Actuator and method of manufacturing actuator

Abstract

To suppress misalignment of a screw shaft caused by inclination of a fastening member.SOLUTION: An actuator includes: a housing; a nut held that rotates while being held directly or indirectly relative to the housing; a screw shaft that moves relative to the housing with the rotation of the nut; a sliding member that moves relative to the housing along a reference axis; a fastening member that engages with a fastening screw groove of the screw shaft to fasten the screw shaft to the sliding member; and a relaxation member formed from a pair of plate parts and a deformation part which is easier to deform than the plate parts and held by the pair of plates, the relaxation member being sandwiched by the sliding member and the fastening member.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present invention relates to an actuator and a method for manufacturing the actuator. [Background technology]

[0002] Patent Document 1 discloses an electric actuator in which a nut of a ball screw is rotated by a hollow motor to move the ball screw shaft forward in one axial direction or backward in the other axial direction. Patent Document 2 discloses a robot including a parallel link equipped with multiple drive units. The drive units include an actuator that drives a rod forward and backward, and a slider to which the tip of the rod is fixed and which guides the rod in one axial direction.

[0003] The robot in Patent Document 2 has multiple degrees of freedom due to the parallel link mechanisms connected in series, and its configuration including parallel links gives it superior precision and strength compared to general serial link robots, and it has been made smaller.

[0004] On the other hand, in a robot in which parallel links are connected in series, the tip working point is located at a distance from each actuator, and it is known that misalignment in each actuator has a significant impact on the positioning accuracy of the tip operation of the robot. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6632909 [Patent Document 2] Patent No. 7088440 Summary of the Invention [Problem to be solved by the invention]

[0006] To ensure accuracy in the amount of movement of the screw shaft, one possible procedure is to perform alignment adjustment to make the central axis of the screw shaft parallel to one axial direction, and then fix the screw shaft to the slider with a fastening member such as a nut. However, because extremely high precision is required for fastening the screw shaft to the slider, even a slight tilt of the fastening member due to distortion in the fastening screw groove that is less than the manufacturing tolerance or an imbalance in the worker's force can cause misalignment of the screw shaft and reduce positioning precision. That is, although fastening thread grooves are machined with a certain degree of precision, slight distortions within manufacturing tolerances are unavoidable, especially in small actuators, due to the small size of the components. Furthermore, because fastening members such as nuts are fastened using these fastening thread grooves, distortions in the thread grooves can cause the fastening members to tilt slightly. Furthermore, when workers tighten fastening members, it is difficult to apply perfectly uniform force around the screw axis, and a force imbalance can cause the fastening members to tilt slightly. A very small tilt of the fastening member causes a slight imbalance in the fastening force around the screw shaft, and this imbalance causes the central axis of the screw shaft to be slightly tilted relative to one axial direction, resulting in misalignment.

[0007] Therefore, an object of the present invention is to suppress misalignment of the screw shaft due to inclination of the fastening member. [Means for solving the problem]

[0008] In order to solve the above problems, one aspect of the actuator of the present invention comprises a housing, a nut that is held directly or indirectly relative to the housing and rotates, a screw shaft that moves relative to the housing as the nut rotates, a slide member that moves along a reference axis relative to the housing, a fastening member that engages with a fastening thread groove in the screw shaft to fasten the screw shaft to the slide member, and a relaxation member sandwiched between the slide member and the fastening member, which comprises a pair of plate portions sandwiched between them and a deformation portion that is more easily deformed than the plate portions.

[0009] According to such an actuator, even if the fastening member is tilted, the relaxation member suppresses imbalance in the fastening force, thereby suppressing misalignment of the screw shaft. In the actuator, it is preferable that the helical center of the fastening thread groove extends along the movement direction of the screw shaft, which suppresses misalignment of the screw shaft due to stress during fastening, compared to when the helical center extends in other directions.

[0010] In the actuator, the screw shaft preferably has the fastening screw groove at one end, which simplifies the configuration and contributes to miniaturization compared to when the screw shaft has the fastening screw groove at another location. In the actuator, the relaxation member preferably has outer surfaces facing in opposite directions and parallel to each other. By having the parallel outer surfaces of the relaxation member, the deformation portion deforms only when the fastening member is tilted, thereby suppressing imbalance in the fastening force.

