JP7427876B2 - actuator - Google Patents

Description

The present invention relates to an actuator.

Conventionally, actuators that convert rotational driving force into linear axial force and output it are known.

For example, Patent Document 1 discloses an actuator using a ball screw. In this actuator, rotational motion of a screw shaft is converted into linear motion of a nut, and an axial force (on the shaft) is generated from an output shaft connected to the nut. force in the direction along the line) is output.

Japanese Patent Application Publication No. 2012-42050

Since the actuator described above can obtain a large axial force from a relatively small input torque, it may be applied to suspension technology for actively damping vibrations of a vehicle.

However, if the power transmission system (for example, motor, gear, ball screw, etc.) in the actuator becomes stuck due to a failure, there is a risk that the actuator will lose its movement and function as a suspension or the like.

Therefore, an object of the present invention is to provide an actuator with a fail-safe (fuse) function that separates the power side and the output side when the above-mentioned sticking occurs.

In order to solve the above problems, one aspect of the actuator according to the present invention includes a rotating part provided with a helical screw and into which rotational force is input, and a helical screw that engages directly or indirectly with the helical screw of the rotating part. is provided with a linear motion section that linearly moves along the rotation section as the rotation section rotates; an output shaft that moves linearly with the shaft and outputs axial force; and an output shaft that is inserted into both the linear motion part and the output shaft to interconnect the linear motion part and the output shaft; a coupling device that releases the coupling when a force exceeding the axial force of is applied between the linear motion part and the output shaft.

According to this type of actuator, if a force exceeding the maximum axial force is applied between the linear motion part and the output shaft due to the above-mentioned sticking, etc., the coupling device releases the connection, so there is a fail-safe function (fuse ) function is realized.

In the actuator, the coupling tool may be broken by a force exceeding the maximum axial force to disconnect the linear motion section from the output shaft. It is preferable that the coupling device, which releases the connection when it breaks, is made of a material that breaks due to a force that exceeds the maximum axial force, and that the linear motion part side and the output shaft side are separated by a force that exceeds the maximum axial force. It is also desirable to have a rupture structure that ruptures.

For connectors made of breakable materials, a stable fail-safe function can be obtained by selecting and adjusting the material. In addition, the connector having the fracture structure can easily achieve a desired fracture shape.

In the actuator, the coupling device is pulled out from the extraction target, which is at least one of the linear motion section and the output shaft, by a force exceeding the maximum axial force, thereby causing the coupling between the linear motion section and the output shaft to be removed. You can break the connection.

It is desirable that the connector, which is to be uncoupled by being pulled out, has a gap in the direction of the linear movement with respect to the inner wall to be pulled out, so that it can be pulled out by a force that exceeds the maximum axial force. Furthermore, it is preferable that the connecting tool has parallel surfaces facing each of the front and rear directions of the linear movement at the insertion point inserted into the extraction target, and that the parallel surfaces have a gap with the inner wall. .

A connector that can be removed by having a gap can easily achieve a fail-safe function by adjusting the gap. When this connector further has the parallel surface, the direction of force transmission between the linear motion part and the output shaft can be aligned with the direction of linear movement by the parallel surface.

In addition, the connector, which is uncoupled by being pulled out, has an end on the far side in the direction of insertion into the object to be pulled out, which is chamfered diagonally with respect to both the direction of linear movement and the direction of insertion. , it is also desirable that it be pulled out by a force that exceeds the maximum axial force mentioned above. Furthermore, the connecting tool has parallel surfaces facing each of the front and back directions of the linear movement at the insertion point inserted into the extraction target, and the edge of the parallel surface on the back side in the insertion direction is chamfered. It is desirable to be present.

For connectors that are chamfered so that they can be removed, a fail-safe function can be easily realized by adjusting the position and size of the chamfer. When this connector further has the parallel surface, the direction of force transmission between the linear motion part and the output shaft can be aligned with the direction of linear movement by the parallel surface.

According to the actuator of the present invention, a fail-safe (fuse) function is realized that disconnects the power side and the output side when the above-mentioned sticking occurs.

1 is a sectional view showing an embodiment of an actuator of the present invention. It is a perspective view showing some elements of an actuator. FIG. 3 is an enlarged view showing a portion of a connecting element. FIG. 6 is a diagram illustrating a method in which connected elements are uncoupled by destruction; It is a figure showing an example of a broken structure. FIG. 6 is a diagram illustrating a first method in which a connecting element is uncoupled by falling off; FIG. 7 is a diagram showing a second method in which the connecting elements are uncoupled by falling off;

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a sectional view showing one embodiment of the actuator of the present invention. FIG. 1 shows a cross-sectional view taken along a plane along the center of the output shaft of the actuator. Furthermore, for convenience of understanding, some elements are shown in external view rather than in cross section. FIG. 2 is a perspective view showing some elements of the actuator.

