JP2001020908A - Rotary actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotary actuator capable of providing high output at a low speed in spite of limiting the peripheral length. SOLUTION: A rocking plate 24 provided with N pieces of first tooth 23 is arranged at the tip of the fixed shaft 10 provided in a fixed base 13 through a universal joint 20, and a rotary plate 40 provided with M (however, M<N) pieces of second tooth 41 capable of meshing with the first teeth 23 is arranged opposing to the rocking plate 24. A proper number of rocking motion generating means 30 are arranged on the fixed base 13, and the rocking motion generating means 30 are made to cyclically repeat rocking motions over a range of 360 deg. so that the meshing positions of the first teeth 23 and the second teeth 41 formed in the rotary plate 40 are continuously displaced relative to the rocking plate 24. One rocking cyclic of the rocking plate 24 over a range of 360 deg. cause the rotary plate 40 to rotate the quantity of the difference between N, the number of the first teeth 23 and M, the number of the second teeth 41. A rotary plates 40 and a cylinder 39 are rotated at a substantially reduced rotation speed by continuously rocking the rocking plate 24.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary actuator, and more particularly to a rotary actuator suitable for obtaining low speed and high output.

[0002]

2. Description of the Related Art Various types of rotary actuators are known according to the purpose of use, such as an electric motor or a turbine motor or a vane motor driven by a fluid. These conventional rotary actuators generally have a high rotation speed, and when used as actuators that require relatively slow movement like a robot,
A combination with a speed reducer was required, resulting in a large overall volume.

As an actuator driven by a fluid and suitable for relatively low-speed operation, FIGS.
b, a rubber wobble generator 100,
A metal wobble ring 115 having an internal gear, an external gear 114 meshing with the internal gear of the wobble ring 115, an output shaft 106 fixed to the external gear 114, members 103, 112, 104 constituting a motor casing, and the output shaft Bearings 113a, 11 supporting rotation of 106
3b and the like are known as wobble motors (Japanese Patent Laid-Open No. 10-78010).
And Japanese Patent Application Laid-Open No. 11-93612).

In the wobble motor described above, the inner peripheral surface of the wobble generator 100 and the outer peripheral surface of the wobble ring 115 are bonded, and the number of teeth of the internal gear of the wobble ring 115 is larger than the number of teeth of the external gear 114. At the same time, a gap exists between the internal gear and the external gear 114 of the wobble ring 115 in the non-driven state. Inside the wobble generator 100, an appropriate number of spaces 102a, 102b, 102c,.
102f is formed in the circumferential direction, and each pressure chamber is connected to an appropriate pneumatic source via tubes 105a, 105b,..., 105f, respectively. Then, by appropriately opening and closing an electromagnetic valve (not shown) interposed in each tube, each of the pressure chambers 102a, 102b,.
The internal pressure of 02f is sequentially increased, whereby the wobble ring 115 revolves and the output shaft 106 rotates.

That is, in the illustrated wobble motor, when the inner peripheral surface of the wobble generator 100 is deformed in the radial direction by pressurization, the wobble ring 115 is also moved in the radial direction accordingly (FIG. Is also not pressurized). Here, for example, the pressure chamber 1
When 02f is pressurized, the pressure chamber 102f expands and the wobble ring 115 is pushed downward in the figure, and the internal gear formed on the inner peripheral surface of the wobble ring 115 comes into contact with the external gear 114 fixed to the output shaft 106. Mesh. When each pressure chamber is sequentially pressurized, the wobble ring 115 performs a so-called orbital motion. Here, as described above, since the number of teeth is different between the external gear 114 and the internal gear formed on the wobble ring 115, the wobble ring 115 With the revolution of 115, the meshing of the two gears shifts, and the output shaft 106 rotates. The rotation angle (rotation speed) depends on the difference between the number of teeth of the internal gear and the external gear and the revolving speed of the wobble ring 115. The speed can be very low. Therefore, there is an advantage that a small actuator can be easily obtained.
In a state where none of the pressure chambers is pressurized, the output shaft 1
06 can be set in a free rotation state, while maintaining only a specific pressure chamber in a pressurized state can be set in a braking state, and high operability as an actuator can be expected.

