Electric actuator

Abstract

To disclose an example of an electric actuator in view of solving a risk of a significant drive loss at a contact part between a shaft and a thrust bearing.SOLUTION: A thrust bearing is fixed to a housing 15 by a screw. A cap 16 as a rotation stopper of the thrust bearing is inserted into the housing 15, and rotation of the cap 16 is stopped by the housing 15 by a serration. Respective projections 16B, 15L configuring the serration are respectively provided with inclined faces 16C, 15M in which the cap 16 rotates only in a specific direction. This enables an appropriate management of a displacement of the thrust bearing, thereby suppressing a significant drive loss.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present disclosure relates to an electric actuator applied to a vehicle seat. [Background technology]

[0002] The electric vehicle seat includes an electric actuator as a drive source for displacing a portion of the seat. The electric actuator includes at least an electric motor, a shaft that is rotationally driven by the electric motor, and a gear fixed to the shaft.

[0003] When a shaft rotates, it rattles along the axial direction. To suppress noise caused by this rattle, for example, the invention described in Patent Document 1 is configured so that the position of the thrust bearing can be adjusted using an adjustment screw. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-330027 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the invention described in Patent Document 1, it is necessary to increase the tightening torque of the adjustment screw to prevent the adjustment screw from loosening. This increases the contact surface pressure between the shaft and the thrust bearing excessively, which may result in a large drive loss at the contact point between the shaft and the thrust bearing. The present disclosure discloses an example of an electric actuator that takes this into consideration. [Means for solving the problem]

[0006] An electric actuator for use in a vehicle seat, which includes an electric motor (11), a shaft (11A) that is driven to rotate by the electric motor (11), and a gear (12) fixed to the shaft (11A), preferably has at least one of the following components:

[0007] That is, the constituent features include a radial bearing (13) that contacts the outer peripheral surface of the shaft (11A) and rotatably supports the shaft (11A), a thrust bearing (14) that contacts the end (11B) of the shaft (11A) in the direction of the rotation center axis and restricts the shaft (11A) from being displaced in the direction of the rotation center axis, the thrust bearing (14) having a male screw portion (14A) that forms a spiral with the rotation center axis (Lo) as its center line, and a housing (15A) that houses at least the thrust bearing (14). The cap (16) is a cylindrical cap that is inserted into the storage section (15A) through an insertion opening (15J) and restricts the thrust bearing (14) from rotating around the central axis of rotation (Lo), and has an outer peripheral engaging section (16A) on its outer circumferential surface that engages with an engaged section (15K) provided on the inner circumferential surface of the housing (15), and an inner peripheral engaging section (17) on its inner circumferential surface that engages with the thrust bearing (14).

[0008] It is desirable that at least one of the tip side in the insertion direction of the outer peripheral engaging portion (16A) and the insertion opening (15N) side of the engaged portion (15K) is provided with an inclined surface (16C, 15M) inclined with respect to an imaginary line parallel to the rotation center axis (Lo), which generates a rotational force that rotates the cap (16) in a predetermined direction with the rotation center axis (Lo) as the center line when the cap (16) is inserted along the rotation center axis (Lo).

[0009] As a result, the thrust bearing (14) of the electric actuator does not move toward or away from the shaft (11A) unless the thrust bearing (14) rotates about the central rotation axis (Lo).

[0010] Furthermore, since the rotation of the thrust bearing 14 is restricted by the cap 16, the thrust bearing 14 does not move toward or away from the shaft 11A. Therefore, in this electric actuator, it is not necessary to excessively increase the tightening torque of the thrust bearing 14 relative to the housing 15.

[0011] Furthermore, since the contact surface pressure between the shaft (11A) and the thrust bearing (14) is prevented from becoming excessively large, the occurrence of large drive loss at the contact portion between the shaft (11A) and the thrust bearing (14) can be prevented.

[0012] In order to improve the ease of inserting the cap (16) into the storage section (15A), it is desirable to provide a tapered surface on at least one of the leading end side of the outer peripheral engaging section (16A) in the insertion direction and the insertion opening (15N) side of the engaged section (15K).

[0013] That is, if a tapered surface is provided, the outer peripheral engaging portion 16A is guided toward the engaged portion 15K when the cap 16 is inserted. However, if a tapered surface is provided, there is a risk that the cap 16 may rotate with respect to the housing 15 when the cap 16 is stored in the storage portion 15A.

[0014] When the cap (16) rotates relative to the housing (15), the thrust bearing (14) is displaced in the direction of the rotation axis in response to the rotation of the cap (16). In this case, for example, if the cap (16) rotates clockwise, the contact surface pressure between the shaft (11A) and the thrust bearing (14) may become excessively large.

[0015] Furthermore, for example, if the cap (16) rotates counterclockwise, the thrust bearing (14) may move away from the shaft (11A). As described above, the relationship between the thrust bearing (14) and the shaft (11A) varies greatly depending on the direction of rotation of the cap (16).

[0016] In contrast, the inclined surfaces (16C, 16M) associated with the electric actuator are configured to generate a rotational force that rotates the cap (16) in a predetermined direction when the cap (16) is inserted.

