JP2008095744A - Ball screw device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means for improving the productivity of a screw shaft having a shaft flange, and for improving the reliability for the strength. <P>SOLUTION: A ball screw device 1 comprises: the screw shaft 2 having a spiral shaft track groove 3 formed in the outer peripheral surface, and a support 5 formed in the end of the shaft track groove 3; a nut 12 having a nut track groove 13 opposite to the shaft track groove 3 in the inner peripheral surface; and a plurality of balls 11 to screw the shaft track groove 3 and the nut track groove 13. A fitting groove 9 is engraved in the support 5 of the screw shaft 2. A shaft flange 17 having an outer diameter greater than the diameter of the support 5, and an internal diameter fitted into the bottom 9a of the fitting groove 9 is divided into two pieces 17a, 17b. The flange pieces 17a, 17b are fitted into the fitting groove 9 respectively so as to be secured in the screw shaft 2. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a ball screw device used for driving or power transmission of a linear movement mechanism such as positioning of a moving table of a machine device such as a machine tool, an industrial machine, a semiconductor manufacturing apparatus, an electric injection molding machine, and an electric press molding machine. About.

A screw shaft used in a ball screw device is generally formed by forming a shaft raceway groove by cutting or rolling, leaving a finishing allowance, and finishing the shaft raceway groove of the shaft material by grinding or cutting.
In addition, when machining or grinding is performed on machine tools, a large axial load is applied to the nut during injection or mold clamping on an electric injection molding machine, so it is supported at the end of the screw shaft to receive this reaction force. A support bearing such as an angular ball bearing or a tapered roller bearing is generally disposed in the support portion.

  In such a ball screw device that requires load resistance, it is relatively easy to increase the load resistance by increasing the circulation path of the nut or increasing the ball diameter. Due to the space of the machine equipment to be used, the axial length restriction is large and it is difficult to increase the number of rows of support bearings. Therefore, a large-diameter support bearing is generally used, and the side surface of the inner ring that supports the axial load The outer diameter of the ball screw device may be larger than the outer diameter of the shaft raceway groove, and in order to increase the contact area with the side surface of the inner ring, a shaft flange with a larger outer diameter is provided between the shaft raceway groove and the support portion. It is done.

In this case, if the shaft flange is machined integrally with the screw shaft by cutting, it will be necessary to cut out from the round bar with the shaft flange finishing allowance added, resulting in wasted machining time and shaft material. There arises a problem that the manufacturing cost increases.
For this reason, the conventional ball screw device has an axial raceway groove formed spirally on the outer peripheral surface of the screw shaft and a nut raceway groove facing the axial raceway groove formed on the inner peripheral surface of the nut via a plurality of balls. When the support part of the support bearing and its shaft flange are formed at the shaft end of the screw shaft, the shaft material with the shaft raceway groove formed by rolling and the support part and shaft flange are formed. A large diameter shaft with a shaft material and an insert material with a melting point lower than that of the round bar, joined while controlling the heating temperature, pressure, holding time and inert atmosphere. Productivity of screw shafts with flanges is improved.
JP-A-8-285030 (mainly second page paragraph 0003 and third page paragraph 0007-0010, FIG. 1, Table 1)

  However, in the above-described conventional technology, an insert material having a lower melting point is sandwiched between the shaft material and the round bar, and the shaft material and the round bar are controlled while controlling the heating temperature, pressure, holding time, and inert atmosphere. Therefore, if the welding conditions such as the heating time are not properly managed, the predetermined bonding strength cannot be obtained, and the bonding strength is likely to vary, and the screw shaft is bonded during the operation of the ball screw device. There is a problem that there is a risk of damage from the part.

This impairs the holding function of the axial position, which is an essential function of the ball screw device, and ensuring the reliability of the joint is an important issue.
The present invention has been made to solve the above problems, and provides a means for improving the productivity of a screw shaft provided with an annular shaft flange and improving the reliability of the strength. Objective.

