JP2782036B2 - Linear actuator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a linear actuator, and more particularly, to a linear actuator using a stepping actuator which can be rotated stepwise in an arbitrary direction in a forward or reverse direction by a fixed angle. The present invention relates to a linear actuator capable of step driving.

[0002]

2. Description of the Related Art In a linear actuator using a servomotor which has been generally used in the past, as shown in FIG. 7, a ball rotatably supported on a body 1 via a speed reducer 3 by a servomotor 2 is used. The screw 4 is driven to rotate, and the output member 6 provided with a female screw into which the ball screw 4 is screwed is linearly driven on the body 1 along the ball screw 4. In such a linear actuator, the rotation angle of the servomotor 2 is precisely controlled while being detected by the encoder 5, whereby the position of the output member 6 is accurately controlled.

This linear actuator using a servomotor has the advantage that precise control is possible. However, the speed reducer 2 is indispensable for driving with a large torque because of high speed and small torque. Yes, and the position is lost when the power is turned off, so that the device becomes complicated and expensive, such as the necessity of a power failure stop type brake. Furthermore, not only the device but also the control system is complicated and expensive.

On the other hand, when a stepping motor is used in place of the servo motor, the output member can be driven stepwise in accordance with the movement by a constant rotation for each input pulse. There is a problem that the operation is uncertain due to the step-out phenomenon, and the apparatus becomes expensive as in the case of using the servomotor.

[0005]

SUMMARY OF THE INVENTION The technical problem of the present invention is to use a stepping actuator which can be rotated stepwise in any direction in a forward or reverse direction by a fixed angle, and to use a stepping actuator as compared with a case where a servomotor is used. Demonstrates high thrust without the use of a reducer, high holding torque without the use of a brake, and accurate sequence control using a simpler sequence control than when a stepping motor is driven by open loop control. It is an object of the present invention to provide a linear actuator which can control the drive more accurately, and can linearly step-drive the output member by a small, simple, and inexpensive device with a large thrust.

[0006]

A linear actuator according to the present invention for solving the above-mentioned problem is provided with a ball screw rotatably driven by being connected to an output shaft of a stepping actuator as follows. It is constituted by providing an output member which is supported and screwed onto the ball screw and guided in the axial direction on the body.

The stepping actuator includes a pair of linear drive members for normal rotation and reverse rotation, which are non-rotatably held by the outer frame and are independently driven in the axial direction. A rotating motion member connected to the output shaft and restrained from moving in the axial direction,
Between the pair of rectilinear driving members and the rotary motion member, one of the member surfaces is provided with an endless groove which is alternately inclined in the opposite direction with respect to the generatrix and is connected to each other at an end. The other member is provided with a projection that elastically presses against the groove, and between the groove and the projection, the projection is sequentially contacted with the projection with a change in the driving direction of the linear drive member near the groove end. A groove selecting mechanism for selecting an adjacent groove is provided, and ends of each row of the endless grooves are connected by a circumferential groove, thereby rotating the axial movement of each linear drive member. unidirectional rotation conversion mechanism for converting the successive steps rotational forward and reverse movement member was composed of
Things .

Further, the stepping actuator includes a pair of linear drive members for normal rotation and reverse rotation which are rotatably held by the outer frame and are independently driven in the axial direction, and the linear drive members have the same structure. A rotation movement member connected to the output shaft and capable of transmitting the rotation of the linear drive member but relatively moving in the axial direction with respect to the linear drive member, between the outer frame and the pair of linear drive members. In the surface of one of the members, a groove which is alternately inclined in the opposite direction with respect to the generatrix and which is connected to each other at an end and has an endless shape is provided, and the other member has an elasticity with respect to the groove. A protrusion is provided between the groove and the protrusion, and a groove selection mechanism is provided between the groove and the protrusion for sequentially selecting the groove adjacent to the protrusion with a change in the driving direction of the linear drive member near the groove end. The ends of each row of said grooves and endless connected by circumferential grooves, these rectilinear driving each
The movement of the moving member in the axial direction is
A one-way rotation conversion mechanism that converts to continuous step rotation is configured.
Can be achieved .

In the stepping actuator of the linear actuator, a groove selecting mechanism for sequentially selecting the grooves adjacent to the projections in accordance with the change of the driving direction of the linear drive member is provided with the drive of the linear drive member. The forward groove toward the groove end can be configured by providing a step that deepens the return groove when returning from the groove end, and furthermore, a pair of linear drive members for normal rotation and reverse rotation are axially moved. As means for driving, the outer frame may be a hydraulic cylinder, and the pair of linear driving members may be pistons independently driven by hydraulic pressure acting on them.

