Feed screw device and method for manufacturing linear motion member provided in the same

Abstract

To reduce the cost of a whirl-stop mechanism for a screw shaft of a feed screw device.SOLUTION: A male screw part 2a is formed on an outer peripheral surface of a screw shaft 2 in an area including a rear end, and a whirl-stop pin 5 protrudes toward an outer diameter from an area where the male screw part 2a is formed. The screw shaft 2 of a ball screw device 1 is provided with a groove 10 that opens onto an outer peripheral surface (male screw part 2a) and one axial end surface 2c, and the whirl-stop pin 5 is attached to the groove 10.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a feed screw device. [Background technology]

[0002] In recent years, electrification has progressed with the aim of reducing labor and improving fuel consumption in vehicles, etc., and systems have been developed and introduced to the market that use the power of electric motors to operate, for example, automatic transmissions, brakes, steering, etc. of automobiles. Known actuators used for such purposes include electric actuators equipped with feed screw devices (e.g., ball screw devices and sliding screw devices) that convert the rotational motion of an electric motor into linear motion.

[0003] For example, the following Patent Document 1 discloses an electric actuator having a ball screw device. As shown in Fig. 14, this ball screw device has a screw shaft 101 having a male thread portion 101a formed on its outer periphery, a nut 102 having a female thread portion 102a formed on its inner periphery, and a large number of balls 103 arranged between the male thread portion 101a of the screw shaft 101 and the female thread portion 102a of the nut 102. The screw shaft 101 reciprocates in the axial direction (left and right direction in the figure) by driving the nut 102 to rotate with an electric motor 130.

[0004] The electric actuator described above is provided with a rotation prevention mechanism that restricts the co-rotation of the screw shaft 101 caused by the rotation of the nut 102. Specifically, the rotation of the screw shaft 101 is restricted by engaging in the rotation direction between a rotation prevention pin 104 that protrudes on both sides in the diameter direction from one end (the left end in the figure) of the outer circumferential surface of the screw shaft 101 and a guide groove 105a that is provided in the sleeve 105 and extends in the axial direction. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5982220 Summary of the Invention [Problem to be solved by the invention]

[0006] The anti-rotation pin 104 is inserted into a through hole 101b that penetrates the screw shaft 101 in the diameter direction. Such a through hole 101b is machined, for example, by penetrating the screw shaft 101 in the diameter direction with a drill bit. At this time, if the drill bit is brought into contact with the male thread portion 101a of the screw shaft 101 from the radially outer side, the tip of the drill bit will come into contact with the inclined surface of the male thread portion 101a and the tip of the bit will escape in the axial direction, causing the axis of the drill bit to shift, which may reduce the machining accuracy of the through hole 101b.

[0007] 14, a cylindrical surface 101c where the male thread portion 101a is not formed is provided at one end of the outer peripheral surface of the screw shaft 101, and a through hole 101b is formed in this cylindrical surface 101c. By abutting a drill bit against such a cylindrical surface 101c from the diameter direction, the drill bit is less likely to become misaligned, and therefore a decrease in the machining accuracy of the through hole 101b can be avoided. There are two methods for forming the cylindrical surface 101c at one end of the outer peripheral surface of the screw shaft 101: (1) A male thread is formed by rolling only on a portion of the axial direction of the outer circumferential surface of the screw shaft, and the remaining axial region is left as a cylindrical surface. (2) After a male thread is formed by rolling over the entire axial area of ​​the outer circumferential surface of the screw shaft, a cylindrical surface is formed by machining a portion of the axial area. In the above method (2), the male thread can be continuously formed on a long shaft member by rolling (through-feed rolling), so when mass-producing threaded shafts, the above method (2) has a lower male thread machining cost than the above method (1). However, the above method (2) requires two steps, the rolling process of the male thread and the machining of the cylindrical surface, so the equipment cost and the number of steps are higher than the above method (1), and the advantage of the above male thread machining cost is diminished.

[0008] An object of the present invention is to reduce the cost of a rotation prevention mechanism for a screw shaft and thereby reduce the cost of a feed screw device. [Means for solving the problem]

[0009] In order to solve the above-mentioned problems, the present invention provides a feed screw device including a screw shaft having a male threaded portion formed on an outer peripheral surface thereof, a nut having a female threaded portion formed on an inner peripheral surface thereof and screwed with the male threaded portion directly or via a plurality of balls, a rotation prevention member protruding outward from a region of the outer peripheral surface of the screw shaft where the male threaded portion is formed, and a guide portion with which the rotation prevention member slides in an axial direction while engaging in a circumferential direction, The feed screw device has a groove formed on the screw shaft, the groove having an opening on the outer circumferential surface and on one axial end surface, and the anti-rotation member attached to the inner periphery of this groove.

