Feed screw device

Abstract

To prevent intrusion of abrasion powder into a screwing part between a screw shaft and a nut of a feed screw device, to prevent early deterioration of the screw shaft and the nut.SOLUTION: A ball screw device 1 comprises a screw shaft 2, a nut 3, a swirl-stop pin 5 protruding from an outer peripheral surface of the screw shaft 2 toward an outer diameter, a guide groove 6a in which the swirl-stop pin 5 slides axially while engaging circumferentially, and a shielding member 10 arranged radially between the guide groove 6a and a male screw part 2a of the screw shaft 2. The shielding member 10 covers an axial region L of the guide groove 6a that overlaps with the male screw part 2a from an inner diameter side. The shielding member 10 can expand and contract in the axial direction in response to an axial movement of the screw shaft 2.SELECTED DRAWING: Figure 1

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. 11, 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, a 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, and a housing 110 that accommodates these. The nut 102 is driven to rotate by an electric motor 130, causing the screw shaft 101 to reciprocate in the axial direction (left and right direction in the figure).

[0004] The electric actuator described above is provided with a rotation prevention mechanism that restricts co-rotation of the screw shaft 101 caused by the rotation of the nut 102. Specifically, a rotation prevention pin 104 protruding from the outer circumferential surface on both sides in the diameter direction is provided at one end (the left end in the figure) of the screw shaft 101. A guide groove 105a extending in the axial direction is formed on the inner circumferential surface of a sleeve 105 fixed to the inner periphery of the housing 110. An end of the rotation prevention pin 104 provided on the screw shaft 101 is inserted into the guide groove 105a of the sleeve 105, and these engage with each other in the rotation direction to restrict the rotation of the screw shaft 101. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5982220 [Patent Document 2] Patent No. 6111043 Summary of the Invention [Problem to be solved by the invention]

[0006] In the above-mentioned ball screw device, when the screw shaft 101 moves in the axial direction, the anti-rotation pin 104 provided on the screw shaft 101 slides in the axial direction while being pressed against the guide groove 105a of the sleeve 105 in the circumferential direction. This sliding between the anti-rotation pin 104 and the guide groove 105a causes wear of the anti-rotation pin 104 or the guide groove 105a. If the wear powder generated at this time adheres to the male thread portion 101a of the screw shaft 101 and enters the screw-engaged portion between the screw shaft 101 and the nut 102, it may cause early deterioration of the screw shaft 101 and the nut 102.

[0007] For example, the above-mentioned Patent Document 2 discloses a technique in which a roller is provided on the anti-rotation pin and the roller is brought into rolling contact with the guide groove. In this case, wear can be suppressed compared to when the anti-rotation pin slides on the guide groove, but since some sliding occurs between the roller and the guide groove, the generation of wear powder cannot be completely prevented. For this reason, the concern of early deterioration due to the intrusion of wear powder into the screw-threaded portion between the screw shaft and the nut cannot be eliminated.

[0008] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to prevent wear powder from entering the threaded engagement portion between the screw shaft and the nut of a feed screw device, thereby preventing early deterioration of the screw shaft and the nut. [Means for solving the problem]

[0009] In order to solve the above-mentioned problems, the present invention provides a feed screw device having a screw shaft having a male threaded portion formed on its outer peripheral surface, a nut having a female threaded portion formed on its inner peripheral surface which screws into the male threaded portion directly or via a plurality of balls, a rotation prevention member protruding outward from the outer peripheral surface of the screw shaft, a guide portion with which the rotation prevention member slides in the axial direction while engaging in the circumferential direction, and a shielding member which covers an axial region of the guide portion that overlaps with the male threaded portion from the inner peripheral side and which can expand and contract in the axial direction as the screw shaft moves axially.

[0010] In this way, by covering the axial region of the guide portion that overlaps with the male thread portion with the shielding member from the inner diameter side, wear powder generated by sliding between the anti-rotation member and the guide portion is blocked by the shielding member, and this wear powder can be prevented from adhering to the male thread portion of the screw shaft arranged on the inner diameter side of the shielding member. Also, the axial region where the guide portion and the male thread portion overlap changes with the axial movement of the screw shaft, but by making the shielding member axially expandable and contractible with the axial movement of the screw shaft, the axial region of the guide portion that overlaps with the male thread portion can always be covered from the inner diameter side with the shielding member.

