JP2003113921A - Ball screw apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To position a circulation top through an easy process of low cost in the ball screw apparatus where the circulation top is used for circulating balls in order to improve quality thereof. SOLUTION: In the ball screw apparatus 1 where a nut shaft 3 is disposed not to rotate and not to move towards an axis and a nut member 2 is disposed to rotate and to move toward the axis with respect to the screw shaft 3, the single circulation top 6 causes double-threaded screw grooves 21a, 21b of the nut member 2 to be each independent closed loop where a group of balls 4 are rotated and circulated, and the circulation top 6 is an injection molding of a synthetic resin so as to be snap fitted into a through-hole 22 of the nut member 2. Thus, the circular top 6 is easily manufactured and rendered light. Further, only a molding accuracy of the circulation top 6 and a machining accuracy of the through-hole 22 are managed to provide precise positioning with an easy assembling operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ball screw device of a type in which a ball group is circulated by using a circulating top.

[0002]

2. Description of the Related Art Conventionally, in a ball screw device, in order to prevent a ball group interposed in each screw groove of the screw shaft and the nut member from slipping out, the screw shaft and the nut member are prevented from slipping out. It is considered that both ends of a ball passage formed by the screw groove and the screw groove of the nut member are connected and connected to each other to form a closed loop, and the balls are circulated and circulated in the closed loop.

For such ball circulation, a return tube, a circulation top, etc. are generally used. Since the present invention is directed to a ball screw device using a circulating top, the circulating top will be described below.

[0004] Generally, the circulation top connects the upstream side and the downstream side of the thread groove for one turn to each other so that the ball group on the downstream side of the thread groove passes over the thread ridge (land portion) and is upstream. The surface of the inner diameter side is provided with a meandering ball circulation groove for overcoming the thread (land) from the downstream side to the upstream side of the thread groove for one turn and returning it. There is.

This circulating top is made of metal and is usually manufactured by a casting method such as the lost wax method. Also,
The circulating top is fixed in a form of filling the gap with an adhesive while being fitted in a through hole formed through the nut member in the radial direction.

[0006]

In the above conventional example, when the circulating top is attached to the through hole of the nut member,
In order to accurately align the connecting portion of the ball circulation groove and the thread groove of the circulating top, extremely laborious and time-consuming positioning work is required, which increases the manufacturing cost and may cause misalignment. It also causes quality deterioration.

By the way, for example, when the thread grooves of two turns adjacent to each other in the axial direction of the nut member are each made into a closed loop, two circulating tops are used, but these two circulating tops surround the center thereof. Install them by shifting them by about 90 degrees. In this case, since it is necessary to use two circulating tops, the above-mentioned problem is naturally amplified.

In addition, as shown in Japanese Utility Model Laid-Open No. 6-12860, the filling member is fitted into the space above the circulating top within the through hole while the circulating top is fitted into the through hole of the nut member. Something that has been done is also considered. With this,
An extra filling member is required, which causes a cost increase.

In view of the above circumstances, the present invention aims to improve the quality of a ball screw device of the type in which a ball is circulated by using a circulating top so that the circulating top can be positioned at a low cost and by a simple method. Is intended.

[0010]

According to a first aspect of the ball screw device of the present invention, between the thread groove provided on the inner peripheral surface of the nut member and the thread groove provided on the outer peripheral surface of the screw shaft. A plurality of balls are interposed in the nut member and the screw shaft to convert torque to thrust force or to convert thrust force to torque. The inside of the through-hole formed in the direction,
A circulating spinning top for connecting and connecting a downstream side and an upstream side of at least one thread groove of the nut member to form a closed loop is attached, and this circulating top is made of a synthetic resin injection molded product, It is fitted and mounted in the through hole in a snap fit state.

According to another aspect of the ball screw device of the present invention, a plurality of balls are interposed between the screw groove provided on the inner peripheral surface of the nut member and the screw groove provided on the outer peripheral surface of the screw shaft. The nut member is configured to convert torque into thrust between the nut member and the screw shaft, or to convert thrust into torque. The nut member is radially formed at a predetermined circumferential position. A circulating top for connecting and connecting a downstream side and an upstream side of at least one threaded groove of the nut member into a closed loop is attached to the inside of the through hole, and the circulating top is used to form the nut member into a molding die. It is an insert-molded product which is embedded by directly injecting a molten synthetic resin into the through hole of the nut member while being inserted into the mold.

