JP2023043475A - electric actuator - Google Patents

Abstract

To facilitate attachment work of a buffer member to a screw shaft.SOLUTION: In an electric actuator 1, a screw shaft 31 forming a ball screw 30 serving as a motion conversion mechanism is provided with: a recessed part 31c which is open on the other end surface 31b; and a pin insertion hole 31d which penetrates through the screw shaft 31 in a radial direction in an axial range of the recessed part 31c. A fitting protruding part 73b of a buffer member 73 formed of an elastic material is fitted in the recessed part 31c. The fitting protruding part 73b has a pair of claw parts 73c which are disposed spaced apart from each other in the radial direction. The pair of claw parts 73c sandwiches a pin 71 inserted into the pin insertion hole 31d.SELECTED DRAWING: Figure 3

Description

The present invention relates to an electric actuator.

For example, in Patent Document 1 below, a motion conversion mechanism that converts the rotary motion of an electric motor into linear motion and outputs it is provided with a nut that rotates upon receiving the rotary motion of the electric motor and an axial motion that changes depending on the direction of rotation of the nut. An electric actuator employing a screw mechanism having a screw shaft that advances on one side or retreats on the other side in the axial direction is described. An electric actuator having such a screw mechanism is provided with a rotation restricting portion for restricting rotation of a screw shaft as a linear motion member around its axis when the nut rotates. An outline of the conventional rotation restricting portion disclosed in Patent Document 1 will be described with reference to FIGS. 8(a) and 8(b). 8(a) is a partial vertical cross-sectional view of a conventional electric actuator, and FIG. 8(b) is a cross-sectional view taken along line YY of FIG. 8(a).

The rotation restricting portion 100 shown in FIGS. 8A and 8B includes a pin 102 attached to the screw shaft 101 with its longitudinal ends (both ends) protruding radially outward of the screw shaft 101, and an axial guide groove 105 formed in the inner periphery of a bottomed cylindrical shaft case 104 that accommodates the screw shaft 101 and into which the projecting portion of the pin 102 is fitted. The pin 102 supports a cylindrical rotating body (guide collar) 103 with its projecting portion, and the guide collar 103 is fitted in the guide groove 105 so as to be free to roll. In this case, the rotation of the screw shaft 101 is restricted by engaging the guide collar 103 supported by the projecting portion of the pin 102 with the guide groove 105 of the shaft case 104 in the circumferential direction of the screw shaft 101 .

Further, in order to prevent the shaft case 104 from being damaged when the rear end portion of the screw shaft 101 formed of a metal material collides with the bottom portion of the shaft case 104, the electric actuator of Patent Document 1 has a A cushioning member 106 made of an elastic material such as rubber is provided between the shaft case 104 and the bottom. The cushioning member 106 is attached to the rear end portion of the screw shaft 101 using the pin 102 that constitutes the rotation restricting portion 100 .

Specifically, in a state in which the fitting convex portion 106a of the cushioning member 106 is fitted into the concave portion 101b provided so as to open in the end surface (the end surface facing the inner bottom surface of the shaft case 104) 101a of the screw shaft 101, the screw is The pin 102 is press-fitted (tightening margin The cushioning member 106 is attached to the screw shaft 101 by inserting it with the

JP 2020-139575 A

When the cushioning member 106 is attached to the screw shaft 101 in the above manner, the pin 102 is attached to the pin 102 after the pin insertion hole 101c provided in the screw shaft 101 and the pin insertion hole 106b provided in the cushioning member 106 are aligned. It is necessary to press-fit into the insertion holes 101c and 106b. Since the screw shaft 101 (and the pin 102) is made of a highly rigid metal material, it is difficult to press-fit the pin 102 into both the pin insertion holes 101c and 106b. The attachment of 106 required a great deal of labor and cost.

SUMMARY OF THE INVENTION In view of such circumstances, it is an object of the present invention to provide an electric actuator in which a cushioning member is attached to the shaft end of a screw shaft, thereby simplifying the operation of attaching the cushioning member to the screw shaft, thereby reducing the manufacturing cost of the electric actuator. and

The first invention of the present application, which was created to achieve the above object,
Equipped with an electric motor and a motion conversion mechanism that converts rotary motion of the electric motor into linear motion,
The motion conversion mechanism has a nut that rotates by receiving the rotational motion of the electric motor, and a screw shaft that advances in one axial direction or retreats in the other axial direction depending on the direction of rotation of the nut,
The screw shaft is provided with a recess opening on the other end face in the axial direction, and a pin insertion hole radially penetrating the screw shaft within the axial range of the recess, and the recess is formed of an elastic material. In the electric actuator in which the fitting convex portion of the cushioning member is fitted,
The fitting convex portion has a pair of claw portions arranged facing each other with a gap in the radial direction, and the pin inserted into the pin insertion hole is sandwiched between the pair of claw portions. do.