[0017] As a result, even if the relationship between the thrust bearing 14 and the shaft 11A changes due to the rotation of the cap 16 when the cap 16 is inserted, the change will be limited to within the range anticipated in advance at the design stage. Therefore, with this electric actuator, it is possible to ensure that the performance of the electric actuator will be within the range anticipated in advance at the design stage.

[0018] The electric actuator may have the following configuration, for example. In other words, it is desirable that the inclined surfaces (16C, 15M) are inclined with respect to the imaginary line so that when the tip side of the outer peripheral engaging portion (16A) in the insertion direction comes into contact with the insertion opening side of the engaged portion (15K), a rotational force is generated in a direction that loosens the screw engagement between the male thread portion (14A) and the female thread portion (15E).

[0019] As a result, the electric actuator can reliably prevent the contact surface pressure between the shaft (11A) and the thrust bearing (14) from becoming excessively large, and can therefore reliably prevent large drive losses from occurring at the contact point between the shaft (11A) and the thrust bearing (14).

[0020] Furthermore, it is desirable that the outer peripheral engaging portion (16A) and the engaged portion (15K) are configured in a serrated or splined shape having a plurality of protrusions (16B, 15L) extending in a direction parallel to the rotation center axis (Lo), and that the inclined surfaces (16C, 15M) are provided on the extension end sides of the protrusions (16B, 15L), and that the length (L1) of one widthwise end of the extension length of the protrusions (16B, 15L) is longer than the length (L2) of the other widthwise end of the extension length of the protrusions (16B, 15L), and that the direction from the one widthwise end to the other widthwise end coincides with the load direction (DL).

[0021] The normal rotation direction refers to the direction of rotation of the shaft 11A when the contact surface pressure between the shaft 11A and the thrust bearing 14 increases. The load direction (DL) refers to the normal rotation direction projected onto an imaginary plane including the rotation center axis (Lo). The width direction refers to the direction perpendicular to the extension direction of the protrusions 16B, 15L.

[0022] In the electric actuator having this configuration, when the shaft (11A) rotates in the normal direction, a rotational force in the normal direction acts on the thrust bearing (14) and the cap (16), and the ridges (16B, 16L) receive the rotational force.

[0023] In this case, in the electric actuator, the length (L1) of one widthwise end of the extension length of the protrusion (16B) provided on the cap (16) is longer than the length (L2) of the other widthwise end of the extension length of the protrusion (16B), and the direction from the one widthwise end to the other widthwise end coincides with the load direction (DL).

[0024] That is, in this electric actuator, the rotational force is received at one end of the ribs (16B, 15L) in the width direction, and therefore the area of the portion receiving the rotational force is larger than in a configuration in which the rotational force is received at the other end of the ribs (16B, 15L) in the width direction, resulting in stable performance of the electric actuator.

[0025] The housing (15) further includes a rotation restricting portion (17A) provided on the inner peripheral engaging portion (17) for restricting the rotation of the thrust bearing (14) around the central axis of rotation (Lo) relative to the cap (16), and a restricting engaging portion (14B) provided on the inner peripheral surface of the cap (16) and engaging with the rotation restricting portion (17A), the restricting engaging portion (14B) being provided in the range from the male thread portion (14A) to the non-contact end (14F), and it is desirable that the non-contact end (14F) side of the thrust bearing (14) be located outside the housing (15).

[0026] The contact end (14E) refers to the portion of the thrust bearing (14) that is in contact with the shaft (11A), and the non-contact end (14F) refers to the end of the thrust bearing (14) that is opposite the contact end (14E) in the direction of the rotational axis (Lo).

[0027] As a result, for example, when an assembly worker assembles an electric actuator, when the cap (16) temporarily fixed to the thrust bearing (14) is assembled into the housing 15, the rotation restricting portion (17A) engages with the restricting engaging portion (14B) before the outer peripheral engaging portion (16A) engages with the engaged portion (15K).

[0028] Furthermore, it is desirable that the cap (16) has a protrusion (17D) provided on the inner peripheral surface thereof on the contact end (14E) side, and an engaging portion (14C) provided on the non-contact end (14F) side of the thrust bearing (14), with the engaging portion (14C) into which the protrusion (17D) can fit and engage, and that when the protrusion (17D) is engaged in the engaging portion (14C) and the contact end (14E) of the thrust bearing (14) is in contact with the shaft (11A), the outer peripheral engaging portion (16A) and the engaged portion (15K) are in a disengaged state.

[0029] As a result, the cap (16) is temporarily fixed to the thrust bearing (14) in a position where the outer peripheral engaging portion (16A) does not interfere with the engaged portion (15K) until the male threaded portion (14A) of the thrust bearing (14) and the female threaded portion (15E) of the housing (15) are completely threaded together.

