JP7548091B2 - Linear motion devices and actuators - Google Patents

Description

The present invention relates to a linear motion device and an actuator.

As an actuator that obtains axial force from input torque, there is a technology that uses a ball screw to convert rotational motion into linear motion. In this actuator, the rotational motion of the screw shaft is converted into linear motion of the nut, and the axial force is extracted from the output shaft connected to the nut. Patent Document 1 discloses a technology that uses a transmission element to connect the nut and output shaft of the actuator.

JP 2012-42050 A

In an actuator that uses a transmission element to connect a nut and an output shaft, if the power transmission system becomes stuck, it is desirable to release the connection between the actuator and the output shaft to avoid the effects of the sticking.
SUMMARY OF THE PRESENT DISCLOSURE In view of the above, an object of the present invention is to provide a linear motion device and an actuator that are capable of releasing the connection with the output shaft using a cotter.

In order to solve the above problems, a linear motion device according to one aspect of the present invention includes a screw shaft, a nut that converts the rotational motion of the screw shaft into linear motion in the axial direction of the screw shaft, a coupling member that couples an output shaft that outputs an axial force based on the linear motion converted by the nut to the nut, and a release member that can release the connection between the nut and the output shaft.

As a result, even if the movement of the nut is restricted due to a stuck state or a loaded state of the power transmission system, the movement of the output shaft can be prevented from being restricted via the nut, and the effects of a stuck state or a high load state of the power transmission system can be avoided.

Furthermore, according to a linear motion device according to one aspect of the present invention, the release member can reversibly release the connection between the nut and the output shaft.

As a result, even if the movement of the nut is restricted due to a stuck state or a loaded state of the power transmission system, the movement of the output shaft can be prevented from being restricted via the nut without destroying the linear motion device. This makes it possible to prevent the movement of the output destination of the axial force from the output shaft from being restricted via the output shaft, and makes it possible to avoid the effects of a stuck state or a high load state of the power transmission system.

In addition, according to a linear motion device according to one aspect of the present invention, the coupling member can be inserted into and removed from the nut by passing through the output shaft in a direction perpendicular to the axial direction of the screw shaft.

This allows the nut and output shaft to be connected or disconnected based on the insertion and removal of the connecting member, eliminating the need to use complex configurations such as a gripping mechanism or clutch mechanism to disconnect the nut and output shaft. This makes it possible to connect the nut and output shaft while preventing the actuator from becoming larger and more expensive.

Furthermore, according to a linear motion device according to one aspect of the present invention, the release member is capable of restoring the connection after releasing the connection.

As a result, after the connection between the nut and the output shaft is released, the linear motion device can be operated normally without replacing the connecting member and the nut. This makes it possible to release the connection between the nut and the output shaft while suppressing a decrease in the maintainability of the actuator.

In addition, according to a linear motion device according to one aspect of the present invention, the connecting member is a cotter or a key.

This makes it possible to connect or disconnect the nut and output shaft by inserting or removing the connecting member.

In addition, according to a linear motion device of one aspect of the present invention, the cotter is arranged relative to the nut and the output shaft so as to have a circumferential gap in the circumferential direction of the output shaft, and the key is arranged relative to the nut and the output shaft so as to have an axial gap in the axial direction of the output shaft.

As a result, even if twisting occurs on the output shaft, the effect can be absorbed by the circumferential and axial gaps, making it difficult for twisting to occur on the ball screw. This makes it possible to extend the life of the actuator that uses the linear motion device, even if misalignment occurs during assembly of the linear motion device and the output shaft.

In addition, according to a linear motion device according to one aspect of the present invention, the release member is an electromagnet that can pull the coupling member out of the nut.

As a result, by controlling the current flowing through the electromagnet, it is possible to connect or disconnect the nut from the output shaft. This eliminates the need to use a complex configuration such as a gripping mechanism or clutch mechanism to disconnect the nut from the output shaft, making it possible to suppress the complexity of the actuator configuration.

In addition, the linear motion device according to one aspect of the present invention further includes an elastic member provided between the electromagnet and the connecting member, which holds down the connecting member at the connecting position between the nut and the output shaft.

This allows the coupling member to be pulled out of the nut while preventing the coupling member from coming loose when the nut and output shaft are coupled, and allows the coupling member to be reversibly released from the nut and output shaft.

In addition, according to a linear motion device according to one aspect of the present invention, the electromagnet has a winding and an iron core around which the winding is wound, and the iron core is extended into the elastic member to a position where it does not interfere with the removal of the connecting member from the nut.

This allows the attractive force of the electromagnet to be increased without increasing the size of the linear motion device, improving the efficiency of releasing the connection between the nut and the output shaft.

In addition, according to a linear motion device according to one aspect of the present invention, the release member includes a motor having a rotating shaft on which a male thread is formed, the rotating shaft is arranged along a direction perpendicular to the axial direction of the screw shaft, and the coupling member includes an opening on which a female thread capable of engaging with the male thread is formed.

This allows the coupling member to move linearly in the axial direction of the rotating shaft based on the rotational motion of the motor, and by switching the rotational direction of the motor, the nut and output shaft can be coupled or released from the coupling between the nut and output shaft. This makes it possible to release the coupling between the nut and output shaft while preventing the actuator configuration from becoming too complicated.

In addition, according to the linear motion device according to one aspect of the present invention, the release member is capable of pulling the connecting member out of the nut.

As a result, by operating the actuator, the nut and the output shaft can be connected or disconnected, and the connection between the nut and the output shaft can be disconnected.

In addition, according to one aspect of the present invention, a linear motion device includes a screw shaft, a nut that converts the rotational motion of the screw shaft into linear motion in the axial direction of the screw shaft, a coupling member that couples an output shaft to the nut that outputs an axial force based on the linear motion converted by the nut, and a pressing part that can reversibly press the coupling member in a direction in which the coupling member is accommodated in the recess of the nut, and the shapes of the coupling member and the recess are set so that the coupling member can move in the axial direction of the screw shaft from a state where it is accommodated in the recess of the nut based on a force applied in the axial direction of the screw shaft and can come out of the recess of the nut.

As a result, by pressing the connecting member, it is possible to connect the nut and the output shaft, and by applying an axial force to the output shaft depending on the stuck state or load state of the power transmission system, the connecting member can be moved axially and removed from the recess. Therefore, it is possible to release the connection between the nut and the output shaft without using a complex configuration such as a gripping mechanism or clutch mechanism, and it is possible to avoid the effects of sticking of the power transmission system while suppressing the complexity of the actuator configuration.

In addition, according to a linear motion device according to one aspect of the present invention, the connecting member has a shape that narrows toward the tip, and the recess has a shape that corresponds to the shape of the connecting member.

This allows the coupling member to be forced in the radial direction of the output shaft when force is applied to the coupling member in the axial direction of the output shaft. As a result, the coupling member can be moved out of the recess as the coupling member moves in the axial direction of the output shaft, and the coupling between the nut and the output shaft can be released while preventing the actuator configuration from becoming too complicated.