[0010] As described above, in the feed screw device of the present invention, the screw shaft is provided with grooves that open on the outer circumferential surface and end surface of the screw shaft. Since such grooves have a higher degree of freedom in machining than through holes (see FIG. 14) that open only on the outer circumferential surface of the screw shaft, even when the grooves are provided in the region where the male thread portion of the screw shaft is formed, they can be machined by a method that does not cause misalignment of the tool. For example, if the grooves are formed by contacting the outer peripheral blade of a tool (e.g., an end mill) that rotates around an axis parallel to the axis of the screw shaft with the male thread portion of the outer circumferential surface of the screw shaft from the radially outer side, the decrease in machining accuracy of the grooves due to misalignment of the tool can be avoided. In this way, by forming a groove for attaching a rotation prevention member in the region of the outer circumferential surface of the screw shaft where the male thread portion is formed, it becomes unnecessary to form a cylindrical surface at one axial end of the outer circumferential surface of the screw shaft, and therefore the manufacturing cost of the screw shaft and therefore the manufacturing cost of the feed screw device are reduced.

[0011] In the feed screw device, it is preferable that the width of the opening of the groove at one axial end face of the screw shaft is made smaller than the width of the anti-rotation member. For example, the above configuration can be realized by gradually widening the width of the groove toward the other axial end. This makes it possible to prevent the anti-rotation member from falling off the opening of the groove.

[0012] If the shape of the inner surface of the groove formed in the screw shaft is different from the shape of the outer circumferential surface of the anti-rotation member that fits thereto, the entire circumference of the anti-rotation member cannot be supported by the inner surface of the groove. In this case, when the anti-rotation member and the guide part engage in the circumferential direction (the direction of rotation of the nut) and a circumferential load is applied to the anti-rotation member, the support of the anti-rotation member on the screw shaft may become unstable. Therefore, it is preferable to insert a fixing member into the gap between the groove and the anti-rotation member. In this way, when a circumferential load is applied to the anti-rotation member, the anti-rotation member is supported not only at the direct contact portion with the groove but also at the indirect contact portion via the fixing member, so that the support of the anti-rotation member is stable.

[0013] The anti-rotation member is preferably made of a material having a surface hardness greater than that of the locking portion.

[0014] When the anti-rotation member is press-fitted into the groove, the portion of the screw shaft surrounding the groove elastically deforms, and this elastic force presses the inner surface of the groove against the anti-rotation member, thereby firmly fixing the anti-rotation member to the screw shaft.

[0015] The linear motion member of the feed screw device can be manufactured through a process of forming a groove that opens on the outer peripheral surface and one end face in the axial direction of the screw shaft by contacting the male threaded portion of the outer peripheral surface of the screw shaft from the radially outward direction with a blade provided on the outer peripheral surface of the screw shaft, and a process of attaching the anti-rotation member to the groove. The inner surface of the groove of the screw shaft manufactured in this way has marks (machining scratches) cut by the outer peripheral blade of the tool that rotates around an axis parallel to the screw shaft. Effect of the Invention

[0016] As described above, according to the present invention, the manufacturing cost of the screw shaft is reduced, and therefore the cost of the feed screw device including the screw shaft is reduced. [Brief description of the drawings]

