Ball screw device

Abstract

This ball screw device is provided with a nut, a screw shaft, a plurality of balls, and one or more blocks. The outer peripheral surface of the screw shaft is provided with more than one recessed part which is recessed towards the radial inner side and accommodates the block body. The recess has a first bottom surface facing radially outward. At least a portion of the first bottom surface is a flat surface. The block has: a second bottom surface that comes into contact with the first bottom surface; a circulation groove surface which is recessed from the second bottom surface to the outside in the radial direction, and the internal space of which forms a circulation path; a bottom opening that opens the circulation path toward the inside in the radial direction; a pair of block-side openings for opening the circulation path in the circumferential direction and connecting the circulation path and the rail; and a pair of tongue pieces that guide the balls, which have entered the circulation path from the rail, to the inside in the radial direction. The portion of the first bottom surface that closes the bottom opening becomes a rolling surface of the ball that moves in the circulation path.

Description

Technical Field

[0001] This disclosure relates to ball screw devices. Background Technology

[0002] A ball screw assembly includes a nut, a screw shaft passing through the nut, multiple balls disposed between the nut and the screw shaft, and a circulation component. An inner circumferential track surface is formed on the inner circumferential surface of the nut. An outer circumferential track surface is formed on the outer circumferential surface of the screw shaft, opposite to the inner circumferential track surface. The inner and outer circumferential track surfaces form a helical track. Multiple balls are disposed on the track and move along the track in a helical direction. The circulation component returns the balls that have moved from one end of the track to the other end to one end of the track. One example of the circulation component is a block that returns the balls by one lead.

[0003] In the ball screw device described in the following patent document, a recessed portion is formed on the outer circumferential surface of the screw shaft, extending radially inward. A block is inserted into the recess and mounted on the screw shaft. Furthermore, the block has an outer diameter surface facing radially outward and a circulation groove surface recessed radially inward from the outer diameter surface. The circulation groove surface is S-shaped when viewed from the radially outward. The ball moves radially inward within the circulation groove surface of the block and passes over the threads of the nut.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2004-225770 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] According to the block described in the aforementioned patent document, when the ball moves radially inward, there is a possibility that the ball may get stuck between the circulation groove surface and the inner circumferential track surface of the nut. Therefore, smooth rolling of the ball cannot be guaranteed. In addition, if the ball gets stuck, the shoulder of the circulation groove surface may be damaged.

[0009] This disclosure was made in view of the above circumstances, and its object is to provide a ball screw device that enables smooth rolling of balls and prevents breakage of the block.

[0010] Solution for solving the problem

[0011] To achieve the above objectives, a ball screw device according to one aspect of this disclosure comprises: a nut having an inner circumferential track surface on its inner circumferential surface; a screw shaft passing through the nut and having an outer circumferential track surface on its outer circumferential surface; a plurality of balls disposed in a track between the outer circumferential track surface and the inner circumferential track surface; and one or more blocks for circulating the balls. One or more recesses are provided on the outer circumferential surface of the screw shaft, the recesses being recessed radially inward to receive the blocks. The recesses have a first bottom surface facing radially outward. At least a portion of the first bottom surface is planar. The blocks have: a second bottom surface abutting against the first bottom surface; a circulation groove surface recessed radially outward from the second bottom surface, the internal space forming a circulation path; a bottom opening that allows the circulation path to open radially inward; a pair of block side openings that allow the circulation path to open circumferentially and connect the circulation path to the track; and a pair of tongues that guide the balls entering the circulation path from the track radially inward. The portion of the first bottom surface that blocks the bottom opening becomes the rolling surface of the ball moving in the circulation path.

[0012] According to the ball screw device disclosed herein, the balls are guided radially inward by the tongue. Therefore, it is possible to prevent the balls from being trapped between the circulation groove surface and the inner circumferential track surface. That is, the rolling of the balls becomes smooth, and damage to the shoulder of the circulation groove surface is also avoided. Furthermore, the depth of the recess can be measured using the plane of the first bottom surface of the recess as a reference surface, making dimensional management of the recess easier. Additionally, the circulation path of the block opens radially inward. That is, when manufacturing the block using a mold, the mold forming the circulation path (circulation groove surface) can be moved radially inward (demolding). Therefore, compared to the case of radial blockage of the circulation path, it is easier to manufacture the block.

[0013] In addition, as a preferred embodiment of the ball screw device, the entire first bottom surface is a plane.

[0014] According to the above structure, the entire first bottom surface is flat, making its formation easy. Furthermore, when viewed from the axial direction, the circulation path becomes straight, resulting in smooth ball rolling. Additionally, when the ball enters the circulation path from the track, its path changes to be radially inward compared to the extension of the track. That is, the ball's path bends radially inward from the track. Assuming the first bottom surface is concave, the bend angle of the ball's path would be larger. On the other hand, according to this disclosure, since the first bottom surface is flat, the bend angle of the ball's path is smaller. Therefore, the ball moves (rolls) smoothly between the outer peripheral track surface and the circulation path.

[0015] Furthermore, as a preferred embodiment of the aforementioned ball screw device, when viewed from an axial direction parallel to the screw shaft, the first bottom surface extends in an intersecting direction that intersects an imaginary line extending radially outward from the center of the screw shaft. A concave surface is provided at the center of the first bottom surface in the intersecting direction, recessed radially inward. Flat surfaces are provided on both sides of the concave surface in the intersecting direction.

[0016] The ends of the first bottom surface in the intersecting directions are flat, resulting in a smaller bending angle in the ball's forward path. Therefore, according to this structure, the ball can move (roll) smoothly between the outer peripheral track surface and the circulation path. Furthermore, a concave surface is provided at the center of the first bottom surface in the intersecting directions. Therefore, compared to the case where the entire first bottom surface is flat, the two ends (flat surfaces) of the first bottom surface in the intersecting directions are positioned radially outward. As a result, the area of ​​the outer peripheral track surface removed due to the concave surface is reduced, increasing the load-bearing capacity of the ball screw assembly.

[0017] In addition, as a preferred embodiment of the ball screw device described above, the tongue is provided with ribs that protrude radially outward.

[0018] Based on the above structure, the strength of the tongue is increased by the ribs.

[0019] Furthermore, as a preferred embodiment of the ball screw device, the recess has an annular inner circumferential surface surrounding the block. The inner circumferential surface has a pair of side surfaces of the block sandwiched between two sides in an intersecting direction that intersects an imaginary line extending radially outward from the center of the screw shaft.

[0020] According to the above structure, the block is held by a pair of side surfaces. Therefore, it is possible to prevent the block from moving along the intersecting directions and falling out of the recess.

[0021] Furthermore, as a preferred embodiment of the ball screw device, the distance from the center of the screw shaft to the thread of the nut is set as R, the diameter of the ball is set as Dw, the distance between the portion of the outer diameter surface of the block that is opposite to the thread of the nut and the thread of the nut is 0.2 mm or more and 1.5 mm or less, and the wall thickness of the block from the portion of the outer diameter surface that is opposite to the thread of the nut to the circulation groove surface is 0.3 mm or more and 1.0 mm or less, and the radial clearance of the circulation path is 0.05 × Dw or more and 0.25 × Dw or less, and the distance h between the first bottom surface and the center of the screw shaft satisfies the following formula (1).

[0022] [Mathematical Expression 1]

[0023]

[0024] According to the above structure, the first bottom surface is positioned radially outward. Therefore, the track becomes longer, and the load-bearing capacity of the ball screw device is increased.

[0025] Furthermore, as a preferred embodiment of the ball screw device, when viewed from an axial direction parallel to the screw shaft, the first bottom surface extends in a cross direction intersecting an imaginary line extending radially outward from the center of the screw shaft. The recess has at least one opening in the cross direction. The block is movable along the first bottom surface in the cross direction. Alternatively, as a preferred embodiment of the ball screw device described above, the recess has two openings. The two openings are one opening on one side of the cross direction and the other opening on the other side of the cross direction.

[0026] Based on the above structure, the block can be installed from the intersecting direction of the recess. Alternatively, the block can also be installed from the radially outer side of the recess. Therefore, the options for the direction of block installation increase, and the installability of the block is improved.

[0027] Furthermore, in a preferred embodiment of the aforementioned ball screw device, the recess has a pair of opposing surfaces in the axial direction. The block has a pair of side surfaces facing the axial direction and opposite to the pair of opposing surfaces. At least one of the pair of opposing surfaces has a groove recessed in the axial direction and extending along the intersecting direction. At least one of the pair of side surfaces has a protrusion protruding in the axial direction and received within the groove. Alternatively, in a preferred embodiment of the aforementioned ball screw device, the groove is formed on both of the pair of opposing surfaces. The protrusion is formed on both of the pair of side surfaces.

[0028] According to the above structure, when a radially outward load is applied to the block, the protrusion hooks into the groove. Therefore, the radially outward movement of the block is restricted.

[0029] Furthermore, in a preferred embodiment of the aforementioned ball screw device, the recess has a pair of opposing surfaces facing each other along the axial direction. The block has an interference fit with respect to the pair of opposing surfaces and is held between them.

[0030] Based on the above structure, the block is difficult to move radially outward or in the intersecting directions. Therefore, it restricts the block from falling out of the recess.