In addition, according to one aspect of the linear motion device of the present invention, the tip of the connecting member is wedge-shaped.

This makes it possible to apply force to the connecting member in the radial direction of the output shaft when force is applied to the connecting member in the axial direction of the output shaft, while also preventing the configuration of the connecting member from becoming too complicated. This makes it possible to release the connection between the nut and the output shaft while preventing the configuration of the actuator from becoming too complicated.

In addition, according to one aspect of the linear motion device of the present invention, the shapes of the connecting member and the recess are rotationally symmetric about the radial axis of the output shaft.

This makes it possible to apply force to the connecting member in the radial direction of the output shaft when force is applied to the connecting member in the axial direction of the output shaft, and simplifies the machining of the connecting member.

In addition, according to a linear motion device according to one aspect of the present invention, the pressing portion includes a pressure medium that can be sealed in a space provided on the rear end side of the connecting member, and a release portion that releases the pressure medium sealed in the space.

By introducing a pressure medium into the space provided on the rear end side of the connecting member, the connecting member can be pressed, and the nut and the output shaft can be connected, and by releasing the pressure medium from the space, the connecting member can be moved in the axial direction of the output shaft, and the connecting member can be moved in the axial direction depending on the stuck state or load state of the power transmission system, and the connecting member can be removed from the recess. Therefore, the connection between the nut and the output shaft can be released without using a complex configuration such as a gripping mechanism or clutch mechanism, and the effects of sticking of the power transmission system can be avoided while suppressing the complexity of the actuator configuration.

In addition, according to a linear motion device according to one aspect of the present invention, the pressing portion is a spring provided on the rear end side of the connecting member.

By providing a compressed spring on the rear end side of the connecting member, it is possible to press the connecting member, connecting the nut and the output shaft, and by moving the connecting member in the axial direction of the output shaft, the spring is further compressed and the connecting member can be removed from the recess. Therefore, it is possible to release the connection between the nut and the output shaft without providing a detector that detects the stuck state of the power transmission system, a power unit that supplies power from the outside, and a control unit that controls the power based on the detection results of the stuck state, etc., and it is possible to avoid the effects of sticking of the power transmission system while suppressing the complication of the actuator configuration.

In addition, according to a linear motion device according to one aspect of the present invention, the connecting member is arranged with respect to at least one of the nut and the output shaft so that there is a gap in the radial direction of the output shaft.

As a result, even if the output shaft is subjected to twisting, the action can be absorbed by the gap between the connecting member, making it difficult for twisting to act on the ball screw. Therefore, even if misalignment occurs during assembly of the linear motion device and the output shaft, it is possible to extend the life of the actuator that uses the linear motion device.

An actuator according to one aspect of the present invention includes any one of the linear motion devices described above and the output shaft.

As a result, even if the power transmission system becomes stuck, it is possible to prevent the operation of the output destination of the axial force from the output shaft from being restricted via the output shaft without destroying the linear motion device, and to avoid the effects of a stuck or high load state of the power transmission system.

In addition, according to an actuator according to one aspect of the present invention, the output shaft includes a storage section that stores the release member in a position where the connection can be released.

This allows the release member to be stored inside the output shaft, preventing it from protruding from the output shaft. This makes it possible to configure an actuator that can release the connection between the nut and the output shaft while preventing increased difficulty in handling and installing the actuator.

In addition, according to an actuator according to one aspect of the present invention, the storage section is an opening provided in the output shaft.

This makes it possible to store the release member inside the output shaft while preventing the output shaft from becoming too complicated in configuration, and also makes it easier to attach the release member to the actuator.

According to one aspect of the present invention, it is possible to provide a linear motion device and actuator that can release the connection with the output shaft using a cotter.

FIG. 1 is a perspective view showing the configuration of an actuator according to a first embodiment. FIG. 2(a) is an oblique view showing the connected state between the nut and the output shaft of the actuator in the first embodiment, FIG. 2(b) is a cross-sectional view showing the connected state between the nut and the output shaft, FIG. 2(c) is an oblique view showing the released state between the nut and the output shaft, and FIG. 2(d) is a cross-sectional view showing the released state between the nut and the output shaft. FIG. 3(a) is a cross-sectional view showing a connected state between a nut and an output shaft of an actuator according to a second embodiment, and FIG. 3(b) is a cross-sectional view showing a released state between the nut and the output shaft. FIG. 4 is a cross-sectional view showing an example of the configuration of an iron core of an electromagnet of an actuator according to the third embodiment. FIG. 5 is a perspective view showing the configuration of an actuator according to the fourth embodiment. FIG. 6(a) is a cross-sectional view showing the configuration of the actuator when the nut and the output shaft are connected in the fifth embodiment, and FIG. 6(b) is a cross-sectional view showing an enlarged view of the cotter portion of FIG. 6(a). FIG. 7(a) is a cross-sectional view showing the configuration of the actuator when the connection between the nut and the output shaft in the fifth embodiment is released, and FIG. 7(b) is a cross-sectional view showing an enlarged view of the cotter portion in FIG. 7(a). FIG. 8(a) is a cross-sectional view showing the configuration of the actuator when the nut and the output shaft are connected in the sixth embodiment, and FIG. 8(b) is a cross-sectional view showing an enlarged view of the cotter portion of FIG. 8(a). FIG. 9(a) is a cross-sectional view showing the configuration of the actuator when the connection between the nut and the output shaft in the sixth embodiment is released, and FIG. 9(b) is a cross-sectional view showing an enlarged view of the cotter portion in FIG. 9(a). Figure 10(a) is a cross-sectional view showing the configuration of the actuator when the nut and output shaft are connected in the seventh embodiment, and Figures 10(b) to 10(d) are cross-sectional views showing enlarged views of the movement of the cotter when the connection between the nut and output shaft in Figure 10(a) is released. FIG. 11(a) is a perspective view showing one example of the configuration of the cotter in FIG. 10(a), and FIG. 11(b) is a perspective view showing another example of the configuration of the cotter in FIG. 10(a). FIG. 12 is a side view showing an example of a gap between the cotter and the nut according to the eighth embodiment. FIG. 13 is a side view showing an example of a gap between the cotter and the output shaft according to the ninth embodiment. Figure 14(a) is a cross-sectional view showing the configuration of the actuator when the nut and output shaft are connected in the 10th embodiment, and Figures 14(b) to 14(d) are cross-sectional views showing enlarged views of the movement of the cotter when the connection between the nut and output shaft in Figure 14(a) is released.

Below, the embodiments of the present invention will be described in detail with reference to the attached drawings. Note that the following embodiments do not limit the present invention, and not all of the combinations of features described in the embodiments are necessarily essential to the configuration of the present invention. The configuration of the embodiments may be modified or changed as appropriate depending on the specifications of the device to which the present invention is applied and various conditions (conditions of use, environment of use, etc.). The technical scope of the present invention is determined by the claims, and is not limited by the individual embodiments below. Also, the drawings used in the following description may differ in scale and shape from the actual structure in order to make each configuration easier to understand.