According to such a configuration, after the pin is fitted into the pin insertion hole of the screw shaft, the pin is fitted into the pair of claws through the gap defined between the pair of claws formed in the fitting projection of the cushioning member. By inserting it between the claws, the pin attached to the screw shaft can be clamped in the radial direction by the pair of claws. In other words, according to the above-described configuration, the screw shaft is required when a conventional cushioning member [see FIGS. The cushioning member can be attached to the screw shaft (rotation restricting portion) without aligning the pin insertion hole of the cushioning member with the pin insertion hole of the cushioning member. As a result, it is possible to simplify the work of attaching the cushioning member, so that the assembly cost (manufacturing cost) of the electric actuator can be reduced.

The fitting of the pin into the pin insertion hole of the screw shaft may be loose fit or interference fit. In the case of loose fit, the pin can be inserted smoothly into the pin insertion hole. , has the advantage that the electric actuator can be easily assembled. On the other hand, in the case of interference fit, it is possible to prevent the pin inserted into the pin insertion hole (attached to the screw shaft) from falling off, so it is possible to improve the handling of the assembly in which the pin and the cushioning member are attached to the screw shaft. There are advantages such as being able to The definitions of "clearance fit" and "tight fit" conform to the definitions of "clearance fit" and "tight fit" specified in JIS B 0401-1. The same applies hereinafter in this specification.

In addition, the second invention of the present application, which has been devised to achieve the above object, is an electric actuator having the same premise structure as the first invention (the screw shaft is provided with a recess opening on the other end face in the axial direction). , an electric actuator in which a pin insertion hole radially penetrating the screw shaft is provided within the axial range of the recess, and a fitting protrusion of a cushioning member formed of an elastic material is fitted in the recess ,
The cushioning member is attached to the screw shaft by fitting a projection provided on the outer peripheral surface of the fitting projection into a groove provided on the inner peripheral surface of the recess, and the fitting projection is a pin It is characterized by terminating on the other side in the axial direction of the pin inserted into the insertion hole.

According to such a configuration, the cushioning member can be attached to the screw shaft independently of the pin that constitutes the rotation restricting portion of the screw shaft. Therefore, for example, by fitting the projection provided on the outer peripheral surface of the fitting convex portion of the cushioning member into the groove provided on the inner peripheral surface of the concave portion of the screw shaft in a state where the pin is inserted into the pin insertion hole of the screw shaft, The attachment of the cushioning member to the screw shaft can be completed. Alternatively, after fitting the projection provided on the outer peripheral surface of the fitting projection into the groove provided on the inner peripheral surface of the concave portion of the screw shaft (after attaching the cushioning member to the screw shaft), the pin is inserted into the pin insertion hole of the screw shaft. can be inserted. In other words, even with such a configuration, the pin insertion hole of the screw shaft and the pin insertion hole of the buffer member, which are required when attaching a conventional buffer member having a pin insertion hole in the fitting convex portion, to the screw shaft. The cushioning member can be attached to the screw shaft without alignment. As a result, it is possible to simplify the work of attaching the cushioning member, so that the assembly cost (manufacturing cost) of the electric actuator can be reduced.

In addition, the third invention of the present application, which was invented to achieve the above object,
Equipped with an electric motor and a motion conversion mechanism that converts rotary motion of the electric motor into linear motion,
The motion conversion mechanism has a nut that rotates by receiving the rotational motion of the electric motor, and a screw shaft that advances in one axial direction or retreats in the other axial direction depending on the direction of rotation of the nut,
The screw shaft is provided with a recess opening on the other end face in the axial direction, and a pin insertion hole radially penetrating the screw shaft within the axial range of the recess, and the recess is formed of an elastic material. In the electric actuator in which the fitting convex portion of the cushioning member is fitted,
The pin is inserted into the pin insertion hole with a clearance fit, and the pin is inserted into a through hole radially penetrating the fitting convex portion with an interference fit.

