JP2003049805A - Rack and pinion-type rotary actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rack and pinion-type rotary actuator having superior durability and reliability and having high positioning accuracy at intermediate stop. SOLUTION: An intermediate stopping mechanism 31 comprises a first pressing member 34, a second pressing member 35 and a stopper part 33. The first pressing member 34 is located on a position approximately coaxial with the first rack and piston 5 in a first piston storing chamber 3, and can be advanced and retracted to the first rack and piston 5. The second pressing member 35 is located on a position approximately coaxial with a second rack and piston 6 in a second piston storing chamber 4, and can be advanced and retracted to the second rack and piston 6. The stopper parts 33 on which the pressing members 34, 35 advanced toward the rack pistons 5, 6 side are abutted, are respectively formed on inner wall faces of both piston storing chambers 3, 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rack and pinion type rotary actuator which can be stopped at three positions, that is, an intermediate stop.

[0002]

2. Description of the Related Art Conventionally, various types of rotary actuators called a rack and pinion type have been proposed. This type of rotary actuator includes an actuator body in which first and second piston accommodating chambers are formed. A rotating shaft is supported in a region between the pair of piston accommodating chambers in the actuator body. The first and second rack pistons are slidably accommodated in the pair of piston accommodating chambers, respectively. A rack is provided on the outer peripheral surfaces of the pair of rack pistons, and a pinion is provided on the outer peripheral surfaces of the rotating shaft. The rack and the pinion are in a meshing relationship. Therefore, when pressurized air is supplied to and discharged from the pressure action chamber defined by each rack piston, both rack pistons reciprocate in opposite directions, and the reciprocating motion causes the pivot shaft to pivot within a predetermined angle range. It is supposed to do.

By the way, in this type of rotary actuator, the rotary shaft is configured to stop only at both ends of the rotary motion, in other words, only at two positions. Therefore, there has conventionally been a demand for intermediately stopping the rotation shaft at an arbitrary angle other than the rotation end. As a specific method therefor, for example, another actuator having a stopper pin is driven by using a solenoid valve, and the stopper pin is engaged with the rotating shaft to move the rotating shaft at an intermediate position. It is possible to prevent it.

[0004]

However, in the above method, it is not possible to expect high position accuracy at the time of intermediate stop, and moreover, a sequence operation is required, which causes a loss of operation time. was there.

It is also possible to use a servomotor in place of the rack and pinion type rotary actuator to realize a rotating operation including an intermediate stop. In this case, high position accuracy can be expected at the time of intermediate stop. However, since the servo motor is expensive, there is a problem that the cost of the entire system increases.

Therefore, in recent years, a rack and pinion type rotary actuator having an intermediate stop mechanism has been proposed. The intermediate stop mechanism in this actuator is configured to include one common centering piston that simultaneously presses a pair of rack pistons from the same direction.

However, since a part of the outer peripheral portion of the centering piston abuts only a part of the outer peripheral portion of the rack piston, the area in which the two abut each other is very small, and the shaft of the rack piston is small. A shock is applied to a position away from the heart. Therefore, the torque that can be held is small, and there is a problem in durability and reliability. In addition, there has been a considerable demand for an intermediate stop mechanism capable of achieving higher positional accuracy.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a rack and pinion type rotary actuator having excellent durability and reliability and having extremely high intermediate stop position accuracy. .

[0009]

In order to solve the above-mentioned problems, in the invention described in claim 1, the first and second internal parts are provided.
An actuator body in which piston accommodating chambers are formed, first and second rack pistons accommodated in the pair of piston accommodating chambers and reciprocating in opposite directions, and a rack provided in the pair of rack pistons An intermediate stop mechanism having a rotating shaft provided with a pinion that engages with each other and a pressing member that intermediately stops the rotating shaft at any angle other than the rotation end angle by pressing both rack pistons substantially at the same time. In the rotary actuator including, the intermediate stop mechanism is disposed at a position substantially coaxial with the first rack piston in the first piston accommodating chamber, and is capable of advancing and retracting with respect to the first rack piston. A member and a second rack piston that is disposed substantially coaxially with the second rack piston in the second piston accommodating chamber. A second pressing member capable of advancing and retracting with respect to the ton and a stopper portion provided on the inner wall surface of each of the piston housing chambers, with which the pressing member that has advanced toward the rack piston abuts. A rack-and-pinion type rotary actuator is used.