[0031] Furthermore, as a preferred embodiment of the aforementioned ball screw device, a direction orthogonal to both the axial direction and the intersecting direction is defined as an orthogonal direction. The direction in which the center of the screw shaft is positioned when viewed from the first bottom surface is defined as the first orthogonal direction. At least one of the two ends of the block in the intersecting direction has a pressing portion protruding from the first bottom surface into the first orthogonal direction.

[0032] According to the above structure, when a load is applied to the block in the intersecting direction, the protrusion hooks onto the outer circumferential surface of the lead screw shaft. This restricts the movement of the block in the intersecting direction.

[0033] Furthermore, as a preferred embodiment of the aforementioned ball screw device, the direction orthogonal to both the axial direction and the intersecting direction is defined as the orthogonal direction. The direction, when viewed from the first bottom surface, opposite to the direction in which the center of the screw shaft is positioned is defined as the second orthogonal direction. A pressing portion is formed on the screw shaft, and this pressing portion is disposed on at least one side of the intersecting direction of the block, protruding beyond the first bottom surface into the second orthogonal direction.

[0034] According to the above structure, when a load is applied to the block in the intersecting direction, the pressing part hooks onto the block from the intersecting direction. This restricts the movement of the block in the intersecting direction.

[0035] Furthermore, as a preferred embodiment of the ball screw device, one or more holes are formed on the first bottom surface. A protrusion for entering the holes is formed on the second bottom surface.

[0036] According to the above structure, when a load is applied to the block in the intersecting direction, the protrusion hooks onto the hole. Therefore, the movement of the block radially outward is restricted.

[0037] The effects of the invention

[0038] The ball screw device disclosed herein ensures smooth ball rolling. Furthermore, it prevents damage to the shoulder of the circulation groove. Attached Figure Description

[0039] Figure 1 This is a cross-sectional view of the brake caliper according to Embodiment 1.

[0040] Figure 2 This is a three-dimensional view of the block and recess of the ball screw device in Embodiment 1.

[0041] Figure 3 This is a three-dimensional view of the concave portion of Embodiment 1.

[0042] Figure 4 This is an enlarged view of the recess and block of Embodiment 1 viewed from the radial outside.

[0043] Figure 5 This is a schematic diagram showing a cross-section obtained by cutting the block and lead screw shaft of Embodiment 1 along the circulation path; more specifically, it is... Figure 4 VV-line sectional view.

[0044] Figure 6This is a schematic diagram showing a cross-section obtained by cutting the block and lead screw shaft of Embodiment 1 along the axial direction. More specifically, it is... Figure 4 Sectional view from VI to VI.

[0045] Figure 7 This is a top view of the block of Embodiment 1 as viewed from the second bottom side.

[0046] Figure 8 This is a schematic diagram showing the cross-section obtained by cutting along the track and circulation path of the ball screw device of Embodiment 1 and the comparative example.

[0047] Figure 9 This is a top view of the recess of the ball screw device in Embodiment 2, viewed radially.

[0048] Figure 10 This is a cross-sectional view obtained by cutting the ball screw device of Embodiment 2 along the track and the circulation path.

[0049] Figure 11 It is a cross-sectional view obtained by cutting the block and recess of the ball screw device of Embodiment 3 along the axial direction and radial direction.

[0050] Figure 12 It is a cross-sectional view obtained by cutting the block and recess of the ball screw device of Embodiment 4 along the axial direction and radial direction.

[0051] Figure 13 This is a perspective view of the recess and block in embodiment 5.

[0052] Figure 14 This is a perspective view of the recessed portion of the lead screw shaft in embodiment 5.

[0053] Figure 15 This is a diagram showing the concave portion of Embodiment 5 as viewed from the intersecting direction.

[0054] Figure 16 yes Figure 15 XVI-XVI line sectional view.

[0055] Figure 17 This is a diagram of the block of Embodiment 5 as viewed from the second bottom side.

[0056] Figure 18 This is a cross-sectional view obtained by cutting the recess and the block of Embodiment 5 along a direction orthogonal to the axis direction, specifically along... Figure 15 A cross-sectional view of the recessed section and the block section cut along the XVIII-XVIII line.

[0057] Figure 19 This is a diagram showing the concave part and the block of deformation example 1 viewed from the intersecting direction.

[0058] Figure 20 This is a three-dimensional view of the concave part of the lead screw shaft in Modified Example 1.

[0059] Figure 21 This is a diagram showing the concave part and the block of deformation example 2 from the perspective of the intersection.

[0060] Figure 22 This is a diagram showing the concave part and the block of deformation example 3 from the perspective of the intersection.

[0061] Figure 23 It is a cross-sectional view obtained by cutting the concave part and the block of modified example 4 in a direction orthogonal to the axis.

[0062] Figure 24 This is a diagram of the block in Deformation Example 5 as viewed from the second bottom surface.

[0063] Figure 25 This is a cross-sectional view obtained by cutting the ball screw device of Modified Example 5 along a direction orthogonal to the axis.

[0064] Figure 26 This is a three-dimensional view of the concave part of variation example 6.

[0065] Figure 27 This is a diagram of the block of Deformation Example 6 as viewed from the second bottom surface.

[0066] Figure 28 yes Figure 26 Sectional view along the XXVIII-XXVIII line. Detailed Implementation

[0067] The present disclosure will now be described in detail with reference to the accompanying drawings. Furthermore, the present disclosure is not limited to the specific embodiments described below (hereinafter referred to as embodiments). Additionally, the constituent elements in the following embodiments include elements readily conceived by those skilled in the art, substantially the same elements, and elements of so-called equivalent scope. Moreover, the constituent elements disclosed in the following embodiments can be appropriately combined.

[0068] (Implementation Method 1)

[0069] Figure 1 This is a cross-sectional view of the brake caliper according to Embodiment 1. (Example) Figure 1 As shown, the brake caliper 100 is a device for suppressing the rotational movement of a wheel by clamping a brake disc 101 (not shown) with two brake pads 102 and 103. The brake caliper 100 includes: a brake disc 101; two brake pads 102 and 103; an electric actuator 104 for actuating the brake pads 102; and a housing 120.

[0070] The electric actuator 104 includes a motor 110 that generates rotary motion and a ball screw assembly 1 that converts rotary motion into linear motion. Hereinafter, the direction parallel to the center O1 of the screw shaft 2 of the ball screw assembly 1 will be referred to as the axial direction. In addition, the side of the axial direction where the brake disc 101 is disposed when viewed from the ball screw assembly 1 will be referred to as the first direction X1, and the direction opposite to the first direction X1 will be referred to as the second direction X2.

[0071] The motor 110 includes a stator 111 fixed to the inner circumferential surface of the housing 120, a rotor 112 disposed on the inner circumferential side of the stator 111, and an output shaft 113 rotatably supported on the housing 120. The stator 111, rotor 112, and output shaft 113 are arranged concentrically around a center O1. The output shaft 113 is fitted into the inner circumferential side of the rotor 112. When electricity is supplied to the stator 111, a rotating magnetic field is generated, and the rotor 112 and output shaft 113 rotate around the central axis O. In addition, a recess 114 for fitting a lead screw shaft 2 is formed on the end face of the output shaft 113 in the first direction X1.

[0072] The ball screw assembly 1 includes a screw shaft 2, a nut 6, and balls 4 (in... Figure 1 Not illustrated. See reference. Figure 5 ) and multiple blocks 5.

[0073] The lead screw 2 includes a connecting portion 10 rotatably supported on a bearing 117 and a lead screw body 11 disposed relative to the connecting portion 10 in a first direction X1. The end portion 10a of the connecting portion 10 in a second direction X2 engages with a recess 114. Furthermore, the connecting portion 10 is connected to the output shaft 113 in a manner that prevents relative rotation. Therefore, when the output shaft 113 rotates, the lead screw 2 also rotates. An outer peripheral track surface 13 extending in the helical direction and a plurality of recesses 14 recessed radially inward are provided on the outer peripheral surface of the lead screw body 11.

[0074] The nut 6 is cylindrical. Additionally, a cap 7 is provided on the nut 6 to block the opening in the first direction X1. An inner circumferential track surface 6a is provided on the inner circumferential surface of the nut 6, opposite to the outer circumferential track surface 13. A spiral track 8 is formed between the outer circumferential track surface 13 and the inner circumferential track surface 6a. A plurality of ball bearings 4 are arranged on this track 8.

[0075] The outer peripheral surface of the nut 6 abuts against the support surface 121 of the housing 120. Both the outer peripheral surface of the nut 6 and the support surface 121 are circular about center O1. A small gap is provided between the outer peripheral surface of the nut 6 and the support surface 121. Therefore, the nut 6 can slide freely relative to the support surface 121 in the axial direction. An anti-rotation member (not shown) is provided on the outer peripheral surface of the nut 6. This anti-rotation member restricts the nut 6 from rotating about center O1.

[0076] The cover 7 blocks the opening of the nut 6 in the first direction X1. In addition, the surface 7a of the cover 7 facing the first direction X1 contacts the brake pad 102.

[0077] Based on the above, when the nut 6 moves in the first direction X1 due to the rotation of the lead screw shaft 2, the brake pad 102 moves in the first direction X1. The brake pad 102 presses against the brake disc 101 in the first direction X1, and the brake disc 101 comes into contact with the brake pad 103. As a result, the brake disc 101 is clamped by the brake pads 102 and 103, and the rotation of the wheel (not shown) is restricted.