According to a third aspect of the ball screw device of the present invention, in the first or second aspect, the synthetic resin is a polyamide-based or polyacetal excellent in self-lubricating property.

According to a fourth aspect of the ball screw device of the present invention, in any one of the first to third aspects, reinforcing fibers are added to the synthetic resin in a required ratio.

According to a fifth aspect of the present invention, there is provided a ball screw device according to any one of the first to fourth aspects, in which the thread groove forming the closed loop has two turns adjacent to each other in the axial direction of the nut member. A single circulating spinning top is used to make a closed loop by individually connecting the downstream side and the upstream side of the plurality of windings of the plurality of turns into a closed loop.

According to a sixth aspect of the ball screw device of the present invention, in the above fifth aspect, the circulation top rolls downstream of each of the two or more thread grooves of the nut member. It has a plurality of ball circulation grooves for overcoming the threads of the screw shaft and individually guiding the balls upstream, and the plurality of ball circulation grooves are arranged substantially in the same phase and adjacent to each other in the axial direction. .

According to a seventh aspect of the present invention, there is provided a ball screw device according to any one of the first to sixth aspects, wherein the balls are rolled in an annular space facing each other between the nut member and the screw shaft. A cage ring, which is spaced apart and rotatably retained, is relatively rotatably interposed.

In short, according to the first aspect of the present invention, since the circulating top made of synthetic resin is fitted and fixed in a state of being snap-fitted into the through hole of the nut member, the circulating top is molded with high accuracy. By simply managing the processing accuracy of the through holes, it becomes possible to position and attach with high accuracy by a simple assembly work.

According to the second aspect of the invention, the synthetic resin circulating top is manufactured by insert molding in which the nut member is placed in the molding die and directly embedded in the through hole of the nut member. The installation work of can be abolished.

Further, in the third aspect of the present invention, since a synthetic resin having excellent self-lubricating property is selected as the base material of the circulating top, the lubricant in the region where the circulating top exists is insufficient. Also, it becomes possible to reduce the frictional resistance of the ball passing therethrough.

Further, according to the invention of claim 4, since the reinforcing fiber is added to the synthetic resin which is the base material of the circulating top, the mechanical strength can be increased.

Further, in the invention of claim 5, since a single circulating top attached to the nut member is used to form the closed loops in which the thread grooves of the plurality of turns of the nut member are independent from each other, compared with the conventional example. It is possible to reduce waste by reducing the number of circulating irons, the number of through holes provided in the nut member for attaching the circulating iron, the number of assembling steps, and the positioning work at the time of assembling.

Further, in the invention of claim 6, the plurality of ball circulation grooves provided in the circulation top are arranged substantially in the same phase and adjacent to each other in the axial direction, so that a plurality of screw grooves are packed in the axial direction. It becomes advantageous to reduce the occupied area in the axial direction.

If a retainer ring for holding the balls is used as in the seventh aspect of the invention, interference between the balls rolling in the screw groove can be avoided and the relative rotation between the nut member and the screw shaft can be avoided. Is maintained smoothly.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described in detail with reference to the embodiments shown in the drawings.

1 to 12 show an embodiment of the present invention. 1 is a vertical sectional view of a ball screw device, FIG.
1 is a vertical cross-sectional view showing a state where the nut member is moved to one side in the axial direction from the state of FIG. 1, FIG. 3 is an exploded perspective view of the ball screw device, and FIG. 4 is a partial cross-sectional view of the ball screw device. 7 is a perspective view of the circulating top, FIG. 6 is a front view showing a connecting portion between the nut member and the bracket, and FIG.
8 is a side view schematically showing a ball circulation path, FIG. 8 is a front view of the ball circulation path of FIG. 7, FIG. 9 is a perspective view showing a circulation top and a through hole of a nut member, and FIG. FIG. 11 is a bottom view of the top, FIG. 11 is a cross-sectional view taken along the line (11)-(11) of FIG. 10, and FIG. 12 is a cross-sectional view taken along the center line of the ball circulation groove.