FIG. 1 is a perspective view showing the configuration of an actuator according to a first embodiment.
In FIG. 1, the actuator EA1 outputs an axial force in the axial direction based on a rotational motion. The actuator EA1 includes a screw shaft 1, a nut 2, an output shaft 3, and a cotter 4. The screw shaft 1 and the nut 2 can be used as a ball screw constituting a linear motion device. The screw shaft 1 performs a rotational motion based on a rotational force generated from a driving source such as a motor. The nut 2 converts the rotational motion of the screw shaft 1 into a linear motion in the axial direction of the screw shaft 1. The output shaft 3 outputs an axial force based on the linear motion converted by the nut 2. The shape of the output shaft 3 is, for example, cylindrical. In this case, the inner peripheral surface of the output shaft 3 can be configured to follow the outer peripheral surface of the nut 2. The nut 2 can be provided between the outer peripheral surface of the screw shaft 1 and the inner peripheral surface of the output shaft 3.

The cotter 4 is used as a connecting member that connects the output shaft 3 to the nut 2. The cotter 4 can be inserted and removed from the nut 2, penetrating the output shaft 3 in a direction perpendicular to the axial direction of the screw shaft 1. When the cotter 4 is inserted into the nut 2, it is supported by the nut 2 in a state where it protrudes toward the output shaft 3. The cotter 4 can be used as an axial force transmission member from the nut 2 to the output shaft 3.

The screw shaft 1 has a screw groove 1m. The screw groove 1m is provided in a spiral shape on the outer peripheral surface of the screw shaft 1. The nut 2 has a screw groove 2m. The screw groove 2m is provided in a spiral shape on the inner peripheral surface of the nut 2 so as to face the screw groove 1m. At this time, the screw grooves 1m and 2m form a spiral ball rolling path between the screw shaft 1 and the nut 2.

The materials of the screw shaft 1, nut 2, and output shaft 3 are not particularly limited as long as they are rigid, and may be, for example, metals such as iron or aluminum alloys, or nonmetals such as ceramics. The material of the cotter 4 is a magnetic material such as iron or ferrite. The cross-sectional shape of each screw groove 1m, 2m may be, for example, a circular arc or a Gothic arc.

One end of the screw shaft 1 is connected to a gear 13. The gear 13 is rotatably supported by a housing 12 via a bearing 11 and is fixed in the axial direction by a gear fixing nut 14. The bearing 11 is, for example, an angular ball bearing.

The rotational force generated by a driving source such as a motor is input to the screw shaft 1 via the gear 13, causing the screw shaft 1 to rotate. When the screw shaft 1 rotates, the balls between the screw shaft 1 and the nut 2 circulate in the ball rolling path via a ball circulator (not shown), while the nut 2 moves linearly. The axial force based on the linear motion of the nut 2 is then transmitted to the output shaft 3 via the cotter 4, and is output via the output shaft 3.

The actuator EA1 can be used, for example, in a vibration control device for a vehicle. For example, in the case of a vibration control device for a railway vehicle, the actuator EA1 can be installed between the car body and the bogie. Then, by outputting an axial force in the opposite phase to the vibration of the car body from the output shaft 3, the vibration of the car body can be reduced.

The actuator EA1 can reversibly release the connection between the nut 2 and the output shaft 3. Here, the actuator EA1 has an electromagnet 5 as a release member that can reversibly release the connection between the nut 2 and the output shaft 3. The electromagnet 5 can pull the cotter 4 out of the nut 2. The electromagnet 5 has an iron core 5A and a winding 5B. The winding 5B is wound around the iron core 5A. The material of the iron core 5A is preferably a material with high magnetic permeability, and for example, pure iron, silicon steel, or ferrite can be used.

The actuator EA1 further includes a spring 6 and a bearing 7. The spring 6 is used as an elastic member that holds down the cotter 4 at the joining position between the nut 2 and the output shaft 3. The spring 6 is provided between the electromagnet 5 and the cotter 4. The spring 6 is not particularly limited as long as it is an elastic member that holds down the cotter 4, such as a spring, a leaf spring, or a disc spring. Rubber may be used instead of the spring 6. The electromagnet 5 and the spring 6 can be stored in the output shaft 3. Here, in order to make it possible to store the electromagnet 5 and the spring 6 in the output shaft 3, the thickness of the output shaft 3 at the storage position of the electromagnet 5 and the spring 6 may be made thick. Also, the distance between the electromagnet 5 and the cotter 4 can be set so that the cotter 4 can be pulled out from the nut 2 when the spring 6 is compressed.

The bearing 7 supports the output shaft 3 so that it can move linearly relative to the housing that contains the output shaft 3. The bearing 7 is, for example, a sliding bearing. The bearing 7 can be fixed to the outer circumferential surface of the output shaft 3. In this case, the bearing 7 may be arranged on the electromagnet 5. The material of the bearing 7 is, for example, resin. By arranging the bearing 7 on the electromagnet 5, the electromagnet 5 and the spring 6 can be prevented from coming off the output shaft 3.

Here, the movement of the nut 2 is restricted according to the stuck state or the loaded state of the power transmission system, such as the motor, gears, or linear motion parts. At this time, when a stuck state or a high load state of the power transmission system is detected, the cotter 4 can be attracted to the electromagnet 5 to a position where the cotter 4 is pulled out from the nut 2 by passing a current through the electromagnet 5, while compressing the spring 6. When the cotter 4 is pulled out from the nut 2, the axial force based on the linear motion of the nut 2 cannot be transmitted to the output shaft 3 via the cotter 4, and the movement of the output shaft 3 can be prevented from being restricted via the nut 2. Therefore, the operation of the output destination of the axial force from the output shaft 3 can be prevented from being restricted via the output shaft 3, and the influence of a stuck state or a high load state of the power transmission system can be avoided.

For example, suppose that actuator EA1 is installed between the car body and bogie of a railway vehicle. If the power transmission system becomes stuck, actuator EA1 will always be in a tensioned state, and vibrations of the bogie will be transmitted directly to the car body via actuator EA1, reducing the ride comfort of the railway vehicle. At this time, a current is passed through electromagnet 5 and the cotter 4 is pulled out from nut 2, thereby releasing the connection between nut 2 and output shaft 3. As a result, even if the power transmission system becomes stuck, it is possible to prevent vibrations of the bogie from being transmitted directly to the car body via actuator EA1, improving the ride comfort of the railway vehicle.

In addition, the nut 2 and the output shaft 3 can be released from the connection by pulling the cotter 4 out of the nut 2 based on the electromagnetic force of the electromagnet 5. This eliminates the need to destroy the nut 2 or the cotter 4 in order to release the connection between the nut 2 and the output shaft 3, and reduces the deterioration of the maintainability of the actuator EA1.

In addition, the connection between the nut 2 and the output shaft 3 can be restored by cutting off the current flowing through the electromagnet 5. Therefore, even if the connection between the nut 2 and the output shaft 3 is released, the actuator EA1 can be restored to normal operation without replacing the nut 2 and the cotter 4.