[0011] For example, the shielding member may have a plurality of plates that are relatively movable in the axial direction, and the axial ends of adjacent plates may be overlapped to make the shielding member expandable and contractible in the axial direction. In this case, if adjacent plates are provided with locking portions that engage with each other in the axial direction to restrict separation of the plates in the axial direction, separation of the adjacent plates in the axial direction can be prevented when the shielding member is extended in the axial direction.

[0012] Furthermore, when the shielding member is made up of a plurality of plates, the plate provided at one axial end can be fixed to a fixed member including a guide portion, and the plate provided at the other axial end can be attached to a rotation-prevention member. When the screw shaft moves in the axial direction, the rotation-prevention member and the plate at one axial end attached thereto move axially together with the screw shaft, while the plate at the other axial end is fixed to a fixed member, so that the shielding member made up of a plurality of plates expands and contracts in the axial direction. Effect of the Invention

[0013] As described above, according to the feed screw device of the present invention, adhesion of wear powder to the male thread portion of the screw shaft is prevented, thereby preventing the intrusion of wear powder into the threaded portion between the screw shaft and the nut, thereby preventing premature deterioration of the screw shaft and the nut. [Brief description of the drawings]

[0014] [Figure 1] 1 is a cross-sectional view of a ball screw device according to an embodiment of the present invention, showing a state in which a screw shaft is in a rear end position. [Diagram 2] FIG. 2 is a partially sectional perspective view of the ball screw device of FIG. [Diagram 3] FIG. 2 is a cross-sectional view taken along line AA in FIG. [Figure 4] FIG. 2 is a cross-sectional view taken along line BB in FIG. [Diagram 5] 2 is a cross-sectional view taken along line CC in FIG. 1. [Figure 6] FIG. 2 is a cross-sectional view taken along line DD in FIG. [Figure 7] FIG. 4 is a cross-sectional view of the ball screw device, showing a state in which the screw shaft is at a front end position. [Figure 8] FIG. 8 is a partially sectional perspective view of the ball screw device of FIG. [Figure 9] FIG. 11 is a cross-sectional view of a ball screw device according to another embodiment. [Figure 10] 10 is a partially sectional perspective view of the ball screw device of FIG. 9. [Figure 11] FIG. 1 is a cross-sectional view of a conventional ball screw device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0016] 1 and 2 show a ball screw device 1 as a feed screw device according to an 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 fixed member including a sleeve 6. The nut 3 is rotatably attached to a housing (not shown) of the linear actuator via a bearing (not shown). 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 an electric motor of the linear actuator, the rotational motion is converted into a 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".

[0017] A male threaded portion 2a consisting of a helical groove is formed on the outer peripheral surface of the screw shaft 2. Cylindrical surfaces 2b and 2c are formed on the outer peripheral surface of the screw shaft 2 in front of and behind the male threaded portion 2a, respectively. The cylindrical surfaces 2b and 2c have a smaller diameter than the groove bottom of the male threaded portion 2a. A female threaded portion 3a consisting of a helical groove is formed on the inner peripheral surface of the nut 3. 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.

[0018] 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 screw shaft 2 is inserted into the inner periphery of a sleeve 6 fixed to a housing. A guide groove 6a extending in the axial direction is formed on the inner circumferential surface of the sleeve 6. In this embodiment, the guide grooves 6a are provided on the inner circumferential surface of the sleeve 6 at two locations that are diametrically opposed to each other. A lid 7 that covers the front opening of the sleeve 6 is attached to the front end of the sleeve 6. The lid 7 is formed in a flat plate shape perpendicular to the axial direction, and a hole 7a through which the screw shaft 2 is inserted is provided in the axial center.

[0019] The anti-rotation pin 5 has, for example, a cylindrical shape (see FIG. 2). The anti-rotation pin 5 protrudes from the cylindrical surface 2c of the screw shaft 2 on both diametrical sides. The anti-rotation pin 5 is attached to a mounting hole 2d provided on the cylindrical surface 2c at the rear of the screw shaft 2 (see FIG. 1). In the illustrated example, the mounting hole 2d penetrates the screw shaft 2 in the diametrical direction, and one anti-rotation pin 5 protruding on one diametrical side and the other anti-rotation pin 5 protruding on the other diametrical side are fixed in the mounting hole 2d by, for example, press-fitting.

[0020] The anti-rotation pin 5 is formed of a material having a higher strength (tensile strength) than the sleeve 6. 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 strength 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 sintered metal having both of these as the main components.