According to a second aspect of the present invention, in the first aspect, the first pressing member is provided with the first pressure member by the action of fluid pressure.
The second centering piston is a first centering piston that advances toward the rack piston side, and the second pressing member is a second centering piston that advances toward the second rack piston side by the action of fluid pressure.

According to a third aspect of the present invention, in the second aspect, the rack piston is arranged in a small diameter portion in the piston accommodating chamber, and the centering piston is arranged in a large diameter portion in the piston accommodating chamber. A step portion with which the outer peripheral portion of the centering piston abuts is formed at the boundary between the portion and the large diameter portion.

According to a fourth aspect of the present invention, in the third aspect, the actuator body communicates with either one of the large-diameter portion and the communication passage that connects the large-diameter portions of the piston accommodating chamber. A fluid supply / discharge port for centering is formed.

The "action" of the present invention will be described below. According to the first aspect of the present invention, the first and second pressing members move forward to press both rack pistons substantially at the same time, so that both rack pistons stop at a predetermined position in the stroke. Therefore, the rotation shaft can be intermediately stopped at any angle other than the rotation end angle. Further, in the present invention, since the pressing members are arranged substantially coaxially with the rack piston in the individual piston accommodating chambers, the area where the rack piston and the pressing member contact each other is relatively large. Moreover, since the pressing member presses the position close to the shaft center of the rack piston, it is possible to prevent the impact from being applied to the position away from the shaft center.
As a result, the torque that can be held at the time of contact increases,
It also improves durability and reliability. Further, the movement of the pressing member is reliably regulated by contact with the stopper portions provided on the inner wall surfaces of the piston housing chambers. Therefore, extremely high positional accuracy can be ensured at the time of intermediate stop.

According to the second aspect of the present invention, since the drive source of the rack piston and the drive source of the centering piston can be made common, the actuator can be driven only by the action of fluid pressure. Further, according to this structure, the centering piston can be driven when necessary and not driven by supplying and discharging the fluid. Therefore, unlike the configuration in which the pressing force always acts on the rack piston, the loss of output torque is prevented.

According to the third aspect of the present invention, the centering piston advances due to the supply of the fluid, and the central portion of the front end surface thereof presses the rack piston. At this time, the outer peripheral portion of the front end surface of the centering piston comes into contact with a step portion formed at the boundary between the small diameter portion and the large diameter portion, and as a result, the movement of the centering piston is restricted. Further, with such a configuration, the assembly becomes relatively easy, which is convenient for cost reduction. Moreover, since the centering piston has a larger diameter than the rack piston, a relatively large effective pressure receiving area is secured in the centering piston. Therefore, a sufficient pressing force can be applied to both rack pistons, and both rack pistons can be reliably stopped at predetermined positions.

According to the fourth aspect of the present invention, when the fluid is supplied through the fluid supply / discharge port for centering, the fluid is introduced into the large diameter portions of both piston accommodating chambers almost simultaneously through the communication passage, Fluid pressure acts on both centering pistons. Therefore, both centering pistons can be advanced substantially simultaneously and both rack pistons can be pressed simultaneously. Further, according to this configuration, it is not necessary to provide the ports at two places, so the structure of the actuator is simplified.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION A rack and pinion type rotary actuator according to an embodiment of the present invention will be described below with reference to FIG.
~ It will be described in detail with reference to FIG.