  In order to solve the above problems, the present invention provides a screw shaft having a spiral shaft raceway groove formed on the outer peripheral surface, a support portion formed at an end of the shaft raceway groove, and an inner peripheral surface. A ball screw device comprising: a nut having a nut raceway groove facing the shaft raceway groove; and a plurality of balls for screwing the shaft raceway groove and the nut raceway groove. A split groove is provided in which an annular member having an outer diameter larger than the diameter of the support portion is divided into two in the diametrical direction, and the split pieces are respectively fitted in the fitting grooves. It is fixed to the screw shaft.

  Thus, according to the present invention, it becomes possible to form an annular member by fitting a split piece formed separately from the screw shaft into the fitting groove of the screw shaft, stabilizing the shaft strength of the screw shaft and increasing its strength. As a result, it is possible to improve the productivity of the screw shaft by reducing the amount of cutting in the radial direction of the screw shaft.

  Embodiments of a ball screw device according to the present invention will be described below with reference to the drawings.

FIG. 1 is an explanatory view showing a ball screw device of the first embodiment, FIG. 2 is an explanatory view showing a side surface of the screw shaft of the first embodiment, and FIG. 3 is a sectional view of the shaft flange along the AA cross section line of FIG. It is explanatory drawing shown.
In FIG. 1, 1 is a ball screw device.
Reference numeral 2 denotes a screw shaft of the ball screw device 1, which is a stepped shaft member made of a steel material such as an alloy steel, and an axial raceway groove 3 having a substantially semicircular arc cross-sectional shape is formed on the outer peripheral surface thereof with a predetermined lead. It is formed in a spiral shape.

  Reference numeral 5 denotes a support portion, which simultaneously supports axial loads and radial loads such as angular ball bearings and tapered roller bearings formed at the outer ends in the axial direction of the shaft raceway grooves 3 formed on the screw shaft 2. A cylindrical portion where the inner peripheral surface of the inner ring 6a of the support bearing 6 that can be fitted is fitted, and has a diameter equivalent to the diameter of the outer peripheral surface of the screw shaft 2 at the portion where the shaft raceway groove 3 is formed. A mounting screw portion 5a to which a lock nut 23 is screwed is formed at an end portion opposite to the shaft raceway groove 3.

The support bearing 6 of the present embodiment is formed by two angular ball bearings that are combined in the back surface.
Reference numeral 7 denotes an attachment portion. In order to attach a drive device such as a motor (not shown) for rotating the screw shaft 2 rotatably supported by the support bearing 6 attached to the support portion 5, the support portion 7 of the screw shaft 2 is attached. It is a cylindrical portion provided coaxially on the outer side in the axial direction of the mounting screw portion 5a.

Reference numeral 9 denotes a fitting groove, as shown in FIG. 2, which is a circumferential groove having a rectangular cross-sectional shape formed on the side of the axial raceway groove 3 on the outer peripheral surface of the support portion 5, and has a cylindrical bottom portion 9a. The diameter is smaller than the diameter of the outer peripheral surface of the support portion 5.
Reference numeral 11 denotes a ball as a rolling element of the ball screw device 1, which is a sphere made of a steel material such as alloy steel.

Reference numeral 12 denotes a nut of the ball screw device 1, which is a cylindrical member made of a steel material such as alloy steel, and has a substantially semicircular arc cross-sectional shape that faces the shaft raceway groove 3 on its inner peripheral surface. 13 is formed with the same lead as the shaft raceway groove 3.
Reference numeral 14 denotes a nut flange portion which is provided at one end of the outer peripheral portion of the nut 12 and is fixed to a moving base of a mechanical device (not shown) with a mounting bolt or the like from a bolt hole (not shown) provided in the nut flange portion 14. .

  Reference numeral 15 denotes a return tube, which is made of a steel material, a resin material, or the like, and is a tube bent into a substantially U shape having an inner diameter through which the ball 11 can pass, and is formed in a hole reaching the nut raceway groove 13 provided in the nut 12. The end portion is fitted and has a function of communicating with the nut raceway groove 13, and a part of the outer peripheral surface of the nut 12 is fixed to the flat surface 12 a cut out in parallel with the axial direction by the tube fixture 16.

