JP2022053022A - Electric actuator - Google Patents

Abstract

To prevent a protrusion from coming out of a linear motion member.SOLUTION: An electric actuator 1 includes an electric motor 2, a screw shaft 7 that is rotationally driven by the electric motor 2, a nut 8 screwed with the screw shaft 7, and a swing member 11 that swings due to the linear motion of the nut 8, and the nut 8 includes a protrusion 12 that abuts on the swing member 11 and swings the swing member 11, and as a retaining structure for preventing the protrusion 12 from coming out of the nut 8, the inside of a hole 8b of the nut 8 is equipped with a circlip 32.SELECTED DRAWING: Figure 6

Description

The present invention relates to an electric actuator.

In recent years, motorization has progressed in order to save labor and reduce fuel consumption of vehicles. For example, a system for operating an automatic transmission, a brake, a steering wheel, etc. of an automobile by the power of an electric motor has been developed and put on the market. ..

As an electric actuator used for such an application, for example, in Patent Document 1, as shown in FIG. 9, a first method of converting a rotational motion of an electric motor 300 into a linear motion (movement in the directions of arrows A1 and A2 in the figure). The second motion conversion that converts the linear motion of the motion conversion mechanism 100 and the first motion conversion mechanism 100 into rotational motion (movement in the directions of arrows B1 and B2 in the figure) of the axis orthogonal to the rotation axis of the electric motor 300. An electric actuator with a mechanism 200 is disclosed. Specifically, the first motion conversion mechanism 100 is composed of a sliding screw mechanism having a screw shaft 101 as a rotating member and a nut 102 as a linear motion member screwed with the screw shaft 101. On the other hand, the second motion conversion mechanism 200 is composed of a swing member 201 having a cylindrical portion 201a and an arm portion 201b. The arm portion 201b is provided with a long hole 201c. Further, by inserting the pin-shaped connecting member 202 into the hole of the nut 102, a protrusion is formed in which a part of the connecting member 202 protrudes from the nut 102. By inserting a protrusion provided on the nut 102 into the elongated hole 201c, the swing member 201 and the nut 102 are interlocked with each other.

When the screw shaft 101 rotates forward or reverse by driving the electric motor 300, the nut 102 moves in the direction of arrow A1 or the direction of arrow A2, so that the rotary motion is converted into a linear motion. Then, as the nut 102 moves, the arm portion 201b is pushed and moved in the moving direction by the protrusion, and the swing member 201 swings in the arrow B1 direction or the arrow B2 direction around the cylindrical portion 201a. As a result, the linear motion is converted into a rotary motion of an axis orthogonal to the rotary axis of the electric motor 300.

Japanese Unexamined Patent Publication No. 2019-97352

In the configuration of Patent Document 1, as described above, the linear motion member moves linearly due to the rotational operation of the screw shaft, and when the protrusion pushes the swing member, the protrusion receives the reaction force from the swing member. become. That is, the protrusion receives a force in the direction opposite to the direction in which the linear motion member moves linearly. Then, when the driving of the electric motor is repeated, the protrusions are repeatedly pressurized in both directions (left direction and right direction in FIG. 9) in the direction opposite to the moving direction of the linear moving member. Will be done. As a result, the inventors have stated that the members constituting the protrusion gradually come out of the linear motion member as the driving time of the electric actuator increases due to the force in the direction in which the protrusion comes out of the linear motion member. Found. Finally, it was discovered that the member constituting the protrusion falls off from the linear motion member.

In view of the above circumstances, it is an object of the present invention to prevent the protrusion from coming out of the linearly moving member.

In order to solve the above problems, the present invention swings by a linear motion of an electric motor, a rotating member rotationally driven by the electric motor, a linear motion member screwed with the rotary member, and the linear motion member. An electric actuator including a swing member, wherein the linear motion member has a protrusion that abuts on the swing member and swings the swing member, and the protrusion is from the linear motion member. It is characterized by having a retaining structure that prevents it from slipping out.

With the electric actuator, it is possible to prevent the protrusion from coming off from the linearly moving member.

A rod-shaped member is inserted into a hole provided in the linear motion member, and the protrusion is a part of the rod-shaped member protruding from the surface of the linear motion member, and holds the rod-shaped member in the hole portion as a retaining structure. Retaining rings can be attached.