[0011] Furthermore, in the actuator, it is preferable that the plate portion is made of metal and the deformation portion is made of resin, since this allows the buffer member to be made compact. In the actuator, the deformed portion is preferably hardened after fastening, which prevents misalignment over time caused by driving the actuator.

[0012] Preferably, the actuator further comprises a hollow motor fixed to the housing, and the nut is rotated by the hollow motor. The actuator can be made smaller in size by using a configuration in which the nut is rotated by the hollow motor. In the actuator, the nut and the screw shaft preferably form a ball screw, which improves the driving accuracy of the actuator.

[0013] In the actuator, the nut may be a torsion-type nut. Since misalignment is likely to be magnified in an actuator having a torsion-type nut, it is effective to suppress the misalignment using a relaxation member. In order to solve the above problems, one aspect of a manufacturing method for an actuator according to the present invention is for an actuator including a housing, a nut that is held directly or indirectly relative to the housing and rotates, a screw shaft that moves relative to the housing as the nut rotates, a slide member that moves along a reference axis relative to the housing, and a fastening member that engages with a fastening thread groove on the screw shaft to fasten the screw shaft to the slide member, the method comprising: a fastening process in which a relaxation member consisting of a pair of plate portions with a deformation portion that is easier to deform than the plate portions is sandwiched between the slide member and the fastening member, and the screw shaft is fastened to the slide member with the fastening member; and a hardening process in which the deformed portion is hardened after fastening with the fastening member.

[0014] According to this manufacturing method, even if the fastening member is tilted, the imbalance in the fastening force is suppressed by the relaxation member, and the fastening state is fixed while suppressing misalignment of the screw shaft, thereby realizing a highly accurate actuator. [Effects of the Invention]

[0015] According to the present invention, misalignment of the screw shaft due to inclination of the fastening member can be suppressed. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a perspective view of an actuator according to an embodiment of the present disclosure. [Figure 2] FIG. 1 is a side view of an actuator according to an embodiment of the present disclosure. [Figure 3] FIG. 2 is a cross-sectional view of the actuator along a reference axis. [Figure 4] FIG. 2 is a diagram showing a cross-sectional shape of the nut along the central axis of the nut. [Figure 5]FIG. 2 is a diagram showing a cross-sectional shape of the nut perpendicular to the central axis of the nut. [Figure 6] 10 is a schematic cross-sectional view of a nut and a screw shaft in a case where the central axis of the screw shaft is inclined with respect to a reference axis. FIG. [Figure 7] 10 is a schematic cross-sectional view of a nut and a screw shaft in which the first link groove is located on the side where the central axis of the screw shaft is inclined with respect to the reference axis. FIG. [Figure 8] 10A and 10B are diagrams illustrating a fixing structure between a screw shaft and a slide member. [Figure 9] 10 is a diagram schematically showing a state in which the fixing nut is inclined with respect to the central axis of the screw shaft. FIG. [Figure 10] 10A and 10B are diagrams illustrating other examples of the deformation portion. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, to avoid unnecessary redundancy in the following description and to facilitate understanding by those skilled in the art, more detailed description than necessary may be omitted. For example, detailed description of already well-known matters or redundant description of substantially identical configurations may be omitted. Furthermore, elements shown in earlier-described figures may be appropriately referenced in the description of later figures.

[0018] <Actuator> Fig. 1 is a perspective view of an actuator 1 according to an embodiment of the present disclosure. Fig. 2 is a side view of the actuator 1, and Fig. 3 is a cross-sectional view of the actuator 1 taken along a reference axis line SL. The reference axis line SL is a reference axis line of the actuator 1. Fig. 1 shows a state in which some of the components of the actuator 1 have been removed for ease of explanation of the interior of the actuator 1.

[0019] The actuator 1 includes a drive unit 10 and a guide unit 20 . <Drive unit> The driving unit 10 includes a housing 11, a motor 12, a nut 13, and a screw shaft 14. The housing 11 has, for example, a hollow rectangular parallelepiped shape extending along a reference axis SL.