[0010]

In the linear actuator having the above-described structure, the ball screw supported by the fuselage has a stepping mechanism.
The output member, which is rotationally driven by the actuator and screwed with the ball screw, is linearly step-driven on the body. In order to drive the output member, in the stepping actuator, when one of the pair of linear driving members is driven by an arbitrary driving unit, the linear driving member moves forward,
The forward or reverse rotation is transmitted to the rotary motion member by the one-way rotation conversion mechanism. When the other linear drive member is driven, the reverse rotation is transmitted to the rotary motion member.

When the protrusion of the one-way rotation converting mechanism reaches the groove end by driving the linear driving member, the driving direction of the linear driving member is changed. The rotary motion member is provided with a continuous rotation in one direction, which is output through the output shaft, so as to cause the child to select a groove adjacent in sequence. Also, when the rotary motion member is driven to rotate via the one-way rotation conversion mechanism by the reciprocating motion of one of the linear drive members, the restriction of rotation by the fitting of the protrusion and the groove in the other one-way rotation conversion mechanism is released. However, since the ends of the grooves are connected by the circumferential grooves, continuous rotational drive in the forward or reverse direction of the rotary motion member can be obtained.

Therefore, a stepping actuator which can be rotated stepwise in any direction by a constant angle in a forward or reverse direction is used, and a higher thrust is exerted than when a servomotor is used. Is large,
Further, a small, simple, and inexpensive linear actuator capable of accurately controlling the drive by a simple sequence control as compared with the case where the stepping motor is driven by the open loop control can be obtained.

[0013]

FIG. 1 shows an embodiment of a linear actuator according to the present invention. The linear actuator includes a ball screw 14 rotatably supported on a body 11 by a pair of bearings 15, and a stepping actuator 12 is connected to the ball screw 14 via a coupling 13. The body 11 is provided with a pair of linear bearings (rails) 18 parallel to the axial direction of the ball screw 14. I guide you. The output member 16 is configured as, for example, a moving table, and is linearly step-driven on the body 11 by rotational driving of the output shaft of the stepping actuator 12, and its position is controlled.

The above stepping actuator 12
Can be configured as illustrated in FIGS. In this stepping actuator, two sets of one-way rotation converting mechanisms for converting the motion of the linear driving members 22A and 22B driven in the axial direction into rotation at a fixed angle and outputting the rotation from the output shaft 24 are arranged side by side in the axial direction. , And the output shaft is rotated forward or backward by each one-way rotation conversion mechanism.

The structure of the stepping actuator will be described in detail.
Has slidably accommodated therein a pair of linear drive members 22A and 22B for forward rotation and reverse rotation which are driven independently in the axial direction on the same axis, and have a common rotary movement member 23 inside them. Is inserted. This rotary motion member 23
Has an output shaft 24 integrated therewith, and this output shaft 2
4 is projected from the outer frame 21 to the outside, and is supported by bearings 25 and 26 provided on covers 27 and 28 for closing both ends of the outer frame 21 so as to be rotatable and immovable in the axial direction.

The rectilinear driving members 22A and 22B are fitted to the outer frame 21 with a deformed cross section, thereby disabling rotational movement with respect to the outer frame 21.
A one-way rotation conversion mechanism, which will be described in detail below, is inserted between the outer frame 21 and the output shaft 24 by sealing with a seal member. Is provided. The outer frame 21 and the linear drive members 22A and 22B do not need to be fitted in irregular cross sections as long as mutual rotation can be suppressed.

As means for driving the linear driving members 22A and 22B in the outer frame 21 in the axial direction, both ends of the outer frame 21 are airtightly closed by covers 27 and 28 to form a fluid pressure cylinder. The linear drive members 22A, 22B are each used as a piston, and are selected between the linear drive members 22A, 22B and the covers 27, 28 through a solenoid valve 29 mounted on the cover 27 and a flow path 31A or 31B in the outer frame. Pressure fluid (pressurized air, pressure oil) can be supplied, and the fluid pressure is applied to the end face of the linear drive member 22A or 22B to drive them inward (forward). ing. At the same time as discharging the pressure fluid, the pressure fluid can be supplied between the linear driving members 22A and 22B through the flow path 31C by the solenoid valve 30, whereby the linear driving member that has previously moved forward is returned. It is configured to be.

