Electric actuator

Abstract

To improve durability of a detent mechanism.SOLUTION: In an electric actuator (1), a fitting part (50) provided in a linear motion part (12) or piston (30) is fitted to a part to be fitted (40) provided in an inner periphery of a cylinder (20), where a sliding portion of the fitting part (50) relative to the part to be fitted (40) differs in accordance with a relative position in an axial direction of the linear motion part (12) or piston (30) relative to the cylinder (20).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to electric actuators. [Background technology]

[0002] In Patent Document 1, a notch is provided in a ring provided on the outer periphery of the piston body, and a needle held in a cylinder is fitted into the notch provided in the ring, thereby achieving a rotation prevention function. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2020-536784 Summary of the Invention [Problem to be solved by the invention]

[0004] However, sliding between the notch of the ring and the needle may cause concentrated wear at specific locations on the notch or the needle. An object of the present disclosure is to improve the durability of the anti-rotation mechanism. [Means for solving the problem]

[0005] In order to solve the above-mentioned problems, an electric actuator according to one aspect of the present disclosure is an electric actuator including a piston that is driven by the linear motion part of a linear motion conversion mechanism and slides in a cylinder, the piston being configured to slide in a forward or backward direction by a rotational motion of an electric motor, the linear motion part ... and a mated portion which is a convex portion formed by a groove or a hole, and the mated portion is mated with the mated portion, and a portion of the mated portion slides between the mated portion and the mated portion, thereby restricting the relative rotation of the linear moving portion with respect to the cylinder about the axis of the linear moving portion, or restricting the relative rotation of the piston with respect to the cylinder about the axis of the piston, and the mated portion is formed so that the sliding portion of the mated portion with respect to the mated portion varies depending on the relative axial position of the linear moving portion or the piston with respect to the cylinder. [Effects of the Invention]

[0006] According to one aspect of the present disclosure, the durability of the anti-rotation mechanism can be improved. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a cross-sectional view of an electric actuator according to an embodiment of the present disclosure. [Figure 2] FIG. 1 is a cross-sectional view of an electric actuator according to an embodiment of the present disclosure. [Figure 3] 10A and 10B are diagrams used to explain modified examples of the guide portion. DETAILED DESCRIPTION OF THE INVENTION

[0008] 1 and 2 are cross-sectional views of an electric actuator according to an embodiment of the present disclosure. Fig. 1(a) is a schematic cross-sectional view showing an electric actuator according to an embodiment of the present disclosure. Fig. 1(b) is a cross-sectional view taken along line AA of Fig. 1(a).

[0009] As shown in Fig. 1(a), an electric actuator 1 according to an embodiment of the present disclosure is an electric actuator used, for example, in a hydraulic caliper, and includes a linear motion conversion mechanism 10, a cylinder 20, and a piston 30. Hereinafter, the forward direction and the backward direction will be defined as shown by the arrows in Fig. 1(a). In Fig. 1(a), the forward direction and the backward direction are parallel to the axis R of the cylinder 20.

[0010] The linear motion conversion mechanism 10 has a rotating unit 11 and a linear motion unit 12. Rotational motion is transmitted to the rotating unit 11 from an electric motor (not shown), and the rotating unit 11 rotates about its axis R. In FIG. 1A, the axes of the rotating unit 11 and the linear motion unit 12 extend at the same position as the axis R of the cylinder 20. Relative rotation of the linear motion unit 12 with respect to the cylinder 20 about the axis R of the cylinder 20 is restricted by a mechanism described in detail below. The rotating unit 11 and the linear motion unit 12 have a screw mechanism that screws together, converting the rotational motion of the rotating unit 11 into linear motion of the linear motion unit 12. When the rotating unit 11 rotates in a predetermined forward direction, the linear motion unit 12 moves linearly forward, and when the rotating unit 11 rotates in the opposite direction, the linear motion unit 12 moves linearly backward. The piston 30 is driven by the linear motion unit 12 and slides inside the cylinder 20. In FIG. 1( a ), the linear motion portion 12 and the piston 30 are in the most retracted position, and their axes extend in the same position as the axis R of the cylinder 20 .

[0011] The linear motion portion 12 has a recess 50. The recess 50 is an example of a fitting portion. As shown in FIG. 1(a), the linear motion portion 12 has a flange 13 protruding from the side surface, and the recess 50 is provided at the tip of the flange 13. The recess 50 is a groove recessed from the tip of the flange 13 in the radial direction of the linear motion portion 12, and penetrates the flange 13 in the axial direction of the linear motion portion 12.

