JP2022054918A - Direct-acting actuator - Google Patents

Abstract

To prevent occurrence of a locked state by a screw mechanism when a collision of an output shaft occurs during advance drive of the output shaft while capable of accurately determining the amount of stroke of the output shaft of a direct-acting actuator by a direct-acting actuator single body.SOLUTION: The direct-acting actuator includes: an output shaft 5 disposed so as to be capable of moving reciprocally in an axial direction relative to a screw mechanism and a case 4; and a fist elastic element 6 for transmitting thrust in an advance direction of a second screw element 2 as a direct-acting side of the screw mechanism to the output shaft 5. The first elastic element 6 interlocks the second screw element 2 and the output shaft 5 in an advance direction when the output shaft 5 transmits thrust in an advance direction in an advanceable state, gives elastic repulsive force in a retreat direction to the second screw element 2 when the output shaft 5 transmits thrust in an advance direction in an advance-disabled state, and gives elastic repulsive force in an advance direction to the output shaft 5. The case 4 has a first stopper 16b for stopping advance of the output shaft 5 and a second stopper 16c for stopping retreat of the output shaft 5.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 (a nut in a screw shaft rotation type and a screw shaft in a nut rotation type) of a screw mechanism is configured as an output shaft that outputs thrust to a mating member supported by an external structure.

Since the stroke in which the output shaft of the linear actuator moves linearly in the axial direction is limited to a certain value, the axial movement of the linear screw element as the output shaft may be restricted. As a regulating means, a stopper is provided on the case or the screw shaft so that the linearly-acting screw element as the output shaft is stopped by contact with the stopper (for example, Patent Document 1).

JP-A-2019-157952

As described above, when the linear actuator is provided with a stopper that limits the movable range of the output shaft, it is possible to accurately determine the stroke amount of the output shaft by the linear actuator alone, but as an environment for using the linear actuator, In some cases, the output shaft and the mating member are opposed to each other in the axial direction, and these are arranged in a non-connected manner. 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 linear motion screw element is advanced by the drive mechanism, the linear motion thread element that also serves as the output shaft of the linear motion actuator collides with the mating member and the screw mechanism is engaged, and then the drive mechanism reversely rotates to the rotary screw element. It may lead to a locked state in which the linear screw element cannot be moved even if a force is applied.

In view of the above background, the problem to be solved by the present invention is that the stroke amount of the output shaft of the linear actuator can be accurately determined by the linear actuator alone, but the output shaft is being driven forward by the drive mechanism. The purpose is to prevent the occurrence of a locked state in the screw mechanism when a collision of the output shaft occurs.

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, it 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 is in the forward direction in a forwardable state. When the thrust is transmitted, the second screw element and the output shaft are interlocked in the forward direction, and when the thrust in the forward direction is transmitted in a state where the output shaft cannot move forward, the second screw element is in the reverse direction. Further comprises a first elastic element that imparts an elastic repulsive force to the output shaft and an elastic repulsive force in the forward direction, and the case stops the advance of the output shaft with respect to the case by contact with the output shaft. A configuration having a first stopper for causing the output shaft to be stopped and a second stopper for stopping the backward movement of the output shaft with respect to the case by contact with the output shaft is adopted.

According to the adoption of the above configuration, the forward end position of the stroke in which the output shaft can move in the axial direction with respect to the case is determined at the contact position between the first stopper of the case and the output shaft, and the reverse end position of the stroke is determined. Is determined at the contact position between the second stopper of the case and the output shaft. Further, during the forward drive of the second screw element by the drive mechanism, the thrust in the forward direction of the second screw element is transmitted to the output shaft via the first elastic element, so that the second screw element and the output shaft are moved forward. It is possible to link them. When the output shaft collides with the mating member during the forward drive of the second screw element, the first elastic element is elastically deformed between the second screw element and the output shaft. The first elastic element applies its elastic rebound force in the backward direction with respect to the second screw element and in the forward direction with respect to the output shaft, and absorbs the impact at the time of collision. Therefore, the biting of the first screw element and the second screw element is prevented, and thereby the occurrence of the locked state in the screw mechanism is prevented.

