US20120325036A1 - Ball Screw and Manufacturing Method of Nut for Ball Screw - Google Patents
Ball Screw and Manufacturing Method of Nut for Ball Screw Download PDFInfo
- Publication number
- US20120325036A1 US20120325036A1 US13/581,210 US201113581210A US2012325036A1 US 20120325036 A1 US20120325036 A1 US 20120325036A1 US 201113581210 A US201113581210 A US 201113581210A US 2012325036 A1 US2012325036 A1 US 2012325036A1
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- US
- United States
- Prior art keywords
- nut
- circumferential surface
- outer circumferential
- ball screw
- ball
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21K—MAKING FORGED OR PRESSED METAL PRODUCTS, e.g. HORSE-SHOES, RIVETS, BOLTS OR WHEELS
- B21K1/00—Making machine elements
- B21K1/64—Making machine elements nuts
- B21K1/70—Making machine elements nuts of special shape, e.g. self-locking nuts, wing nuts
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21J—FORGING; HAMMERING; PRESSING METAL; RIVETING; FORGE FURNACES
- B21J13/00—Details of machines for forging, pressing, or hammering
- B21J13/02—Dies or mountings therefor
- B21J13/025—Dies with parts moving along auxiliary lateral directions
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21J—FORGING; HAMMERING; PRESSING METAL; RIVETING; FORGE FURNACES
- B21J5/00—Methods for forging, hammering, or pressing; Special equipment or accessories therefor
- B21J5/02—Die forging; Trimming by making use of special dies ; Punching during forging
- B21J5/025—Closed die forging
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21J—FORGING; HAMMERING; PRESSING METAL; RIVETING; FORGE FURNACES
- B21J5/00—Methods for forging, hammering, or pressing; Special equipment or accessories therefor
- B21J5/06—Methods for forging, hammering, or pressing; Special equipment or accessories therefor for performing particular operations
- B21J5/12—Forming profiles on internal or external surfaces
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21K—MAKING FORGED OR PRESSED METAL PRODUCTS, e.g. HORSE-SHOES, RIVETS, BOLTS OR WHEELS
- B21K1/00—Making machine elements
- B21K1/04—Making machine elements ball-races or sliding bearing races
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21K—MAKING FORGED OR PRESSED METAL PRODUCTS, e.g. HORSE-SHOES, RIVETS, BOLTS OR WHEELS
- B21K21/00—Making hollow articles not covered by a single preceding sub-group
- B21K21/12—Shaping end portions of hollow articles
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21K—MAKING FORGED OR PRESSED METAL PRODUCTS, e.g. HORSE-SHOES, RIVETS, BOLTS OR WHEELS
- B21K21/00—Making hollow articles not covered by a single preceding sub-group
- B21K21/16—Remodelling hollow bodies with respect to the shape of the cross-section
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21K—MAKING FORGED OR PRESSED METAL PRODUCTS, e.g. HORSE-SHOES, RIVETS, BOLTS OR WHEELS
- B21K23/00—Making other articles
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16H—GEARING
- F16H25/00—Gearings comprising primarily only cams, cam-followers and screw-and-nut mechanisms
- F16H25/18—Gearings comprising primarily only cams, cam-followers and screw-and-nut mechanisms for conveying or interconverting oscillating or reciprocating motions
- F16H25/20—Screw mechanisms
- F16H25/22—Screw mechanisms with balls, rollers, or similar members between the co-operating parts; Elements essential to the use of such members
- F16H25/2204—Screw mechanisms with balls, rollers, or similar members between the co-operating parts; Elements essential to the use of such members with balls
- F16H25/2214—Screw mechanisms with balls, rollers, or similar members between the co-operating parts; Elements essential to the use of such members with balls with elements for guiding the circulating balls
- F16H25/2223—Cross over deflectors between adjacent thread turns, e.g. S-form deflectors connecting neighbouring threads
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16H—GEARING
- F16H25/00—Gearings comprising primarily only cams, cam-followers and screw-and-nut mechanisms
- F16H25/18—Gearings comprising primarily only cams, cam-followers and screw-and-nut mechanisms for conveying or interconverting oscillating or reciprocating motions
- F16H25/20—Screw mechanisms
- F16H25/24—Elements essential to such mechanisms, e.g. screws, nuts
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T74/00—Machine element or mechanism
- Y10T74/19—Gearing
- Y10T74/19642—Directly cooperating gears
- Y10T74/19698—Spiral
- Y10T74/19702—Screw and nut
- Y10T74/19744—Rolling element engaging thread
- Y10T74/19749—Recirculating rolling elements
- Y10T74/19767—Return path geometry
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Transmission Devices (AREA)
- Forging (AREA)
Abstract
A ball screw is provided in which an outer circumferential formation is formed at a portion facing a ball circulating passage out of outer circumferential surface of a nut. The ball screw includes: a screw shaft having on its outer circumferential surface a screw groove; a nut having on its inner circumferential surface a screw groove facing the screw groove; a plurality of balls rollably loaded in a spiral ball rolling passage formed by both screw grooves; and a ball circulating passage to return the balls from a start point to an end point of the ball rolling passage for recirculation. The ball circulating passage is a concaved groove formed by concaving a groove on a part of the cylindrical inner circumferential surface of the nut by plastic working. Then, a flange is integrally provided at a portion facing the ball circulating passage and the screw groove.
Description
- The present invention relates to a ball screw. The present invention relates to a manufacturing method of a nut constituting a ball screw.
- A ball screw includes: a screw shaft having on its outer circumferential surface a spiral screw groove; a nut having on its inner circumferential surface a screw groove facing the screw groove of a screw shaft; and a plurality of balls rollably loaded in a spiral rolling passage formed by the both screw grooves. When the nut screwed via the balls into the screw shaft and the screw shaft is relatively rotate in an axial direction, the screw shaft and the nut relatively move through the rolling of the balls.
- In such a ball screw, there is provided a ball circulating passage constituting an endless ball passage formed by communicating a start point with an end point of the ball rolling passage. That is, when the balls rotate around the screw shaft while moving through within the ball rolling passage and reaches the endpoint of the ball rolling passage, the balls are scooped up from one end of the ball rolling passage, the balls travel through the ball circulating passage and is finally returned back to the start point of the ball rolling passage from the other end of the ball circulating passage. In this way, since the balls rolling through within the ball rolling passage infinitely circulates along the ball circulating passage, the screw shaft and the nut can relatively move continuously.
- A circulating system of the balls employing the ball circulating passage includes various systems, such as a tube system, a deflector system, etc. For example, in case of the tube system, a return tube to communicate a start point with an endpoint of the ball rolling passage is fixed on an outer circumferential surface of the nut. Meanwhile, in case of the deflector system, a deflector in which a groove to communicate a start point with an endpoint of the ball rolling passage is formed is fitted into a deflector hole piercing through an inner circumferential surface and the outer circumferential surface.
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- Patent Document 1: U.S. Pat. No. 7,013,747
- Patent Document 2: JP 2000-297854 A
- Patent Document 3: JP 2008-281063 A
- Patent Document 4: JP 2010-96317 A
- Patent Document 5: JP 2004-251367 A
- However, it is difficult to form outer circumferential formations, such as a flange, etc., at a portion where the ball rolling passage is provided out of the outer circumferential surface of the nut, for the reason that in case of the tube system, the return tube is fixed to the outer circumferential surface of the nut. In case of the deflector system, the deflector hole to fit a deflector is opened to the outer circumferential surface of the nut. In other words, it is difficult to design the outer circumferential surface in arbitrary shape. In addition, it is difficult to freely attach another member to a portion where the ball circulating passage is provided of the outer circumferential surface of the nut. As stated above, in the conventional ball screw, restrictions are imposed on the geometry of an outer diameter portion of the nut.
- To this end, an object of the present invention is to provide a ball screw for solving the above-indentified problems of the prior art, and has a high degree of freedom of the geometry at the outer diameter portion of the nut. Another object of the present invention is to provide a manufacturing method of a ball screw nut to enable manufacturing of a nut constituting such a ball screw.
- To accomplish the above-indicated object, the present invention is configured of the following components. Namely, according to one aspect of the present invention, there is provided a ball screw comprising: a screw shaft having on an outer circumferential surface a spiral screw groove; a nut having on its inner circumferential surface a screw groove facing the screw groove of the screw shaft; a plurality of balls rollably loaded in a spiral ball rolling passage formed by the both screw grooves; and a ball circulating passage to return the balls from an end point to a start point of the ball rolling passage for circulating the balls, wherein the ball circulating passage is formed of a concaved groove formed by concaving a groove on a part of the cylindrical inner circumferential surface of the nut, and an outer circumferential formation is integrally formed on a part facing the concaved groove on the outer circumferential surface of the nut.
- Herein, the outer circumferential formation may be at least one of an encoder, a teeth train for a gear, a rotation stopper, a key, a key seat, a motor rotor, an inner ring of a one-way clutch, a raceway groove for a bearing, a screw, a circumferential groove, and another shape of the outer circumferential surface.
- Additionally, the nut may be produced by machining a cylindrical metal blank to produce a roughly formed nut having a substantially identical shape with the nut, concaving a groove on the part of the cylindrical inner circumferential surface of the roughly formed nut, forming the concaved groove constituting the ball circulating passage, and forming the outer circumferential formation on the outer circumferential surface of the roughly formed nut.
- Alternatively, the nut may be produced by machining a cylindrical metal blank to produce a roughly formed nut having a substantially identical shape with the nut, by concaving a groove a part of the cylindrical inner circumferential surface of the roughly formed nut by plastic working, forming the concaved groove constituting the ball circulating passage, and forming the outer circumferential formation on the outer circumferential surface of the roughly formed nut.
- In addition, in the ball screw according to the aforesaid one embodiment of the present invention, preferably, the screw groove of the nut is provided only at a part where the balls rotate on the inner circumferential surface of the nut, and is not provided at a part where the balls do not rotate.
- Furthermore, according to said one aspect of the present invention, a protrusion may be provided integrally with the nut on an end face in an axial direction of the nut. This protrusion may be provided at a part in the circumferential direction of the end face in an axial direction of the nut.
- Moreover, according to another aspect of the present invention, there is provided a ball screw comprising: a screw shaft having on an outer circumferential surface a spiral screw groove; a nut having on its inner circumferential surface a screw groove facing the screw groove of the screw shaft; a plurality of balls rollably loaded in a spiral ball rolling passage formed by the both screw grooves; and a ball circulating passage to return the balls from an end point to a start point of the ball rolling passage for circulating the balls, wherein the ball circulating passage is formed of a concaved groove formed by concaving a groove on a part of the cylindrical inner circumferential surface of the nut, and an outer circumferential formation is integrally formed on a part facing the concaved groove on the outer circumferential surface of the nut, wherein the concaved groove is formed on the inner circumferential surface of the nut blank by pressing the inner circumferential surface of the nut blank with a convex, by a press method using a die of the cam mechanism, the cam mechanism comprising: a cam driver internally inserted into a nut blank and moving in an axial direction; a cam slider disposed between the nut blank and the cam driver, and having the convex corresponding to the concaved groove, the convex moving in a radial direction of the nut with a movement of the cam driver.
- Moreover, according to said one aspect or another aspect of the present invention, the ball screw may further comprise a nut fitted member to be fitted by press fitting onto the outer circumferential surface of the nut.
- In this situation, preferably, an interference of the nut fitted member and the nut by press fitting exceeds 0.02 percent of an external dimension of the outer circumferential surface of the nut onto which the nut fitted member is fitted. Alternatively, preferably, an interference of the nut fitted member and the nut by press fitting exceeds 0.02 percent and less than 0.16 percent of an external dimension of the outer circumferential surface of the nut onto which the nut fitted member is fitted.
- Additionally, preferably, when the nut fitted member is press fitted into the nut, shrink fitting is used which heats the nut fitted member to fit onto the nut.
- Furthermore, preferably, the nut fitted member is any of a sleeve a bearing, a gear, each having a cylindrical inner circumferential surface, and a combination thereof.
- Moreover, according to said one aspect of the present invention, the ball screw may further comprise a nut fitted member provided by insert molding on the outer circumferential surface of the nut.
- Additionally, according to another aspect of the present invention, there is provided a manufacturing method of ball screw nut comprising: a nut having on an inner circumferential surface a spiral groove and on an outer circumferential surface a protrusion; a screw shaft having on an outer circumferential surface a spiral groove; a plurality of balls rollably loaded between a raceway formed by the both screw grooves; and a ball returning passage formed as a concave on an inner circumferential surface of the nut, to return the balls from an end point to a start point of the raceway, the plurality of balls rolling in the raceway to cause the nut to relatively move with respect to the screw shaft, wherein formation of the concave on the inner circumferential surface of the nut, and formation of the protrusion on the outer circumferential surface of the nut are simultaneously performed by cold forging.
- Furthermore, according to said another aspect of the present invention, the concaved groove may be formed on the inner circumferential surface of the nut blank by pressing the inner circumferential surface of the nut blank with a convex, by a press method using a die of the cam mechanism, the cam mechanism comprising: a cam driver internally inserted into a cylindrical nut blank and moving in an axial direction; a cam slider disposed between the nut blank and the cam driver, and having the convex corresponding to the concaved groove, the convex moving in a radial direction of the nut with a movement of the cam driver; and a restraining member for restraining both end faces in the axial direction and the outer circumferential surface of the nut blank, and having a recess on an inner circumferential surface that receives the outer circumferential surface of the nut blank, wherein the outer circumferential formation is formed by projecting a periphery of the nut blank into the recess of the restraining member.
- In this situation, a working in a subsequent process may be performed after a process in the press method using the die, by using the outer circumferential formation, a recess or a tapered surface formed on the inner circumferential surface of the outer circumferential formation, as a reference surface or a holding part.
- In addition, the outer circumferential formation may be a torque transmission part, a positing part, or a mounting part.
- Furthermore, according to further another aspect of the present invention, there is provided a ball screw comprising: a screw shaft having on an outer circumferential surface a spiral screw groove; a nut having on an inner circumferential surface a screw groove facing the screw groove of the screw shaft; a plurality of balls rollably loaded in a spiral ball rolling passage formed by the both screw grooves; and a ball circulating passage to return the ball from an end point to a start point of the ball rolling passage for circulating the balls, wherein the ball circulating passage is formed of a concaved groove on a part of the cylindrical inner circumferential surface of the nut, and a protrusion is provided on an end face in an axial direction of the nut.
- In this situation, the concaved groove may be formed on the inner circumferential surface of the nut blank by pressing the inner circumferential surface of the nut blank with a convex, by a press method using a die of a cam mechanism, the cam mechanism comprising: a cam driver internally inserted into a cylindrical nut blank and moving in an axial direction; a cam slider disposed between the nut blank and the cam driver, and having the convex corresponding to the concaved groove, the convex moving in a radial direction of the nut with a movement of the cam driver; and a restraining member for restraining both end faces in the axial direction and the outer circumferential surface of the nut blank, and having a recess on an end face to receive the both end faces in the axial direction of the nut blank, wherein the protrusion is formed by projecting an excess material, produced with the formation of the concaved groove, of the nut blank into a recess of the restraining member.
- Additionally, preferably, a nut fitted member is provided by insert molding on the outer circumferential surface of the nut, the nut fitted member being formed to cover the outer circumferential formation on the outer circumferential surface of the nut produced with the formation of the concaved groove.
- Preferably, the nut fitted member formed by insert molding may be either of or both of the sleeve or a gear having a cylindrical inner circumferential surface.
- Since in the ball screw of the present invention, the ball circulating passage is configured with the concaved groove formed by concaving a groove on a part of the inner circumferential surface of the nut, the present invention provides a high degree of freedom of the geometry of the outer diameter portion of the nut. Further, the production method of the ball screw nut of the present invention allows manufacturing of the ball screw nut with a high degree of freedom of the geometry of the outer diameter portion of the nut.
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FIG. 1 is a cross-sectional view of a ball screw according to a first embodiment of the present invention; -
FIG. 2 is a front view of a nut; -
FIG. 3 is a cross-sectional view taken along a line A-A of the nut shown inFIG. 2 ; -
FIG. 4 shows a first example of a second embodiment of a ball screw according to the present invention, in whichFIG. 4A is a front view, andFIG. 4B is a longitudinal sectional view; -
FIG. 5 shows only a ball screw nut shown inFIG. 4 , in whichFIG. 5A is a right side view, andFIG. 5B a longitudinal sectional view; -
FIG. 6 is a process drawing of manufacturing method of the nut shown inFIG. 5 ; -
FIG. 7 shows only a nut of a second example of a second embodiment of the ball screw of the present invention, in whichFIG. 7A is a front view, andFIG. 7B is a longitudinal sectional view; -
FIG. 8 shows only a nut of a third example of the second embodiment of the ball screw of the present invention, in whichFIG. 8A is a front view, andFIG. 8B is a longitudinal sectional view; -
FIG. 9 shows only a nut of a fourth example of the second embodiment of the ball screw of the present invention, in whichFIG. 9A is a front view, andFIG. 9B is a longitudinal sectional view; -
FIG. 10 shows only a nut of a fifth example of the second embodiment of the ball screw of the present invention, in whichFIG. 10A is a front view, andFIG. 10B is a longitudinal sectional view; -
FIG. 11 shows only a nut of a sixth example of the second embodiment of the ball screw of the present invention, in whichFIG. 11A is a front view, andFIG. 11B is a longitudinal sectional view; -
FIG. 12 shows only a nut of a seventh example of the second embodiment of the ball screw of the present invention, in whichFIG. 12A is a front view, andFIG. 12B is a longitudinal sectional view; -
FIG. 13 shows only a nut of an eighth example of the second embodiment of the ball screw of the present invention, in whichFIG. 13A is a transverse longitudinal sectional view, andFIG. 13B is an orthogonal longitudinal sectional view; -
FIG. 14 shows a modification of the ball screw shown inFIG. 13 , in whichFIG. 14A a transverse longitudinal sectional view, andFIG. 14B is an orthogonal longitudinal sectional view; -
FIG. 15 a process drawing explaining a manufacturing method of a ball screw of a third embodiment; -
FIG. 16 is a view explaining a method of a first example of a fourth embodiment; -
FIG. 17 is a view showing a cam slider used in the first example of a fourth embodiment, in whichFIG. 17A is a plain view,FIG. 17B is a perspective view, andFIG. 17C is a perspective view showing the cam slider; -
FIG. 18 is a perspective view showing a nut blank removed from a die in a state shown inFIG. 16B ; -
FIG. 19 is a view explaining the second example of the fourth embodiment; -
FIG. 20 is a view showing a cam slider used in the second example of the fourth embodiment, in whichFIG. 20A is a plane view,FIG. 20B is a perspective view, andFIG. 20C is a perspective view showing the cam driver; -
FIG. 21 is a perspective view showing a nut blank removed from a die in a state shown inFIG. 19B ; -
FIG. 22 is a view explaining a method of a third example of the fourth embodiment; -
FIG. 23 is a view showing a cam slider used in the third example of the fourth embodiment, in whichFIG. 23A is a plane view,FIG. 23B is a perspective view, andFIG. 23C is a perspective view showing the cam driver; -
FIG. 24 is a perspective view showing a nut blank removed from a die in a state shown inFIG. 22B ; -
FIG. 25 is a view explaining a method of the fourth example of the fourth embodiment; -
FIG. 26 is a perspective view showing a nut blank removed from a die in a state shown inFIG. 26B ; -
FIG. 27 is a view explaining a method of a fifth example of the fourth embodiment; -
FIG. 28 is a view explaining a method ofpatent document 3; -
FIG. 29 is a cross-sectional view showing a construction in a first example of a manufacturing method of a fifth embodiment; -
FIG. 30 is a view showing a cam driver used in the first example of the fifth embodiment, in whichFIG. 30A is a perspective view,FIG. 30B is a plane view showing a cam slider, andFIG. 30C is a perspective view; -
FIG. 31 is a view showing a split constituting a restraining member used in the first example of the fifth embodiment, in whichFIG. 31A is a plane view,FIG. 31B is a sectional view taken along a line A-A thereof, andFIG. 31C is a cross-sectional view of a stand; -
FIG. 32 is a view showing a nut blank in which an S-shaped groove and a convex are formed in the first example of the fifth embodiment, in whichFIG. 32A is a front view, andFIG. 32B is a cross-sectional view taken along a line A-A thereof, andFIG. 32C is a perspective view; -
FIG. 33 is a cross-sectional view showing a construction in the second example of manufacturing method of the fifth embodiment; -
FIG. 34 is a cross-sectional view showing a construction in the third embodiment of manufacturing method of the fifth embodiment; -
FIG. 35 is a cross-sectional view showing a construction in the fourth embodiment of manufacturing method of the fifth embodiment; -
FIG. 36 is a view explaining a method of the fifth example of manufacturing method of the fifth embodiment; -
FIG. 37 is a view explaining a method of the fifth example of manufacturing method of the fifth embodiment; -
FIG. 38 is a view showing a construction of one example of the ball screw of the fifth embodiment, in whichFIG. 38A is a cross-sectional view, andFIG. 38B is a perspective view; -
FIG. 39 is a perspective view showing a construction of another example of the ball screw of the fifth embodiment; -
FIG. 40 is a longitudinal sectional view showing a first example of the ball screw of a sixth embodiment; -
FIG. 41 is a longitudinal sectional view showing a second example of the ball screw of the sixth embodiment; -
FIG. 42 is a longitudinal sectional view showing a third example of the ball screw of the sixth embodiment; -
FIG. 43 is a longitudinal sectional view showing a fourth example of the ball screw of the sixth embodiment; -
FIG. 44 is a longitudinal sectional view showing a fifth example of the ball screw of the sixth embodiment; -
FIG. 45 is a longitudinal sectional view showing a sixth example of the ball screw of the sixth embodiment; -
FIG. 46 is a longitudinal sectional view showing a first example of the ball screw of a seventh embodiment; -
FIG. 47 is a longitudinal sectional view showing a second example of the ball screw of the seventh embodiment; -
FIG. 48 is an explanation view of a ball screw nut used in the ball screw shown inFIG. 47 ; -
FIG. 49 is a longitudinal sectional view showing a third example of the ball screw of the seventh embodiment; -
FIG. 50 is a longitudinal sectional view showing a fourth example of the ball screw of a seventh embodiment; -
FIG. 51 is a longitudinal sectional view showing a fifth example of a ball screw of the seventh embodiment; and -
FIG. 52 is a partial sectional view of a steering gear of an electric steering device. - Hereinafter, a description will be made to embodiments of the present invention with reference to the accompanying drawings.
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FIG. 1 is a cross-sectional view (a cross-sectional view taken with a plane in an axial direction) of a ball screw of a first embodiment according to the present invention. As shown inFIG. 1 , theball screw 1 includes: ascrew shaft 3 having on its outer circumferential surface aspiral screw groove 3 a; anut 5 having on its inner circumferential surface aspiral screw groove 5 a facing thescrew groove 3 a of thescrew shaft 3; a plurality ofballs 9 rollably loaded in a spiralball rolling passage 7 formed by the bothscrew grooves ball circulating passage 11 to return theballs 9 from an endpoint to a start point of theball rolling passage 7 for circulating theballs 9. - Namely, the
balls 9 circulates around thescrew shaft 3 while traveling within theball rolling passage 7 and reaches an endpoint of theball rolling passage 7, where theballs 9 are scooped up from one end of theball circulating passage 11 and returns to the start point of theball rolling passage 7 from the other end of theball circulating passage 11 through within theball circulating passage 11. - It is noted that materials for the
screw shaft 3, thenut 5, and theball 9 are not specifically limited to particular ones, and any general materials may be available. For example, metal such as steel, etc., and ceramic may be given as a candidate. Additionally, a cross-sectional shape of thescrew grooves - Such a
ball screw 1 is arranged such that when thenut 5 screwed via theball 9 with thescrew shaft 3 and thescrew shaft 3 are relatively rotated, thescrew shaft 3 and thenut 5 relatively move through the rolling of theball 9 in an axial direction. An endless ball passage is formed by theball rolling passage 7 and theball circulating passage 11. Theball 9 rolling within theball rolling passage 7 endlessly circulates within the endless ball passage, and therefore thescrew shaft 3 and thenut 5 are allowed to relatively move continuously. - An explanation will be made here to the
ball circulating passage 11 in further details. Theball circulating passage 11 is integrally formed on an inner circumferential surface of thenut 5. More specifically, a concaved groove formed concaving a groove on a part of the cylindrical inner circumferential surface of thenut 5 by plastic working or by cutting is taken as theball circulating passage 11. Since theball screw 1 of the present embodiment adopts a ball circulating system utilizing such aball circulating passage 11, it eliminates the necessity for mounting another member constituting theball circulating passage 11 on thenut 5. In this connection, a cross-sectional shape of theball circulating passage 11 may be an arc or a gothic arc. - In case where the ball circulating system is a tube system or a deflector system, a member constituting the ball circulating passage and the nut are formed as a separate body. In case of the tube system, the return tube is provided on the outer circumferential surface, whereas in case of the deflector system, a deflector is attached in a deflector hole. Therefore, it is impossible to provide an outer circumferential formation such as a flange, etc., at a portion where the return tube and the deflector are provided, on the outer circumferential surfaces. Thus, a restriction is imposed on the freedom to design the outer circumferential surface of the nut.