The linear drive members 22A, 22B
Can be driven not only by the fluid pressure described above but also by using, for example, a solenoid or other mechanical drive means. In this case, the linear drive members 22A and 22B
Of course, there is no need to seal between the outer frame 21 and the output shaft 24, and between the outer frame 21 and the covers 27 and 28.

Between the linear drive members 22A and 22B and the rotary motion member 23, the motion of the linear drive members 22A and 22B driven in the axial direction is converted into forward and reverse rotations at a certain angle, respectively. A pair of one-way rotation conversion mechanisms for outputting are arranged side by side in the axial direction.

That is, as shown in a developed view of FIG. 4, grooves 32A and 32 alternately inclined in the opposite direction for forming a one-way rotation conversion mechanism are formed on the cylindrical surface of the rotary motion member 23.
The row of B corresponds to 2 corresponding to the linear drive members 22A and 22B.
They are arranged side by side. The rows of these grooves 32A and 32B are formed endlessly by alternately inclining in opposite directions with respect to the generatrix of the rotary motion member 23 and connecting adjacent grooves to each other at their ends. is there. On the other hand, the linear drive members 22A and 22B are provided with ball-shaped projections 33A and 33B which are elastically pressed against the grooves 32A and 32B of the rotating member 23, respectively. The ball-shaped projections 33A, 33B are fitted into holes provided in the linear drive members 22A, 22B, and are inserted into the grooves 32A, 32B from behind by annular springs 35A, 35B.
It is configured to be pressed against.

In order to reciprocate the rotary motion member 23 in one direction in the forward or reverse direction by reciprocating the one linear drive member, the protrusions 33A, 33B are reciprocated by the linear drive members 22A, 22B. Must be sequentially transferred to the adjacent grooves. Therefore, in each of the connecting portions at the ends of the grooves 32A and 32B, the connecting portions at the ends of the grooves 32A and 32B are adjacent to the projections 33A and 33B with the change in the driving direction of the linear drive members 22A and 22B. A groove selecting mechanism for selecting the grooves 32A and 32B to be provided is provided. As the groove selecting mechanism, a groove (return groove) when the projections 33A and 33B return to the connecting portion of the grooves 32A and 32B and a groove (return groove) when returning from the connecting portion is connected to each of the connecting portions. Step 36 in the section (immediately before the straight drive end)
A, 36B, so that the projections 33A, 33B naturally select the adjacent return groove in cooperation with the springs 35A, 35B. In addition,
Of course, the groove deepened by the steps 36A and 36B is returned to the original depth before it reaches the other end.

The groove selecting mechanism in the two rows of grooves 32A and 32B provided in the rotary motion member 23 operates the steps 36A and 3 so as to select adjacent grooves in opposite directions.
6B, the linear drive members 22A, 22B
Function as for normal rotation and for reverse rotation, respectively.

Further, one of the linear drive members 22
When a rotational motion is given to the rotary motion member 23 by A or 22B, it is necessary to be rotatable between the other linear drive member and the rotary motion member 23. Therefore, the grooves 32A, 32A, The ends of each row of 32B are connected by circumferential grooves 37A and 37B. These circumferential grooves 37A, 37B correspond to the grooves 32A, 32B.
The end is not so shallow that the function of preventing rotation (angle positioning) of the end is not lost.

The operation of the stepping actuator having such a configuration will be described. First, by switching the solenoid valve 29, pressure is selectively applied to the outer end face side of one of the linear drive members 22A or 22B through the flow path 31A or 31B. Fluid is supplied, whereby either the right or left linear drive member moves inward, and simultaneously with the discharge of the pressure fluid, the solenoid valve 30
Drive members 22A and 22B through the flow path 31C.
When the pressurized fluid is supplied during this period, the forwardly moving linear drive member is caused to return, and accordingly, the forward or reverse rotation is transmitted to the rotary motion member 23 by the one-way rotation conversion mechanism.

That is, for example, the linear drive member 22A is
When moving to the right from the left end position of the
Is restricted by the outer frame 21 and does not rotate. During the movement, the protrusion 33A moves in the groove 32A of the rotating member 23 to rotate the rotating member 23 by a required angle determined by the groove shape. When the linear drive member 22A returns to the left end position in FIG. 4 due to the switching of the pressure fluid, the protrusion 33A similarly moves back in the adjacent groove 32A while rotating the rotary motion member 23, thereby rotating the rotary motion member 23A. The member 23 is provided with a continuous rotation in one direction, which is output through an output shaft 24.