[0078] The block 5 is a circulating device that returns the ball 4, which has moved one lead in the track 8, to its original position by one lead. Additionally, a block 5 is mounted on a recess 14. Furthermore, in this disclosure, there is no particular limitation on the method of fixing the block 5 to the recess 14. That is, the block 5 may be fixed to the recess 14 or not. Therefore, in this disclosure, the block 5 may be fitted into the recess 14 with clearance. Alternatively, an interference fit may be provided on the block 5 to fit into the recess 14. Alternatively, the block 5 may be bonded to the recess 14. Furthermore, the block 5 may be fixed to the recess 14 by compression. Thus, there is no particular limitation on whether the block 5 is fixed.

[0079] Furthermore, although not specifically illustrated, when viewed from the axial direction, the multiple blocks 5 (multiple recesses 14) are arranged in different directions from the center O1. Thus, the load acting on the lead screw shaft 2 from the nut 6 via the balls 4 is evenly distributed in the circumferential direction. More preferably, the multiple blocks 5 are arranged at equal intervals along the circumferential direction.

[0080] Figure 2 This is a three-dimensional view of the block and recess of the ball screw device in Embodiment 1. Figure 2 As shown, block 5 is a component in which a circulation path 30 is formed internally. Examples of materials for forming block 5 include metal and resin, but this disclosure is not particularly limited to these. Block 5 has the circulation path 30 and a pair of block side openings 31 connecting the circulation path 30 to the track 8 (outer peripheral track surface 13). Figure 2 (Only one is shown in the figure), and a pair of tongues 40, 40. The recess 14 and the block 5 are described in detail below.

[0081] Figure 3 This is a three-dimensional view of the concave portion in Embodiment 1. For example... Figure 3 As shown, a recess 14 is formed by removing a portion of the outer peripheral track surface 13 of the lead screw shaft 2 radially outward. The recess 14 has an inner peripheral surface 15 surrounding the block 5 and a first bottom surface 16 facing radially outward. In the following description, as... Figure 5As shown, the imaginary line perpendicular to the first bottom surface 16 and orthogonal to the center O1 is called the imaginary line K1.

[0082] Figure 4 This is an enlarged view of the recess and block of Embodiment 1, viewed from the radially outer side. Furthermore, Figure 4 The imaginary line Z is an imaginary line passing through the center of the groove width of the outer peripheral track surface 13 and extending in a helical direction. Hereinafter, the direction parallel to the imaginary line Z will be referred to as the helical direction. Furthermore, Figure 4 The imaginary line W is an imaginary line passing through the center of the slot width of the loop path 30. Hereinafter, the path along the loop path 30 will sometimes be referred to as the length direction of the loop path 30.

[0083] like Figure 4 As shown, when viewed from the radially outer side, the recess 14 is rectangular (quadrilateral). However, although the recess 14 in this embodiment is rectangular (quadrilateral) when viewed from the radially outer side, it may also be elliptical, for example, and is not limited to the example shown in the embodiment. The inner peripheral surface 15 of the recess 14 has a pair of first opposing surfaces 17, 17 that are opposite each other in the axial direction and a pair of second opposing surfaces 18, 18 that are opposite each other in the intersecting direction Y. Furthermore, as... Figure 5 As shown, the intersection direction Y is when viewed from the axis direction and from the center O1 ( Figure 5 (Not shown in the diagram) The imaginary line K1 extending radially outward intersects (or is orthogonal to) the direction.

[0084] The first opposing surface 17 is formed by removing a portion of the thread tooth 13a of the outer peripheral track surface 13. Therefore, a thin-walled portion 19 with a small thickness (thickness in a direction orthogonal to the helical direction) H1 is provided in a portion of the thread tooth 13a.

[0085] The first opposing surface 17 extends along a helical direction. That is, the thickness H1 of the thin-walled portion 19 is uniform in the entire direction (helical direction) in which the thin-walled portion 19 extends. Therefore, the thin-walled portion 19 of this embodiment has no weaker parts, and deformation of the thread tooth 13a (thin-walled portion 19) is suppressed. In addition, this disclosure may also have the first opposing surface 17 extending along the intersecting direction Y, and is not limited to the example shown in the embodiment.

[0086] When viewed from the radially outer side, the second opposing surface 18 extends along the axial direction. For example... Figure 3 As shown, a portion of the second opposing surface 18 is removed by the outer peripheral track surface 13. That is, a screw shaft-side opening 13b is provided on the second opposing surface 18. Therefore, the second opposing surface 18 is composed of the end face 13c of the thread tooth 13a located at the center in the axial direction of the second opposing surface 18, and the partial end faces 13d of the thread tooth 13a located at both ends in the axial direction of the second opposing surface 18.

[0087] Furthermore, the end face 13c of the thread tooth 13a has the same cross-sectional shape as the thread tooth 13a. When viewed from the intersecting direction Y, the partial end face 13d of the thread tooth 13a has the same shape as one of the two sides of the end face 13c of the thread tooth 13a divided in the axial direction. For example... Figure 4 As shown, when viewed from the radially outer side, the local end face 13d of the thread tooth 13a is arc-shaped (R-shaped).

[0088] like Figure 4 As shown, a pair of second opposing surfaces 18 form a pair of side surfaces of block 5 sandwiched between the two sides in the intersecting direction Y. This restricts the movement of block 5 in the intersecting direction Y.

[0089] like Figure 3 As shown, no concave surface is formed in a portion of the first bottom surface 16. That is, the entire first bottom surface 16 is a plane. According to this embodiment, the depth of the recess 14 can be measured using the plane (first bottom surface 16) as a reference plane. If the first bottom surface 16 is concave, the depth of the recess 14 will vary depending on the measurement position on the first bottom surface 16, making it difficult to measure the depth of the recess 14. For this reason, according to this embodiment, the dimensions of the recess 14 are easy to manage, and the manufacturing of the recess 14 becomes simple.

[0090] Figure 5 This is a schematic diagram showing a cross-section obtained by cutting the block and lead screw shaft of Embodiment 1 along the circulation path; more specifically, it is... Figure 4 VV-line sectional view. Figure 6 This is a schematic diagram showing a cross-section obtained by cutting the block and lead screw shaft of Embodiment 1 along the axial direction. More specifically, it is... Figure 4 Sectional view from VI to VI.

[0091] like Figure 5 As shown, when viewed from the axial direction, the first bottom surface 16 extends in a straight line along the intersecting direction. Figure 6 As shown, when viewed from the intersecting direction, the first base surface 16 extends in a straight line along the axial direction. That is, the first base surface 16 is a plane extending along both the intersecting direction and the axial direction. Figure 6 As shown, the first opposing surface 17 is perpendicular to the first bottom surface 16. Figure 5 As shown, the second opposite face 18 (in) Figure 5 The diagram shows only a partial end face 13d, which is perpendicular to the first bottom face 16.

[0092] like Figure 5 As shown, the central portion 16a of the first bottom surface 16 in the intersecting direction is at a distance from the center O1 ( Figure 5The distance (not shown) is smaller than the distance from the two ends 16b of the first bottom surface 16 in the intersecting direction to the center O1. The depth H2 of the two ends 16b of the first bottom surface 16 in the intersecting direction becomes the same depth as the central part (bottom of the groove) of the groove width of the outer peripheral track surface 13. Therefore, as Figure 3 As shown, the first bottom surface 16 is connected to the center of the groove width (groove bottom) of the outer peripheral track surface 13 without any steps.

[0093] like Figure 4 As shown, block 5 is formed relative to center C (refer to...). Figure 4 It is point-symmetric. Block 5 has an outer peripheral surface 24 in a ring shape with center C as the center. The outer peripheral surface 24 has a pair of first side surfaces 25, 25 opposite to a pair of first opposite surfaces 17, 17, and a pair of second side surfaces 26, 26 opposite to a pair of second opposite surfaces 18, 18.

[0094] The circulation path 30 of the block 5 is formed in an S-shape when viewed from the radial outside. When the ball 4 moves within this circulation path 30, it returns one lead. Furthermore, while the circulation path 30 in this embodiment is S-shaped when viewed from the radial outside, this disclosure is not particularly limited, and it may also be a straight line connecting the lead screw shaft-side openings 13b to each other. A block-side opening 31 is provided on the second side surface 26. Thus, the ball 4 rolling on the outer peripheral track surface 13 of the lead screw shaft 2 enters the circulation path 30 of the block 5 through the block-side opening 31.

[0095] like Figure 2 As shown, the block 5 has an outer diameter surface 41 facing radially outward. Two protrusions 42 are provided on this outer diameter surface 41. The protrusions 42 extend in a helical direction. The two protrusions 42 are separated from each other in the axial direction. Therefore, a groove surface 43 is provided between the two protrusions 42, recessed radially inward and extending in a helical direction.

[0096] like Figure 6 As shown, the protrusion 42 has a semi-circular cross-sectional shape. The protrusion 42 is housed within the inner circumferential track surface 6a of the nut 6. The protrusion 42 is separate from the inner circumferential track surface 6a. Furthermore, the thread 6b of the nut 6 is housed within the groove surface 43. The groove surface 43 is separate from the thread 6b. Based on the above, the nut 6 does not interfere with the block 5.

[0097] like Figure 2 As shown, the tongue 40 protrudes from the protrusion 42 in a spiral direction. The width of the tongue 40 is H3 (refer to...). Figure 7 The front end 40a of the tongue plate 40 gradually becomes smaller and becomes a pointed shape.