[0012] The cylinder 20 has an expanded diameter portion 51. The expanded diameter portion 51 is provided on the inner circumferential surface of the cylinder 20. A holding portion 41 that holds a rod-shaped guide portion 40 protrudes from the expanded diameter portion 51 of the cylinder 20. The guide portion 40 is an example of a fitted portion, and is configured so that at least a portion of it protrudes from the inner periphery of the cylinder 20. For example, a portion of the guide portion 40 is engaged with the holding portion 41. The guide portion 40 extends at an angle with respect to the axis R of the cylinder 20, and the amount of protrusion of the guide portion 40 from the inner circumferential surface of the cylinder 20 varies with respect to the axis R of the cylinder 20. The amount by which the guide portion 40 protrudes from the inner circumferential surface of the cylinder 20 is smaller toward the forward direction and larger toward the backward direction.

[0013] As shown in FIG. 1(b), the guide portion 40 is fitted into the recess 50 of the linear moving portion 12 and abuts against the inner wall of the recess 50. This restricts the relative rotation of the linear moving portion 12 about its axis with respect to the cylinder 20 and the relative rotation of the piston 30 about its axis. When the guide portion 40 is fitted into the recess 50 of the linear moving portion 12, the width of the guide portion 40 is approximately the same as the width of the recess 50. The sliding portion of the recess 50 relative to the guide portion 40 differs depending on the axial position of the linear moving portion 12 relative to the cylinder 20. The sliding portion of the recess 50 relative to the guide portion 40 is the position where the guide portion 40 abuts against the inner surface of the recess 50.

[0014] Fig. 2(a) is a schematic cross-sectional view showing an electric actuator according to an embodiment of the present disclosure. Fig. 2(b) is a cross-sectional view taken along the line B-B of Fig. 2(a). Fig. 2(a) shows an example of a state in which the linear moving part 12 and the piston 30 have moved forward from the state shown in Fig. 1(a), with the linear moving part 12 and the piston 30 at their most forward positions.

[0015] As the linear moving part 12 moves forward, the inner surface of the recessed part 50 slides while contacting the guide part 40. As shown in (b) of Fig. 2, the sliding part of the inner surface of the recessed part 50 that contacts the guide part 40 moves away from the axis R of the cylinder 20 and approaches the inner periphery of the cylinder 20 more than the position shown in (b) of Fig. 1 due to the forward movement of the linear moving part 12.

[0016] When the linear motion portion 12 moves a predetermined distance in the backward direction, the first point 42 of the guide portion 40 comes into contact with the bottom surface of the recessed portion 50. The sliding movement between the bottom surface of the recessed portion 50 and the first point 42 of the guide portion 40 restricts the linear motion portion 12 from moving backward beyond the predetermined movement range.

[0017] The guide portion 40 has a tip end 43 that extends further toward the rearward direction than the first point 42. The tip end 43 may abut against the rear surface 21 of the cylinder 20, for example. The tip end 43 may have a different spring constant than portions of the guide portion 40 other than the tip end 43. The guide portion 40 may also be partially bent. For example, the extension direction of the tip end 43 may be different from portions of the guide portion 40 other than the tip end 43. For example, the guide portion 40 may be bent toward the tip end 43 from the first point 42 in a direction that brings it closer to the axis of the cylinder 20. When the linear moving portion 12 is positioned near the most retracted position, the tip end 43 of the guide portion 40 biases the linear moving portion 12 in the forward direction. This reduces the retraction speed of the linear moving portion 12 when the linear moving portion 12 is positioned near the most retracted position, and reduces the impact applied to the linear moving portion 12 when the linear moving portion 12 stops at the most retracted position. The sliding portion of the recess 50 relative to the guide portion 40 may be changed over the entire movable range in the axial direction of the linear moving portion 12, or may be changed over a partial movable range. When changing the sliding portion of the recess 50 relative to the guide portion 40 over a partial movable range in the axial direction of the linear moving portion 12, for example, the guide portion 40 may be bent midway so as to abut against the inner periphery of the cylinder 20.

[0018] [Modification] In the above embodiment, the recess 50 is a groove recessed from the tip of the flange 13 in the radial direction of the cylinder 20 and penetrates the flange 13 in the axial direction of the cylinder 20, but the shape of the recess 50 is not limited to this. For example, the recess 50 may be a hole penetrating the flange 13 in the axial direction of the cylinder 20. In the above embodiment and modified example, the recess 50 is provided in the flange 13 of the linearly moving portion 12, but the recess 50 may be provided in the piston 30. In this case, the recess 50 may be provided in the piston 30 so that the sliding portion of the recess 50 relative to the guide portion 40 varies depending on the relative axial position of the piston 30 with respect to the cylinder 20.