[0006]

The wobble motor of the above-mentioned type is inconvenient for the air motor, that is, it is supposed to be used at a high speed rotation although it is small, and is required to be used at a high torque and a low speed. The inconvenience of separately providing a speed reducer externally has been solved by providing a speed reduction mechanism in the mechanism of the motor itself. It enables use at high torque and low rotation while maintaining. However, the wobble motor of the above type is suitable only for a small motor due to its mechanism, and since the rubber wobble generator functions as one of the members receiving a rotational reaction force in the circumferential direction, the rubber (elastic) It is difficult to generate a large torque with a large wobble motor having a large diameter because the shear force that can be generated by the body is limited.

[0007] Instead of a rubber wobble generator, a ring having an internal gear is used, and three or more air pistons whose operating direction is a radial direction (radial direction) are arranged on the outer peripheral surface of the ring. By operating it sequentially,
Similar rotary actuators capable of generating high torque (output) can be obtained, but arranging the air piston in the radial direction increases the size in the circumferential direction, and in any case from the ring that rolls by some means An additional mechanism for taking out the rotation around the fixed output shaft is required. The present invention
The present invention has been made in view of the above circumstances, and has as its object to provide a rotary actuator capable of simultaneously satisfying both low speed and high output while limiting the size in the circumferential direction.

[0008]

A rotary actuator according to the present invention for solving the above-mentioned problems is swingably supported at the tip of a fixed shaft provided on a fixed base via a universal joint, and An oscillating plate having first teeth having a number N of teeth formed concentrically about the axis of the fixed shaft;
A second tooth having a number M of teeth capable of meshing with the first tooth of the oscillating disk is disposed on the opposing surface in a state where the movement in the axial direction is prevented. (However, M ≠
N) a rotating plate provided concentrically with the axis of the fixed shaft as a center, and a meshing position between the first teeth of the rotating plate and the second teeth formed on the rotating plate. Oscillating motion generating means for generating a periodic oscillating motion over 360 degrees so that the oscillating plate is continuously displaced. Number of teeth N
And a rotational movement of a difference between the number of teeth M of the second teeth and the number of second teeth is caused on the rotating plate.

In the above structure, the meshing position between the first teeth and the second teeth formed on the rotary plate is continuously displaced with respect to the rocker plate by an appropriate rocking motion generating means. When a 360-degree oscillating motion is generated, the number N of the first teeth of the oscillating plate and the second
The rotational movement of the difference of the number of teeth M of the first tooth occurs on the rotating plate. By continuing the swinging motion of the swinging plate, the rotating plate rotates at a speed corresponding to the difference in the number of teeth and the swinging cycle speed of the swinging plate.

The radial dimension of the rotary actuator according to the present invention basically depends only on the diameters of the oscillating plate and the rotary plate, so that the size can be easily reduced and, if necessary, a large diameter. Can be designed, again,
Since the meshing teeth are located at positions near the outer circumferences of the rocking plate and the rotating plate, the maximum mechanically possible torque can be generated. Further, the output (rotation torque) essentially depends on the force of the first teeth formed on the rocking plate pressing the second teeth formed on the rotation plate, and further, the rotation reaction force is also supported. It can be performed by the fixed shaft and the universal joint attached to the tip of the fixed shaft, and since there is no elastic body as in the conventional case, the swinging motion generating means for generating the swinging motion on the swinging plate is provided. The output can be reliably transmitted to the rotating plate side with little loss, and a high-output (high torque), low-rotation rotary actuator can be easily obtained.

The oscillating motion generating means is arranged to rotate the oscillating plate periodically over 360 degrees so that the meshing position between the first teeth of the oscillating plate and the second teeth formed on the rotating plate is continuously displaced. There is no limitation as long as it can generate a dynamic movement.
The oscillating motion generating means is three or more linear motion mechanisms, for example, a fluid-driven piston / cylinder mechanism, which are arranged rotationally symmetrically with respect to the fixed axis between the fixed base and the oscillating plate. There is provided an operation mechanism that is sequence-controlled so that the linear motion mechanisms are activated in a predetermined order. The linear motion mechanism uses a direction parallel to the fixed axis of the rotary actuator as an operation direction, and does not affect the diameter dimension of the rotary actuator. The working fluid may be pumped air or liquid. The oscillating motion generating means may be a plurality of electromagnetic solenoids, in which case a sequence control mechanism for turning the solenoids on and off in a predetermined order is provided.