According to such a configuration, when attaching the cushioning member to the screw shaft, although it is still necessary to align the pin insertion hole of the screw shaft with the pin insertion hole of the cushioning member, it is formed of a highly rigid metal material. , the pin can be smoothly inserted into the pin insertion hole of the screw shaft, which is generally used. This facilitates the work of inserting the pins into the pin insertion holes of the screw shaft and the cushioning member, that is, the work of attaching the cushioning member to the screw shaft via the pins.

The first to third inventions of the present application described above can be preferably applied to, for example, an electric actuator in which the screw shaft is arranged parallel to the output shaft of the electric motor.

As described above, according to the present invention, it is possible to simplify the operation of attaching the cushioning member to the screw shaft in the electric actuator in which the cushioning member is attached to the shaft end of the screw shaft. This makes it possible to reduce the manufacturing cost of the electric actuator.

1 is a schematic longitudinal sectional view of an electric actuator according to an embodiment of the present invention (first invention). FIG. FIG. 2 is a schematic perspective view of the electric actuator shown in FIG. 1; FIG. 2 is a cross-sectional view taken along the line AA of FIG. 1; FIG. 2 is a cross-sectional view taken along line BB of FIG. 1; 2 is a schematic perspective view of a cushioning member that constitutes the electric actuator shown in FIG. 1; FIG. FIG. 6 is a partial schematic cross-sectional view of an electric actuator according to an embodiment of the second invention; (a) is a schematic perspective view of a cushioning member used in an electric actuator according to an embodiment of the third invention, and (b) is a partial schematic cross-sectional view of the same electric actuator. (a) is a partial vertical cross-sectional view of a conventional electric actuator, and (b) is a cross-sectional view taken along line YY in FIG. (a).

An embodiment of the first invention of the present application will be described below with reference to FIGS. 1 to 5. FIG. 1 is a schematic longitudinal sectional view of an electric actuator 1 according to an embodiment of the first invention, FIG. 2 is a schematic perspective view of the electric actuator 1, and FIG. 3 is a line AA of FIG. 4 is a cross-sectional view taken along line BB in FIG. 1, and FIG.

An electric actuator 1 shown in FIG. A driving force transmission portion 4 that transmits a driving force to the motion conversion mechanism portion 3 , a support portion 5 that supports the motion conversion mechanism portion 3 , and a lock mechanism portion 6 that restricts driving of the motion conversion mechanism portion 3 . The drive section 2 of this embodiment is composed of a motor section 8 and a speed reduction mechanism section 9 . The “axial direction” used to indicate directionality in the following description is the direction along the axial center of the electric motor 10 that constitutes the motor section 8 unless otherwise specified. In the "axial direction", the side on which the motor section 8 is arranged (the left side of the paper surface of FIG. 1) and the side on which the lock mechanism section 6 is arranged (the right side of the paper surface of FIG. 1) are referred to as "one axial side" and It is also called “the other side in the axial direction”.

The motor unit 8 includes an electric motor 10 for driving an actuator, and a motor case 11 housing the electric motor 10 . For the electric motor 10, a motor capable of detecting the rotation angle of the output shaft 10a, such as a three-phase brushless motor, is preferably used. The motor case 11 includes a case body 12 and a sealing member 13 that seals an end opening on one side in the axial direction of the case body 12 .

The speed reduction mechanism 9 includes a speed reducer 15 that reduces the speed of rotation of the motor unit 8 (electric motor 10) and outputs the reduced speed, and a speed reducer case 16 that houses the speed reducer 15 . The speed reducer case 16 is detachably connected to the case body 12 of the motor case 11 that is adjacently arranged on one side in the axial direction.

The speed reducer 15 of this embodiment includes a sun gear 17 that is rotatable integrally with the output shaft 10 a of the electric motor 10 , a ring gear 18 that is provided on the inner circumference of the speed reducer case 16 , and a A planetary gear reducer provided with a plurality of (for example, three) planetary gears 19 which are disposed in the rim and are meshed with the sun gear 17 and the ring gear 18, and a planetary gear holder 20 and a planetary gear carrier 21 which rotatably hold the planetary gears 19 is. The planetary gear carrier 21 integrally has an annular portion 21a connected to the planetary gear 19 and a cylindrical portion 21b extending from the inner diameter end portion of the annular portion 20a to the other side in the axial direction. Take out and output. The cylindrical portion 21b of the planetary gear carrier 21 is connected to (the inner ring of) a rolling bearing 46 and a gear boss 44, which will be described later, so as to be able to rotate integrally therewith.