It is preferable to further include a second elastic element arranged between the output shaft and the case so as to urge the output shaft in the backward direction as the output shaft advances. In this way, the second elastic element can be elastically deformed by utilizing the forward movement of the output shaft to urge the output shaft in the backward direction, and when the second screw element is moved backward, the elastic repulsion of the second elastic element can be used. The output shaft can be moved backward, and by extension, it is not necessary to pull the output shaft in the backward direction with the first elastic element, and the first elastic element can be fixed to only one of the second screw element and the output shaft for easy installation. can do.

Further, the case has one end portion that surrounds the periphery of the output shaft, and a bearing port that penetrates the one end portion of the case in the axial direction is formed. A linear motion guide portion that slides in the axial direction, a flange portion that is arranged inside the case and has a larger diameter than the linear motion guide portion, and a linear motion guide portion that is arranged outside the case and the linear motion guide portion. The case has an engaging portion provided with a diameter larger than that of the portion, and the first stopper of the case locks the flange portion of the output shaft at the forward end position of the stroke of the output shaft. The second stopper of the case comprises a rear wall surface formed at one end of the case, and the second stopper of the case is attached to one end of the case so as to engage the engaging portion of the output shaft at the rearward end position of the stroke of the output shaft. It is composed of a formed front wall surface, and the second elastic element is arranged between the flange portion of the output shaft and one end portion of the case, and at least one of the flange portion of the output shaft and one end portion of the case. One preferably has a recess for forming a storage space in which the second elastic element can be compressed. In this way, the output shaft is guided in the axial direction by the shaft through port at one end of the case and the linear motion guide portion of the output shaft, and the front and rear wall surfaces of the one end, the flange portion of the output shaft, and the engaging portion are formed. While the stroke amount of the output shaft can be determined by, the second elastic element can be arranged by using the flange portion and one end portion of the case.

The first elastic element may be composed of a coil spring spanned between the second screw element and the output shaft, and may be fixed to only one of the second screw element and the output shaft. In this way, the mounting structure of the first elastic element is fixed by the fitting portion between the second thread element and one of the output shafts and the first elastic element, and the second thread element and the other of the output shafts and the first elastic element are fixed. It can be as simple as abutting the first elastic element in the axial direction at the fitting portion with the element.

An electric motor can be adopted as the drive mechanism.

As described above, in the present invention, by adopting the above configuration, the stroke amount of the output shaft of the linear acting actuator can be accurately determined by the linear acting actuator alone (the first stopper and the second stopper of the case). If a collision of the output shaft occurs during the forward drive of the output shaft by the drive mechanism, a locked state is generated in the screw mechanism by the absorption action of the first elastic element between the second screw element of the screw mechanism and the output shaft. Can be prevented.

A vertical sectional view showing a linear actuator according to an embodiment of the present invention. FIG. 1 is a cross-sectional view taken along the line II-II. A vertical sectional view showing a state in which the output shaft of the linear actuator is advanced from the state shown in FIG. Enlarged view of the vicinity of the linear motion guide portion of the output shaft in FIG.

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

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 interposed between the output shaft 5 and the second screw element 2 and a second elastic element 7 interposed between the output shaft 5 and the case 4 are provided. 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.

This linear actuator is for driving the mating member 100 of another device located outside the case 4 in the axial direction. The mating member 100 is supported so as to be reciprocally movable within a predetermined range in the axial direction with respect to the external structure of the other device.

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 having a male screw portion 8. The first screw element 1 is
It has a hollow shaft shape that opens at the end opposite to the male screw portion 8. The drive mechanism 3 is connected to the first screw element 1.

The drive mechanism 3 includes an electric motor having a drive shaft 9. The drive mechanism 3 can rotate the drive shaft 9 in the forward and reverse directions. The drive shaft 9 is inserted into the hollow portion of the first screw element 1. The drive shaft 9 and the first screw element 1 are connected in a state in which a rotational force can be transmitted in any rotation direction of forward and reverse rotation and relative movement is not possible in the axial direction. A polygonal shape such as a width across flats or a D-cut, a spline, or the like is applied to the connection.