In the rotary actuator according to the present invention, the oscillating plate may be disposed only on one side surface of the rotating plate, and the same type of oscillating plate is mirror-symmetrical on both side surfaces of the rotating plate. It may be arranged in such a manner. In the latter case,
Naturally, the second teeth are equally formed on both side surfaces of the rotating plate. The first teeth of each of the two oscillating plates arranged mesh with the second teeth formed on both sides of the rotating plate, and the meshing points substantially oppose each other on both surfaces. By setting the position, it is possible to cancel the axial force acting on the rotating plate, and it is possible to increase the output and operate with less vibration.

The rotary actuator according to the present invention can be used in many ways. For example, the rotating plate may be used as a low-speed and high-output motor by attaching a gear to the rotating plate, or may be directly used as a driving wheel of a vehicle by attaching a cylindrical rim to the rotating plate and mounting a tire. You can also. The former case is suitable for use as an actuator of a robot arm or the like as air drive,
The latter case is suitable for use as a drive wheel of a watering car as a hydraulic drive.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of a rotary actuator according to the present invention will be described below with reference to the drawings. FIG. 1 shows a rotary actuator 1 according to the present invention.
Is a perspective view showing the entirety of FIG. 1, and FIG. 2 is a central sectional view thereof. In the figure, reference numeral 10 denotes a fixed shaft, which is fixed to a fixed machine frame (not shown) directly or via a fixed base 13 described later when the rotary actuator 1 is used. Fixed shaft 1
A cylindrical body 12 having a radial flange 11 is attached to the leading end of the cylindrical body 1 by appropriate means such as screwing.
2, the support shaft 21 of the universal joint 20 is press-fitted. That is, the intermediate ring 2 is attached to the tip of the support shaft 21 by the shaft 22a.
2 is rotatably supported, and the intermediate ring 22 is provided with a universal joint 20 of a conventionally known type which supports a swinging disk 24 by a shaft 25 so that the swinging disk 24 is fixed to the fixed shaft 10.
Is mounted so as to be able to swing in any direction about the axis of the shaft.

On one surface (the right surface in FIG. 1) of the oscillating disk 24, first teeth 23 having a number N of teeth (such teeth are generally called crown gears) are formed concentrically. The other surface is formed with a recess 26 for receiving a piston tip of a piston-cylinder mechanism described later. A fixed base 13 is fixed to the fixed shaft 10 by a screw 14.
The fixed base 13 is provided with four sets of fluid-driven piston / cylinder mechanisms 30... With their lines of action parallel to the axis of the fixed shaft 10. Note that the fixed shaft 10 and the fixed base 13 may be integrated. Each piston / cylinder mechanism 30 includes a cylinder 3
1, a piston 32 reciprocating in a cylinder 31, and a piston rod 33 having a cap 34 attached to the tip thereof. A spring 35 is interposed between the cap 34 and the front wall of the cylinder 31 in a compressed state. Have been. An air supply chamber 36 is provided on the rear wall of the cylinder 31, through which pressurized air from a not-shown compressed air source is supplied into the cylinder 31.

The four sets of piston / cylinder mechanisms 30 are of the same standard, and when no pressurized air is supplied,
The tip of each piston rod 33 is kept in constant contact with the back surface of the oscillating disk 24 at the same pressure by the force of the spring 35. As a result, as shown in FIG. It is held perpendicular to your heart. When the pressurized air is supplied, the piston 32 moves rightward in the figure, and the tip of the piston rod 33 further presses the swinging disk 24. Therefore, if the pressurized air is supplied to only one piston / cylinder mechanism 30 and only the piston / cylinder mechanism 30a located at a higher position in the drawing to be in an operating state, the swinging disk 24 is connected to the joint of the universal joint 20. With the part as a fulcrum, the upper part in the figure swings rightward and is inclined.

An inner race 38 of an annular bearing 37 capable of simultaneously supporting both a radial load and an axial load is fixed to the outer periphery of the fixed base 13 by appropriate means. A cylinder 39 is fixed to the outer race of the bearing 37 with the axis thereof being the same as the axis of the fixed shaft 10. This allows the cylinder 39 to freely rotate about the fixed shaft 10 as an axis, while preventing movement in the axial direction.