As a retaining structure, the linear motion member and the protrusion can be integrally provided.

According to the present invention, it is possible to prevent the protrusion from coming off from the linearly moving member.

It is a perspective view of the electric actuator which concerns on one Embodiment of this invention. It is a vertical sectional view of an electric actuator. It is a perspective view of the nut into which the screw shaft is inserted. It is a front view of the nut into which the screw shaft is inserted. It is a perspective view of a pin and a circlip. FIG. 4 is a cross-sectional view taken along the line AA of FIG. It is a perspective view of the nut of a different embodiment. It is sectional drawing of the nut of FIG. 7 in which a screw shaft is inserted. It is a vertical sectional view which shows the conventional electric actuator.

Hereinafter, embodiments according to the present invention will be described with reference to the drawings. In each figure, the same or corresponding parts are designated by the same reference numerals, and the duplicated description thereof will be appropriately simplified or omitted.

FIG. 1 is a perspective view of an electric actuator according to an embodiment of the present invention, and FIG. 2 is a vertical sectional view of the electric actuator according to the present embodiment.

As shown in FIG. 1, the electric actuator 1 according to the present embodiment has a linear motion of an electric motor 2, a speed reducer 3 that decelerates and outputs the rotation of the electric motor 2, and a rotary motion output from the speed reducer 3. The first motion conversion mechanism 4 that converts to It mainly includes a mechanism 5 and a housing 6 for accommodating them.

In this embodiment, as the electric motor 2, a small motor such as a brushed motor or a brushless motor is used. The electric motor 2 is connected to an external power supply (not shown) via a relay circuit (not shown) which is a switching element provided in the housing 6. A motor holder 16 for holding the electric motor 2 is provided on one end side (reducer 3 side) in the axial direction of the electric motor 2. The motor holder 16 is assembled to the housing 6. As a result, the electric motor 2 is supported by the housing 6 via the motor holder 16. Further, the motor holder 16 and the electric motor 2 are fixed by a plurality of bolts 17 (see FIG. 2) as fixing members.

The housing 6 is configured by assembling two housing split bodies 60. FIG. 1 shows a state in which one of the two housing divisions 60 is removed from the other. By assembling the housing divisions 60 to each other via a sealing member (not shown) between the mating surfaces, the internal space of the housing 6 is sealed and foreign substances such as dust and water are prevented from entering the housing 6. Will be done. In particular, as in the present embodiment, by making the mating surface of the housing split 60 a flat surface parallel to the rotating shaft 2a of the electric motor 2 (without a step), the mating surfaces of the housing split 60 are aligned with each other at the time of assembly. Even if there is some deviation between the mating surfaces, it is difficult for gaps to occur between the mating surfaces, and it is easy to ensure airtightness. As the sealing member, a solid sealing material such as an O-ring, a rubber sheet, a resin sheet, a joint sheet, or a metal gasket, or a liquid sealing member such as a liquid gasket can be adopted.

As shown in FIG. 2, the first motion conversion mechanism 4 has a screw shaft 7 as a rotating member and a nut 8 as a linear motion member. The nut 8 linearly moves in the direction of the axis of rotation as the screw shaft 7 rotates. Thread grooves are formed on the outer peripheral surface of the screw shaft 7 and the inner peripheral surface of the nut 8, respectively, and these screw shafts are directly screwed to form a sliding screw mechanism. As the first motion conversion mechanism 4, a ball screw mechanism in which a plurality of balls are interposed between the screw shaft (rotating member) and the nut (linear motion member) may be used. The screw shaft 7 is rotatably supported with respect to the housing 6 at both ends in the rotation axis direction via a radial bearing 9 and a thrust bearing 10, respectively. Further, the two sets of radial bearings 9 and thrust bearings 10 arranged on one end side and the other end side of the screw shaft 7 are held by a bearing holder 18 assembled to the housing 6, respectively.