In this case, since the return groove is made deeper than the forward groove at the end of the groove 32A by the step 36A, after the protrusion 33A reaches the groove end, the straight drive member 22 is moved.
In the case of the backward movement due to the change of the driving direction of A, the protrusion 33A always stably selects the adjacent backward groove by the groove selecting mechanism, and the rotary motion member 23 is reliably given continuous rotation in a certain direction. .

For example, when the rectilinear driving member 22A reciprocates by the pressurized fluid and tries to rotationally drive the rotary motion member 23 via the one-way rotation converting mechanism, the rectilinear driving member 22B rotates with respect to the outer frame 21. Since it is restrained, it is necessary to release the restraint of the rotary motion member 23 whose rotation is restricted by the fitting of the projection 33B into the groove 32B. Groove 32 on rotating member 23
A, 32B connecting the ends of the circumferential grooves 37A, 3B
Numeral 7B enables circumferential movement of the projection 33B in this case, whereby the rotary motion member 23 is continuously rotated in the forward or reverse direction by the reciprocating drive of the linear drive member 22A or 22B. Will be done. In addition,
Since the circumferential grooves 37A and 37B are made shallower with respect to the terminal ends of the grooves 32A and 32B, even if the projection 33A rolls in the circumferential grooves 37A or 37B, the grooves 7A and 37B will eventually be formed.
The protrusion 33A is settled in a state of being fitted into the deep groove at the end of the 2A or 32B, and the positioning of the projection 33A is stably performed.

FIGS. 5 and 6 show other examples of the groove selection mechanism in the stepping actuator.
The configuration of this stepping actuator has no particular difference from the configuration example shown above except for the groove selection mechanism. Briefly describing the configuration, this stepping
In the actuator, a pair of linear drive members 42A, 42B for forward rotation and reverse rotation, which are independently driven in the axial direction on the same axis, are slidably housed inside the outer frame 41 having a cylindrical shape. A common rotary motion member 43 is inserted into the inside, and an output shaft 44 integrated with the rotary motion member 43 is protruded from the outer frame 41 to the outside, and is rotatable axially by bearings 45 and 46 provided on the outer frame 41. Is immovable.

The linear drive members 42A and 42B disable rotation with respect to the outer frame 41 by fitting a pin 48 into a linear groove 47 on the inner surface of the outer frame 41. Is sealed with a seal member and inserted.
In addition, a one-way rotation conversion mechanism, which will be described in detail below, is provided between the outer frame 41 and the rotary motion member 43.

The linear drive members 42A and 42B supply a pressure fluid by a valve (not shown) through a pressure fluid supply / discharge port 51A or 51B provided in the outer frame 41 and drive them inward. ), And at the same time as discharging the pressure fluid, the linear drive members 42A, 42A through the supply / discharge port 51C.
The pressurized fluid is supplied during 2B, whereby the rectilinear driving member that has moved forward is moved backward.

Between the linear driving members 42A, 42B and the rotary motion member 43, the linear driving members 42A, 42
As a pair of one-way rotation conversion mechanisms for converting the motion of B into forward and reverse rotations of a fixed angle, the surface of the rotary motion member 43 is alternately and reversely rotated on the surface of the rotary motion member 43 as shown in a developed view of FIG. The row of the inclined grooves 52A and 52B is
2A and 42B are arranged in parallel with each other in two rows, and the linear drive members 42A and 42B are each provided with a projection 53A, which is elastically pressed against the grooves 52A and 52B of the rotary motion member 43 by springs 55A and 55B. 53B are provided. Further, when a rotational motion is given to the rotary motion member 43 by one of the linear drive members 42A or 42B, the other linear drive member and the rotary motion member 43 are allowed to rotate. Circumferential groove 5 at the end of each row
7A, 57B and these circumferential grooves 57
A and 57B are made shallower with respect to the end portions of the grooves 52A and 52B.

The grooves 52A and 52B are alternately inclined in the opposite direction with respect to the generatrix of the rotary motion member 43, as in the case of FIG. 4, so that adjacent grooves are connected to each other at their ends. , But the reciprocating drive of the linear drive members 42A, 42B causes the protrusion 53
When the grooves A and 53B reach the groove ends, in order to configure a groove selection mechanism for sequentially shifting the grooves to adjacent grooves, the linear drive members 42A and 42A are provided in the respective grooves 52A and 52B.
B drives the protrusions 53A and 53B toward the groove ends to form curved grooves, and the straight drive members 42A and 4A at the groove ends.
The return groove portion of the adjacent groove to which the protrusion returns in accordance with the change of the driving direction of 2B is formed in a straight line.