[0017] [Figure 1]2. FIG. 3 is a cross-sectional view (cross-sectional view taken along line XX in FIG. 2) of a ball screw device according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a front view of the ball screw device as viewed from a direction A in FIG. [Diagram 3] FIG. 2 is a partially sectional perspective view of the ball screw device. [Figure 4] FIG. 4 is a side view of a linear motion member of the ball screw device as viewed from a radial direction. [Diagram 5] 5 is an enlarged view of the rear end of the linear motion member of FIG. 4. [Figure 6] FIG. 2 is an exploded perspective view of the linear motion member. [Figure 7] 4A to 4C are diagrams illustrating a manufacturing process of a screw shaft. [Figure 8] FIG. 4 is a side view showing a method of forming a groove in a screw shaft. [Figure 9] FIG. 13 is a perspective view of a linear motion member according to another embodiment. [Figure 10] 10 is a side view of the linear motion member of FIG. 9 as viewed from the radial direction. [Figure 11] 11 is an enlarged view of the rear end of the linear motion member of FIG. 10. [Figure 12] FIG. 11 is a perspective view of a linear motion member according to still another embodiment. [Figure 13] FIG. 13 is an exploded perspective view of the linear motion member of FIG. [Figure 14] FIG. 1 is a cross-sectional view of a conventional ball screw device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0019] 1 to 3 show a ball screw device 1 as a feed screw device according to one embodiment of the present invention, which is incorporated in a linear motion type electric actuator (linear actuator). This ball screw device 1 has a linear motion member including a screw shaft 2, a rotating member including a nut 3, and a sleeve 6 as a fixed member. The nut 3 is rotatably attached to the housing of the linear actuator via a bearing. The sleeve 6 is fixed to the housing of the linear actuator. When the nut 3 of the ball screw device 1 is rotated by the electric motor of the linear actuator, the rotational motion is converted into linear motion of the screw shaft 2, and an object is operated at one axial end of the screw shaft 2 (the left end in FIG. 1). In the following, one axial side of the screw shaft 2 (the left side in FIG. 1) is referred to as the "front", and the opposite side (the right side in FIG. 1) is referred to as the "rear".

[0020] A male threaded portion 2a is formed on the outer peripheral surface of the screw shaft 2 (see Figs. 1 and 3). The male threaded portion 2a reaches the rear end of the outer peripheral surface of the screw shaft 2 (see Fig. 4). A cylindrical surface 2b is formed on the outer peripheral surface of the screw shaft 2 forward of the male threaded portion 2a. The cylindrical surface 2b has a smaller diameter than the groove bottom of the male threaded portion 2a. A female threaded portion 3a is formed on the inner peripheral surface of the nut 3 (see Fig. 1). A large number of balls 4 are arranged between the male threaded portion 2a of the screw shaft 2 and the female threaded portion 3a of the nut 3, and the male threaded portion 2a and the female threaded portion 3a are screwed together via the balls 4. The nut 3 is provided with a circulation mechanism (not shown) for circulating the balls 4.

[0021] The ball screw device 1 is provided with a rotation prevention mechanism that restricts the rotation of the screw shaft 2. The rotation prevention mechanism of this embodiment is composed of a rotation prevention pin 5 as a rotation prevention member attached to the screw shaft 2, and a guide groove 6a as a guide portion with which the rotation prevention pin 5 engages in the circumferential direction. In this embodiment, the guide groove 6a extending in the axial direction is formed on the inner peripheral surface of a sleeve 6 fixed to the housing (see FIG. 1). In this embodiment, the guide grooves 6a are provided at two diametrically opposed positions on the inner peripheral surface of the sleeve 6 (see FIG. 2). An area including the rear end of the screw shaft 2 is inserted into the inner circumference of the sleeve 6, and both ends of the rotation prevention pin 5 are disposed in the guide grooves 6a.

[0022] The anti-rotation pin 5 has, for example, a cylindrical shape (see FIG. 6). The anti-rotation pin 5 is attached to a groove 10 provided in the screw shaft 2 (see FIG. 4). The groove 10 is provided at the rear end of the screw shaft 2. The groove 10 opens to the rear end face 2c and the outer circumferential surface (male threaded portion 2a) of the screw shaft 2. The groove 10 in this embodiment penetrates the screw shaft 2 in the diameter direction and has a straight shape in the same direction. The anti-rotation pin 5 is inserted into the inner circumference of the groove 10, and both ends thereof protrude from the outer circumferential surface (male threaded portion 2a) of the screw shaft 2 on both sides in the diameter direction (see FIG. 2).

[0023] The anti-rotation pin 5 is formed of a material having a higher surface hardness than the sleeve 6. The surface hardness here refers to the Rockwell hardness defined in ISO 6508-1 (2015) or JIS Z 2245:2016. In this embodiment, the anti-rotation pin 5 is formed of a metal, for example, a steel material, specifically, a bearing steel. The sleeve 6 is formed of a metal having a lower surface hardness than the anti-rotation pin 5, for example, a sintered metal, specifically, a copper-based sintered metal having copper as the main component, an iron-based sintered metal having iron as the main component, or a copper-iron-based sintered metal having both of these as the main components.