Furthermore, by using the cotter 4 to connect the nut 2 to the output shaft 3, the nut 2 can be connected to the output shaft 3 or released from the connection between the nut 2 and the output shaft 3 by inserting and removing the cotter 4, and there is no need to use a complex configuration such as a gripping mechanism or clutch mechanism to release the connection between the nut 2 and the output shaft 3. Therefore, the nut 2 can be connected to the output shaft 3 while preventing the actuator EA1 from becoming larger and more expensive.

The operation of releasing the connection between the nut 2 and the output shaft 3 using the electromagnet 5 will now be described in detail.
Figure 2(a) is an oblique view showing the connected state between the nut and the output shaft of the actuator in the first embodiment, Figure 2(b) is a cross-sectional view showing the connected state between the nut and the output shaft cut in the axial direction, Figure 2(c) is an oblique view showing the released state between the nut and the output shaft, and Figure 2(d) is a cross-sectional view showing the released state between the nut and the output shaft cut in the axial direction.

In Figures 2(a) and 2(b), the nut 2 has a recess 2A. The recess 2A accommodates the tip of the cotter 4. The planar shape of the recess 2A can correspond to the planar shape of the tip of the cotter 4. The recess 2A can be provided on the outer peripheral surface of the nut 2.

The output shaft 3 has a through hole 3A and openings 3B to 3D. The through hole 3A and openings 3B to 3D can be provided on the side of the output shaft 3. In this case, the tip end of the cotter 4 can be accommodated in the recess 2A via the through hole 3A and openings 3B to 3D. The through hole 3A accommodates the rear end of the cotter 4. The opening 3B accommodates the spring 6 between the electromagnet 5 and the cotter 4. The opening 3C accommodates the electromagnet 5 at a distance from the cotter 4 in the radial direction of the output shaft 3. The opening 3D accommodates the bearing 7 so as to cover the electromagnet 5.

In order to support the electromagnet 5 in the output shaft 3 with a gap between it and the cotter 4, a step may be provided between the openings 3B and 3C. Then, by placing the electromagnet 5 housed in the case 8 in the step between the openings 3B and 3C, the electromagnet 5 can be supported in the output shaft 3 with a gap between it and the cotter 4.

When the nut 2 and output shaft 3 are connected, the rear end of the cotter 4 is fitted into the recess 2A with the rear end protruding into the through hole 3A. The cotter 4 is pressed by the spring 6 so that it does not slip out of the recess 2A. At this time, the spring 6 is maintained in a partially compressed state between the cotter 4 and the electromagnet 5. In other words, when the nut 2 and output shaft 3 are connected, the spring 6 is maintained in a state in which it can further compress while pressing the cotter 4.

When the nut 2 and output shaft 3 are connected, the power transmission system is stuck and the movement of the nut 2 is restricted. At this time, when the stuck state of the power transmission system is detected and a current is passed through the electromagnet 5, the cotter 4 is attracted to the electromagnet 5 while the spring 6 is compressed. Then, as shown in Figures 2(c) and 2(d), when the cotter 4 is pulled out of the nut 2 and the tip of the cotter 4 reaches the through hole 3A, the output shaft 3 is released from the constraint of the nut 2.

Here, by providing an opening 3C in the output shaft 3 as a housing for housing the electromagnet 5, it is possible to house the electromagnet 5 within the output shaft 3 while preventing the configuration of the output shaft 3 from becoming too complicated, and it is also possible to easily attach the electromagnet 5 to the actuator EA1.

In addition, by providing a step between the openings 3B and 3C, the spring 6 is accommodated in the opening 3B, and then the electromagnet 5 is placed in the step between the openings 3B and 3C, making it possible to support the electromagnet 5 in the output shaft 3 with a gap between it and the cotter 4. This makes it possible to reversibly release the connection between the nut 2 and the output shaft 3 while preventing the configuration of the output shaft 3 from becoming complicated, and also makes it easier to attach the spring 6 and the electromagnet 5 to the actuator EA1.

FIG. 3(a) is a cross-sectional view taken along the axial direction to show the connected state between the nut and the output shaft of the actuator according to the second embodiment, and FIG. 3(b) is a cross-sectional view taken along the axial direction to show the released state between the nut and the output shaft.
3(a) and 3(b), this actuator has an electromagnet 5' instead of the electromagnet 5 of FIG. 2(b) and 2(d). The electromagnet 5' has an iron core 5A' instead of the iron core 5A of FIG. 2(b) and 2(d). The iron core 5A' protrudes from the winding 5B toward the cotter 4 and is extended into the spring 6 to a position where it does not interfere with the removal of the cotter 4 from the nut 2.

This allows the attractive force of the electromagnet 5' to be increased without increasing the size of the actuator, improving the efficiency of releasing the connection between the nut 2 and the output shaft 3.

FIG. 4 is a cross-sectional view showing an example of the configuration of an iron core of an electromagnet of an actuator according to a third embodiment, cut in the circumferential direction.
In Fig. 4, this actuator has an electromagnet 5" instead of the electromagnet 5 in Figs. 2(b) and 2(d). The electromagnet 5" has an iron core 5A" instead of the iron core 5A in Figs. 2(b) and 2(d). In the circumferential direction of the output shaft 3, the outer circumferential surface of the iron core 5A" is configured to follow the inner circumferential surface of the bearing 7. For example, the curvature of the outer circumferential surface of the iron core 5A" can be made equal to the curvature of the inner circumferential surface of the bearing 7.

This makes it possible to increase the contact area between the iron core 5A'' and the bearing 7 without increasing the size of the actuator, and prevents the electromagnet 5'' from coming loose in the circumferential direction when the bearing 7 is attached.

FIG. 5 is a perspective view showing the configuration of an actuator according to the fourth embodiment.
5, this actuator EA2 includes a nut 2' and an output shaft 3' instead of the nut 2 and the output shaft 3 in Fig. 1. Also, this actuator EA2 includes a key 4', an electromagnet 5' and a spring 6' in addition to the actuator EA1 in Fig. 1.

The nut 2' converts the rotational motion of the screw shaft 1 into linear motion in the axial direction of the screw shaft 1. The output shaft 3' outputs an axial force based on the linear motion converted by the nut 2'. Here, not only a cotter 4 but also a key 4' is used to connect the nut 2' and the output shaft 3'. The key 4' can be arranged at a distance from the cotter 4 in the circumferential direction of the output shaft 3'.

The key 4' is used as a connecting member that connects the output shaft 3 to the nut 2. The key 4' can be inserted into and removed from the nut 2, penetrating the output shaft 3 in a direction perpendicular to the axial direction of the screw shaft 1. When the key 4' is inserted into the nut 2, it is supported by the nut 2 in a state where it protrudes toward the output shaft 3. The key 4' is made of a magnetic material such as iron or ferrite. The key 4' can be used as a member that prevents the output shaft 3 from rotating relative to the nut 2.