[0019] In the above embodiment, the holding portion 41 protrudes into the expanded diameter portion 51 provided on the inner circumferential surface of the cylinder 20, but this is not limiting. For example, the holding portion 41 may be held by the expanded diameter portion 51 provided on the inner circumferential surface of the cylinder 20.

[0020] The guide portion 40 is held by a holding portion 41 provided in the expanded diameter portion 51 of the cylinder 20. However, the guide portion 40 may be formed integrally with the cylinder 20, and for example, the inner periphery of the cylinder 20 may be formed so as to protrude from the expanded diameter portion 51.

[0021] In the above embodiment, the amount by which the guide portion 40 protrudes from the inner circumferential surface of the cylinder 20 is smaller toward the forward direction and larger toward the backward direction. However, the guide portion 40 can have any shape as long as the sliding portion of the recessed portion 50 relative to the guide portion 40 approaches the inner periphery of the cylinder 20 as the linearly moving portion 12 moves forward. For example, the guide portion 40 may be a plate material with a protruding portion that abuts against the recessed portion 50, as shown in FIG. 3 . Changing the guide portion 40 from a pin shape to a plate material, as shown in FIG. 3(a), makes it easier to fix the guide portion 40 to the inner periphery of the cylinder 20. FIG. 3(b) is a schematic diagram showing an example of a cross section taken along CC in FIG. 3(a). FIG. 3(c) is a schematic diagram showing an example of a cross section taken along DD in FIG. 3(a). Here, when the guide portion 40 is made of a plate material, it is preferable to provide a protruding portion from the plate material on the surface where the torque applied to the guide portion 40 is greatest. This reduces the area of ​​the sliding surface between the guide portion 40 and the recess 50, thereby reducing the resistance component of the linear movement of the linear moving portion 12 or the piston 30 even if a large torque is applied to the guide portion 40.

[0022] The cross-sectional shape of the guide portion 40 is not limited to those shown in Fig. 1(b) and Fig. 2(b). The cross-sectional shape of the guide portion 40 may be, for example, rectangular. Furthermore, the guide portion 40 may be in close contact with the recessed portion 50 in the vicinity of the first point 42 to restrict the relative rotation of the guide portion 40 with respect to the recessed portion 50. The cross-sectional shape of the recess 50 is not limited to those shown in Figure 1(b) and Figure 2(b). The bottom surface of the recess 50 may be, for example, a curved surface.

[0023] In the above embodiment, the axis of the linear motion portion 12 and the axis of the piston 30 extend in the same position as the axis R of the cylinder 20, but this is not limiting.

[0024] In the above embodiment, the electric actuator 1 is an electric actuator used for a hydraulic caliper, but is not limited to this. The same effects can be obtained even when the electric actuator 1 is applied to something other than a hydraulic caliper, for example, an electric caliper. In the above embodiment, the recess 50 is used as the fitting portion and the guide portion 40 protruding from the inner periphery of the cylinder 20 is used as the fitted portion, but this is not limited to this. The fitting portion may be convex and the fitted portion may be concave, as long as the fitting portion is formed so that the sliding portion of the fitted portion relative to the fitting portion varies depending on the relative axial position of the linear moving portion or piston with respect to the cylinder.

[0025] 〔summary〕 An electric actuator according to one aspect of the present disclosure provides an electric actuator in which a rotating part of a linear motion conversion mechanism rotates in response to the rotational motion of an electric motor, and the rotational motion of the rotating part is converted into linear motion in a forward or backward direction of a linear motion part of the linear motion conversion mechanism, and the electric actuator includes a piston that is driven by the linear motion part and slides inside a cylinder, the electric actuator including: a fitting part that is a recessed or protruding part formed by a groove or hole provided in the linear motion part or the piston; and a protruding part or a fitting part that is provided on the inner circumference of the cylinder by a part of the inner circumference of the cylinder or a member held on the inner circumference of the cylinder. and a mating portion which is a recess formed by a groove or a hole, and the mating portion and the mating portion are mated together, and a portion of the mating portion and the mating portion slide together, thereby restricting the relative rotation of the linear moving portion with respect to the cylinder about the axis of the linear moving portion, or restricting the relative rotation of the piston with respect to the cylinder about the axis of the piston, and the mating portion is formed so that the sliding portion of the mating portion with respect to the mating portion differs depending on the relative axial position of the linear moving portion or the piston with respect to the cylinder. The sliding portion of the mating portion relative to the mated portion changes depending on the axial relative position of the linear motion portion or piston with respect to the cylinder, so that only specific portions of the mating portion do not slide against the mated portion. This distributes the sliding points of the mating portion and improves the durability of the anti-rotation mechanism.