The rotation of the electric motor 10 is reduced by the speed reducer 15 and then transmitted to the driving force transmission section 4 and further to the motion conversion mechanism section 3 . As a result, the rotational torque of the driving force transmission section 4 can be increased, so that a small electric motor 10 can be employed.

The motion conversion mechanism 3 of this embodiment includes a ball screw 30 as a motion conversion mechanism and a shaft case 35 . The ball screw 30 includes a screw shaft 31 arranged parallel to the output shaft 10a of the electric motor 10, a nut 32 rotatably fitted to the outer circumference of the screw shaft 31 via a large number of balls 33, and a circulation member. A top 34 is provided. A large number of balls 33 are loaded between a spiral groove 31a formed on the outer peripheral surface of the screw shaft 31 and a spiral groove 32a formed on the inner peripheral surface of the nut 32, and a top 34 is incorporated. With such a configuration, when the screw shaft 31 axially advances and retreats (moves forward to one side in the axial direction or moves backward to the other side in the axial direction) as the nut 32 rotates, the two-helical Balls 33 circulate between grooves 31a and 32a.

The screw shaft 31 also functions as an output member of the electric actuator 1, and an operation portion C for outputting (transmitting) linear motion of the screw shaft 31 to an operation target is provided at one axial end thereof. is provided. In the illustrated example, the operation portion C is configured by a radial through hole into which a connecting member for connecting the operation target and the screw shaft 31 is inserted. The screw shaft 31 having the above configuration is made of a highly rigid metal material such as stainless steel.

The shaft case 35 has a bottomed tubular shape integrally having a tubular portion 35a and a bottom portion 35b, and (a part of) the screw shaft 31 is accommodated in the tubular portion 35a. The shaft case 35 also integrally has a cylindrical holder portion 35 d that accommodates the lock mechanism portion 6 , and is detachably connected to the transmission gear case 45 that constitutes the driving force transmission portion 4 . Although the details will be described later, the shaft case 35 also functions as a component of the rotation restricting portion 70 for restricting the screw shaft 31 from rotating around its axis when the nut 32 rotates.

The electric actuator 1 includes a position detection device for detecting the forward/backward movement amount (axial position) of the screw shaft 31 . This position detection device mainly includes a magnetic sensor 36 (see FIG. 2) as a stroke sensor attached to the motor case 11, and a permanent magnet 37 as a sensor target attached to the screw shaft 31 via a holding member 38. Consists of In this case, when the screw shaft 31 moves back and forth in the axial direction, the magnetic sensor 36 detects a change in the magnetic field (for example, the direction and strength of the magnetic flux density) of the permanent magnet 37 that moves along with the movement of the screw shaft. 31 forward and backward movement amounts are detected.

The driving force transmission unit 4 includes a transmission gear mechanism 41 that transmits the output of the drive unit 2 (reduction mechanism unit 9) to the motion conversion mechanism unit 3, and a transmission gear case 45 that accommodates the transmission gear mechanism 41. The transmission gear case 45 is detachably connected to the speed reducer case 16 arranged adjacently on one side in the axial direction.

The transmission gear mechanism 41 includes a driving-side drive gear 42, a driven-side driven gear 43 meshing therewith, and a gear boss 44 arranged on the inner circumference of the drive gear 42. The gear boss 44 extends along the axial direction of the drive gear 42. It is rotatably supported by rolling bearings 46 and 47 arranged on both sides. The rolling bearing 46 is mounted on the inner periphery of the transmission gear case 45 , and the rolling bearing 47 is mounted on the inner periphery of the bearing case 51 forming the support portion 5 .

The gear boss 44 is formed in a stepped cylindrical shape integrally having a small-diameter cylindrical portion 44a and a large-diameter cylindrical portion 44b, and is arranged coaxially with the rotating shaft 10a of the electric motor 10. As shown in FIG. The inner peripheral surface of the cylindrical portion 21a of the planetary gear carrier 21 is press-fitted to the outer peripheral surface of the small-diameter cylindrical portion 44a, and the inner peripheral surface of the drive gear 42 is press-fitted to the outer peripheral surface of the large-diameter cylindrical portion 44b.

The driven gear 43 has a cylindrical nut mounting portion 43a arranged radially outwardly of the nut 32 of the ball screw 30. In this embodiment, the outer peripheral surface of the nut 32 is press-fitted into the inner peripheral surface of the nut mounting portion 43a. ing.