As shown in FIGS. 1 and 2, the rotary actuator 1 of this embodiment is composed of a flat rectangular parallelepiped aluminum alloy actuator body 2. The actuator body 2 is composed of a main housing 2a having a hollow portion, and a first end cover 2b and a second end cover 2c provided to close both ends of the main housing 2a. Inside the actuator body 2, a first piston housing chamber 3 and a second piston housing chamber 4 are provided.
Are formed respectively. Both the piston accommodating chambers 3 and 4 are spaces having a circular cross section, and are formed parallel to each other in a state of extending along the longitudinal direction of the actuator body 2. A first rack piston 5 is housed in the first piston housing chamber 3 so as to be capable of reciprocating along the longitudinal direction of the actuator body 2. In the second piston accommodating chamber 4,
The second rack piston 6 is housed so as to be capable of reciprocating along the longitudinal direction of the actuator body 2. A rack 5 extending along the axial direction of the rack pistons 5 and 6 is provided in a predetermined region on the outer peripheral surface of the rack pistons 5 and 6.
a and 6a are engraved respectively. Further, rubber-shaped and annular piston packings 7 are attached to the outer peripheral surfaces of both rack pistons 5 and 6 at positions on both ends of the racks 5a and 6a. In this embodiment, the rack pistons 5 and 6 are made of stainless steel.

As shown in FIGS. 1 and 2, the actuator body 2 is provided with a shaft insertion hole 12 for inserting a shaft 11 as a rotating shaft. The shaft insertion hole 12 is formed so as to penetrate the central portion of the actuator body 2 in the thickness direction (vertical direction in FIG. 2). In other words, the shaft insertion hole 1
2 is formed so as to penetrate the region between the pair of piston accommodating chambers 3 and 4 along the thickness direction of the actuator body 2. That is, in the actuator 1 of the present embodiment, the direction in which the shaft 11 extends and both rack pistons 5,
The reciprocating directions of 6 are orthogonal to each other.

The rack 5 is provided on one end side of the shaft 11.
A pinion 13 having a pitch capable of meshing with a and 6a is fixed to the shaft 11 so as to rotate integrally therewith. The end of the shaft 11 on the side where the pinion 13 is fixed (non-projecting side end) is inserted into the shaft insertion hole 12 of the actuator body 2. At this time, the shaft 11 is pivotally supported by a pair of ball bearings 14 arranged on both upper and lower sides of the pinion 13. Racks 5a and 6a of both rack pistons 5 and 6
The pinion 13 and the pinion 13 are in mesh with each other.

An end of the shaft 11 on the side where the pinion 13 is not fixed is projected from the upper surface of the actuator body 2 to the outside. A jig or a work (not shown), which is a driven object, is attached to the end of the shaft axis 11 on the protruding side. In this embodiment, the shaft 11 is made of stainless steel.

As shown in FIG. 1, the first rack piston 5 divides the first piston housing chamber 3 into two regions. For convenience, the space formed on the first end cover 2b side is referred to as "first end cover side pressure action area A1", and the space formed on the second end cover 2c side is referred to as "second end cover side pressure action area A2". ". Similarly, the second rack piston 6 also divides the second piston accommodating chamber 4 into two regions. For convenience, the space formed on the first end cover 2b side is referred to as a "first end cover side pressure acting area A3", and the space formed on the second end cover 2c side is referred to as a "second
It is referred to as an end cover side pressure acting area A4 ".

Fluid supply / discharge ports 15, 16, 17, and 18 are provided at a plurality of locations in the actuator body 2. More specifically, the first fluid supply / discharge port 15 is formed on the side surface of the main housing 2a so as to communicate with the first end cover side pressure acting area A1. The second fluid supply / discharge port 16 is formed on the side surface of the main housing 2a so as to communicate with the second end cover side pressure acting area A2. The third fluid supply / discharge port 17 is formed on the side surface of the main housing 2a so as to communicate with the first end cover side pressure acting area A3. The fourth fluid supply / discharge port 18 is formed on the side surface of the main housing 2a so as to communicate with the second end cover side pressure acting area A4.