At the front end of the cylinder 39, as shown in FIG. 3, the number M of teeth that can mesh with the first teeth 23 formed on the oscillating disk 24 concentrically on one surface (however,
The ring-shaped rotary plate 40 on which the second teeth 41 satisfying M ≠ N (normally, M <N) is formed so as to be in a posture perpendicular to the axis of the fixed shaft 10, and may be screwed in as appropriate. It is fixed at. As shown in FIG. 2, the rotating plate 40 and the oscillating disk 24 are formed by first teeth 23 formed on the oscillating disk 24.
And the second teeth 41 formed on the rotating plate 40 are located at positions facing each other. A shielding plate 43 is fixed to the center of the rotating plate 40 by screws 44.

The operation of the rotary actuator 1 will be described. The operating principle of the rotary actuator 1 is as follows.
Basically, it is based on a deceleration mechanism by rolling motion,
A swinging disk 24 non-rotatably attached to the fixed shaft 10 via the universal joint 20 has a first tooth 23 formed concentrically on one side surface and the rotating plate 40 also concentrically. The first tooth 23 is provided on the rotating plate 40 side by generating a periodic swinging motion over 360 degrees so that the meshing position with the formed second tooth 41 can be continuously displaced. And the rotational movement of the difference between the number N of teeth of the second tooth 41 and the number M of teeth of the second tooth 41 is caused. Since the first tooth swings and meshes with the second tooth, the number N of the first teeth is generally larger than the number M of the second teeth, and N> M.

In the rotary actuator 1 described above, the oscillating motion of the oscillating disk 24 is performed by sequentially operating the four sets of piston / cylinder mechanisms 30 arranged on the back side of the oscillating disk 24. Occurs. FIG. 4 shows an example of a system configuration for sequentially operating the four sets of piston / cylinder mechanisms 30a to 30d. In this example, pressurized air from a compressed air source 60 is sent to a pipeline 51. , Pipeline 5
Each of the four branches has a normally closed 3-port solenoid valve 52a.
52d are interposed, and the ON / OFF of the electromagnetic valves 52a to 52d is sequence-controlled by a digital signal from the computer 70, whereby the piston / cylinder mechanisms 30a to 30d are sequentially operated with regularity. Like that. In FIG. 4, reference numeral 61 denotes a pressure gauge, 62 denotes a pressure regulating valve, and 71 denotes a display for control.

The state shown in FIG. 4 corresponds to the solenoid valves 52a to 52d.
Are turned off, no pressurized air is sent to the piston / cylinder mechanisms 30a to 30d, and each cylinder chamber is kept at atmospheric pressure. As shown in FIG. 2, in this state, the tip of each piston rod 33 is pressed against the back surface of the oscillating disk 24 with the same pressure by the force of the spring 35, and the oscillating disk 24 is With respect to the vertical.
In that position, the first teeth 23 and the second
The rotating plate 40 (and the cylinder 39) is in a free state in which the rotating plate 40 (and the cylinder 39) can freely rotate with respect to the fixed shaft 10 via the bearing 37.

When, for example, the solenoid valve 52a is excited by a signal from the computer 70, pressurized air is sent to the piston / cylinder mechanism 30a via the channel (1),
The piston 32 moves to the right in FIG. 2, and the upper part in FIG. 2 is tilted rightward with the swinging disk 24 as a fulcrum about the joint portion of the universal joint 20. Due to the inclination, the oscillating disk 2
4 is in a posture in which the first teeth 23 mesh with the second teeth 41 on the rotating plate 40 side. This state corresponds to the fixed shaft 1 of the rotating plate 40.
This is a state in which the relative rotation with respect to 0 is regulated by the meshing of the gears, and corresponds to a state in which a brake is applied.

In response to a signal from the computer 70, for example, counterclockwise in FIG. 4, that is, the solenoid valves 52a → 52
ON-OF of four solenoid valves in the order of b → 52c → 52d
Switch F. As a result, pressurized air is sequentially supplied to the four sets of piston / cylinder mechanisms in the order of 30a → 30b → 30c → 30d (in the order of channels (1) to (4)) and is released to the atmosphere. . As a result, the oscillating disk 24 generates a periodic oscillating motion over 360 degrees, and the second teeth formed on the first teeth 23 of the oscillating disk 24 and the rotating plate 40.
Meshing position with the teeth 41 is continuously displaced within a range of 360 degrees. Then, the number N of the first teeth 23 and the number of the second teeth 4
The number of teeth M of one is different, and the rotational movement of the difference occurs on the rotating plate 40 side. By causing the oscillating disk 24 to generate a periodic oscillating motion continuously, the rotating plate 40 is continuously driven to rotate, and functions as a rotary actuator.