With the above configuration, when the output shaft 10a of the electric motor 10 rotates and its rotational driving force is transmitted to the gear boss 44 via the speed reducer 15, the gear boss 44 and the drive gear 42 rotate integrally, and the gear boss 44 rotates. The driven gear 43 and the nut 32 of the ball screw 30, which are in mesh with each other, rotate together. As a result, the screw shaft 31 advances in one axial direction or retreats in the other axial direction depending on the rotation direction of the nut 32 (the output shaft 10a of the electric motor 10), and is connected to the operation portion C of the screw shaft 31. The target of operation is operated.

The transmission gear case 45 has a cylindrical portion 45a in which a portion of the screw shaft 31 is accommodated. A tubular boot 47 is attached between the cylindrical portion 45 a and the screw shaft 31 . The boot 47 is formed of an elastic material such as a rubber material or a thermoplastic elastomer, and integrally has a small-diameter tubular portion 47a, a large-diameter tubular portion 47b, and a bellows portion 47c connecting the tubular portions 47a and 47b. The small-diameter tubular portion 47a is tightened and fixed to the screw shaft 31 by a boot band 48A, and the large-diameter tubular portion 47b is tightened and fixed to the cylindrical portion 45a of the transmission gear case 45 by a boot band 48B. With such a configuration, the transmission gear case 45 (a casing of the electric actuator 1 formed by connecting the transmission gear case 45, the speed reducer case 16, the motor case 11, the shaft case 35, and a bearing case 51 described later). Intrusion of foreign matter and external leakage of lubricant such as grease interposed in the casing are prevented.

The support portion 5 includes a support bearing 50 that rotatably supports the nut 32 of the ball screw 30 and a bearing case 51 that accommodates the support bearing 50 . The bearing case 51 is detachably connected to the transmission gear case 45 arranged adjacently on one side in the axial direction.

The support bearing 50 is a double-row angular contact ball comprising an outer ring 50a, an inner ring 50b, and double-row balls 50c arranged to roll freely between them, and capable of supporting a radial load and an axial load in both directions. Bearings are used. Between the bearing case 51 and the support bearing 50 , a flanged cylindrical sleeve 52 integrally having a radially inward flange 52 a is arranged. Positioning in the axial direction is achieved by sandwiching between the portion 52a and a retaining ring 53 attached to the inner peripheral surface of the sleeve 52. As shown in FIG. On the other hand, the inner ring 50b of the support bearing 50 is sandwiched between the driven gear 43 and a retaining ring 54 mounted on the outer peripheral surface of the nut 32, so that it is positioned in the axial direction.

The lock mechanism portion 6 includes a lock member 61 and a lock motor (for example, a DC motor) 64 that generates a driving force for moving the lock member 61 back and forth in the axial direction. A sliding screw shaft 63 is attached to the output shaft of the locking motor 64 so as to be rotatable therewith, and a sliding screw nut 62 that holds the lock member 61 fixedly is screwed onto the outer circumference of the sliding screw shaft 63 . are doing. The locking motor 64 is housed in a cylindrical holder portion 35d provided in the shaft case 35 while being electrically connected to a power source (for example, a power source common to the power source of the electric motor 10). , the end opening on the other side in the axial direction of the holder portion 35d is sealed with a cap 65 attached to the holder portion 35d.

The lock member 61 has a non-circular portion with a non-circular cross section inserted into a non-circular (for example, rectangular) through hole 51 a provided in the bearing case 51 . As a result, when the output shaft of the locking motor 64 rotates, the locking member 61 that receives the rotational power moves forward and backward in the axial direction while being prevented from rotating. The lock member 61 moves forward and backward in the axial direction between two positions: a restricting position restricting power transmission between the driving portion 2 and the nut 32 of the ball screw 30, and a permitting position permitting the power transmission. Note that FIG. 1 shows a state in which the lock member 61 is positioned at the restricted position.

A drive gear 42 is arranged in the direction in which the lock member 61 advances, and the drive gear 42 is formed with a hole portion 42a into which the non-circular portion of the lock member 61 is inserted. The regulated position in the present embodiment is a position where the non-circular portion of the lock member 61 is inserted into the hole 42a of the drive gear 42 and the lock member 61 and the drive gear 42 are engaged in the rotational direction of the drive gear 42. defined as In this case, when the lock member 61 is positioned at the restricted position, the rotation of the drive gear 42 is restricted, so that the electric actuator 1 rotates the nut 32 (progressive and retractive movement of the screw shaft 31), that is, outputs linear motion to the operation target. is locked. On the other hand, although not shown, the lock member 61 moves backward until the non-perfect circular portion of the lock member 61 is completely separated from the hole 42a of the drive gear 42 (the lock member 61 is positioned at the allowable position). Then, the engagement state between the lock member 61 and the drive gear 42 is released, so that the unlocked state is established in which the rotation of the drive gear 42 and the nut 32 and the forward and backward movement of the screw shaft 31 are allowed.