The first fluid supply / discharge port 15 and the fourth fluid supply / discharge port 18 are connected to a first common pipe 21, and the first common pipe 21 is connected to a fluid supply source via a solenoid valve 22. It is connected to 23. In this embodiment, an air compressor that supplies compressed and pressurized air is used as the fluid supply source 23 (pressurized air supply source). A 6-port 3-position switching valve as shown in FIG. 1 is used as the solenoid valve 22. Such an electromagnetic valve 22 is electrically connected to a sequencer (not shown), and its drive is controlled by a command from the sequencer.

The second fluid supply / discharge port 16 and the third fluid supply / discharge port 17 are connected to the second common pipe 24, and the second common pipe 24 supplies the fluid via the solenoid valve 22. Connected to the source 23. The solenoid valve 22
A so-called speed controller composed of a throttle valve and a check valve may be installed on the common pipes 21 and 24 on the secondary side. Further, a muffler may be connected to a port on the primary side of the solenoid valve 22 that is not connected to the fluid supply source 23 to prevent noise.

As shown in FIG. 1, stroke adjusting bolts 27 are provided at two locations on the first end cover 2b.
Is attached. One end of these bolts 27
It projects into the first end cover side pressure acting areas A1, A3, and the other end projects outside the actuator body 2. A nut 28 is screwed onto the bolt 27. The amount of protrusion of the bolt 27 into the first end cover side pressure acting area A1, A3 can be adjusted by changing the screwing degree of the nut 28. By individually adjusting the protrusion amount in this manner, the rack pistons 5,
The stroke end positions of 6 can be changed respectively. As a result, the rotation end angle of the shaft 11 can be adjusted arbitrarily.

Next, the intermediate stop mechanism 31 provided in the actuator 1 of this embodiment will be described. The intermediate stop mechanism 31 has a structure in which the shaft 11 is intermediately stopped at an arbitrary angle other than the turning end angle by pressing both rack pistons 5 and 6 almost simultaneously by the pressing member. The intermediate stop mechanism 31 of the present embodiment is characterized in that it has not only one pressing member but two pressing members.

As shown in FIG. 1, the second end cover 2c is formed to be slightly thicker than the first end cover 2b, and a pair of concave portions 32 having a circular cross section is formed inside the second end cover 2c. . One of these recesses 32 constitutes a part of the first piston accommodating chamber 3 and the second piston accommodating chamber 4
Form part of the. A portion of the first piston accommodating chamber 3 on the second end cover 2c side (that is, the recess 32) is set to have a larger inner diameter than a portion of the first piston accommodating chamber 3 on the main housing 2a side. In other words, the first piston housing chamber 3 has the small diameter portion 3a and the large diameter portion 3b. Similarly, a portion of the second piston accommodating chamber 4 on the second end cover 2c side (that is, the recess 3).
In 2), the inner diameter is set to be larger than that of the portion of the second piston housing chamber 4 on the main housing 2a side. In other words, the second piston housing chamber 4 also has the small diameter portion 4a and the large diameter portion 4b. And the small diameter portion 3
A stepped portion 33 is formed at both the boundary between a and the large diameter portion 3b and the boundary between the small diameter portion 4a and the large diameter portion 4b. It can be understood that the step portion 33 is provided on the inner wall surface of each of the piston housing chambers 3 and 4. In addition, such a stepped portion 33 functions as a stopper portion with which the pressing member that has advanced toward the rack pistons 5 and 6 comes into contact. The step portion 33 in the present embodiment has an annular shape and is formed over the entire circumferential direction of the piston housing chambers 3, 4. The size of the step portion 33 is set to about 1 mm to several mm.

In the large diameter portion 3b of the first piston accommodating chamber 3, the first centering piston 3 as a first pressing member is provided.
4 is slidably accommodated. The disk-shaped first centering piston 34 of the present embodiment has a shorter length along the axial direction and a slightly larger diameter than the first rack piston 5. The first centering piston 34 is
It is arranged coaxially with the first rack piston 5 in the first piston housing chamber 3. A piston packing 34a is attached to the outer peripheral surface of the first centering piston 34.