A bus bar 10 for connecting to an external power source is connected to the drive mechanism 3. An example in which the drive shaft 9 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 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 is composed of a nut screw-fitted to the male screw portion 8 of the first screw element 1. The second screw element 2 receives the female screw portion 11 corresponding to the male screw portion 8, the plurality of protrusions 12 used to prevent the rotation of the second screw element 2, and the rear side of the first elastic element 6. The peripheral groove portion 13 is integrally formed. Here, the direction in which the second screw element 2 moves axially to the right in the figure is the forward direction (forward), and the direction in which the second screw element 2 moves axially to the left in the figure is the backward direction (backward). ).

Inside the case 4, there is a rear accommodation chamber 14 that supports the drive mechanism 3 and the bus bar 10, and a front accommodation chamber 15 that accommodates the screw mechanism, the output shaft 5, the first elastic element 6, and the second elastic element 7. Is provided. Inside the rear accommodation chamber 14, an uneven portion for fixing the drive mechanism 3 and the bus bar 10 is provided. The case 4 supports the screw mechanism via a drive mechanism 3 fixed in the rear accommodation chamber 14. The case 4 has an appropriately divided structure, and the drive mechanism 3 and the like are arranged inside the case 4 so that they can be assembled.

As shown in FIGS. 1 and 2, guide grooves 15a extending straight in the axial direction are formed at a plurality of locations in the circumferential direction inside the front accommodation chamber 15. The protrusion 12 of the second screw element 2 is located in the guide groove 15a. When a rotational force is applied to the second screw element 2, the protrusion 12 engages with the guide groove 15a in the rotational direction, so that the second screw element 2 cannot rotate with respect to the case 4, but in the axial direction. You can move. A pin may be attached to the second screw element instead of the protrusion 12.

As shown in FIGS. 1 and 3, the case 4 has one end portion 16 that surrounds the circumference of the output shaft 5. One end 16 of the case 4 forms the front end of the front accommodation chamber 15. An axial through hole 16a is formed so as to penetrate one end portion 16 of the case 4 in the axial direction.

The output shaft 5 includes a linear motion guide portion 17 that slides in the axial direction with respect to the axial through port 16a of the case 4, a flange portion 18 provided with a diameter larger than that of the linear motion guide portion 17, and a linear motion guide portion. It is composed of an engaging portion 19 provided with a diameter larger than 17.

The linear motion guide portion 17 of the output shaft 5 is provided redundantly on both front and rear sides from the shaft through port 16a of the case 4. The output shaft 5 is supported coaxially with the drive shaft 9 and the screw mechanism by fitting the linear motion guide portion 17 and the shaft through port 16a.

The flange portion 18 of the output shaft 5 is arranged inside the front side accommodating chamber 15 of the case 4. The flange portion 18 is integrally formed with the linear motion guide portion 17. A step portion 18a is formed on the rear side of the flange portion 18, and a recess 18b is formed on the front side of the flange portion 18. The stepped portion 18a has a stepped round shaft shape having a small diameter on the rear side and a large diameter on the front side. The recess 18b is recessed rearward around the linear motion guide portion 17. The step portion 18a is a portion for receiving the first elastic element 6. The recess 18b is a portion for storing while receiving the second elastic element 7.

The engaging portion 19 of the output shaft 5 is arranged outside the case 4. The engaging portion 19 is composed of a retaining ring. A retaining ring groove for fitting the engaging portion 19 is formed in the external extension portion (a portion located in front of the axial through port 16a) of the linear motion guide portion 17.

The first elastic element 6 is composed of a coil spring. The first elastic element 6 is bridged between the peripheral groove portion 13 of the second screw element 2 and the step portion 18a of the output shaft 5. The rear side of the first elastic element 6 is fixed to the peripheral groove portion 13 by forced fitting of the spring winding portion to the peripheral groove portion 13. The front side of the first elastic element 6 is supported in the radial direction in a state where it can move backward and cannot move forward with respect to the output shaft 5 by fitting the spring winding portion to the step portion 18a. As a result, the first elastic element 6 is fixed only to the second screw element 2 and can be easily inserted and removed from the output shaft 5. Although an example in which the peripheral groove portion 13 is provided on the outer periphery of the second screw element 2 is shown, the peripheral groove portion is provided on the output shaft, the step portion is provided on the second screw element, and the first elastic element 6 is provided only on the output shaft. It may be fixed.