[0098] like Figure 5As shown, the tongue 40 is housed within the inner circumferential track surface 6a of the nut 6. The tongue 40 is separate from and does not contact the inner circumferential track surface 6a of the nut 6. Furthermore, the front end portion 40a is located radially outward from the imaginary curve M formed by connecting the centers O4 of the balls 4 rolling on the track 8. Moreover, in this embodiment, the height difference H4 between the bottom of the groove on the inner circumferential track surface 6a and the front end portion 40a is relatively small.

[0099] According to the aforementioned tongue 40, the ball 4 entering the circulation path 30 from the block side opening 31 contacts the front end portion 40a of the tongue 40. Furthermore, in the ball 4, the front end portion 40a of the tongue 40 contacts the ball 4 (see reference). Figure 5 The portion of ball 4 (4A) of the plurality of balls 4 shown is in contact with the radially outer portion of the center O4. Therefore, a radially inward load is applied to ball 4. As a result, the forward path of ball 4 is radially inward compared to the track 8 (helical direction), and ball 4 smoothly enters the circulation path 30. Furthermore, since the height difference H4 of the front end 40a is small, ball 4 moves smoothly without jamming when in contact with the front end 40a.

[0100] Block 5 has a second bottom surface 50 facing radially inward. The second bottom surface 50 abuts against the first bottom surface 16 of the recess 14. The second bottom surface 50 extends linearly in the intersecting direction Y. Figure 6 As shown, when viewed from the intersecting direction Y, the second bottom surface 50 extends in a straight line along the axial direction. That is, the second bottom surface 50 is a plane extending along both the intersecting direction Y and the axial direction.

[0101] Figure 7 This is a top view of the block structure of the embodiment, viewed from the second bottom surface. (Example) Figure 7 As shown, a circulation groove surface 51, recessed radially outward from the second bottom surface 50, is provided on the second bottom surface 50. The internal space of the circulation groove surface 51 forms a circulation path 30. Figure 6 As shown, the cross-sectional shape obtained by cutting the circulation groove surface 51 along the groove width direction is U-shaped. That is, a bottom opening 53 is provided on the second bottom surface 50, which opens the circulation path 30 radially inward. As a result, when manufacturing the block 5, the mold forming the circulation path 30 (circulation groove surface 51) can be moved radially inward (demolding). Therefore, it is easier to manufacture the block 5 compared to the case where the radially inward side of the circulation path 30 is blocked.

[0102] like Figure 5 , Figure 6 As shown, the bottom opening 53 is blocked by the first bottom surface 16 of the recess 14. Therefore, as Figure 3 As shown, the portion of the first bottom surface 16 that blocks the bottom opening 53 (refer to...) Figure 3The two imaginary lines K54 (between the two lines) form a rolling surface 54 for the balls 4 moving in the circulation path 30 to roll. Based on the above, the balls 4 moving in the circulation path 30 are surrounded by the circulation groove surface 51 and the rolling surface 54, and do not contact the threads 6b of the nut 6.

[0103] like Figure 5 As shown, the depth H5 of the circulation groove surface 51 from the second bottom surface 50 (first bottom surface 16) is constant along the length of the circulation path 30. In other words, when viewed from the axial direction, the bottom of the circulation groove surface 51 is parallel to the first bottom surface 16. Therefore, when viewed from the axial direction, the circulation path 30 is straight in the intersecting direction Y. As a result, the movement of the ball 4 becomes smooth.

[0104] Next, refer to Figure 8 The effects of the ball screw device 1 in Embodiment 1 will be explained. Figure 8 This is a schematic diagram illustrating the cross-section obtained by cutting along the track and circulation path of the ball screw device of Embodiment 1 and the comparative example. Additionally, Figure 8 The imaginary line K10 shown is a curve that connects the centers of the balls 4 rolling on the track 8 (outer track surface 13). Figure 8 The imaginary line K11 shown is the line connecting the centers of the balls 4 rolling on the loop path 30 (first bottom surface 16). Point K12 is the intersection of imaginary lines K10 and K11. Imaginary line K13 is the tangent to imaginary line K10 at point K12.

[0105] Furthermore, the effects of Embodiment 1 will be explained by comparing it with the comparative example. For example... Figure 8 As shown, the ball screw device in the comparative example differs from that in Embodiment 1 in that the bottom surface 1016 is concave when viewed from the axial direction. Furthermore, Figure 8 The imaginary line K1011 shown is the line connecting the centers of the balls 4 rolling on the loop (bottom surface 1016). Point K1012 is the intersection of imaginary lines K10 and K1011. Imaginary line K1013 is a tangent to imaginary line K10 at point K1012. Imaginary line K1014 is a tangent to imaginary line K1011 at point K1012.

[0106] According to embodiment 1, the ball 4 and the tongue 40 (in) enter the circulation path 30 from the track 8. Figure 8 Not illustrated. See reference. Figure 5When the ball 4 contacts the tongue 40, its forward path changes to be radially inward than the tongue 40, entering the circulation path 30. Here, viewed from the axial direction, the trajectory of the ball 4 moving on the track 8 (outer peripheral track surface 13) (refer to imaginary line K10) is an arc. When the ball 4 contacts the tongue 40, its forward path bends radially inward than the imaginary line K10. The bending angle of this forward path of the ball 4 is θ11.

[0107] On the other hand, according to the comparative example, the bending angle of the ball 4 as it enters the circulation path (bottom surface 1016) from the track 8 (outer peripheral track surface 13) is θ1011. The bending angle θ1011 in the comparative example is greater than the bending angle θ11 in this embodiment. This is because, in the comparative example, the two ends 1016b of the bottom surface 1016 in the intersecting direction are concave radially inward. Based on the above, according to this embodiment, since the bending angle θ11 is smaller, the movement of the ball 4 between the track 8 and the circulation path 30 becomes smoother.

[0108] In summary, the ball screw device 1 of Embodiment 1 includes: a nut 6 having an inner peripheral track surface 6a on its inner peripheral surface; a screw shaft 2 passing through the nut 6 and having an outer peripheral track surface 13 on its outer peripheral surface; a plurality of balls 4 arranged on a track 8 between the outer peripheral track surface 13 and the inner peripheral track surface 6a; and at least one block 5 for circulating the balls 4. At least one recess 14 is provided on the outer peripheral surface of the screw shaft 2, recessed radially inward to accommodate the block 5. The recess 14 has a first bottom surface 16 facing radially outward. At least a portion of the first bottom surface 16 is planar. The block 5 has: a second bottom surface 50 that abuts against the first bottom surface 16; a circulation groove surface 51 that is recessed radially outward from the second bottom surface 50 and whose internal space forms a circulation path 30; a bottom opening 53 that opens the circulation path 30 radially inward; a pair of block side openings 31 that open the circulation path 30 circumferentially and connect the circulation path 30 to the track 8; and a pair of tongues 40 that guide the balls 4 entering the circulation path 30 from the track 8 radially inward. The portion of the first bottom surface 16 that blocks the bottom opening 53 becomes the rolling surface 54 of the balls 4 moving in the circulation path 30.

[0109] According to Embodiment 1, the ball 4 is reliably guided radially inward by the tongue 40. Therefore, it is possible to prevent the ball 4 from being trapped between the circulation groove surface 51 and the inner circumferential track surface 6a. Thus, the rolling of the ball 4 becomes smooth, and damage to the shoulder of the circulation groove surface 51 is avoided. Furthermore, the first flat bottom surface 16 can be used as a reference surface for dimensional management, making the manufacturing of the recess 14 easier. Additionally, since the circulation path 30 of the block 5 opens radially inward, the block 5 can be easily manufactured using a mold.

[0110] In addition, in embodiment 1, the entire first bottom surface 16 is a plane.

[0111] According to Embodiment 1, the first bottom surface 16 is easily formed. Furthermore, the bending angle of the ball 4's path when entering the circulation path 30 is small. Therefore, the ball 4 moves smoothly between the track 8 and the circulation path 30.

[0112] Furthermore, when viewed from the axial direction, the first bottom surface 16 of the ball screw device 1 in Embodiment 1 extends in the intersecting direction Y, intersecting with an imaginary line K1 extending radially outward from the center O1 of the screw shaft 2. The recess 14 has an annular inner peripheral surface 15 surrounding the block 5. The inner peripheral surface 15 has a pair of side surfaces (second opposing surfaces 18) that sandwich the block 5 from both sides of the intersecting direction Y.

[0113] According to Embodiment 1, it is possible to prevent the block 5 from moving along the intersecting direction Y and falling off the recess 14.

[0114] Next, other embodiments of the ball screw device will be described. Furthermore, in the following description, only the changes relative to Embodiment 1 will be explained.

[0115] (Implementation Method 2)

[0116] Figure 9 This is a top view of the recess of the ball screw device in Embodiment 2, viewed radially. Figure 10 This is a cross-sectional view obtained by cutting the ball screw device of Embodiment 2 along the track and circulation path. Furthermore, Figure 10 The imaginary line K16 is the first bottom surface 16 of Embodiment 1. The imaginary line K51 is the circulation groove surface 51 of Embodiment 1. Therefore, the loop 30 of Embodiment 1 is formed between the imaginary lines K16 and K51.

[0117] like Figure 9 As shown, the recess 14 of the screw shaft 2 in Embodiment 2 of the ball screw device 1A differs from that in Embodiment 1 of the ball screw device 1 in that it replaces the first bottom surface 16 and becomes the first bottom surface 16A. The first bottom surface 16A has a concave surface 201 located at the center 16a in the intersecting direction Y and two flat surfaces 202 located on both sides of the concave surface 201 in the intersecting direction Y.