In the large diameter portion 4b of the second piston accommodating chamber 4, the second centering piston 3 as the second pressing member is provided.
5 is slidably accommodated. The disc-shaped second centering piston 35 of the present embodiment has a shorter length along the axial direction and a slightly larger diameter than the second rack piston 6. The second centering piston 35 is
It is arranged coaxially with the second rack piston 6 in the second piston accommodating chamber 4. A piston packing 35a is attached to the outer peripheral surface of the second centering piston 35.

In the case of this embodiment, the stroke lengths of the first and second centering pistons 34 and 35 are equal to the first stroke.
And shorter than the stroke length of the second rack pistons 5 and 6.

As shown in FIG. 1, the second end cover 2c is formed with a communication passage 36 that connects the large diameter portions 3b and 4b of both piston housing chambers 3 and 4.
Further, the second end cover 2c is provided with a centering fluid supply / discharge port 37 that communicates with the large diameter portion 4b of the second piston housing chamber 4. The solenoid valve 22 is connected to the fluid supply / discharge port 37 via a pipe 38.

Now, the operation of the rotary actuator 1 thus constructed will be described with reference to FIG. First,
The solenoid valve 22 is driven to supply the pressurized air only to the second fluid supply / discharge port 16 and the third fluid supply / discharge port 17. Then, pressurized air is introduced into each of the pressure acting areas A2 and A3, and the air pressure acts on the right end side surface of the first rack piston 5 and the left end side surface of the second rack piston 6. As a result, after the first rack piston 5 moves to the left and the second rack piston 6 moves to the right, both of them stop at the positions shown in FIG. At this time,
The shaft 11 rotates counterclockwise in FIG. 3A and then stops at a predetermined rotation end angle.

Next, the solenoid valve 22 is switched to supply the pressurized air only to the first fluid supply / discharge port 15 and the fourth fluid supply / discharge port 18. Then, each pressure acting area A
1, pressurized air is introduced into A1 and air pressure acts on the left end side surface of the first rack piston 5 and the right end side surface of the second rack piston 6. As a result, the first rack piston 5 moves to the right and the second rack piston 6 moves to the left, and then both stop at the positions shown in FIG. 3C. At this time, the shaft 11 rotates clockwise in FIG. 3C and then stops at a predetermined rotation end angle.

Further, a case where the intermediate stop is performed from this state will be described. In this case, switch the solenoid valve 22,
The pressurized air is supplied only to the fluid supply / discharge port 37 for centering. Then, the pressurized air is introduced into the large diameter portion 4b of the second piston housing chamber 4, and the pressurized air is introduced into the large diameter portion 3b of the first piston housing chamber 3 via the communication passage 36. As a result, air pressure acts on the right end surface side of both centering pistons 34, 35, and both move simultaneously to the left.

In this case, the first centering piston 34
On the left end face side of the first rack piston 5 before the start of movement.
The right end face of is already in contact. Therefore, the first centering piston 34 moves integrally with the first rack piston 5 toward the left while maintaining contact with the first rack piston 5. After that, the outer peripheral portion of the first centering piston 34 contacts the stopper portion (that is, the step portion 33) provided on the inner wall surface of the first piston housing chamber 3. As a result of such contact, the further movement of the first centering piston 34 is restricted, and the first centering piston 3
4 stops at that position.

On the other hand, when the movement is started, the left end surface of the second centering piston 35 and the right end surface of the second rack piston 6 are separated from each other. Therefore, the second centering piston 35 moves leftward. In other words, the second
The centering piston 35 advances toward the second rack piston 6 side, and eventually contacts the right end surface of the second rack piston 6. Further, the outer peripheral portion of the second centering piston 35 abuts on the stopper portion (that is, the step portion 33) provided on the inner wall surface of the second piston housing chamber 4. As a result of such contact, further movement of the second centering piston 35 is restricted, and the second centering piston 35 stops at that position.