[0020] As an example, motor 12 is a stepping motor and includes stator 12a and rotor 12b. Stator 12a is fixed inside housing 11. Motor 12 is a hollow motor, and rotor 12b is hollow, passes through stator 12a, and is rotatably supported relative to housing 11 by first bearing 15.

[0021] The nut 13 is rotatably supported relative to the housing 11 by a second bearing 16. The nut 13 is fixed to the hollow rotor 12b and rotates integrally with the rotor 12b. The configuration in which the nut 13 is rotated by the hollow motor allows the actuator 1 to be made smaller.

[0022] Fig. 4 is a diagram showing the cross-sectional shape of the nut 13 along the central axis CL1 of the nut 13. Fig. 5 is a diagram showing the cross-sectional shape of the nut 13 perpendicular to the central axis CL1 of the nut 13. As an example, the nut 13 is a toe-type nut. The nut 13 has a nut body 13a and four toe portions 13b.

[0023] 4 and 5 show a first frame portion 13b1, a second frame portion 13b2, a third frame portion 13b3, and a fourth frame portion 13b4. In the following description, when the first frame portion 13b1, the second frame portion 13b2, the third frame portion 13b3, and the fourth frame portion 13b4 are not distinguished from one another, they will be simply referred to as "frame portions 13b."

[0024] The nut body 13a has a cylindrical shape, and the screw shaft 14 passes through the nut body 13a. The nut body 13a has a spiral groove 13a1 on its inner circumferential surface, in which a plurality of balls B can roll. The screw shaft 14 has a spiral thread groove 14a on its outer circumferential surface, in which a plurality of balls B can roll.

[0025] The first link portion 13b1, the second link portion 13b2, the third link portion 13b3, and the fourth link portion 13b4 are arranged on the nut body 13a and are positioned spirally around the central axis CL1. That is, the first link portion 13b1, the second link portion 13b2, the third link portion 13b3, and the fourth link portion 13b4 are arranged in this order, for example, at equal intervals, in the direction along the central axis CL1. Also, the first link portion 13b1, the second link portion 13b2, the third link portion 13b3, and the fourth link portion 13b4 are arranged, for example, at equal intervals, in the direction around the central axis CL1.

[0026] Each of the link portions 13b faces the screw shaft 14 and has a link groove D that allows the ball B to ride up the threads of the screw shaft 14. The link grooves D of the first link portion 13b1, the second link portion 13b2, the third link portion 13b3, and the fourth link portion 13b4 are each positioned at equal intervals in the direction around the screw shaft 14.

[0027] The ball B rolling in the screw groove 14a of the screw shaft 14 moves through the groove D to another screw groove 14a adjacent to the screw groove 14a in the direction along the central axis CL1, thereby circulating the ball B within the nut 13. As the nut 13 is a top-type nut as an example as described above, the outer diameter of the nut 13 can be made compact, and it can also be used with a screw shaft 14 having a small lead (the amount of positional change in the thread groove 14a per one rotation of the screw shaft 14). In other words, the top-type nut 13 allows for more precise positioning of the screw shaft 14 than end deflector-type, tube-type, and end cap-type nuts.

[0028] 1 to 3, the screw shaft 14 is disposed with a first end portion disposed within the housing 11 and a second end portion exposed from the housing 11. The central axis CL2 of the screw shaft 14 is aligned so as to be parallel to the reference axis SL. The screw shaft 14 passes through the rotor 12b and the nut 13. As the nut 13 rotates, the screw shaft 14 moves linearly relative to the housing 11. The screw shaft 14 has a flange portion 14b that protrudes outward from the circumferential surface, and a stopper 14c is attached to the screw shaft 14.

[0029] <Guide section> The guide unit 20 guides the screw shaft 14 along the reference axis SL. The guide unit 20 includes a support body 21, a slide member 22, two guide rails 23a and 23b, four linear guides 24a, 24b, 24c, and 24d, and a linear encoder 25.