The shaft raceway groove 3 of the screw shaft 2 and the nut raceway groove 13 of the nut 12 opposed thereto form a load path on which the ball 11 rolls, and both ends thereof are communicated by a return tube 15 so that a circulation path is formed. It is formed.
The return tube 15 of the present embodiment is provided at two locations in the axial direction of the nut 12, whereby the circulation path of the present embodiment is formed in two rows.

  A plurality of balls 11 and a predetermined amount of lubricant, such as grease, are sealed in these circulation paths, and the shaft raceway groove 3 and the nut raceway groove 13 are screwed together via the balls 11 to rotate the screw shaft 2. Accordingly, the ball 11 circulates in the circulation path, and the ball 11 rolling on the load path is reciprocally supported by the load applied to the nut 12 while being lubricated by the lubricant, and the nut 12 is the axis of the screw shaft 2. The rotary motion of the screw shaft 2 is converted into the linear motion of the nut 12.

  Reference numeral 17 denotes a shaft flange as an annular member, and as shown in FIG. 3, a steel material such as alloy steel having an outer diameter larger than the diameter of the outer peripheral surface of the support portion 5 and greater than or equal to the outer diameter of the inner ring of the support bearing 6. The flange pieces 17a and 17b are formed in a relatively thick donut plate shape having an inner diameter to be fitted to the outer peripheral surface of the bottom portion 9a of the fitting groove 9, and are divided into two arcuate pieces in the diameter direction. It is configured.

In this case, the inner diameter of the shaft flange 17 is formed by setting a predetermined fitting allowance for intermediate fitting or interference fitting to the diameter of the outer peripheral surface of the bottom 9 a of the fitting groove 9.
One flange piece of the shaft flange 17, for example, the flange piece 17 a is provided with a bolt hole 20 through which a bolt 19 formed in the vertical direction of each dividing surface 18 is inserted, and the other flange piece 17 b is provided with the flange piece 17 a. A screw hole 21 into which the bolt 19 inserted through the bolt hole 20 is screwed is provided, and the flange pieces 17a and 17b are respectively inserted into the fitting grooves 9 of the screw shaft 2 and the inner peripheral surfaces thereof are fitted into the fitting grooves 9. The flange portions 17a and 17b are fitted into the fitting grooves 9 by being fitted to the outer peripheral surface of the bottom portion 9a and fastened with bolts 19 arranged on both sides of the bottom portion 9a.

As a result, the flange pieces 17a and 17b are formed in an annular shape with their dividing surfaces 18 facing each other through a gap, and the shaft flange 17 is installed on the shaft track groove 3 side of the support portion 5, The abutting support bearing 4 is fastened and fixed by a lock nut 23 that is screwed into the mounting screw portion 5a.
In this case, if the number of bolts 19 for fastening the flange pieces 17a and 17b is at least one on each side of the bottom 9a of the fitting groove 9, the total number is not limited to two, but three or more. It may be.

In order to improve the mounting accuracy of the shaft flange 17, the inner peripheral surface of the shaft flange 17 and the outer peripheral surface of the bottom 9a of the fitting groove 9 are preferably finished by grinding.
Further, when the perpendicularity of the shaft flange 17 with respect to the screw shaft 2 is required, after fixing the flange pieces 17 a and 17 b to the screw shaft 2, the end face of the shaft flange 17 on the required side is placed outside the support portion 9. It is good to finish by grinding etc. on the basis of a diameter.

Furthermore, when there is a possibility that the shaft flange 17 rotates relative to the screw shaft 2 as the screw shaft 2 rotates, the one flange piece 17a is passed through in the radial direction and fitted into the bottom 9a of the fitting groove 9. It is advisable to provide a driving pin for matching.
Furthermore, when there is a possibility that the shaft flange 17 after fixing is deformed due to the gap between the divided surfaces 18 of the flange pieces 17a and 17b, a spacer having the same thickness as the gap is inserted between the divided surfaces 18. It is good to do so.