The first elastic element 6 thus arranged between the second screw element 2 and the output shaft 5 can transmit the thrust of the second screw element 2 in the forward direction to the output shaft 5. When the first elastic element 6 transmits the thrust in the forward direction of the second screw element 2 to the output shaft 5 in a state where the output shaft 5 can advance with respect to the second screw element 2, the second screw element 2 The second screw element 2 and the output shaft 5 can be interlocked in the forward direction by thrust transmission via the peripheral groove portion 13, the first elastic element 6, and the step portion 18a of the output shaft 5.

On the other hand, when the first elastic element 6 transmits the thrust in the forward direction of the second screw element 2 to the output shaft 5 in a state where the output shaft 5 cannot move forward with respect to the second screw element 2, the peripheral groove portion 13 Since the axial distance between the step portions 18a becomes narrow, the first elastic element 6 is elastically deformed so as to contract in the axial direction, and the first elastic element 6 is elastically displaced in the circumferential groove portion 13 of the second screw element 2. A repulsive force can be applied, and an elastic repulsive force in the forward direction can be applied to the step portion 18a of the output shaft 5.

The case 4 has a first stopper 16b that stops the forward movement of the output shaft 5 with respect to the case 4 by contact with the output shaft 5, and a second stopper 16c that stops the backward movement of the output shaft 5 with respect to the case 4 by contact with the output shaft 5. And have. The first stopper 16b is formed of a rear wall surface formed at a portion of one end portion 16 of the case 4 that faces the flange portion 18 of the output shaft 5 in the axial direction. The second stopper 16c is formed of a front wall surface formed at a portion of one end portion 16 of the case 4 that faces the engaging portion 19 of the output shaft 5 in the axial direction. The first stopper 16b and the second stopper 16c each have a flat surface extending in the radial direction.

As shown in FIG. 3, the first stopper 16b can stop the forward movement of the output shaft 5 by locking the flange portion 18 of the output shaft 5 at the forward end position of the stroke L of the output shaft 5. .. As shown in FIGS. 1 and 4, the second stopper 16c stops the reverse movement of the output shaft 5 by locking the engaging portion 19 of the output shaft 5 at the rearward end position of the stroke L of the output shaft 5. be able to.

The stroke L of the output shaft 5 shown in FIGS. 1 and 3 corresponds to a drive range in which the axial position of the mating member 100 can be adjusted by this linear actuator. The front end surface of the linear motion guide portion 17 is abutted against the mating member 100. The output shaft 5 outputs the thrust in the forward direction transmitted from the second screw element 2 from the linear motion guide portion 17 to the mating member 100. The mating member 100 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 second elastic element 7 is arranged between the recess 18b of the flange portion 18 of the output shaft 5 and the one end portion 16 of the case 4. The second elastic element 7 is compressed into the recess 18b to the forward end position of the stroke L of the output shaft 5 (that is, until the flange portion 18 of the output shaft 5 is locked by the first stopper 16b of the case 4). It can be stored.

The second elastic element 7 is made of an annular spring. As the annular spring, a coil spring, a disc spring, or the like can be adopted. Since the second elastic element 7 is arranged coaxially with the output shaft 5, it is fitted to the linear motion guide portion 17.

As the output shaft 5 advances with respect to one end 16 of the case 4, as shown in FIG. 3, the axial distance between the recess 18b of the output shaft 5 and the one end 16 becomes narrower, so that the second elastic element 7 is the shaft. It is elastically deformed so as to shrink in the direction. Therefore, the second elastic element 7 can urge the output shaft 5 in the reverse direction by the stored elastic rebound force.

Since the first elastic element 6 has a structure fixed only to the second screw element 2, when the second screw element 2 is reverse, the thrust in the reverse direction is transmitted from the first elastic element 6 to the output shaft 5, and the output shaft. Although the 5 cannot be pulled in the reverse direction, the output shaft 5 can be interlocked in the reverse direction according to the reverse movement of the second screw element 2 by the urging of the second elastic element 7.