In the ball screw device 1 of the illustrated example, a plurality of balls 4 are provided between the thread groove 21 provided on the inner peripheral surface of the nut member 2 and the thread groove 31 provided on the outer peripheral surface of the screw shaft 3. Has a structure in which a plurality of balls 4 are circulated by a circulating top 6 in a state where they are interposed by a cage ring 5 at equal intervals around the circumference, which is a so-called internal circulation type structure.

The nut member 2 is formed with two thread grooves 21 which are interrupted in the middle of the axial direction thereof, and the screw shaft 3 has a single thread groove continuous from one shaft end to the other shaft end. A thread groove 31 is formed. The thread groove 21 of the nut member 2 and the thread groove 31 of the screw shaft 3 are set to have the same lead angle. The cross-sectional shape of these both thread grooves 21 and 31 is a semicircular shape, but it may be a Gothic arc shape.

The retainer ring 5 holds the plurality of balls 4 rotatably at equal intervals around the circumference of the ball. The cage ring 5 is made of a thin cylindrical member, and a plurality of ball pockets 51 having an elongated hole along the axial direction are provided at several places on its circumference. Two ball pockets 51 are provided for each ball pocket 51. The balls 4 are stored one by one.

Further, the cage ring 5 is attached to the inner diameter side of the nut member 2 in a state of being substantially immovably positioned in the axial direction and in a relatively rotatable state. Therefore, the enlarged diameter portion 2 is provided on the fixed end of the nut member 2.
4 and a radially outward flange 52 at one end of the cage ring 5, respectively, and the enlarged diameter portion 2 of the nut member 2 is provided.
Fit the flange 52 of the cage ring 5 to the 4
Further, a spacer 7 for preventing slipping out is fixedly fitted in the enlarged diameter portion 24 of the nut member 2 by press fitting. However, the spacer 7 is separated from the step wall surface 25 formed at the boundary between the enlarged diameter portion 24 of the nut member 2 and the portion where the thread groove 21 is formed,
The flange 52 of the cage ring 5 is arranged between the spacer 7 and the step wall surface 25 in a state having a play in the axial direction. As a result, the cage ring 5 is substantially immovable with respect to the nut member 2 in the axial direction and is allowed to rotate relatively. However, the cage ring 5 is guided by the screw thread (land portion) of the screw shaft 3 by setting the facing gap with the screw shaft 3 smaller than the facing gap with the nut member 2. ing.

Further, as shown in FIG. 7, the circulation top 6 individually connects the upstream side and the downstream side of the two-threaded screw grooves 21a and 21b of the nut member 2 so as to communicate with each other. , 21b downstream of the ball 4 over the thread (land) 32 of the screw shaft 3 and returned to the upstream side, with respect to the single through hole 22 formed through the nut member 2 in the radial direction. Is inserted and installed.

Two ball circulation grooves 61, 62 are provided on the inner diameter side surface of the circulation top 6. The ball circulation grooves 61 and 62 are adjacent to each other in the axial direction.
It has a meandering shape so that the thread (land portion) 32 of the screw shaft 3 can be passed over and returned from the downstream side of the winding thread grooves 21a, 21b to the upstream side.

In this embodiment, the nut member 2
And a screw shaft 3 are separated from each other by a maximum distance to secure an overlapping region having a predetermined length in the axial direction, and about 2 turns of the screw groove 21 of the nut member 2 are arranged in this overlapping region. The two winding screw grooves 21a and 21b are each made into an independent closed loop with a single circulating top 6, and the balls 4 arranged in the two winding screw grooves 21a and 21b in the closed loop are independently made. I try to circulate by rolling.

The nut member 2 is provided on the bracket 8
Are integrally connected to. This bracket 8
Although not shown, a rotational power source such as a motor is engaged through a reduction gear and a rolling bearing is mounted on a cylindrical shaft that is inserted through a central hole of the cylindrical screw shaft 3 so as to be axially movable. Supported through. Further, the screw shaft 3 is supported via a rolling bearing with respect to a rotary shaft that is spline-fitted to the inner diameter side of the cylindrical shaft. This axis of rotation is
Although not shown, it is rotatably supported by a fixed part such as a case so as not to move in the axial direction.