[0024] As shown in FIG. 5, the width W of the opening of the groove 10 at the rear end surface 2c of the screw shaft 2 is smaller than the width (outer diameter D) of the anti-rotation pin 5. The "width" here refers to the dimension in the direction perpendicular to both the axis of the screw shaft 2 and the axis of the anti-rotation pin 5 (the vertical direction in FIG. 5, hereinafter referred to as the "width direction"). In the illustrated example, the inner surface of the groove 10 is provided with a pair of side surfaces 11 facing each other in the width direction and a bottom surface 12 connecting the front ends of the pair of side surfaces 11. Each side surface 11 and the bottom surface 12 are flat surfaces. The distance between the pair of side surfaces 11 gradually becomes wider toward the front end. That is, the groove 10 is trapezoidal in the side view shown in FIG. 5.

[0025] When the nut 3 is rotated by the electric motor, the screw shaft 2 moves in the axial direction. At this time, the end of the anti-rotation pin 5 and the guide groove 6a of the sleeve 6 engage in the circumferential direction (rotation direction), thereby restricting the rotation of the screw shaft 2. At this time, a circumferential load is applied to the anti-rotation pin 5, and this load is supported by the contact portion with the groove 10.

[0026] For example, if a columnar anti-rotation pin is press-fitted into a cylindrical through-hole, the anti-rotation pin is supported from the entire circumference, and therefore can be stably supported even when a circumferential load as described above is applied (see Fig. 14). In contrast, in this embodiment, as shown in Fig. 5, the shape of the outer peripheral surface of anti-rotation pin 5 (cylindrical surface) differs from the shape of the inner surface of groove 10 (trapezoid), so that groove 10 cannot support anti-rotation pin 5 from the entire circumference.

[0027] Therefore, in this embodiment, a fixed pin 7 serving as a fixing member is inserted into the gap between the anti-rotation pin 5 and the groove 10 to reinforce the support of the anti-rotation pin 5. In the illustrated example, the fixed pins 7 are disposed at both corners of the front end of the groove 10. The fixed pins 7 are disposed forward of a contact portion P between the anti-rotation pin 5 and a side surface 11 of the groove 10. The fixed pin 7 contacts the side surface 11 and bottom surface 12 of the groove 10 and the outer circumferential surface of the anti-rotation pin 5. In this case, the anti-rotation pin 5 is supported by the contact portion P with the side surface 11 of the groove 10 and the contact portion Q with the fixed pin 7, so that the support of the anti-rotation pin 5 is stable.

[0028] In particular, in this embodiment, the anti-rotation pin 5 and the fixed pin 7 are press-fitted into the inner circumference of the groove 10. As a result, the portions 2d of the screw shaft 2 provided on both sides of the groove 10 in the width direction are elastically deformed in the direction in which the width of the groove 10 increases (see the arrows in FIG. 5). Due to the elastic force of these portions 2d, the side surface 11 of the groove 10 is pressed against the outer circumferential surface of the anti-rotation pin 5, and the outer circumferential surface of the fixed pin 7 is pressed against the side surface 11 and bottom surface 12 of the groove 10 and the outer circumferential surface of the anti-rotation pin 5. In this way, the anti-rotation pin 5 is supported in a state in which it is pressed by the contact portion P with the side surface 11 of the groove 10 and the contact portion Q with the fixed pin 7, so that the support of the anti-rotation pin 5 is further stabilized and the anti-rotation pin 5 is firmly fixed to the groove 10.

[0029] When the screw shaft 2 moves in the axial direction, the anti-rotation pin 5 and the guide groove 6a of the sleeve 6 slide in the axial direction, so that the anti-rotation pin 5 and the guide groove 6a may wear. At this time, only a part of the outer peripheral surface of the anti-rotation pin 5 slides against the guide groove 6a in the circumferential direction, while the guide groove 6a slides against the anti-rotation pin 5 within the stroke range of the screw shaft 2. In this way, the anti-rotation pin 5 has a narrower sliding area than the guide groove 6a, and the worn parts are concentrated, so the amount of wear is likely to be large. In addition, when the anti-rotation pin 5 wears, the anti-rotation pin 5 becomes thin and is likely to be insufficient in strength, while even if the guide groove 6a of the sleeve 6 wears, the thickness of its both circumferential side portions 6b (see FIG. 2) is easily secured, so that the strength is unlikely to be insufficient. As described above, the anti-rotation pin 5 is more likely to be worn by sliding than the sleeve 6, and is more likely to be insufficient in strength due to wear. In this embodiment, the anti-rotation pin 5 is formed from a material having a higher surface hardness than the sleeve 6, so that wear of the anti-rotation pin 5 is suppressed and insufficient strength can be avoided.