Although an example is shown in which the recess 18b for forming the storage space in which the second elastic element 7 can be compressed is provided only in the flange portion 18 of the output shaft 5, the recess for forming the storage space is shown. It may be provided on at least one of the output shaft and one end of the case, and the recess may be provided only on one end of the case, or may be provided on both the flange of the output shaft and one end of the case. When the recess 18b is provided only on the output shaft 5 as shown in the illustrated example, the accuracy of the recess can be controlled only by the output shaft, which is a relatively small component, so that the manufacturing is relatively easy.

Here, FIGS. 1 and 4 show a state in which the second screw element 2 is most retracted by the drive mechanism 3, and FIG. 3 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, as shown in FIGS. 1 and 4, when the output shaft 5 is at the backward end position of the stroke L, the first elastic element 6 and the second elastic element 7 are in the longest axially oriented state, respectively. The engaging portion 19 of the output shaft 5 is maintained in a state of being locked to the second stopper 16c by the urging of the second elastic element 7. Therefore, the output shaft 5 is set at the rearward end position of the stroke L.

When the second screw element 2 is advanced by the drive mechanism 3 from the states of FIGS. 1 and 4, the thrust thereof is the peripheral groove portion 13 of the second screw element 2, the first elastic element 6, and the flange portion 18 of the output shaft 5. , The second elastic element 7, and one end 16 of the case 4 are transmitted in this order. At this time, there is resistance between one end 16 of the case 4 and the second elastic element 7, and when the mating member 100 is pushed in the forward direction, the load also becomes resistance. By advancing the second screw element 2 with a thrust exceeding the resistance at this time, the first elastic element 6 and the second elastic element 7 are gradually compressed, and the output shaft 5 is gradually moved from the shaft through port 16a of the case 4. When the mating member 100 is pushed forward, the mating member 100 is advanced. Eventually, as shown in FIG. 3, when the flange portion 18 of the output shaft 5 comes into contact with the first stopper 16b of the case 4, and the advance of the output shaft 5 is stopped by the locking of the flange portion 18 and the first stopper 16b. The output shaft 5 is defined at the forward end position of the stroke L.

When the second screw element 2 is moved backward by the drive mechanism 3 from the state of FIG. 3, the first elastic element 6 fixed to the second screw element 2 is moved backward integrally with the second screw element 2, and this reverse movement is performed. The first elastic element 6 and the second elastic element 7 gradually extend due to elastic repulsion, so that the output shaft 5 is moved backward. Eventually, as shown in FIGS. 1 and 4, the engaging portion 19 of the output shaft 5 comes into contact with the second stopper 16c of the case 4, and the reverse movement of the output shaft 5 is stopped by the locking of the engaging portion 19 and the second stopper 16c. When it is made to move, the output shaft 5 is set at the reverse end position of the stroke L.

Here, consider a case where the output shaft 5 collides with the mating member 100 in the axial direction in the middle of the advance of the stroke L of the output shaft 5. In this case, the drive mechanism 3 cannot be stopped immediately at the time of a collision, and the output shaft 5 cannot advance at a constant speed with the second screw element 2, so that the second screw element 2 can be further advanced with respect to the output shaft 5. .. At this time, since the rear end of the first elastic element 6 is pushed in the forward direction from the peripheral groove portion 13 of the second screw element 2 while the front end of the first elastic element 6 is received by the step portion 18a of the output shaft 5. , The first elastic element 6 is compressed in the forward direction. The elastic repulsive force of the first elastic element 6 is applied in the backward direction with respect to the second screw element 2 and in the forward direction with respect to the output shaft 5. Therefore, the first elastic element 6 gives an impact at the time of collision. Is absorbed. As a result, the male screw portion 8 and the female screw portion 11 do not become in a high friction state, and the first screw element 1 and the second screw element 2 are prevented from being caught, so that a locked state is prevented in the screw mechanism. ..

When the thrust of the second screw element 2 exceeds the resistance of the mating member 100 or the like after the above-mentioned collision, the first elastic element 6 and the second elastic element 7 can be compressed, so that the output shaft 5 is stroked L. It is possible to advance to the forward end position of.