  As described above, the shaft flange 17 of the present embodiment is fixed by fitting the flange pieces 17 a and 17 b formed separately from the screw shaft 2 into the fitting groove 9 of the screw shaft 2. In addition to receiving the axial load of the support bearing 6 using the end surface on the 5 side, it is possible to stably maintain a predetermined shaft strength by eliminating the management of the joining conditions such as the heating time. It is possible to prevent damage during operation and improve the reliability of its strength, and to reduce the amount of cutting in the radial direction of the screw shaft 2 and improve its productivity.

  Further, when the shaft flange 17 is formed by joining, it is necessary to finish the shaft raceway groove 3 by grinding or cutting after joining, and it is necessary to release the grinding tool or cutting tool in the axial direction. Although the shaft raceway groove 3 cannot be machined to the end face of the screw shaft 2, there is a problem that the stroke is shortened in the case of the screw shaft 2 of the same length. Since the flange pieces 17a and 17b formed separately after finishing the groove 3 are fitted into the fitting groove 9 of the screw shaft 2 to form the shaft flange 17, the shaft raceway groove 3 is fitted as shown in FIG. It is possible to perform the finishing process by causing the fitting groove 9 to function as a relief groove of the tool by grinding or cutting up to the side surface of the groove 9, that is, the end face of the shaft flange 17 on the shaft raceway groove 3 side. Effective thread range of raceway groove 3 The made longer in the case of forming the screw shaft 2 of the same stroke, it is possible to shorten the overall length of the screw shaft 2.

The same applies to the case where the shaft flange 17 is formed by joining and the finishing of the shaft raceway groove 3 after joining is omitted. That is, in the case of joining, it is necessary to provide a space between the end face of the shaft flange 17 and the end of the shaft raceway groove 3 in order to avoid the thermal effect on the shaft raceway groove 3 at the time of joining, This is because the stroke is shortened in the case of a screw shaft.
As described above, in this embodiment, a fitting groove is provided in the support portion formed at the shaft end portion of the screw shaft of the ball screw device, and the fitting groove is fitted with an outer diameter larger than the diameter of the support portion. A flange piece formed separately from the screw shaft by fitting a flange piece divided into two in the diametrical direction into a shaft flange having an inner diameter that fits in the bottom of the groove and fixing it to the screw shaft Can be fitted into the fitting groove of the screw shaft to form a shaft flange, and the shaft strength of the screw shaft can be stabilized and the reliability of the strength can be improved. The amount of shaving can be reduced and the productivity can be improved.

In addition, when the shaft raceway groove is finished by grinding or cutting to the end face on the raceway groove side of the shaft flange, the effective thread range of the shaft raceway groove is lengthened to form a screw shaft with the same stroke. The overall length of the screw shaft can be shortened.
Furthermore, by providing at least two bolts arranged on both sides of the bottom of the fitting groove that is inserted into one of the flange pieces and screwed into the other, the two flange pieces are easily and reliably screwed. Can be fixed to.

  In this embodiment, the outer diameter of the outer peripheral surface of the support portion has been described as being equivalent to the diameter of the outer peripheral surface of the screw shaft in the portion where the shaft raceway groove is formed. When the inner diameter of the surface is larger than the diameter of the outer peripheral surface of the screw shaft at the portion where the shaft raceway groove is formed, the outer diameter of the support portion is increased to match the inner diameter of the inner ring as shown in FIG. A fitting groove may be formed in the part. In this way, when the inner diameter of the inner ring is larger than the diameter of the outer peripheral surface of the screw shaft where the shaft raceway groove is formed, the amount of cutting in the radial direction of the screw shaft is minimized and the productivity is improved. be able to.

  In the present embodiment, the inner diameter of the shaft flange has been described as being fitted to the bottom of the fitting groove. However, if the accuracy is not required, the inner diameter of the shaft flange is set to the outer diameter of the bottom of the fitting groove. It is good also as a state which provided a clearance gap larger. In this case, the shaft flange is not fixed to the screw shaft alone, but is fixed to the screw shaft by assembling the support bearing and tightening it with a lock nut.