[0030] The support body 21 has a cylindrical shape with a square cross section that extends along the reference axis line SL, and is fixed to the housing 11. The slide member 22 has an L-shape and integrally includes a fixed portion 22a and a rectangular parallelepiped portion 22b. A second end of the screw shaft 14 is fixed to the fixed portion 22a. Therefore, the slide member 22 moves integrally with the screw shaft 14 relative to the housing 11. The rectangular parallelepiped portion 22b penetrates the support body 21 along the reference axis SL.

[0031] The fixed portion 22a has a through hole 22a1 through which the screw shaft 14 passes. The inner diameter of the through hole 22a1 is larger than the outer diameter of the screw shaft 14. In other words, the screw shaft 14 passes through the fixed portion 22a with a gap between it and the through hole 22a1. The two guide rails 23a, 23b extend along the reference axis SL and are fixed to the slide member 22 at positions opposite to each other with the rectangular parallelepiped portion 22b of the slide member 22 interposed therebetween.

[0032] The four linear guides 24a, 24b, 24c, and 24d are fixed within the support body 21 and guide the two guide rails 23a and 23b along the reference axis SL. Specifically, the first and second linear guides 24a and 24b are spaced apart from each other in the direction along the reference axis SL and guide the first guide rail 23a. The third and fourth linear guides 24c and 24d are also spaced apart from each other in the direction along the reference axis SL and guide the second guide rail 23b.

[0033] As described above, the support body 21 is fixed to the housing 11, and the guide rails 23a, 23b are fixed to the slide member 22. Therefore, the slide member 22 is movable along the reference axis SL relative to the housing 11 by the linear guides 24a to 24d. Also, as described above, the slide member 22 moves integrally with the screw shaft 14. Therefore, the guide portion 20 guides the screw shaft 14 along the reference axis SL.

[0034] The linear encoder 25 includes a scale 25a and a head 25b. The scale 25a is disposed on the slide member 22 along the reference axis SL. The scale 25a moves integrally with the screw shaft 14 relative to the housing 11. Meanwhile, the head 25b is disposed on the support 21 fixed to the housing 11, and detects the amount of movement of the scale 25a relative to the head 25b. In other words, the linear encoder 25 detects the amount of movement of the screw shaft 14 relative to the housing 11.

[0035] <Fastening with a fixing nut> The actuator 1 includes a fixing nut 18 as an example of a fastening member, and also includes a relaxation member 17. The screw shaft 14 has a fastening thread groove (not shown) at a second end thereof that engages with the fixing nut 18. When the fixing nut 18 engages with the fastening thread groove and is screwed together, the fixing nut 18 and flange portion 14b sandwich the relaxation member 17 and fixed portion 22a. As a result, the slide member 22 is fixed to the screw shaft 14, and the screw shaft 14 and slide member 22 move together.

[0036] The screw groove for fastening is coaxial with the screw groove 14a that moves the screw shaft 14. That is, The spiral center of the fastening thread groove extends along the movement direction of the screw shaft 14. Therefore, misalignment, which will be described later, when fastening the fixing nut 18 is suppressed compared to when the fastening thread groove is in another direction. In addition, because the fastening thread groove is provided at one end of the screw shaft 14, the fixing structure between the screw shaft 14 and the slide member 22 is simple and compact.

[0037] The procedure for fixing the slide member 22 to the screw shaft 14 is as follows: first, the screw shaft 14 is passed through the through hole 22a1 of the slide member 22. Then, with the screw shaft 14 passing through the through hole 22a1, alignment adjustment is performed to make the central axis CL2 of the screw shaft 14 parallel to the reference axis SL. After the alignment adjustment, the relaxation member 17 is sandwiched between the slide member 22 and the fixing nut 18 , and the screw shaft 14 is fastened to the slide member 22 by the fixing nut 18 .

[0038] As will be described in detail later, the relaxation member 17 relaxes the imbalance in fastening force that occurs when the fixing nut 18 is inclined when the fixing nut 18 is tightened. When the actuator 1 is in operation, a voltage is applied to the motor 12, causing the rotor 12b to rotate, and the nut 13 to rotate together with the rotor 12b, causing the screw shaft 14 to move relative to the housing 11. The screw shaft 14 also moves along the reference axis SL while being guided by the guide portion 20. The screw shaft 14 moves inward and outward from the housing 11 according to the rotation direction of the nut 13. When the screw shaft 14 moves inward from the housing 11, the movement of the screw shaft 14 is stopped at a position where the stopper 14c and the nut 13 come into contact.