[0030] Incidentally, the symbols in each of the parentheses above are examples showing the correspondence with the specific configurations, etc. described in the embodiments described below, and the present disclosure is not limited to the specific configurations, etc. shown by the symbols in the parentheses above. [Brief explanation of the drawings]

[0031] [Figure 1] 1 is a diagram showing a vehicle seat according to a first embodiment. [Figure 2] FIG. 2 is an exploded view of the electric actuator according to the first embodiment. [Figure 3] 1 is a diagram showing the structure of an electric actuator according to a first embodiment. FIG. [Figure 4] 1 is a diagram showing the structure of an electric actuator according to a first embodiment. FIG. [Figure 5] FIG. 2 is a view showing a thrust bearing according to the first embodiment. [Figure 6] 2 is a view showing a bearing holder according to the first embodiment. FIG. [Figure 7] 3A and 3B are diagrams showing the structure of a housing according to the first embodiment. [Figure 8] FIG. 2 is a diagram showing a cap according to the first embodiment. [Figure 9] 3A and 3B are diagrams showing the structures of an outer circumferential engaging portion and an engaged portion according to the first embodiment. [Figure 10] 4 is a diagram showing a ridge 16A according to the first embodiment. FIG. [Figure 11] FIG. 2 is a diagram showing a cap according to the first embodiment. [Figure 12] 5A and 5B are views showing fitting of a cap and a thrust bearing according to the first embodiment. [Figure 13] FIG. [Figure 14] 1 is a diagram showing the structure of an electric actuator according to a first embodiment. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0032] The following "embodiments of the invention" are examples of embodiments that fall within the technical scope of the present disclosure. In other words, the invention-specific matters described in the claims are not limited to the specific configurations and structures shown in the following embodiments.

[0033] This embodiment is an example in which an electric actuator according to the present disclosure is applied to a seat (hereinafter referred to as a vehicle seat) mounted on a vehicle such as a car. Arrows and diagonal lines indicating directions are added to each figure to make it easier to understand the relationship between the figures and the shapes of components or parts.

[0034] Therefore, the electric actuator is not limited to the directions indicated in the drawings. The directions indicated in the drawings are directions when the vehicle seat according to the present embodiment is assembled to a vehicle. Diagonally shaded drawings do not necessarily represent cross-sectional views.

[0035] At least one component or part that is described with a reference symbol is provided unless otherwise specified, such as "one." In other words, unless otherwise specified, such as "one," two or more components may be provided.

[0036] The electric actuators shown in this disclosure include at least the components such as the members or sections numbered and described, and at least one of the structural sections shown. (First embodiment) <1. Overview of vehicle seats> As shown in FIG. 1, the vehicle seat 1 includes a seat cushion 2, a seat back 3, and at least one of a reclining device 4, a sliding device 5, a lifter device 6, and a tilt device .

[0037] The seat cushion 2 is a portion for supporting the buttocks of a seated occupant. The seat back 3 is a portion for supporting the back of the seated occupant. The seat back 3 is connected to the rear end side of the seat cushion 2 so as to be able to swing.

[0038] The reclining device 4 is a movable mechanism that swings the seat back 3 in the front-rear direction of the seat around the lower end side of the seat back 3. The sliding device 5 is a movable mechanism that slides the seat cushion 2 in the front-rear direction of the seat.

[0039] The lifter device 6 is a movable mechanism that raises and lowers the seat cushion 2. The tilt device 7 is a movable mechanism that swings the front end of the seat cushion 2 up and down. Each of the reclining device 4, the sliding device 5, the lifter device 6, and the tilt device 7 operates using an electric actuator 10 as a drive source.

[0040] <2. Electric Actuator Configuration> <2.1 Configuration Overview> As shown in FIG. 2, the electric actuator 10 includes at least an electric motor 11, a shaft 11A, a gear 12, a radial bearing 13, a thrust bearing 14, a housing 15, a cap 16, and the like.

[0041] <Shafts, gears> The shaft 11A is a shaft that is rotated by the electric motor 11. The electric motor according to this embodiment is an inner rotor type rotating electric machine in which a rotor (not shown) rotates inside. The shaft 11A is directly connected to the rotor.

[0042] The gear 12 is fixed to the shaft 11A and rotates integrally with the shaft 11A. The gear 12 according to this embodiment is configured as a worm, as shown in Fig. 3. The gear 12 meshes with a worm wheel that forms an output gear 12A.

[0043] Since the gear 12 according to this embodiment is configured as a worm, when a load acts on the gear 12, a thrust load and a radial load are generated on the shaft 11A. The thrust direction is a direction parallel to the central axis of rotation Lo of the shaft 11A. The radial direction is a direction perpendicular to the thrust direction.

[0044] <Bearings> Radial bearing 13 contacts the outer peripheral surface of shaft 11A to rotatably support shaft 11A. Radial bearing 13 is, for example, a sliding bearing that makes sliding contact with the outer peripheral surface of shaft 11A. Specifically, radial bearing 13 is a bush made of sintered metal.

[0045] 4, the thrust bearing 14 is in contact with the longitudinal end 11B of the shaft 11A. Therefore, the thrust bearing 14 constitutes a guide that restricts the shaft 11A from being displaced in the direction of the rotational center axis Lo.