The bracket 8 is made of a metal material whose upper half has a substantially U-shaped cross section. In other words, the bracket 8 has a shape in which one end side in the axial center direction of the inner tubular portion 81 and the outer tubular portion 82 that are concentrically provided inside and outside the radial direction are connected. The inner tubular portion 81 is arranged in a non-contact state in the central hole of the screw shaft 3 and is supported by the tubular shaft via a rolling bearing. Further, the outer tubular portion 82 is integrally fitted to the outer periphery of the region of the nut member 2 on the one end side in the axial direction, as shown in FIG.
As shown in FIG. 6A and FIG. 6B, the projections 83 provided at several places on the base side of the outer tubular portion 82 and the recesses 23 provided at several places on the inner side in the fitting direction of the nut member 2 are provided in the axial direction. The bracket 8 and the nut member 2 are integrally connected in the circumferential direction by fitting with each other. A resin gear 9 is integrally formed on the outer peripheral surface of the outer cylinder portion 82.

Next, the operation of the ball screw device 1 described above will be described. First, when the bracket 8 and the nut member 2 are rotated by driving a motor (not shown), the nut member 2 itself is guided by the screw shaft 3 while being rotated, and is linearly moved in one axial direction thereof. As a result, for example, the state shown in FIG. 1 changes to the state shown in FIG. On the other hand, when the motor is driven in the reverse rotation direction to the above, the nut member 2 is moved in the other axial direction while rotating in the opposite direction to that described above, so that the state shown in FIG. It becomes a state.

As described above, by reciprocating the nut member 2 in the axial direction, the range in which the nut member 2 and the screw shaft 3 overlap with each other in the axial direction changes greatly. Cage ring 5 positioned axially
And the threaded groove 2 of the two turns of the nut member 2 by the circulation top 6.
As the ball group 3 rolls and circulates in the 1a and 21b, the spiral movement of the nut member 2 is smoothly guided, and the nut member 2 moves reciprocally within a predetermined movement stroke range. It is possible to reliably prevent the phenomenon that the balls 4 come out from between the screw groove 21 and the screw groove 31 of the screw shaft 3.

Next, the features of this embodiment will be described.

That is, the circulating top 6 is made of synthetic resin. In this embodiment, when the circulating top 6 is made of synthetic resin, the circulating top 6 is made by injection molding, fitted into the through hole 22 of the nut member 2, and positioned and fixed by snap fitting.

Specifically, the circulating top 6 is shown in FIG. 5 and FIG.
As shown in FIG. 5, tapered protrusions 63, 63 that are flared are provided separately for the two opposing hanging pieces 6a, 6b along the ball circulation grooves 61, 62, respectively. In the vicinity of 63, 63, recesses 64, 64 for making the tapered projections 63, 63 elastically bendable are provided. On the other hand, on the nut member 2, as shown in FIG. 9, the tapered projections 63, 63 of the circulating top 6 are aligned with predetermined regions on the outer diameter opening side of the two opposing inner walls of the through hole 22. Tapered recesses 24, 24 are provided for fitting. The tapered projections 63, 63 and the recesses 64, 64 are formed at the thickest portions of the hanging pieces 6a, 6b, and are not bent due to bending when the circulating top 6 is mounted in the through hole 22. Therefore, it is taken into consideration that the ball circulation grooves 61, 62 are not deformed.

From the above, the width of the circulating top 6 is made wider than the width of the through hole 22 by the tapered projections 63, 63 of the circulating top 6, so that the circulating top 6 is inserted into the through hole 22 of the nut member 2. When it is fitted and mounted, the tapered protrusions 63, 63 of the circulation top 6 are sandwiched from both sides, so that the tapered protrusions 63, 63 are elastically bent in a manner of being pushed into the recesses 64, 64. The hole 22 can be fitted and mounted. Moreover, once the circulating top 6 is fitted and mounted in the through hole 22, the tapered protrusions 63, 63 are formed.
Elastically restores, and the tapered concave portion 24 of the through hole 22,
Since it will be snap-fitted to 24, it is fixed in a state where it does not come off. Further, when the circulating top 6 is attached to the through hole 22, the upper and lower surfaces of the circulating top 6 are set to be flush with the outer peripheral surface and the inner peripheral surface of the nut member 2.