The actuator 1 of this embodiment converts rotational force input from a drive source such as an electric motor into axial force (force in the direction along the axis) by using a ball screw that converts rotational motion into linear motion. This is a ball screw type direct-acting actuator that outputs

The actuator 1 of this embodiment includes a ball screw 10 that converts rotational motion into linear motion, a transmission gear 20 that receives rotational force from a drive source such as an electric motor (not shown), and transmits it to the screw shaft 11 of the ball screw 10. A hollow output shaft 30 that is connected to the nut 13 of the ball screw 10 and outputs the axial force converted from the rotational force by the ball screw 10, and a substantially cylindrical housing member that contains the ball screw 10 and the output shaft 30. 40, a ball bearing 51 that rotatably holds the screw shaft 11 of the ball screw 10, and a bearing housing 50 that fixes the ball bearing 51 to the housing member 40. The transmission gear 20 is fixed to the screw shaft 11 with a gear fixing nut 21.

The screw shaft 11 of the ball screw 10 corresponds to an example of a rotating part according to the present invention, and the nut 13 of the ball screw 10 corresponds to an example of a linear moving part according to the present invention. Note that the actuator of the present invention may have a structure in which the rotating part is a nut and the linear moving part is a screw shaft, or the actuator may have a structure in which the rotating part is a nut and the linear moving part is a screw shaft, or the helical screws are directly engaged with each other instead of a ball screw that indirectly engages through balls. Engaging bolts and nuts may also be used. Further, the output shaft 30 corresponds to an example of an output shaft according to the present invention.

The ball screw 10 includes a screw shaft 11 having a helical thread groove 11a on the outer circumferential surface, a nut 13 having a helical thread groove 13a on the inner circumferential surface opposite to the thread groove 11a of the screw shaft 11, and both thread grooves. A plurality of balls (not shown) loaded so as to be able to freely roll in a spiral ball rolling path formed by 11a and 13a, and balls that circulate the balls back from the end point to the starting point of the ball rolling path. A circulation path (not shown) is provided. That is, the screw shaft 11 and the nut 13 are indirectly engaged through the ball.

While moving within the ball rolling path, the ball rotates around the screw shaft 11 and reaches the end point of the ball rolling path, where it is scooped up from the ball rolling path and placed in one of the ball circulation paths. Enter the end. The balls that have entered the ball circulation path pass through the ball circulation path, reach the other end of the ball circulation path, and are returned from there to the starting point of the ball rolling path.

Note that the materials of the screw shaft 11, nut 13, and the ball are not particularly limited, and general materials can be used, such as metals such as steel and ceramics. Moreover, the cross-sectional shape of the thread grooves 11a and 13a may be circular arc shape or Gothic arc shape.

In the ball screw 10, when the nut 13 and the screw shaft 1, which are indirectly engaged through the balls, are rotated relative to each other, the screw shaft 11 and the nut 13 are brought into contact with each other through the rolling motion of the balls. Move in a straight line relative to the axial direction. An endless ball path is formed by the ball rolling path and the ball circulation path, and the balls rolling in the ball rolling path circulate endlessly in the endless ball path. Therefore, the screw shaft 11 and the nut 13 can continuously move linearly. The direction of linear movement of the nut 13 is determined by the direction of rotation of the screw shaft 11.

The ball screw 10 and the output shaft 30 connected to the nut 13 of the ball screw 10 are contained in the internal space of the housing member 40, and the screw shaft 11 of the ball screw 10 and the output shaft 30 are connected to the housing member 40. arranged coaxially. Further, the nut 13 is contained in one axial end (the opening at the lower end in FIG. 1) of the hollow interior 30a of the output shaft 30, and the nut 13 and the output shaft 30 are coaxial and nested.

The nut 13 is connected to the output shaft 30 by a connecting element 53. In this embodiment, two connecting elements 53 are provided as an example. When the nut 13 moves linearly, the axial force is transmitted to the output shaft 30 by the connecting element 53, and since the output shaft 30 moves linearly together with the nut 3, the axial force is output from the output shaft 30. The connecting element 53 corresponds to an example of a connecting tool according to the present invention.