[0039] <Misalignment and lead error> As described above, the alignment adjustment is performed so that the central axis CL2 of the screw shaft 14 and the reference axis SL are parallel to each other, so the amount of movement of the screw shaft 14 along the reference axis SL when the nut 13 rotates once is equal to the lead of the screw shaft 14.

[0040] On the other hand, if misalignment occurs in which the central axis CL2 of the screw shaft 14 is inclined relative to the reference axis SL, a so-called lead error occurs in which the amount of movement of the screw shaft 14 along the reference axis SL when the nut 13 rotates once is shorter than the lead of the screw shaft 14.

[0041] FIG. 6 is a schematic cross-sectional view of the nut 13 and the screw shaft 14 when the central axis CL2 of the screw shaft 14 is inclined with respect to the reference axis SL. As shown in Figure 6, when the central axis CL2 of the screw shaft 14 is inclined with respect to the reference axis SL, the larger the inclination angle, the smaller the amount of movement of the screw shaft 14 along the reference axis SL when the nut 13 makes one rotation, and the larger the lead error.

[0042] Furthermore, when the nut 13 is a top-type nut 13, the lead error may become large, as will be explained next. FIG. 7 is a schematic cross-sectional view of the nut 13 and the screw shaft 14 when the groove D of the first link portion 13b1 is located on the side where the central axis CL2 of the screw shaft 14 is inclined with respect to the reference axis SL.

[0043] As described above, the four link portions 13b of the nut 13 are arranged side by side along the central axis CL1 of the nut 13, and the link grooves D of the link portions 13b are positioned at equal intervals in the circumferential direction of the screw shaft 14. When the nut 13 rotates, the positions of the link grooves D of the link portions 13b also rotate.

[0044] As a result, when the groove of the first link portion 13b1 is present on the side to which the screw shaft 14 is inclined as shown in Fig. 7, the screw shaft 14 is further inclined toward the groove D from the state shown in Fig. 6. In other words, in the state shown in Fig. 7, the inclination angle of the screw shaft 14 is larger than in the state in which the groove D of the first link portion 13b1 is not present on the side to which the screw shaft 14 is inclined as shown in Fig. 6.

[0045] The larger the inclination angle of the screw shaft 14, the larger the lead error. Therefore, when the nut 13 is a top-type nut 13, particularly high accuracy is required for the parallelism of the central axis CL2 of the screw shaft 14 with respect to the reference axis SL.

[0046] <Fixing structure details> Here, the fixing structure between the screw shaft 14 and the slide member 22 will be described in detail. 8 and 9 are diagrams schematically showing the fixing structure between the screw shaft 14 and the slide member 22. Fig. 8 shows a state in which the fixing nut 18 is not inclined with respect to the central axis CL2 of the screw shaft 14, and Fig. 9 shows a state in which the fixing nut 18 is inclined with respect to the central axis CL2 of the screw shaft 14.

[0047] As described above, the screw shaft 14 is fixed to the slide member 22 by the fixing nut 18. When the fixing nut 18 is tightened to fix the screw shaft 14 to the slide member 22, it is required to tighten with high precision to avoid misalignment in which the central axis CL2 of the screw shaft 14 is tilted.

[0048] Furthermore, even if the lead error due to misalignment is small at the end of the screw shaft 14 of the actuator 1, it will cause a large operation error at the final operating point in a multi-axis actuator in which parallel links having the actuator 1 are connected in series in multiple stages. Therefore, when fixing the screw shaft 14 and the slide member 22 together, it is necessary to precisely fasten the fixing nut 18 so that even the slightest misalignment does not occur.