[0046] As shown in Fig. 5, the thrust bearing 14 is provided with a male thread portion 14A. The male thread portion 14A is configured with a protrusion that describes a spiral with the central axis of rotation Lo as its center line. The thrust bearing 14 according to this embodiment is a sliding bearing made of resin.

[0047] <Housing> 4, the housing 15 is a casing having a storage section 15A that stores at least the thrust bearing 14. The housing 15 according to this embodiment includes a housing main body 15A and a bearing holder 15B.

[0048] The storage portion 15A is formed in the housing main body 15A. The bearing holder 15B is inserted and fixed into the housing main body 15A while holding the radial bearing 13. Specifically, the bearing holder 15B is provided with a holding portion 15C and a rotation stopper portion 15D.

[0049] The retaining portion 15C is a portion provided with a fitting hole into which the radial bearing 13 fits. As shown in Fig. 6, the rotation stopper portion 15D is a portion configured in a cylindrical shape, and is provided with a polygonal rotation stopper on the outer periphery side and with a female thread portion 15E on the inner periphery side.

[0050] As shown in Fig. 4, the female thread portion 15E is threadedly engaged with the male thread portion 14A of the thrust bearing 14. As shown in Fig. 7, the housing main body 15A is provided with a polygonal hole 15F that is congruent with the outer peripheral shape of the rotation stopper portion 15D.

[0051] This prevents the bearing holder 15B from rotating relative to the housing main body 15A around the central rotation axis Lo. The housing main body 15A is provided with a stepped portion 15G that serves as a stopper portion.

[0052] The longitudinal end of bearing holder 15B comes into contact with stepped portion 15G (see FIG. 4), thereby determining the position of bearing holder 15B in a direction parallel to rotation center axis Lo. Bearing holder 15B is press-fitted and fixed into a hole in housing main body 15A.

[0053] The press fit refers to, for example, a transition fit or an interference fit with an interference greater than 0. For this reason, a protruding crushed margin 15H (see FIG. 6) is provided on the outer circumferential surface of the retaining portion 15C. Note that both the housing body 15A and the bearing holder 15B according to this embodiment are made of resin.

[0054] <Cap> 4, the cap 16 is a cylindrical member that restricts the rotation of the thrust bearing 14 about the central rotation axis Lo. The cap 16 is inserted into the storage section 15A through an insertion opening 15J of the storage section 15A and attached to the storage section 15A.

[0055] <2.1 Cap attachment structure> <Connection structure between cap and housing> As shown in Fig. 8, an outer peripheral engaging portion 16A is provided on the outer peripheral surface of the cap 16. As shown in Fig. 7, an engaged portion 15K that engages with the outer peripheral engaging portion 16A is provided on the inner peripheral surface of the storage portion 15A.

[0056] The outer circumferential engaging portion 16A and the engaged portion 15K are engaged with each other (see FIG. 4), thereby preventing the cap 16 from rotating relative to the housing main body 15A around the central axis of rotation Lo.

[0057] As shown in Figures 7 and 8, the outer peripheral engaging portion 16A and the engaged portion 15K are each configured in a serration or spline shape having a plurality of protrusions 16B, 15L extending in a direction parallel to the rotation center axis Lo.

[0058] 9, inclined surfaces 16C and 15M are provided on the leading end side of the outer circumferential engaging portion 16A in the insertion direction and on the insertion opening 15N side of the engaged portion 15K. Each of the inclined surfaces 16C and 15M is a surface inclined with respect to an imaginary line parallel to the rotation center axis Lo.

[0059] 9 is a development view of the inclined surfaces 16C and 15M projected onto the inner peripheral surface of a virtual cylinder disposed on the outer periphery of the cap 16 and the storage section 15A. Therefore, the left-right direction in FIG. 9 coincides with the circumferential direction of the cap 16 and the storage section 15A.

[0060] That is, an inclined surface 16C is provided on the leading end side of each ridge 16B in the insertion direction (the lower end side of each ridge 16B in FIG. 9), and an inclined surface 15M is provided on the insertion opening 15N side of each ridge 15L (the upper end side of each ridge 15L in FIG. 9).

[0061] Each inclined surface 16C, 16M is inclined so as to generate a rotational force that rotates the cap 16 in a predetermined direction around the rotational axis Lo when the cap 16 is inserted along the rotational axis Lo.

[0062] That is, for example, in FIG. 9, when the cap 16 is displaced toward the housing 15 along the rotation central axis Lo and the inclined surfaces 16C and 15M come into contact with each other, the cap 16 rotates in the direction of the arrow R in FIG.

[0063] In this embodiment, the inclined surfaces 16C, 15M are inclined so that when the inclined surfaces 16C, 15M come into contact with each other, a rotational force is generated in a direction that loosens the engagement between the male thread portion 14A and the female thread portion 15E.

[0064] The maximum rotation angle of the cap 16 when inserted is a central angle corresponding to the width W of the protrusion 16B. In this embodiment, the cap 16 is configured so that the rotation angle of the cap 16 when inserted into the storage section 15A is, for example, 60 degrees or less.