At this time, the longitudinal direction of the cotter 4 is set in the circumferential direction of the output shaft 3, while the longitudinal direction of the key 4' can be set in the axial direction of the output shaft 3. Also, the recess of the nut 2' in which the tip of the cotter 4 is housed is configured to receive the axial force applied to the cotter 4, while the recess of the nut 2' in which the tip of the key 4' is housed is configured to receive the rotational force applied to the key 4'. For example, the recess of the nut 2' in which the tip of the cotter 4 is housed may be a groove provided in the nut 2' along the circumferential direction, and the recess of the nut 2' in which the tip of the key 4' is housed may be a groove provided in the nut 2' along the axial direction.

In this actuator EA2, similar to the actuator EA1 in FIG. 1, the rotational force generated by a drive source such as a motor is input to the screw shaft 1 via the gear 13, causing the screw shaft 1 to rotate. When the screw shaft 1 rotates, the balls between the screw shaft 1 and the nut 2' circulate in the ball rolling path via a ball circulator (not shown), causing the nut 2' to perform linear motion. The axial force based on the linear motion of the nut 2' is then transmitted to the output shaft 3' via the cotter 4' and output via the output shaft 3'.

This actuator EA2 can reversibly release the connection between the nut 2' and the output shaft 3'. Here, this actuator EA2 is provided with an electromagnet 5' in addition to the electromagnet 5 in FIG. 1 as a release member capable of reversibly releasing the connection between the nut 2' and the output shaft 3'. Also, this actuator EA2 is provided with a spring 6' as an elastic member that holds down the key 4' at the connection position between the nut 2' and the output shaft 3'. The spring 6' is provided between the electromagnet 5' and the key 4'. The spring 6' is not particularly limited as long as it is an elastic member that holds down the key 4', such as a spring, a leaf spring, or a disc spring. The electromagnet 5' and the spring 6' can be stored in the output shaft 3'. Here, in order to make it possible to store the electromagnet 5' and the spring 6' in the output shaft 3', the thickness of the output shaft 3' at the storage position of the electromagnet 5 and the spring 6' may be made thicker. In addition, the distance between the electromagnet 5' and the key 4' can be set so that the key 4' can be pulled out of the nut 2' when the spring 6' is compressed.

Here, the movement of the nut 2' is restricted according to the stuck state or the loaded state of the power transmission system such as the motor, gear, or linear motion parts. At this time, when the stuck state or the high load state of the power transmission system is detected and a current is passed through the electromagnets 5, 5', the springs 6, 6' are compressed and the cotter 4 and the key 4' can be attracted to the electromagnets 5, 5' to a position where the cotter 4 and the key 4' are pulled out from the nut 2'. When the cotter 4 and the key 4' are pulled out from the nut 2', the movement of the nut 2' cannot be transmitted to the output shaft 3' via the cotter 4 and the key 4', and the movement of the output shaft 3' can be prevented from being restricted via the nut 2'. Therefore, the operation of the connection destination of the output shaft 3' can be prevented from being restricted via the output shaft 3', and the influence of the stuck state or the high load state of the power transmission system can be avoided.

In addition, the cotter 4 and key 4' can be pulled out of the nut 2' using the electromagnetic force of the electromagnets 5, 5' to release the connection between the nut 2' and the output shaft 3'. This eliminates the need to destroy the nut 2 or the cotter 4 and key 4' to release the connection between the nut 2' and the output shaft 3', and reduces the deterioration of the maintainability of the actuator EA2.

In addition, the connection between the nut 2' and the output shaft 3' can be restored by cutting off the current flowing through the electromagnets 5, 5'. Therefore, even if the connection between the nut 2' and the output shaft 3' is released, the actuator EA2 can be restored to normal operation without replacing the nut 2', cotter 4, and key 4'.

Furthermore, by using the cotter 4 and key 4' to connect the nut 2' to the output shaft 3', the nut 2' to the output shaft 3' can be connected or released by inserting and removing the cotter 4 and key 4', and there is no need to use a complex configuration such as a gripping mechanism or clutch mechanism to release the connection between the nut 2' and the output shaft 3'. Therefore, the nut 2' to the output shaft 3' can be connected while preventing the actuator EA2 from becoming larger and more expensive.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-mentioned embodiments and includes various modified examples. For example, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations.

For example, in the above embodiment, a spring is used to hold down the cotter or key when the nut and the output shaft are coupled, but as long as the cotter or key can be held down, the configuration is not limited to using a spring. For example, the cotter or key may be made of a permanent magnet (e.g., a neodymium magnet), or a permanent magnet may be embedded or attached to the surface of the cotter or key. When the nut and the output shaft are coupled, a repulsive force may be applied between the electromagnet and the permanent magnet to hold the cotter or key inside the nut, and when the nut and the output shaft are released from the coupling, an attractive force may be applied between the electromagnet and the permanent magnet to pull the cotter or key out of the nut.

Figure 6(a) is a cross-sectional view showing the configuration of the actuator when the nut and output shaft are connected according to the fifth embodiment, Figure 6(b) is a cross-sectional view showing an enlarged view of the cotter portion of Figure 6(a), Figure 7(a) is a cross-sectional view showing the configuration of the actuator when the nut and output shaft are released from the connection according to the fifth embodiment, and Figure 7(b) is a cross-sectional view showing an enlarged view of the cotter portion of Figure 7(a).

In Figures 6(a), 6(b), 7(a) and 7(b), the actuator EA3 has an output shaft 13, a cotter 4A and a motor 21, instead of the output shaft 3, the cotter 4, the electromagnet 5 and the spring 6 of the actuator EA1 in Figure 1.

The output shaft 13 outputs an axial force based on the linear motion converted by the nut 2. The output shaft 13 has a through hole 13A and openings 13C and 13D. The through hole 13A and openings 13C and 13D can be provided on the side of the output shaft 13. In this case, the tip of the cotter 4A can be accommodated in the recess 2A via the through hole 13A and openings 13C and 13D. The through hole 13A accommodates the rear end of the cotter 4A. The opening 13C accommodates the motor 21 at a distance from the cotter 4A in the radial direction of the output shaft 13. The opening 13D accommodates the bearing 7 so as to cover the motor 21.

The cotter 4A is used as a connecting member that connects the output shaft 13 to the nut 2. The cotter 4A penetrates the output shaft 13 in a direction perpendicular to the axial direction of the screw shaft 1 and can be inserted into and removed from the nut 2. The cotter 4A has an opening KA formed in the radial direction of the output shaft 13. The opening KA may be a through hole that penetrates the output shaft 13 in the radial direction. The opening KA has a female thread that can mesh with a male thread formed on the outer circumferential surface of the rotating shaft JA of the motor 21.

The actuator EA3 can reversibly release the connection between the nut 2 and the output shaft 13. Here, the actuator EA3 is equipped with a motor 21 as a release member that can reversibly release the connection between the nut 2 and the output shaft 13. The motor 21 can insert the cotter 4A into the recess 2A and pull it out from the recess 2A. The motor 21 has a rotating shaft JA on which a male thread is formed. The rotating shaft JA of the motor 21 is inserted into the opening KA of the cotter 4A. At this time, the male thread of the rotating shaft JA and the female thread of the opening KA are engaged, and the rotational motion of the rotating shaft JA is converted into linear motion of the cotter 4A.