[0021] A shielding member 10 is disposed radially between the guide groove 6a of the sleeve 6 and the male threaded portion 2a of the screw shaft 2. In this embodiment, the shielding member 10 has a first plate 11, a second plate 12, and a third plate 13. Each of the plates 11 to 13 is formed of a resin material or a metal material. The shielding member 10 is axially expandable and contractable. In this embodiment, the plates 11 to 13 move relative to each other in the axial direction, causing the shielding member 10 to expand and contract in the axial direction (see FIG. 7).

[0022] Of the plates 11 to 13, the first plate 11 provided at the front end is fixed to a fixing member including the sleeve 6 (see FIG. 1). In the illustrated example, the first plate 11 is fixed to the lid 7 that covers the front opening of the sleeve 6. Specifically, the front end of the first plate 11 is inserted into a slit 7b provided in the lid 7, and a bent portion 11a provided at the front end of the first plate 11 engages with the lid 7 in the axial direction, thereby restricting the rearward movement of the first plate 11. The method of fixing the first plate 11 to the lid 7 is not limited to this, and they may be fixed by, for example, crimping or welding.

[0023] The second plate 12 and the third plate 13 provided behind the first plate 11 are provided to be movable in the axial direction with respect to the sleeve 6. The third plate 13 is fixed to the anti-rotation pin 5 and moves in the axial direction together with the screw shaft 2. In this embodiment, as shown in Figs. 3 to 6, the sleeve 6 is provided with a plate guide portion 6b extending in the axial direction on the inner diameter side (the side closer to the screw shaft 2) of the guide groove 6a, and the plates 11 to 13 are arranged in the plate guide portion 6b. In this embodiment, the plates 11 to 13 have the same width, and the width of the plate guide portion 6b is larger than the guide groove 6a and slightly larger than the plates 11 to 13. This allows the second plate 12 and the third plate 13 to move in the axial direction while being guided by the plate guide portion 6b. The "width" here means the dimension in the direction perpendicular to both the axial direction of the screw shaft 2 and the axial direction of the anti-rotation pin 5 (the left-right direction in Figs. 3 to 6). Further, on the inner diameter side of the plate guide portion 6b, there is provided a long hole 6c which is narrower than the plate guide portion 6b and extends in the axial direction, but there is a gap between this long hole 6c and the anti-rotation pin 5, so that they do not slide.

[0024] Adjacent plates, i.e., the first plate 11 and the second plate 12, and the second plate 12 and the third plate 13, have their axial ends overlapping each other (see FIG. 1). That is, the first plate 11 to the third plate 13 are provided continuously without any gaps in the axial direction. Also, the width of each of the plates 11 to 13 is greater than the width of the guide groove 6a. Therefore, the shielding member 10 formed of the plates 11 to 13 covers the entire axial region L of the guide groove 6a that overlaps with the male thread portion 2a from the inner diameter side.

[0025] The rear end of the first plate 11 and the front end of the second plate 12 are provided with locking portions that engage with each other in the axial direction. In the illustrated example, the rear end of the first plate 11 is provided with a bent portion 11b facing inward as a locking portion, and the front end of the second plate 12 is provided with a bent portion 12a facing outward as a locking portion. When the second plate 12 moves rearward and the bent portion 12a at the front end of the second plate 12 engages with the bent portion 11b at the rear end of the first plate 11 from the front, further rearward movement of the second plate 12 is restricted. This restricts separation of the first plate 11 and the second plate 12 in the axial direction. Similarly, the rear end of the second plate 12 has an inwardly bent portion 12b as an engagement portion, and the front end of the third plate 13 has an outwardly bent portion 13a as an engagement portion. These bent portions 12b, 13a engage with each other in the axial direction, thereby regulating axial separation of the second plate 12 and the third plate 13.

[0026] When the nut 3 is driven to rotate by the electric motor, the rotational motion of the nut 3 is converted into linear motion of the screw shaft 2 via the balls 4, and the screw shaft 2 moves in the axial direction (forward or backward). At this time, the screw shaft 2 also tries to rotate in conjunction with the rotation of the nut 3, but the rotation prevention pin 5 provided on the screw shaft 2 engages with the guide groove 6a of the sleeve 6 in the circumferential direction (rotation direction), restricting the rotation of the screw shaft 2. In this state, the screw shaft 2 moves in the axial direction, causing the rotation prevention pin 5 to slide against the side surface of the guide groove 6a of the sleeve 6.