A ring-shaped sliding bearing 55 that goes around the output shaft 30 so as to cover the connecting element 53 is provided between the output shaft 30 and the housing member 40 . The sliding bearing 55 is fixed to the outer surface of the output shaft 30 and supports the output shaft 30 with respect to the housing member 40. The sliding bearing 55 slides on the inner peripheral surface of the housing member 40 and moves in the axial direction within the housing member 40 together with the output shaft 30.
Here, details of the connection structure by the connection element 53 will be explained.
FIG. 3 is an enlarged view showing a portion of the connecting element.

The output shaft 30 is provided with a through hole 31 extending in the radial direction. The connecting element 53 is press-fitted into the through hole 31 of the output shaft 30 from the outside of the output shaft 30, and the back side of the connecting element 53 in the press-fitting direction is fitted into the recess 13b provided in the nut 13. In other words, the connecting element 53 fits into the through hole 31 of the output shaft 30 with a negative clearance, and fits into the recess 13b of the nut 13 with a clearance.

In addition, parallel surfaces 53a are provided on the back side of the connecting element 53 in the press-fitting direction, and the parallel surfaces 53a face the front and rear of the output shaft 30 in the axial direction (that is, the direction along the axis). By pushing the inner wall of the nut 13 in the axial direction, axial force is transmitted from the nut 13 to the output shaft 30. The transmission direction of the axial force is correctly aligned in the axial direction by being transmitted by the parallel surface 53a.

The connection between the nut 13 and the output shaft 30 by the connection element 53 is broken when an excessive force in the axial direction is applied between the nut 13 and the output shaft 30. The excessive force here is a force that is greater than the maximum output by the actuator 1 and exceeds the maximum axial force generated in the nut 13 due to the maximum driving force transmitted from the transmission gear 20 to the screw shaft 11 of the ball screw 10. It is power.

When the coupling element 53 is uncoupled by such an excessive force, a so-called fail-safe function is realized. That is, if sticking occurs somewhere in the power transmission path from the drive source to the nut 13 for the transmission gear 20, the power side and the output side are separated and the movability of the output shaft 30 is guaranteed. Therefore, if the actuator 1 is incorporated into a suspension, for example, the function of the suspension will be ensured even if the above-mentioned sticking occurs.

Such a fail-safe function is effective for vertical actuators such as those used in vibration damping devices for railways, for example. A railway vehicle has a car body and a bogie that are separated, and an air spring is installed between the car body and the bogie. In the case of a system in which low-frequency vibrations are absorbed by the air spring and high-frequency vibrations are damped by a vertical actuator, if the actuator is stuck, the position of the vehicle body may also be fixed. If there is a failsafe function as described above, even in the event of such a fixation, for example, the air spring can be lowered to the maximum extent and the weight of the vehicle body can be applied to the fixed actuator to release the fixation, thereby avoiding the fixation of the vehicle body.
Here, as a method for uncoupling the connecting element 53, there may be a method by destruction or a method by falling off.
Each method by which the connecting element 53 unlinks will be described below.
FIG. 4 is a diagram illustrating how the connecting element 53 is uncoupled by breaking.

The connecting element 53 in the method shown in FIG. 4 is made of a material with low hardness, such as aluminum, and is broken at once by the above-mentioned excessive force and separated into the nut 13 side and the output shaft 30 side. Although it is desirable that the connecting element 53 be destroyed at once, if the connecting element 53 is destroyed by excessive force, the fail-safe function can be realized even if it is not destroyed at once.
Since the connecting element 53 remains inside the actuator 1 even after being destroyed, it does not affect peripheral devices of the actuator 1 or the environment.

In the method shown in FIG. 4, the material is adjusted so that the connecting element 53 can be destroyed at once under desired conditions. A more desirable fractured state can be easily realized by providing a fracture structure in addition to or apart from such material adjustment.
FIG. 5 is a diagram showing an example of a fractured structure.

The connecting element 53 shown in FIG. 5 is provided with a groove 53b at the boundary between the nut 13 side and the output shaft 30 side as an example of a fracture structure. When the above-described excessive force is applied, the presence of the groove 53b ensures that the connecting element 53 is broken into the nut 13 side and the output shaft 30 side. In addition to the groove 53b shown in FIG. 5, the fracture structure may be, for example, a structure in which a portion on the nut 13 side and a portion on the output shaft 30 side are bonded. In such an adhesive structure, when the above-mentioned excessive force is applied, the connecting element 53 is broken at the adhesive location.
Next, a method of uncoupling the coupling element 53 by falling off will be described.
FIG. 6 is a diagram showing a first method in which the connecting element 53 is uncoupled by falling off.