- In contrast, in the
ball screw 1 of the present embodiment, theball circulating passage 11 is provided on the inner circumferential surface of thenut 5, which eliminates the need for providing any kind of member for circulation of the balls on the outer circumferential surface of thenut 5. This gives freedom to design all over the outer circumferential surface of thenut 5 in arbitrary shape, without being restricted by a position where theball circulating passage 11 is provided and the number of circuits. Thus, the embodiment enables integrally forming the outer circumferential formation even at a position facing theball circulating passage 11 and thescrew groove 5 a, on the outer circumferential surfaces of thenut 5. Theball screw 1 of the present embodiment is provided with aflange 13 as the outer circumferential formation. Further, since theball screw 1 does not include members such as the return tube, the deflector, etc., it is free from care about perchance being fallen out, thus providing thereliable ball screw 1. - The kind of the outer circumferential formation is not specifically limited to a particular one. In addition to the flange, a teeth train for a gear, a key seat, a baring raceway groove, and another shape of outer circumferential surface may be used. For example, provided that the teeth train for a gear is arranged in a circumferential direction and consists of a plurality of teeth on the outer circumferential surface of the
nut 5, it enables thenut 5 to function as a gear. Moreover, given that a key seat is formed on the outer circumferential surface of thenut 5, thenut 5 can be connected with another member by engaging a key provided in another member into the key seat. Further, provided that a bearing raceway groove is formed on the outer circumferential surface of thenut 5, it enables thenut 5 to function as an inner ring of the rolling bearing. Furthermore, whereas the outer circumferential surface of thenut 5 typically has a circular cross section, not limited thereto, another shape of outer circumferential surfaces, such as a polygonal cross section and an elliptical cross section may also be permitted. Incidentally, one of these outer circumferential formations may be provided on the outer circumferential surfaces of thenut 5, or two or more may be provided. For instance, as in theball screw 1 of the present embodiment, aflange 13 is provided on the outer circumferential surface of thenut 5, and ateeth train 15 for a gear on the outer circumferential surface of theflange 13. - A forming method of these outer circumferential formations is not specifically limited to a particular one, and it may be formed by forging such as cold forging, or by cutting. With these forming methods, low-cost manufacturing of the ball screw with the outer circumferential formation is made possible as the formation can be easily formed. Also, in what order the outer circumferential formation and the
ball circulating passage 11 should be provided is not specifically limited to a particular one, rather it does not matter which of them is provided first. Nonetheless, if theball circulating passage 11 is formed after the outer circumferential formation is provided by e.g. cold forging, it ensures high shaping accuracy of theball circulating passage 11. - Whereas application of such a
ball screw 1 of the preset embodiment is not specifically limited to a particular one, it is preferably applied, inter alia, to an electric actuator to be incorporated into a car, a motorcycle, a positioning device, etc. - Herein, one example of manufacturing method of the
nut 5 of theball screw 1 of the present embodiment will be briefly explained by referring toFIG. 6 . Firstly, a cylindrical steel material (not shown) is worked by cold forging to form a virtually cylindrical blank (having a shape substantially identical with the nut 5). Secondly, a concaved groove is formed on an outer circumferential surface of the blank by plastic working such as forging, etc., to provide theball circulating passage 11. Then, ateeth train 15 for a gear that consists of a plurality of teeth arranged in a circumferential direction is provided on the outer circumferential surface of theflange 13 projecting from the outer circumferential surface of the blank. Finally, when thescrew groove 5 a is formed on the inner circumferential surface of the blank, thenut 5 is provided. - In the ball screw, there are a variety of circulating systems of the balls using the ball circulating passages, including a tube system and a deflector system. For example, in case of the tube system, a return tube for communicating a start point with an end point of the ball rolling passage is secured on the outer circumferential surface of the
nut 5. Meanwhile, in case of the deflector system, a deflector in which a groove for communicating a start point with an end point of the ball rolling passage is formed is fitted into a deflector hole piercing through the outer circumferential surface and the inner circumferential surface of the nut. In addition, it is also known a circulating system in which a concaved groove is formed by concaving a groove on a part of the inner circumferential surface of the nut, so that the concaved groove is adopted as the ball circulating passage. - In manufacturing such a ball screw, the nut is manufactured by working a cylindrical steel material by cold forgoing to produce a substantially cylindrical blank (having a shape substantially the same as that of the nut), and by applying cutting to the blank. More specifically, the formation of a through hole into which the return tube is inserted and the deflector hole, the formation of the concaved groove, and the formation of the outer circumferential formation, such as the teeth train for a gear, on the outer circumferential surface are achieved by cutting. Further, Patent Document 2 proposes a technique of manufacturing a nut having a desired geometry with sintered alloy.
- However, manufacturing of the nut by cutting inherently entails a problem of undergoing poor material yield and high cost. What is more, since sintered alloy has low density and contains void, the sintered alloy inherently involves a problem that it is difficult to have the sufficient strength as a nut.
- The second embodiment is devised for aiming at the above-identified problems, and its object is to provide a manufacturing method of a ball screw and a ball screw, with which manufacturing of a ball screw is enabled at a low-cost and with a high strength, in addition to a high material yield.
- To solve the above problems, a manufacturing method of the second embodiment comprises: a screw shaft having on its outer circumferential surface a spiral screw groove; a nut having on its inner circumferential surface a screw groove facing the screw groove of the screw shaft; and a plurality of balls rollably loaded in a spiral ball rolling passage formed by the both screw grooves; a ball circulating passage to return the ball from an end point to a start point of the ball rolling passage for circulating the balls; and an outer circumferential formation integrally formed on the outer circumferential surface of the nut, the method comprising a roughly forming step of producing a roughly formed nut having a shape substantially identical with the nut from a cylindrical metal material; a ball circulating passage forming step of forming a concaved groove constituting the ball circulating passage by concaving a groove on a part of a circular cylindrical surface (cylindrical surface) inner circumferential surface of the roughly formed nut; and an outer circumferential formation forming step of forming the outer circumferential formation on the outer circumferential surface of the roughly plastic nut, wherein the outer circumferential formation is at least one of a key, an encoder, a gear, a rotation stopper, a screw, a circumferential groove, a motor rotor, and an inner ring of a one-way clutch.
- At least one of the roughly forming step, the ball circulating passage forming step, and the outer circumferential formation forming step is worked by plastic working.
- Further, the plastic working is cold forging.
- The ball screw of the second embodiment comprises: a screw shaft having on its outer circumferential surface a spiral screw groove; a nut having on its inner circumferential surface a screw groove facing the screw groove of the screw shaft; a plurality of balls rollably loaded in a spiral ball rolling passage formed by the both screw grooves, and a ball circulating passage to return the balls from an end point to a start point of the ball rolling passage for circulating the balls, wherein the ball circulating passage is formed of a concaved groove formed by concaving a groove on a part of the cylindrical inner circumferential surface of the nut, and a outer circumferential formation is integrally formed on the outer circumferential surface of the nut, and wherein the outer circumferential formation is at least one of a key, an encoder, a gear, a rotation stopper, a screw, a circumferential groove, a motor rotor, and an inner ring of a one-way clutch.
- According to the manufacturing method of the ball screw and the nut of the second embodiment, the embodiment allows manufacturing the ball screw with a high strength at a low cost, in addition to a high material yield.
- An explanation will next be made to the ball screw of the second embodiment by referring to the drawings.
FIG. 4 is a view showing one example of the ball screw of the second embodiment, in whichFIG. 4A is a front view, andFIG. 4B is a longitudinal sectional view (a longitudinal sectional view parallel to an axis line, hereinafter referred also to as a transversal longitudinal sectional view).FIG. 5 is a view only showing the details of the nut of the ball screw shown inFIG. 4 , in whichFIG. 5A is a right side view, andFIG. 5B is a transversal longitudinal sectional view. - As shown in
FIG. 5 , theball screw 1 includes: ascrew shaft 3 having on its outer circumferential surface aspiral screw groove 3 a; anut 5 having on its inner circumferential surface aspiral screw groove 5 a facing thescrew groove 3 a of thescrew shaft 3; a plurality ofballs 9 rollably loaded in a spiralball rolling passage 7 formed by bothscrew grooves ball circulating passage 11 to return theballs 9 from an endpoint to a start point of theball rolling passage 7 for circulating the balls. - In other words, the
balls 9 rotate around ascrew shaft 3 while traveling through theball rolling passage 7, and reach an end point of theball rolling passage 7 where theballs 9 are scooped up from one end of theball circulating passage 11 and are returned to the start point of theball rolling passage 7 through theball circulating passage 11. - It is noted that what materials should be used for the
screw shaft 3, thenut 5, and theballs 9 are not specifically restrained to particular ones, rather it may be available general materials, including e.g. metal such as steel, etc., and ceramic. Further, a cross-sectional shape of thescrew grooves - Such a
ball screw 1 is configured such that when thenut 5 screwed with thescrew shaft 3 via theballs 9 and thescrew shaft 3 are relatively rotated, they relatively move in an axial direction with the rolling of theballs 9. The endless ball passage is formed of theball rolling passage 7 and theball circulating passage 11. As theballs 9 rolling through theball rolling passage 7 endlessly circulate through the endless ball passage, thescrew shaft 3 and thenut 5 are permitted to relatively move continuously. - An explanation will be made here in detail to the
ball circulating passage 11. The circulatingpassage 11 is integrally formed on the inner circumferential surface of thenut 5. More particularly, a concaved groove formed by concaving a groove on a part of the inner circumferential surface of thenut 5 e.g. by plastic working is taken as theball circulating passage 11. It is noted that a cross-sectional shape of theball circulating passage 11 may be an arc or the previously described gothic arc. Since theball screw 1 of the present embodiment adopts a ball circulating system using such aball circulating passage 11, the embodiment eliminates the need for providing a member, such as the return tube and the deflector on thenut 5 constituting the ball circulating passage. Also, the embodiment eliminates the necessity for providing a through hole and a deflector hole to mount another member, such as the return tube and the deflector constituting the ball circulating passage. - Where the ball circulating system is the tube system and the deflector system, the member constituting the ball circulating passage and the nut are separate bodies. In case of the tube system, the return tube is provided on the outer circumferential surface of the nut, whereas in case of the deflector system, the deflector is fitted into the deflector hole. For that reason, the outer circumferential formation such as the flange cannot be arranged on a portion where the return tube and the deflector are provided, on the outer circumferential surfaces of the nut, resulting in a restriction on freedom of design of the outer circumferential surface of the nut.
- In contrast, according to the
ball screw 1 of the present embodiment, since theball circulating passage 11 is provided on the inner circumferential surface of the nut, the embodiment eliminates the need for providing any member to circulate the ball on the outer circumferential surface of thenut 5. Additionally, since the embodiment eliminates the necessity for forming any hole to attach a member for circulating the ball, thenut 5 is not subject to a restriction of a position where theball circulating passage 11 is provided or the number thereof. This may give a high degree of freedom to design the outer circumferential surface in arbitrary shape on all over the outer circumferential surface of thenut 5. Accordingly, the embodiment enables the integral formation of the outer circumferential formation on the outer circumferential surface of thenut 5, even at a portion facing theball circulating passage 11 and thescrew groove 5 a, on the outer circumferential surfaces of thenut 5. Further, since members such as the return tube, the deflector, etc. are not provided, it is free from care of these members being fallen out, which offers theball screw 1 with high reliability. Furthermore, no particular restriction is not imposed on the kind of the outer circumferential formation of thenut 5, rather in addition to the flange, a teeth train for gear (helical gear), an encoder, a key, a bevel gear, a rotation stopper, a screw (male screw), a circumferential groove, a motor rotor, and an inner ring of a one-way clutch may be available. For example, integrally providing the flange on the outer circumferential surface of thenut 5, and forming the teeth train for a gear (helical gear consisting of plural circumferentially arranged teeth on the outer circumferential surface of the flange allows thenut 5 to function as a gear. - Moreover, integrally providing the encoder on the outer circumferential surface of the
nut 5 enables direct detection of a rotational state of thenut 5. Additionally, integrally providing a key on the outer circumferential surface of thenut 5 connects thenut 5 with another member, by engaging thenut 5 into a key seat formed in the another member. Further, integrally providing a bevel gear on the outer circumferential surface of thenut 5 enables a power transmission with the bevel gear to be meshed. - With the provision of a detent on the outer circumferential surface of the
nut 5, mere locking of the rotation stopper attains a translatory movement of thescrew shaft 3, when thenut 5 and thescrew shaft 3 are relatively rotated. Further, integrally providing a screw (male screw) on the outer circumferential surface of thenut 5 allows a screw motion between screws to be screwed together therewith. In addition to this, integrally providing a circumferential groove on the outer circumferential surface of thenut 5 achieves a bearing capability on the outer circumferential surface of thenut 5 by, for example, attaching a wear ring into the circumferential groove. - Moreover, integrally providing the rotor motor on the outer circumferential surface of the
nut 5 enables thenut 5 per se to function as a rotor motor. By installing it within a motor stator, a turning force to be imparted to thenut 5 may easily or directly be obtained. Additionally, integrally providing an inner ring of a one-way clutch on the outer circumferential surface of thenut 5 restricts the rotation to either thenut 5 or the outer ring of the one-way clutch. - Specifically, one of these outer circumferential formations may be formed on the outer circumferential surface of the
nut 5, or two or more may be formed thereon. For example, in theball screw 1 of the present embodiment, theflange 13 is provided on the outer circumferential surface of thenut 5, the teeth train 15 for a gear is provided on the outer circumferential surface of theflange 13, and an encoder (rotary encoder) 17 is integrally provided on a left side in an illustrated axial direction of theflange 13. Thereby, thenut 5 of theball screw 1 of the present embodiment may function as a gear, and its rotational state can be detected by theencoder 17. While an application of theball screw 1 of the present embodiment is not specifically limited to a particular one, it may preferably be applied to an electric actuator to be built in a car, a motorcycle, a positioning device, etc. - An explanation of one example will next be made to a manufacturing method of the
ball screw 1 of the present embodiment by referring toFIG. 6 . In the present embodiment, acylindrical steel material 20 having the predetermined length (or mass) is machined by plastic working e.g. by cold forging, etc., to produce a blank 21 (roughly formed nut) having a shape (substantially cylindrical shape) virtually identical with the nut 5 (roughly forming process). At this time, the flange 12 is also provided on the outer circumferential surface of the blank 21 by plastic working. Therefore, the roughly forming process also serves as an outer circumferential forming process. - A concaved groove is then formed by concaving a groove on a part of the cylinder-shaped inner circumferential surface of the blank 21 by e.g. plastic working such as cold forging to form a
concaved groove 22 constituting theball circulating passage 11 communicating a start point with an end point of the ball rolling passage 7 (ball circulating passage forming process). A specific method of forming theconcaved groove 22 includes one as below. That is, inserting a punch with a convex having a shape corresponding to theconcaved groove 22; bringing the convex of the punch into contact with the inner circumferential surface of the blank 21; and strongly pressing the punch against the inner circumferential surface of the blank to form theconcaved groove 22. - It is noted that in what order the outer circumferential formation and the
ball circulating passage 11 should be provided is not specifically limited to a particular one, which of them is provided first is not a matter. However, in the present embodiment, since theball circulating passage 11 is formed after theflange 13 that is the outer circumferential formation is formed by plastic working, a higher shape accuracy of theball circulating passage 11 can be secured. - The teeth train 15 for a gear, consisting of a plurality of circumferentially arranged teeth is provided on the outer circumferential surface of the
flange 13 projecting from the outer circumferential surface of the blank 21, e.g. by plastic working such as cold forging, and theencoder 17 is provided directly on the outer circumferential surface of thenut 5, e.g. by plastic working such as cold forging. It is noted that the plastic working is preferable for these formations, but they may be formed by cutting. - Then, a
screw groove 5 a is formed on the inner circumferential surface of the blank 21 by cutting (screw groove forming process). Finally, thenut 5 is manufactured by applying heat treatment, such as hardening and tempering, thereto under a desired condition. An example of hear treatment includes carburizing, carbonitriding, induction heat treatment, etc. - The
ball screw 1 of the present embodiment is manufactured by combining thenut 5 thus manufactured in this way with thescrew shaft 3 and theballs 9 manufactured in the traditional method. In the present embodiment, since all the aforementioned roughly forming process, the ball circulating passage forming process, and the outer circumferential formation forming process are performed by plastic working, the manufacturing method of theball screw 1 achieves manufacturing of the high precision of theball screw 1 at a low cost, in addition to a high material yield. Further, since manufacturing is done by plastic working, a metal flow (fiber flow) of thesteel material 20 is hardly cut and subject to work hardening, whereby ahigh strength nut 5 may be manufactured. - The kind of the plastic working is not specifically limited to a particular one, but forging is preferable, and cold forging is more preferable. Instead, adopting hot forging is also possible, but since the cold forging provides highly accurate finishing as compared with the hot forging, it may provide the
nut 5 with satisfactory high precision, without applying a post process. As a result, theball screw 1 can be manufactured at a low cost. - It is preferable to adopt the plastic working as the cold forging in all the manufacturing processes, out of the roughly forming process, the ball circulating passage forming process, and the outer circumferential formation forming process, but it may substitute the plastic working for the cold forging in either one or in two processes. In this occasion, as a working method other than the plastic working such as the cold forging, it is also possible to use cutting, such as turning working and grinding, electrical discharge working or combination of them, or a combination of them and shot blasting.
- Additionally, in the ball circulating passage forming process, a working process may be divided into two or more processes as with the rough processing and finishing. In that case, for example, a rough shape may previously be formed on a lathe as rough processing, and then perform finishing working by grinding, polishing, or banish working.
- An explanation will next be made to a second example of the ball screw of the second embodiment by referring to
FIG. 7 .FIG. 7 is a view showing only the nut of the ball screw manufactured by the same manufacturing process as the first example of the second embodiment shown inFIGS. 4 to 6 , in whichFIG. 7A is a front view, andFIG. 7B is a transversal longitudinal cross-sectional view. The screw shaft and the ball of the ball screw of the present embodiment are the same as those of the first example of the second embodiment shown inFIG. 4 . Further, the circulatingpassage 11 and thescrew groove 5 a formed in thenut 5 are functionally equal thereto, though their shapes are slightly different, and so its detailed description is omitted for brevity's sake. - In the present embodiment, a key 31 is integrally provided on the outer circumferential surface of the
nut 5 e.g. by plastic working in the outer circumferential formation forming process shown inFIG. 6 . The key 31 plays a role of connecting another member (not shown) to thenut 5 by engaging into a key seat of another part. The key 31 may be manufactured by cutting or by grinding. Alternatively, a key seat may be formed in place of the key 31. - An explanation will next be made to a third example of the ball screw of the second embodiment by referring to
FIG. 8 .FIG. 8 is a view showing only the nut out of the ball screw manufactured by the same manufacturing process as that of the first example of the second embodiment shown inFIGS. 4 to 6 , in whichFIG. 8A is a front view, andFIG. 8B is a transversal longitudinal sectional view. The screw shaft and the ball of the ball screw of the present embodiment are the same as those of the first example of the second embodiment shown inFIG. 4 . Further, the circulatingpassage 11 and thescrew groove 5 a formed in thenut 5 are functionally equal thereto, though their shapes are slightly different, and so its detailed description is omitted for brevity's sake. - In the present embodiment, a
bevel gear 33 is integrally provided on the outer circumferential surface of thenut 5 e.g. by plastic working in the outer circumferential forming process shown inFIG. 6 . Thebevel gear 33 may play a part in power transmission in a direction perpendicular to the axis with a bevel gear to be meshed therewith. Thebevel gear 33 may be provided by cutting and grinding. - An explanation will next be made to a fourth example of the ball screw of the second embodiment by referring to
FIG. 9 .FIG. 9 is a view showing only the nut in the ball screw manufactured by the same manufacturing process as that of the first example of the second embodiment shown inFIGS. 4 to 6 , in whichFIG. 9A is a front view, andFIG. 9B is a transversal longitudinal sectional view. The screw shaft and the balls of the ball screw according to the present embodiment are same with those of the first example in the second embodiment illustrated inFIG. 4 . Further, the circulatingpassage 11 and thescrew groove 5 a formed in thenut 5 as a function of the ball screw are functionally equal thereto, though their shapes are slightly different, and so its detailed description is omitted for brevity's sake. - In the present embodiment, a
cubic rotation stopper 35 is integrally provided on the outer circumferential surface of thenut 5 in the outer circumferential formation forming process shown inFIG. 6 . Therotation stopper 35 is abut by another member (not shown) to thereby restrict rotation of thenut 5, thus accomplishing a translatory movement in an axial direction of the screw shaft, for example, when thenut 5 and the screw shaft are relatively rotated. Suppose that therotation stopper 35 is arranged on the outside in a radial direction of theball circulating passage 11. When a concaved groove for theball circulating passage 11 is formed with the punch as described above, a concave is previously formed at a dice side. This automatically provides therotation stopper 35 using a material to expand to the outside in a radial direction of thenut 5. - An explanation will next be made to a fifth example of the ball screw of the second embodiment by referring to
FIG. 10 .FIG. 10 is a view showing only the nut out of the ball screw manufactured by the same manufacturing process as that of the first example of the second embodiment shown in FIGS. 4 to 6, in whichFIG. 10A is a front view, andFIG. 10B is a transversal longitudinal sectional view. The screw shaft and the balls of the ball screw according to the present embodiment are same with those of the first example in the second embodiment illustrated inFIG. 4 . Further, the circulatingpassage 11 and thescrew groove 5 a formed in thenut 5 are functionally equal thereto, though their shapes are slightly different, and so its detailed description is omitted for brevity's sake. - In the present embodiment, a screw (male screw) 37 is integrally provided on the outer circumferential surface of the
nut 5 in the outer circumferential formation forming process shown inFIG. 6 . Themale screw 37 is screwed into a screw (e.g. female screw) of another member (not shown) to thereby accomplishing a screw motion. Instead, thescrew 37 may be formed by cutting. - An explanation will then be made to a six example of the ball screw of the second embodiment by referring to
FIG. 11 .FIG. 11 is a view showing only the nut out of the ball screw manufactured by the same manufacturing process as that of the first example of the second embodiment shown inFIGS. 4 to 6 , in whichFIG. 11A is a front view, andFIG. 11B is a transversal longitudinal sectional view. The screw shaft and the balls of the ball screw according to the present embodiment are same with those of the first example in the second embodiment illustrated inFIG. 4 . Further, the circulatingpassage 11 and thescrew groove 5 a formed in thenut 5 are functionally equal thereto, though their shapes are slightly different, and so its detailed description is omitted for brevity's sake. - In the present embodiment, in the outer circumferential formation forming process shown in
FIG. 6 , acircumferential groove 39 of thenut 5 is integrally formed on the outer circumferential surface of thenut 5 e.g. by plastic working, and awear ring 40 is attached to thecircumferential groove 39. As is well known, because thewear ring 40 is provided for acting as a bearing with another member (not shown), thewear ring 40 allows supporting between thenut 5 and another member when thenut 5 is housed inside of another member. Thecircumferential groove 39 may be formed by cutting and grinding. - An explanation will next be made to a seventh example of the ball screw of the second embodiment by referring to
FIG. 12 .FIG. 12 is a view showing only the nut out of the ball screw manufactured by the same manufacturing process as that of the first example of the second embodiment shown inFIGS. 4 to 6 , in whichFIG. 12A is a front view, andFIG. 11B is a transversal longitudinal sectional view. The screw shaft and the balls of the ball screw according to the present embodiment are same with those of the first example in the second embodiment illustrated inFIG. 4 . Further, the circulatingpassage 11 and thescrew groove 5 a formed in thenut 5 are functionally equal, though their shapes are slightly different, and so its detailed description is omitted for brevity's sake. - In the present embodiment, a
motor rotor 41 is integrally provided e.g. by plastic working in the outer circumferential formation forming process shown inFIG. 6 . As the motor is configured by housing themotor rotor 41 within the motor stator (not shown), simply and directly a turning force to thenut 5 is obtainable. Alternately, themotor rotor 41 may be manufactured by cutting and grinding. - An explanation will then be made to an eighth example of the ball screw of the ball screw of the second embodiment by referring to
FIG. 13 .FIG. 13 is a view showing only the nut out of the ball screw manufactured by the same manufacturing process as that of the first example of the second embodiment shown inFIGS. 4 to 6 , in whichFIG. 13A is a front view, andFIG. 13B is a vertical longitudinal sectional view perpendicular to the axial line (hereinafter, referred to as a axial line-perpendicular vertical longitudinal sectional view). Thescrew shaft 3 and theballs 9 of theball screw 1 of the present embodiment are the same as those of the second embodiment shown inFIG. 1 . Further, the circulatingpassage 11 and thescrew groove 5 a formed in thenut 5 are functionally equal thereto, though their shapes are slightly different, and so its detailed description is omitted for brevity's sake. - In the present embodiment, an
inner ring 43 of a one-way clutch 48 is integrally provided on the outer circumferential surface of thenut 5 in the outer circumferential formation forming process shown inFIG. 6 . Theinner ring 43 per se of the one-way clutch 48 of the present embodiment is formed into a cylindrical body. The one-way clutch 48 includes anouter ring 44 to be fitted onto the outside in a radial direction of theinner ring 43, and aroller 45, as plural rolling elements, to be loaded between theinner ring 43 and theouter ring 44, as described in Patent Document JP 4,214,371 B proposed by the applicant of the present invention. In the present embodiment, a rollingbearing 46 is interposed at the both sides in an axial direction of theinner ring 43 on the outer circumferential surface of thenut 5 to rotatably support theinner ring 43 and theouter ring 44. In the present embodiment, acam face 47 is formed on an inner circumferential surface of theouter ring 44. When theinner ring 43 and theouter ring 44 relatively rotate in a direction indicated by an arrow A shown inFIG. 13A , theroller 45 is bite into thecam face 47 and the relative rotation of the both is restricted by a wedge effect. - On the other hand, when the
inner ring 43 and theouter ring 44 relatively rotate in a reverse direction from the arrow A, the wedge effect caused between theroller 45 and thecam face 47 is released, and they are permitted to freely and relatively rotate. Accordingly, the one-way clutch 48 only restricts the relative rotation in one direction of thenut 5 and theouter ring 44, or another member (not shown) to be installed in theouter ring 44. Instead, theinner ring 43 may be provided by cutting and grinding. -
FIG. 14 is a modification of theball screw 1 shown inFIG. 13 , in which theinner ring 43 of the one-way clutch 48 is a separate body different from thenut 5. Even in this situation, because thenut 5 of the present embodiment is devoid of a projection on the outer circumferential surface, the cylindricalinner ring 43 may be fitted, as it is, onto the outer circumferential surface of thenut 5. For example, provided that theinner ring 43 is, press fitted to the outer circumferential surface of thenut 5, the both may successfully be integrated. In addition, a deformation of theinner ring 43 due to fitting can be suppressed. - For the ball screw, a circulation system using the ball circulating passage includes a variety of systems, such as a tube system and a deflector system. For example, in case of the tube system, a return tube to communicate a start point with an endpoint of the ball rolling passage is fixed to the outer circumferential surface of the nut. Meanwhile, incase of the deflector system, a deflector in which a groove is formed to communicate a start point with an end point of the ball rolling passage is fitted into a deflector hole piercing through the inner circumferential surface and the outer circumferential surface of the nut. Moreover, a circulating system is known such that a concaved groove is formed by concaving a groove on a part of the inner circumferential surface of the nut to adopt the concaved groove as the ball rolling passage.