The lock mechanism section 6 of this embodiment having the above configuration operates as follows.
First, in the driving state of the electric motor 10, the locking member 61 is held at the allowable position. When the electric motor 10 is de-energized in this state, the locking motor 64 is driven to move the locking member 61 forward from the allowable position toward the restricting position. When the lock member 61 is positioned at the restricted position, the locking motor 64 is stopped and the lock member 61 is held at the restricted position. After that, when the energization of the electric motor 10 is resumed, the locking motor 64 is driven to move the locking member 61 backward from the restricting position toward the permitting position. When the lock member 61 is positioned at the allowable position, the locking motor 64 stops and the lock member 61 is held at the allowable position.

In order to accurately switch between the locked state and the unlocked state, the lock mechanism portion 6 is provided with a detection portion 66 for detecting the axial position (stroke amount) of the lock member 61 . The detector 66 of the present embodiment indirectly detects the axial position of the locking member 61 by detecting the axial position of the sliding screw nut 62 holding the locking member 61 .

As shown in FIGS. 1, 3 and 4, the other end (rear end) of the screw shaft 31 in the axial direction is provided so as to prevent the screw shaft 31 from rotating around its axis when the nut 32 rotates. A rotation restricting portion 70 for restricting is provided. The rotation restricting portion 70 is supported by an axial guide groove 35c formed in the inner circumference of the cylindrical portion 35a of the shaft case 35 and a radial support shaft provided on the screw shaft 31 in the guide groove 35c. The guide groove 35c and the guide collar 72 are provided at two locations facing each other at 180° with the axis of the screw shaft 31 interposed therebetween. The rear end of the screw shaft 31 is formed with a recess 31c opening to the other end surface 31b and a pin insertion hole 31d radially penetrating the screw shaft 31 within the axial range of the recess 31c. In the pin insertion hole 31d, a pin 71 as the supporting shaft made of a metal material such as stainless steel is protruded radially outward of the screw shaft 31 (into the guide groove 35c). It is inserted in a closed state). In this embodiment, the pin 71 is inserted (press-fitted) into the pin insertion hole 31d with an interference.

The guide collar 72 is made of a resin material mainly composed of thermoplastic resin such as polyacetal (POM), polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), polyether ether ketone (PEEK), etc. It is tightly fitted. The guide groove 35c has a concave cross-sectional shape defined by a pair of groove side surfaces parallel to each other and a groove bottom surface connecting both groove side surfaces, and the groove width (separation distance between the pair of groove side surfaces) is , is set larger than the outer diameter of the cylindrical guide collar 72 . With such a configuration, when the screw shaft 31 advances and retreats in the axial direction, the guide collar 72 is rotatably supported by the support pin 71 and can smoothly roll on the groove side surface of the guide groove 35c.

The electric actuator 1 has a cushioning member 73 made of an elastic material such as rubber or thermoplastic elastomer. 73a and a fitting protrusion 73b fitted to the recess 31c of the screw shaft 31 are integrally provided. By providing such a buffer member 73, even if the screw shaft 31 collides with the bottom portion 35b of the shaft case 35, the impact load can be absorbed and alleviated by the buffer member 73 (the head portion 73a thereof). Therefore, it is possible to reduce the possibility that the shaft case 35 is damaged.

The cushioning member 73 is attached to the screw shaft 31 . As shown in FIGS. 3 and 5, the cushioning member 73 of this embodiment has a pair of claw portions 73c in which the fitting convex portion 73b is spaced apart in the radial direction of the screw shaft 31 and opposed to each other. The pin 71 inserted (press-fitted) into the pin insertion hole 31d of the screw shaft 31 is radially clamped by the pin restraining portion 73e formed by the cooperation of the pair of claw portions 73c. installed.