[0049] However, even if the fastening screw groove of the screw shaft 14 is created with high precision, particularly when the actuator 1 is miniaturized, the fixing nut 18 may be slightly tilted with respect to the central axis CL2 of the screw shaft 14 as shown in FIG. 9 due to distortions that are smaller than the manufacturing tolerances. That is, because the components of a small actuator are also small, slight distortion within manufacturing tolerances is unavoidable in the fastening thread groove. Since the fixing nut 18 is fastened using this fastening thread groove, distortion in the thread groove can cause the fixing nut 18 to tilt slightly. Furthermore, when an operator tightens the fixing nut 18, it is difficult to tighten it with perfectly uniform force around the screw axis, and an imbalance in force can cause the fixing nut 18 to tilt slightly.

[0050] If the fastening force becomes unbalanced around the screw shaft 14 due to the inclination of the fixing nut 18 relative to the central axis CL2 of the screw shaft 14, a force is generated in the direction of tilting the screw shaft 14. As a result, misalignment occurs in which the central axis CL2 of the screw shaft 14 is tilted, which may result in a lead error. However, the precise tightening work of the fixing nut 18, which does not allow even the slightest inclination due to distortion less than the manufacturing tolerance, takes time and effort, and reduces the assembly efficiency of the actuator 1.

[0051] Therefore, in the actuator 1, the imbalance in the fastening forces is alleviated by the relaxation member 17, thereby suppressing misalignment and lead error. This also improves the workability in tightening the fixing nut 18, and improves the assembly efficiency of the actuator 1.

[0052] The relaxation member 17 is a small member having a pair of plate portions 17a made of, for example, metal and a deforming portion 17b made of, for example, resin. The deforming portion 17b is sandwiched between the pair of plate portions 17a and is more easily deformed than the plate portions 17a. The deforming portion 17b may be an elastic or plastic body, but it is preferable that it harden after the fixing nut 18 is tightened.

[0053] The fastening force produced by tightening the fixing nut 18 is transmitted to the slide member 22 via the relaxation member 17. The outer surface of the relaxation member 17 is the surface of the plate portion 17a, and the outer surface on the fixing nut 18 side and the outer surface on the slide member 22 side are surfaced parallel to each other. Therefore, when the fixing nut 18 is tightened without tilting with respect to the central axis CL2, the deforming portion 17b is not deformed and fastening is completed as shown in FIG. 8. As a result, the slide member 22 is sandwiched between the fixing nut 18 and the flange portion 14b by a fastening force generated evenly around the screw shaft 14, and is fixed to the screw shaft 14 with high precision. Therefore, the central axis CL2 of the screw shaft 14 does not tilt, and misalignment and lead error are suppressed.

[0054] 9, when the fixing nut 18 is tilted with respect to the central axis CL2, the deformable portion 17b deforms to reduce the imbalance in the fastening force. Therefore, the fastening force transmitted to the plate portion 17a that is in contact with the slide member 22 becomes uniform around the screw shaft 14, and fastening is completed. As a result, even when the fixing nut 18 is tilted, the slide member 22 is fixed to the screw shaft 14 with high precision by the fastening force that is generated uniformly around the screw shaft 14. Therefore, even when the fixing nut 18 is slightly tilted due to distortion that is less than the manufacturing tolerance, the central axis CL2 does not tilt, and misalignment and lead error are suppressed.

[0055] Deformable portion 17b is made of, for example, a thermosetting resin, and is heated and hardened after fastening with fixing nut 18. This suppresses misalignment over time due to driving of actuator 1, and maintains a highly accurate positional relationship between screw shaft 14 and slide member 22. That is, the fixing procedure using the relaxation member 17 shown in Figures 8 and 9 involves a fastening process in which the relaxation member 17 is clamped between the slide member 22 and the fixing nut 18 and the screw shaft 14 is fastened to the slide member 22 with the fixing nut 18, and a hardening process in which the deformed portion 17b is hardened after fastening with the fixing nut 18.

[0056] FIG. 10 is a diagram showing another example of the deforming portion 17b. In the example shown in Figure 10, deforming portion 17b has deformed portion 17b1 and hardened portion 17b2. Deformed portion 17b1 is an elastic or plastic body, and deforms according to the inclination of fixing nut 18. Hardened portion 17b2 is, for example, a thermosetting resin, and is hardened by heating after fixing nut 18 is fastened. In the example shown in Figure 10, imbalances in fastening force are alleviated when fixing nut 18 is tightened, and after fastening, a highly accurate positional relationship between screw shaft 14 and slide member 22 is maintained.