- When manufacturing such a ball screw, it has been worked by cold forging a cylindrical steal material to produce a substantially cylindrical (having a geometry virtually identical with the nut) blank; and the nut is manufactured by applying cutting to the blank. More preciously, the cutting working has been performed for formation of the through hole or the deflector hole through which the return tube pierces, formation of the concaved groove, and formation of the outer circumferential formation, such as the teeth train for a gear to the outer circumferential surface of the nut.
- In Patent Document 2, there is proposed a technology of manufacturing a nut having a desirable geometry using a sintered alloy.
- However, the manufacturing of the nut by cutting inherently entails a problem of undergoing a poor material yield and a high cost. What is more, since the sintered alloy has a low density and contains voids, the sintered alloy intrinsically involves a problem that it is difficult to have the satisfactory strength as a nut.
- Thereupon, an object of the third embodiment is to solve the above-identified problems of the prior art, and provide a manufacturing method of a ball screw with a high strength at a low cost, in addition to a high material yield.
- To solve the above problems, the third embodiment has the following structure. Namely, the manufacturing method of the ball screw of the third embodiment comprises: a screw shaft having on its outer circumferential surface a spiral groove; a nut having on its inner circumferential surface a screw groove facing the screw groove of the screw shaft; a plurality of balls rollably loaded in a spiral ball rolling passage formed by the both ball grooves; a ball circulating passage to return the balls from an end point to a start point of the ball rolling passage for circulating the balls; and an outer circumferential formation integrally provided on the outer circumferential surface of the nut, wherein the method involves a roughly forming step of producing a roughly formed nut having a shape virtually identical with the nut by plastic working from a cylindrical metal material; a ball circulating passage forming step of forming a concaved groove constituting the ball circulating passage by concaving a groove on a part of a cylindrical inner circumferential surface of the roughly formed nut.
- In the manufacturing method of the ball screw of the third embodiment, it is preferable for the plastic working, used in at least one of process, out of the roughly forming step, the ball circulating passage formation step, and the outer circumferential formation forming step to be implemented by cold forging. Further, the outer circumferential formation may be at least one a flange, a teeth train for a gear, a key seat, a bearing raceway groove, and another shape of circumferential surface.
- The manufacturing method of the ball screw of the third embodiment allows manufacturing of the ball screw with a high strength at a low cost, in addition to a high material yield.
- An explanation will then be made in detail to the ball screw of the third embodiment by referring to the drawings.
FIG. 1 is a cross-sectional view (a cross-sectional view taken with a plane in an axial direction). As shown IFIG. 1 , theball screw 1 includes: ascrew shaft 3 having on its outer circumferential surface aspiral screw groove 3 a; anut 5 having on its inner circumferential surface aspiral screw groove 5 a facing thescrew groove 3 a of thescrew shaft 3; a plurality ofballs 9 rollably loaded in a spiralball rolling passage 7 formed by the bothscrew grooves ball circulating passage 11 to return theballs 9 from an end point to a start point of theball rolling passage 7 for circulating the balls. - Namely, the
balls 9 rotate around thescrew shaft 3 while travelling through theball rolling passage 7, reach the end point of theball rolling passage 7 where theballs 9 are scooped up from one end of theball circulating passage 11, and returned to the start point of theball rolling passage 7 from the other end of theball circulating passage 11 through theball circulating passage 11. - It is noted that materials for the
screw shaft 3, thenut 5, and theballs 9 are not specifically limited to particular ones, and general materials may be available. For example, metal such as steel, etc., and ceramic may be given as a candidate. Further, a cross-sectional shape of thescrew grooves - Such a
ball screw 1 is configured such that when thenut 5 screwed via theballs 9 with thescrew shaft 3 and thescrew shaft 3 are relatively rotated, they relatively move in an axial direction through the rolling of theballs 9. An endless ball passage is formed of theball rolling passage 7 and theball circulating passage 11. As theballs 9 rolling through theball rolling passage 7 endlessly circulate through the endless ball passage, thescrew shaft 3 and thenut 5 are allowed to relatively move continuously. - Here, an explanation will be made in detail to the
ball circulating passage 11. The circulatingpassage 11 is integrally formed on the inner circumferential surface of thenut 5. More particularly, a concaved groove formed by concaving a groove on a part of the inner circumferential surface of thenut 5 by plastic working is taken as theball circulating passage 11. In this connection, a cross-sectional shape of theball circulating passage 11 may be an arc or the previously described gothic arc. Since theball screw 1 of the present embodiment adopts the ball circulating system using such aball circulating passage 11, the embodiment eliminates the need for providing another member (the return tube and the deflector) on thenut 5 constituting the ball circulating passage. Also, the embodiment eliminates the necessity for providing holes (the through hole and the deflector hole) to mount another member constituting the ball circulating passage. - Where the ball circulating system is the tube system and the deflector system, the member for constituting the ball circulating passage and the nut are separate bodies. In case of the tube system, the return tube is provided on the outer circumferential surface of the nut, whereas in case of the deflector system, the deflector is fitted into the deflector hole. For that reason, it could not provide the outer circumferential formation such as the flange on a portion where the return tube and the deflector are provided, out of the outer circumferential surfaces of the nut, resulting in a restriction on freedom of design of the outer circumferential surface of the nut.
- In contrast, the
ball screw 1 of the present embodiment, since theball circulating passage 11 is provided on the inner circumferential surface of thenut 5, the embodiment eliminates the need for providing any member on the outer circumferential surface. Additionally, as the embodiment eliminates the necessity for forming any hole such as the aforesaid through hole, the deflector hole, etc., thenut 5 is not subject to a restriction of a position where theball circulating passage 11 is provided and the number of cycle. This may give a high degree of freedom to design the outer circumferential surface all over the outer circumferential surface of thenut 5. Accordingly, the embodiment enables integrally forming the outer circumferential formation on the outer circumferential surface of thenut 5, even at a portion facing theball circulating passage 11 and thescrew groove 5 a on the outer circumferential surfaces of thenut 5. Theball screw 1 of the present embodiment is provided with theflange 13 as outer circumferential formation. Further, members such as the return tube, the deflector, etc., are not provided, thereby making it free from care of these members from falling out, which offers the highreliable ball screw 1. - The kind of the outer circumferential formation is not specifically limited to a particular one, rather a teeth train for a gear, a key seat, a baring raceway groove, and another shape of outer circumferential surface may be used, apart from the flange. For example, provided that the teeth train for a gear that consists of a plurality of teeth arranged in a circumferential direction is provided on the outer circumferential surface of the
nut 5, it enables thenut 5 to function as a gear. Moreover, given that the key seat is formed on the outer circumferential surface of thenut 5, thenut 5 can be connected with another member by engaging a key provided in another member into the key seat. Further, provided that a bearing raceway groove is formed on the outer circumferential surface of thenut 5, it enables thenut 5 to function as an inner ring of the rolling bearing. Furthermore, whereas the outer circumferential surface of thenut 5 typically has a cross section in circle, not limited thereto, another outer shape of circumferential surface, such as a polygonal cross section and an elliptical cross section may also be permitted. Incidentally, one of these outer circumferential formations may be provided on the outer circumferential surface of thenut 5, or two or more may be provided. For example, as with theball screw 1 of the present embodiment, theflange 13 may be provided on the outer circumferential surface of thenut 5, and the teeth train 15 for a gear may be provided on the outer circumferential surface of theflange 13. - While an application of the
ball screw 1 of the present embodiment is not specifically limited to a particular one, it may preferably be applied to an electric actuator to be built in a car, a motorcycle, a positioning device, etc. - An explanation of one example will next be made to a manufacturing method of the
ball screw 1 of the present embodiment by referring toFIG. 15 . In the present embodiment, acylindrical steel material 20 having the predetermined length (or mass) is worked by plastic working e.g. by cold forging, etc., to produce a blank 21 (roughly formed nut) having a shape virtually identical with the nut 5 (roughly forming process). At this time, theflange 13 is also provided on the outer circumferential surface of the blank 21 by plastic working. Therefore, the roughly forming process also serves as an outer circumferential forming process. - Then, the
concaved groove 22 constituting theball circulating passage 11 communicating an endpoint with a start point of theball rolling passage 7 is formed by concaving a groove on a part of a cylindrical inner circumferential surface of the blank 21 by plastic working such as cold forging, etc (ball circulating passage forming process). A specific example of a method of forming theconcaved groove 22 includes one as follows. That is, a punch with a convex having a shape corresponding to theconcaved groove 22 is inserted into the blank 21, the convex of the punch is brought into contact with the inner circumferential surface of the blank 21, and the punch is strongly pressed against the inner circumferential surface of the blank 21 to thereby form theconcaved groove 22. - It is noted that in what order the outer circumferential formation and the
ball circulating passage 11 should be provided is not specifically limited to a particular one, rather, it does not matter which of them is provided first. However, in the present embodiment, theball circulating passage 11 is formed after theflange 13 that is the outer circumferential formation is provided by plastic working, whereby a higher shape accuracy of theball circulating passage 11 is secured. - Next, the teeth train 15 for a gear including circumferentially arranged plural teeth are provided on the outer circumferential surface of the
flange 13 projecting into the outer circumferential surface of the blank 21 by plastic working such as cold forging. Alternatively, it is preferable to form the teeth train 15 for a gear by plastic working, but it may be formed by cutting. - Then, a
screw groove 5 a is formed on the inner circumferential surface of the blank 21 by cutting (screw groove forming process). Finally, thenut 5 is manufactured by applying heat treatment, such as hardening and tempering, thereto under a desired condition. An example of hear treatment includes carburizing, carbonitriding, induction heat treatment, etc. - By combining the
nut 5 thus manufactured by this way with thescrew shaft 3 and theball 9 manufactured by the traditional method, theball screw 1 is manufactured. - Since all the aforesaid roughly forming process, the ball circulating passage forming process, and the outer circumferential formation forming process are performed by the plastic working, the manufacturing method of the
ball screw 1 allows producing a ball screw with high precision at a low cost, in addition to a high material yield. Further, owing to the manufacturing by plastic working, a metal flow (fiber flow) having thesteel material 20 is hardly cut and subject to work hardening, thereby providing thenut 5 with a high strength. - The kind of the plastic working is not specifically limited to a particular one, but forging is preferable, and cold forging is more preferable. Instead, adopting hot forging is also possible, but since the cold forging provides high accurate finishing as compared with the hot forging, it may provide the
nut 5 with satisfactory high precision, without applying a post process. As a result, theball screw 1 can be manufactured at a low cost. - It is preferable to adopt the plastic working as the cold forging in all the manufacturing processes, out of the roughly forming process, the ball circulating passage forming process, and the outer circumferential formation forming process, but it may substitute the plastic working for the cold forging in either one or in two processes.
- The fourth embodiment is directed to a nut constituting a ball screw and a manufacturing method thereof.
- The ball screw is a device including: a nut having on its inner circumferential surface a spiral groove; a screw shaft having on its outer circumferential surface a spiral groove; balls loaded between a raceway formed of the spiral groove of the nut and the spiral groove of the screw groove; and a ball returning passage to return the balls from an end point to a start point of the raceway, wherein the nut relatively moves relative to the screw shaft through the rolling of the balls within the raceway.
- Such a ball screw is utilized not only for a positioning device of general industrial machinery but also for an electric actuator to be built in vehicles such as a car, a motorcycle, or a ship.
- The ball returning passage of the ball screw includes a circulating tube system and a deflector system. In case of the deflector system, the deflector having a concave constituting the ball returning passage is fitted into a through hole of the nut. On the other hand, in
Patent Document 3, there is disclosed that a concave (circulating groove) constituting the ball returning passage is directly formed on an inner circumferential surface of a nut blank by plastic working. As to how to form the ball returning passage will be described by referring toFIG. 28 . - Firstly, a die equipped with a cylindrical working
head 130 having S-shapedconvexes stand 190, with its axial direction being oriented toward a horizontal direction; adistal end 130 b and abase end 130 a are fixed with theconvexes head 130 placed inside of thenut blank 101. Then, pressing pressure is applied, in this state, to anupper member 120 of the die to go down it, and the convexes 137 and 138 are pressed against the innercircumferential surface 111 of the nut blank 101 to thereby cause the innercircumferential surface 111 of the nut blank 101 to be subject to plastic deformation. - In the manufacturing method of such a ball screw nut, where a projection (a flange, a rotational or an axial stopper, positioning at the time of machining and mounting, power transmission, projection for the purposes of torque transmission, etc) is provided on the outer circumferential surface of the nut, cutting is adopted.
- Further, Patent Document 2 proposes to integrally form a nut having a concave (a return groove) constituting a ball returning passage, a spiral groove (inner screw groove), and a projection (a portion forming an outside surface) on an outer circumferential surface using sintered metal.
- However, the manufacturing of the nut by cutting is problematic in that it inflicts a lower material yield and a high cost. There is also a problem that it is difficult for the nut to have the satisfactory strength due to containing of pores in the sintered alloy, in addition to its low density.
- The object of the fourth embodiment is to solve the above-identified problems of the prior art, and provides a method of capable of manufacturing a ball screw nut with a high strength at a low cost, in addition to a high material yield.
- To solve the above problems, the manufacturing method of a first ball screw nut of the fourth embodiment includes: a nut having a spiral screw groove on its inner circumferential surface and having a projection on its outer circumferential surface; a screw shaft having on its outer circumferential surface a spiral screw groove; and balls rollably loaded in a spiral ball rolling passage formed by the spiral screw groove of the nut and the spiral screw groove of the screw shaft; and a ball returning passage which is formed on the inner circumferential surface as a concave to return the balls from an end point to a start point of the ball rolling passage, wherein the ball screw nut where the nut relatively moves relative to the screw shaft through the rolling of the balls, and wherein formation of the concave on the inner circumferential surface of the nut and formation of the projection is simultaneously performed by cold forging.
- The manufacturing method of a second ball screw nut of the fourth embodiment includes: a nut having on its inner circumferential surface a spiral groove and on its outer circumferential surface a projection; a screw shaft having on its outer circumferential surface a spiral groove; balls rollably loaded between a raceway formed by the spiral screw groove of the nut and the spiral screw groove of the screw shaft; and a ball returning passage which is formed as a concave on the inner circumferential surface of the nut to return the balls from an end point to a start point of the raceway, wherein the nut relatively moves relative to the screw shaft through the rolling of the balls, and wherein a concave is formed on the inner circumferential surface of the nut blank by pressing the inner circumferential surface of the nut blank with the convex, by press method (cold forging) using a die of the cam mechanism comprising a cam driver internally inserted into a cylindrical nut blank and moving in its axial direction; a cam slider which is disposed between the nut blank and the cam driver, and the convex corresponding to the concave is provided, the convex moving in a radial direction of the nut with the movement of the cam driver; and a restraining member for restraining both end faces in an axial direction and the outer circumferential surface of the nut blank, and on an inner circumferential surface of which a recess is formed to receive the outer circumferential surface, and wherein the projection is formed by projecting a periphery of the nut blank into a recess of the restraining member.
- This method solves the following problems. In other words, in
Patent Document 3, there is a problem that when the nut has a long axial dimension and a small inner diameter, damage may occur due to the insufficient strength of the working head of the die, as the working head of the die becomes elongate. Further, because a flow of materials with the formation of the concave cannot be controlled, the flow goes toward in an axial direction of the nut blank, leading to a deformation of the axial both end faces of the nut blank into a projection. Moreover, there is also a problem that as the axial end faces of the nut blank come to a reference plane for processing by spiral groove working that is the next process, the projection induces degradation in machining accuracy of the spiral groove as it stands. - According to this method, a movement in an axial direction of the cam driver changes its direction to an radial direction on a slope constituting the cam mechanism to transmit it to the cam slider, and the concave is formed on the inner circumferential surface of the nut blank by pressing and plastically deforming the inner circumferential surface of the nut blank with the convex provided in the cam slider. Even when manufacturing a nut having a long axial dimension and a small inner diameter, damage is hardly given to the die as compared with the method disclosed in
Patent Document 3. - Since the axial both end faces of the nut blank and the outer circumferential surface are restrained by the restraining member, and the projection is provided by projecting a periphery of the nut blank into the recess of the restraining member, the both ends in an axial direction of the nut blank are hardily subject to deformation at the time of the formation of the concave. As the end faces in an axial direction of the nut blank come to the reference plane for processing by the spiral groove working that is the next process, the spiral groove working accuracy will be enhanced at the time of being used as it is.
- Further, according to the method, since the projection is provided on the outer circumferential surface of the nut blank, concurrently with the formation of the concave by cold forging, the material will not be wasted as in the case where the projection is provided by cutting.
- In the manufacturing method of the first or the second ball screw nut of the fourth embodiment, the projection, the concave or the tapered surface being formed on the inner circumferential surface of the projection is adopted to a reference plane or a holding part to proceed the working after the next process.
- A ball screw nut manufactured by the first or the second method according to the fourth embodiment includes a ball screw nut where the projection is an axial force transmission part, a torque transmission part, a positioning part, or a mounting part.
- According to the first method of the fourth embodiment, the embodiment can manufacture the ball screw nut with a high strength, at a reduced working cost and at a low cost, in addition to a high material yield.
- According to the second method of the fourth embodiment, even when the nut having a long axial dimension and a small inner diameter is manufactured, as a method of directly forming by plastic working a concave constituting the ball returning passage on the inner circumferential surface of the nut blank, the concave can be formed without giving damage to the die, as well as suppressing the deformation of the both ends in an axial direction of the nut blank. Also, as the projection is provided on the outer circumferential surface of the nut blank simultaneously with the formation of the groove, the material cost can be reduced as compared with the case where the projection is manufactured by cutting.
- An explanation will next be made to the fourth embodiment in detail.