According to such a configuration, for example, after the pin 71 is inserted into the pin insertion hole 31d of the screw shaft 31, the gap 73d is formed between the pair of claw portions 73c formed on the fitting convex portion 73b of the cushioning member 73. By introducing the pin 71 into the pin restraining portion 73e (see FIG. 5) via the pin 71 (see FIG. 5), the pin 71 attached to the screw shaft 31 can be clamped by the pair of claw portions 73c. That is, according to the above configuration, it is necessary to attach the conventional cushioning member 106 having the pin insertion hole 106b in the fitting convex portion 106a shown in FIGS. The cushioning member 73 can be attached to the screw shaft 31 without aligning the pin insertion hole 101c of the screw shaft 101 and the pin insertion hole 106b of the cushioning member 106, which has been described above. This simplifies the mounting work of the buffer member 73, so that the assembly cost (manufacturing cost) of the electric actuator 1 can be reduced.

In this embodiment, the pin 71 is press-fitted into the pin insertion hole 31d of the screw shaft 31 (the pin 71 is tightly fitted into the pin insertion hole 31d). In this case, it is possible to prevent the pin 71 attached to the screw shaft 31 (inserted into the pin insertion hole 31d) from coming off, so that the handleability of the assembly in which the pin 71 and the buffer member 73 are attached to the screw shaft 31 is improved. It has the advantage of being able to However, the fit of the pin 71 into the pin insertion hole 31d may be a clearance fit. In the case of loose fitting, the pin 71 can be smoothly inserted into the pin insertion hole 31d. There is an advantage that the electric actuator 1 (the assembly described above) can be easily assembled without having to

Hereinafter, the electric actuator 1 according to the embodiment of the second invention of the present application will be described with reference to FIG. Only the configuration different from the actuator 1 will be described.

FIG. 6 is a partial longitudinal sectional view of the electric actuator 1 according to the second embodiment of the invention of the present application. In this embodiment, an annular projection 73f provided on the outer peripheral surface of the fitting projection 73b of the cushioning member 73 is fitted into a groove (annular groove) 31c1 provided on the inner peripheral surface of the recess 31c of the screw shaft 31. The cushioning member 73 is attached to the screw shaft 31, and the fitting convex portion 73b of the cushioning member 73 terminates on the other side in the axial direction of the pin 71 inserted into the pin insertion hole 31d of the screw shaft 31. there is That is, the end portion of the fitting protrusion 73b on one side in the axial direction is located on the other side in the axial direction relative to the pin 71, and the fitting protrusion 73b of the cushioning member 73 is not in contact with the pin 71 (the pin 71 and spaced apart).

According to such a configuration, the cushioning member 73 can be attached to the screw shaft 31 independently of the pin 71 that constitutes the rotation restricting portion 70 of the screw shaft 31 . Therefore, for example, when the pin 71 is inserted into the pin insertion hole 31d of the screw shaft 31, the protrusion 73f provided on the outer peripheral surface of the fitting projection 73b of the cushioning member 73 is provided on the inner peripheral surface of the recess 31c of the screw shaft 31. The attachment of the cushioning member 73 to the screw shaft 31 can be completed by fitting it into the groove 31c1. Alternatively, after fitting the projection 73f provided on the outer peripheral surface of the fitting projection 73b into the groove 31c1 provided on the inner peripheral surface of the recess 31c of the screw shaft 31 (after attaching the buffer member 73 to the screw shaft 31), the screw A pin 71 can be inserted into the pin insertion hole 31 d of the shaft 31 .

8(a) and 8(b). The cushioning member 73 can be attached to the screw shaft 31 without aligning the pin insertion hole 101c of the screw shaft 101 and the pin insertion hole 106b of the cushioning member 106. This simplifies the mounting work of the buffer member 73, so that the assembly cost (manufacturing cost) of the electric actuator 1 can be reduced.

Hereinafter, an electric actuator 1 according to an embodiment of the third invention of the present application will be described with reference to FIGS. 7(a) and 7(b). Only the configuration different from the electric actuator 1 according to the embodiment will be described.

FIG. 7(a) is a perspective view of a cushioning member 73 used in an electric actuator 1 according to a third embodiment of the present invention, and FIG. 7(b) is a partial longitudinal sectional view of the same electric actuator 1. be. In the electric actuator 1 of this embodiment, the cushioning member 73 is similar to the conventional cushioning member 106 shown in FIGS. 8(a) and 8(b). That is, as shown in FIG. 7(a), the cushioning member 73 used in this embodiment integrally has a head portion 73a and a (solid) fitting projection 73b. 73b is provided with a pin insertion hole 73g passing therethrough in the radial direction. Then, the pin 71 is inserted into the pin insertion hole 31d provided in the screw shaft 31 with loose fit, and the pin 71 is inserted into the pin insertion hole 73g provided in the fitting convex portion 73b of the buffer member 73 with interference fit. It is