In this embodiment, as shown in FIG. 10, recesses 65 serving as a reservoir of lubricant are provided near both ends of the ball circulation grooves 61, 62 of the circulation top 6. The recess 65 is formed in a substantially hemispherical shape,
The radius of curvature is set smaller than the radius of curvature of the ball 4. Of course, regarding the shape of the depression 65,
It can be transformed in various ways.

By the way, the circulation top 6 made of synthetic resin is made of synthetic resin having self-lubricity as a base material.
It is preferable to manufacture it by adding reinforcing fibers thereto.

Concretely, as a synthetic resin which is a base material of the circulating top 6, polyamide (PA) type, polyacetal (POM), polybutylene terephthalate (PBT),
Polyphenylene sulfide (PPS), polyethylene terephthalate (PET), etc. can be used,
Polyamide (PA) -based or polyacetal (POM) is preferable because of its excellent self-lubricating property.

As is well known, the polyamide synthetic resin (PA) is a polymer having an amide bond (-CONH) in the main ring. This polyamide-based synthetic resin has the properties of good organic solvent resistance, oil resistance, grease resistance, and high fatigue strength, but it is not limited to tetrafluoroethylene resin, molybdenum disulfide, graphite, carbon fiber, lubricating oil, etc. The self-lubricating property is further improved by compounding with.

Specific types include, for example, polyamide (PA) 6, polyamide (PA) 66, polyamide (PA) 46, polyamide (PA) 11, polyamide (PA) 12, polyamide (PA) 612, polyamide ( PA) 6T, polyamide (PA) 9T, polyphthalamide (PPA), MXD6 and the like.

PA6 is obtained by ring-opening polymerization of ε-caprolactam and has a melting point of 220 ° C. PA66 is the polycondensation of hexamethylenediamine and adipic acid and has a melting point of 260 ° C. PA46 is from ring-opening polymerization of ω-laurolactam and has a melting point of 215 ° C. PA11 is from the polycondensation of 11-aminoundecanoic acid and has a melting point of 186 ° C. PA12 is ω-
Melting point of 176 ° C due to ring-opening polymerization of laurolactam
Have. PA612 is the result of ring-opening copolymerization of caprolactam and lauryllactam. PA6T is a semi-aromatic system containing a terephthalic acid component and has a melting point of 3
Has 20 ° C. PA9T is semi-aromatic consisting of an aromatic ring and higher fatty acids and has a melting point of 308 ° C. MXD6
Is due to the polycondensation of metaxylylenediamine and adipic acid and has a melting point of 243 ° C.

The above PA6, PA66, PA46,
Although PA11, PA12, and PA612 have moisture absorption and water absorption properties, they have the property of becoming tough, such as increased impact strength when they absorb or absorb water, so whether or not they can be used depends on the operating environment. Good. However, PA6T, PA
9T is also excellent in moisture absorption and water absorption.

Further, polyacetal (POM) has excellent cyclic fatigue resistance, creep characteristics and heat resistance, and also has excellent friction and wear characteristics and is suitable as a material for mechanical elements having a sliding contact surface.

The reinforcing fibers increase the mechanical strength of the retainer ring 5, and include glass fibers (GF), carbon fibers (CF), potassium whisker titanate (Ti).
Inorganic fibers such as K) and organic fibers such as aramid fibers (AF) are preferred. These are individually added to the synthetic resin base material, and the preferable addition amount to the base material is as follows. However, a plurality of materials may be combined and the weight% may be changed and added.

Glass fiber has a very large elastic modulus and is excellent as a reinforcing material. As the addition ratio to the base material,
It is 5 to 60% by weight, preferably 30 to 40% by weight.

The carbon fiber is also called carbon fiber or carbonized fiber, and it is roughly classified into polyacrylonitrile (PAN) type carbon fiber and pitch type carbon fiber. The addition ratio to the base material is 5 to 60% by weight, preferably 15 to 30% by weight.

The aramid fiber is an aromatic polyamide fiber having excellent tensile properties and heat resistance. The addition ratio to the base material is 5 to 20% by weight, preferably 10 to
It is 20% by weight.