[0027] When the screw shaft 2 is at the rear end position, as shown in FIG. 1, the shielding member 10 (plates 11 to 13) is in a state of being stretched in the axial direction. When the screw shaft 2 moves forward from this state, as shown in FIGS. 7 and 8, the third plate 13 moves forward integrally with the anti-rotation pin 5, and when the screw shaft 2 moves forward further, the anti-rotation pin 5 abuts against the second plate 12 from the rear, and the second plate 12 moves forward. In this way, the third plate 13 and the second plate 12 move forward with the forward movement of the screw shaft 2, and the shielding member 10 is shortened in the axial direction. On the other hand, when the screw shaft 2 moves rearward from the front end position shown in FIGS. 7 and 8, the third plate 13 moves rearward integrally with the anti-rotation pin 5, and when the screw shaft moves rearward further, the bent portion 13a at the front end of the third plate 13 engages with the bent portion 12b at the rear end of the second plate 12, and the second plate 12 moves rearward. In this way, as the screw shaft 2 moves rearward, the third plate 13 and the second plate 12 move rearward, and the shielding member 10 is stretched in the axial direction (see FIG. 1).

[0028] When the screw shaft 2 is at the rear end position shown in FIG. 1, the inner diameter side of the guide groove 6a is covered by the shielding member 10 (plates 11-13) in the entire axial region L where the guide groove 6a and the male threaded portion 2a overlap in the radial direction, i.e., the entire axial region L from the front end of the guide groove 6a to the rear end of the male threaded portion 2a. In the illustrated example, since the third plate 13 of the shielding member 10 extends rearward beyond the anti-rotation pin 5, the shielding member 10 covers the axial region of the guide groove 6a including the anti-rotation pin 5 from the inner diameter side. Also, when the screw shaft is at the front end position shown in FIG. 7, the inner diameter side of the guide groove 6a is covered by the shielding member 10 (plates 11-13) shortened in the axial direction in the entire axial region L where the guide groove 6a and the male threaded portion 2a overlap in the radial direction.

[0029] As described above, regardless of the axial position of the screw shaft 2, the shielding member 10 is always disposed between the guide groove 6a and the male threaded portion 2a in the radial direction, and the axial region L of the guide groove 6a overlapping with the male threaded portion 2a is covered by the shielding member 10. In particular, in this embodiment, the space (plate guide portion 6b) communicating with the guide groove 6a and the male threaded portion 2a is shielded by the shielding member 10 over the entire axial region L (see Figs. 3 to 5). As a result, even if wear powder is generated by sliding between the guide groove 6a and the anti-rotation pin 5, the wear powder is blocked by the shielding member 10, so that the wear powder can be prevented from adhering to the male threaded portion 2a of the screw shaft 2. In addition, in the illustrated example, both ends of the shielding member 10 in the width direction (left and right directions in Figs. 3 to 6) are covered by the wall surface of the plate guide portion 6b, and only a small gap is provided between them, so that the wear powder can be prevented from entering through the gap between them. 1 and 7, when the screw shaft 2 is used with one guide groove 6a disposed above the screw shaft 2, wear powder generated by sliding between the upper guide groove 6a and the anti-rotation pin 5 falls by gravity, but this wear powder rides on the shielding member 10 and does not reach the male threaded portion 2a. In this way, by preventing the adhesion of wear powder to the male threaded portion 2a of the screw shaft 2, it is possible to prevent wear powder from entering the screwing portion between the male threaded portion 2a of the screw shaft 2 and the female threaded portion 3a of the nut 3 via the balls 4, and therefore it is possible to prevent a situation in which wear powder gets caught in the contact portions between the male threaded portion 2a and the female threaded portion 3a and the balls 4, causing deterioration of the surfaces of these portions.

[0030] 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.

[0031] In the above embodiment, among the plates 11 to 13 constituting the shielding member 10, the second plate 12 is not fixed to another member, so there is a concern that it may tilt within the plate guide portion 6b. Therefore, the plate guide portion 6b may be provided with a structure that prevents the second plate 12 from tilting. For example, the width of the third plate 13 is narrower than the width of the second plate 12, and the portion of the plate guide portion 6b that guides the second plate 12 (second plate guide portion) is wider than the portion of the plate guide portion 6b that guides the third plate 13 (third plate guide portion), thereby providing the plate guide portion 6b with a stepped structure that prevents the second plate 12 from tilting. The second plate guide portion is not limited to the above, and may have a structure that prevents the second plate 12 from tilting and stabilizes its posture.