Here, the motor 21 can insert the cotter 4A into the recess 2A as shown in FIG. 6(a) and FIG. 6(b) by switching the rotation direction of the rotating shaft JA, or can pull out the cotter 4A from the recess 2A as shown in FIG. 7(a) and FIG. 7(b). Therefore, by switching the rotation direction of the rotating shaft JA, the nut 2 and the output shaft 13 can be coupled or released from the coupling between the nut 2 and the output shaft 13. As a result, it is no longer necessary to destroy the nut 2 or the cotter 4A in order to release the coupling between the nut 2 and the output shaft 13, and after the stuck state of the power transmission system is eliminated, the actuator EA3 can be restored to normal operation without replacing the actuator EA3. In addition, by securing a space for installing the motor 21 on the output shaft 13, the coupling between the nut 2 and the output shaft 13 can be released, and the influence of the stuck state of the power transmission system can be avoided while suppressing the complexity and size of the configuration of the actuator EA3.

Figure 8(a) is a cross-sectional view showing the configuration of the actuator when the nut and output shaft are connected according to the sixth embodiment, Figure 8(b) is a cross-sectional view showing an enlarged view of the cotter portion of Figure 8(a), Figure 9(a) is a cross-sectional view showing the configuration of the actuator when the nut and output shaft are released from the connection according to the sixth embodiment, and Figure 9(b) is a cross-sectional view showing an enlarged view of the cotter portion of Figure 9(a).

In Figures 8(a), 8(b), 9(a) and 9(b), actuator EA4 has an output shaft 23, a cotter 4B and an actuator 31, instead of the output shaft 3, cotter 4, electromagnet 5 and spring 6 of actuator EA1 in Figure 1.

The output shaft 23 outputs an axial force based on the linear motion converted by the nut 2. The output shaft 23 has a through hole 23A and openings 23C and 23D. The through hole 23A and the openings 23C and 23D can be provided on the side of the output shaft 23. At this time, the tip of the cotter 4B can be accommodated in the recess 2A via the through hole 23A and the openings 23C and 23D. The through hole 23A accommodates the rear end of the cotter 4B. The opening 23C accommodates the actuator 31 at a distance from the cotter 4B in the radial direction of the output shaft 23. The opening 23D accommodates the bearing 7 so as to cover the actuator 31.

The cotter 4B is used as a connecting member that connects the output shaft 23 to the nut 2. The cotter 4B can be inserted and removed from the nut 2 by passing through the output shaft 23 in a direction perpendicular to the axial direction of the screw shaft 1.

The actuator EA4 can reversibly release the connection between the nut 2 and the output shaft 23. Here, the actuator EA4 includes an actuator 31 as a release member that can reversibly release the connection between the nut 2 and the output shaft 23. The actuator 31 has an output shaft JB. The output shaft JB of the actuator 31 is connected to the cotter 4B. The actuator 31 linearly moves the output shaft JB in the radial direction of the output shaft 23, and can insert the cotter 4B into the recess 2A or pull it out from the recess 2A. The actuator 31 may be a hydraulic actuator, a pneumatic actuator, or an electric actuator.

Here, the actuator 31 can insert the cotter 4B into the recess 2A as shown in FIG. 8(a) and FIG. 8(b) by advancing the output shaft JB, or can pull out the cotter 4B from the recess 2A as shown in FIG. 9(a) and FIG. 9(b) by retracting the output shaft JB. Therefore, by switching the advancing direction of the output shaft JB, the nut 2 and the output shaft 23 can be coupled, or the coupling between the nut 2 and the output shaft 23 can be released. As a result, it is no longer necessary to destroy the nut 2 or the cotter 4B in order to release the coupling between the nut 2 and the output shaft 23, and after the stuck state of the power transmission system is eliminated, the actuator EA4 can be restored to normal operation without replacing the actuator EA4. In addition, by securing a space for installing the actuator 31 on the output shaft 23, the coupling between the nut 2 and the output shaft 23 can be released, and the influence of the stuck state of the power transmission system can be avoided while suppressing the complexity and size of the configuration of the actuator EA4.

In the actuators EA1 to EA4 described above, as disclosed in JP 2012-42050 A, the cotter can be used as an axial force transmission element and the key can be used as a rotational force transmission element. In this case, both axial end faces of the cotter may be in contact with the nut and the output shaft, and both circumferential end faces of the cotter may have a circumferential gap between the nut and the output shaft. Also, both circumferential end faces of the key may be in contact with the nut and the output shaft, and both axial end faces of the key may have an axial gap between the nut and the output shaft.

As a result, even if twisting occurs on the output shaft, the effect can be absorbed by the circumferential and axial gaps, making it difficult for twisting to occur on the ball screw. This makes it possible to extend the life of the actuator that uses the linear motion device, even if misalignment occurs during assembly of the linear motion device and the output shaft.

Figure 10(a) is a cross-sectional view showing the configuration of the actuator when the nut and output shaft are connected according to the seventh embodiment, and Figures 10(b) to 10(d) are enlarged cross-sectional views showing the movement of the cotter when the connection between the nut and output shaft in Figure 10(a) is released.

In Fig. 10(a) and Fig. 10(b) to Fig. 10(d), the actuator EA5 has a nut 42, an output shaft 43 and a cotter 4C instead of the nut 2, the output shaft 3, the cotter 4, the electromagnet 5 and the spring 6 of the actuator EA1 in Fig. 1.

The nut 42 converts the rotational motion of the screw shaft 1 into linear motion in the axial direction of the screw shaft 1. The nut 42 has a recess 42A instead of the recess 2A in FIG. 2(b). The recess 42A is set to a shape such that the cotter 4C moves in the axial direction of the screw shaft 1 from a state accommodated in the recess 42A of the nut 42 based on the force applied to the cotter 4C in the axial direction of the screw shaft 1 and can come out of the recess 42A of the nut 42. At this time, in order to apply a force to the cotter 4C in the radial direction of the output shaft 43 when a force is applied to the cotter 4C in the axial direction of the output shaft 43, the recess 42A of the nut 42 can have an inclined surface MA. In addition, the shape of the recess 42A is set to correspond to the shape of the tip of the cotter 4C. For example, if the shape of the tip of the cotter 4C is conical, the shape of the recess 42A can be formed into a mortar shape.

The output shaft 43 outputs an axial force based on the linear motion converted by the nut 42. The output shaft 43 has a through hole 43A and an opening 23D. The through hole 43A and the opening 23D can be provided on the side of the output shaft 43. At this time, the tip of the cotter 4C can be accommodated in the recess 42A through the through hole 43A and the opening 23D. The through hole 43A accommodates the rear end of the cotter 4C. At this time, the height of the through hole 43A is set so that a space 43C is formed on the rear end side of the cotter 4C when the cotter 4C is accommodated in the recess 42A. The height of the space 43C can be set to a height required to allow the cotter 4C to come out of the recess 42A. The opening 23D accommodates the bearing 7 so that the bearing 7 is located above the space 43C.