Furthermore, in order to stably move the straightened return groove portion to the projection, the above-mentioned circumferential grooves 57A, 57A,
57B, while the protrusions 53B and 53A move back through the linear return grooves in the grooves 52B and 52A on the other side, the protrusion 53
Concave portions 58A and 58B for holding A and 53B are formed.

With this configuration, for example, when the linear drive member 42B reciprocates and the projection 53B moves through the linear return groove in the groove 52B in the reciprocation, the projection of the linear drive member 42A Since 53A is recessed in the recess 58A in the circumferential groove 57A, the projection 53B of the linear drive member 42B stably moves along the straight return groove in the groove 52B, and then projects in the curved portion of the groove 52B. Since the child 53B rotates the rotary motion member 43, the protrusion 53A escapes from the concave portion 58A in the circumferential groove 57A accordingly, and the rotational drive of the rotary motion member 43 is continued.

In the example described above, grooves are provided on the surfaces of the rotary motion members 23 and 43, and the linear drive members 22A and 22A are provided.
A case is shown in which a protrusion is provided on the groove 22B or 42A, 42B to elastically press against these grooves. Conversely, grooves are provided on the linear drive member side, and the protrusion is provided on the rotary motion member. Can also be provided. On the other hand, in the above-mentioned stepping actuator, since the rotation angle of the rotary motion member accompanying the movement of the linear drive member is large, if a speed reducer is added between the stepping actuator and the ball screw, a higher torque, more precise positioning, Fine feed can be provided.

In the two stepping actuators described above, the linear drive members 22A, 22B or 42A,
42B cannot be rotated with respect to the outer frame,
A pair of linear drive members 22A, 2 for normal rotation and reverse rotation that are held by the outer frames 21, 41 via a one-way rotation conversion mechanism and are driven independently in the axial direction.
2B or 42A, 42B, and are connected to the output shafts 24, 44 in the linear drive members so that the rotation of the linear drive members is transmitted, but can be moved relative to the linear drive members in the axial direction. It is also possible to provide the rotary motion members 23 and 43, and provide a one-way rotation conversion mechanism between the outer frame and the pair of linear drive members.

That is, the outer frames 21, 41 and the surface of one of the pair of linear drive members 22A, 22B or 42A, 42B are alternately inclined in the opposite direction to the generatrix and connected to each other at the ends. Endless groove 3
2A, 32B or 52A, 52B, and a projection 3 elastically pressed against the groove on the other member.
2A, 32B or 52A, 52B is provided, and a groove selecting mechanism for selecting a groove sequentially adjacent to the protrusion with a change in the drive direction of the linear drive member near the groove end between the groove and the protrusion. And the ends of each row of the endless grooves are connected by a circumferential groove. The operation in this case is substantially the same as the above-described case, and thus the description thereof is omitted.

In the above-described embodiment, the structure of the groove selection mechanism for sequentially selecting the grooves adjacent to the projection is illustrated. However, the groove selection mechanism is not limited to this example. What is necessary is just to select the groove so that the child can output continuous one-way rotation with respect to the output shaft. Further, in the above embodiment, while one of the linear driving members is being driven to rotate in one direction, it is possible to rotate between the other linear driving member and the rotary motion member. Although the ends of each row of the grooves in the conversion mechanism are connected by the circumferential grooves, the linear drive member and the rotary motion member can be rotatable by any structure without such a structure. Further, the above-described linear drive member is not limited to a pair for forward rotation and reverse rotation, but may be any number necessary for giving continuous forward and reverse rotation to the output shaft.

[0039]

As described in detail above, according to the present invention, a stepping actuator which can be rotated stepwise in any direction in a forward or reverse direction by a fixed angle is used, and compared with the case where a servomotor is used. Demonstrates high thrust without using a speed reducer, high holding torque without using a brake, and accurate driving by simple sequence control compared to driving a stepping motor by open loop control Thus, it is possible to obtain a linear actuator that can control the output member linearly and stepwise by using a small, simple, and inexpensive device with large thrust.