[0030] A method for manufacturing the screw shaft 2 will now be described.

[0031] First, a long cylindrical bar 20 is prepared {see FIG. 7(A)} and a thread groove 21 is formed on the entire outer circumferential surface by rolling (e.g., rolling) {see FIG. 7(B)}. The bar 20 is then divided into a plurality of pieces to obtain a plurality of threaded shaft blanks 2' each having a thread groove 21 {see FIG. 7(C)}. Then, a cylindrical surface 2b is formed on one end (front end) of the threaded shaft blank 2' by machining (e.g., turning) {see FIG. 7(D)}. The thread groove 21 on the outer circumferential surface of each threaded shaft blank 2' other than the cylindrical surface 2b becomes the male thread portion 2a.

[0032] Then, the groove 10 is formed at the other end of the screw shaft blank 2'. The groove 10 is formed by machining. In this embodiment, as shown in FIG. 8, the groove 10 is formed in the screw shaft blank 2' by using an end mill 30. The blade 31 of the end mill 30 has the same shape as the groove 10 in a side view, and is trapezoidal in the illustrated example. Specifically, in a state where the axis of the end mill 30 is arranged parallel to the axis of the screw shaft blank 2', the end mill 30 is moved in a direction perpendicular to the axis while rotating around its own axis (see the arrow in FIG. 8). As a result, the outer peripheral blade 31 of the end mill 30 is brought into contact with the rear end of the outer peripheral surface of the shaft blank 2', and the shaft blank 2' is penetrated in the diameter direction while cutting the ridge portion of the male thread portion 2a. The inner surface (side surface 11 and bottom surface 12) of the groove 10 thus formed becomes a machined surface. More specifically, on the side surface 11 of the groove 10, numerous marks (machining lines) extending in a direction perpendicular to the axial direction are formed by the outer circumferential blade 31 of the end mill 30. Through the above, the screw shaft 2 having the groove 10 is completed.

[0033] Thereafter, the anti-rotation pin 5 and the fixed pin 7 are inserted into the groove 10 (see FIG. 3). Specifically, the anti-rotation pin 5 is inserted into the inner periphery of the groove 10, and then the fixed pin 7 is press-fitted into the gap between the anti-rotation pin 5 and the groove 10 of the screw shaft 2 with the anti-rotation pin 5 protruding from both sides in the diameter direction of the screw shaft 2, completing the linear motion member (see FIG. 4).

[0034] The present invention is not limited to the above embodiment. Other embodiments of the present invention will be described below, but redundant description of the same points as the above embodiment will be omitted.

[0035] The shape of the anti-rotation pin 5 is not limited to a cylinder. For example, in the embodiment shown in Figs. 9 and 10, the anti-rotation pin 5 is in the shape of a prism, more specifically, in the shape of a prism with a square cross section. Specifically, as shown in an enlarged view in Fig. 11, the front side surface 5a of the anti-rotation pin 5 having a prism shape is in contact with the bottom surface 12 of the groove 10 of the screw shaft 2, and the rear corner portion 5b of the anti-rotation pin 5 is in contact with the side surface 11 of the groove 10 of the screw shaft 2. The width C of the anti-rotation pin 5 is larger than the width W of the opening of the groove 10. In this embodiment, the anti-rotation pin 5 is press-fitted into the groove 10. That is, the front side surface 5a of the anti-rotation pin 5 is pressed against the bottom surface of the groove 10, and the rear corner portion 5b of the anti-rotation pin 5 is pressed against the side surface 11 of the groove 10. Furthermore, the fixing pin 7 is press-fitted between the anti-rotation pin 5 and the groove 10. That is, the outer peripheral surface of the fixing pin 7 is pressed against the side surface 11 and bottom surface 12 of the groove 10 and the side surface 5c of the anti-rotation pin 5 on one or the other side in the width direction.

[0036] 12 and 13, the portion 5d of the anti-rotation pin 5 that is inserted into the inner periphery of the groove 10 of the screw shaft 2 and the portion 5e that slides along the guide groove 6a have different shapes. Specifically, the portion 5d of the anti-rotation pin 5 that is inserted into the inner periphery of the groove 10 of the screw shaft 2 has a rectangular column shape, and the portion 5e that slides along the guide groove 6a has a cylindrical shape.