[0065] As shown in FIG. 10, the length L1 of at least one widthwise end of the protrusion 16B provided on the cap 16 is longer than the length L2 of the other widthwise end of the protrusion 16B, and the direction from the one widthwise end to the other widthwise end coincides with the load direction DL.

[0066] The lengths L1 and L2 are the lengths in the extension direction of the ribs 16B. The width direction of the ribs 16B refers to the direction perpendicular to the extension direction of the ribs 16B. The load direction DL refers to the normal direction of rotation projected onto an imaginary plane (an imaginary plane parallel to the plane of FIG. 10) that includes the rotation center axis Lo.

[0067] The normal rotation direction refers to the direction of rotation of the shaft 11A when the contact surface pressure between the shaft 11A and the thrust bearing 14 increases. In Fig. 9, the normal rotation direction is the opposite direction to the arrow R. Each of the ridges 15L according to this embodiment has a similar shape to the ridges 16B.

[0068] <Cap and thrust bearing connection structure> 11, an inner peripheral engaging portion 17 is provided on the inner peripheral surface of the cap 16. The inner peripheral engaging portion 17 is a portion that engages with the thrust bearing 14, and performs at least two functions.

[0069] The first function is to restrict the cap 16 from rotating about the central axis of rotation Lo relative to the thrust bearing 14. The second function is to restrict the cap 16 from displacing in a direction parallel to the central axis of rotation Lo.

[0070] Specifically, the inner circumferential engaging portion 17 is configured to have at least a first engaging portion 17A, a second engaging protrusion 17B, and a third engaging protrusion 17C. The first engaging portion 17A and the third engaging protrusion 17C mainly perform a first function. The second engaging protrusion 17B mainly performs a second function.

[0071] <Details of the first function> The first engagement portion 17A is an example of a rotation restricting portion that restricts the thrust bearing 14 from rotating about the central rotation axis Lo relative to the cap 16. Specifically, the first engagement portion 17A is a polygonal (octagonal in this embodiment) fitting hole.

[0072] For this reason, thrust bearing 14 is provided with first engaged portion 14B (see FIG. 5) that engages with first engaging portion 17A. First engaged portion 14B is an example of a restrictive engaging portion. First engaged portion 14B is configured with a polygonal (octagonal in this embodiment) shaft portion that fits into a fitting hole that forms first engaging portion 17A.

[0073] 5, at least one slit 14D (in this embodiment, multiple slits) is provided on the longitudinal end of the thrust bearing 14 opposite the male thread portion 14A (the right end in FIG. 5). The slit 14D is a groove extending in a direction parallel to the rotation center axis Lo.

[0074] 12, the third engagement protrusions 17C provided on the inner peripheral surface of the cap 16 are fitted into the respective slits 14D, thereby restricting the thrust bearing 14 from rotating about the central rotation axis Lo relative to the cap 16.

[0075] When the outer circumferential engaging portion 16A engages with the engaged portion 15K, each third engaging protrusion 17C slides and displaces while fitted into the corresponding slit 14D. Since the thrust bearing 14 is provided with the slit portion 14D, the right end side easily deforms and narrows when the cap 16 is attached to the thrust bearing 14. This allows the operator to easily attach the cap 16 to the thrust bearing 14.

[0076] <Details of the second function> The second engagement protrusion 17B restricts displacement of the cap 16 in the direction of the rotational axis Lo relative to the thrust bearing 14. Specifically, the second engagement protrusion 17B is composed of at least one (two in this embodiment) protrusion that protrudes from the inner circumferential surface of the cap 16 toward the rotational axis Lo side.

[0077] 5, a second engaged portion 14C, which is an example of a fitting portion, is provided on the outer peripheral surface of thrust bearing 14. Second engaged portion 14C is provided at the longitudinal end of thrust bearing 14 on the opposite side to male thread portion 14A (the right end side in FIG. 5), and at a position facing second engaging protrusion 17B.

[0078] According to this embodiment, a plurality of second engaged portions 14C and a plurality of second engaging protrusions 17B (four in this embodiment) are provided, and each second engaged portion 14C is engaged with a second engaging protrusion 17B as shown in FIG.

[0079] Specifically, each second engaged portion 14C is a groove-shaped portion into which the opposing second engaging protrusion 17B can fit, and is a groove-shaped portion (see FIG. 5) extending in a direction perpendicular to the rotation center axis Lo.

[0080] Therefore, when the second engaging protrusions 17B facing each second engaged portion 14C are fitted in, as shown in Figure 4, the cap 16 is restricted from being displaced beyond a predetermined dimension in a direction parallel to the rotation center axis Lo.

[0081] <Configuration for temporarily fastening the cap to the thrust bearing> In the electric actuator 10 according to this embodiment, the thrust bearing 14 and the cap 16 are assembled to the housing 15 as a temporary assembly (also called a sub-assembly) shown in FIG.

[0082] In this temporary assembly, the cap 16 is temporarily fixed in a predetermined position on the thrust bearing 14. As shown in FIG. 8, a protrusion 17D is provided on the inner circumferential surface of the fitting hole that forms the first engagement portion 17A.