[0053] Potassium titanate whiskers have the property of increasing the strength of the base material and have a fiber strength lower than that of other general reinforcing fibers, so that the nut member 2 which is a contact partner is not damaged. There are advantages. Whiskers have a diameter of several nm
It is a fibrous crystal of μm, is a single crystal with almost no crystal defects, has excellent mechanical properties and is suitable as a reinforcing material.
5 to 30% by weight relative to the base material, preferably 10 to 20
% By weight. Potassium titanate whisker is an additive that is excellent in strengthening, attacking mating material, abrasion resistance, dimensional stability, and the like.

The lower limit of the weight% of each of these fibers is determined in consideration of ensuring strength, and the upper limit thereof is determined in consideration of ease of kneading with the base material, that is, moldability in injection molding. To be done.

As described above, in the above embodiment,
Since the circulation top 6 is a synthetic resin molded product, it is excellent in mass productivity, and the manufacturing cost can be greatly reduced. Moreover, in the state where the circulation top 6 is positioned by the snap fit with respect to the through hole 22 of the nut member 2. Since they are fitted and fixed, it is only necessary to control the forming accuracy of the tapered projections 63 and 63 and the processing accuracy of the tapered recesses 24 and 24.
It is possible to position and attach with high precision by simple assembly work. Moreover, since a synthetic resin having excellent self-lubricating property is selected as the base material of the circulating top 6, even if the lubricant in the ball circulating grooves 61, 62 of the circulating top 6 is insufficient, it is Since the frictional resistance of the passing ball 4 can be reduced, the behavior of the ball 4 can be stabilized and the durability of the circulating top 6 can be greatly improved.

By the way, in the above-described embodiment, a single circulating top 6 is used for independently rolling and circulating the ball group 4 in each of the two thread grooves 21a, 21b adjacent in the axial direction. Therefore, the number of parts, the number of through holes 22 of the nut member 2, the number of assembling steps of the circulating top 6 with respect to the through holes 22, and the alignment work are performed as compared with the case of using two circulating tops as in the conventional example. The number can be reduced, which can contribute to a reduction in manufacturing cost. Moreover, as shown in FIG. 7, if the two ball circulation grooves 61, 62 are provided in substantially the same phase and adjacent to each other in the axial direction, the screw groove 21 of the nut member 2 can be arranged in the axial direction. This is advantageous in reducing the area occupied in the axial direction. However, in this case, the balls 4 located in the ball circulation grooves 61, 62 cannot receive the radial load or the axial load, and therefore, the two ball circulation grooves 61, 62.
When the two are arranged close to each other in the circumferential direction and the axial direction, a load-free area can be formed within a predetermined angular range on the circumference. However, as in the above-described embodiment, if the axial dimension of the nut member 2 and the screw shaft 3 is shortened and the outer diameter dimension is set large, as shown in FIG. 8, the ball circulates on the circumference. Since the angle θ range of the region where the grooves 61 and 62 exist is small and the number of the balls 4 located in the ball circulation grooves 61 and 62 is small, it is possible to suppress the reduction of the load bearing capacity, which is a practical obstacle. There will be nothing.

The present invention is not limited to the above-described embodiments, and various applications and modifications can be considered.

First, when the circulating top 6 is made of synthetic resin, although not shown, the nut member 2 is inserted into a molding die and is melted in the through hole 22 of the nut member 2. It is also possible to directly insert a synthetic resin and insert it in a form of embedding. In this case, it is possible to further improve the production efficiency, for example, by eliminating the work of attaching the circulation top 6. The material of the circulating top 6 here may be the same as in the above embodiment.

Further, in the above embodiment, in order to independently circulate the ball group 3 in a rolling manner, each of the two thread grooves 21a and 21b of the nut member 2 is formed as a closed loop.
Although the single circulating top 6 having the two ball circulating grooves 61 and 62 is used, the present invention also includes a mode in which two circulating tops having one ball circulating groove which are generally used in the past are used.