[0037] In the above embodiment, the fixed pin 7 is press-fitted into the gap between the anti-rotation pin 5 and the groove 10 of the screw shaft 2, but this is not limiting and the fixed pin 7 may be inserted into the gap by clearance fit. Even in this case, when a load is applied to the anti-rotation pin 5 and it is tilted with respect to the screw shaft 2, the anti-rotation pin 5 comes into contact with and is supported by the fixed pin 7. Furthermore, the fixed pin 7 may be omitted if not particularly necessary.

[0038] In the above embodiment, the guide groove 6a is formed in the sleeve 6, but the present invention is not limited to this. For example, the guide groove may be formed directly on the inner peripheral surface of the housing. Alternatively, a pair of guide members extending in the axial direction may be fixed to two diametrically opposed positions on the inner peripheral surface of the housing, and the guide groove 6a may be provided in each guide member.

[0039] In the above embodiment, the anti-rotation pin 5 and the guide groove 6a slide directly on each other, but the present invention is not limited to this. For example, the anti-rotation member may be composed of an anti-rotation pin and a roller disposed on its outer periphery, and the roller may be disposed in the guide groove. In this case, the contact between the roller of the anti-rotation member and the guide groove is mainly rolling contact, so that the sliding resistance between them is reduced.

[0040] In addition, in the above embodiment, the present invention is applied to a ball screw device 1, but the present invention can also be applied to a sliding screw device in which the male threaded portion 2a of the screw shaft 2 and the female threaded portion 3a of the nut 3 are directly screwed together without using balls.

[0041] The feed screw mechanism according to the present invention is not limited to being applied to an electric actuator, but can also be applied to a motion conversion mechanism (for example, a linear guide) that does not have an integrated drive unit. [Explanation of symbols]

[0042] 1. Ball screw device (feed screw device) 2 Screw shaft 2a Male thread 3 Nut 3a Female thread 4. Ball 5 Anti-rotation pin (anti-rotation component) 6 Sleeve 6a Guide groove (guide part) 7 Fixing pin (fixing member) 10 grooves 20 Bar material 30 End Mill 31 Blades

Claims

1. A feed screw device comprising: a threaded shaft having a male thread portion formed in an area including one axial end of an outer peripheral surface; a nut having a female thread portion formed in an inner peripheral surface thereof and screwed with the male thread portion directly or via a plurality of balls; a rotation prevention member protruding outward from the area of ​​the outer peripheral surface of the threaded shaft where the male thread portion is formed; and a guide portion with which the rotation prevention member slides in the axial direction while engaging in the circumferential direction, The feed screw device has a groove formed on the outer peripheral surface and one axial end surface of the screw shaft, and the anti-rotation member is attached to this groove.

2. 2. The feed screw device according to claim 1, wherein a width of an opening of the groove at one axial end face of the screw shaft is smaller than a width of the anti-rotation member.

3. 3. The feed screw device according to claim 2, wherein the width of the groove gradually increases toward the other axial side.

4. The shape of the inner surface of the groove is different from the shape of the outer circumferential surface of the anti-rotation member that fits therein, 2. The feed screw device according to claim 1, wherein a fixing member is inserted into a gap between said groove and said anti-rotation member.

5. 2. The feed screw device according to claim 1, wherein the rotation prevention member is made of a material having a surface hardness higher than that of the engaging portion.

6. 2. The feed screw device according to claim 1, wherein the inner surface of the groove is pressed against the anti-rotation member by the elastic force of the screw shaft.

7. 2. The feed screw device according to claim 1, wherein the inner surface of the groove has a cutting mark formed thereon by a peripheral blade of a tool that rotates about an axis parallel to the screw shaft.

8. A method for manufacturing a linear motion member of a feed screw device having a screw shaft having a male thread portion formed in an area including one end portion in an axial direction of an outer peripheral surface of the screw shaft, and a rotation prevention member protruding from the outer peripheral surface of the screw shaft to an outer diameter side, comprising: A step of forming a groove that opens on the outer peripheral surface of the screw shaft and one end face in the axial direction by contacting a blade provided on the outer periphery of a tool that rotates around an axis parallel to the axis of the screw shaft with a male thread portion on the outer peripheral surface of the screw shaft from the radially outer side; and attaching the anti-rotation member to the groove.

Images