As a result of the above, the rotary actuator 1 is brought into a state as shown in FIG. 3 (b), and the shaft 11 is made to stop intermediately at an angle just between the two turning end angles.

Therefore, according to this embodiment, the following effects can be obtained. (1) The rotary actuator 1 employs the intermediate stop mechanism 31 having the above structure. That is, the first centering piston 34 that can advance and retreat with respect to the first rack piston 5 is provided at a position coaxial with the first rack piston 5 in the first piston accommodating chamber 4. A second centering piston 35 that can move forward and backward with respect to the second rack piston 6 is provided at a position coaxial with the second rack piston 6 in the second piston accommodating chamber 4. Then, step portions 33 as stopper portions are provided on the inner wall surfaces of both piston accommodating chambers 3 and 4, respectively.

Therefore, both centering pistons 34,
35 moves forward and presses both rack pistons 5 and 6 almost simultaneously, so that both rack pistons 5 and 6 stop at a predetermined position in the stroke. Therefore, the shaft 11 can be intermediately stopped at any angle other than the turning end angle.

In this embodiment, the centering pistons 34 and 35 are arranged coaxially with the rack pistons 5 and 6 in the individual piston accommodating chambers 3 and 4. Therefore, the area where the rack pistons 5 and 6 and the centering pistons 34 and 35 contact each other is relatively large. Moreover, since the centering pistons 34 and 35 press the positions close to the shaft centers of the rack pistons 5 and 6, it is possible to prevent the impact from being applied to the positions apart from the shaft centers. As a result, the torque that can be held at the time of contact is increased, and durability and reliability are improved as compared with the conventional device.

Further, the centering pistons 34, 35
The movement of is reliably regulated by contact with the step portion 33 provided on the inner wall surfaces of the piston housing chambers 3 and 4. Therefore, extremely high positional accuracy can be ensured at the time of intermediate stop.

(2) In the case of the intermediate stop mechanism 31 of the present embodiment, the intermediate stop can be realized relatively easily without performing complicated sequence control. Therefore, unlike an intermediate stop mechanism of a type in which another pin-locking actuator is driven by a solenoid valve to engage the pin with the rotary shaft, no loss of operating time occurs. Further, since the intermediate stop is not realized by using an expensive servo motor, it is possible to avoid the cost increase of the entire system.

(3) In this embodiment, the first centering piston 34, which advances toward the first rack piston 5 side by the action of air pressure, is used as the first pressing member. Further, similarly, the second centering piston 35 that advances toward the second rack piston 6 side by the action of the air pressure is also provided.
Is used as the second pressing member.

Therefore, since the drive sources of the rack pistons 5 and 6 and the drive sources of the centering pistons 34 and 35 can be made common, the actuator 1 can be driven only by the action of air pressure. Further, according to this structure, the centering pistons 34 and 35 can be driven when necessary and not driven by supplying and discharging the pressurized air. Therefore, unlike the configuration in which the pressing force always acts on the rack pistons 5 and 6, the occurrence of output torque loss is prevented. That is, the shaft 11 can be efficiently driven without wasting energy.

(4) In this embodiment, both centering pistons 34 and 35 are arranged in the large diameter portions 3b and 4b of the piston accommodating chambers 3 and 4, respectively. Also, the small diameter portion 3
a step portion 3 formed at a boundary between a and 4a and large diameter portions 3b and 4b
3, the outer peripheral portions of both centering pistons 34, 35 are configured to abut. Therefore, the centering pistons 34 and 35 are moved forward by the supply of the pressurized air, and the center portions of the front end surfaces thereof press the rack pistons 5 and 6. At this time, the outer periphery of the front end faces of the centering pistons 34, 35 (the outer periphery of the left end face in FIG. 3C) is the step portion 33.
With respect to each other, and as a result, the movements of the centering pistons 34 and 35 are restricted.