Regarding the ball screw device 1,
Usage of rotating one of the nut member 2 and the screw shaft 3 to move the other in the axial direction, or usage of rotating one of the nut member 2 and the screw shaft 3 in the axial direction to rotate the other Can be The former usage pattern is called positive efficiency for converting torque to thrust, and the latter usage pattern is called reverse efficiency for converting thrust to torque. Hereinafter, four patterns (A-1 to A-4) related to the usage pattern in the normal efficiency and four patterns (B-1 to B-4) related to the usage pattern in the reverse efficiency will be described.

(A-1) As described in the above embodiment, the nut member 2 is moved in the axial direction while being rotated. In this case, the screw shaft 3 may be non-rotating and immobile in the axial direction, and the nut member 2 may be rotationally driven.

(A-2) The nut member 2 is moved in the axial direction without being rotated. In this case, while making the screw shaft 3 immobile in the axial direction, the nut member 2 is not rotated,
The screw shaft 3 may be driven to rotate.

(A-3) The screw shaft 3 can be moved in the axial direction while rotating. In this case, the nut member 2 may be non-rotated and immobile in the axial direction, and the screw shaft 3 may be rotationally driven.

(A-4) The screw shaft 3 is moved in the axial direction without being rotated. In this case, while the screw shaft 3 is not rotated, the nut member 2 may be immobile in the axial direction and the nut member 2 may be rotationally driven.

(B-1) The nut member 2 is rotated immovably in the axial direction. In this case, while making the nut member 2 immobile in the axial direction, the screw shaft 3 is kept non-rotating,
Should be moved in the axial direction.

(B-2) The nut member 2 is rotated while being moved in the axial direction. In this case, the screw shaft 3 may be immobile and non-rotatable in the axial direction, and the nut member 2 may be moved in the axial direction.

(B-3) The screw shaft 3 is rotated immovably in the axial direction. In this case, while the screw shaft 3 is immovable in the axial direction, the nut member 2 is not rotated and the nut member 2 is not rotated.
Should be moved in the axial direction.

(B-4) The screw shaft 3 is rotated while being moved in the axial direction. In this case, the nut member 2 may be immobile in the axial direction and not rotated, and the screw shaft 3 may be moved in the axial direction.

[0069]

In the ball screw device according to the inventions of claims 1 to 7, since the circulating top is a synthetic resin molded product, the weight of the entire device is reduced as compared with the conventional example using the metallic circulating top. In addition to being capable of being manufactured, molding can be performed with excellent mass productivity, and the manufacturing cost of the device can be reduced.

In particular, according to the first aspect of the invention, since the circulating top made of synthetic resin is fitted and fixed in a state of being snap-fitted to the through hole of the nut member, the circulating top is molded with high precision. By simply managing the processing accuracy of the through holes, it becomes possible to position and attach with high accuracy by a simple assembly work.

According to the second aspect of the invention, in manufacturing the circulating top made of synthetic resin, since the nut member is arranged in the molding die and the insert molding is directly embedded in the through hole of the nut member, the circulating top is used. It is possible to further improve the production efficiency by eliminating the installation work of.

According to the third aspect of the invention, since a synthetic resin having a high self-lubricating property is selected as the base material of the circulating top, the lubricant in the region where the circulating top exists is insufficient. However, the frictional resistance of the ball passing therethrough can be reduced, which can greatly contribute to stabilizing the behavior of the ball and improving the durability of the circulating top.

Further, in the invention of claim 4, since the reinforcing fiber is added to the synthetic resin as the base material of the circulating top, the mechanical strength can be increased, and the durability and the reliability can be improved. I can contribute.

According to the invention of claim 5, a single ball group is arranged between the thread groove of the nut member and the thread groove of the screw shaft so that the ball group is independently circulated and circulated every plural turns. Since a circulating top is used, it is possible to reduce the number of circulating tops, the number of through holes for mounting the circulating top provided in the nut member, the number of man-hours for assembling the circulating top to the through holes, and the positioning work, etc. Therefore, it is possible to reduce waste and reduce manufacturing cost.

According to the sixth aspect of the invention, since the plurality of ball circulation grooves provided in the circulation top are arranged substantially in the same phase and adjacent to each other in the axial direction, the screw grooves can be arranged in the axial direction. As a result, it is advantageous in reducing the area occupied in the axial direction and can contribute to the compactness.