[0083] When the protrusion 17D fits into the second engaged portion 14C of the thrust bearing 14, it positions the cap 16 so as to temporarily fix it at a predetermined position on the thrust bearing 14. The predetermined position is, for example, a position that satisfies the following requirements (a) and (b).

[0084] Requirement (a): The cap 16 and the thrust bearing 14 are assembled to the housing 15 in a state where they are integrally assembled in advance, that is, in a state of a temporary assembly. Requirement (b): Until the male threaded portion 14A of the thrust bearing 14 is completely threaded with the female threaded portion 15E of the housing 15, the cap 16 is temporarily fixed to the thrust bearing 14 in a position where the outer peripheral engaging portion 16A does not interfere with the engaged portion 15K.

[0085] The above requirements (a) and (b) are specifically as follows: 13, second engaged portion 14C is provided on the non-contact end 14F side. Protrusion 17D is on the contact end 14E side of cap 16, can fit into and engage with second engaged portion 14C, and is provided at a position on the contact end 14E side with respect to second engaging protrusion 17B.

[0086] The contact end 14E refers to the portion of the thrust bearing 14 that is in contact with the shaft 11A. The non-contact end 14F refers to the end of the thrust bearing 14 that is opposite the contact end 14E with respect to the central rotation axis Lo. In FIG. 13, the contact end 14E side refers to the left side. In FIG. 13, the non-contact end 14F side refers to the right side.

[0087] When the protrusion 17D is fitted into the second engaged portion 14C, as shown in Figure 13, the first engaging portion 17A and the first engaged portion 14B are engaged, and the second engaging protrusion 17B and the second engaged portion 14C are in a disengaged state.

[0088] Furthermore, when the protrusion 17D is fitted into the second engaged portion 14C and the contact end 14E of the thrust bearing 14 is in contact with the longitudinal end 11B of the shaft 11A, the outer circumferential engaging portion 16A and the engaged portion 15K are in a disengaged state, as shown in Figure 14.

[0089] When the second engaging projection 17B is fitted into the second engaged portion 14C, that is, when the cap 16 and the thrust bearing 14 are completely assembled into the housing 15, the following state is achieved.

[0090] That is, the outer circumferential engaging portion 16A and the engaged portion 15K are engaged, the inner circumferential engaging portion 17 is engaged with the thrust bearing 14, and the protrusion 17D is crushed and comes into contact with the first engaged portion 14B.

[0091] <Engagement relationship for restricting thrust bearing rotation> The outer circumferential engaging portion 16A, the first engaging portion 17A, the first engaged portion 14B, and the engaged portion 15K are provided at positions that satisfy the following requirement (c).

[0092] That is, the requirement (c) is that "when the temporary assembly is attached to the housing 15, the first engaging portion 17A engages with the first engaged portion 14B before the outer circumferential engaging portion 16A engages with the engaged portion 15K."

[0093] Specifically, first engaged portion 14B according to this embodiment ranges from male thread portion 14A to non-contact end 14F, as shown in Fig. 13. When thrust bearing 14 is attached to housing 15, the non-contact end 14F side of thrust bearing 14 (second engaged portion 14C in this embodiment) is located outside housing 15, as shown in Fig. 4.

[0094] Therefore, when the protrusion 17D is fitted into the second engaged portion 14C, the first engaging portion 17A is engaged with the first engaged portion 14B, and the outer circumferential engaging portion 16A is disengaged from the engaged portion 15K, as shown in Fig. 14. Therefore, this embodiment has a configuration that satisfies the requirement (c).

[0095] <2.2 Thrust bearing and cap installation method (see Figure 2)> An operator (including an automatic assembly machine) mounts the temporary assembly, in which the protrusion 17D is fitted into the second engaged portion 14C, onto the housing 15 to which the electric motor 11 is mounted.

[0096] In other words, in this temporary assembly, the cap 16 is temporarily fixed to the thrust bearing 14 in a position where the outer engaging portion 16A does not interfere with the engaged portion 15K until the male threaded portion 14A of the thrust bearing 14 is completely threaded with the female threaded portion 15E of the housing 15.

[0097] Next, the worker applies electricity to the electric motor 11 to rotate the shaft 11A, while tightening the male thread portion 14A of the thrust bearing 14 into the female thread portion 15E of the housing 15. Note that, because the first engaging portion 17A and the first engaged portion 14B are engaged, the worker can tighten the male thread portion 14A into the female thread portion 15E by rotating the cap 16.

[0098] Then, when the current value of the electric motor 11 exceeds a predetermined threshold value (hereinafter referred to as the tightening stop current value), the worker stops the rotation of the thrust bearing 14 and ends the tightening work of the thrust bearing 14.

[0099] At the end of the tightening operation, first engaging portion 17A is engaged with first engaged portion 14B, and outer circumferential engaging portion 16A is not engaged with engaged portion 15K. In other words, in this embodiment, first engaging portion 17A engages with first engaged portion 14B before outer circumferential engaging portion 16A engages with engaged portion 15K.