For example, if the number of teeth N of the first teeth 23 is 77 and the number of teeth M of the second teeth 41 is 76, the difference in the number of teeth, that is, 2π / 77rad
Only the rotating plate 40 rotates. Therefore, the number of rotations per unit time can be obtained by multiplying the value by the oscillation frequency of the oscillation disk 24. Also, depending on whether the difference between the number N of the first teeth 23 and the number M of the second teeth 41 is positive or negative,
The direction of rotation is reversed.

FIG. 5 is an enlarged view showing the meshing portion between the first teeth 23 and the second teeth 41. In the rotary actuator 1 according to the present invention, since the two gears are engaged while being pressed, the shape of the teeth is different from a normal involute curve or the like, but is represented here as an isosceles triangle. Further, the magnitude of the force transmitted from the oscillating disk 24 to the rotating plate 40 changes depending on the pressure angle α. For example, if the oscillating disk 24 on the left side in the drawing is pressed by the force Fin, Has 1/2 Fsi in the rotation direction.
A force of n2α and a force of Fsin ² α are generated in the axial direction. Therefore, the pressure angle α may be selected according to the purpose of use. However, when the maximum torque is generated, α = π / 4r
ad.

In the above example, four sets of piston / cylinder mechanisms each having a normally closed 3-port solenoid valve are used as the means for generating the oscillating motion of the oscillating disk 24. However, this is merely an example. May be used. For example, in the case of a single-acting push-out cylinder as described above, the required two-degree-of-freedom swing cannot occur unless the number of cylinders is three or more. Any number of sets may be used.

When the four piston-cylinder mechanisms shown are used, as shown in FIG. 6A, only one piston-cylinder mechanism is sequentially pressurized to obtain four states (π / 2) equal to the number of cylinders. The swing may be performed for one cycle at (pitch), and as shown in FIG. 6b, the case where one cylinder is pressurized and the case where two cylinders are pressurized are repeated, and It may be made to swing for one cycle in the state (π / 4 pitch). When swinging every π / 4 rad, for example, 616 (77 (number of teeth) × 8)
In this state, the rotating plate 41 makes one rotation (2π rad). By utilizing this, the rotary actuator according to the present invention can be used as a stepping motor that rotates every π / 380 rad.

FIG. 7 shows an application of the rotary actuator 1 according to the present invention. Here, a rim 80 is attached to the cylindrical portion 39 of the rotary actuator 1 described above, and a tire 81 is attached thereto.
A plurality of drive mechanisms are prepared, and each fixed shaft 10
(Or the fixed base 13) to a vehicle frame (not shown).
By fixing the rotary actuator 1 (corresponding to a machine frame), a vehicle using the rotary actuator 1 directly as a driving wheel of the vehicle can be obtained. In this case, if water pressure is used instead of pressurized air as the driving fluid, for example, a part of the water flow for watering can be used as the driving force of the rotary actuator, so that it is effective as a driving wheel of a watering wheel. Available to

In the above description, the first teeth 23 formed on the oscillating disk 24 are formed on the surface opposite to the side where the fixed shaft 10 is located. That is, the first teeth 23 may be formed on the surface of the piston / cylinder mechanism 30 where the recess 26 for receiving the piston tip is formed. In that case, the annular rotating plate 40 is arranged such that its second teeth 41 can mesh with the first teeth 23 of the oscillating disk 24, and the piston / cylinder mechanism 30 is located. 1 (the left side of the oscillating disk 24 in FIG. 1). In this case, the first
The meshing position between the second tooth 41 and the second tooth 41 is a position axially symmetric with the piston / cylinder mechanism 30 to be operated. In this case, the same function as the rotary actuator is performed without any trouble.

FIG. 8 is a central sectional view showing another embodiment of the rotary actuator according to the present invention. Here, the second teeth 41, 41 are equally formed on both side surfaces of the rotating plate 40A, and the fixed shaft 10, the piston / cylinder mechanism 30 having the same configuration as described above are provided on both sides of the rotating plate 40A. , A driving mechanism such as a oscillating disk 24 is arranged so as to be mirror-symmetrical, and the left and right cylinders 3
9A and 39A are mounted.