- In the first example, a
stopper 191 projecting to the outer circumferential surface of thenut blank 101 is provided at the outside in an radial direction of an S-shaped concave 115 by a method shown inFIG. 16 , concurrently with the formation of the S-shaped concave (concave constituting the ball returning passage) 115 on the inner circumferential surface of thenut blank 101. - A die to be used in the first example, as shown in
FIG. 16 , the die includes ablank holder 102 having a concave 121 to hold the nut blank 101; alid member 122 to restrain an upper end face of the nut blank 101; acam slider 103 and acam driver 104 to be disposed inside of thenut blank 101. On an inner circumferential surface of the concave 121 of theblank holder 102, therecess 121 a having a shape corresponding to thestopper 191 is formed. The concave 121 of theblank holder 102 and thelid member 122 constitute the restraining member for restraining the both end faces in an axial direction and an outer circumferential surface of thenut blank 101. - The
cam slider 103 is, as shown inFIGS. 17A and 17B , a substantially semi-cylindrical member having aplane 132 parallel to an outercircumferential surface 131 in an axial direction, wherein the diameter of a circle defining the outercircumferential surface 131 is smaller than the diameter of acircle 111 a defining the innercircumferential surface 111 of thenut blank 101. On aplane 132 of thecam slider 103, aslope 133 extending in an axial direction is provided at a middle portion in a radial direction. Theslope 133 corresponds to a plane connecting abase line 134 a of the concave 134 at one end in an axial direction (upper end) and aline 132 d forming a lower end of theplane 132. Moreover, an S-shaped concave 135 corresponding to an S-shaped concave 115 is provided on the outercircumferential surface 131 of thecam slider 103. - The
cam driver 104 is, as shown inFIG. 17C , a long plate-shaped member, oneside face 141 of which has a slope having the same slant as theslope 133 of thecam slider 103, and theother side 142 of which has a periphery along acircle 111 a defining the innercircumferential surface 111 of thenut blank 101. The dimensions in an axial direction of thecam driver 104 are longer than that of thecam slider 103. Further, the width of thecam driver 104 is thinner than the width corresponding to an open width (dimensions between the both sides of the slope 133) of the concave 134 of thecam slider 103. - The
slope 131 of thecam slider 103 and the slantedside face 141 of thecam driver 104 constitute the cam mechanism of the die. - Firstly, the
nut blank 101 is disposed in the concave 121 of theblank holder 102 using this die, and thelid member 122 is placed on an upper end face of the nut blank 101 to restrain the both ends in an axial direction of thenut blank 101 and the outer circumferential surface of thenut blank 101. Secondly, thecam slider 103 is inserted into the inside of the nut blank 101, with the concave 134 side being set upward and the S-shaped convex 135 oriented toward the innercircumferential surface 111 of thenut blank 101. In this instance, the S-shaped convex 135 of thecam slider 103 is aligned with therecess 121 a of theblank holder 102. - Then, the
cam driver 104 is inserted between thecam slider 103 and thenut blank 101. On this occasion, a portion at theside face 141 of thecam driver 104 is fitted into the concave 134 of thecam slider 103 to bring theslope 133 of thecam slider 103 into contact with the slantedside face 141 of thecam driver 104.FIG. 16A shows this state. - After that, when pressing the
cam driver 104 from above by applying pressing pressure, a force is transmitted from the slantedside face 141 of thecam driver 104 to theslope 133 of thecam slider 103. Accompanying thereto, a downward force of thecam driver 104 is converted into a force moving thecam slider 103 to the radial outside, and the S-shaped convex 135 provided in thecam slider 103 presses the innercircumferential surface 111 of the nut blank 101 to cause it to be subject to plastic deformation. Accompanying thereto, materials existing on the outer circumferential surface of the nut blank 101 are pushed into therecess 121 a of theblank holder 102.FIG. 16B shows this state. - Thereby, the S-shaped concave 115 is formed in the inner
circumferential surface 111 of the nut blank 101, a periphery of the nut blank 101 projects and therecess 121 a is formed, which provides thestopper 191 on the outer circumferential surface of thenut blank 101. A state where thenut blank 101 is removed from the die is shown inFIG. 18 . - Thus, according to the method of the first example, even when the nut having a long axial dimension and a small inner diameter is manufactured, the S-shaped concave 115 can be formed, without giving damage to the
cam driver 104. Further, as the material of the nut blank 101 pressed to the outside in an radial direction by the S-shaped convex 135 goes toward therecess 121 a, deformation hardly occurs on the both end faces in an axial direction of thenut blank 101. The end faces in an axial direction of the nut blank 101 may be adopted as a reference plane for processing in the spiral groove machining that is the next process. Therefore, even if the spiral groove is applied using as it is, good machining accuracy is guaranteed. - Further, as the stopper (projection) 191 is provided on the outer circumferential surface of the nut blank 101, simultaneously with the formation of the S-shaped concave 115, a low material cost may be achieved, as compared with the case where the
stopper 191 is manufactured by cutting. Moreover, since thestopper 191 is provided when materials making the nut blank 101 flow in an radial direction, a metal flow (fiber flow) is hardly cut and subject to work hardening, thestopper 191 may have the strength high enough to resist an axial force and torque. - In the second example, a
stopper 192 projecting into the outer circumferential surface of thenut blank 101 is formed at an one end in an axial direction, concurrently with the formation of the S-shaped concave (concave constituting the ball returning passage) 115 on the inner circumferential surface of the nut blank 101 by using a method shown inFIG. 19 . - A die to be used in the second example includes: as shown in
FIG. 19 , theblank holder 102 having the concave 121 to hold the nut blank 101; thelid member 122 to restrict an upper end face of the nut blank 101; and thecam slider 103A and thecam driver 104 to be disposed inside of thenut blank 101. On an upper end of the inner circumferential surface of the concave 121 of theblank holder 102, therecess 121 b having a shape corresponding to thestopper 192 is formed. The concave 121 and thelid member 122 of theblank holder 102 constitute the restraining member for restraining the both end faces in an axial direction and the outer circumferential surface of thenut blank 101. - The
cam slider 103A is, as shown inFIGS. 20A and 20B , a substantially semi-cylindrical member having aplane 132 parallel with the outercircumferential surface 131 in an axial direction, where the diameter of a circle defining the outercircumferential surface 131 is slightly smaller than that of acircle 111 a defining the innercircumferential surface 111 of thenut blank 101. On theplane 132 of thecam slider 103A, theaxially extending slope 133 is provided at a middle portion in an radial direction. Theslope 133 corresponds to a plane connecting abase line 134 a of the concave at axial one end (upper end) and aline 132 d defining a lower end of theplane 132. - On the outer
circumferential surface 131 of thecam slider 103A, the S-shaped convex 135 corresponding to the S-shaped concave 115 is provided. Further, on the outercircumferential surface 131 of thecam slider 103A, a convex 136 for forming thestopper 192 is provided at a position corresponding to therecess 121 b. - The
cam driver 104 is, as shown inFIG. 20C , a long plate-shaped member, oneside face 141 of which has a slope having the same slant as theslope 133 of thecam slider 103A, and theother side 142 of which has a periphery along acircle 111 a defining the innercircumferential surface 111 of thenut blank 101. The dimension in an axial direction of thecam driver 104 is longer than that of thecam slider 103A. Further, the width of thecam driver 104 is thinner than the width corresponding to an open width (dimensions between the both sides of the slope 133) of the concave 134 of thecam slider 103A. - The
slope 131 of thecam slider 103A and the slantedside face 141 of thecal slider 103A constitute the cam mechanism of the die. - Firstly, the
nut blank 101 is disposed in the concave 121 of theblank holder 102 using this die, and thelid member 122 is placed on an upper end face to restrain the both ends in an axial direction of thenut blank 101 and the outer circumferential surface of thenut blank 101. Secondly, thecam slider 103A is inserted into the inside of the nut blank 101, with the concave 134 side being set upward and the S-shaped convex 135 and the convex 136 oriented toward the innercircumferential surface 111 of thenut blank 101. In this instance, the convex 136 of thecam slider 103 is aligned with therecess 121 a of theblank holder 102. - Then, the
cam driver 104 is inserted into between thecam slider 103A and thenut blank 101. On this occasion, a portion on theside face 141 side of thecam driver 104 is fitted into the concave 134 of thecam slider 103A to bring theslope 133 of thecam slider 103A into contact with the slantedside face 141 of thecam driver 104.FIG. 19A shows this state. - After that, when pressing the
cam driver 104 from the top thereof by applying a pressing pressure, a force is transmitted from theslant side face 141 of thecam driver 104 to theslope 133 of thecam slider 103A. At the same time, a downward force of thecam driver 104 is converted into a force moving thecam slider 103A to the outside in a radial direction, and the S-shaped convex 135 and the convex 136 provided in thecam slider 103A presses the innercircumferential surface 111 of the nut blank 101 to cause it to be subject to plastic deformation. Accompanying thereto, a portion, pressed by the S-shaped convex 135, in the material forming the nut blank 101 moves upward, a portion (materials existing on the outer circumferential surface of the nut blank 1) pressed by the convex 136 to the outside in an radial direction is pressed into therecess 121 b of theblank holder 102.FIG. 20B shows this state. - Thereby, the S-shaped concave 115 is formed on the inner
circumferential surface 111 of the nut blank 101, a periphery of the nut blank 101 projects into therecess 121 b, which provides thestopper 192 on the outer circumferential surface of thenut blank 101. Similarly, a concave 116 corresponding to the convex 136 is formed on the inner circumferential surface of thestopper 192. A state where thenut blank 101 is removed from the die is shown inFIG. 21 . - Thus, according to the method of the second example, even when the nut having a long axial dimension and a small inner diameter is manufactured, the S-shaped concave 115 can be formed, without giving damage to the
cam driver 104. Further, as the material making the nut blank 101 pressed by the S-shaped convex 135 and the convex 136 goes toward therecess 121 b, deformation hardly occurs on the both end faces in an axial direction of thenut blank 101. The end faces in an axial direction of the nut blank 101 may be adopted as a reference plane for processing in a spiral groove working that is the next process. Therefore, even if the grooving is applied using as it is, good working accuracy is guaranteed. - Further, as the stopper (projection) 192 is provided on the outer circumferential surface of the nut blank 101, simultaneously with the formation of the S-shaped concave 115, low material cost can be achieved, as compared with the case where the
stopper 192 is manufactured by cutting. Moreover, since thestopper 192 is provided when materials of the nut blank 101 flow in a radial direction, a metal flow (fiber flow) is hardly cut and subject to work hardening, thestopper 192 may have the strength high enough to resist an axial force and torque. - In the third example, in a method illustrated in
FIG. 22 , a pair of thestoppers 193 projected into the outer circumferential surface of thenut blank 101 is provided at an end in an axial direction, concurrently with the formation of the S-shaped concaves (concave constituting the returning passage) 115 a and 115 b in two points on the outer circumferential surface of thenut blank 101. - A die to be used in the third example includes: as shown in
FIG. 22 , theblank holder 102 having the concave 121 to hold the nut blank 101; thelid member 122 to restrain an upper end face of the nut blank 101; a pair of thecam slider cam driver 106 to disposed between the bothcam sliders blank holder 102, there are provided a pair of therecesses 121 c each having a shape corresponding to the pair of thestoppers 193. The concave 121 of theblank holder 102 and thelid member 122 constitutes the restraining member for restraining the both end faces in an axial direction and the outer circumferential surface of thenut blank 101. - Each of the
cam sliders FIGS. 23A and 23B , a substantially semi-cylindrical member having an outercircumferential surface 151 of which diameter is slightly smaller than an inner diameter of the nut blank 101, and aline 152 defining an opposite face of the outercircumferential surface 151 is smaller than an inner diameter of thenut blank 101. Thus, as shown inFIG. 23A , when the outercircumferential surfaces 151 of thecam sliders circle 111 a defining the innercircumferential surface 111 of the nut blank 101, agap 152 a is generated between thelines 152 of the bothcam sliders - On the
opposite face 152 b (face along a line 152) of the bothcam sliders axially extending slope 153 is formed at a middle portion of theline 152. Theslope 153 corresponds to a plane connecting abase line 154 a of the concave 154 at one end (upper end) in an axial direction and aline 152 of a lower end. Further, the S-shapedconvexes concaves circumferential surface 151 of the eachcam slider circumferential surface 151 of each of thecam sliders stopper 193 is formed at a position corresponding to the eachrecess 121 c. - The
cam driver 106 is, as shown inFIG. 23C , a long quadrangular prism comprising: aslope 161 havingslopes base end 162 of which both end faces have a parallel surface to each other. Theslopes cam driver 106 are identical with theslopes 153 of thecam sliders slopes slopes 153 of thecam sliders slope 161 of thecam driver 106 may be received in theconcaves 154 of thecam sliders - The
slopes 153 of thecam slider slopes cam driver 106 constitute the cam mechanism of the die. - Firstly, the
nut blank 101 is disposed in the concave 121 of theblank holder 102, and thelid member 122 is placed on an upper end face of the nut blank 101 to restrain the both end faces in an axial direction and an outer circumferential surface of thenut blank 101. Secondly, a pair of thecam sliders slopes 153 face each other. On this occasion, theconvexes 156 of thecam sliders respective recesses 121 c of theblank holder 102. - Next, the
cam driver 106 is inserted between the bothcam sliders slopes 153 of the bothcam sliders slopes cam driver 106.FIG. 22A shows this state. - Then, when the
cam driver 106 is pressed from the top thereof by applying a pressing pressure, a force is transmitted from theslopes 161 a and 16 ab of thecam driver 106 to theslopes 153 of the bothcam sliders cam driver 106 is converted into a force moving each of thecam sliders convexes respective cam slider circumferential surface 111 of the nut blank 101 to cause it to be subject to plastic deformation. - Accompanying thereto, a portion, pressed by the S-shaped
convexes recess 121 c of theblank holder 102.FIG. 22B shows this state. - Thereby, the S-shaped concave 115 a and 115 b are provided at two points of the inner
circumferential surface 111 of the nut blank 101, and an external circumference of the nut blank 101 projects into therecess 121 c, and thestopper 193 is provided on the outer circumferential surface of thenut blank 101. Further, on the inside of thestopper 193, a concave 117 corresponding to the convex 156 is formed. A state where thenut blank 101 is removed from the die is shown inFIG. 24 . - Thus, according to the method of the third example, even when the nut having a long axial dimension and a small inner diameter is manufactured, the S-shaped concave 115 can be formed, without giving damage to the
cam driver 106. Further, as the material forming the nut blank 101 pressed by the S-shaped convex 155 and the convex 156 goes toward therecess 121 c, deformation hardly occurs on the both end faces in an axial direction of thenut blank 101. The end faces in an axial direction of the nut blank 101 may be adopted as a reference plane for processing in the spiral groove working that is the next process. Therefore, even if the grooving is applied as it is, good working accuracy is guaranteed. Additionally, the end faces in an axial direction of the nut blank 101 are subject to work hardening, and thus they are suited for a reference plane for processing. - Further, as the stopper (projection) 193 is provided on the outer circumferential surface of the nut blank 101, simultaneously with the formation of the S-shaped concave 115, a low material cost can be achieved, as compared with the case where the
stopper 193 is manufactured by cutting. Moreover, since thestopper 193 is provided when materials forming the nut blank 101 flow in a radial direction, a metal flow (fiber flow) is hardly cut and subject to work hardening, thestopper 191 may have the strength high enough to resist an axial force and torque. The formation of a bolt insertion hole in thestopper 193 makes it available as a fitting flange for the nut. - In the fourth example, in a method illustrated in
FIG. 25 , aflange 194 is provided on the outer circumferential surface at one end in an axial direction of the nut blank 101, and atapered surface 118 is formed on an internal circumference thereof, concurrently with the formation of S-shaped concaves (concaves constituting a ball returning passage) 115 a and 115 b at two points on the inner circumferential surface of thenut blank 101. - A die includes: as shown in
FIG. 25 , theblank holder 102 having the concave 121 to hold the nut blank 101; thelid member 122 to restrain an upper end face of the nut blank 101; a pair ofcam slider 107A, 107B to be disposed inside of the nut blank 101; and thecam driver 108 to be disposed between the bothcam sliders 107A and 107B. On an upper end of the inner circumferential surface of the concave 121 of theblank holder 102, a circumferential groove (recess) 121 d having a shape corresponding to theflange 194 is formed. The concave 121 of theblank holder 102 and thelid member 122 constitute the restraining member for restraining both end faces in the axial direction and the outer circumferential surface of thenut blank 101. - The
cam sliders 107A and 107B have a shape where an end at which the convex 156 is provided is cut in an axial direction, including the convex 156, from thecam sliders convexes slope 153 of thecam sliders concaves - The
cam driver 108 has aramp 181 havingslopes cam sliders 107A and 107B, and a base end at which atapered surface 182 a corresponding to the taperedsurface 118 is formed. The slope 173 of thecam sliders 107A and 107B and theslopes cam driver 108 constitute the cam mechanism of the die. - Firstly, the
nut blank 101 is disposed in the concave 121 of theblank holder 102 using this die, and thelid member 122 is placed on an upper end face of the nut blank 101 to restrain the both ends in an axial direction and the outer circumferential surface of thenut blank 101. Secondly, a pair of thecam slider 107A, 107B is inserted into the inside of the nut blank 101 so that the both slopes face each other. - Then, the
cam driver 108 is inserted into between the concaves (identical with theconcaves 154 of thecam sliders cam sliders 107A and 107B is formed to bring the slope 173 of the bothcam sliders 107A and 107B into contact with aslopes cam driver 108.FIG. 25A shows this state. - After that, when pressing the
cam driver 108 from above by applying pressing pressure, a force is transmitted from theslopes cam driver 108 to the slope 173 of the bothcam sliders 107A and 107B. Accompanying thereto, a downward force of thecam driver 108 is converted into a force moving thecam sliders 107A and 107B to the outside in a radial direction, and the S-shapedconvexes cam slider 107A and 107B press the innercircumferential surface 111 of the nut blank 101 to cause it to be subject to plastic deformation. Further, thetapered surface 182 a of thecam driver 108 presses and plastically deforms the upper portion of the innercircumferential surface 111 of thenut blank 101. - Accompanying thereto, a portion, pressed by the S-shaped
convexes surface 182 a to the outside in a radial direction is pushed into acircumferential recess 121 d of theblank holder 102.FIG. 25B shows this state. - Thereby, the S-shaped
concaves circumferential surface 111 of the nut blank 101, the external circumference of the nut blank 101 projects into thecircumferential recess 121 d, which provides theflange 194 on the outer circumferential surface of thenut blank 101. A tapered surface 113 corresponding to the taperedsurface 182 a is formed inside of theflange 194. A state where thenut blank 101 is removed is shown inFIG. 26 . - Thus, according to the method of the fourth example, even when the nut having a long axial dimension and small inner diameter is manufactured, the S-shaped
concaves cam driver 108. Further, because the material forming the nut blank 101 pressed by the S-shapedconvexes tapered surface 118 flows toward thecircumferential recess 121 d, deformation hardly occurs on the end faces in an axial direction of thenut blank 101. The end faces in an axial direction of the nut blank 101 may be adopted as a reference plane for processing in spiral groove working that is the next process. Besides, the end faces in an axial direction of the nut blank 101 are work hardened, and thus they are suited for a reference plane for processing. - Further, as the flange (projection) 194 is provided on the outer circumferential surface of the nut blank 101, simultaneously with the formation of the S-shaped
concaves flange 194 is manufactured by cutting. Moreover, since theflange 194 is provided when materials making the nut blank 101 flow in an radial direction, a metal flow (fiber flow) is hardly cut and subject to work hardening, theflange 194 may have the strength high enough to resist an axial force and torque. - The
flange 194 may be used as a flange for mounting parts such as a bearing on the outer circumferential surface of the nut. Likewise, thetapered surface 118 may be used as the center (surface for center alignment in grinding of cylinder). Further, by forming a bolt insertion hole in theflange 194, it may be used as a mounting flange for the nut. Moreover, gear cutting may be done on an external circumference of theflange 194 to manufacture a gear. - As shown in
FIG. 27 , previously forming the concave 196 on the underside of theupper member 120 of the die simultaneously enables by cold forging formation of the concave 197 on the innercircumferential surface 111 of the nut blank 101, and formation of aprojection 198 on the outer circumferential surface of the nut blank 101 in exactly the same way as the case shown inFIG. 28 . - The fifth embodiment is directed to a manufacturing method of the nut constituting the ball screw and a ball screw nut manufactured thereby.
- The ball screw includes: the nut having on its inner circumferential surface a spiral groove; the screw shaft having on its outer circumferential surface a spiral groove; balls loaded between a raceway formed by the spiral groove of the nut and the spiral groove of the screw shaft; and the ball returning passage to return the balls from an end point to a start point of the raceway. The ball screw is a device in which the balls roll within the raceway to thereby relatively move the nut with respect to the screw shaft.
- Such a ball screw is provided not only for a positioning device, etc. for general industrial machinery, but also for an electric actuator to be installed in vehicles such as a car, a motorcycle, a ship, etc.
- The ball returning passage of the ball screw includes a circulating tube system and a deflector system. In case of the deflector system, a deflector having a concave constituting the ball returning passage is fitted into a through hole of the nut. On the other hand, in
Patent Document 3, there is disclosed directly defining by plastic working a concave (circulating groove) constituting the ball returning passage on the inner circumferential surface of the nut blank. As for the manufacturing method thereof, it is as stated in the fourth embodiment. - The method disclosed in
Patent Document 3, however, intrinsically entails a problem that when the nut has a long axial dimension and a small inner diameter, damage may occur due to the strength poverty of the working head of the die, as the working head of the die becomes elongate. - The present invention is contrived focusing on the above-identified problems, and its object is to provide a manufacturing method of a ball screw nut which is able to form a concave, without giving damage to the die, and to attenuate an impact on outside accuracy of the nut, even when a nut having a long axial dimension and a small inner dimension is manufactured, as a method of directly forming by plastic working the concave constituting the ball returning passage on the inner circumferential surface of the nut blank.
- Further, yet another object of the present invention is to provide a ball screw and a manufacturing method thereof which is able to prevent adhesion on butting of the nut against the housing, and to suppress collision energy generated thereat.
- To solve the above-identified problems, the manufacturing method of the ball screw nut of the fifth embodiment includes: the nut having on its inner circumferential surface a spiral groove; the screw shaft having on its outer circumferential surface a spiral groove; balls loaded between a raceway formed by the spiral groove of the nut and the spiral groove of the screw shaft; and the ball returning passage provided as a concave on the inner circumferential surface of the nut for returning the balls from an end point to a start point of the raceway, wherein the nut relatively moves with respect to the screw shaft by rolling the balls with the raceway, and wherein the concave is formed on the inner circumferential surface of the nut blank by pressing the inner circumferential surface of the nut blank with a convex, by a press method using a die of the cam mechanism, the cam mechanism comprising: a cam driver internally inserted into a cylindrical nut blank and moving in an axial direction; a cam slider disposed between the nut blank and the cam driver, and having the convex corresponding to the concave, the convex moving in a radial direction of the nut with a movement of the cam driver; and a restraining member for restraining both end faces in the axial direction and the outer circumferential surface of the nut blank, and having a recess on an end face to receive the end face in the axial direction of the nut blank, wherein the outer circumferential formation is formed by projecting a periphery of the nut blank into the recess of the restraining member.
- According to the fifth embodiment, a movement in the axial direction of the cam driver on a slope defining the cam mechanism changes its direction to the radial direction to transmit it to the cam slider; and the convex provided in the cam slider presses the inner circumferential surface of the nut blank to cause it to be subject to plastic deformation, which forms the concave on the inner circumferential surface of the nut blank. Then, even when the nut having a long axial dimension and a small inner diameter is manufactured, the die is hardly subject to damage, as compared with the method disclosed in
Patent Document 3. - Since the both end faces in an axial direction and the outer circumferential surface of the nut blank are restrained by the restraining member, and the end face of the nut blank is projected into the recess of the restraint member, it may reduce an impact on the outer dimension accuracy of the nut.
- Further, the ball screw of the fifth embodiment is a ball screw including: the nut having on its inner circumferential surface a spiral groove; a screw shaft having on its outer circumferential surface a spiral groove; balls loaded between a raceway formed by the spiral groove of the nut and the spiral groove of the screw shaft; and the ball returning passage provided as a concave on the inner circumferential surface of the nut, for returning the balls from an end point to a start point of the of the raceway, wherein a convex is provided at an end face in an axial direction of the nut.
- With the ball screw according to the fifth embodiment, since the end face of the nut is projected, the embodiment prevents adhesion occurred on butting of the nut against the housing, thereby suppressing collision energy.
- According the fifth embodiment, as a method of directly manufacturing the concave constituting the ball returning passage on the inner circumferential surface of the nut by plastic working, even when the nut having a long axial dimension and a small inner diameter is manufactured, the embodiment enables formation of the concave, without giving damage to the die, as well as reduction of an impact on the outer dimension accuracy. Additionally, to project the end face of the nut, thereby providing the ball screw of which collision energy is decreased to prevent the adhesion on colliding of the nut.
- An explanation will then be made to a first example of a manufacturing method of the ball screw according to the fifth embodiment by referring to drawings.