When the second elastic element 7 is provided, the first elastic element 6 has a predetermined elastic repulsive force in the state of FIGS. It is also possible to give a preload to 6. This preload suppresses the amount by which the first elastic element 6 contracts in the axial direction as the second screw element 2 advances from the states of FIGS. 1 and 4, and the output shaft 5 with respect to the advance of the second screw element 2 This is to suppress stroke loss.

As described above, this linear actuator has 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 3 that applies the rotational force to the first screw element 1. A case 4 that supports the drive mechanism 3 and the screw mechanism, 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, and the second. When it is arranged between the output shaft 5 and the second screw element 2 so as to transmit the forward thrust of the screw element 2 to the output shaft 5, and the forward thrust is transmitted in a state where the output shaft 5 can move forward. When the second screw element 2 and the output shaft 5 are interlocked in the forward direction and the output shaft 5 transmits the thrust in the forward direction in a state where the output shaft 5 cannot move forward, the second screw element 2 is given an elastic repulsive force in the reverse direction. A first stopper 16b comprising a first elastic element 6 that gives an elastic repulsive force in the forward direction to the output shaft 5, and the case 4 stops the advance of the output shaft 5 with respect to the case 4 by contact with the output shaft 5. By having the second stopper 16c that stops the reverse movement of the output shaft 5 with respect to the case 4 by contact with the output shaft 5, the forward end position of the stroke L of the output shaft 5 is the contact between the first stopper 16b and the output shaft 5. The position is determined, and the reverse end position of the stroke L is determined at the contact position between the second stopper 16c and the output shaft 5. Further, during the forward drive of the second screw element 2 by the drive mechanism 3, the thrust in the forward direction of the second screw element 2 is transmitted to the output shaft 5 via the first elastic element 6, so that the second screw element 2 and the second screw element 2 The output shaft 5 is interlocked in the forward direction. At this time, when the output shaft 5 collides with the mating member 100, the first elastic element 6 elastically deformed between the second screw element 2 and the output shaft 5 exerts its elastic repulsive force with respect to the second screw element 2. It is applied in the reverse direction, applied in the forward direction with respect to the output shaft 5, and absorbs the impact at the time of collision. Therefore, the first screw element 1 and the second screw element 2 are prevented from being bitten, thereby preventing the occurrence of a locked state in the screw mechanism.

Therefore, in this linear actuator, although the stroke amount L of the output shaft 5 can be accurately determined by the linear actuator alone, a collision of the output shaft 5 occurs during the forward drive of the output shaft 5 by the drive mechanism 3. In this case, it is possible to prevent the occurrence of a locked state in the screw mechanism by the absorption action of the first elastic element 6 between the second screw element 2 of the screw mechanism and the output shaft 5.

Further, since this linear motion actuator further includes a second elastic element 7 arranged between the output shaft 5 and the case 4 so as to urge the output shaft 5 in the reverse direction as the output shaft 5 moves forward. , The second elastic element 7 can be elastically deformed between the output shaft 5 and the case 4 by utilizing the forward movement of the output shaft 5 to urge the output shaft 5 in the backward direction, and when the second screw element 2 is moved backward. The output shaft 5 can be moved backward by the elastic repulsion of the second elastic element 7, and it is not necessary to pull the output shaft 5 in the backward direction by the first elastic element 6, and the first elastic element 6 is a second screw element. It can be easily attached by fixing it to only one of 2 and the output shaft 5.