The operation mode of the rotary actuator 1A is basically the same as that of the rotary actuator 1 described with reference to FIGS. 1 to 4, but each of the two rocking plates 24 arranged mirror-symmetrically. The first teeth 23 of the rotating plate 40
The sequence control by the computer 70 is performed such that the meshing points meshing with the second teeth 41 formed on both sides of A are positioned so as to be opposed to each other on both sides.
As a result, the axial force acting on the rotating plate 40A is offset, and the operation with less vibration can be performed with the increase in output.

FIG. 9 is a central sectional view showing still another embodiment of the rotary actuator according to the present invention. This rotary actuator 1B is the same as the rotary actuator 1A shown in FIG. 8, except that an annular rotary plate 40B is formed integrally with a common cylinder 39A and the common axis is the same. The driving mechanism such as the piston / cylinder mechanism 30 and the swinging disk 24 having substantially the same configuration as described above is mirror-symmetrical on both sides of the annular rotating plate 40B with respect to the fixed axis 10B. It is arranged so that it becomes. The operation mode of the rotary actuator 1B is basically the same as that of the rotary actuator 1A shown in FIG.
By using 0B, more stable operation can be expected. In each case, the output (torque) is determined by the supply pressure of the fluid, and the rotation speed is determined by the switching speed of the solenoid valve. Therefore, the torque and the rotation speed can be controlled independently. It can be used.

[0033]

As described above, according to the present invention,
A small-sized, low-rotation, high-output rotary actuator can be obtained. If necessary, it can be constructed as a large-sized, high-output one.

[Brief description of the drawings]

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

FIG. 2 is a central sectional view of the rotary actuator shown in FIG. 1;

FIG. 3 is a perspective view showing an example of a rotating plate.

FIG. 4 is a system diagram illustrating the operation principle of the rotary actuator according to the present invention.

FIG. 5 is a view for explaining a mode of engagement between a first tooth and a second tooth.

FIG. 6 is a view for explaining different pressurization patterns of four sets of piston and cylinder mechanisms.

FIG. 7 is a sectional view illustrating an example of use of a rotary actuator according to the present invention.

FIG. 8 is a central sectional view showing another embodiment of the rotary actuator according to the present invention.

FIG. 9 is a central sectional view showing still another embodiment of the rotary actuator according to the present invention.

FIG. 10 is a diagram illustrating a wobble motor as an example of a hydraulic drive actuator.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Rotary actuator, 10 ... Fixed shaft, 20 ... Universal joint, 24 ... Oscillating disk, 23 ... 1st tooth, 30 ... Piston / cylinder mechanism as oscillating motion generating means, 37 ...
Bearing, 39: cylinder, 40: rotating disk, 41: second
Teeth, 52 ... solenoid valve, 60 ... compressed air source, 70 ... computer

Claims (3)

[Claims] A first shaft having a first number of teeth N, which is swingably supported at the tip of a fixed shaft provided on a fixed base via a universal joint, and is formed concentrically about the axis of the fixed shaft. A oscillating plate provided with a first tooth of the oscillating disk, the first surface of the oscillating disk being engaged with the oscillating plate while being prevented from moving in the axial direction; Second teeth (M 歯)
N) is provided concentrically about the axis of the fixed shaft, and the meshing position between the first teeth and the second teeth formed on the rotating plate is relative to the swinging plate. Oscillating motion generating means for generating a periodic oscillating motion over 360 degrees so as to be continuously displaced, wherein the first tooth is formed by one oscillating cycle over 360 degrees of the oscillating plate. A rotational movement of the rotating plate, the rotational movement being a difference between the number N of teeth and the number M of second teeth. 2. The oscillating motion generating means includes three or more linear motion mechanisms disposed rotationally symmetrically with respect to a fixed axis between a fixed base and a oscillating plate, and operates the linear motion mechanisms in a predetermined order. 2. The rotary actuator according to claim 1, further comprising an operation mechanism that is sequence-controlled to perform the following. 3. The rotary actuator according to claim 2, wherein the linear motion mechanism is a fluid-driven piston / cylinder mechanism.