The second motion conversion mechanism 5 includes a cylindrical output shaft 14 and a swing member 11 attached to the output shaft 14. The output shaft 14 is rotatably supported by the housing 6 via a radial bearing 15 (see FIG. 1). The swing member 11 is attached to both ends of the output shaft 14 in the axial direction, and is configured to swing (rotatably) integrally with the output shaft 14 around the output shaft 14. Further, the output shaft 14 is provided with a connecting hole 14a in which a plurality of irregularities (splines) are formed on the inner peripheral surface. The connecting hole 14a is a hole for inserting an operation shaft provided in an operation target (not shown). When the operating shaft is inserted into the connecting hole 14a and spline-fitted, the operating shaft is rotatably connected to the output shaft 14. Further, the rocking member 11 is provided with a slit-shaped elongated hole 11c as a recess that opens at the lower end side shown in FIG. A columnar protrusion 12 protruding from the nut 8 is inserted into the elongated hole 11c. As a result, the nut 8 and the swing member 11 are configured to be interlocked with each other via the protrusion 12. Further, in the present embodiment, the protrusions 12 are provided on the surfaces of the nut 8 on opposite sides to each other, and the swing members 11 having the elongated holes 11c are also provided on both sides of the nut 8 so as to correspond to the protrusions 12. ing.

The speed reducer 3 is arranged between the electric motor 2 and the first motion conversion mechanism 4. In this embodiment, a two-stage planetary speed reducer 20 is used as the speed reducer 3. Specifically, as shown in FIG. 2, the planetary speed reducer 20 includes a first sun gear 21 as a first-stage input rotating body, a plurality of first planetary gears 22 as a first-stage planetary rotating body, and one stage. A first carrier 23 that also serves as an output rotating body for the eyes and an input rotating body for the second stage, a plurality of second planetary gears 24 as the planetary rotating bodies for the second stage, and a second carrier as the output rotating body for the second stage. It includes a carrier 25 and a ring gear 26 that also serves as a first-stage and second-stage track ring.

The first sun gear 21 is attached to the rotating shaft 2a of the electric motor 2 so as to rotate integrally with the rotating shaft 2a. The ring gear 26 is arranged on the outer periphery of the first sun gear 21 and is assembled so as not to rotate with respect to the housing 6. A plurality of first planetary gears 22 are provided in the circumferential direction of the first sun gear 21. Each first planetary gear 22 is interposed between the first sun gear 21 and the ring gear 26, and is arranged so as to mesh with each other. Further, each first planetary gear 22 is rotatably attached to a flange portion 23b protruding in the outer diameter direction from the cylindrical portion 23a of the first carrier 23. A gear portion 23c in which a plurality of teeth are arranged in the circumferential direction is provided on the outer peripheral surface of the cylindrical portion 23a of the first carrier 23. Further, the rotating shaft 2a of the electric motor 2 is inserted into the inner circumference of the cylindrical portion 23a of the first carrier 23 in a relatively rotatable state. A plurality of second planetary gears 24 that mesh with the gear portions 23c of the first carrier 23 and the ring gears 26 are arranged. Each second planetary gear 24 is rotatably attached to a flange portion 25b protruding in the outer diameter direction from the cylindrical portion 25a of the second carrier 25. Further, the second carrier 25 is inserted with one end side of the screw shaft 7. A plurality of irregularities (splines) 25d and 7a extending in the axial direction are formed on the inner peripheral surface of the cylindrical portion 25a of the second carrier 25 and the outer peripheral surface on the one end side of the screw shaft 7, respectively, and these irregularities are formed. By spline fitting the 25d and 7a together, the screw shaft 7 is movable in the axial direction with respect to the second carrier 25 and is integrally rotatably connected in the circumferential direction. Further, on the outer peripheral surface of the cylindrical portion 25a of the second carrier 25, one radial bearing 9 that supports one end side of the screw shaft 7 is arranged.

Here, in the present embodiment, the first carrier 23 also serves as the first-stage output rotating body and the second-stage input rotating body, but functions as the first-stage output rotating body (first planetary gear 22). The flange portion 23b) for holding the above and the portion (cylindrical portion 23a having the gear portion 23c) that functions as the input rotating body of the second stage may be configured as separate bodies. Similarly, the ring gear 26 also has a portion that functions as a first-stage orbital ring (a portion that meshes with the first planetary gear 22) and a portion that functions as a second-stage orbital ring (a portion that meshes with the second planetary gear 24). It may be configured separately.

Subsequently, the operation of the electric actuator according to the present embodiment will be described.