FIG. 29 is a cross-sectional view showing a construction in the first example of the manufacturing method of the fifth embodiment.FIG. 30 is a view showing a cam driver, in whichFIG. 30A is a perspective view,FIG. 30B is a plane view, andFIG. 30C is a perspective view.FIG. 31 is a view showing a split constituting a restraining member used in the first example, in whichFIG. 31A is a plane view,FIG. 31B is a cross section taken along a line A-A, andFIG. 31C is a cross-sectional view of a stand.FIG. 32 is a plain view showing a nut blank in which an S-shaped concave and a convex are formed, in whichFIG. 32A is a front view,FIG. 32B is a cross-sectional view taken along a line A-A, andFIG. 32C is a perspective view. - As shown in
FIGS. 29 to 31 , a die used in the first example includes acam driver 202 to be inserted inside of a nut blank 201;cam sliders 203A to 203D to be disposed between thenut blank 201 and thecam driver 202; astand 204 in which a concave 241 having the same inner diameter as thenut blank 201 is formed at the center of a top surface; a restrainingmember 205 for restraining an upper end surface and an outer circumferential surface of the nut blank 201; and anouter member 206 for restraining a movement to the outside of the restrainingmember 205. - The
cam driver 202 is, as shown inFIG. 30A , a bar member having a square cross section, wherein the cam driver includes abase end 221 in which the size of a square in section is unchanged in an axial direction, and abody 222 in which the size of a square in section gets smaller as it goes toward an end. In other words, foursides 221 a to 221 d of thebase end 221 are respectively parallel with one another, back and forth and right and left, and the foursides 222 a to 222 b of the body have a slope with the same inclination. -
Cam sliders 203 A to 203D are, as shown inFIGS. 30B and 30C , a member in which a cylinder having the diameter slightly smaller than the inner diameter of thenut member 201 is divided into four in a circumferential direction. At the opposite side of the outercircumferential surface 231, aslope 233 with the same inclination as the fourslopes 222 a to 222 b of thecam driver 202 is provided. Arranging thecam sliders 203A to 203D matching with the outercircumferential surface 231 to acircle 211 a defining the innercircumferential surface 211 of thenut blank 201 creates a space at the center of thecircle 211 a into which thecam driver 202 is inserted, with the fourslopes 233, at the center of thecircle 211 a. Moreover, on the outercircumferential surface 231 of the eachcam slider 203A to 203D, S-shapedconvexes 235A to 235D corresponding to the S-shaped convex constituting the four ball returning passages is provided. - The
slopes 222 a to 222 d of thecam driver 202 and the slope 238 of the cam slider 203 constitute the cam mechanism of the die. - The restraining
member 205 is, as shown inFIG. 31A , comprised ofsplits 251 to 254, in which an outer circumferential diameter of cylinder changed in a tapered shape in an axial direction are divided into four parts in a circumferential direction. As shown inFIG. 31B , an inner circumferential surface of each split 251 to 254 is provided in small-diameter portions 251 b to 254 b in which a large-diameter side of the outer circumferential surface is formed in the large-diameter portions 251 a to 254 a corresponding to the outside of the nut blank 201, and a small-diameter side of an outer circumferential surface is formed in the small-diameter portions 251 b to 254 b slightly larger than the inner diameter (smaller than the outside) of thenut blank 201. - Thereby, at a boundary surface of the large-
diameter portions 251 a to 254 a and the small-diameter portions 251 b to 254 b, restrainingsurfaces 251 c to 254 c are formed, which bring into contact with anupper end surface 214 of thenut blank 201. On these restrainingsurfaces 251 c to 254 c (a recess 253 d is not shown inFIG. 31B ), recesses 251 d to 254 d are formed. The large-diameter portions 251 a to 254 a of the inner circumferential surface of each split 251 to 254 correspond to the inner circumferential surface to which the outercircumferential surface 213 of thenut blank 201 is received. - The
stand 204 has, as shown inFIG. 31C , a concave 241 having the same inner diameter as thenut blank 201 is formed on the center of theupper surface 204, and apart of theupper surface 204 a acts as a restraining surface that comes into contact with alower end face 215 of thenut blank 201. On the restraining surface, recesses 242 a to 242 d are formed. InFIG. 31C , because there is shown an aspect in which therecesses 242 a to 242 d are formed so as to be positioned at the inner circumferential surface side of the each split 251 to 254, only therecess 242 b and therecess 242 d are shown, but therecess 242 a and the recess 242 c are not shown. - The
recesses 242 a to 242 d are formed at least on one axial end face of the nut blank 201, i.e. at either of theupper end face 214 or thelower end face 215. In the first example, therecesses 242 a to 242 d have a substantially semispherical shape, and are formed integrally and continuously in a circumferential direction of at least either theupper end face 214 or thelower end face 215. The shape and the number of therecesses 242 a to 242 d are not necessarily limited to such aspect. They may independently be provided in correspondence with the length of an arc in a circumferential direction of the S-shapedconcaves 212A to 212D to be formed on the inner circumferential surface of thenut blank 201. Further, therecesses 242 a to 242 d may be formed identical with one another in area, depth, geometry, etc., or they may individually be different. For example, therecesses 242 a to 242 d formed at a position distant from the S-shapedconcaves 212A to 212D may be small in their area and depth. Conversely, therecesses 242 a to 242 d to be formed at a position proximate to the S-shapedconcaves 212A to 212D may be large in their area and depth. Moreover, irrespective of the number of the S-shaped concave, provision of only one recess may of course be possible. - An
outer member 206 is a cylinder having an outside surface identical with the innercircumferential surface 261 corresponding to the tapered outer circumferential surface of the restrainingmember 205, and with a profile of thestand 204. - The S-shaped
concaves 212A to 212D are formed which define the four ball returning passages on the innercircumferential surface 211 of the nut blank 201 by the following method, using this die. - Firstly, the
nut blank 201 is disposed at the center on thestand 204 to match the innercircumferential surface 211 of the nut blank 201 with the inner circumferential surface of the concave 241. Secondly, each splits 251 to 254 of the restrainingmember 205 are disposed on thestand 204, the large-diameter portions 251 a to 254 a of the inner circumferential surface are brought into contact with the outercircumferential surface 213 of the nut blank 201, and the restraining surfaces 251 c to 254 c are brought into contact with theupper end face 214 of thenut blank 201. Then, theouter member 206 is disposed on thestand 204, and the innercircumferential surface 261 is brought into contact with the tapered outer circumferential surface of the restrainingmember 205. At this instance, theouter member 206 is fixed to thestand 204. - Thereby, a movement toward the outside in a radial direction of
splits 251 to 254 constituting the restrainingmember 205 is restrained. The restrainingmember 205 and thestand 204 put into a state where the both end faces 214 and 215 in an axial direction of the nut blank 201 are restrained. - Subsequently, the
cam sliders 203A to 203D are inserted into the nut blank 201 toward the innercircumferential surface 211 of thenut blank 201. Thereby, the fourslopes 233 of thecam sliders 203A to 203D creates a space into which thecam driver 202 is inserted. Then, an end of the body of thecam driver 202 is inserted into the space.FIG. 29A shows this state. - When pressing the
cam driver 202 from above by applying pressing pressure a force is transmitted from the slantedslopes 222 a to 222 d of thecam driver 202 to theslope 233 of thecam sliders 203A to 203D. Accompanying thereto, a downward force of thecam driver 202 is converted into a force radially moving outward eachcam slider 203A to 203D, and the S-shapedconvexes 235A to 235D provided in the eachcam slider 203A to 203D press the innercircumferential surface 211 of the nut blank 201 to cause it t be subject to plastic deformation. Accompanying thereto, materials existing on the outercircumferential surface 213 of the nut blank 201 are pushed into therecesses 251 a to 251 d of thesplits 251 to 254 constituting the restrainingmember 205 and into therecesses 242 a to 242 d of thestand 204.FIG. 29B shows this state. - This forms S-shaped
concaves 212A to 212D constituting the four ball returning passages on the innercircumferential surface 211 of thenut blank 201. An excess material produced with the formation of the S-shapedconcaves 212A to 212D move into therecesses 251 d to 254 d of thesplits 251 to 254 constituting the restrainingmember 205 from an upper end of the nut blank 201, andconvexes 214A to 214D are provided thereby. Furthermore, excess material produced with the formation of the S-shapedconcaves 212A to 212D moves into therecesses 242 a to 242 d of thestand 204 from alower end 215 of the nut blank 201, and theconvexes 215A to 215D are provided thereby. Hereinafter, in some case, theseconvexes 214A to 214D and convexes 215A to 215D may possibly be called as an end face convex. - Here, it is preferable for a die at the outside side of the nut blank 201 to be one which relatively firmly fastens the outside of the
nut blank 201. For example, it is preferable that fitting of the outside of the die and the nut blank 201 range from loose fit of several micrometers to interference fit of tens of micrometers. Since with plastic working using such method, expansion of the excess material to the outside of the nut blank 201 can be suppressed, it enables plastic working of the S-shapedconcaves 212A to 212D, without impacting on accuracy of the outside dimensions, etc. - It is noted that where the formation of a projection at the outside side of the
nut blank 201 is allowed for, it is also possible to use at the same time the recess formed at the outer diameter side and the recess formed at the end face side. - The nut blank 209 in which the S-shaped
concaves 212A to 212D, theconvexes 214A to 214D, and theconvexes 215A to 215D are formed by this method is shown inFIG. 32 .FIG. 32A is a front view;FIG. 32B is a cross-sectional view taken along a line A-A thereof; andFIG. 32C is a perspective view. By forming a spiral groove and a seal attaching groove in the nut blank 201, the ball screw nut is manufactured. - Herein, as shown in
FIGS. 32B and 32C , on oneend face 215 of the nut blank 201, anotch 216 is formed for positioning during forging of the nut blank 210 and subsequent cutting. In the first example, a convex (not shown) to be fitted to or to be engaged into may be provided in thestand 204 and the restrainingmember 205 for preventing that the excess material does not move into thenotch 216 during plastic working to thenut blank 201. - Further, the sum of volume of the convex parts of the
convexes 214A to 214D and theconvexes 215A to 215D is substantially identical with that of the concave of the S-shapedrecesses 212A to 212D. - With the method according to the first example, the end face convex can be manufactured simultaneously with the S-shaped concave. Also, the method minimizes an effect of the material flowing to the periphery of the nut, caused by forging. Even when a nut having long dimensions in an axial direction and a small inner diameter is manufactured, simultaneous formation of the four S-shaped
concaves 212A to 212D in the nut blank 201 may be possible, without giving damage to thecam driver 202. Adhesion between the nut and housing, which may be caused when the nut moves in an axial direction and an end face of the nut collides against the housing, etc., can be prevented by providing an end face concave and making a collision area small between the nut and the housing, etc. Further, according to the first example, it does not impair plane accuracy of portions other than the convex of the nut end face. -
FIG. 33 is a cross-sectional view showing a second example of the manufacturing method of the ball screw of a fifth embodiment. In this connection, the second example is the same as the above-mentioned first example, with the exception that a location where the recess of the splits and the recess of the stand are formed is changed. Thus, the descriptions of the same configurations having the same reference numerals with those of the first example will be omitted for brevity's sake. As shown inFIG. 33 , the second example illustrates one example of arrangement of the recess where plastic working (e.g. cold forging) is applied to the nut blank 201 in which theflange 207 is provided. - In the nut blank 201, where a thick wall part of the
flange 207 and a phase of the S-shapedconcaves 212A to 212D in an axial direction are overlapped, there is some possibility of exerting a bad influence even on geometry, etc., of the S-shapedconcaves 212A to 212D to be worked, due to hindrance by the thick wall part and insufficient plastic deformation resulting therefrom, even by forming the recess on the outer diameter side. In addition, where the flow of the material is unsuccessfully ended and a thin wall part (inFIG. 33 , a portion at which the flange in an axial direction does not have overlapping phase each other) exists, it is thinkable that dimensional accuracy of an internal diameter of the thin wall part could drop. - To address this potential adverse effect, in the second example, a
recess 242 a corresponding to the S-shapedconcaves 212A to 212D of which phase overlaps with theflange 207 in an axial direction is provided in thestand 204 facing theend face 207 a of theflange 207. On the contrary, a concave of which phase does not overlap in an axial direction with theflange 207 may be provided at end faces (restraining surfaces) 251 c to 254 c at the opposite side to theflange 207, or provided, as shown inFIG. 33 , at a position corresponding to the S-shapedconcaves 212A to 212D of the large-diameter portions 251 a to 254 a facing the external diameter of thenut blank 201. - Here, in the second example, when A is “a distance in an axial direction between the S-shaped concave nearest to an end face at the side where the end face convex is provided and an axial end face at the side where the end face convex is provided”, and B is “a distance in a radial direction between the S-shaped concave and the outermost circumferential surface of the nut blank”, it is preferable to set to be A<B. By defining like this, notably, the nut blank with the
flange 207, the projection is liable to project, which mitigates an impact on the external diameter side of thenut blank 201. - According to the second example, even where the thick wall part such as the
flange 207 etc., is provided in the nut blank 201, the nut on an end face of which the projection is formed may be provided, while suppressing an adverse effect on another portion of thenut blank 201. In this connection, area, depth, position in a circumferential direction of the projection, etc. may be properly set at discretion as with the first example. -
FIG. 34 is a cross-sectional view showing a third example of the manufacturing method of the ball screw of the fifth embodiment. As the third example is the same as the above-mentioned first example, with the exception that a construction of the stand. Therefore, the descriptions of the same construction denoted by the same reference numerals are omitted for simplification. - As shown in
FIG. 34 , in the third example, thestand 204 that is a part of the die is made of pressure resistant rubber and is devoid of the concave 241 having the same inner diameter as that of thenut blank 201. That is so say, thestand 204 is made softer than an upper pressing member (metal), and is permitted to undergo somewhat of elastic deformation. Put differently, a pressing force to an end face is reduced than that to the outer circumferential surface of thenut blank 201. Thus, the excess material to flow by working of the S-shaped concave tends to more protrude over alower end face 215 of the nut blank 201 that is likely to be elastically deformed. As a consequence, a different-sized convex may be provided which is a result of protruding of the excess material over the both end faces 214 and 215 in an axial direction of thenut blank 201. This prevents adhesion when an end face of the nut at the side where the end face is not planar and the housing, etc., collide against each other, as at least either of theupper end face 214 or thelower end face 215 of thenut blank 201 is not flat after forging. - Here, whether what shape of the end face convex should be taken is not limited to the convex as exemplified in the first and the second examples, rather an end face of the nut having an undulated shape may be included.
- Moreover, as a candidate of the pressure resistant rubber, materials that may resist compression under high pressure are desirable. A variety of synthetic rubber, such as urethane rubber, nitrile rubber, acrylic rubber, fluorine rubber, and acrylonitrile-butadiene rubber may preferably be used for this purpose.
- In the event of fear of frictional wear to the pressure resistant rubber, arising from direct abutment of the
stand 204 made of the pressure resistant rubber and the nut blank 201, thelower end face 215 of the nut blank 201 may be received through elastic members such as rubber, spring, etc. -
FIG. 35 is a cross-sectional view showing a fourth example of the manufacturing method of the ball screw of the fifth embodiment. As the fourth example is the same as the above-mentioned second example, with the exception that a recess is formed in the nut blank, and so its description of the same construction denoted by the same reference numeral is omitted for brevity's sake. - As shown in
FIG. 35 , in the fourth example, a concave 207 b is formed at anend face 207 a of theflange 207, which is used when plastic working is applied to the nut blank 201 in which theflange 207 is provided. Thereby, since the excess material flows to therecess 207 b, without forming therecesses 242 a to 242 d in thestand 204, it preferably enables working of the S-shapedconcaves 212A to 212D. - Herein, in the fourth example, the
lower end face 215 of the nut blank 201 may not be plane after forging. That is, where volume of therecess 207 b is different from that of the S-shaped concaves 211A to 212D, the formation of a recess or a convex at a position of therecess 207 b contributes to reduce a colliding area of the nut and the housing. This prevents the occurrence of adhesion between the nut and the housing. -
FIGS. 36 and 37 are a cross-sectional view showing a fifth example of the manufacturing method of the ball screw of the fifth embodiment. As shown inFIG. 36 , previously providing a concave 196 on a member which faces an axial end face of thenut blank 101 and restrains the axial end face simultaneously attains by cold forging the formation of the concave 197 on the innercircumferential surface 111 of thenut blank 101 and the formation of theprojection 198 on the end face in an axial direction of the nut blank 101, in the exactly same way as the example shown inFIG. 28 . - Further, as shown in
FIG. 37 , where the member facing the end face in an axial direction of thenut blank 101 does not restrain the end face in an axial direction, because the member and the end face in an axial direction of the nut blank 101 are apart from each other, it allows by cold forging the simultaneous formation of the concave 197 on the innercircumferential surface 111 of thenut blank 101 and the formation of theprojection 198 on the end face in an axial direction of the nut blank 101, in the exactly same way as the example shown inFIG. 28 , even without the formation of thegroove 196 in the member. - An explanation will then made below to the ball screw utilizing the nut manufactured in the first and the fourth examples by referring to drawings.
FIG. 38 is a view showing one exemplary construction of the ball screw of the fifth embodiment; in whichFIG. 28A is a cross-sectional view, andFIG. 38B is a perspective view. As shown inFIG. 38A , theball screw 302 includes: anut 305 rotatably supported via abearing 304 in a large-diameter hole 303 b communicating with a central opening of thehousing 303 in which acentral opening 303 a is formed as a fixed portion; ascrew shaft 306 to be screwed with thenut 305; and a large number ofballs 307 loaded between thenut 305 and thescrew shaft 306. - The
nut 305 is manufactured by any of the methods disclosed in the foregoing first to fourth examples. To put it concretely, thenut 305 is made of acylindrical member 305 b on inner circumferential surface of which ascrew groove 305 a is formed. One end of an outer circumferential surface of thecylindrical member 305 b is rotatably supported via thebearing 304 by thehousing 303, and aspur gear 305 c is fitted onto the other end. Aspur gear 305 c is meshed with thespur gear 305 d, which is coupled to a rotation axis of the electric motor as a rotary driving source (not shown), and thenut 305 is rotationally driven by a turning force of the electric motor. - Moreover, in the
nut 305, a cylindricalabutting piece 310 is axially provided in a projecting manner, as a abutting member, which is abutted to an end face in a circumferential direction of aguide projection 306 e of thescrew shaft 306 to be mentioned later, at a more outside position in a radial direction than thescrew groove 305 a on aside end face 305 e in an axial direction at thespur gear 305 c side. - The abutting
piece 310 is a convex provided on the end face 214 (215) of the nut blank 201 in the forgoing first to fourth examples. A circulating groove (not shown) is the S-shapedconcaves 212A to 212D formed in the first to fourth examples. Further, thescrew groove 305 a is one which is formed by cutting, etc. Incidentally, as the abuttingpiece 310 is the convex provided on the end face 214 (215) of the nut blank 201 in the foregoing first to fourth examples, the total volume of these projections is virtually identical with that of a concave of the S-shapedrecesses 212A to 212D (not shown). - The
screw shaft 306 is being inserted into acentral opening 303 a formed in the protrusion housing, and includes: a large-diameter portion 306 b on the outer circumferential surface of which ascrew groove 306 a is formed; asquare tube 306 d fitted to aprism 306 c provided at one end of the large-diameter portion 306 b; aguide projection 306 e outwardly projecting from its one plane than the large-diameter portion 306 b in a radial direction; and a small-diameter shaft 306 f connected to theprism 306 c. - Here, at the end where the
nut 305 of thehousing 303 is received, a fixingcover 309 is integrally fixed by a fixing member such as bolting, as a fixed portion, made by die-casting e.g. of aluminum, aluminum alloy, etc. that is used for forming a receiving portion 309 a to receive therein thenut 305. In the fixingcover 309, an insertinghole 309 b is formed, which has a diameter smaller than that of thecentral opening 303 a of thehousing 303 into which the small-diameter shaft 306 f and the large-diameter portion 306 b of thescrew shaft 306 are inserted, and has a diameter larger than the large-diameter portion 306 b of thescrew shaft 306. Aguide groove 309 c to guide aguide projection 306 e of thescrew shaft 306 is formed at the inner circumferential surface side of aninsertion hole 309 b. Theguide groove 309 c is opened to the receiving portion 309 a side, and at the opposite side to the receiving portion 309 a side, astopper 309 d is provided to which theguide projection 306 e abuts without opening. - As shown in
FIG. 38B , suppose that theabutting piece 310 of thenut 305 is abutted to an end face in a circumferential direction of theguide projection 306 e of thescrew shaft 306, and is at the stroke ends in a radial direction, as shown inFIG. 38A , and that about a half theguide projection 306 e in an axial direction is engaged, in this state, into theguide groove 309 c of the fixingcover 309. - By rotating from this state the
nut 305 in a direction indicated by an arrow A, the abuttingpiece 310 separates in a circumferential direction from the guide protrusion 310 c with the rotation of thenut 305. At the same time, as theguide projection 306 e is engaged into theguide groove 309 c of the fixingcover 309 to stop the rotation of thescrew shaft 306, thescrew shaft 306 advances in an axial direction and theguide projection 306 e advances concurrently therewith. - After that, the
nut 305 continues to rotate, and when an end face at the small-diameter shaft 306 f side of theguide projection 306 e of thescrew shaft 306 abuts to thestopper 309 d of the fixingcover 309, the advance of thescrew shaft 306 stops and reaches the forward stroke end. - When the
nut 305 is reversely rotated in an opposite direction counter to an arrow A shown inFIG. 38B , from a state where thescrew shaft 306 reached the forward stroke end, thescrew shaft 306 is subject not to rotate and retreats in an axial direction, as theguide projection 306 e of thescrew shaft 306 is engaged into theguide groove 309 c of the fixingcover 309, with the reverse rotation of thenut 305. - When the
guide projection 306 e of thescrew shaft 306 reaches a position (one turn short of the stroke end) facing the abuttingpiece 310 of thenut 305, a reverse rotation of thenut 305 is allowed. - On that account, the
screw shaft 306 further retreats and a back end of theguide projection 306 e enters a raceway at an end of theabutting piece 310 provided in thenut 305. Finally, as shown inFIG. 38B , the abuttingpiece 310 abuts an end face in a circumferential direction ofguide projection 306 e. In this situation, as shown inFIG. 38A , as about a half the axial length of theguide projection 306 e is engaged into theguide groove 309 c i.e. in a non-rotating state, and theabutting piece 310 abuts theguide projection 306 e with the predetermined abutting length, the abuttingpiece 310 is abutted to theguide projection 306 e to restrain a further reverse rotation of thenut 305, and thescrew shaft 306 reaches the backward stroke end. - In this way, at the stroke end toward the
nut 305 side of thescrew shaft 306, the abuttingpiece 310 provided in thenut 305 is abutted to theguide projection 306 e having a rotation stopper capability of thescrew shaft 306, to thereby exhibit the rotation stopper capability. Additionally, by forming theguide projection 306 e using the aforementioned method, a metal flow (fiber flow) is hardly cut and subject to work hardening, which offers theguide projection 306 e with high strength. - Accordingly, the
guide projection 306 e may have the both rotation stopper and stopper capabilities, which eliminate the need for providing the stopper capability with another member. This simplifies a construction as well as reduces parts count, thereby reducing the product cost. - When the
screw shaft 306 reaches the stroke end, theguide projection 306 e of thescrew shaft 306 is engaged into theguide groove 309 c, and theabutting piece 310 is abutted to the projection projecting from theguide groove 309 c. Because of this, when input torque to be transmitted to thenut 305 is transmitted via the abuttingpiece 310 to theguide projection 306 e, the transmitted torque is received via theguide projection 306 e in theguide groove 309 c, as theguide projection 306 e itself is engaged into theguide groove 309 c. This securely prevents the radial load actions upon thescrew shaft 306 and thenut 305. - An explanation will next be made to another example of the ball screw of the fifth embodiment by referring to drawings.