FIG. 6 is an explanatory view showing the ball screw device of the second embodiment, and FIG. 7 is an explanatory view showing a cross section of the shaft flange along the BB cross section line of FIG.
In addition, the same part as the said Example 1 attaches | subjects the same code | symbol, and abbreviate | omits the description.
In FIG. 6, reference numeral 31 denotes a ring, which is a relatively thin cylindrical member formed of a metal material, and an inner peripheral surface thereof is a flange piece fitted in the fitting groove 9 of the screw shaft 2. It is formed to a diameter obtained by subtracting a predetermined tightening allowance from the diameter of the outer peripheral surface formed by 17a and 17b, and is fitted and fixed to the outer peripheral surface of the flange pieces 17a and 17b by press fitting or the like, and the flange pieces 17a and 17b are screwed It has a function of fixing to the shaft 2.

As shown in FIG. 7, the flange pieces 17a and 17b of the present embodiment are flange pieces in which the bolt holes 20 and the screw holes 21 shown in the first embodiment are not formed.
Reference numeral 33 denotes a housing, which is a fixing member to which the outer ring 6b of the support bearing 6 is fixed. An oil seal 34 is attached to the shaft flange 17 side, and the lip portion of the oil seal 34 is a flange piece 17a. , 17b is in sliding contact with the outer peripheral surface of the ring 31 fitted to the outer peripheral surface of 17b.

  Thus, since the flange pieces 17a and 17b of the present embodiment are fixed to the fitting groove 9 of the screw shaft 2 by the ring 31 fitted to the outer peripheral surface thereof, the respective divided surfaces of the flange pieces 17a and 17b. The vicinity of 18 spreads outward in the radial direction, so that the outer peripheral surface of the shaft flange 17 can be prevented from being deformed into a lemon shape, and the circumferential discontinuity formed by the gap between the divided surfaces 18 can be prevented. The outer peripheral surface of the shaft flange 17 can be covered with a smooth cylindrical surface, and the lip portion can be brought into sliding contact with the outer peripheral surface of the ring 31 while preventing the lip portion of the oil seal 34 from being damaged.

  In this case, when improving the cylindricity and surface roughness of the outer peripheral surface of the ring 31, after the ring 31 is fitted to the outer peripheral surface of the flange pieces 17 a and 17 b, grinding is performed on the basis of the axis of the screw shaft 2. It is advisable to carry out finishing by, for example. In this way, the sealing performance of the oil seal 34 that is in sliding contact with the outer peripheral surface of the ring 31 can be improved, and damage to the lip portion of the oil seal 34 can be further prevented.

In this embodiment, the ring 31 is fixed to the outer peripheral surfaces of the flange pieces 17a and 17b by press-fitting. However, the ring 31 may be fixed by shrink fitting, and the ring 31 is made of a shape memory alloy. May be formed and fixed using its shape memory property.
Moreover, although the flange pieces 17a and 17b of the present embodiment have been described as flange pieces in which the bolt holes 20 and the screw holes 21 are not formed, the bolt holes 20 and the screw holes 21 shown in the first embodiment are provided. After the flange pieces 17a and 17b are fixed to the screw shaft 2 by the bolt 19, the ring 31 may be fitted. Even if it does in this way, the effect of said ring 31 is not impaired, but it becomes possible to fix the ring 31 by adhesion | attachment.

  As described above, in this embodiment, in addition to the same effects as in the first embodiment, a ring having an inner peripheral surface that fits to the outer peripheral surface of the flange piece that fits into the fitting groove of the screw shaft is provided. By doing so, it is possible to prevent deformation in the vicinity of each split surface of the flange piece, and to smooth the outer peripheral surface of the shaft flange covering the discontinuity in the circumferential direction formed by the gap between the split surfaces. A cylindrical surface can be formed, and the lip portion or the like of the oil seal can be brought into sliding contact.