[0118] like Figure 10 As shown, the concave surface 201 is formed in an arc shape when viewed from the axial direction, and it is concave radially inward as it approaches the central portion 16a in the intersecting direction. Furthermore, the central portion of the concave surface 201 connects to the imaginary line K16. That is, the central portion 16a of the concave surface 201 in the intersecting direction is a distance from the center O1 (… Figure 10 The distance (not shown in the figure) is the same as that of the first bottom surface 16 of Embodiment 1.

[0119] Furthermore, the block 5A of Embodiment 2 differs from the block 5 of Embodiment 1 in that it has a protrusion 251 that protrudes radially outward at the center of the circulation groove surface 51A along its length. Therefore, the circulation groove surface 51A has a shape corresponding to the first bottom surface 16A. In addition, the plane 202 extends along the axial direction and the intersecting direction in the same way as the first bottom surface 16 of Embodiment 1.

[0120] In summary, according to Embodiment 2, the circulation path 30A is not a straight line, but a path that sinks radially inward from the center in the length direction. In other words, the plane 202 of the first bottom surface 16A is positioned radially outward compared to the first bottom surface 16 (refer to imaginary line K16) in Embodiment 1. Therefore, the length of the outer peripheral track surface 13 is L longer than that in Embodiment 1 (refer to...). Figure 10 The amount of ball screw device 1A is increased, thus improving its load-bearing capacity.

[0121] Furthermore, flat surfaces 202 are provided at both ends of the first bottom surface 16A in the intersecting direction. Therefore, similarly to Embodiment 1, in Embodiment 2, the bending angle is smaller when entering from the track 8 into the circulation path 30A compared to the case where the entire first bottom surface 16 is concave. Therefore, in Embodiment 2, the ball bearing 4 also moves smoothly between the track 8 and the circulation path 30.

[0122] Furthermore, the concave surface 201 of Embodiment 2 is arc-shaped when viewed from the axial direction, but it may also be triangular in shape, and is not limited to the example shown in the embodiment.

[0123] (Implementation Method 3)

[0124] Figure 11 This is a cross-sectional view obtained by cutting the block and recess of the ball screw device in Embodiment 3 along the axial direction and radially. For example... Figure 11 As shown, the block 5B of the ball screw device 1B in Embodiment 3 differs from that in Embodiment 1 in that it has a rib 60 on the outer peripheral side where the protrusion 42 is provided. This rib 60 extends in the helical direction and is also provided on the outer peripheral surface of the tongue 40. According to Embodiment 3, the strength of the tongue 40 is increased by the rib 60, making the tongue 40 less prone to breakage.

[0125] The various embodiments have been described above, but this disclosure may also be a ball screw device as shown below.

[0126] (Implementation Method 4)

[0127] Figure 12 This is a cross-sectional view obtained by cutting the block and recess of the ball screw device in Embodiment 4 along the axial direction and radially. For example... Figure 12As shown, in the ball screw device 1C of Embodiment 4, the distance between the first bottom surface 16C and the center O1 is set as h. The distance from the center O1 to the thread tooth 6b of the nut 6 is set as R. The diameter of the ball 4 is set as Dw. When the distance L1 between the thread tooth 6b and the groove surface 43 (the part of the outer diameter surface 41 of the block 5C that is opposite to the thread tooth 6b of the nut 6) is 0.2 mm or more and 1.5 mm or less, and the wall thickness L2 of the block 5C (the wall thickness of the block 5C from the part of the outer diameter surface 41 that is opposite to the thread tooth 6b of the nut 6 (groove surface 43) to the circulation groove surface 51) is 0.3 mm or more and 1.0 mm or less, and the radial clearance L3 of the circulation path 30 is 0.05 × Dw or more and 0.25 × Dw or less, the distance h is expected to satisfy the following formula (2).

[0128] [Mathematical Expression 2]

[0129]

[0130] If the distance h satisfies equation (2), then the value of distance h is relatively large. That is, the first bottom surface 16C is arranged radially outward, and the track 8 becomes longer. Therefore, the load-bearing capacity of the ball screw device 1C is improved.

[0131] The above describes embodiments 1 to 4. Furthermore, the recess 14 in embodiments 1 to 4 has a pair of second opposing surfaces 18 that sandwich the block 5 from both sides in the intersecting direction Y (see reference). Figure 3 , Figure 4 However, this disclosure is not limited to such recesses. In the following embodiment 5, a recess without a pair of second opposing surfaces 18 will be described.

[0132] Figure 13 This is a perspective view of the recess and block in Embodiment 5. In the ball screw device 1D of Embodiment 5, the block 5D differs from Embodiment 1 in that it is exposed from the recess 14D of the screw shaft 2 in the intersecting direction Y. The details will be explained below.

[0133] Figure 14 This is a perspective view of the recess of the lead screw shaft in Embodiment 5. The recess 14D of the lead screw shaft 2 in Embodiment 5 differs from the recess 14 in Embodiment 1 in that it has a pair of openings 150, 150 that open towards both sides in the intersecting direction Y. That is, the recess 14D in Embodiment 5 does not have a pair of second opposing surfaces 18 that clamp the block 5 from both sides in the intersecting direction Y (see reference). Figure 3 , Figure 4 Therefore, the block 5D is exposed from the recess 14D in the intersecting direction Y. Furthermore, this disclosure sometimes refers to the pair of openings 150, 150 as two openings.

[0134] In addition, the recess 14D of Embodiment 5 has the same first bottom surface 16 and a pair of first opposing surfaces 17, 17 that are opposite each other in the axial direction as Embodiment 1.

[0135] One of the pair of openings 150, 150 opens on one side of the intersecting direction Y, and the other opens on the other side of the intersecting direction Y. In Embodiment 5, a pair of openings 150, 150 are formed, and the wall portion constituting a pair of second opposing surfaces 18 is removed. Therefore, the first bottom surface 16 and the pair of first opposing surfaces 17, 17 are enlarged in the intersecting direction Y compared to Embodiment 1. That is, the recess 14D is enlarged in the intersecting direction Y compared to the recess 14 in Embodiment 1. In addition, the block 5D of Embodiment 5 is also enlarged in the intersecting direction Y compared to the block 5 of Embodiment 1 (see reference). Figure 13 ).

[0136] Figure 15 This is a diagram showing the recess in embodiment 5 as viewed from the intersecting direction. (As shown...) Figure 15 As shown, when viewed from the intersecting direction Y, the opening 150 has a quadrilateral shape along the first bottom surface 16 and the pair of first opposing surfaces 17, 17. In other words, no protrusions or the like protruding into the opening 150 are formed on the first bottom surface 16 or the pair of first opposing surfaces 17, 17. Therefore, the block 5 can move along the first bottom surface 16 and the pair of first opposing surfaces 17, 17 in the intersecting direction Y.

[0137] Figure 16 yes Figure 15 A cross-sectional view along the XVI-XVI line. (See example...) Figure 16 As shown, according to Embodiment 5, the block 5D is inserted from the intersection direction Y of the recess 14D (see reference). Figure 16 Arrow A1), which allows the block 5D to be mounted in the recess 14D. Furthermore, in Embodiment 5, similar to the recess 14 in Embodiment 1, the block 5D is positioned radially outward from the recess 14D, and the block 5D is moved radially inward (see [reference]). Figure 16 Arrow A2) can also be used to mount the block 5D onto the recess 14D. Therefore, the options for the direction of mounting the block 5D are increased, and the mounting capability of the block 5D is improved.

[0138] Additionally, in Embodiment 1, the lead screw shaft side opening 13b is formed on the second opposing surface 18 (see reference). Figure 3 , Figure 4 On the other hand, such as Figure 14 As shown, in Embodiment 5, the lead screw shaft-side opening 13b is formed on the first bottom surface 16. Therefore, the two ends 16b of the first bottom surface 16 in the intersecting direction Y are removed due to the lead screw shaft-side opening 13b.

[0139] Figure 17This is a view of the block of Embodiment 5 from the second bottom surface side. Block 5D, like in Embodiment 1, has a second bottom surface 50 that abuts against the first bottom surface 16. In addition, a non-contact surface 160 that does not abut against the first bottom surface 16 is formed on a portion of the second bottom surface 50.

[0140] Figure 18 This is a cross-sectional view obtained by cutting the recess and the block of Embodiment 5 along a direction orthogonal to the axis direction, specifically along... Figure 15 A cross-sectional view of the recess and the block when the XVIII-XVIII line is cut through. (See attached image.) Figure 18 As shown, the non-contact surface 160 is disposed radially outside the external thread groove surface 213 of the lead screw shaft 2, and is separated from the external thread groove surface 213. Therefore, in embodiment 5, a portion of the block 5D is not disposed in the recess 14D, but is disposed radially outside the external thread groove surface 213. Hereinafter, the portion of the block 5D disposed radially outside the external thread groove surface 213 will be referred to as the recess outer wall portion 161. This recess outer wall portion 161 is formed at both ends of the block 5D in the intersecting direction Y (see reference). Figure 17 ).

[0141] Furthermore, the aforementioned external thread groove surface 213 refers to the thread groove surface formed when the outer peripheral surface of the lead screw shaft 2 is continuously cut in the helical direction to form the outer peripheral track surface 13. Therefore, the external thread groove surface 213 extends in the same helical direction as the outer peripheral track surface 13, but is not connected to the circulation path 30 of the block 5D. That is, no balls 4 are arranged on the external thread groove surface 213.