Further, with such a structure, the assembling becomes relatively easy. That is, the centering piston 3
4, 35 and rack pistons 5, 6 are accommodated,
The second end cover 2c may be attached to the main housing 2a. At that time, a step portion 33 is also formed at a joint portion between the main housing 2a and the second end cover 2c.
Therefore, it can be said that this configuration is convenient for cost reduction.

Moreover, the centering pistons 34, 35
Has a larger diameter than the rack pistons 5 and 6. Therefore, a relatively large pressure receiving area is secured in the centering pistons 34, 35. Therefore, the centering pistons 34, 35 can apply a sufficient pressing force to both the rack pistons 5, 6, and the both rack pistons 5, 6 can be reliably stopped at predetermined positions. As a result, the shaft 11 can be reliably stopped in the middle at a predetermined angle.

(5) This rotary actuator 1 is
The piston accommodating chambers 3 and 4 are provided with a communication passage 36 that connects the large diameter portions 3b and 4b to each other, and a centering fluid supply / discharge port 37 that communicates with the large diameter portion 4b. Therefore, if pressurized air is supplied through the fluid supply / discharge port 37,
Pressurized air is introduced into both large-diameter portions 3b and 4b at substantially the same time via the communication passage 36, and both centering pistons 34,
Air pressure acts on 35. Therefore, both the centering pistons 34 and 35 can be advanced substantially at the same time and both rack pistons 5 and 6 can be pressed simultaneously. Also,
According to this configuration, it is not necessary to provide the ports 37 at two places, so that the structure of the actuator 1 can be simplified.

(6) Both centering pistons 34, 35
The stroke length of is set to be shorter than the stroke length of both rack pistons 5 and 6. Therefore, even if the intermediate stop mechanism 31 is provided at the end of the main housing 2a, the size of the device does not significantly increase in the longitudinal direction as a whole.

The embodiment of the present invention may be modified as follows. In the intermediate stop mechanism 41 of another example shown in FIG. 4, a pressing member of a type different from that of the embodiment is used. That is, here, the first and second centering pistons 3
4, 35 instead of the pair of centering plates 42,
43 is used. First centering plate 4
2 is housed in the large-diameter portion 3b together with the coil spring 44 as the urging means. The second centering plate 43 is housed in the large-diameter portion 4b together with the coil spring 44 as a biasing means. Therefore, the centering plates 42 and 43 are always subjected to the urging force toward the right side in FIG. When it is desired to make an intermediate stop in the apparatus configured as described above, the supply of the pressurized air to each of the ports 15 to 18 is stopped. Then, the coil springs 44 in the compressed arrangement state try to return to their original lengths, and as a result, the centering plates 42 and 43 move leftward in FIG.

In the case of the intermediate stop mechanism 41 having such a structure, it is not necessary to supply and discharge the air pressure to drive the intermediate stop mechanism 41, so that the solenoid valve 22 having a simpler structure can be used. There is.

In the above another example, the coil spring 4
For example, rubber or the like may be used as the biasing means in place of 4. The stroke adjusting bolt 27 and the nut 28 are not essential components and may be omitted.

The axial centers of the first centering piston 34 and the first rack piston 5 do not necessarily have to be exactly the same as in the embodiment, but may be slightly decentered. The same applies to the second centering piston 35 and the second rack piston 6.

The stopper portion does not have to have the outer peripheral portions of the centering pistons 34 and 35 abutting over the entire circumference as in the embodiment, and may have a structure in which only a part thereof abuts. Good.

・ The stopper is composed of both piston storage chambers 3,
It may be configured not only by being provided on a part of the inner wall surface of No. 4 but also by attaching a member different from the actuator body 2 to the inner wall surface.

The rack and pinion type rotary actuator 1 of the present invention can be embodied not only as a drive source using air pressure but also as a drive source using hydraulic pressure.