FIG. 39 is a perspective view showing another construction of the ball screw of the fifth embodiment. As the ball screw disclosed in the example is the same as the abovementioned ball screw, with the exception that a convex (abutting portion) is provided on an end face in an axial direction of the nut is worked, its description of the same construction denoted by the same reference numeral is omitted for brevity's sake. - As shown in
FIG. 39 , in this example, the abutting member is configured of a spiral slope and a abutting surface, in place of the abutting piece. Namely, the abutting member to be provided on an end face at thespur gear 305 c side of thenut 305 includes aspiral slope 312 and aabutting surface 313 manufactured by applying any of cutting, grinding, or plastic working to a convex provided on an end face in an axial direction of the nut. - The
spiral slope 312 is formed so that a projecting length in an axial direction gradually gets longer as it goes toward a circumferential direction in a counterclockwise direction from astart edge 312 a, which takes up a predetermined width at the inner circumferential side in a radial direction from one point of an outer circumferential line on theside end face 305 e at thespur gear 305 c side of thenut 305. Further, the abuttingsurface 313 is abutted on an end face in a circumferential direction of theguide projection 306 e of thescrew shaft 306 provided by axially extending from alongest projection 312 b facing thestart edge 312 a of thespiral slope 312 toward thestart edge 312 a. - With this construction, as shown in
FIG. 39 , by rotating thenut 305 in a direction indicated by an arrow A in which theabutting surface 313 is abutted to an end face in a circumferential direction of theguide projection 306 e, from a state where thescrew shaft 306 is at the backward stroke end, the abuttingsurface 313 of thespiral slope 312 separates in a circumferential direction from theguide projection 306 e with the rotation of thenut 305. At the same time, thescrew shaft 306 advances in an axial direction and theguide projection 306 e also advances, as theguide projection 306 e is engaged with theguide groove 309 c of the fixingcover 309, and thescrew shaft 306 is subject not to rotate. - After one rotation of the
nut 305, the lockingsurface 313 of thenut 305 is separated from a back end of theguide projection 306 e, which avoids theabutting surface 313 from abutting to the end face in a circumferential direction of theguide projection 306 e. - Subsequently, the
nut 305 continues to rotate, and when an end face at the small-diameter shaft 306 f side of theguide projection 306 e of thescrew shaft 306 abuts to the stopper 309 e of the fixingcover 309, the advance of thescrew shaft 306 is stopped and reaches the forward stroke end. - When the
nut 305 is reversely rotated in an opposite direction to a direction indicated by an arrow A from a state where thescrew shaft 306 reached the forward stroke end, thescrew shaft 306 is subject not to rotate and retreats in an axial direction, as theguide projection 306 e of thescrew shaft 306 is engaged into theguide groove 309 c of the fixingcover 309 with the reverse rotation of thenut 305. - Then, when the
guide projection 306 e of thescrew shaft 306 reaches a position (one turn short of the stroke end) facing the abuttingsurface 313 of thenut 305, as mentioned previously, the reverse rotation of thenut 305 is allowed. - For this reason, the
screw shaft 306 further retreats and a back end of theguide projection 306 e enters in a raceway of thelongest projection 312 b provided in thenut 305. Finally, as shown inFIG. 39 , the abuttingsurface 313 abuts an end face in a circumferential direction of theguide projection 306 e. In this state, as with the aforesaid example, because about half of the axial length of theguide projection 306 e is engaged into theguide groove 309 c, theguide projection 306 e is in a non-rotating state. As theabutting surface 313 abuts to theguide projection 306 e, the abuttingsurface 313 is abutted to theguide projection 306 e to restrain a further reverse rotation of thenut 305, and thescrew shaft 306 reaches the backward stroke end. - In this manner, also in this example, at the stroke end to the
nut 305 side of thescrew shaft 306, the abuttingsurface 313 of thespiral slope 312 provided in thenut 305 is abutted to theguide projection 306 e having a rotation stopper capability, to thereby exhibit a stopper capability. - Hence, the
guide projection 306 e may have both the rotation stopper and stopper capabilities, which eliminates the need for providing the stopper capability by use of another member. This simplifies the construction as well as reduces product counts, thereby reducing the product cost. - Here, the concave 242 a of the
stand 204 may have the substantially same shape as the spiral slope (abutting portion) by using the method shown inFIGS. 29 and 33 , and may be manufactured simultaneously with the circulating groove by forging. - Further, whereas the geometry of the ball screw in the example of the ball screw shown in
FIGS. 38 and 39 is one which shows a case where the nut rotates (case where the nut does not move in an axial direction of the screw shaft), it may be valid for an aspect that a screw shaft of the ball screw where a convex is provided on an end face of the nut rotates, and the nut moves in an axial direction. - As described above, although the explanation has been made to the examples of the ball screw nut which is manufactured by the manufacturing method of the ball screw nut and the ball screw nut manufactured thereby according to the fifth embodiment, the fifth embodiment is not necessarily limited to the above examples, as long as the fifth embodiment is at least a ball screw nut in which a convex is provided at least on an end face in an axial direction of the nut and a manufacturing method thereof. It should be understood that various modifications of the fifth embodiment may be possible, as far as they do not deviate from the spirit of the fifth embodiment.
- For example, the manufacturing method of the ball screw nut according to the fifth embodiment, and the nut of the ball screw manufactured thereby may equally be applied to a ball screw nut that adopts a circulating screw shaft. Further, in the above example, while the example is given where the plurality of S-shaped concaves are simultaneously provided by plastic working on the inner circumferential surface of the nut blank, the plurality of S-shaped concaves may consecutively be provided.
- Also, as plastic working of the S-shaped
concaves 212A to 212D in the fifth example, a variety of plastic working such as hot forging, cold forging, hydro forming, etc, may be applied. - The sixth embodiment is directed to a ball screw in which balls are loaded between the ball screw shaft and the ball screw nut, in particular, to be suited for a ball screw in which a concave, serving as the circulating groove, is formed on an inner circumferential surface of the ball screw nut.
- The ball screw allows a smoother rotational-linear motion by rolling the balls, by forms a male ball screw groove in the ball screw shaft, by forming a female ball screw groove in the ball screw nut, and by loading balls between these male and female ball screw grooves. In utilizing such a ball screw, Patent Document 4 discloses e.g. press fitting a rolling bearing on an outer circumferential surface of the ball screw nut.
- However, in general ball screw, it needs so-called, a ball returning passage to return balls of the ball screw nut from a rolling endpoint to a rolling start point of the ball screw nut along a female ball screw groove. The ball returning passage is formed of separate ball returning members inserted from the outer circumferential surface of the ball screw nut to the inner circumferential surface of the ball screw nut in which the female ball screw groove is formed. That is, a through hole to circulate the balls is formed in the nut, and when rolling bearing is press fitted to the ball screw nut in which the through hole is formed in an open manner, compressive stress to the ball screw nut becomes uneven in a circumferential direction with the press fitting. For example, there is some probability of affecting to the inner circumferential surface of the ball screw nut, i.e. circularity of the female ball screw groove.
- The sixth embodiment focuses on the above-identified problems, and its object is to provide a ball screw in which a compressive stress of the ball screw nut with press fitting is liable to be equal in a circumferential direction, even when a nut fitted member is press fitted onto the ball screw nut.
- In order to solve the above-identified problems, the ball screw of the sixth embodiment includes: balls that are rolling elements; a ball screw shaft having on its outer circumferential surface a male ball screw groove, as a rolling groove into which the balls are loaded; a ball screw nut which has on its outer circumferential surface a female ball screw groove, as a rolling groove, into which the balls are loaded, is fitted onto the ball screw shaft, and of which outer circumferential surface are in a non-through state; a nut fitted member fitted by press fitting onto the outer circumferential surface of the ball screw nut.
- Further, interference by press fitting of the nut fitted member and the ball screw nut exceeds 0.02% of the external dimensions of the outer circumferential surface of the nut onto which the nut fitted member is fitted.
- Furthermore, interference by press fitting of the nut fitted member and the ball screw nut exceeds 0.02% and less than 0.16% of the external dimensions of the outer circumferential surface of the ball screw nut onto which the fitted member is fitted.
- When the nut fitted member is press fitted in the nut, shrink fitting is used which heats the nut fitted member to fit onto the nut.
- Further, a circulating groove constituting the ball returning passage is formed on the inner circumferential surface of the ball screw nut.
- Furthermore, the nut fitted member is any one of a sleeve, a rolling bearing, and a gear wheel, each having a cylindrical inner circumferential surface, or a combination of them.
- According to the ball screw nut according to the sixth embodiment, the nut fitted member is fitted by press fitting onto the outer circumferential surface of the ball screw nut that is fitted onto the ball screw shaft. The inner circumferential surface and the outer circumferential surface of the ball screw nut are in a non-through state. Thus, it is easy to secure the nut fitted member, as well as compressive stress of the ball screw nut with press fitting of the nut fitted member is liable to be equal in a circumferential direction. Moreover, an appropriate compressive force may be applied to the inner circumferential surface of the ball screw nut i.e. to the female ball screw groove, which improves the durability of rolling fatigue of the female ball screw groove of the ball screw nut.
- Since the interference by press fitting of the nut fitted member and the ball screw nut exceeds 0.02% of the external dimensions of the outer circumferential surface of the ball screw nut to be fitted onto the nut fitted member, it enables fixing of the nut fitted member by press fitting on the outer circumferential surface of the ball screw nut. Further, as the interference between the nut fitted member and the ball screw nut by press fitting exceeds 0.02% and less than 0.16%, it enables fixing of the nut fitted member by press fitting onto the outer circumferential surface of the ball screw nut, as well as rendering a compressive stress produced in the ball screw nut and the nut fitted member to be a proper one.
- Where the nut fitted member is press fitted in the ball screw nut, the increased interference of the nut fitted member and the ball screw nut can be made larger, as shrink fitting is adopted to heat the nut fitted member and to fit it onto the ball screw nut.
- Moreover, since the circulating groove constituting the ball returning passage is formed on the inner circumferential surface of the ball screw nut, the inner circumferential surface and the outer circumferential surface of the ball screw nut is liable to be in a non-piercing through state, which easily improves the circularity of the outer circumferential surface of the ball screw nut onto which the nut fitted member is press fitted.
- Further, the nut fitted member made of any of a sleeve, a bearing, a gear, each having a cylindrical inner circumferential surface, or combination thereof facilitates the practice of the invention.
- An explanation will next be made to an example of the ball screw of a sixth embodiment by referring to drawings.
-
FIG. 40 is a longitudinal sectional view showing a first example of the ball screw of the sixth embodiment. -
Reference Numeral 401 inFIG. 40 denotes a ball screw shaft. Aball screw nut 402 is fitted onto theball screw shaft 401. On an outercircumferential surface 403 of theball screw shaft 401, a maleball screw groove 404 is formed. Also, on an innercircumferential surface 405 of theball screw nut 402, a femaleball screw groove 406 is formed. Multiple balls are loaded between the maleball screw groove 404 and the femaleball screw groove 406. - Thus, for example, when the
ball screw shaft 401 or theball screw nut 402 rotates, theballs 407 roll in the maleball screw groove 404 and the femaleball screw groove 406. Accompanying thereto, theball screw nut 402 or theball screw shaft 401 linearly moves. This achieves a smooth rotational-linear motion. - Moreover, in the first example, as is disclosed in
Patent Document 3 proposed earlier by the applicant of this invention, a circulatinggroove 408 constituting the ball returning passage is directly formed by plastic forming on the innercircumferential surface 405 of theball screw nut 402. The circulatinggroove 408 is configured of the S-shaped concave formed on the innercircumferential surface 405 of theball screw nut 402. Accordingly, in the first example, the inner circumferential surface and the outer circumferential surface of theball screw nut 402 can be put in a non-through state. - Then, in the first example, on a part of the outer circumferential surface of the
ball screw nut 402, an outercircumferential surface 409 having high circularity is formed, e.g. by grinding, and in addition, anabutting end face 410 is formed to be adjacent to the outercircumferential surface 409. A rollingbearing 411 is fitted onto the outercircumferential surface 409 as a nut fitted member by press fitting, and positioning is done by abutting an end face of the rollingbearing 411 to theabutting end face 410. An inner circumferential surface of the inner ring of the rollingbearing 411 is typically finished to have high circularity. Therefore, if the circularity of the outercircumferential surface 409 of theball screw nut 402 is high, the rollingbearing 411 can be press fitted closely in theball screw nut 402. - In this instance, because the inner
circumferential surface 405 and the outercircumferential surface 409 of theball screw nut 402 are in a non-through state, a compressive stress of theball screw nut 402 is liable to be equal in a circumferential direction with the press fitting of the rollingbearing 411. In particular, if the circularity of the outercircumferential surface 409 of theball screw nut 402 is high, the compressive stress of theball screw nut 402 is roughly equal in a circumferential direction with the press fitting of the rollingbearing 411, as the circularity of the inner circumferential surface of the inner ring of the rollingbearing 411 is high as stated above. - The circularity of the inner circumferential surface of the inner ring of the rolling
bearing 411 that is the nut fitted member and that of the outercircumferential surface 409 of theball screw nut 402 shall be both less than or equal to 10 μm, preferably, be less than or equal to 5 μm, and more preferably be less than or equal to 1 μm. Further, preferably, surface roughness of the inner circumferential surface of an inner ring of the rollingbearing 411 that is the nut fitted member and surface roughness of the outer circumferential surface of theball screw nut 402 are less than or equal to 3 μmRa, and more preferably be less than or equal to 1 μmRa. - In this way, in the ball screw of the first example, by fitting the rolling
bearing 411 that is the nut fitted member onto the outercircumferential surface 409 of theball screw nut 402 by press fitting, which is fitted by press fitting onto theball screw shaft 401 and of which innercircumferential surface 405 and outer circumferential surface are in a non-through state, it is easy to fix the rolling bearing, as well as compressive stress of theball screw nut 402 is liable to be equal with the press fitting of the rollingbearing 411. Moreover, an appropriate compressive stress may be applied to the innercircumferential surface 405 of theball screw nut 402, i.e. to the femaleball screw groove 406. This improves durability of rolling fatigue of the femaleball screw groove 406 of theball screw nut 402. - Further, if the interference of the rolling
bearing 411 that is the nut fitted member and theball screw nut 402 by press fitting exceeds 0.02% of the external dimensions of the outercircumferential surface 409 of theball screw nut 402 to be fitted onto the rolling beating 411, the rollingbearing 411 can more firmly be fixed by press fitting to the outercircumferential surface 409 of theball screw nut 402. Furthermore, if the interference between the rollingbearing 411 that is the nut fitted member and theball screw nut 402 by press fitting is less than 0.16% of the external dimensions of the outercircumferential surface 409 of theball screw nut 402 to be fitted onto the rollingbearing 411, compressive stress produced in theball screw nut 402 and the rollingbearing 411 can be made more appropriate. However, when the interference exceeds 0.16%, an excessive tensile stress is liable to be developed in the inner ring of the rollingbearing 411, and thus it is not desirable, as it is very likely to produce a crack in the inner ring. - Preferably, the interference of the rolling
bearing 411 that is the nut fitted member and theball screw nut 402 by press fitting is within a range from 0.05% to 0.15% of the external dimensions of the outercircumferential surface 409 of theball screw nut 402 to be fitted onto the rollingbeating 411. Additionally, it is preferable that when load to be applied to the rolling beating 411 that is the nut fitted member or theball screw nut 402 is heavy, the interference is within a range from 0.08% to 0.15% of the external dimensions of the outercircumferential surface 409 of theball screw nut 402 to be fitted onto the rollingbearing 411. - Assuming that the circulating
groove 408 constituting the ball returning passage is formed on the innercircumferential surface 405 of theball screw nut 402, the innercircumferential surface 405 and the outer circumferential surface of theball screw nut 402 is liable to be in a non-through state. This easily improves circularity of the outercircumferential surface 409 of theball screw nut 402 onto which the rolling bearing 411 that is the nut fitted member is press fitted. What is more, the rollingbearing 411 may be press fitted to a position corresponding to the circulatinggroove 408. -
FIG. 41 is a longitudinal sectional view showing a second example of the ball screw of a sixth embodiment. As a lower half of longitudinal section is symmetric with an upper half thereof, and so its illustration is omitted for brevity's sake. Further, as the construction of the ball screw per se is the same as that in the first example shown inFIG. 40 , the same construction is denoted by the same reference numeral, and thus its detailed description is omitted for simplification. - In the second example, as with the first example, the rolling
bearing 411 is used for the nut fitted member, the outercircumferential surface 409 for press fitting the rollingbearing 411 is manufactured at the both ends in an axial direction of theball screw nut 402 with high circularity by cutting process or the like, and aabutting end face 411 is adjacently formed at the inside in an axial direction of these outer circumferential surfaces 409. Then, the rollingbearing 411 is press fitted onto the respective outercircumferential surfaces 409 from the outside in an axial direction. - The details of the circularity, surface roughness, and interference of the both when the rolling
bearing 411 that is the nut fitted member is press fitted onto the outer circumferential surface of theball screw nut 402 are the same as those in the first example. It is noted that when the rollingbearing 411 is press fitted onto the outercircumferential surface 409 of theball screw nut 402, different parameters of these rollingbearings 411 may be taken. Also, the rollingbearing 411 may employ various bearings, such as a roller bearing, apart from the illustrated ball bearing. -
FIG. 42 is a longitudinal sectional view showing a third example of the ball bearing of the sixth embodiment. As a lower half of the longitudinal section is symmetric with an upper half thereof, and so its illustration is omitted for brevity's sake. Further, as the construction of the ball screw per se is the same as that in the first example shown inFIG. 40 , the same construction is denoted by the same reference numeral, and thus its detailed description is omitted for simplification. - In the third example, a
sleeve 412 is used for the nut fitted member. Here, assume that an innercircumferential surface 413 of thesleeve 412 has the same diameter throughout the length in an axial direction, and that an outercircumferential surface 409 of theball screw nut 402 onto which the innercircumferential surface 413 of thesleeve 412 is fitted also has the same diameter throughout the length in an axial direction. The outercircumferential surface 409 for press fitting thesleeve 412 is formed by grinding, etc., with high circularity throughout the length in an axial direction of theball screw nut 402, the innercircumferential surface 413 of thesleeve 412 is also formed by grinding with high circularity, and thesleeve 412 is press fitted onto the outercircumferential surface 409 of theball screw nut 402 from one side in an axial direction. - When the
sleeve 412 that is the nut fitted member is press fitted into the outercircumferential surface 409 of theball screw nut 402, the details of the circularity, surface roughness, and interference of thesleeve 412 and the outercircumferential surface 409 are the same as those of the rollingbearing 411 in the first example. Where thesleeve 412 is press fitted onto the outercircumferential surface 409 of theball screw nut 402, as the nut fitted member, the thickness of theball screw nut 402 may be thinned as an outer circumference of theball screw nut 402 may be reinforced with thesleeve 412. In addition to this, if it succeeds in thinning the thickness of theball screw nut 402, it has the merit of facilitating plastic working of the circulatinggroove 408 formed, e.g. of the S-shaped concave. - When the
sleeve 412 that is the nut fitted member is press fitted in theball screw nut 402, adopting shrinkage fitting in which thesleeve 412 is fitted onto theball screw nut 402 after heating thesleeve 412 to expand an inner diameter thereof brings about increased interference by press fitting of the both. -
FIG. 43 is a longitudinal sectional view showing a fourth example of the ball screw of the sixth embodiment. As a lower half of longitudinal section is symmetric with an upper half thereof, and so its illustration is omitted for brevity's sake. Further, as the construction of the ball screw per se is the same as that in the first example shown inFIG. 40 , the same construction is denoted by the same reference numeral, and thus its detailed description is omitted for simplification. - In the fourth example, the
sleeve 412 and the rollingbearing 411 are utilized for the nut fitted member. The innercircumferential surface 413 of thesleeve 412 has the same diameter throughout the length in an axial length matching with the inner circumferential surface of an inner ring of the rollingbearing 411, and that of the outercircumferential surface 409 of theball screw nut 402 onto which an inner ring of the rollingbearing 411 and the innercircumferential surface 413 of thesleeve 412 are fitted has the same diameter throughout the length in an axial direction. The outercircumferential surface 409 for press fitting thesleeve 412 is formed by grinding, etc., with high circularity throughout the length in an axial direction, and the innercircumferential surface 413 of thesleeve 412 is also formed by grinding, etc., with high circularity. Subsequently, thesleeve 412 is press fitted onto the outercircumferential surface 409 of theball screw nut 402 from one side in an axial direction, and the rollingbearing 411 is press fitted onto the outercircumferential surface 409 of theball screw nut 402 from the other side in an axial direction, and an end face of the rollingbearing 411 is abutted to an end face in an axial direction of thesleeve 412. - When the
sleeve 412 that is the nut fitted member is press fitted into the outercircumferential surface 409 of theball screw nut 402, the details of the circularity, surface roughness, and interference of thesleeve 412 and the outercircumferential surface 409 are the same as those of the rollingbearing 411 in the first example. Also, a merit and a press fitting method in a case where thesleeve 412, as a nut fitted member, is press fitted onto the outercircumferential surface 409 of theball screw nut 402 are the same as those in the third example. - Where the circularity, the surface roughness, and the interference associated with the press fitting of the rolling
bearing 411 and theball screw nut 402 are identical with those of thesleeve 412 and theball screw nut 402, compressive stress of theball screw nut 402 where the both are press fitted may be equalized by equalizing the thickness of thesleeve 412 and that of the rollingbearing 411. -
FIG. 44 is a longitudinal sectional view showing a fifth example of the ball screw of the sixth embodiment. As a lower half of longitudinal section is symmetric with an upper half thereof, and so its illustration is omitted for brevity's sake. Further, as the construction of the ball screw per se is the same as that in the first example shown inFIG. 40 , the same construction is denoted by the same reference numeral, and thus its detailed description is omitted for simplification. - In the fifth embodiment, a
gear 414 is used for the nut fitted member. Thegear 414 in the fifth example is one in which teeth are formed throughout the length in an axial direction on the outer circumferential surface of a sleeve-shaped cylinder. It is configured such that the innercircumferential surface 415 of the cylinder of thegear 414 has the same diameter throughout the length in an axial direction, and the outercircumferential surface 409 of theball screw nut 402 onto which the innercircumferential surface 415 of thegear 414 is fitted has the same diameter throughout the length in an axial direction. The outercircumferential surface 409 to press fit thegear 414 is formed by grinding, etc., with high circularity throughout the length in an axial direction of theball screw nut 402, the innercircumferential surface 415 of thegear 414 is also formed by grinding with high circularity, and thegear 414 is press fitted on the outercircumferential surface 409 of theball screw nut 402 from one side in an axial direction. - When the
gear 414 that is the nut fitted member is press fitted into the outercircumferential surface 409 of theball screw nut 402, the details of the circularity, surface roughness, and interference of thegear 414 and the outercircumferential surface 409 are the same as those of the rollingbearing 411 in the first example, when thegear 414 is press fitted onto the outercircumferential surface 409 of theball screw nut 402. In this connection, a spline and a serration may be applied to thegear 414, in addition to the spur gear and a helical gear. -
FIG. 45 is a longitudinal sectional view showing a sixth example of the ball screw of the sixth embodiment. As a lower half of the longitudinal section is symmetric with an upper half thereof, and so its illustration is omitted for brevity's sake. Further, as the construction of the ball screw per se is the same as that in the first example shown inFIG. 40 , the same construction is denoted by the same reference numeral, and thus its detailed description is omitted for simplification. - In the sixth example, as with the foregoing third example, whereas the
sleeve 412 is used for the nut fitted member, in thesleeve 412 of the sixth example, thegear 414 is formed at an end of in an axial direction of the outer circumferential surface of the cylinder. The innercircumferential surface 413 of thesleeve 412 with thegear 414 has the same diameter throughout the length in an axial direction, and the outercircumferential surface 409 of theball screw nut 402 onto which the innercircumferential surface 413 of thesleeve 412 is fitted also has the same diameter throughout the length in an axial direction. Subsequently, the outercircumferential surface 409 for press fitting thesleeve 412 is formed by grinding, etc., with high circularity throughout the length in an axial direction of theball screw nut 402, the innercircumferential surface 413 of thesleeve 412 is also formed by grinding, etc., with high circularity, and thesleeve 412 is press fitted onto the outercircumferential surface 409 of theball screw nut 402 from one side in an axial direction. - The details of the circularity, surface roughness, and interference of the
sleeve 412 that is the nut fitted member and theball screw nut 402 are the same as those of the rollingbearing 411 in the first example, when thesleeve 412 is press fitted onto the outercircumferential surface 409 of theball screw nut 402. In this connection, a spline and a serration may be applied to thegear 414, in addition to a spur gear and a helical gear. - Materials of the
ball screw nut 402 in the aforementioned respective examples, carbon steel, bearing steel, stainless steel, etc., may be applied. Further, similar materials may be applied to the rollingbearing 411, thesleeve 412, and thegear 414 which are press fitted onto theball screw nut 402. Moreover, it is preferable that these members should be hardened by a proper heat treatment at least to a pressed fitted portion. - Further, in the ball screws in the aforementioned respective example, as there can be a case where an inner diameter of the inner
circumferential surface 405 of theball screw nut 402 may become smaller due to the press fitting of the nut fitted member, it is preferable that an inner gap of the ball screw should be set in expectation of this situation. - The seventh embodiment is directed to a ball screw in which balls are loaded between a ball screw shaft and a ball screw nut, and is especially suited for a ball screw in which a concave defining the circulating groove formed on the inner circumferential surface of the ball screw nut.