[0142] Even in the ball screw device 1D of embodiment 5 described above, the ball 4 is also affected by the tongue 40 (see reference). Figure 13 , Figure 18 It is reliably guided radially inward. Therefore, similar to Embodiment 1, the ball 4 is prevented from being trapped between the circulation groove surface 51 and the inner circumferential track surface 6a. In addition, the first opposing surface 17 of Embodiment 5 extends in the helical direction as described in Embodiment 1, but in this disclosure, the first opposing surface 17 may also extend in the intersecting direction Y. There is no particular limitation on the orientation (angle relative to the intersecting direction Y) of the extension of the first opposing surface 17.

[0143] Next, a modified example 1 in which a portion of the ball screw device 1D of embodiment 5 is deformed will be described.

[0144] (Variation Example 1)

[0145] Figure 19 This is a diagram showing the concave part and the block of deformation example 1 viewed from the intersecting direction. Figure 20This is a perspective view of the recessed portion of the lead screw shaft in Modified Example 1. In the ball screw device 1E of Modified Example 1, the recessed portion 14D differs from that in Embodiment 5 in that a pair of grooves 220, 220 recessed along the axial direction are formed on a pair of first opposing surfaces 17, 17. Furthermore, the block 5D of Modified Example 1 differs from that in Embodiment 5 in that a pair of protrusions 230, 230 projecting along the axial direction are formed on a pair of first side surfaces 25, 25. In this disclosure, the pair of first opposing surfaces 17, 17 are sometimes referred to as a pair of opposing surfaces. Additionally, the pair of first side surfaces 25, 25 are sometimes referred to as a pair of side surfaces.

[0146] like Figure 20 As shown, the groove 220 extends in the intersecting direction Y. Furthermore, the groove 220 extends to both ends of the first opposing surface 17 in the intersecting direction Y. And, both ends of the groove 220 in the intersecting direction Y are open in the intersecting direction Y. Figure 19 As shown, the size between a pair of first opposing surfaces 17, 17 is W1. The size between a pair of slots 220, 220 is W2, which is greater than W1 (W2 > W1).

[0147] Furthermore, the radial position of the groove 220 (height from the first bottom surface 16) is located at the innermost radial side of the first opposing surface 17. Therefore, the innermost radial end 220a of the groove 220 is connected to the first bottom surface 16.

[0148] The protrusion 230, when viewed from the intersecting direction Y, has the same shape as the groove 220. Furthermore, although not specifically illustrated, the protrusion 230 extends along the first side surface 25 in the intersecting direction Y. Figure 19 As shown, the radial position of the protrusion 230 is located at the innermost radial position in the first side surface 25. Therefore, the protrusion 230 is opposite to the groove 220 in the axial direction and enters the groove 220. Furthermore, in the embodiment, the protrusion 230 extends in the intersecting direction Y, but in this disclosure, it may not extend in the intersecting direction Y. In addition, the protrusion 230 may also extend discontinuously in the intersecting direction Y.

[0149] Regarding the thickness of block 5E along its axial direction, the thickness W3 between the pair of first side surfaces 25, 25 is less than or equal to the size W1 between the first opposing surfaces 17, 17 (W1 ≥ W3). Therefore, the pair of first side surfaces 25, 25 of block 5E are not sandwiched between the first opposing surfaces 17, 17.

[0150] The thickness W4 between the pair of protrusions 230, 230 is less than the size W2 between the pair of grooves 220, 220 (W2 > W4). Therefore, it is large enough to accommodate the pair of protrusions 230 within the pair of grooves 220, 220. In addition, the thickness W4 between the pair of protrusions 230, 230 is greater than the size W1 between the pair of first opposing surfaces 17, 17 (W4 > W1).

[0151] Regarding the installation method of block 5D in modified example 1, block 5D is first positioned in the intersecting direction Y of recess 14D. Next, a pair of protrusions 230, 230 are inserted into a pair of slots 220, 220, and block 5E is pressed into the recess 14D side. Thus, block 5D is installed in recess 14D.

[0152] According to Modification 1, even when a radially outward load is applied to the block 5D, the pair of protrusions 230, 230 are hooked onto the pair of grooves 220, 220. Therefore, the radially outward movement of the block 5D is restricted. Furthermore, in Modification 1, grooves 220 are formed on each of the pair of first opposing surfaces 17, 17, but in this disclosure, a groove 220 can also be formed on one of the pair of first opposing surfaces 17, 17. In such a case, the protrusion 230 housed in the groove 220 is formed on one of the pair of first side surfaces 25, 25.

[0153] Next, a modified example 2, which deforms modified example 1, will be described.

[0154] (Variation Example 2)

[0155] Figure 21 This is a diagram showing the concave portion and the block of deformation example 2 from the perspective of the intersection. For example... Figure 21 As shown, the ball screw device 1F of Modified Example 2 differs from that of Modified Example 1 in that the radial positions of a pair of grooves 220F, 220F and a pair of protrusions 230F, 230F are changed.

[0156] Specifically, a pair of grooves 220F, 220F of the recess 14D are disposed in the radial middle portion of the first opposing surface 17. Similarly, a pair of protrusions 230F, 230F are also disposed in the radial middle portion of the first side surface 25. In this modified example 2, the movement of the block 5D radially outward is also restricted in the same way as in modified example 1.

[0157] In the above-described variations 1 and 2, examples were given of having a pair of grooves 220, 220 and a pair of protrusions 230, 230 in order to restrict the movement of the block 5D radially outward. However, this disclosure may also be as shown in the following variation 3.

[0158] (Variation Example 3)

[0159] Figure 22This is a view of the recess and block in Modified Example 3 from the cross direction. In the ball screw device 1G of Modified Example 3, the block 5D differs from Embodiment 5 in that it is clamped by a pair of first opposing surfaces 17, 17 of the recess 14D. Specifically, a size W5 is formed between the pair of first opposing surfaces 17, 17. On the other hand, the thickness W6 of the block 5D in the axial direction (the size between the pair of first side surfaces 25, 25) is larger than the size W5 between the pair of first opposing surfaces 17, 17 before it is installed into the recess 14D. That is, the block 5D has an interference fit with respect to the pair of first opposing surfaces 17, 17 and is installed into the recess 14D by pressing. In summary, according to Modified Example 3, the movement of the block 5D radially outward and in the cross direction Y is restricted.

[0160] Furthermore, the block 5D in the aforementioned variations 1 and 2 may move in the intersecting direction Y. To limit the movement of the block 5D in the intersecting direction Y, the content of variation 3 can also be applied. Specifically, the thickness W3 between the pair of first side surfaces 25, 25 can be made larger than the size W1 between the first opposing surfaces 17, 17 (see reference). Figure 19 Therefore, block 5D has an interference fit in the axial direction relative to recess 14D. As a result, the movement of block 5D in the intersecting direction Y is restricted.

[0161] Furthermore, in order to limit the movement of the block 5D in modified examples 1 and 2 in the intersecting direction Y, this disclosure can also include modified examples 4 to 6, which will be described below. In addition, in the following description, the direction orthogonal to both the axial direction and the intersecting direction Y is defined as the orthogonal direction. Furthermore, the direction of the center O1 of the lead screw shaft 2 when viewed from the first bottom surface 16 is defined as the first orthogonal direction Z1 (see...). Figure 23 (etc.). The direction opposite to the direction of the center O1 of the lead screw shaft 2 when viewed from the first bottom surface 16 is designated as the second orthogonal direction Z2 (refer to...). Figure 23 wait).

[0162] (Variation Example 4)

[0163] Figure 23 This is a sectional view obtained by cutting along a direction orthogonal to the axis of deformation example 4, including the concave portion and the block. For example... Figure 23 As shown, in the ball screw device 1H of Modified Example 4, the difference from Modified Example 1 lies in the fact that the block 5D has a pressing portion 161H. This pressing portion 161H presses the outer wall portion 161 of the recess of the block 5D radially outward after the block 5D is mounted in the recess 14D (see Figure 161H). Figure 23 It is formed by the arrow A3.

[0164] In addition, in modified example 4, a pair of concave outer wall portions 161 are respectively extruded (in Figure 23Only one recessed outer wall portion 161 is shown in the diagram. (See reference...) Figure 17 Therefore, a pair of extrusion sections 161H are formed on both sides of the intersection direction Y of the block 5D (in Figure 23 Only one extrusion section 161H is shown in the figure.

[0165] The extrusion section 161H protrudes from the first bottom surface 16 in the first orthogonal direction Z1. Therefore, when a load in the intersecting direction Y is applied to the block 5D, the pair of extrusion sections 161H hook onto the external thread groove surface 213 of the loop. Thus, the movement of the block 5H in the intersecting direction Y is restricted.

[0166] Furthermore, in Modification 4, the outer wall portion 161 of the recess is extruded, but in this disclosure, the portion other than the outer wall portion 161 of the recess can also be extruded to form the extruded portion 161H. Additionally, in Modification 4, the extruded portion 161H is hooked onto the external thread groove surface 213 of the circuit, but in this disclosure, it can also be hooked onto the thread tooth 13a (outer peripheral surface) of the lead screw shaft 2. Furthermore, in Modification 4, a portion of the block 5D is extruded to deform (bend) it in the orthogonal direction, but in this disclosure, a portion of the block 5D can also be deformed in the axial direction to form the extruded portion 161H.