In the first method shown in FIG. 6, a gap 53c between the parallel surface 53a of the connecting element 53 and the inner wall of the recess 13b of the nut 13 is set to be large. This gap 53c is large enough to always maintain the connection between the nut 13 and the output shaft 30 during normal use (FIG. 6(A)).

When the above-mentioned excessive force is applied (FIG. 6(B)), the connection element 53 is tilted significantly with respect to the nut 13 and the output shaft 30 due to the existence of the gap 53c, and furthermore, the connection element 53 is pushed into the recess of the nut 13. 13b and enters the falling state (FIG. 6(C)). Since the connecting element 53 remains inside the actuator 1 even after it is removed from the nut 13, it does not affect peripheral devices of the actuator 1 or the environment.

In the method shown in FIG. 6, the size of the gap 53c is adjusted so that the connecting element 53 will fall off under desired conditions. The size of such a gap 53c can be determined by mechanical calculation or analysis, so it is easy to design.
FIG. 7 is a diagram showing a second method in which the connecting element 53 is uncoupled by falling off.

In the second method shown in FIG. 7, a large chamfer 53d is provided at the end of the connecting element 53 on the back side (lower side in FIG. 7) in the insertion direction where the connecting element 53 is inserted into the nut 13. . This chamfer 53d is inclined with respect to both the direction of the axial force and the direction of insertion.

Further, the above-described parallel surface 53a is provided on the near side in the insertion direction (upper side in FIG. 7) with respect to the chamfer 53d. During normal use (FIG. 7(A)), the nut 13 and the output shaft 30 are connected by the parallel surface 53a, and axial force is transmitted.

When the above-mentioned excessive force is applied (FIG. 7(B)), the connecting element 53 tilts significantly with respect to the nut 13 and the output shaft 30 due to the presence of the chamfer 53d, and furthermore, the connecting element 53 tilts against the nut 13. It comes out of the recess 13b and becomes a fallen state (FIG. 7(C)). Since the connecting element 53 remains inside the actuator 1 even after it is removed from the nut 13, it does not affect peripheral devices of the actuator 1 or the environment.

In the method shown in FIG. 7, the size and inclination of the chamfer 53d are adjusted so that the connecting element 53 will fall off under desired conditions. Design is easy because such size and inclination can be determined through mechanical calculations and analysis.
Note that although FIGS. 6 and 7 show an example in which the connecting element 53 comes off from the nut 13, the connecting element 53 may come off from the output shaft 30.
Furthermore, the above-described method of uncoupling the connecting element 53 by breaking and the method of uncoupling the connecting element 53 by falling off may be used in combination.

DESCRIPTION OF SYMBOLS 1... Actuator, 10... Ball screw, 20... Transmission gear, 30... Output shaft, 31... Through hole, 40... Housing member, 11... Screw shaft, 13... Nut, 13b... Recessed part, 53... Connection element, 53a... Parallel Surface, 53b...groove, 53c...gap, 53d...chamfer

Claims (1)

a rotating part provided with a spiral screw and into which rotational force is input;
a linear motion part that is provided with a helical screw that engages directly or indirectly with the helical screw of the rotating part, and that moves linearly along the rotating part as the rotating part rotates;
an output shaft that is connected to the linear motion section in a coaxial and nested arrangement with the linear motion section, and that moves linearly together with the linear motion section to output an axial force;
It is inserted into both the linear motion part and the output shaft to interconnect the linear motion part and the output shaft, and the force exceeding the maximum axial force accompanying the rotational force is inserted between the linear motion part and the output shaft. a coupling device that is not destroyed by a force exceeding the maximum axial force that breaks the connection when applied between the coupling device and the shaft;
Equipped with
The connecting tool is inserted into the extraction target, which is at least one of the linear motion part and the output shaft, and is fitted with a clearance, and is inserted into the extraction target and moved into the insertion position where the clearance fit is achieved. The parallel surface receives the axial force on the parallel surface, and the end of the parallel surface on the back side in the insertion direction into the extraction target is aligned with the direction of the linear movement and the insertion direction. By being chamfered diagonally with respect to both directions, it is assumed that a force that exceeds the maximum axial force causes it to come out of the extraction target and break the connection between the linear motion part and the output shaft. Characteristic actuator.

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