  In addition, by fixing the outer peripheral surface of the ring to the screw shaft after the flange piece fitted to the ring is finished, the finishing process is performed based on the axis of the screw shaft. The surface roughness can be further improved, the sealing performance of the oil seal slidingly contacting the outer peripheral surface of the ring can be improved, and damage to the lip portion of the oil seal can be further prevented.

  In the present embodiment, the ring 31 has been described as being cylindrical. However, as shown in FIG. 8, the ring 31 may have an L-shaped cross section having a flange portion 35. In this way, the ring 31 can be fixed to the shaft flange 31 by screwing using the flange portion 35 of the annular ring 31 without impairing the function of sliding the lip portion of the oil seal 34. become.

In each of the above embodiments, a case where the present invention is applied to a ball screw device using a tube-type circulation system that circulates a ball by a return tube has been described as an example, but a top type, an end cap type, a deflector type, etc. Even if the present invention is applied to a circulation type ball screw device, the same effect can be obtained.
In each of the above embodiments, the screw shaft of the ball screw device is rotated and the nut is moved in the axial direction. However, the ball screw device of the type that rotates the nut and moves the screw shaft in the axial direction has been described. If the present invention is applied when a shaft flange is provided as a stopper on the screw shaft, the same effect as described above can be obtained.

Explanatory drawing which shows the ball screw apparatus of Example 1. Explanatory drawing which shows the side surface of the screw shaft of Example 1. FIG. Explanatory drawing which shows the cross section of the shaft flange along the AA cross section line of FIG. Explanatory drawing which shows the other form of the screw shaft of Example 1. FIG. Explanatory drawing which shows the other form of the screw shaft of Example 1. FIG. Explanatory drawing which shows the ball screw apparatus of Example 3. Explanatory drawing which shows the cross section of the shaft flange along the BB cross section line of FIG. Explanatory drawing which shows the other form of the ring of Example 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ball screw apparatus 2 Screw shaft 3 Shaft raceway groove 5 Support part 5a Attachment screw part 6 Support bearing 7 Attachment part 9 Fitting groove 9a Bottom part 11 Ball 12 Nut 12a Plane 13 Nut raceway groove 14 Nut flange part 15 Return tube 16 Tube fixation Tool 17 Shaft flange 17a, 17b Flange piece 18 Dividing surface 19 Bolt 20 Bolt hole 21 Screw hole 23 Lock nut 31 Ring 33 Housing 34 Oil seal 35 Bump

Claims (6)

A screw shaft having a spiral shaft raceway groove formed on the outer peripheral surface, and a support portion formed at an end of the shaft raceway groove;
A nut having an inner circumferential surface formed with a nut raceway groove facing the shaft raceway groove;
In a ball screw device comprising a plurality of balls for screwing the shaft raceway groove and the nut raceway groove,
A fitting groove is provided in the support portion of the screw shaft, and a split piece obtained by dividing an annular member having an outer diameter larger than the diameter of the support portion into two in the diameter direction is provided.
A ball screw device, wherein the divided pieces are respectively fitted in the fitting grooves and fixed to the screw shaft. In claim 1,
The ball screw device, wherein the shaft raceway groove is finished by grinding or cutting to an end surface of the annular member on the shaft raceway side. In claim 1 or claim 2,
A ball screw device comprising at least two bolts disposed on both sides of a bottom portion of the fitting groove that is inserted into one of the divided pieces and screwed into the other. In any one of Claims 1 to 3,
A ball screw device comprising a ring having an inner peripheral surface fitted to the outer peripheral surface of the divided piece. In any one of Claims 1 thru | or 4,
The ball screw device, wherein at least one end surface of the annular member is a finished surface finished with the outer diameter of the support portion as a reference after fixing the divided piece to the screw shaft. In claim 4,
The ball screw, wherein the outer peripheral surface of the ring is a finished surface that is finished on the basis of the axis of the screw shaft after fixing the divided piece fitting the ring to the screw shaft apparatus.