According to such a configuration, when the cushioning member 73 is attached to the screw shaft 31 (via the pin 71), the alignment between the pin insertion hole 31d of the screw shaft 31 and the pin insertion hole 73g of the cushioning member 73 remains unchanged. Although necessary, it is possible to smoothly insert the pin 71 into the pin insertion hole 31d of the screw shaft 31 made of a highly rigid metal material. This facilitates the work of inserting the pin 71 into the pin insertion holes 31d and 73g of the screw shaft 31 and the buffer member 73, that is, the work of attaching the buffer member 73 to the screw shaft 31 via the pin 71.

The electric actuator 1 according to the embodiment of the present invention (the first to third inventions of the present application) has been described above, but the electric actuator 1 may be modified as appropriate without departing from the gist of the present invention. can be done.

For example, the motion conversion mechanism 3 may be configured by a so-called slide screw, which is substantially composed only of a screw shaft 31 and a nut 32 rotatably fitted to the outer circumference of the screw shaft 31, without the ball 33 and the top 34. is also possible. Further, according to the present invention, the speed reduction mechanism portion 9 is omitted, and the driving portion 2 is substantially composed only of the motor portion 8 (rotational driving force of the electric motor 10 is transmitted as it is to the transmission gear mechanism portion 4). It can also be applied to the actuator 1.

The present invention is by no means limited to the above-described embodiments, and can of course be embodied in various forms without departing from the gist of the present invention. It is defined by the claims, and includes all changes within the meaning of equivalents and the scope of the claims.

Reference Signs List 1 electric actuator 3 motion conversion mechanism 10 electric motor 31 screw shaft 31c recess 32 nut 35 shaft case 35c guide groove 70 rotation restricting portion 71 pin 73 cushioning member 73a head 73b fitting protrusion 73c claw 73d gap 73f protrusion 73g pin insertion hole

Claims (4)

Equipped with an electric motor and a motion conversion mechanism that converts rotary motion of the electric motor into linear motion,
The motion conversion mechanism has a nut that rotates by receiving the rotational motion of the electric motor, and a screw shaft that advances in one axial direction or retreats in the other axial direction depending on the direction of rotation of the nut,
The screw shaft is provided with a recess opening on the other end face in the axial direction, and a pin insertion hole radially penetrating the screw shaft within the axial range of the recess, and the recess is made of an elastic material. In the electric actuator in which the fitting convex portion of the formed cushioning member is fitted,
wherein the fitting convex portion has a pair of claw portions arranged opposite to each other with an interval in the radial direction, and the pin inserted into the pin insertion hole is sandwiched between the pair of claw portions. actuator. Equipped with an electric motor and a motion conversion mechanism that converts rotary motion of the electric motor into linear motion,
The motion conversion mechanism has a nut that rotates by receiving the rotational motion of the electric motor, and a screw shaft that advances in one axial direction or retreats in the other axial direction depending on the direction of rotation of the nut,
The screw shaft is provided with a recess opening on the other end face in the axial direction, and a pin insertion hole radially penetrating the screw shaft within the axial range of the recess, and the recess is made of an elastic material. In the electric actuator in which the fitting convex portion of the formed cushioning member is fitted,
The cushioning member is attached to the screw shaft by fitting a projection provided on the outer peripheral surface of the fitting protrusion into a groove provided on the inner peripheral surface of the recess, and the fitting protrusion is An electric actuator, wherein the pin inserted into the pin insertion hole terminates on the other side in the axial direction. Equipped with an electric motor and a motion conversion mechanism that converts rotary motion of the electric motor into linear motion,
The motion conversion mechanism has a nut that rotates by receiving the rotational motion of the electric motor, and a screw shaft that advances in one axial direction or retreats in the other axial direction depending on the direction of rotation of the nut,
The screw shaft is provided with a recess opening on the other end face in the axial direction, and a pin insertion hole radially penetrating the screw shaft within the axial range of the recess, and the recess is made of an elastic material. In the electric actuator in which the fitting convex portion of the formed cushioning member is fitted,
An electric actuator according to claim 1, wherein a pin is inserted into said pin insertion hole with a clearance fit, and said pin is inserted into a through hole radially penetrating said fitting convex portion with an interference fit. The electric actuator according to any one of claims 1 to 3, wherein the screw shaft is arranged parallel to the output shaft of the electric motor.

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