- In the ball screw, a male screw groove is formed in the ball screw shaft, a female ball screw groove is formed in the ball screw nut, and balls are loaded between these male and female ball screw grooves, thereby allowing a smooth rotational-linear motion by rolling the balls. On the occasion of using such a ball screw, e.g. there is disclosed, in
Patent Document 5, fitting and installing a plastic gear that is a separate component on the outer circumferential surface of the ball screw nut. - However, when the nut fitted member such as the gear is fitted and installed on the outer circumferential surface of the ball screw nut, it is crucial for control fitting accuracy of the both, but there is a drawback in that it requires much care for working and assembly.
- The seventh embodiment is devised focusing on the above-identified problems, and its object is to provide a ball screw able to easily fit the nut fitted member onto the outer circumferential surface of the ball screw nut, and to fix the member.
- To solve the above-identified problems, the inventors of this invention have developed the seventh embodiment, as a result of the extensive studies, after having been obtained knowledge thereof. If it is possible to form the nut fitted member to be fitted by insert molding, such as a gear on the outer circumferential surface of the ball screw nut by insert molding, the embodiment can save labor for working and assembly. The insert molding is provided for casting it in a die. In this case, the nut fitted member is integrally formed with the ball screw nut by previously enclosing the ball screw nut therein, and by injecting resin into the die.
- However, in the typical ball screw, it is necessary to provide, so-called, the ball returning passage which returns balls rolling e.g. along the female ball screw groove, from a rolling endpoint to a rolling start point of the ball screw nut. The ball returning passage is made of a separate ball circulating member inserted from the outer circumferential surface of the ball screw nut to the inner circumferential surface of the ball screw nut where the female ball screw groove is provided. Namely, a through hole to circulate the balls is formed in the ball screw nut. When a resin is injected on the outer circumferential surface of the ball screw nut in which the through hole is formed, an injection molding pressure comes out through the through hole, which precludes insert molding.
- On the contrary, in the ball screw disclosed in
Patent Document 3 proposed by the applicant of this invention, the circulating groove constituting the ball returning passage is directly formed by plastic working on the inner circumferential surface of the ball screw nut. Since the circulating groove is formed of an S-shaped concave formed on the inner circumferential surface of the ball screw nut, the inner circumferential surface and the outer circumferential surface of the ball screw nut are in a non-through state. Thus, as long as the ball screw nut in which such an inner circumferential surface and the outer circumferential surface of this kind are in a non-through state, the nut fitted member can be manufactured by insert molding. - The ball screw according to the seventh embodiment includes: balls that are rolling elements; the ball screw shaft having on its outer circumferential surface a male ball screw groove into which the balls are received, as the rolling groove; the ball screw nut having on its inner circumferential surface a female ball screw groove, as a rolling groove, into which the balls are received, being fitted onto the ball screw shaft, the inner circumferential surface and the outer circumferential surface being in a non-through state; and a nut fitted member provided by insert molding on the outer circumferential surface of the ball screw nut.
- Further, a circulating groove constituting the ball returning passage is formed on the inner circumferential surface of the ball screw nut.
- Moreover, the nut fitted member is provided by insert molding on an outer circumferential surface of the ball screw nut so as to cover a concave on the outer circumferential surface of the ball screw nut produced with the formation of the circulating groove.
- The nut fitted member is either of or both of the sleeves or the gear with a cylindrical inner circumferential surface.
- According to the ball screw of the seventh embodiment, since the nut fitted member is fitted by insert molding onto the outer circumferential surface of the ball screw shaft of which inner circumferential surface and outer circumferential surface are in a non-through state, the nut fitted member is integrally formed to be fitted onto the outer circumferential surface of the ball screw nut, without injection pressure escaping, thereby realizing easy fixation of the nut fitted member.
- Further, forming the circulating groove constituting the ball returning passage on the inner circumferential surface of the ball screw nut facilitates putting the inner circumferential surface and the outer circumferential surface of the ball screw nut into a non-through state.
- Furthermore, by providing the nut fitted member by insert molding on the outer circumferential surface of the ball screw nut so as to cover a concave on the outer circumferential surface of the ball screw nut produced with the formation of the circulating groove, the nut fitted member and the concave are locked to each other, and it facilitates fixation of the nut fitted member to the ball screw nut.
- Moreover, constituting the nut fitted member by either of or both of the sleeve and the gear having a cylindrical inner circumferential surface facilitates to practice.
- An explanation will next be made to an embodiment of the ball screw of a seventh embodiment by referring to drawings.
FIG. 46 is a longitudinal sectional view showing a first example of the ball screw of the seventh embodiment. -
Reference numeral 501 inFIG. 46 is a ball screw shaft. Aball screw nut 502 is fitted onto theball screw shaft 501. A maleball screw groove 504 is formed on the outer circumferential surface of the ball screw shaft 51. Moreover, a femaleball screw groove 506 is formed on the innercircumferential surface 505 of theball screw nut 502. Multiple balls are loaded between the maleball screw groove 504 and the femaleball screw groove 506. Accordingly, e.g. when theball screw shaft 501 or theball screw nut 502 rotates, theballs 507 roll through within the maleball screw groove 504 and the femaleball screw groove 506, and theball screw nut 502 or theball screw shaft 501 linearly moves together therewith. This achieves a smooth rotational-linear motion. - Additionally, in the first example, as is disclosed in
Patent Document 3 proposed by the applicant of this invention, the circulatinggroove 508 constituting the ball returning passage is directly formed by plastic working on the innercircumferential surface 505 of theball screw nut 502. The circulatinggroove 508 is formed of an S-shaped concave formed on the innercircumferential surface 505 of theball screw nut 502. Thus, in the first example, it enables putting the innercircumferential surface 505 and the outer circumferential surface 609 of theball screw nut 502 into a non-through state. - In the first example, a
gear 511 integrated with a sleeve-like gear base 512 is formed to be fitted, as a nut fitted member, by insert molding, on the outercircumferential surface 509 of theball screw nut 502. The insert molding is, as described above, a subject to be casted into a die, in this case, theball screw nut 502 is enclosed in the die, and the resin is injected into the die. Then, thegear 511 and thegear base 512 that are the nut fitted member are integrally formed to be fitted onto theball screw nut 502. - Since the
ball screw nut 502 of the ball screw in the first example is, as previously discussed, in an non-through state between the innercircumferential surface 505 and the outercircumferential surface 509, even by injection molding thegear 511 and thegear base 512 on the outercircumferential surface 509 of theball screw nut 502, it is clear of worry about coming out injection pressure even by insert molding. This integrally and firmly form and fit them onto the outercircumferential surface 509 of theball screw nut 502. - In this manner, in the ball screw of the first example, the rolling
bearing 511 that is the nut fitted member is formed to be fitted by insert molding onto the outercircumferential surface 509 of theball screw nut 502 which is fitted onto theball screw shaft 501 and of which innercircumferential surface 505 and the outer circumferential surface are in a non-through state. Thereby, thegear 511 and thegear base 512 that are nut fitted member are integrally formed to be fitted onto the outer circumferential surface of theball screw nut 502, which easily fixes thegear 511 and thegear base 512. - Furthermore, by forming the circulating
groove 508 constituting the ball returning passage on the innercircumferential surface 505 of theball screw nut 502, the innercircumferential surface 505 and the outercircumferential surface 509 of theball screw nut 502 are liable to be in a non-through state. -
FIG. 47 is a longitudinal sectional view showing a second example of the ball screw of the seventh embodiment. A lower half of the longitudinal section is identical with that of the upper half thereof, and hence its illustration is omitted for simplification. Whereas theball screw nut 502 shows a state where the female ball screw groove is not formed on the innercircumferential surface 505, a construction of theball screw nut 502 per se is the same as that shown inFIG. 46 of the first example. Thus, the same construction is denoted by the same reference numeral, and so its detailed description is omitted for brevity's sake. - The second example, as with the first example, is to integrally form and fit by insert molding the sleeve-
like gear base 512 and thegear 511 onto the outercircumferential surface 509 of theball screw nut 502. Besides, in the second example, a convex 510 is previously provided on the outer circumferential surface of theball screw nut 502. The convex 510 is, as shown inFIG. 48 , produced at the time the circulatinggroove 508 is formed by plastic working on the innercircumferential surface 505 of theball screw nut 502. - The circulating
groove 508 in the second example inserts e.g. a die for pressing forming of the circulatinggroove 508 in the innercircumferential surface 505 of a material (blank) of theball screw nut 502. After that, when a bar having a cum face is e.g. pushed inside of the die, a slide protrusion member slidably attached in the die presses the innercircumferential surface 505 of theball screw nut 502, and presses the innercircumferential surface 505 of theball screw nut 502 with that pressing force to form by plastic deformation the circulatinggroove 508. With the pressing forming of the circulatinggroove 508, a material of theball screw nut 502 swells out outward, and expands as the convex 510 on the outercircumferential surface 509. - The
gear base 512 and thegear 511 that are the nut fitted member are provided by insert molding on the outercircumferential surface 509 of theball screw nut 502 produced with the formation of the circulatinggroove 508 like this, so as to cover the convex 510 of the outercircumferential surface 509 of theball screw nut 502. Thereby, thegear base 512 and thegear 511 and convex 510 are locked to restrain a movement of them in an axial direction of them, which provides an easier way of fixing thegear base 512 and thegear 511 to theball screw nut 502. - Further, by forming to fit onto by insert molding the
gear base 512 so as to cover the both end faces in an axial direction of theball screw nut 502, a movement of thegear base 512 and thegear 511 in an axial direction are restrained, thereby firmly fixing thegear base 512 and the gear 611 to the outer circumferential surface of theball screw nut 502. -
FIG. 49 is a longitudinal sectional view showing a third example of the ball screw of the seventh embodiment. A lower half of the longitudinal section is identical with that of the upper half thereof, and hence its illustration is omitted for simplification. Whereas theball screw nut 502 shows a state where the female ball screw groove is not formed on the innercircumferential surface 505, a construction of theball screw nut 502 per se is the same as that shown inFIG. 46 of the first example. Thus, the same construction is denoted by the same reference numeral, and so its detailed description is omitted for brevity's sake. - In the third example, as with the first example, the
gear base 512 and thegear 511 are integrally formed to be fitted by insert molding onto the outercircumferential surface 509 of theball screw nut 502. The convex 510 is previously provided, as with the second example, on the outer circumferential surface of theball screw nut 502 in the third example. The reason why the convex 510 is provided is the same as that of the second example. - In the third example, the
gear base 512 acting as a base of thegear 511 is set to a portion covering the convex 510 from an illustrated left end face of theball screw nut 502. Covering in this manner by thegear base 512 either of an end face of theball screw nut 502, and either of the convex 510, restrains, as with the second example, a movement in an axial direction of thegear base 512 and thegear 511, which provides a more further easy way of fixing thegear base 512 and thegear 511 to theball screw nut 502. -
FIG. 50 is a longitudinal sectional view showing a fourth example of the ball screw of the seventh embodiment. A lower half of the longitudinal section is identical with that of the upper half thereof, and hence its illustration is omitted for simplification. Whereas theball screw nut 502 shows a state where the female ball screw groove is not formed on the innercircumferential surface 505, a construction of theball screw nut 502 per se is the same as that shown inFIG. 46 of the first example. Thus, the same construction is denoted by the same reference numeral, and so its detailed description is omitted for brevity's sake. Also, on the outer circumferential surface of theball screw nut 502 in the fourth example, the convex 510 is previously provided as with the second example. The reason why the convex 510 is provided is the same as that of the second example. - In the fourth example, the
sleeve 513 is integrally formed to be fitted as the nut fitted member by insert molding onto the outercircumferential surface 509 of theball screw nut 502. The length in an axial direction of thesleeve 513 is reconciled with that of theball screw nut 502. In this way, by integrally forming to fit thesleeve 513 onto the outercircumferential surface 509 of theball screw nut 502, the outer circumferential surface of the ball screw nut 502 (to be exact, the outer circumferential surface of the sleeve 513) may be formed into a circle having the same diameter, e.g. without removing the convex 510 by grinding and cutting. If the outer circumferential surface of the ball screw nut 502 (sleeve 513) may be formed into a circle having the same diameter, a bearing, a gear, or the like are easily to be fitted onto its outer circumferential surface thereof. In this occasion, manufacturing thesleeve 513 with relatively hard resin realizes proper fitting of the bearing and the gear. As an alternative, the outer circumferential surface of thesleeve 513 is not necessarily limited to a circle, instead it may be formed into a polygon. Additionally, it is also possible to take a key seat, an encoder, a flange, and another shape such as an ellipse. -
FIG. 51 is a longitudinal sectional view showing a fifth example of the ball screw of the seventh embodiment. A lower half of the longitudinal section is identical with that of the upper half thereof, and hence its illustration is omitted for simplification. Whereas theball screw nut 502 shows a state where the female ball screw groove is not formed on the innercircumferential surface 505, a construction of theball screw nut 502 per se is the same as that shown inFIG. 46 of the first example. Thus, the same construction is denoted by the same reference numeral, and so its detailed description is omitted for brevity's sake. Also, on the outer circumferential surface of theball screw nut 502 in the fifth example, the convex 510 is previously provided as with the second example. The reason why the convex 510 is provided is the same as that of the second example. - In the fifth example, the
sleeve 513 and thegear 511 are integrally formed to be fitted as the nut fitted member by insert molding onto the outercircumferential surface 509 of theball screw nut 502. The length in an axial direction of thesleeve 513 is set to one which is enough to cover the illustrated left end face of theball screw nut 502 and does not reach an illustrated right end face. Further, the thickness in a radial direction of thesleeve 513 is set to one enough to cover the convex 510. In this manner, by integrally formed to fit thesleeve 513 onto the outercircumferential surface 509 of theball screw nut 502, as with the fourth example, the outer circumferential surface (to be exact, the outer circumferential surface of the sleeve 513) of theball screw nut 502 may be formed into a circle having the same diameter, e.g. without removing the convex 510 by grinding and cutting. - As materials of the
ball screw nut 502 in each example of the above-mentioned seventh embodiment, carbon steel, bearing steel, stainless steel, etc., may be applied. Further, the nut fitted member such as thegear 511 and thesleeve 513 formed to be fitted by insert molding onto the outer circumferential surface of theball screw nut 502 is desirable to use thermoplastic resin suitable for injection molding. Instead, materials may be available, in which filler and fiber reinforcement are mixed into the thermoplastic resin. As ideal resin materials, polyamide, polyphenylene sulfide, polyimide, polyether ether ketone, fluororesin, etc. may be employed. Further, Ideal fiber reinforcements include glass fiber and carbon fiber. - Preferably, materials may be employed in which glass fiber and the carbon fiber are mixed into polyamide and polyphenylene sulfide resin so as to have percentage content of 5 to 50 percent by weight. In particular, where teeth of the gear is formed and it is taken as a fitted surface, percentage content of the glass fiber and the carbon fiber is ranging from 20 to 50 percent by weight. More preferably, it is ranging from 30 to 50 percent by weight. When percentage content of the glass fiber and the carbon fiber are less than or equal to 20 percent by weight, it is likely to be insufficient strength as teeth of the gear. Moreover, when percentage content is more than or equal to 50 percent by mass, it faces difficulties for injection molding.
- In each example of the seventh embodiment, because, as previously discussed, the inner
circumferential surface 505 and the outercircumferential surface 509 of theball screw nut 502 are in a non-through state, it enables working at relatively high injection molding pressure. Therefore, this enhances percentage content of reinforcing filler such as glass fiber and carbon fiber, which manufactures more firm resin product such as the gear. For example, when the gear is formed, it is most desirable for the reinforcing filler to be 40 to 50 percent by mass. Further, as it is allowed to increase the injection molding pressure, good fluidity of resin is ensured, despite of the existence ofplural convexes 510, thereby filling resin without gaps. - In the second to fifth examples, while the convex of the outer
circumferential surface 509 of theball screw nut 502 produced during the formation of the circulatinggroove 508 is utilized as a locking portion of the nut fitted member, such as thegear 511 and thesleeve 513, e.g. a groove or a key seat may previously be formed by knurling on the outercircumferential surface 509 of theball screw nut 502, and may be used it as a rotation stopper for the nut fitted member. - Further, the nut fitted member to be fitted by insert molding onto the outer circumferential surface of the
ball screw nut 502 may be anything, as far as it can be manufactured e.g. by insert molding on the outer circumferential surface of theball screw nut 502, in addition to the each example. Additionally, it is also possible that the nut fitted member manufactured by insert molding is formed in a post processing into a desired shape. - It is noted that the ball screw shown in each example of the second to the seventh embodiments may be applied to the ball screw illustrated in the first embodiment.
- The ball screw illustrated in the first to the seventh embodiments may preferably be applied to an electric steering device (especially, a rack-type electric power steering device).
FIG. 52 is a partial cross-sectional view of a steering gear of the electric power steering device. - In
FIG. 52 , within a rack and apinion housing 621 constituting a steering gear case, arack shaft 623 and a pinion (not shown) constituting the rack and pinion mechanism are installed thereinto, and the pinion is connected to alower shaft 622. Therack shaft 623 has arack 625 provided at left inFIG. 52 to be meshed with the pinion, as well as a spherical joint 627 swingably supporting atie rod 615 is fixed at the both ends. A screw shaft of the ball screw is used for therack shaft 623. - At the illustrated right end of the rack and
pinion housing 621, aball screw housing 633 is mounted. In the ball screwhousing 633, a front end of theelectric motor 635 is fixed by bolting to a lower portion thereof, as well as adriving gear 637 fixed to a shaft of theelectric motor 635 and a drivengear 639 to be meshed with thedriving gear 637 are housed therein. Also, in the ball screwhousing 633, aball nut 645 is rotatably held via a double row angular contact ball bearing. - The
ball nut 645 is received in an inner diameter of the drivengear 639. Between an inner diameter side of shaft center of the drivengear 639 and at an outer diameter side of theball nut 645, there is provided a splinefitting portion 661. Thereby, the drivengear 639 and theball nut 645 may feely be slide relatively. - At the illustrated right side of the
rack shaft 623, a male ball screw groove (threaded portion) 651 is formed. On the other hand, afemale ball groove 653 is formed, and between amale ball groove 651 and thefemale ball groove 653, a large number ofsteel balls 655 constituting circulating balls are loaded. Also, in theball nut 645, a circulating groove (not shown) to circulate thesteel balls 655 are formed. - In the electric power steering device, when a steering wheel is steered by a driver, a steering force is transmitted from the
lower shaft 622 to the pinion, arack shaft 623 moves in an either left or a right direction inFIG. 52 with therank 625 to be meshed with it, and a wheel is steered through right and left tie rods. At the same time, based on an output from a steering torque sensor (not shown), theelectric motor 635 rotates with prescribed rotating toque in a forward or a reverse direction. Rotating torque is transmitted via thedriving gear 637 and the drivengear 639 to theball nut 645. Then, by rotating the ball nut 456, a thrust force is acted to the male ball groove 651 of therack shaft 623 via thesteal balls 655 to be engaged into the femaleball screw groove 653, thereby exerting a steering assist torque. -
-
- 1: ball screw
- 2: screw shaft
- 3: screw groove
- 5: nut
- 5 a: screw groove
- 7: ball rolling passage
- 9: ball
- 11: ball circulating passage
- 13: flange
- 15: teeth train for a gear
- 17: encoder
- 20: steel material
- 21: blank
- 22: concaved groove
- 31: key
- 33: bevel gear
- 35: detent
- 37: screw (external screw)
- 39: circumferential groove
- 41: rotor motor
- 43: inner ring
- 44: outer ring
- 45: roller
- 46: rolling bearing
- 47: cam face
- 48: one-way clutch
- 101: nut blank
- 111: inner circumferential surface of nut blank
- 111 a: circle defining an inner circumferential surface of nut blank
- 115: S-shaped concave (concave constituting ball returning passage)
- 115 a: S-shaped concave (concave constituting ball returning passage)
- 115 b: S-shaped concave (concave constituting ball returning passage)
- 116: concave
- 117: concave
- 118: tapered surface
- 102: blank holder
- 121: concave (restraining member)
- 121 a: recess
- 121 b: recess
- 121 c: recess
- 121 d: Circumferential groove (recess)
- 122: lid member (restraining member)
- 103: cam slider
- 103A: cam slider
- 133: slope of cam slider (cam mechanism)
- 135: S-shaped convex
- 136: stopper forming convex
- 104: cam driver
- 141: slanted side face of cam slider (cam mechanism)
- 142: circumferential side
- 105A: cam slider
- 105B: cam slider
- 153: slope of cam slider (cam mechanism)
- 155 a: S-shaped convex
- 155 b: S-shaped convex
- 156: stopper forming convex
- 106: cam driver
- 161 a: slope of cam driver (cam mechanism)
- 161 b: slope of cam driver (cam mechanism
- 162: base
- 107A, 107B: cam slider
- 173: slope of cam slider (cam mechanism)
- 175 a: S-shaped convex
- 175 b: S-shaped convex
- 108: cam driver
- 181: slope
- 181 a: slope of cam driver (cam mechanism)
- 161 b: slope of cam driver (cam mechanism)
- 182: base
- 182 a: tapered surface
- 191: stopper (projection)
- 192: stopper (projection)
- 193: stopper (projection)
- 194: flange (projection)
- 201: nut blank
- 211: inner circumferential surface of nut blank
- 212A to 212D: S-shaped concave
- 213: outer circumferential surface of nut blank
- 214: upper end face of nut blank
- 214A to 214D: convex
- 215: lower end face of nut blank
- 215A to 215D: convex
- 202: cam driver
- 221: base
- 222; body
- 222 a to 222 b: slanted slope (can mechanism)
- 203A to 203D: cam slider
- 231: outer circumferential surface of cam slider
- 233: slope of cam slider (cam mechanism)
- 235A to 235D: S-shaped convex
- 204: stand
- 241: concave
- 242 a to 242 d: recess
- 205: restraining member
- 251 to 254: split of restraining member
- 251 a to 254 a: large-diameter portion of inner circumferential surface of restraining member
- 251 b to 254 b: small-diameter portion of inner circumferential surface of restraining member
- 251 c to 254 c: surface restraining upper end face of nut blank
- 251 d to 254 d: recess
- 206: outer member
- 261: inner circumferential surface
- 401: ball screw shaft
- 402: ball screw nut
- 403: outer circumferential surface
- 404: male ball screw groove
- 405: inner circumferential surface
- 406: female ball screw groove
- 407: ball
- 408: circulating groove
- 409: outer circumferential surface
- 410: abutting end face
- 411: rolling bearing (nut fitted member)
- 412: sleeve (nut fitted member)
- 413: inner circumferential surface
- 414: gear (nut fitted member)
- 415: inner circumferential surface
- 501: ball screw shaft
- 502: ball screw nut
- 502: outer circumferential surface
- 504: male ball screw groove
- 505: inner circumferential surface
- 506: female ball screw groove
- 507: ball
- 508: circulating groove
- 509: outer circumferential surface (nut fitted member)
- 510: convex
- 511: gear (nut fitted member)
- 512: gear base (nut fitted member)
- 513: sleeve (nut fitted member)
Claims (27)
1. A ball screw comprising: a screw shaft having on an outer circumferential surface a spiral screw groove; a nut having on its inner circumferential surface a screw groove facing the screw groove of the screw shaft; a plurality of balls rollably loaded in a spiral ball rolling passage formed by the both screw grooves; and a ball circulating passage to return the balls from an end point to a start point of the ball rolling passage for circulating the balls,
wherein the ball circulating passage is formed of a concaved groove formed by concaving a groove on a part of the cylindrical inner circumferential surface of the nut, and an outer circumferential formation is integrally formed on a part facing the concaved groove on the outer circumferential surface of the nut,
wherein the outer circumference formation is at least one of an encoder, a teeth train for a gear, a rotation stopper, a key, a key seat, a motor rotor, an inner ring of a one-way clutch, a raceway groove for a bearing, a screw, a circumferential groove, and another shape of the outer circumferential surface.