[0100] Next, the worker engages the outer engaging portion 16A of the cap 16 with the engaged portion 15K of the housing 15, and inserts and attaches the cap 16 into the housing 15 so that each third engaging protrusion 17C of the cap 16 fits into each slit 14D.

[0101] 3. Features of the electric actuator according to this embodiment In this embodiment, since each ridge 16B engages with the corresponding ridge 15L, the thrust bearing 14 does not move toward or away from the shaft 11A unless the thrust bearing 14 rotates around the central rotation axis Lo.

[0102] Furthermore, because the rotation of the thrust bearing 14 is restricted by the cap 16, the thrust bearing 14 does not move toward or away from the shaft 11A. Therefore, in this embodiment, the tightening torque of the thrust bearing 14 to the housing 15 does not need to be excessively large.

[0103] Furthermore, since the contact surface pressure between the shaft 11A and the thrust bearing 14 is prevented from becoming excessively large, the occurrence of large drive loss at the contact portion between the shaft 11A and the thrust bearing 14 can be prevented.

[0104] Incidentally, in order to improve the ease of inserting cap 16 into storage portion 15A, it is desirable to provide a tapered surface for guiding purposes on each of protrusions 16B, 15L. However, if a tapered surface is provided, there is a risk that cap 16 may rotate with respect to housing 15 when cap 16 is stored in housing 15.

[0105] When cap 16 rotates relative to housing 15, thrust bearing 14 is displaced in the direction of the central axis of rotation. At this time, for example, if cap 16 rotates clockwise, the contact surface pressure between shaft 11A and thrust bearing 14 may become excessively large.

[0106] Furthermore, for example, if the rotation direction of cap 16 is leftward, there is a risk that thrust bearing 14 will separate from shaft 11A. As such, the relationship between thrust bearing 14 and shaft 11A varies greatly depending on the rotation direction of cap 16.

[0107] In contrast to this, the inclined surfaces 16C and 16M according to this embodiment are configured so that when the cap 16 is inserted, a rotational force is generated that rotates the cap 16 in a predetermined direction.

[0108] As a result, even if the relationship between the thrust bearing 14 and the shaft 11A changes due to the rotation of the cap 16 when the cap 16 is inserted, the change will remain within the range anticipated in advance at the design stage. Therefore, according to this embodiment, it is possible to ensure that the performance of the electric actuator 10 will be within the range anticipated in advance at the design stage.

[0109] The inclined surfaces 16C and 15M are inclined so that when the ridges 16B and ridges 15L come into contact with each other, a rotational force is generated in a direction that loosens the engagement between the male thread portion 14A and the female thread portion 15E.

[0110] As a result, the electric actuator 10 can reliably prevent the contact surface pressure between the shaft 11A and the thrust bearing 14 from becoming excessively large, and can reliably prevent large drive losses from occurring at the contact point between the shaft 11A and the thrust bearing 14.

[0111] In the electric actuator 10 according to this embodiment, when the shaft 11A rotates in the normal direction, a rotational force in the normal direction acts on the thrust bearing 14 and the cap 16. This rotational force exerts a force on the ridges 16B and 16L.

[0112] In this embodiment, the length L1 of the extension length of the protrusion 16B at one widthwise end is longer than the length L2 of the extension length of the protrusion 16B at the other widthwise end, and the direction from the one widthwise end to the other widthwise end coincides with the load direction DL.

[0113] That is, in the electric actuator 10, the rotational force is received at one end of the ribs 16B and 15L in the width direction. Therefore, compared to a configuration in which the rotational force is received at the other end of the ribs 16B and 15L in the width direction, the area of the portion receiving the rotational force is larger, and the performance of the electric actuator is stabilized.

[0114] (Other embodiments) The housing 15 according to the above-described embodiment is configured with multiple components (for example, the housing main body 15A and the bearing holder 15B). However, the present disclosure is not limited to this. That is, the present disclosure may also be configured with, for example, a single product in which the housing main body 15A and the bearing holder 15B are integrally molded.

[0115] The electric actuator 10 according to the above-described embodiment has a configuration including a worm 12 as a gear. However, the present disclosure is not limited to this. That is, the present disclosure may also be applicable to an electric actuator having, for example, a spur gear or a bevel gear as a gear.

[0116] In the above-described embodiment, the inclined surfaces 16C and 15M are configured to be inclined so as to generate a rotational force in a direction that loosens the threaded engagement between the male thread portion 14A and the female thread portion 15E when the cap 16 is attached. However, the present disclosure is not limited to this.

[0117] That is, the disclosure may be configured such that, for example, the inclined surfaces 16C and 15M are inclined so as to generate a rotational force in a direction that tightens the threaded engagement between the male thread portion 14A and the female thread portion 15E when the cap 16 is attached.

[0118] In this configuration, the make-up stop current value may be the same as or different from that in the above-described embodiment. In this configuration, since a rotational force in the tightening direction may be generated when the cap 16 is attached, it is desirable to set the make-up stop current value in this configuration to a smaller value than the make-up stop current value in the above-described embodiment.