[0032] The number of plates constituting the shielding member 10 is not limited to three, and may be two, four or more. For example, in the embodiment shown in Fig. 9, the shielding member 10 is made up of two plates. Specifically, the second plate 12 of the above embodiment is omitted, and the first plate 11 and the third plate 13 cover the entire axial region L of the guide groove 6a that overlaps with the male thread portion 2a from the inner diameter side.

[0033] The shielding member 10 is not limited to a plurality of plates, and may be configured to have, for example, a bellows portion that is expandable and contractible in the axial direction. Specifically, for example, the shielding member 10 having the bellows portion is disposed between the guide groove 6a and the screw shaft 2 in the radial direction, and the front end of the shielding member 10 is fixed to the cover 7 of the sleeve 6, while the rear end of the shielding member 10 is fixed to the anti-rotation pin 5. For example, one shielding member 10 having a bellows portion may be provided on each of the inner diameter sides of the upper guide groove 6a and the lower guide groove 6a. Alternatively, one shielding member 10 having a cylindrical bellows portion may be provided on the inner diameter sides of the upper and lower guide grooves 6a, i.e., on the outer periphery of the screw shaft 2.

[0034] In the above embodiment, the shielding members 10 are provided between the screw shaft 2 and two guide grooves 6a provided diametrically opposite to each other in the sleeve 6, but the present invention is not limited to this. For example, when the ball screw device 1 is used with one guide groove 6a disposed above the screw shaft 2 as shown in FIG. 1, the shielding member 10 may be provided only between the upper guide groove 6a and the screw shaft 2, and the shielding member 10 between the lower guide groove 6a and the screw shaft 2 may be omitted. This reduces the number of parts, thereby reducing costs.

[0035] In this case, wear powder generated by sliding between the lower guide groove 6a and the anti-rotation pin 5 accumulates in the guide groove 6a. Most of the wear powder accumulated in the lower guide groove 6a in this way remains downward due to gravity and does not adhere to the male thread portion 2a of the screw shaft 2, but some fine wear powder may fly up and adhere to the male thread portion 2a of the screw shaft 2. In addition, if the shielding member 10 is provided only in one guide groove 6a, the ball screw device 1 must be positioned so that the guide groove 6a with the shielding member 10 is on the upper side during assembly, which reduces the ease of assembly. From these points of view, it is preferable to provide the shielding members 10 between both the upper and lower guide grooves 6a and the screw shaft 2 as in the embodiment shown in FIG. 1.

[0036] 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.

[0037] In the above embodiment, the anti-rotation pin 5 and the guide groove 6a directly slide against 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 roller of the anti-rotation member and the guide groove are mainly in rolling contact, so the sliding resistance between them is reduced. However, the roller of the anti-rotation member and the guide groove are not always in rolling contact, but are temporarily in sliding contact and slide against each other. Wear powder generated by this sliding is blocked by the shielding member that covers the guide groove from the inner diameter side.

[0038] 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.

[0039] 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]

[0040] 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) 6b Plate guide part 7 Lid 10 Shielding material 11 First Plate 12 Second Plate 13 Third Plate

Claims

1. a nut having an internal thread formed on its internal surface and threadedly engaging with the external thread directly or via a plurality of balls; a rotation prevention member protruding from the external surface of the screw shaft toward the outer diameter; a guide portion with which the rotation prevention member slides in the axial direction while engaging in the circumferential direction; and a shielding member disposed radially between the guide portion and the external thread of the screw shaft, the shielding member covering an axial region of the guide portion that overlaps with the external thread from the inner diameter side and capable of expanding and contracting in the axial direction in accordance with axial movement of the screw shaft.

2. The shielding member has a plurality of plates that are relatively movable in the axial direction, 2. The feed screw device according to claim 1, wherein axial ends of the adjacent plates are overlapped with each other.

3. 3. The feed screw device according to claim 2, wherein adjacent plates are provided with locking portions for engaging with each other in the axial direction to restrict separation of the plates in the axial direction.

4. 3. The feed screw device according to claim 2, wherein among the plurality of plates, a plate provided at one axial end is fixed to a fixed member including the guide portion, and a plate provided at the other axial end is attached to the anti-rotation member.

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