Further, in this linear motion actuator, the case 4 has one end portion 16 that surrounds the periphery of the output shaft 5, and an axial through port 16a that penetrates the one end portion 16 of the case 4 in the axial direction is formed, and the output shaft 5 is formed. A linear motion guide portion 17 that slides in the axial direction with respect to the axial through port 16a, a flange portion 18 that is arranged inside the case 4 and has a diameter larger than that of the linear motion guide portion 17, and a case 4. Case 4 having an engaging portion 19 arranged externally and having a diameter larger than that of the linear motion guide portion 17, and the first stopper 16b locking the flange portion 18 at the forward end position of the stroke L. The rear wall surface of the one end portion 16 is formed, the second stopper 16c is formed of the front wall surface of the one end portion 16 of the case 4 for engaging the engaging portion 19 at the rearward end position of the stroke L, and the second elastic element 7 is the flange portion. A recess 18b arranged between the 18 and one end 16 of the case 4 for forming a storage space in which at least one of the flange 18 and one end 16 of the case 4 can compress the second elastic element 7. The output shaft 5 is guided in the axial direction by the shaft through port 16a of the case 4 and the linear motion guide portion 17 of the output shaft 5, and both the front and rear wall surfaces of the one end portion 16 of the case 4 and the flange portion of the output shaft 5 are provided. The second elastic element 7 can be arranged by using the flange portion 18 and the one end portion 16 of the case 4 while the stroke amount L of the output shaft 5 can be determined by the engaging portion 19.

Further, in this linear motion actuator, the first elastic element 6 is composed of a coil spring spanned between the second screw element 2 and the output shaft 5, and is fixed to only one of the second screw element 2 and the output shaft 5. Therefore, it is as simple as fixing one of them with the fitting portion of the first elastic element 6 and abutting the first elastic element 6 in the axial direction at the fitting portion of the other side and the first elastic element 6. It can be a mounting structure of one elastic element 6.

In the above-described embodiment, the first screw element 1 is provided with the male screw portion 8 and the second screw element 2 is provided with the female screw portion 11, but the first screw element is provided with the female screw portion and the second screw element is provided with the male screw portion. It is also possible to change to a screw mechanism.

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.

When the second elastic element is not adopted, the first elastic element may be fixed to the output shaft, and the thrust in the backward direction of the second screw element may be transmitted from the first elastic element to the output shaft. Although the first elastic element 6 and the second elastic element 7 are each composed of a single spring, each may be composed of a plurality of spring members.

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 13 Circumferential groove 16 One end 16a Shaft through hole 16b First stopper 16c Second stopper 17 Linear guide Part 18 Flange part 18a Step part 18b Recess 19 Engagement part

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 transmit the thrust in the forward direction to the output shaft, and the thrust in the forward direction is provided so that the output shaft can move forward. When the second screw element and the output shaft are interlocked in the forward direction when transmitting, and when the thrust in the forward direction is transmitted in a state where the output shaft cannot move forward, the elasticity in the reverse direction is transmitted to the second screw element. Further provided with a first elastic element that gives a repulsive force and gives an elastic repulsive force in the forward direction to the output shaft.
The case includes a first stopper that stops the forward movement of the output shaft with respect to the case by contact with the output shaft, and a second stopper that stops the backward movement of the output shaft with respect to the case by contact with the output shaft. A linear actuator characterized by having. The linear actuator according to claim 1, further comprising a second elastic element arranged between the output shaft and the case so as to urge the output shaft in the backward direction as the output shaft advances. The case has one end portion that surrounds the periphery of the output shaft, and an axial through port is formed through the one end portion of the case in the axial direction.
The output shaft includes a linear motion guide portion that slides in the axial direction with respect to the axial passage port of the case, and a flange portion that is arranged inside the case and has a diameter larger than that of the linear motion guide portion. It has an engaging portion that is arranged outside the case and is provided with a diameter larger than that of the linear motion guide portion.
The first stopper of the case is composed of a rear wall surface formed at one end of the case so as to lock the flange portion of the output shaft at the forward end position of the stroke of the output shaft, and is the second of the case. The stopper is composed of a front wall surface formed at one end of the case so as to engage the engaging portion of the output shaft at the rearward end position of the stroke of the output shaft.
The second elastic element is arranged between the flange portion of the output shaft and one end portion of the case.
The linear actuator according to claim 2, wherein at least one of the flange portion of the output shaft and one end portion of the case has a recess for forming a storage space in which the second elastic element can be compressed. The first elastic element is composed of a coil spring spanned between the second screw element and the output shaft, and is fixed to only one of the second screw element and the output shaft. The linear actuator according to any one of the following items. The linear actuator according to any one of claims 1 to 4, wherein the drive mechanism comprises an electric motor.

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