[0026] In one aspect of the electric actuator of the present disclosure, the fitting portion is formed so that when the axial relative position of the linear motion portion or the piston with respect to the cylinder changes in the forward direction, the sliding portion with respect to the fitted portion approaches the inner circumference of the cylinder, and the fitted portion is configured so that a portion of it protrudes from the inner circumference of the cylinder by a member held on the inner circumference of the cylinder, and the fitted portion is held on the inner circumference of the cylinder at a portion that includes the end of the fitted portion on the forward direction side. Generally, when a load connected to an electric actuator is operated, the load on the electric actuator decreases as the linear moving part and piston move backward, and increases as the linear moving part and piston move forward. In this case, the torque applied to the protrusion that functions as a rotation stop for the recess increases as the linear moving part and piston move forward. On the other hand, the torque applied to the protrusion that functions as a rotation stop for the recess decreases as the linear moving part and piston move backward. As described above, by configuring the cylinder and the protrusion as separate parts, holding the protrusion on the inner periphery of the cylinder at a portion including the end of the protrusion on the forward direction side, and forming the recess so that the sliding portion for the protrusion approaches the inner periphery of the cylinder when the axial position of the linear moving part or piston relative to the cylinder changes in the forward direction, deformation of the protrusion can be suppressed even with a simple structure for holding the protrusion on the cylinder. For example, even when the guide part 40 is supported at one point by the holding part 41 provided on the inner periphery of the cylinder 20, deformation of the guide part 40 can be suppressed.

[0027] In one aspect of the electric actuator of the present disclosure, when the relative position of the linear motion part or the piston with respect to the cylinder retreats to a predetermined position, a part of the mated part abuts against the bottom of the mating part, thereby urging the mating part in the forward direction. According to the above configuration, when the relative position of the linear moving part or the piston with respect to the cylinder retreats to a predetermined position, a part of the mated part abuts against the bottom of the mating part, and either the linear moving part or the piston provided with the mating part is urged in the forward direction, thereby slowing down the retreat speed of the linear moving part and the piston and mitigating the impact when the linear moving part and the piston stop. [Additional Notes] The present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present disclosure. [Explanation of symbols]

[0028] 1 Electric Actuator 10. Linear motion conversion mechanism 11 Rotating part 12 Linear motion section 20 cylinders 30 pistons 40 Guide section 41 Holding part 50 recess R axis

Claims

1. An electric actuator including: a rotating part of a linear motion conversion mechanism that rotates in response to rotational motion of an electric motor; the rotational motion of the rotating part is converted into linear motion in an advancing direction or a retreating direction of a linear motion part of the linear motion conversion mechanism; and a piston that is driven by the linear motion part and slides in a cylinder; a fitting portion which is a recess or a protrusion formed by a groove or a hole provided in the linear motion portion or the piston; a fitted portion which is a recess formed by a protrusion, a groove, or a hole provided on the inner circumference of the cylinder by a part of the inner circumference of the cylinder or a member held on the inner circumference of the cylinder, the fitting portion and the fitted portion are fitted together, and a portion of the fitting portion and the fitted portion slide together, thereby restricting a relative rotation of the linear motion portion with respect to the cylinder about the axis of the linear motion portion, or restricting a relative rotation of the piston with respect to the cylinder about the axis of the piston, The fitting portion is formed so that a sliding portion of the fitting portion relative to the fitted portion varies depending on the relative axial position of the linear motion portion or the piston with respect to the cylinder.

2. the fitting portion is formed so that, when the relative position of the linear motion portion or the piston with respect to the cylinder in the axial direction changes in the forward movement direction, the sliding portion with respect to the fitted portion approaches an inner periphery of the cylinder, the fitted portion is configured so that a portion thereof protrudes from the inner periphery of the cylinder by a member held on the inner periphery of the cylinder, The electric actuator according to claim 1 , wherein the fitted portion is held on an inner periphery of the cylinder at a portion including an end portion of the fitted portion on the forward direction side.

3. 2. The electric actuator according to claim 1, wherein when the relative position of the linear motion portion or the piston with respect to the cylinder retreats to a predetermined position, a portion of the fitted portion abuts against a bottom of the fitting portion, thereby urging the fitting portion in the forward direction.

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