Electric power is supplied from the power source to the electric motor 2 by switching the relay circuit, and when the electric motor 2 rotates in the forward direction or in the reverse direction, the rotational motion is transmitted to the planetary reducer 20 (reducer 3). In the planetary speed reducer 20, the first sun gear 21 rotates integrally with the electric motor 2 (rotating shaft 2a), so that a plurality of first planetary gears 22 meshing with the electric motor 2 start to rotate. Each first planetary gear 22 revolves along the ring gear 26 while rotating, and the revolving motion is output as the rotational motion of the first carrier 23 holding the first planetary gear 22. As a result, the rotational movement of the electric motor 2 is decelerated by one step.

Further, as the first carrier 23 rotates, a plurality of second planetary gears 24 that mesh with the gear portion 23c start to rotate. Each second planetary gear 24 revolves along the ring gear 26 while rotating, and the revolving motion is output as the rotational motion of the second carrier 25 holding the second planetary gear 24. As a result, the rotational motion is further decelerated.

As described above, the rotational motion of the rotary shaft 2a is decelerated and transmitted to the screw shaft 7 via the planetary reducer 20. Therefore, the rotational torque of the screw shaft 7 can be increased, and even a small electric motor 2 can obtain a large rotational torque.

The rotational motion decelerated by the speed reducer 3 is transmitted to the first motion conversion mechanism 4. That is, when the second carrier 25 of the planetary reducer 20 rotates, the screw shaft 7 of the first motion conversion mechanism 4 rotates integrally with the second carrier 25. When the screw shaft 7 rotates, the nut 8 moves linearly with the rotation. The nut 8 advances in the direction of arrow A1 in FIG. 2 when the electric motor 2 rotates in the forward direction, and retracts in the direction of arrow A2 in FIG. 2 when the electric motor 2 rotates in the reverse direction.

Then, as the nut 8 moves forward or backward, the protrusion 12 provided on the nut 8 comes into contact with the swing member 11 (the wall surface portion forming the elongated hole 11c) and pushes the swing member 11 to move. As a result, the swing member 11 swings in the direction of arrow B1 or arrow B2 in FIG. 2, and the output shaft 14 rotates integrally with the swing member 11, so that the linear motion of the nut 8 is caused by the electric motor 2. It is output as a rotary motion of an axis (output shaft 14) in a direction different from that of the rotary shaft 2a. In the present embodiment, the output shaft 14 is arranged in a direction orthogonal to the rotation shaft 2a of the electric motor 2 (direction orthogonal to the paper surface of FIG. 2). Therefore, the rotary motion of the electric motor 2 is output as a rotary motion of an axis orthogonal to the rotary axis 2a of the electric motor 2.

Next, the nut 8 and the protrusion 12 provided on the nut 8 will be described in more detail.

As shown in FIGS. 3 and 4, the nut 8 has a screw shaft 7 inserted into a through hole 8a provided inside the nut 8. The screw shaft 7 is screwed with a screw groove formed on the inner peripheral surface in the through hole 8a. The nut 8 has holes 8b that open in the direction orthogonal to the through holes 8a on both sides of the through holes 8a, and pins 31 as rod-shaped members are inserted into the holes 8b, respectively. A portion of one end of the pin 31 that protrudes from the surface of the nut 8 constitutes each protrusion 12.

By the way, as described above, when the protrusion 12 pushes and moves the swing member 11 by the drive of the electric actuator 1 (see FIG. 2), the protrusion 12 receives the reaction force. That is, the pin 31 that moves integrally with the nut 8 receives a force in the direction opposite to the moving direction of the nut 8. Then, as the electric actuator 1 repeatedly drives, the pin 31 alternately repeats the forces in the right direction and the left direction (arrows A1 direction and A2 direction) in FIG. 2 in the direction opposite to the moving direction of the nut 8. Will receive. As a result, a force acts on the pin 31 in the direction of coming out of the hole 8b, and as the driving time of the electric actuator 1 becomes longer, the pin 31 gradually comes out of the hole 8b. As a result, the amount of protrusion of the protrusion 12 from the nut 8 may increase, or the pin 31 may completely fall out of the hole 8b. When the amount of protrusion of the protrusion 12 becomes large, one end of the protrusion 12 (pin 31) slides with the inner surface of the housing 6 and causes wear of the housing 6. Further, when the pin 31 comes off, the nut 8 cannot swing the swing member 11. In order to deal with such a problem, the nut 8 of the present embodiment has a pin 31 retaining structure. Hereinafter, this retaining structure will be described.