[0119] In the above-described embodiment, the configuration satisfies all of requirements (a) to (c). However, the present disclosure is not limited to this. That is, the present disclosure may have a configuration that does not satisfy at least one of requirements (a) to (c), for example.

[0120] In the above-described embodiment, the vehicle seat according to the present disclosure is applied to a vehicle. However, the application of the invention disclosed in this specification is not limited thereto. That is, the present disclosure can also be applied to seats used in vehicles such as railway cars, ships, and aircraft, as well as stationary seats used in theaters, homes, etc.

[0121] Furthermore, the present disclosure is not limited to the above-described embodiments as long as it conforms to the spirit of the disclosure described in the above-described embodiments. Therefore, the present disclosure may be a configuration in which at least two of the above-described embodiments are combined, or a configuration in which any of the components illustrated or described with reference numerals in the above-described embodiments is eliminated. [Explanation of symbols]

[0122] 10... Electric actuator 11... Electric motor 11A... Shaft 12... Gear (worm) 12A... Output gear (worm wheel) 13... Radial bearing 14... Thrust bearing 14A... Male thread 14B... First engaged part 14C... Second engaged part 14D... Slit 15... Housing 15A... Storage section 15A... Housing body 15B... Bearing holder 15C... Holding portion 15D... Rotation stopper portion 15E... Female thread portion 15J... Insertion port 15K... Engaged portion 15M... Inclined surface 15L... Ridge 16... Cap 16A... Outer circumferential engagement part 16B... Projection 16C... Inclined surface 17... Inner circumference engaging part 17A... First engaging part 17B... Second engaging part

Claims

1. An electric actuator for use in a vehicle seat, the electric actuator including an electric motor, a shaft that is rotationally driven by the electric motor, and a gear fixed to the shaft, a radial bearing that contacts an outer peripheral surface of the shaft and rotatably supports the shaft; a thrust bearing that contacts an end of the shaft in the direction of the rotation central axis to restrict displacement of the shaft in the direction of the rotation central axis, the thrust bearing having a male screw portion that forms a spiral with the rotation central axis as its center line; a housing having a storage portion in which at least the thrust bearing is stored, the housing having a female thread portion that is threadedly engaged with the male thread portion; a cylindrical cap inserted into the storage portion through an insertion opening of the storage portion, the cylindrical cap restricting rotation of the thrust bearing around the central axis of rotation, an outer peripheral surface of the cap is provided with an outer peripheral engaging portion that engages with an engaged portion that is provided on an inner peripheral surface of the storage portion, and an inner peripheral engaging portion that engages with the thrust bearing is provided on an inner peripheral surface of the cap, Furthermore, an electric actuator is provided with an inclined surface inclined with respect to an imaginary line parallel to the rotation center axis on at least one of the tip side in the insertion direction of the outer peripheral engaging portion and the insertion opening side of the engaged portion, the inclined surface generating a rotational force that rotates the cap in a predetermined direction with the rotation center axis as the center line when the cap is inserted along the rotation center axis.

2. 2. The electric actuator according to claim 1, wherein the inclined surface is inclined with respect to the imaginary line so as to generate a rotational force in a direction that loosens the engagement between the male thread portion and the female thread portion when the leading end side of the outer peripheral engaging portion in the insertion direction comes into contact with the insertion opening side of the engaged portion.

3. the outer peripheral engaging portion and the engaged portion are configured in a serration or spline shape having a plurality of protrusions extending in a direction parallel to the rotation central axis, and the inclined surface is provided on an end side of the protrusions in the extension direction, When the direction of rotation of the shaft when the contact surface pressure between the shaft and the thrust bearing increases is defined as the normal rotation direction, the normal rotation direction projected onto an imaginary plane including the rotation central axis is defined as the load direction, and a direction perpendicular to the extension direction of the protrusion is defined as the width direction, 3. The electric actuator according to claim 2, wherein the length of one widthwise end of the extension direction of the protrusion provided on the cap is longer than the length of the other widthwise end of the extension direction of the protrusion, and the direction from the one widthwise end to the other widthwise end coincides with the direction of the load.

4. When a portion of the thrust bearing that is in contact with the shaft is defined as a contact end, and an end of the thrust bearing opposite to the contact end in the direction of the rotation center axis is defined as a non-contact end, a rotation restricting portion provided at the inner circumferential engaging portion for restricting rotation of the thrust bearing relative to the cap about the central rotation axis; a restrictive engagement portion provided on an inner circumferential surface of the cap and engaging with the rotation restricting portion, the restrictive engagement portion being provided in a range from the male thread portion to the non-contact end, 4. The electric actuator according to claim 1, wherein the non-contact end of the thrust bearing is located outside the housing.

5. a protrusion provided on the inner circumferential surface of the cap on the contact end side; a fitting portion provided on the non-contact end side of the thrust bearing, into which the protrusion can be fitted and engaged, 5. The electric actuator according to claim 4, wherein when the protrusion is fitted into the fitting portion and the contact end of the thrust bearing is in contact with the shaft, the outer peripheral engaging portion and the engaged portion are in a disengaged state.

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