[0167] In addition, in Modification 4, after the block 5D is installed in the recess 14D, both ends of the block 5D in the intersecting direction Y are squeezed. However, in this disclosure, one end of the block 5D in the intersecting direction Y can be squeezed before the block 5D is installed in the recess 14D.

[0168] Furthermore, in Modification 4, a pair of extrusion portions 161H are formed at both ends of the intersecting direction Y of the block 5D, but in this disclosure, the extrusion portion 161H may be formed only at one end of the intersecting direction Y of the block 5D. In such a block 5D, during the manufacturing of the block 5D, a protrusion (not shown) that protrudes from the first bottom surface 16 toward the first orthogonal direction Z1 needs to be pre-formed on one side of the intersecting direction Y of the block 5D.

[0169] (Variation Example 5)

[0170] Figure 24 This is a diagram of the block in Deformation Example 5 as viewed from the second bottom surface. Figure 25 This is a cross-sectional view obtained by cutting the ball screw device of deformation example 5 along a direction orthogonal to the axis. For example... Figure 24 As shown, the block 5D in Modified Example 4 differs from Modified Example 1 in that it has a notch surface 162 that cuts the two ends of the block 5D in the intersecting direction Y into an arc shape. The notch surface 162 removes a pair of concave outer wall portions 161.

[0171] Furthermore, when viewed from an orthogonal direction, the notch surface 162 is larger than the opening 13b on the lead screw shaft side. Therefore, as Figure 25As shown, a portion of the first bottom surface 16 (the edge of the lead screw shaft side opening 13b) is not covered by the second bottom surface 50 of the block 5I.

[0172] Furthermore, Modification 5 differs from Modification 1 in that a pressing portion 163 is formed on the first bottom surface 16 of the recess 14D. After the block 5D is installed in the recess 14D, the pressing portion 163 is formed by pressing the edge of the lead screw shaft side opening 13b of the first bottom surface 16. In addition, although not specifically illustrated, the pressing portion 163 is formed at both ends of the first bottom surface 16 in the intersecting direction Y.

[0173] The extrusion section 163 protrudes from the first bottom surface 16 in the second orthogonal direction Z2. Therefore, when a load in the intersecting direction Y is applied to the block 5D, the pair of extrusion sections 163 hook onto the notch surface 162. Thus, the movement of the block 5D in the intersecting direction Y is restricted.

[0174] Furthermore, in Modification 5, the first bottom surface 16 is extruded, but in this disclosure, the thread 13a of the lead screw shaft 2 can also be extruded. Additionally, if the extruded portion 163 is formed in the thread 13a of the lead screw shaft 2, the notch surface 162 may not be formed in the block 5I. That is, this disclosure does not particularly limit the shape of the block. Furthermore, in Modification 5, a portion of the lead screw shaft 2 is extruded to deform (bend) it in an orthogonal direction, but in this disclosure, a portion of the lead screw shaft 2 can also be deformed in the axial direction to form the extruded portion 163.

[0175] In addition, in Modification 5, after the block 5D is installed in the recess 14D, a pair of extrusion portions 163 are formed on both sides of the cross direction Y of the block 5D. However, in this disclosure, one of the extrusion portions 163 can be formed before the block 5D is installed in the recess 14D.

[0176] Furthermore, in Modification 5, a pair of pressing portions 163 are formed on both sides of the intersecting direction Y of the block 5D, but in this disclosure, the pressing portion 163 may be formed only on one side of the intersecting direction Y of the block 5D. In such a recess 14D, during the manufacturing of the lead screw shaft 2, a protrusion (not shown) that protrudes from the first bottom surface 16 toward the second orthogonal direction Z2 needs to be pre-formed on one side of the intersecting direction Y of the block 5D.

[0177] (Variation Example 6)

[0178] Figure 26 This is a three-dimensional view of the concave part of variation example 6. Figure 27 This is a diagram of the block of Deformation Example 6 as viewed from the second bottom surface. Figure 28 yes Figure 26 Sectional view along lines XXVIII-XXVIII. (e.g.) Figure 26As shown, in the ball screw device 1J of Modified Example 6, there is a difference from Modified Example 1 in that two holes 240 are formed on the first bottom surface 16 of the recess 14D of the screw shaft 2. Additionally, as... Figure 27 As shown, in the block 5D of modified example 6, there are two protrusions 241 formed on the second bottom surface 50, which is different from modified example 1.

[0179] like Figure 28 As shown, protrusion 241 enters hole 240. Therefore, when a load in the intersecting direction Y is applied to block 5D, protrusion 241 hooks onto hole 240. Thus, the movement of block 5D in the intersecting direction Y is restricted.

[0180] Furthermore, regarding the mounting method of the block 5D, the block 5D is positioned in the intersecting direction Y of the recess 14D. Next, a pair of protrusions 230, 230 are inserted into a pair of slots 220, 220, pressing the block 5D into the recess 14D. At this time, the protrusion 241 is deformed by the pressure of the first bottom surface 16. Furthermore, when the protrusion 241 overlaps with the hole 240 in the orthogonal direction, the protrusion 241 returns to its original shape and enters the hole 240. Thus, the block 5D is mounted in the recess 14D. Additionally, the block of this disclosure is not limited to the aforementioned metal or resin materials, but in this modified example, a resin block that is easily elastically deformable is preferred.

[0181] Additionally, the two holes 240 and the two protrusions 241 are relative to the center C of the block 5D (see reference). Figure 4 The points are symmetrically arranged. Therefore, even when the block 5D is installed with the recess 14D rotated 180°, the protrusion 241 will enter the hole 240. Therefore, the block 5D has good installability.

[0182] Furthermore, in Modified Example 6, there are two holes 240 and two protrusions 241, but this disclosure requires only one or more holes 240 and protrusions 241, and is not limited to the number shown in the Modified Example. Additionally, this disclosure does not particularly limit the shape of the hole 240; for example, it can be a hemisphere, a frustum, a pyramid, a cone, or a pyramid.

[0183] The above descriptions of variations 4 to 6 have been provided, but the contents of variations 4 to 6 can also be applied to variation 3. This more reliably restricts the movement of the block in the intersecting direction Y.

[0184] The various embodiments and modifications have been described above, but the circulation groove surface 51 of this disclosure may also be a corner groove with a quadrilateral cross-sectional shape. Alternatively, the cross-sectional shape of the circulation groove surface 51 may also be a Gothic arc, and is not limited to the examples shown in the embodiments. In addition, in the ball screws of embodiments 1 to 4, the block may have an interference fit in the recess, and the block may be installed in the recess by pressing. Furthermore, the recess 14B of embodiment 5 and the modifications has two openings 150, 150, but the opening 150 of this disclosure may also be only one. That is, the recess may also have an opening only on one side in the intersecting direction Y.

[0185] Furthermore, this disclosure may also be a combination of the following structures. (1)

[0187] A ball screw device, wherein,

[0188] This ball screw device has the following features:

[0189] The nut has an inner circumferential track surface on its inner circumferential surface;

[0190] A lead screw shaft, which passes through the nut, has an outer peripheral track surface on its outer peripheral surface;

[0191] Multiple balls are disposed on a track between the outer peripheral track surface and the inner peripheral track surface; and

[0192] One or more blocks that cause the balls to circulate.

[0193] One or more recesses are provided on the outer circumferential surface of the lead screw shaft, the recesses being recessed radially inward to accommodate the block.

[0194] The recess has a first bottom surface facing radially outward.

[0195] At least a portion of the first bottom surface is a plane.

[0196] The block has:

[0197] The second bottom surface abuts against the first bottom surface;

[0198] The circulation groove surface is recessed radially outward from the second bottom surface, and the internal space forms a circulation path;

[0199] The bottom opening directs the circulation path toward the radially inward opening;

[0200] A pair of block side openings that allow the circulation path to open circumferentially and connect the circulation path to the track; and

[0201] A pair of tongues guide the balls that enter the circulation path from the track radially inward.

[0202] The portion of the first bottom surface that blocks the bottom opening becomes the rolling surface of the ball moving in the circulation path. (2)

[0204] According to the ball screw device described in (1), wherein,

[0205] The entire first bottom surface is a plane. (3)

[0207] According to the ball screw device described in (1), wherein,

[0208] When viewed from an axis parallel to the lead screw axis, the first bottom surface extends in an intersecting direction that intersects an imaginary line extending radially outward from the center of the lead screw axis.

[0209] A concave surface that is recessed radially inward is provided at the center of the first bottom surface in the intersecting direction.

[0210] A flat surface is provided on both sides of the intersection direction of the concave surface. (4)

[0212] According to any one of (1) to (3) the ball screw device, wherein,

[0213] The tongue is provided with ribs that protrude radially outward. (5)

[0215] According to any one of (1) to (4) the ball screw device, wherein,

[0216] When viewed from an axis parallel to the lead screw axis, the first bottom surface extends in an intersecting direction that intersects an imaginary line extending radially outward from the center of the lead screw axis.

[0217] The recess has an annular inner circumferential surface surrounding the block.