[0057] In the above description, an example is shown in which the nut 13 and the screw shaft 14 form a ball screw, but the nut 13 and the screw shaft 14 may have a configuration other than a ball screw. However, when the nut 13 and the screw shaft 14 form a ball screw, the conversion efficiency from the rotation of the nut 13 to the movement of the screw shaft 14 is higher than in other configurations, and the driving accuracy is also higher.

[0058] Furthermore, in the above description, a top-type nut is exemplified as the nut 13, but it is not denied that any of an end deflector-type, tube-type, or end cap-type nut may be used as the nut 13. When the nut 13 is any of a top-type nut, end deflector-type nut, and tube-type nut, the axial length of the actuator 1 can be made smaller than when the nut 13 is an end cap-type nut.

[0059] Furthermore, in the above description, an example is shown in which the nut 13 has the link portion 13b and the link groove D is formed in the link portion 13b of the nut 13. However, the nut 13 may not have the link portion 13b, and the link groove D may be formed in the nut body portion 13a of the nut 13. Also, the nut 13 may not have the link portion 13b, and the link groove D may be formed in the screw shaft 14. When the link groove D is formed in the screw shaft 14, the balls B circulate by moving through the link groove D to the groove 13a1 of the adjacent nut 13 in the direction along the central axis CL1. When the nut 13 does not have the link portion 13b in this way, the number of parts of the nut 13 is reduced, thereby reducing the cost and size of the nut 13.

[0060] Furthermore, in the above description, an example has been given in which the fixing nut 18 is provided as a fastening member, but the actuator 1 may also be provided with a bolt as a fastening member. [Explanation of symbols]

[0061] 1... actuator, 10... drive unit, 11... housing, 12... motor, 13... nut, 13b... link portion, 14... screw shaft, 17... relaxation member, 18... fixing nut, 20... guide portion, 22... slide member, CL1... central axis of nut, CL2: Central axis of the screw shaft, SL: Reference axis

Claims

1. Housing and a nut that is held and rotated directly or indirectly relative to the housing; a screw shaft that moves relative to the housing by rotation of the nut; a slide member that moves along a reference axis relative to the housing; A fastening member that engages with a fastening thread groove of the screw shaft to fasten the screw shaft to the slide member; a relaxation member sandwiched between the slide member and the fastening member, the relaxation member being formed by sandwiching a deformation portion between a pair of plate portions, the deformation portion being more easily deformed than the plate portions; An actuator comprising:

2. The actuator according to claim 1 , wherein a center of the spiral of the fastening screw groove extends along the moving direction of the screw shaft.

3. The actuator according to claim 1 , wherein the screw shaft has the fastening screw groove at one end.

4. The actuator of claim 1 , wherein the damping member has opposing outer surfaces that are parallel and facing each other.

5. The actuator according to claim 1 , wherein the plate portion is made of metal and the deformation portion is made of resin.

6. The actuator according to claim 1 , wherein the deformation portion is hardened after fastening.

7. a hollow motor fixed to the housing; The actuator of claim 1 , wherein the nut is rotated by the hollow motor.

8. The actuator according to claim 1 , wherein the nut and the screw shaft form a ball screw.

9. The actuator according to claim 8, wherein the nut is a locking nut.

10. An actuator including a housing, a nut that is held directly or indirectly relative to the housing and rotates, a screw shaft that moves relative to the housing as the nut rotates, a slide member that moves along a reference axis relative to the housing, and a fastening member that engages with a fastening thread groove provided on the screw shaft to fasten the screw shaft to the slide member, a fastening process in which a relaxation member formed by sandwiching a deformation portion that is easier to deform than the plate portions between a pair of plate portions is sandwiched between the slide member and the fastening member, and the screw shaft is fastened to the slide member by the fastening member; a hardening process of hardening the deformed portion after fastening by the fastening member; A method for manufacturing an actuator having the above structure.

Images