The cotter 4C is used as a connecting member that connects the output shaft 43 to the nut 42. The cotter 4C can be inserted into and removed from the nut 42 by penetrating the output shaft 43 in a direction perpendicular to the axial direction of the screw shaft 1. The cotter 4C is set to a shape such that the cotter 4C can move from a state accommodated in the recess 42A of the nut 42 in the axial direction of the screw shaft 1 based on the force applied to the cotter 4C in the axial direction of the screw shaft 1 and can be removed from the recess 42A of the nut 42. At this time, the tip of the cotter 4C can be provided with an inclined surface MC so that when a force is applied to the cotter 4C in the axial direction of the output shaft 43, a force is also applied in the radial direction of the output shaft 43. For example, the shape of the cotter 4C can have a shape that narrows in the direction toward the tip, and the recess 42A can have a shape corresponding to the shape of the cotter 4C. At this time, the inclined surface MC of the cotter 4C can be in contact with the inclined surface MA of the recess 42A.

The actuator EA5 can reversibly release the connection between the nut 42 and the output shaft 43. Here, the actuator EA5 has a pressure medium PB that can be sealed in the space 43C to connect the nut 42 and the output shaft 43. The pressure medium PB may be a liquid such as oil, or a gas such as air. The actuator EA5 can release the pressure medium PB to release the connection between the nut 42 and the output shaft 43. The actuator EA5 has a pipe 52 and a control valve 53 as a release part that releases the pressure medium PB. The pipe 52 is connected to the space 51 and is drawn out to the outside of the output shaft 43. The control valve 53 closes and opens the passage of the pipe 52.

As shown in FIG. 10(b), the control valve 53 opens the passage of the pipe 52, introduces the pressure medium PB into the space 43C, and then closes the passage of the pipe 52, sealing the pressure medium PB within the space 43C. At this time, the pressure medium PB presses the cotter 4C, and the tip of the cotter 4C is accommodated in the recess 42A, thereby connecting the nut 42 and the output shaft 43.

Then, the power transmission system is fixed, and the actuator EA5 is always in a tensioned state. At this time, the control valve 53 opens the passage of the piping 52, releasing the pressure medium PB sealed in the space 43C, and the pressing force applied to the rear end of the cotter 4C is reduced. Then, as shown in Figures 10(c) and 10(d), when a force is applied to the cotter 4C in the axial direction of the output shaft 43, a force is also applied in the radial direction of the output shaft 43 via the inclined surfaces MA and MC. Therefore, the cotter 4C can be removed from the recess 42A as the cotter 4C moves in the axial direction of the output shaft 43, and the connection between the nut 42 and the output shaft 43 can be released. As a result, it is no longer necessary to destroy the nut 42 or the cotter 4C in order to release the connection between the nut 42 and the output shaft 43, and after the stuck state of the power transmission system is eliminated, the actuator EA5 can be restored to normal operation without replacing the actuator EA5. In addition, by providing the space 43B required for the cotter 4C to slip out of the recess 42A in the output shaft 43, the connection between the nut 42 and the output shaft 43 can be released, preventing the actuator EA5 from becoming too complicated and large in size, while avoiding the effects of a stuck power transmission system.

FIG. 11(a) is a perspective view showing one example of the configuration of the cotter in FIG. 10(a), and FIG. 11(b) is a perspective view showing another example of the configuration of the cotter in FIG. 10(a).
11(a), the cotter 4D has an inclined surface MD. The inclined surface MD can apply a force to the cotter 4D in the radial direction of the output shaft 43 when the force is applied to the cotter 4D in the axial direction of the output shaft 43. In this case, the shape of the tip of the cotter 4D can be wedge-shaped.

This makes it possible to apply force to the cotter 4D in the radial direction of the output shaft 43 when force is applied to the cotter 4D in the axial direction of the output shaft 43, making it possible to release the connection between the nut 42 and the output shaft 43, and also makes it possible to release the connection between the nut 42 and the output shaft 43 by simply providing an inclined surface MC on the cotter 4D, thereby preventing the configuration of the actuator EA5 from becoming too complicated and preventing the actuator EA5 from becoming too large and expensive.

In FIG. 11(b), the cotter 4E has an inclined surface ME. The inclined surface ME can be configured so that when a force is applied to the cotter 4E in the axial direction of the output shaft 43, a force is also applied in the radial direction of the output shaft 43. In this case, the shape of the tip of the cotter 4E can be rotationally symmetric about the radial axis of the output shaft 43, and can be, for example, conical.

This makes it possible to apply force to the cotter 4E in the radial direction of the output shaft 43 when force is applied to the cotter 4E in the axial direction of the output shaft 43, making it possible to release the connection between the nut 42 and the output shaft 43, and also allows the inclined surface ME to be provided on the cotter 4E with simple processing, preventing the configuration of the actuator EA5 from becoming too complicated and preventing the actuator EA5 from becoming too large and expensive.

FIG. 12 is a side view showing an example of a gap between the cotter and the nut according to the eighth embodiment.
In Fig. 12, the actuator EA6 includes a cotter 4F instead of the cotter 4C of the actuator EA5 in Fig. 10(a). A step HC is provided on the rear end side of the cotter 4F. A step DA capable of receiving the step HC is provided in the through hole 43A of the output shaft 43. The cotter 4F can be configured such that, when the steps HC and DA come into contact with each other, a gap Cc is provided between the inclined surface MC of the cotter 4F and the inclined surface MA of the recess 42A.

As a result, even if twisting occurs on the output shaft 43, the action can be absorbed by the gap Cc between the inclined surfaces MA and MC, making it difficult for twisting to occur on the ball screw. Therefore, even if misalignment occurs during assembly of the linear motion device and the output shaft 43, it is possible to extend the life of the actuator EA6, which uses the linear motion device.

FIG. 13 is a side view showing an example of a gap between the cotter and the output shaft according to the ninth embodiment.
13(a) and 13(b), the actuator EA7 includes a cotter 4G instead of the cotter 4C of the actuator EA5 in FIG. 10(a). A step HC is provided on the rear end side of the cotter 4G. A step DA capable of receiving the step HC is provided in the through hole 43A of the output shaft 43. The cotter 4G can be configured such that a gap Cd is provided between the steps HC and DA when the inclined surface MC of the cotter 4G and the inclined surface MA of the recess 42A come into contact with each other.

As a result, even if twisting occurs on the output shaft 43, the action can be absorbed by the gap Cd between the steps HC and DA, making it difficult for twisting to occur on the ball screw. Therefore, even if misalignment occurs during assembly of the linear motion device and the output shaft 43, it is possible to extend the life of the actuator EA7, which uses the linear motion device.

Figure 14(a) is a cross-sectional view showing the configuration of the actuator when the nut and output shaft are connected in the 10th embodiment, and Figures 14(b) to 14(d) are cross-sectional views showing enlarged views of the movement of the cotter when the connection between the nut and output shaft in Figure 14(a) is released.
14(a) and 14(b) to 14(d), the actuator EA8 includes an output shaft 63 and a spring 61 instead of the output shaft 43 and pressure medium PB of the actuator EA5 in FIG.