Next, in addition to the technical ideas described in the claims, the technical ideas grasped by the above-mentioned embodiment will be listed below together with their effects. (1) In any one of claims 1 to 4, the centering piston has a diameter equal to or larger than that of the rack piston. Therefore, according to the invention described in this technical idea 2, since a relatively large effective pressure receiving area is secured in the centering piston, it is possible to apply a sufficient pressing force to the rack piston.
Therefore, both rack pistons can be reliably stopped at the predetermined positions.

[0059]

As described above in detail, according to the first aspect of the present invention, it is possible to provide a rack and pinion type rotary actuator which is excellent in durability and reliability and which has extremely high intermediate stop position accuracy. it can.

According to the second aspect of the invention, the actuator can be efficiently driven by using one type of drive source. According to the invention as set forth in claim 3, it is possible to provide the one excellent in the assembling property, the cost property and the position accuracy of the intermediate stop.

[Brief description of drawings]

FIG. 1 is a sectional view of a rack and pinion type rotary actuator according to an embodiment of the present invention.

FIG. 2 is a partial cross-sectional view of the actuator.

3A is a cross-sectional view of the shaft at a clockwise end angle, FIG. 3B is a cross-sectional view of an intermediate stop, and FIG. 3C is a shaft at a counterclockwise end angle. Sectional drawing of a state.

FIG. 4 is a sectional view of a rack and pinion type rotary actuator of another example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Rack and pinion type rotary actuator, 2 ... Actuator main body, 3 ... 1st piston accommodating chamber, 3a, 4
a ... small diameter part, 3b, 4b ... large diameter part, 4 ... second piston accommodating chamber, 5 ... first rack piston, 5a, 6a ... rack,
6 ... 2nd rack piston, 11 ... Shaft as a rotating shaft, 13 ... Pinion, 31, 41 ... Intermediate stop mechanism, 33
... stepped portion as stopper portion, 34 ... first centering piston as first pressing member, 35 ... second centering piston as second pressing member, 36 ... communicating passage, 37
… Fluid supply / drain ports for centering.

Claims (4)

[Claims] 1. An actuator body having first and second piston accommodating chambers formed therein, and first and second rack pistons accommodated in the pair of piston accommodating chambers and reciprocating in opposite directions. And a rotation shaft provided with a pinion that engages with racks provided on the pair of rack pistons, and the rotation shafts by pressing both rack pistons substantially at the same time to rotate the rotation shafts at any angle other than the rotation end angle. A rotary actuator having an intermediate stop mechanism having a pressing member for intermediate stop at the intermediate stop mechanism, the intermediate stop mechanism being disposed substantially coaxially with the first rack piston in the first piston accommodating chamber. A first pressing member capable of advancing and retracting with respect to one rack piston, and substantially coaxial with the second rack piston in the second piston accommodating chamber And a second pressing member that is disposed in a stationary position and is movable back and forth with respect to the second rack piston, and the pressing members that are respectively provided on the inner wall surfaces of the piston housing chambers and that have moved forward toward the rack piston side come into contact with each other. A rack and pinion type rotary actuator comprising: a stopper portion. 2. The first pressing member is a first centering piston that advances toward the first rack piston side by the action of fluid pressure, and the second pressing member is the second centering piston by the action of fluid pressure. The rack and pinion type rotary actuator according to claim 1, wherein the rack and pinion type rotary actuator is a second centering piston that advances toward the rack piston side. 3. The rack piston is arranged in a small diameter portion in the piston housing chamber, the centering piston is arranged in a large diameter portion in the piston housing chamber, and a boundary between the small diameter portion and the large diameter portion is The rack-and-pinion type rotary actuator according to claim 2, wherein a stepped portion with which an outer peripheral portion of the centering piston abuts is formed. 4. The actuator body is provided with a communication passage that connects large diameter portions of the piston housing chamber, and a centering fluid supply / discharge port that communicates with any one of the large diameter portions. The rack and pinion type rotary actuator according to claim 3, wherein: