JP2022051042A - Linear motion actuator - Google Patents

Abstract

To prevent generation of a lock state in a screw mechanism when an output portion axially collides with a stopper or a mating member during linear motion by a drive mechanism of a linear motion actuator.SOLUTION: A screw mechanism for converting torque of a first screw element 1 into axial thrust of a second screw element 2, and a drive mechanism 3 for imparting the torque to the screw element 1 are supported in a case 4. An output shaft 5 is disposed in a manner that it can be axially reciprocated to the screw elements 1, 2 and the case 4. First and second elastic elements 6, 7 are disposed between the output shaft 5 and the second screw element 2 so that thrust in a forward or backward direction, of the second screw element 2 is transmitted to the output shaft. The first and second elastic elements 6, 7 interlock the second screw element 2 and the output shaft 5 in the same direction when the output shaft 5 can be advanced or retreated, and stop the second screw element 2 by imparting elastic repulsion force equal to the thrust or more to the second screw element 2 when the output shaft 5 cannot be advanced or retreated in the axial direction.SELECTED DRAWING: Figure 1

Description

The present invention relates to a linear motion actuator including a screw mechanism that converts one rotary motion of a screw shaft and a nut into a linear motion of the other, and a drive mechanism that rotates one of the screw shaft and the nut in the forward and reverse directions. It relates to a unitized mechanism and drive mechanism in a case.

The linear motion actuator is roughly classified into a screw shaft rotation type in which a screw shaft is rotated to linearly move a nut and a nut rotation type in which a nut is rotated to linearly move a screw shaft.

Conventionally, a linear screw element of a screw mechanism (a nut for a screw shaft rotation type and a screw shaft for a nut rotation type) is configured as an output unit of a linear actuator.

In order to limit the stroke in which the output unit of the linear actuator moves linearly in the axial direction to a certain level, the axial movement of the linear motion screw element may be restricted at the end position of the stroke. As a regulating means, a stopper is provided on the case or the screw shaft so that the linear motion screw element, which is an output unit, is stopped by contact with the stopper (for example, Patent Document 1).

JP-A-2019-157952

However, if the position of the stopper is not appropriate due to the influence of various errors, the linear screw element, which is the output part of the linear actuator, collides with the stopper, and when the rotary screw element and the linear screw element are engaged, the screw mechanism is released. After that, even if a reverse rotational force is applied to the rotary screw element from the drive mechanism, the linear screw element may not be able to move, resulting in a locked state.

It is also conceivable to consider a usage environment in which the linear motion screw element, which is the output unit of the linear motion actuator, is arranged in a non-connected manner with the mating member. In such a usage environment, axial misalignment may occur when the mating member is positioned with respect to the linear actuator, or the mating member may move in the axial direction independently of the linear actuator. There is. Therefore, when the linearly driven screw element is advanced by the drive mechanism, the linearly driven screw element may collide with the mating member and the screw mechanism may reach a locked state.

In view of the above background, the problem to be solved by the present invention is the generation of a locked state in the screw mechanism when the output unit during linear motion by the drive mechanism of the linear motion actuator collides with the stopper or the mating member in the axial direction. It is to prevent.

In order to achieve the above problems, the present invention comprises a screw mechanism that converts the rotational force of the first screw element into an axial thrust of the second screw element, and a drive mechanism that applies the rotational force to the first screw element. In a linear motion actuator including a case for supporting the drive mechanism and the screw mechanism, an output shaft arranged so as to be reciprocally movable in the axial direction with respect to the first screw element, the second screw element, and the case. And, in a state where the output shaft is arranged between the output shaft and the second screw element so as to transmit the thrust in the forward direction of the second screw element to the output shaft, and the output shaft can move forward in the axial direction. When the second screw element and the output shaft are interlocked in the forward direction when transmitting the thrust in the forward direction, and the forward direction is transmitted when the output shaft cannot move forward in the axial direction. The first elastic element that applies an elastic repulsive force equal to or higher than the thrust of the second screw element to stop the advance of the second screw element, and the thrust in the backward direction of the second screw element is the output shaft. When the output shaft is arranged between the output shaft and the second screw element so as to transmit the thrust in the reverse direction while the output shaft can move backward in the axial direction, the second screw element and the second screw element are transmitted. When the output shaft is interlocked in the reverse direction and the thrust in the reverse direction is transmitted in a state where the output shaft cannot move backward in the axial direction, an elastic repulsive force equal to or higher than the thrust in the reverse direction is applied to the second screw element. A configuration is adopted that further includes a second elastic element that is given to stop the backward movement of the second screw element.

By adopting the above configuration, the output shaft is used as the output part of the linear actuator, and when the output shaft does not collide with the stopper or the mating member in the axial direction while the second screw element is moving forward or backward by the drive mechanism, the first elastic element or The thrust in the corresponding direction via the second elastic element is transmitted to the output shaft, and the output shaft is interlocked in the moving direction of the second screw element. On the other hand, if the output shaft collides with the stopper or the mating member in the axial direction while the second screw element is moving forward or backward by the drive mechanism, the second screw element moves forward or backward with respect to the output shaft, and the output shaft moves forward or backward. Or, as the reverse progresses, the corresponding first elastic element or second elastic element is compressed from the second screw element to increase the elastic repulsive force, and the elastic repulsive force becomes the thrust in the moving direction of the second screw element. When it becomes equal to or higher than that, the movement of the second screw element is stopped by the elastic repulsive force, so that the first screw element and the second screw element do not bite, thereby preventing the occurrence of the locked state in the screw mechanism. ..

Preferably, the second thread element has a hollow shaft extending in the axial direction, and the first elastic element and the second elastic element are arranged between the inside of the hollow shaft and the output shaft. The output shaft has an intermediate spring receiver protruding inward of the hollow shaft, and the second screw element is a rear spring that axially sandwiches the first elastic element with the rear end of the intermediate spring receiver. It may have a receiver and a front spring receiver that axially sandwiches the second elastic element with the front end of the intermediate spring receiver. In this way, the first elastic element and the second elastic element are held in the hollow shaft of the second screw element, and the elastic repulsive force of the first screw element and the second screw element is received by the common intermediate spring receiver and is intermediate. The first elastic element and the second elastic element can be expanded and contracted according to the moving direction of the output shaft with respect to the second screw element while preventing the spring receiver from tilting.

The hollow shaft of the second screw element is radially supported by the case, the intermediate spring receiver of the output shaft is radially supported by the hollow shaft, and the front spring of the second screw element. The receiver may support the output shaft in the radial direction. In this way, the intermediate spring receiver and the front spring receiver can be used for the support structure of the output shaft with respect to the hollow shaft, and the hollow shaft can be supported and stabilized in the radial direction by the case.

The second screw element may have a nut screw-fitted to the first screw element, and the hollow shaft of the second screw element and the rear spring receiver may be integrally formed with the nut. In this way, the output shaft, the first and second elastic elements and the nut can be assembled into the subunit simply by attaching the front spring holder to the nut with the output shaft, the first and second elastic elements inserted in the hollow shaft. be able to.

The case may have a front stopper and a rear stopper that constantly limit the stroke of the output shaft with respect to the case by contact with the output shaft. By doing so, the stroke amount of the forward advance and the backward advance of the output shaft can be accurately determined by the linear actuator alone without depending on the mating member on the driven side.

As described above, in the present invention, by adopting the above configuration, when the output shaft as the output portion during linear motion by the drive mechanism of the linear motion actuator collides with the stopper portion or the mating member in the axial direction, the first elastic element. Alternatively, since the elastic repulsive force of the second elastic element can stop the axial movement of the second screw element with respect to the first screw element, it is possible to prevent the occurrence of a locked state in the screw mechanism.

A vertical sectional view showing a linear actuator according to an embodiment of the present invention. Enlarged view of the vicinity of the screw mechanism in FIG. Sectional view of line III-III of FIG. A vertical sectional view showing a state in which the output shaft of the linear actuator is advanced from the state shown in FIG.

Hereinafter, embodiments as an example of the present invention will be described with reference to FIGS. 1 to 4 attached.

The linear actuators shown in FIGS. 1 and 2 have a screw mechanism that converts the rotational force of the first screw element 1 into an axial thrust of the second screw element 2, and a drive mechanism that applies the rotational force to the first screw element 1. 3, a case 4 that supports the drive mechanism 3 and the above-mentioned screw mechanism, and an output shaft 5 that is arranged so as to be reciprocally movable in the axial direction with respect to the first screw element 1, the second screw element 2, and the case 4. , A first elastic element 6 and a second elastic element 7 interposed between the output shaft 5 and the second screw element 2. Here, the axial direction means the direction along the rotation axis of the first screw element 1. Hereinafter, the direction perpendicular to the rotation axis is referred to as a radial direction, and the circumferential direction that goes around the rotation axis is referred to as a circumferential direction.

The first screw element 1 is arranged so as to be rotatable with respect to the case 4 and immovable in the axial direction. The first screw element 1 is composed of a screw shaft 8 having a male screw portion, a bearing 9 attached to the screw shaft 8, and a retaining ring 10 attached to the screw shaft 8.

The screw shaft 8 has a hollow shaft shape opened at an end opposite to the male screw portion. The bearing 9 is for supporting the side of the screw shaft 8 opposite to the male screw so as to be rotatable and axially immovable with respect to the case 4. The bearing 9 is a non-separable rolling bearing. The retaining ring 10 is attached to a retaining ring groove formed in the screw shaft 8. The inner ring of the bearing 9 is regulated in the axial direction by the shoulder portion of the screw shaft 8 and the retaining ring 10. The outer ring of the bearing 9 is regulated in the axial direction by the shoulder portion of the case 4 and the retaining ring 11 attached to the case 4. The retaining ring 11 is attached to a retaining ring groove formed on the inner circumference of the case 4.

The second screw element 2 is arranged so as to be non-rotatable and movable in the axial direction with respect to the case 4. The second screw element 2 includes a nut 12 screw-fitted to the male screw of the screw shaft 8 of the first screw element 1, a front spring receiver 13 that receives the front end of the second elastic element 7 in the axial direction, and the inside of the nut 12. It is composed of a retaining ring 14 attached to the. Here, the direction in which the second screw element 2 moves to the right in the figure in the axial direction is the forward direction, and the direction in which the second screw element 2 moves to the left in the figure in the axial direction is the reverse direction.

The nut 12 has a female thread portion 12a, a hollow shaft 12b extending in the axial direction, a rear spring receiver 12c that receives the rear end of the first elastic element 6 in the axial direction, and a detent for the second thread element 2. A plurality of pin insertion grooves 12d are integrally formed.

The hollow shaft 12b has a cylindrical shape that extends forward coaxially with the female thread portion 12a. The inner circumference of the hollow shaft 12b has a cylindrical surface shape, and the inner diameter thereof is larger than the inner diameter of the male screw portion 12a. The outer diameter surface of the nut 12 including the outer diameter surface of the hollow shaft 12b is radially supported inside the case 4, and is a fitting surface that slidably contacts the inside of the case 4 in the axial direction. There is. Further, due to this support, the nut 12 is arranged coaxially with the screw shaft 8 of the first screw element 1.

The rear spring receiver 12c is formed of a stepped surface for providing an inner diameter difference between the female screw portion 12a and the hollow shaft 12b. The pin insertion groove 12d extends axially from the outside of the nut 12. As shown in FIG. 3, the plurality of pin insertion grooves 12d are formed at a plurality of locations in the circumferential direction evenly arranged.

The front spring receiver 13 shown in FIGS. 1 and 2 is composed of a washer fitted inside the hollow shaft 12b. The front spring receiver 13 is interposed between the hollow shaft 12b and the output shaft 5 inserted inside the hollow shaft 12b. The front spring receiver 13 supports the output shaft 5 in the radial direction. The inner diameter surface of the front spring receiver 13 is a fitting surface that slidably contacts the output shaft 5 in the axial direction. The retaining ring 14 is attached to a retaining ring groove formed in the hollow shaft 12b. The retaining ring 14 prevents the forward spring receiver 13 from advancing with respect to the hollow shaft 12b against the elastic rebound force generated by the second elastic element 7.

The drive mechanism 3 includes an electric motor having a drive shaft 15. The drive mechanism 3 can rotate the drive shaft 15 in the forward and reverse directions. The hollow portion of the drive shaft 15 and the screw shaft 8 is fitted so as to be able to transmit a rotational force in either the forward or reverse rotation direction. The rotation transmission member 16 attached to the drive shaft 15 is radially joined to the hollow portion of the screw shaft 8 at a position where it radially overlaps with the bearing 9. As the rotation transmission member, a polygonal shape such as a width across flats or a D-cut, a spline, or the like is applied. An example in which the drive shaft 15 of the drive mechanism 3 and the first screw element 1 are directly connected is shown, but the drive shaft and the first screw element are arranged in parallel, or a rotational force is applied between the drive shaft and the first screw element. It is also possible to add a gear mechanism to transmit.

The case 4 includes a screw case 17 that supports the first screw element 1 and the second screw element 2, a motor case 18 that supports the drive mechanism 3, and a front end case 19 that is abutted with the mating device 100 in the axial direction. Has been done.

The inner circumference of the screw case 17 supports the outside of the nut 12 including the hollow shaft 12b in the radial direction and guides the screw case 17 in the axial direction. As shown in FIGS. 2 and 3, a plurality of pin insertion grooves 17a are formed on the inner circumference of the screw case 17. The pin insertion groove 17a extends axially so as to face the pin insertion groove 12d of the nut 12 in the radial direction. The pin 20 is inserted between the pin insertion groove 12d of the nut 12 and the pin insertion groove 17a of the screw case 17. When a rotational force is applied to the nut 12 by the plurality of pin insertion grooves 12d, pins 20 and pin insertion grooves 17a, the pins 20 pushed in the rotational direction by the pin insertion grooves 12d of the nut 12 are pin insertion grooves of the screw case 17. Since it engages with 17a in the rotational direction, the nut 12 cannot rotate with respect to the case 4. The pin may be installed in the radial direction, or the nut may be stopped by the screw case with a fitting structure of the nut having a polygonal cross-sectional shape and the screw case without using the pin.

The inner circumference of the screw case 17 has a rear stopper 17b that faces the rear end of the output shaft 5 in the axial direction. The rear stopper 17b is a portion that stops the reverse movement of the output shaft 5 with respect to the case 4 by contact with the output shaft 5, and is a reverse end position (reverse limit position) of the stroke L of the reciprocating movement of the output shaft 5 with respect to the case 4. It is a part that determines. The rear stopper 17b is formed of a stepped surface along the radial direction. The rear stopper 17b forms a stepped portion by making the inner diameter of the front opening of the screw case 17 larger than the inner diameter of the contact portion with the nut 12, and the stepped portion is machined along the radial direction. Is formed of.

The motor case 18 shown in FIGS. 1 and 2 is coupled to the rear end side of the screw case 17. The motor case 18 supports the motor housing portion of the drive mechanism 3 on the screw case 17 so as to maintain the coaxial arrangement and the coupled state of the drive shaft 15 of the drive mechanism 3 and the first screw element 1.

The front end case 19 is coupled to the front end side of the screw case 17. The front end case 19 is composed of an inner circumference that surrounds the periphery of a protruding portion of the output shaft 5 located in front of the inner circumference of the screw case 17, and a terminal wall that extends radially from the inner circumference. The end wall of the front end case 19 is formed with a connection hole 19a that penetrates the front end case 19 in the axial direction and a front stopper 19b that faces the front end of the output shaft 5 in the axial direction.

The connection hole 19a is a female screw hole formed coaxially with the output shaft 5. The connection hole 19a is formed to facilitate the proper alignment between the case 4 of the linear actuator and the mating member 101 of the mating device 100.

The mating member 101 is supported by the housing 102 of the mating device 100 so as to be reciprocally movable within a predetermined range in the axial direction. The housing 102 has a hollow male screw shaft through which the mating member 101 is passed. By screwing the male screw shaft of the housing 102 into the connection hole 19a, the front end case 19 and the housing 102 are fastened so as to be axially abutted around the connection hole 19a. By this fastening, the axial positioning of the mating member 101 with respect to the case 4 is ensured with a certain accuracy, and the radial positioning of the mating member 101 with respect to the first screw element 1, the second screw element 2 and the output shaft 5 is also performed. It is secured at a constant coaxiality. The mating member 101 and the output shaft 5 are arranged in a non-connected state in which they can move independently in the axial direction, and do not always move integrally in the axial direction.

The front stopper 19b of the front end case 19 is a portion that stops the advance of the output shaft 5 with respect to the case 4 by contact with the output shaft 5, and is a forward end position of the stroke L of the reciprocating movement of the output shaft 5 with respect to the case 4. It is a part that determines the forward limit position). The front stopper 19b is formed of an annular flat surface along the radial direction.

The output shaft 5 can reciprocate in the axial direction with respect to the first screw element 1 and the second screw element 2, and is within a constant stroke L defined between the rear stopper 17b and the front stopper 19b of the case 4. It is arranged so that it can be reciprocated in the axial direction with respect to the case 4. The output shaft 5 is a portion serving as an output unit of the linear actuator, and the stroke L corresponds to a drive range in which the axial position of the mating member 101 can be adjusted by the linear actuator.

The output shaft 5 includes a bar 21, an intermediate spring receiver 22 that protrudes radially toward the inside of the hollow shaft 12b, a retaining ring 23 attached to the rear side of the bar 21, and a front of the hollow shaft 12b. It is composed of an engaging plate 24 protruding larger than the hollow shaft 12b at the position of, a retaining ring 25 attached to the front side of the bar 21, and a tip cap 26 overlaid on the front end of the bar 21. There is.

The bar 21 has a stepped shaft shape having shaft ends having a smaller shaft diameter than the shaft diameter of the middle portion of the axial length on the front side and the rear side. The intermediate portion of the bar 21 is radially supported by the front spring receiver 13.

The intermediate spring receiver 22 receives the front end of the first elastic element 6 and the rear end of the second elastic element 7 in the axial direction. The intermediate spring receiver 22 is composed of a washer fitted to a shaft end portion on the rear side of the bar 21. The retaining ring 23 is attached to a retaining ring groove formed at a shaft end on the rear side of the bar 21. The intermediate spring receiver 22 is restricted to a state in which it cannot move with respect to the bar 21 by the stepped surface formed between the shaft end portion and the intermediate portion on the rear side of the bar 21 and the retaining ring 23. There is. The intermediate spring receiver 22 is radially supported by the hollow shaft 12b. The outer diameter surface of the intermediate spring receiver 22 is a fitting surface that is slidably in contact with the hollow shaft 12b in the axial direction. The intermediate spring receiver 22 may be formed integrally with the bar 21.

The engaging plate 24 is made of a washer fitted to the shaft end portion on the front side of the bar 21. The retaining ring 25 is attached to a retaining ring groove formed at a shaft end on the front side of the bar 21. The engaging plate 24 is restricted to a state in which it cannot move with respect to the bar 21 by the stepped surface formed between the shaft end portion and the intermediate portion on the front side of the bar 21 and the retaining ring 25. .. The engagement plate 24 is attached so that the output shaft 5 comes into axial contact with the rear stopper 17b of the screw case 17 when the output shaft 5 moves backward to the rearward end position of the stroke L.

The tip cap 26 is press-fitted into the shaft end portion on the front side of the bar 21. The tip cap 26 has a tip portion, which is the frontmost portion of the output shaft 5, having a diameter larger than that of the connection hole 19a, and is around the connection hole 19a when the output shaft 5 advances to the forward end position of the stroke L. It is attached for axial contact with the front end case 19.

The first elastic element 6 and the second elastic element 7 are arranged between the inside of the hollow shaft 12b and the output shaft 5. The first elastic element 6 and the second elastic element 7 can generate elastic repulsive forces equal to or higher than the thrust of the second screw element 2 based on the maximum output of the drive mechanism 3, respectively. The first elastic element 6 and the second elastic element 7 each consist of an annular spring. A compression coil spring is used as the annular spring. The first elastic element 6 and the second elastic element 7 have the same specifications. The first elastic element 6 and the second elastic element 7 may each be composed of a plurality of spring members.

The first elastic element 6 is axially sandwiched between the rear end of the intermediate spring receiver 22 and the rear spring receiver 12c. The second elastic element 7 is axially sandwiched between the front end of the intermediate spring receiver 22 and the front spring receiver 13. When the second screw element 2 is moved forward or backward by the drive mechanism 3, the thrust of the second screw element 2 is transmitted from the rear spring receiver 12c or the front spring receiver 13 to the first elastic element 6 or the second elastic element 7. It is transmitted from the first elastic element 6 or the second elastic element 7 to the intermediate spring receiver 22 and further transmitted to the bar 21. Since the first elastic element 6 and the second elastic element 7 sandwich the outer diameter side of the intermediate spring receiver 22 from both the front and rear sides, the first elastic element 6 and the second elastic element are on the outer diameter side of the intermediate spring receiver 22. Even if the elastic repulsive force of 7 acts, the inclination of the intermediate spring receiver 22 is suppressed, and there is no concern that the intermediate spring receiver 22 will bite into the inside of the hollow shaft 12b.

The first elastic element 6 and the second elastic element 7 are arranged in advance between the intermediate spring receiver 22 and the corresponding rear spring receiver 12c or the front spring receiver 13 in a predetermined compression state. This is the first elastic element 6 or the second by the thrust transmitted from the rear spring receiver 12c or the front spring receiver 13 when the output shaft 5 moves forward or backward without receiving resistance from the stoppers 19b and 17b and the mating member 101. Avoiding one-layer axial compression of the elastic element 7 and advancing or reversing the output shaft 5 in conjunction with the forward or backward movement of the second screw element 2, the output shaft 5 with respect to the forward or reverse movement of the second screw element 2 This is to substantially eliminate the loss of the stroke.

Here, FIGS. 1 and 2 show a state in which the second screw element 2 is most retracted by the drive mechanism 3, and FIG. 4 shows a state in which the second screw element 2 is most retracted by the drive mechanism 3. .. The forward / backward stroke of the second screw element 2 by the drive mechanism 3 is longer than the stroke L of the output shaft 5, and the redundant portion causes the first elastic element 6 and the second elastic element 7 to be compressed by the drive mechanism 3. Based on axial length.

Specifically, when the output shaft 5 moves backward in conjunction with the reverse movement of the second screw element 2 by the drive mechanism 3, when the engaging plate 24 of the output shaft 5 in reverse contact with the rear stopper 17b of the case 4, the output is output. The reverse movement of the shaft 5 is stopped. At this time, the drive mechanism 3 cannot be stopped immediately, and the second screw element 2 is further moved backward with respect to the stopped output shaft 5. Along with this backward movement, the front end of the second elastic element 7 is rearward from the front spring receiver 13 of the second screw element 2 while the rear end of the second elastic element 7 is received by the intermediate spring receiver 22 of the output shaft 5. Since it is pushed toward, the second elastic element 7 is compressed in the axial direction to increase the elastic repulsive force, while the axial distance between the intermediate spring receiver 22 and the rear spring receiver 12c is widened, so that the first elastic element 6 is extended. Will be done. The elastic repulsive force of the second elastic element 7 is the front end of the second elastic element 7, the front spring receiver 13, and the stop while the rear end of the second elastic element 7 is received by the intermediate spring receiver 22 of the output shaft 5. Since the ring 14 and the nut 12 act in this order, the force pushing the second screw element 2 forward, that is, the force opposite to the backward thrust of the second screw element 2, is the entire second screw element 2. Will act on. When the elastic rebound force becomes equal to or higher than the thrust in the backward direction of the second screw element 2, the reverse movement of the second screw element 2 is stopped and the states shown in FIGS. 1 and 2 are obtained. In this way, in the backward progress of the output shaft 5, the backward movement of the second screw element 2 is stopped by the elastic repulsive force of the second elastic element 7, so that the female screw portion 12a and the screw shaft 8 are locked. It does not become a high friction state.

When the second screw element 2 is advanced by the drive mechanism 3 from the state of FIG. 2, the output shaft 5 is the second screw while the second elastic element 7 is extended according to the advance of the front spring receiver 13 of the second screw element 2. It will move forward in conjunction with element 2.

On the other hand, when the output shaft 5 advances in conjunction with the advance of the second screw element 2 by the drive mechanism 3, when the tip cap 26 of the advancing output shaft 5 collides with the front stopper 19b of the case 4 or the mating member 101, The advance of the output shaft 5 is stopped. At this time, the drive mechanism 3 cannot be stopped immediately, and the second screw element 2 is further advanced with respect to the stopped output shaft 5. Along with this advancement, the rear end of the first elastic element 6 moves forward from the rear spring receiver 12c of the second screw element 2 while the front end of the first elastic element 6 is received by the intermediate spring receiver 22 of the output shaft 5. Since it is pushed toward, the first elastic element 6 is compressed in the axial direction to increase the elastic repulsive force, while the axial distance between the intermediate spring receiver 22 and the front spring receiver 13 is widened, so that the second elastic element 7 is extended. Will be done. The elastic repulsive force of the first elastic element 6 is the rear end of the first elastic element 6 and the rear spring receiver of the nut 12 while the front end of the first elastic element 6 is received by the intermediate spring receiver 22 of the output shaft 5. Since it acts in the order of 12c, it acts on the entire second screw element 2 as a force pushing the second screw element 2 backward, that is, a force opposite to the forward thrust of the second screw element 2. become. When the elastic repulsive force of the first elastic element 6 becomes equal to or more than the thrust in the forward direction of the second screw element 2, the advance of the second screw element 2 is stopped, and the state shown in FIG. 4 is obtained. In this way, in the forward progress of the output shaft 5, the advance of the second screw element 2 is stopped by the elastic repulsive force of the first elastic element 6, so that the female screw portion 12a and the screw shaft 8 are locked. It does not become a high friction state.

When the second screw element 2 is moved backward by the drive mechanism 3 from the state of FIG. 4, the output shaft 5 is the second screw while the first elastic element 6 is extended according to the backward movement of the rear spring receiver 12c of the second screw element 2. It will move backward in conjunction with element 2.

As described above, this linear motion actuator has the output shaft 5 arranged so as to be reciprocally movable in the axial direction with respect to the first screw element 1, the second screw element 2 of the screw mechanism and the case 4 supporting the screw mechanism. , The first elastic element 6 arranged between the output shaft 5 and the second screw element 2 so as to transmit the thrust in the forward direction of the second screw element 2 to the output shaft 5, and the reverse of the second screw element 2. It is provided with a second elastic element 7 arranged between the output shaft 5 and the second screw element 2 so as to transmit a thrust in the direction to the output shaft 5, and the first elastic element is in a state where the output shaft 5 can be advanced. When the second screw element 2 and the output shaft 5 are interlocked in the forward direction when 6 transmits the thrust in the forward direction, and the first elastic element 6 transmits the thrust in the forward direction while the output shaft 5 cannot move forward. The first elastic element 6 applies an elastic repulsive force equal to or higher than the thrust in the forward direction to the second screw element 2 to stop the advance of the second screw element 2, and the second elastic is in a state where the output shaft 5 can move backward. When the element 7 transmits the thrust in the reverse direction, the second screw element 2 and the output shaft 5 are interlocked in the reverse direction, and the second elastic element 7 transmits the thrust in the reverse direction while the output shaft 5 cannot move backward. In this case, the second elastic element 7 applies an elastic repulsive force equal to or higher than the thrust in the reverse direction to the second screw element 2 to stop the second screw element 2 from moving backward. When the output shaft 5 does not collide with the stoppers 17b, 19b or the mating member 101 in the axial direction while the second screw element 2 is moving forward or backward by the drive mechanism 3, the thrust of the second screw element 2 is the first elastic element 6. Alternatively, it is transmitted to the output shaft 5 via the second elastic element 7 and the output shaft 5 is interlocked in the moving direction of the second screw element 2, while the drive mechanism 3 outputs the second screw element 2 while it is moving forward or backward. When the shaft 5 collides with the stoppers 17b, 19b or the mating member 101 in the axial direction, the second screw element 2 advances or moves backward with respect to the stopped output shaft 5, whereby the corresponding first elastic element 6 or When the second elastic element 7 is compressed from the second screw element 2 to increase the elastic repulsive force, and the elastic repulsive force becomes equal to or higher than the thrust in the moving direction of the second screw element 2, the elastic repulsive force causes the second screw. Since the movement of the element 2 is stopped, the first screw element 1 and the second screw element 2 do not engage with each other, and the occurrence of a locked state in the screw mechanism is prevented. As described above, in this linear actuator, the output shaft 5 as the output unit during the linear motion by the drive mechanism 3 collides with the stoppers 17b and 19b of the case 4 and the mating member 101 driven by the output shaft 5 in the axial direction. At this time, it is possible to prevent the occurrence of a locked state in the screw mechanism.

Further, in this linear motion actuator, the second thread element 2 has a hollow shaft 12b extending in the axial direction, and the first elastic element 6 and the second elastic element 7 are located between the inside of the hollow shaft 12b and the output shaft 5. Arranged, the output shaft 5 has an intermediate spring receiver 22 protruding inward of the hollow shaft 12b, and the second thread element 2 axially aligns the first elastic element 6 with the rear end of the intermediate spring receiver 22. Since it has a rear spring receiver 12c for sandwiching the rear spring receiver 12c and a front spring receiver 13 for sandwiching the second elastic element 7 with the front end of the intermediate spring receiver 22 in the axial direction, the first elastic element 6 and the second elastic element 7 are sandwiched by the second screw element 2. The second screw element 2 is held in the hollow shaft 12b of the above, and the elastic repulsive force of the first screw element 1 and the second screw element 2 is received by the common intermediate spring receiver 22 to prevent the intermediate spring receiver 22 from tilting. The first elastic element 6 and the second elastic element 7 can be expanded and contracted according to the moving direction of the output shaft 5.

Further, in this linear motion actuator, the hollow shaft 12b of the second screw element 2 is radially supported by the case 4, and the intermediate spring receiver 22 of the output shaft 5 is radially supported by the hollow shaft 12b. Since the front spring receiver 13 of the second screw element 2 supports the output shaft 5 in the radial direction, the intermediate spring receiver 22 and the front spring receiver 13 are used for the support structure of the output shaft 5 with respect to the hollow shaft 12b, and the hollow thereof is used. The shaft 12b can be supported and stabilized in the radial direction by the case 4.

Further, in this linear motion actuator, the second screw element 2 has a nut 12 screw-fitted to the first screw element 1, and the hollow shaft 12b and the rear spring receiver 12c of the second screw element 2 are integrated with the nut 12. Since the output shaft 5, the first and second elastic elements 6 and 7 are inserted into the hollow shaft 12b, the front spring receiver 13 is simply attached to the nut 12, and the output shaft 5, the first and the second are formed. (Ii) Elastic elements 6, 7 and nuts 12 can be assembled into the subsystem.

Further, since the linear actuator has a front stopper 19b and a rear stopper 17b that limit the stroke L of the output shaft 5 with respect to the case 4 to a constant value when the case 4 comes into contact with the output shaft 5, the driven side mating member 101 The stroke amount of the forward advance and the backward advance of the output shaft 5 can be accurately determined by the linear actuator alone without depending on.

In this linear actuator, the first screw element 1 is provided with a male screw and the second screw element 2 is provided with a female screw. However, the mechanism should be changed to a screw mechanism in which the first screw element has a female screw and the second screw element has a male screw. Is also possible. This change can be realized, for example, by extending a portion corresponding to the hollow shaft to the screw shaft of the first screw element and holding the output shaft, the first elastic element, and the second elastic element inside the hollow shaft. In this linear actuator, a stepped surface is formed as the rear spring receiver 12c by utilizing the radial wall thickness of the female thread portion 12a, so that the second screw element is compared with the case where the hollow shaft is extended from the screw shaft. The axial length of 2 can be suppressed. Further, although a sliding screw in which the threads of the first screw element 1 and the second screw element 2 are directly screwed to each other is adopted as the screw mechanism, a ball screw can also be adopted.

The embodiments disclosed this time should be considered to be exemplary and not restrictive in all respects. Therefore, the scope of the present invention is shown by the scope of claims rather than the above description, and it is intended that all modifications within the meaning and scope equivalent to the scope of claims are included.

1 1st screw element 2 2nd screw element 3 Drive mechanism 4 Case 5 Output shaft 6 1st elastic element 7 2nd elastic element 8 Thread shaft 12 Nut 12b Hollow shaft 12c Rear spring holder 13 Front spring holder 17b Rear stopper 19b Front stopper 22 Intermediate spring holder 24 Engagement plate 101 Mating member

Claims (5)

It supports a screw mechanism that converts the rotational force of the first screw element into an axial thrust of the second screw element, a drive mechanism that applies the rotational force to the first screw element, and the drive mechanism and the screw mechanism. In a linear actuator with a case,
An output shaft arranged so as to be reciprocally movable in the axial direction with respect to the first screw element, the second screw element, and the case.
The thrust in the forward direction of the second screw element is arranged between the output shaft and the second screw element so as to be transmitted to the output shaft, and the output shaft can be advanced in the axial direction in the forward direction. When the second screw element and the output shaft are interlocked in the forward direction when transmitting the thrust of the above, and when the thrust in the forward direction is transmitted in a state where the output shaft cannot move forward in the axial direction, the said in the forward direction. A first elastic element that applies an elastic repulsive force equal to or greater than the thrust to the second screw element to stop the advance of the second screw element.
The thrust in the reverse direction of the second screw element is arranged between the output shaft and the second screw element so as to be transmitted to the output shaft, and the output shaft can be moved backward in the axial direction in the reverse direction. When the second screw element and the output shaft are interlocked in the reverse direction when transmitting the thrust of the above, and when the thrust in the reverse direction is transmitted in a state where the output shaft cannot move backward in the axial direction, the said in the reverse direction. A linear motion actuator further comprising a second elastic element that applies an elastic repulsive force equal to or higher than a thrust to the second screw element to stop the backward movement of the second screw element. The second thread element has a hollow shaft extending in the axial direction and has a hollow shaft extending in the axial direction.
The first elastic element and the second elastic element are arranged inside the hollow shaft and between the output shaft.
The output shaft has an intermediate spring holder protruding inward of the hollow shaft.
The second screw element includes a rear spring receiver that axially sandwiches the first elastic element with the rear end of the intermediate spring receiver, and a front spring receiver that axially sandwiches the second elastic element with the front end of the intermediate spring receiver. The linear actuator according to claim 1, wherein the actuator has. The hollow shaft of the second screw element is radially supported by the case.
The intermediate spring receiver of the output shaft is radially supported by the hollow shaft.
The linear actuator according to claim 2, wherein the front spring receiver of the second screw element supports the output shaft in the radial direction. The second thread element has a nut threaded into the first thread element.
The linear actuator according to claim 2 or 3, wherein the hollow shaft of the second screw element and the rear spring receiver are integrally formed with the nut. The linear actuator according to any one of claims 1 to 4, wherein the case has a front stopper and a rear stopper that constantly limit the stroke of the output shaft with respect to the case by contact with the output shaft.

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