The output shaft 63 outputs an axial force based on the linear motion converted by the nut 4. The output shaft 63 has a through hole 63A. The through hole 63A can be provided on the side of the output shaft 63. At this time, the tip of the cotter 4C can be accommodated in the recess 42A via the through hole 63A. The through hole 63A accommodates the rear end of the cotter 4C. At this time, the height of the through hole 63A is set so that a space 63C is formed on the rear end side of the cotter 4C when the cotter 4C is accommodated in the recess 42A. The height of the space 63C can be set to a height required to allow the cotter 4C to slip out of the recess 42A.

The actuator EA8 can reversibly release the connection between the nut 42 and the output shaft 63. Here, the actuator EA8 includes a spring 61 that presses the cotter 4C to connect the nut 42 and the output shaft 63.
14B, the spring 61 can be disposed in the space 63C so as to contact the rear end surface of the cotter 4C. At this time, the compressive force of the spring 61 can be set so that the contact state between the contact surface MA of the nut 42 and the contact surface MC of the cotter 4C is maintained when the actuator EA8 is operating normally. In addition, the spring 61 can be configured so as to be capable of further contracting from the contracted pressure state when the nut 42 and the output shaft 63 are coupled until the cotter 4C is completely removed from the recess 42A.

Then, the power transmission system is fixed, and the actuator EA8 is always in a tensioned state. At this time, as shown in FIG. 14(c) and FIG. 14(d), when a force is applied to the cotter 4C in the axial direction of the output shaft 63, a force is also applied in the radial direction of the output shaft 63 via the inclined surfaces MA and MC. Therefore, the cotter 4C can be removed from the recess 42A as the cotter 4C moves in the axial direction of the output shaft 63, and the connection between the nut 42 and the output shaft 63 can be released. Therefore, it is no longer necessary to destroy the nut 42 or the cotter 4C in order to release the connection between the nut 42 and the output shaft 63, and after the stuck state of the power transmission system is resolved, the actuator EA8 can be restored to normal operation without replacing the actuator EA8. In addition, in order to release the connection between the nut 42 and the output shaft 63, it is no longer necessary to provide a detector that detects the stuck state of the power transmission system, a power unit that supplies power from the outside, and a control unit that controls the power based on the detection result of the stuck state, etc., and it is possible to avoid the influence of the stuck state of the power transmission system while suppressing the complexity of the configuration of the actuator EA8. Furthermore, by securing the space 63C necessary for the cotter 4C to come out of the recess 42A in the output shaft 63, it is possible to release the connection between the nut 42 and the output shaft 63, and it is possible to avoid the influence of the stuck state of the power transmission system while suppressing the complexity and size of the configuration of the actuator EA8.

1 Screw shaft, 2 Nut, 3 Output shaft, 4 Cotter, 5 Electromagnet, 5A Iron core, 5B Winding, 6 Spring, 7, 11 Bearing, 12 Housing, 13 Gear, 14 Gear fixing nut

Claims (18)

A screw shaft,
A nut that converts the rotational motion of the screw shaft into a linear motion in the axial direction of the screw shaft;
a coupling member for coupling an output shaft, which outputs an axial force based on the linear motion converted by the nut, to the nut;
a release member capable of releasing the connection between the nut and the output shaft ,
The linear motion device according to claim 1, wherein the release member is an electromagnet capable of pulling the coupling member out of the nut . 2. The linear motion device according to claim 1, further comprising an elastic member provided between the electromagnet and the connecting member, for holding the connecting member at a connecting position between the nut and the output shaft. The electromagnet is
A winding;
a core around which the winding is wound,
3. The linear motion device according to claim 2, wherein the iron core extends into the elastic member to a position where it does not hinder removal of the coupling member from the nut. A screw shaft,
A nut that converts the rotational motion of the screw shaft into a linear motion in the axial direction of the screw shaft;
a coupling member for coupling an output shaft, which outputs an axial force based on the linear motion converted by the nut, to the nut;
a release member capable of releasing the connection between the nut and the output shaft,
The release member includes a motor having a rotating shaft on which a male screw is formed,
The rotation axis is arranged along a direction perpendicular to the axial direction of the screw shaft,
The linear motion device, wherein the coupling member has an opening having a female thread that can mesh with the male thread. 5. The linear motion device according to claim 4, wherein the motor is capable of pulling the connecting member out of the nut. 6. The linear motion device according to claim 1 , wherein the release member is capable of reversibly releasing the connection between the nut and the output shaft. 7. The linear motion device according to claim 1 , wherein the coupling member is capable of passing through the output shaft in a direction perpendicular to an axial direction of the screw shaft and being inserted into and removed from the nut. 7. The linear motion device according to claim 1, wherein the release member is capable of returning the connection to its original state after releasing the connection. 9. The linear motion device according to claim 1, wherein the coupling member is a cotter or a key. The coupling member has a cotter and a key,
the cotter is disposed relative to the nut and the output shaft such that a circumferential gap is present in a circumferential direction of the output shaft,
The linear motion device according to claim 9 , wherein the key is disposed with an axial gap with respect to the nut and the output shaft in the axial direction of the output shaft. A screw shaft,
A nut that converts the rotational motion of the screw shaft into a linear motion in the axial direction of the screw shaft;
a coupling member for coupling an output shaft, which outputs an axial force based on the linear motion converted by the nut, to the nut;
a pressing portion capable of reversibly pressing the connecting member in a direction in which the connecting member is accommodated in the recess of the nut,
The shapes of the coupling member and the recess are set so that the coupling member can move from a state in which it is accommodated in the recess of the nut in the axial direction of the screw shaft based on a force applied in the axial direction of the screw shaft and can be removed from the recess of the nut ,
The coupling member has a shape narrowing in a direction toward a tip thereof, and the recess has a shape corresponding to the shape of the coupling member,
A linear motion device, characterized in that the tip of the connecting member is wedge-shaped. The linear motion device according to claim 11 , wherein the shapes of the coupling member and the recess are rotationally symmetric about an axis in the radial direction of the output shaft. The pressing portion is
a pressure medium capable of being sealed in a space provided on the rear end side of the coupling member;
The linear motion device according to claim 11 or 12, further comprising: a release portion that releases the pressure medium sealed in the space. 13. The linear motion device according to claim 11 , wherein the pressing portion is a spring provided on a rear end side of the connecting member. 15. The linear motion device according to claim 11, wherein the connecting member is arranged with a gap in a radial direction of the output shaft with respect to at least one of the nut and the output shaft. A linear motion device according to any one of claims 1 to 15 ;
An actuator comprising the output shaft. A linear motion device according to any one of claims 1 to 10;
The output shaft,
An actuator , wherein the output shaft has a storage portion for storing the release member at a position where the connection can be released. 18. The actuator according to claim 17 , wherein the storage portion is an opening provided in the output shaft.