If a retainer ring for holding the balls is used as in the seventh aspect of the invention, it is possible to avoid individual interference of the balls in the thread groove, so that the behavior of the balls can be stabilized. Therefore, the relative rotation between the nut member and the screw shaft is smoothly maintained, which is advantageous for improving the operational stability.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a ball screw device according to the present invention.

FIG. 2 is a vertical cross-sectional view showing a state in which the nut member is moved to one side in the axial direction from the state of FIG.

FIG. 3 is an exploded perspective view of a ball screw device.

FIG. 4 is a perspective view of a partial cross section of the ball screw device.

FIG. 5 is a perspective view of a circulating top.

FIG. 6 is a front view showing a coupling portion between a nut member and a bracket.

FIG. 7 is a side view schematically showing a ball circulation path.

8 is a front view of the ball circulation path of FIG. 7. FIG.

FIG. 9 is a perspective view showing a circulating top and a through hole of a nut member.

FIG. 10 is a bottom view of the circulating top.

11 is an arrow view of a cross section taken along line (11)-(11) of FIG.

FIG. 12 is a sectional view taken along the center line of the ball circulation groove.

[Explanation of symbols]

1 Ball screw device 2 Nut member 21 thread groove 21a, 21b Thread groove forming a closed loop 22 Through hole of nut member 24 Tapered recess in through hole of nut member 3 screw shaft 31 thread groove Four balls 5 cage ring 6 circulation tops 61,62 Circulation top ball circulation groove 63 Circular spinning taper protrusion 64 Circular spinning top recess

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masahiro Inoue             3-5-8 Minamisenba, Chuo-ku, Osaka Koyo             Within Seiko Co., Ltd. F term (reference) 3J062 AB22 AC07 BA12 BA17 CD07

Claims (7)

[Claims] 1. A plurality of balls are interposed between a thread groove provided on an inner peripheral surface of a nut member and a thread groove provided on an outer peripheral surface of a screw shaft, and torque is provided between the nut member and the screw shaft. Is a ball screw device configured to convert a thrust force into a thrust force or to convert a thrust force into a torque, wherein a nut member is inserted into a through hole radially formed at a predetermined circumferential position of the nut member. A circulating top for connecting at least one thread groove downstream and upstream to form a closed loop is attached. The circulating top is made of an injection-molded product of synthetic resin and is provided in the through hole of the nut member. A ball screw device, which is fitted and mounted in a snap fit state. 2. A plurality of balls are interposed between a screw groove provided on the inner peripheral surface of the nut member and a screw groove provided on the outer peripheral surface of the screw shaft, and torque is provided between the nut member and the screw shaft. Is a ball screw device configured to convert a thrust force into a thrust force or to convert a thrust force into a torque, wherein a nut member is inserted into a through hole radially formed at a predetermined circumferential position of the nut member. A circulating spinning top for connecting a downstream side and an upstream side of at least one threaded groove to each other to form a closed loop is attached, and the circulating spinning top is the nut member in a state in which the nut member is inserted into a molding die. A ball screw device comprising an insert-molded product which is embedded by directly injecting a molten synthetic resin into the through hole of the. 3. The ball screw device according to claim 1, wherein the synthetic resin is made of polyamide or polyacetal having excellent self-lubricating property. 4. The ball screw device according to claim 1, wherein reinforcing fibers are added to the synthetic resin at a required ratio. 5. The ball screw device according to any one of claims 1 to 4, wherein the thread groove forming the closed loop is two or more thread grooves adjacent to each other in the axial direction of the nut member, and a plurality of these thread grooves are provided. The ball screw device is characterized in that a single circulating top is used to individually connect and connect the downstream side and the upstream side of the thread groove of (1) to form a closed loop. 6. The ball screw device according to claim 5, wherein the circulation top allows the balls rolling downstream of each of the two or more thread grooves of the nut member to pass over the threads of the screw shaft. A ball screw device having a plurality of ball circulation grooves for individually guiding upstream, and the plurality of ball circulation grooves are arranged substantially in the same phase and adjacent to each other in the axial direction. 7. The ball screw device according to claim 1, wherein the balls are separated from each other in the rolling direction and rotatably held in an annular space facing the nut member and the screw shaft. Ball-screw device, characterized in that the instrument ring is interposed so as to be rotatable relative to each other.