As shown in FIG. 5, the pin 31 has a cylindrical shape and has a groove portion 31a formed in the circumferential direction (over the entire circumference) on the other end side inserted into the nut 8. The groove portion 31a is a portion to which the circlip 32 as a retaining ring is mounted. The circlip 32 is a C-shaped member lacking a part in the circumferential direction. By forming the circlip 32 into a C shape, the diameter of the circlip 32 can be easily expanded when the pin 31 described later is press-fitted. Further, the groove depth of the groove portion 31a is set to a depth equal to or larger than the wire diameter of the circlip 32.

As shown in FIG. 6, the hole 8b of the nut 8 is provided with a diameter-expanded portion 8b1 having a partially enlarged hole diameter. The enlarged diameter portion 8b1 is provided in the hole portion 8b in a circumferential shape. The enlarged diameter portion 8b1 is formed, for example, by cutting after forming the nut 8.

When attaching the pin 31 to the nut 8, first, the pin 31 is press-fitted into the hole 8b with the circlip 32 pushed into the groove 31a of the pin 31. Then, when the circlip 32 reaches the enlarged diameter portion 8b1 in the hole portion 8b, the circlip 32 expands in diameter by its own elastic force and enters the enlarged diameter portion 8b1. At this position, the pin 31 is held in the hole 8b of the nut 8. The enlarged diameter portion 8b1 is provided in both the hole portions 8b, and the circlip 32 is attached to both the enlarged diameter portions 8b1.

The circlip 32 enters the enlarged diameter portion 8b1 in the middle of the hole portion 8b and is held between the enlarged diameter portion 8b1 and the pin 31, so that the circlip 32 is held in the hole portion of the pin 31 (projection portion 12). It functions as a retaining structure for 8b. As a result, even if the protrusion 12 is repeatedly pressurized as described above, the pin 31 (protrusion 12) does not come out of the hole 8b. Therefore, the assembling property of the pin 31 with respect to the nut 8 and the reliability as a component can be improved.

Further, as a structure for preventing the protrusion 12 from coming off, the protrusion 12 may be integrally molded with the nut 8 as shown in FIGS. 7 and 8. Since the protrusion 12 is provided integrally with the nut 8, the protrusion 12 does not come out of the nut 8 even if the protrusion 12 is repeatedly pressurized as described above.

Further, by integrally molding the protrusion 12 with the nut 8, the step of post-processing the enlarged diameter portion 8b1 into the nut 8 and the circlip 32 being pushed into the pin 31 as in the above-described embodiment of FIG. The step of press-fitting the pin 31 into the hole 8b can be omitted. Further, it is not necessary to separately provide a member for preventing disconnection such as the circlip 32.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made without departing from the gist of the present invention.

The structure of the retaining ring is not limited to the above-mentioned C-shaped circlip 32. For example, an annular retaining ring can be used if the diameter is sufficiently expanded when the pin 31 is press-fitted. Further, the cross section of the retaining ring is not necessarily limited to a circular shape.

1 Electric actuator 2 Electric motor 2a Rotating shaft 3 Reducer 6 Housing 7 Screw shaft 8 Nut (linear motion member)
8b hole 8b1 enlarged diameter 9 radial bearing (bearing)
11 Swing member 11c Long hole (recess)
12 Protrusion 14 Output shaft 31 pin (rod-shaped member)
32 Circlip (retaining ring)

Claims (3)

An electric actuator including an electric motor, a rotating member rotationally driven by the electric motor, a linear motion member screwed with the rotary member, and a swing member that swings due to linear motion of the linear motion member. hand,
The linear motion member has a protrusion that abuts on the rocking member and swings the rocking member.
An electric actuator characterized by having a retaining structure for preventing the protrusion from coming out of the linear motion member. A rod-shaped member is inserted into the hole provided in the linear motion member, and the rod-shaped member is inserted into the hole.
The protrusion is a part of the rod-shaped member protruding from the surface of the linear motion member.
The electric actuator according to claim 1, wherein a retaining ring for holding the rod-shaped member is attached to the hole as the retaining structure. The electric actuator according to claim 1, wherein the linear motion member and the protrusion are integrally provided as the retaining structure.

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