[0218] The inner circumferential surface has a pair of side surfaces that sandwich the block from both sides of the intersecting direction. (6)

[0220] The ball screw device according to any one of (1) to (5), wherein,

[0221] The distance from the center of the lead screw shaft to the thread of the nut is set as R, the diameter of the ball is set as Dw, the distance between the portion of the outer diameter surface of the block that is opposite to the thread of the nut and the thread of the nut is 0.2 mm or more and 1.5 mm or less, and the wall thickness from the portion of the outer diameter surface of the block that is opposite to the thread of the nut to the circulation groove surface is 0.3 mm or more and 1.0 mm or less, and the radial clearance of the circulation path is 0.05 × Dw or more and 0.25 × Dw or less, and the distance h between the first bottom surface and the center of the lead screw shaft satisfies the following formula (3).

[0222] [Mathematical Expression 3]

[0223] (7)

[0225] According to any one of (1) to (4) the ball screw device, wherein,

[0226] When viewed from an axis parallel to the lead screw axis, the first bottom surface extends in an intersecting direction that intersects an imaginary line extending radially outward from the center of the lead screw axis.

[0227] The recess has at least one opening in the intersecting direction.

[0228] The block is capable of moving along the first bottom surface in the intersecting direction. (8)

[0230] According to the ball screw device described in (7), wherein,

[0231] The recess has two openings.

[0232] The two openings are the opening on one side of the intersecting direction and the opening on the other side of the intersecting direction. (9)

[0234] According to the ball screw device described in (7) or (8), wherein,

[0235] The recess has a pair of opposing surfaces opposite each other in the axial direction.

[0236] The block has a pair of side surfaces facing the axis and opposite to the pair of opposing surfaces.

[0237] At least one of the pair of opposing surfaces is formed with a groove that is recessed in the axial direction and extends along the intersecting direction.

[0238] At least one of the pair of said sides has a protrusion that protrudes in the axial direction and is received in the groove. (10)

[0240] According to the ball screw device described in (9), wherein,

[0241] The groove is formed on both sides of the pair of opposing surfaces.

[0242] The protrusion is formed on both sides of the pair of sides. (11)

[0244] According to any one of (7) to (10) the ball screw device, wherein,

[0245] The recess has a pair of opposing surfaces opposite each other in the axial direction.

[0246] The block has an interference fit with respect to the pair of opposing surfaces and is held between the pair of opposing surfaces. (12)

[0248] According to any one of (7) to (11) the ball screw device, wherein,

[0249] The direction orthogonal to both the axial direction and the intersecting direction is defined as the orthogonal direction.

[0250] The direction in which the center of the lead screw shaft is positioned when viewed from the first bottom surface is defined as the first orthogonal direction.

[0251] At least one of the two ends of the block in the intersecting direction is formed with a pressing portion that protrudes from the first bottom surface into the first orthogonal direction. (13)

[0253] According to any one of (7) to (11) the ball screw device, wherein,

[0254] The direction orthogonal to both the axial direction and the intersecting direction is defined as the orthogonal direction.

[0255] The direction that is opposite to the direction in which the center of the lead screw axis is configured when viewed from the first bottom surface is designated as the second orthogonal direction.

[0256] A pressing portion is formed on the lead screw shaft, which is disposed on at least one side of the cross direction of the block and protrudes from the first bottom surface into the second orthogonal direction. (14)

[0258] According to any one of (7) to (11) the ball screw device, wherein,

[0259] One or more holes are formed on the first bottom surface.

[0260] A protrusion for entering the hole is formed on the second bottom surface.

[0261] Explanation of reference numerals in the attached figures

[0262] 1. 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H, 1J: Ball screw assembly; 2. Screw shaft; 4. Ball; 5. 5A, 5B, 5D: Block; 6. Nut; 6a. Inner circumferential track surface; 8. Track; 13. Outer circumferential track surface; 14. 14D. Recess; 15. Inner circumferential surface; 16. 16A. First bottom surface; 17. First opposing surface; 18. Second opposing surface; 13a. Thread tooth; 13b. Screw shaft side opening; 13c. End face; 13d. Partial end face; 25. First side surface; 26. Second side surface; 30. 30A. Circulation path; 31. Block side opening. ; 40, tongue; 41, outer diameter surface; 42, protrusion; 43, groove surface; 50, second bottom surface; 51, circulation groove surface; 53, bottom opening; 54, rolling surface; 60, rib; 100, brake caliper; 104, electric actuator; 120, housing; 150, opening; 160, non-contact surface; 161, outer wall of recess; 161H, 163, extrusion part; 162, notch surface; 201, concave surface; 202, flat surface; 213, external thread groove surface of the circuit; 220, 220F, groove; 230, 230F, protrusion; 240, hole; 241, protrusion; 251, convex part.

Claims

1. A ball screw device, wherein, This ball screw device has the following features: The nut has an inner circumferential track surface on its inner circumferential surface; A lead screw shaft, which passes through the nut, has an outer peripheral track surface on its outer peripheral surface; Multiple balls are disposed on a track between the outer peripheral track surface and the inner peripheral track surface; and One or more blocks that cause the balls to circulate. One or more recesses are provided on the outer circumferential surface of the lead screw shaft, the recesses being recessed radially inward to accommodate the block. The recess has a first bottom surface facing radially outward. At least a portion of the first bottom surface is a plane. The block has: The second bottom surface abuts against the first bottom surface; The circulation groove surface is recessed radially outward from the second bottom surface, and the internal space forms a circulation path; The bottom opening directs the circulation path toward the radially inward opening; A pair of block side openings that allow the circulation path to open circumferentially and connect the circulation path to the track; as well as A pair of tongues guide the balls that enter the circulation path from the track radially inward. The portion of the first bottom surface that blocks the bottom opening becomes the rolling surface of the ball moving in the circulation path.

2. The ball screw device according to claim 1, wherein, The entire first bottom surface is a plane.

3. The ball screw device according to claim 1, wherein, When viewed from an axis parallel to the lead screw axis, the first bottom surface extends in an intersecting direction that intersects an imaginary line extending radially outward from the center of the lead screw axis. A concave surface that is recessed radially inward is provided at the center of the first bottom surface in the intersecting direction. A flat surface is provided on both sides of the intersection direction of the concave surface.

4. The ball screw device according to any one of claims 1 to 3, wherein, The tongue is provided with ribs that protrude radially outward.

5. The ball screw device according to any one of claims 1 to 4, wherein, When viewed from an axis parallel to the lead screw axis, the first bottom surface extends in an intersecting direction that intersects an imaginary line extending radially outward from the center of the lead screw axis. The recess has an annular inner circumferential surface surrounding the block. The inner circumferential surface has a pair of side surfaces that sandwich the block from both sides of the intersecting direction.

6. The ball screw device according to any one of claims 1 to 5, wherein, The distance from the center of the lead screw shaft to the thread of the nut is set as R, the diameter of the ball is set as Dw, the distance between the portion of the outer diameter surface of the block that is opposite to the thread of the nut and the thread of the nut is 0.2 mm or more and 1.5 mm or less, and the wall thickness of the block from the portion of the outer diameter surface that is opposite to the thread of the nut to the circulation groove surface is 0.3 mm or more and 1.0 mm or less, and the radial clearance of the circulation path is 0.05 × Dw or more and 0.25 × Dw or less, and the distance h between the first bottom surface and the center of the lead screw shaft satisfies the following formula (1). 。 7. The ball screw device according to any one of claims 1 to 4, wherein, When viewed from an axis parallel to the lead screw axis, the first bottom surface extends in an intersecting direction that intersects an imaginary line extending radially outward from the center of the lead screw axis. The recess has at least one opening in the intersecting direction. The block is capable of moving along the first bottom surface in the intersecting direction.

8. The ball screw device according to claim 7, wherein, The recess has two openings, which are openings on one side of the intersecting direction and openings on the other side of the intersecting direction.

9. The ball screw device according to claim 7 or 8, wherein, The recess has a pair of opposing surfaces opposite each other in the axial direction. The block has a pair of side surfaces facing the axis and opposite to the pair of opposing surfaces. At least one of the pair of opposing surfaces is formed with a groove that is recessed in the axial direction and extends along the intersecting direction. At least one of the pair of said sides has a protrusion that protrudes in the axial direction and is received in the groove.

10. The ball screw device according to claim 9, wherein, The groove is formed on both sides of the pair of opposing surfaces. The protrusion is formed on both sides of the pair of sides.

11. The ball screw device according to any one of claims 7 to 10, wherein, The recess has a pair of opposing surfaces opposite each other in the axial direction. The block has an interference fit with respect to the pair of opposing surfaces and is held between the pair of opposing surfaces.

12. The ball screw device according to any one of claims 7 to 11, wherein, The direction orthogonal to both the axial direction and the intersecting direction is defined as the orthogonal direction. The direction in which the center of the lead screw shaft is positioned when viewed from the first bottom surface is defined as the first orthogonal direction. At least one of the two ends of the block in the intersecting direction is formed with a pressing portion that protrudes from the first bottom surface into the first orthogonal direction.

13. The ball screw device according to any one of claims 7 to 11, wherein, The direction orthogonal to both the axial direction and the intersecting direction is defined as the orthogonal direction. The direction that is opposite to the direction in which the center of the lead screw axis is configured when viewed from the first bottom surface is designated as the second orthogonal direction. A pressing portion is formed on the lead screw shaft, which is disposed on at least one side of the cross direction of the block and protrudes from the first bottom surface into the second orthogonal direction.

14. The ball screw device according to any one of claims 7 to 11, wherein, One or more holes are formed on the first bottom surface. A protrusion for entering the hole is formed on the second bottom surface.

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