2. A ball screw comprising: a screw shaft having on an outer circumferential surface a spiral screw groove; a nut having on its inner circumferential surface a screw groove facing the screw groove of the screw shaft; a plurality of balls rollably loaded in a spiral ball rolling passage formed by the both screw grooves; and a ball circulating passage to return the balls from an end point to a start point of the ball rolling passage for circulating the balls,
wherein the ball circulating passage is formed of a concaved groove formed by concaving a groove on a part of the cylindrical inner circumferential surface of the nut, and an outer circumferential formation is integrally formed on a part facing the concaved groove on the outer circumferential surface of the nut,
wherein the concaved groove is formed on the inner circumferential surface of the nut blank by pressing the inner circumferential surface of the nut blank with a convex, by a press method using a die of the cam mechanism,
the cam mechanism comprising:
a cam driver internally inserted into a nut blank and moving in an axial direction;
a cam slider disposed between the nut blank and the cam driver, and having the convex corresponding to the concaved groove, the convex moving in a radial direction of the nut with a movement of the cam drive.
3. The ball screw according to claim 1 , wherein the nut is produced by machining a cylindrical metal blank to produce a roughly formed nut having a substantially identical shape with the nut, concaving a groove on the part of the cylindrical inner circumferential surface of the roughly formed nut, forming the concaved groove constituting the ball circulating passage, and forming the outer circumferential formation on the outer circumferential surface of the roughly formed nut.
4. The ball screw according to claim 1 , wherein the nut is produced by machining a cylindrical metal blank to produce a roughly formed nut having a substantially identical shape with the nut, by concaving a groove a part of the cylindrical inner circumferential surface of the roughly formed nut by plastic working, forming the concaved groove constituting the ball circulating passage, and forming the outer circumferential formation on the outer circumferential surface of the roughly formed nut.
5. The ball screw according to claim 1 , wherein a protrusion is provided integrally with the nut on an end face in an axial direction of the nut.
6. The ball screw according to claim 1 , further comprising a nut fitted member to be fitted by press fitting onto the outer circumferential surface of the nut.
7. The ball screw according to claim 6 , wherein an interference of the nut fitted member and the nut by press fitting exceeds 0.02 percent of an external dimension of the outer circumferential surface of the nut onto which the nut fitted member is fitted.
8. The ball screw according to claim 6 , wherein an interference of the nut fitted member and the nut by press fitting exceeds 0.02 percent and less than 0.16 percent of an external dimension of the outer circumferential surface of the nut onto which the nut fitted member is fitted.
9. The ball screw according to claim 6 , wherein when the nut fitted member is press fitted into the nut, shrink fitting is used which heats the nut fitted member to fit onto the nut.
10. The ball screw according to claim 6 , wherein the nut fitted member is any of a sleeve a bearing, a gear, each having a cylindrical inner circumferential surface, and a combination thereof.
11. The ball screw according to claim 1 , further comprising a nut fitted member provided by insert molding on the outer circumferential surface of the nut.
12. A manufacturing method of ball screw nut comprising: a nut having on an inner circumferential surface a spiral groove and on an outer circumferential surface a protrusion; a screw shaft having on an outer circumferential surface a spiral groove; a plurality of balls rollably loaded between a raceway formed by the both screw grooves; and a ball returning passage formed as a concave on an inner circumferential surface of the nut, to return the balls from an end point to a start point of the raceway, the plurality of balls rolling in the raceway to cause the nut to relatively move with respect to the screw shaft,
wherein formation of the concave on the inner circumferential surface of the nut, and formation of the protrusion on the outer circumferential surface of the nut are simultaneously performed by cold forging.
13. The ball screw according to claim 1 , wherein the concaved groove is formed on the inner circumferential surface of the nut blank by pressing the inner circumferential surface of the nut blank with a convex, by a press method using a die of the cam mechanism,
the cam mechanism comprising:
a cam driver internally inserted into a cylindrical nut blank and moving in an axial direction;
a cam slider disposed between the nut blank and the cam driver, and having the convex corresponding to the concaved groove, the convex moving in a radial direction of the nut with a movement of the cam driver; and
a restraining member for restraining both end faces in the axial direction and the outer circumferential surface of the nut blank, and having a recess on an inner circumferential surface that receives the outer circumferential surface of the nut blank,
wherein the outer circumferential formation is formed by projecting a periphery of the nut blank into the recess of the restraining member.
14. The ball screw according to claim 13 , wherein a working in a subsequent process is performed after a process in the press method using the die, by using the outer circumferential formation, a recess or a tapered surface formed on the inner circumferential surface of the outer circumferential formation, as a reference surface or a holding part.
15. The ball screw according to claim 13 , wherein the outer circumferential formation is a torque transmission part, a positing part, or a mounting part.
16. A ball screw comprising: a screw shaft having on an outer circumferential surface a spiral screw groove; a nut having on an inner circumferential surface a screw groove facing the screw groove of the screw shaft; a plurality of balls rollably loaded in a spiral ball rolling passage formed by the both screw grooves; and a ball circulating passage to return the ball from an end point to a start point of the ball rolling passage for circulating the balls,
wherein the ball circulating passage is formed of a concaved groove on a part of the cylindrical inner circumferential surface of the nut, and a protrusion is provided on an end face in an axial direction of the nut.
17. The ball screw according to claim 16 , wherein the concaved groove is formed on the inner circumferential surface of the nut blank by pressing the inner circumferential surface of the nut blank with a convex, by a press method using a die of a cam mechanism,
the cam mechanism comprising:
a cam driver internally inserted into a cylindrical nut blank and moving in an axial direction;
a cam slider disposed between the nut blank and the cam driver, and having the convex corresponding to the concaved groove, the convex moving in a radial direction of the nut with a movement of the cam driver; and
a restraining member for restraining both end faces in the axial direction and the outer circumferential surface of the nut blank, and having a recess on an end face to receive the both end faces in the axial direction of the nut blank,
wherein the protrusion is formed by projecting an excess material, produced with the formation of the concaved groove, of the nut blank into a recess of the restraining member.
18. The ball screw according to claim 13 , further comprising a nut fitted member provided by insert molding on the outer circumferential surface of the nut, the nut fitted member being formed to cover the outer circumferential formation on the outer circumferential surface of the nut produced with the formation of the concaved groove.
19. The ball screw according to claim 11 , wherein the nut fitted member is either of or both of the sleeve or a gear having a cylindrical inner circumferential surface.
20. The ball screw according to claim 1 , wherein the screw groove of the nut is provided only at a part where the balls rotate on the inner circumferential surface of the nut, and is not provided at a part where the balls do not rotate.
21. The ball screw according to claim 5 , wherein the protrusion is provided at a part in the circumferential direction of the end face in an axial direction of the nut.
22. The ball screw according to claim 2 , further comprising a nut fitted member provided by insert molding on the outer circumferential surface of the nut.
23. The ball screw according to claim 2 , further comprising a nut fitted member to be fitted by press fitting onto the outer circumferential surface of the nut.
24. The ball screw according to claim 23 , wherein an interference of the nut fitted member and the nut by press fitting exceeds 0.02 percent of an external dimension of the outer circumferential surface of the nut onto which the nut fitted member is fitted.
25. The ball screw according to claim 23 , wherein an interference of the nut fitted member and the nut by press fitting exceeds 0.02 percent and less than 0.16 percent of an external dimension of the outer circumferential surface of the nut onto which the nut fitted member is fitted.
26. The ball screw according to claim 23 , wherein when the nut fitted member is press fitted into the nut, shrink fitting is used which heats the nut fitted member to fit onto the nut.
27. The ball screw according to claim 23 , wherein the nut fitted member is any of a sleeve a bearing, a gear, each having a cylindrical inner circumferential surface, and a combination thereof.
Applications Claiming Priority (15)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2010-061182 | 2010-03-17 | ||
JP2010061182 | 2010-03-17 | ||
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JP2011-042529 | 2011-02-28 | ||
JP2011042529 | 2011-02-28 | ||
PCT/JP2011/001560 WO2011114728A1 (en) | 2010-03-17 | 2011-03-16 | Ball screw, manufacturing method of nut for ball screw |
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US14/678,459 Active US9737926B2 (en) | 2010-03-17 | 2015-04-03 | Ball screw and manufacturing method of nut for ball screw |
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EP (1) | EP2532924B1 (en) |
JP (1) | JP5418667B2 (en) |
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US20190107186A1 (en) * | 2016-03-23 | 2019-04-11 | Nsk Americas, Inc. | Integrated ball screw linear actuator |
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Citations (24)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US1971083A (en) * | 1930-11-29 | 1934-08-21 | Schlaa Friedrich Im | Production of ball races and the like |
US2924113A (en) * | 1960-02-09 | Orner | ||
US3006212A (en) * | 1959-10-28 | 1961-10-31 | Gen Motors Corp | Stamped ball nut |
US3579782A (en) * | 1968-08-02 | 1971-05-25 | Stig Lennart Hallerback | Method of manufacturing rolling bearing components |
US3657781A (en) * | 1969-11-20 | 1972-04-25 | Riv Officine Di Villar Perosa | Method for the manufacture of rolling bearings |
US4369558A (en) * | 1980-09-10 | 1983-01-25 | Toyota Jidosha Kogyo Kabushiki Kaisha | Outer race working method and apparatus therefor |
US5988007A (en) * | 1996-06-21 | 1999-11-23 | Thk Co., Ltd. | Ball screw apparatus |
US6192585B1 (en) * | 1998-11-04 | 2001-02-27 | Valeo Electrical Systems, Inc. | Ball nut and method of high volume manufacturing of same |
US20010027693A1 (en) * | 2000-01-28 | 2001-10-11 | Rexroth Star Gmbh | Nut unit |
US6334370B1 (en) * | 1998-09-11 | 2002-01-01 | Thk Co., Ltd. | Ball screwed nut, linearly guiding apparatus using the same, ball screw for steering and method of manufacturing the ball screwed nut |
US6464034B1 (en) * | 1999-02-04 | 2002-10-15 | Ntn Corporation | Electrically powered steering device |
US6761080B2 (en) * | 2000-04-27 | 2004-07-13 | Thomson Saginaw Ball Screw Co., Llc | Multiple stage, multiple extend, speed reducing ball screw linear actuator and method of constructing and operating the actuator |
US20060053919A1 (en) * | 2004-08-27 | 2006-03-16 | Delphi Technologies, Inc. | Method for making a ball-nut and method for making a ball-screw |
US7013747B2 (en) * | 2002-04-15 | 2006-03-21 | White Stroke Llc | Internal recirculating ball screw and nut assembly |
US20070209465A1 (en) * | 2004-04-08 | 2007-09-13 | Thk Co., Ltd. | Screw Device And Method Of Manufacturing The Same |
US20080250887A1 (en) * | 2005-09-05 | 2008-10-16 | Nsk Ltd. | Ball Screw Mechanism and Assembling Method of the Same |
US20090064811A1 (en) * | 2005-10-19 | 2009-03-12 | Thk Co., Ltd. | Ball screw device |
US7536929B2 (en) * | 2002-09-17 | 2009-05-26 | Ina-Schaeffler, Kg | Ball screw and method for producing a spindle nut, in particular of a ball screw |
US20100043582A1 (en) * | 2007-05-01 | 2010-02-25 | Ntn Corporation | Ball Screw And A Method For Manufacturing The Same |
US20100172606A1 (en) * | 2007-06-13 | 2010-07-08 | Schaeffler Kg | Method for the production of a roller bearing without machining |
US20100242652A1 (en) * | 2006-03-31 | 2010-09-30 | Thk Co., Ltd. | Ball screw device |
US20130008275A1 (en) * | 2010-03-31 | 2013-01-10 | Nsk Ltd. | Method for Manufacturing Nut for Ball Screw and Ball Screw |
US20130139628A1 (en) * | 2010-08-04 | 2013-06-06 | Shouji Yokoyama | Method of Production of Nut for Ball Screw Use and Ball Screw |
US20130220047A1 (en) * | 2010-11-15 | 2013-08-29 | Nsk Ltd | Ball Screw |
Family Cites Families (40)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3393575A (en) | 1966-05-31 | 1968-07-23 | Trw Inc | Ball screw actuator |
US3393576A (en) | 1966-05-31 | 1968-07-23 | Trw Inc | Ball screw actuator |
JPS4937059A (en) | 1972-08-04 | 1974-04-06 | ||
US3902377A (en) | 1973-10-23 | 1975-09-02 | Tech Integrale | Ball screw and nut mechanism |
JPS5641861Y2 (en) | 1976-12-28 | 1981-09-30 | ||
ZA837328B (en) * | 1982-10-14 | 1984-05-30 | Pfd Ltd | Manufacture of article having undercut internal surface |
JPH067202Y2 (en) | 1986-06-02 | 1994-02-23 | エヌティエヌ株式会社 | Oil-free multi-start ball screw |
JPS6411466U (en) | 1987-07-10 | 1989-01-20 | ||
JPH0645149U (en) * | 1992-11-30 | 1994-06-14 | エヌティエヌ株式会社 | Ball screw nut device |
JP3398998B2 (en) | 1993-02-08 | 2003-04-21 | 日本精工株式会社 | Preload mechanism in screw device |
JP3394332B2 (en) | 1994-08-25 | 2003-04-07 | トヨタ自動車株式会社 | Burring processing method |
DE19739216C2 (en) | 1997-09-08 | 1999-07-08 | Star Gmbh | Spindle drive |
JPH11104781A (en) | 1997-09-29 | 1999-04-20 | Matsushita Electric Ind Co Ltd | Method and device for processing bearing with groove |
JP2000297855A (en) * | 1999-04-15 | 2000-10-24 | Ntn Corp | Electric power steering device |
JP2000297854A (en) | 1999-04-15 | 2000-10-24 | Ntn Corp | Electric power steering device |
DE19936837C2 (en) | 1999-08-05 | 2001-11-08 | Wilfried Erb | Ball screw nut |
JP3844922B2 (en) * | 1999-11-04 | 2006-11-15 | Ntn株式会社 | Ball screw and electric power steering apparatus including the same |
US6736235B2 (en) * | 2000-11-29 | 2004-05-18 | Ntn Corporation | Powered steering device and ball screw mechanism therefor |
DE10236281A1 (en) | 2002-08-08 | 2004-02-19 | Ina-Schaeffler Kg | Method for manufacturing spindle nuts for ball thread drives involves arranging externally profiled tool mandrel in hollow blank and exerting radial force from outside to reshape blank to form helical track |
JP4214371B2 (en) | 2002-10-29 | 2009-01-28 | 日本精工株式会社 | Electric actuator |
JP2004150593A (en) * | 2002-10-31 | 2004-05-27 | Nsk Ltd | Ball screw device |
US20040083840A1 (en) | 2002-11-04 | 2004-05-06 | King David E. | Integrated recirculation path in ball nut / ball screw |
JP4027238B2 (en) | 2003-02-03 | 2007-12-26 | 株式会社ジェイテクト | Ball screw device and method of manufacturing ball screw device |
JP4458224B2 (en) | 2003-02-20 | 2010-04-28 | 株式会社ジェイテクト | Ball screw device |
DE10333909A1 (en) | 2003-07-25 | 2005-03-24 | Zf Lenksysteme Gmbh | Steering nut and ball screw and thus equipped motor vehicle steering |
JP2005249036A (en) | 2004-03-03 | 2005-09-15 | Koyo Seiko Co Ltd | Ball screw device |
JP2005321059A (en) | 2004-05-10 | 2005-11-17 | Thk Co Ltd | Screw device |
JP4608262B2 (en) | 2004-06-11 | 2011-01-12 | Thk株式会社 | Thread groove processing method |
DE102004040360A1 (en) | 2004-08-20 | 2006-02-23 | Ina-Schaeffler Kg | Ball Screw |
CN100552264C (en) * | 2005-06-17 | 2009-10-21 | Thk株式会社 | The manufacture method of screw device and screw device |
US8220353B2 (en) | 2005-07-29 | 2012-07-17 | Thk Co., Ltd. | Screw device manufacturing method and screw device |
JP2007092968A (en) | 2005-09-30 | 2007-04-12 | Nsk Ltd | Manufacturing method for nut |
JP2007127152A (en) * | 2005-11-01 | 2007-05-24 | Yamaha Motor Co Ltd | Ball screw unit, electronic component transferring device, surface mounting machine, and ic handler |
JP2008002523A (en) | 2006-06-21 | 2008-01-10 | Ntn Corp | Electric linear actuator |
JP2008215422A (en) * | 2007-03-01 | 2008-09-18 | Ntn Corp | Ball screw for actuator and its screw grooving method |
JP2008281063A (en) * | 2007-05-09 | 2008-11-20 | Nsk Ltd | Ball screw mechanism |
JP2009014025A (en) * | 2007-07-02 | 2009-01-22 | Tokuo Takamura | Device with screw rod slid and moved |
DE112009000277T5 (en) | 2008-02-06 | 2011-02-17 | Trw Automotive U.S. Llc, Sterling Heights | Ball Screw |
JP2009192033A (en) * | 2008-02-18 | 2009-08-27 | Nidec Tosok Corp | Motor component, manufacturing method of motor component |
JP2010096317A (en) | 2008-10-20 | 2010-04-30 | Nsk Ltd | Ball screw device |
-
2011
- 2011-03-16 JP JP2012505512A patent/JP5418667B2/en active Active
- 2011-03-16 CN CN201180010963.4A patent/CN102906457B/en active Active
- 2011-03-16 EP EP11755919.5A patent/EP2532924B1/en active Active
- 2011-03-16 US US13/581,210 patent/US20120325036A1/en not_active Abandoned
- 2011-03-16 KR KR1020127022404A patent/KR101414381B1/en active IP Right Grant
- 2011-03-16 WO PCT/JP2011/001560 patent/WO2011114728A1/en active Application Filing
-
2015
- 2015-04-03 US US14/678,459 patent/US9737926B2/en active Active
Patent Citations (24)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2924113A (en) * | 1960-02-09 | Orner | ||
US1971083A (en) * | 1930-11-29 | 1934-08-21 | Schlaa Friedrich Im | Production of ball races and the like |
US3006212A (en) * | 1959-10-28 | 1961-10-31 | Gen Motors Corp | Stamped ball nut |
US3579782A (en) * | 1968-08-02 | 1971-05-25 | Stig Lennart Hallerback | Method of manufacturing rolling bearing components |
US3657781A (en) * | 1969-11-20 | 1972-04-25 | Riv Officine Di Villar Perosa | Method for the manufacture of rolling bearings |
US4369558A (en) * | 1980-09-10 | 1983-01-25 | Toyota Jidosha Kogyo Kabushiki Kaisha | Outer race working method and apparatus therefor |
US5988007A (en) * | 1996-06-21 | 1999-11-23 | Thk Co., Ltd. | Ball screw apparatus |
US6334370B1 (en) * | 1998-09-11 | 2002-01-01 | Thk Co., Ltd. | Ball screwed nut, linearly guiding apparatus using the same, ball screw for steering and method of manufacturing the ball screwed nut |
US6192585B1 (en) * | 1998-11-04 | 2001-02-27 | Valeo Electrical Systems, Inc. | Ball nut and method of high volume manufacturing of same |
US6464034B1 (en) * | 1999-02-04 | 2002-10-15 | Ntn Corporation | Electrically powered steering device |
US20010027693A1 (en) * | 2000-01-28 | 2001-10-11 | Rexroth Star Gmbh | Nut unit |
US6761080B2 (en) * | 2000-04-27 | 2004-07-13 | Thomson Saginaw Ball Screw Co., Llc | Multiple stage, multiple extend, speed reducing ball screw linear actuator and method of constructing and operating the actuator |
US7013747B2 (en) * | 2002-04-15 | 2006-03-21 | White Stroke Llc | Internal recirculating ball screw and nut assembly |
US7536929B2 (en) * | 2002-09-17 | 2009-05-26 | Ina-Schaeffler, Kg | Ball screw and method for producing a spindle nut, in particular of a ball screw |
US20070209465A1 (en) * | 2004-04-08 | 2007-09-13 | Thk Co., Ltd. | Screw Device And Method Of Manufacturing The Same |
US20060053919A1 (en) * | 2004-08-27 | 2006-03-16 | Delphi Technologies, Inc. | Method for making a ball-nut and method for making a ball-screw |
US20080250887A1 (en) * | 2005-09-05 | 2008-10-16 | Nsk Ltd. | Ball Screw Mechanism and Assembling Method of the Same |
US20090064811A1 (en) * | 2005-10-19 | 2009-03-12 | Thk Co., Ltd. | Ball screw device |
US20100242652A1 (en) * | 2006-03-31 | 2010-09-30 | Thk Co., Ltd. | Ball screw device |
US20100043582A1 (en) * | 2007-05-01 | 2010-02-25 | Ntn Corporation | Ball Screw And A Method For Manufacturing The Same |
US20100172606A1 (en) * | 2007-06-13 | 2010-07-08 | Schaeffler Kg | Method for the production of a roller bearing without machining |
US20130008275A1 (en) * | 2010-03-31 | 2013-01-10 | Nsk Ltd. | Method for Manufacturing Nut for Ball Screw and Ball Screw |
US20130139628A1 (en) * | 2010-08-04 | 2013-06-06 | Shouji Yokoyama | Method of Production of Nut for Ball Screw Use and Ball Screw |
US20130220047A1 (en) * | 2010-11-15 | 2013-08-29 | Nsk Ltd | Ball Screw |
Cited By (12)
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US10253866B2 (en) * | 2014-07-31 | 2019-04-09 | Canon Kabushiki Kaisha | Driving force transmission mechanism and image forming apparatus |
US9903452B2 (en) * | 2014-11-21 | 2018-02-27 | Moteck Electric Corp. | Structure of linear actuator |
US20180087636A1 (en) * | 2015-04-02 | 2018-03-29 | Nsk Ltd. | Screw shaft, manufacturing method thereof, and ball screw device |
US10663045B2 (en) * | 2015-04-02 | 2020-05-26 | Nsk Ltd. | Screw shaft, manufacturing method thereof, and ball screw device |
US20170088162A1 (en) * | 2015-09-25 | 2017-03-30 | Steering Solutions Ip Holding Corporation | Ball screw assembly |
US9802640B2 (en) * | 2015-09-25 | 2017-10-31 | Steering Solutions Ip Holding Corporation | Ball screw assembly |
US20190107186A1 (en) * | 2016-03-23 | 2019-04-11 | Nsk Americas, Inc. | Integrated ball screw linear actuator |
US10816067B2 (en) * | 2016-03-23 | 2020-10-27 | Nsk Americas, Inc. | Integrated ball screw linear actuator |
US11441648B2 (en) | 2016-03-23 | 2022-09-13 | Nsk Americas, Inc. | Integrated ball screw linear actuator |
US10300575B2 (en) | 2016-08-23 | 2019-05-28 | Sanshin Co., Ltd. | Ball screw polishing method and device thereof |
CN109386581A (en) * | 2018-12-09 | 2019-02-26 | 扬州海通电子科技有限公司 | A kind of closely-pitched self-locking type gear hobbing lead screw |
EP4234867A1 (en) | 2022-02-25 | 2023-08-30 | Overhead Door Corporation | Swing door operator |
Also Published As
Publication number | Publication date |
---|---|
JPWO2011114728A1 (en) | 2013-06-27 |
EP2532924B1 (en) | 2019-11-20 |
CN102906457B (en) | 2016-05-25 |
US9737926B2 (en) | 2017-08-22 |
KR20120118486A (en) | 2012-10-26 |
KR101414381B1 (en) | 2014-07-01 |
JP5418667B2 (en) | 2014-02-19 |
US20150283600A1 (en) | 2015-10-08 |
CN102906457A (en) | 2013-01-30 |
WO2011114728A1 (en) | 2011-09-22 |
EP2532924A4 (en) | 2018-04-25 |
EP2532924A1 (en) | 2012-12-12 |
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