In the stepping actuator used in the present invention, it is easy and easy to detect the position of the linear driving member by using a sensor.
Moreover, since positioning can be performed by the number of pulses from a control device such as a sequencer, not only the drive control is easy, but also it is possible to confirm that the operation of the linear drive member has been reliably performed. Can be controlled.

[Brief description of the drawings]

FIG. 1 is a plan view showing an embodiment of a linear actuator according to the present invention.

FIG. 2 is a sectional view showing an example of a stepping actuator used in the linear actuator of FIG.

FIG. 3 is a transverse sectional view taken along line AA in FIG. 2;

FIG. 4 is a developed view showing a groove shape on a surface of a rotating member in the stepping actuator of FIG. 2;

FIG. 5B shows another example of the stepping actuator used in the linear actuator of FIG. 1;
It is sectional drawing in the -B line.

FIG. 6 is a developed view showing a groove shape on the surface of the rotary motion member in the stepping actuator of FIG. 5;

FIG. 7 is a schematic plan view of a conventional linear actuator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Airframe 12 Stepping actuator 14 Ball screw 16 Output member 21, 41 Outer frame 22A, 22B, 42A, 42B Linear drive member 23, 43 Rotary movement member 24, 44 Output shaft 32A, 32B, 52A, 52B Groove 33A, 33B, 53A, 53B Protrusion 37A, 37B, 57A, 57B Circumferential groove 36A, 36B Step

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F15B 15/06 F15B 15/14

Claims (4)

(57) [Claims] A ball screw rotatably connected to an output shaft of a stepping actuator is rotatably supported on a body of the vehicle, and the ball screw is screwed onto the ball screw on the body and guided in an axial direction of the ball screw. The stepping actuator is mounted on the outer frame.
Positive that is held non-rotatably and driven independently in the axial direction
A pair of linear drive members for rotation and reverse rotation are provided, and the linear drive members are connected to the output shaft in the linear drive members.
A rotational movement member whose direction of movement is restricted, and one of the pair of linear drive members and the rotational movement member between the pair of linear drive members and the rotational movement member .
When the surface of the member is provided with an endless groove that is alternately inclined in the opposite direction with respect to the generatrix, and is connected to each other at the ends.
Both are elastically pressed against the other member against the groove.
Provide a protrusion, between the groove and the protrusion, near the groove end
As the drive direction of the linear drive member changes,
Equipped with a groove selection mechanism to select adjacent grooves, endless
The ends of each row of the above-mentioned grooves are connected by circumferential grooves
And, a linear actuator that these were constructed one-way rotation conversion mechanism for converting the axial movement of the respective linear drive member in successive steps rotational forward and reverse rotational movement member, characterized in that . 2. An output shaft which is rotatably supported on the body by being connected to an output shaft of a stepping actuator and is rotatably driven, and which is screwed onto the ball screw and guided in the axial direction on the body. The stepping actuator includes a pair of linear drive members for normal rotation and reverse rotation that are rotatably held by the outer frame and are independently driven in the axial direction, and the stepping actuator is provided in the linear drive members. , Connected to the above output shaft and going straight
The rotation of the driving member is transmitted, but the shaft is
A rotary motion member that is relatively movable in the
Between the frame and the pair of rectilinear driving members, one of the member surfaces is provided with an endless groove which is alternately inclined in the opposite direction with respect to the generatrix and is connected to each other at an end portion. The member is provided with a protrusion that elastically presses against the groove, and between the groove and the protrusion, a groove sequentially adjacent to the protrusion with a change in the driving direction of the linear drive member near the groove end. A groove selecting mechanism for selecting the end of each row of the endless grooves is connected to each other by a circumferential groove. A linear actuator, comprising a one-way rotation conversion mechanism for converting the rotation into a forward and reverse continuous step rotation. 3. A linear actuator according to claim 1 , wherein
In the estimator, it is adjacent to the protruding part as the driving direction of the linear driving member changes.
A groove selecting mechanism for selecting a groove to be moved,
When the protrusion moves toward the groove end with the drive of
By providing a step to deepen the return groove when returning from the end
Configuration was, linear actuator, characterized in that Ri. 4. The linear actuator according to claim 1 , wherein said stepping actuator is used for normal rotation and reverse rotation.
For driving a pair of linear driving members in the axial direction
The outer frame is a fluid pressure cylinder,
Driving pairs of linear drive members independently with fluid pressure acting on them
A linear actuator, characterized in that the piston is moved.