JPH09229092A - Air cylinder control circuit - Google Patents

Abstract

The present invention relates to an air cylinder control circuit for a connecting / disconnecting mechanism that performs a boost drive by air pressure, and makes it possible to reliably perform the connecting / disconnecting operation while reducing manufacturing costs. SOLUTION: An air pressure source 7, a first air chamber 20 for operating a piston 17 in one direction, a second air chamber 18 and a second air chamber for operating the piston 17 in a direction opposite to the one direction. A power cylinder 11 having an exhaust valve 43 for opening the working air in 18 to the outside, and the working air is interposed between the air pressure source 7 and the first air chamber 20.
To the solenoid valve 3 and the solenoid valve 3 interposed between the air pressure source 7 and the relay valve 5.
A discharge port 3A capable of discharging the working air supplied to the relay valve 5 is formed at the discharge port 3A and the second air chamber 1
It is configured to provide a communication passage d that communicates with

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air cylinder control circuit in a connecting / disconnecting mechanism such as a clutch booster, a brake, a shift control cylinder for a transmission, an intermittent clutch for power take-off, etc.

In recent years, for large vehicles such as buses and trucks and medium-sized vehicles, full automatic transmissions and semi-automatic transmissions have been proposed as automatic transmissions that automatically perform gear shifting operations in order to reduce the burden on the driver of gear shifting operations. ， Has been developed. In the case of passenger cars, light trucks, light buses, and the like, such automatic transmissions have mainly adopted torque converters instead of clutches, but in large and medium-sized vehicles such as buses and trucks. However, the amount of transmission of the driving torque is large and the load on the torque converter becomes excessive.

Therefore, the large and medium-sized vehicles as described above are provided with a clutch mechanism similar to that of a manual transmission.
A mechanism that automatically connects and disconnects the clutch is provided, and a semi-automatic transmission that eliminates the need for clutch operation during gear shifting operation, a mechanism that automatically engages and disengages the clutch, and a mechanism that automatically performs gear shifting are provided. A fully automatic transmission has been developed that operates automatically.

In such a vehicle, a drive mechanism using fluid pressure has been developed as a mechanism for automatically connecting and disconnecting the clutch. Further, Japanese Utility Model Laid-Open No. 5-96561 discloses a vehicle booster device as shown in FIG. 6 as one of such vehicle booster devices. 5 is a diagram schematically showing the air circuit of the booster shown in FIG.

Here, referring to FIGS. 5 and 6,
This booster is provided with a power cylinder 11 having a power piston 17 driven by compressed air. The power cylinder 11 includes solenoid valves 3 and 4 (in FIG. 5, solenoid valve 4 is omitted). The compressed air is supplied and discharged at a predetermined time. An air tank 7 is provided in the air supply circuit of the power cylinder 11, and air (hereinafter referred to as “pressurized air”) pressurized to a relatively high pressure by an air compressor (not shown) or the like is accumulated.

Further, in the air supply circuit to the power cylinder 11, there is provided a pressure adjusting valve (reducing valve) 2 for depressurizing the pressurized air in the air tank 7 to an arbitrarily set pressure and sending it out as instructed pressure air. A relay valve 5 and the like for supplying the pressurized air in the air tank 7 to the power cylinder 11 based on the instructed pressure air from the pressure adjusting valve 2 are provided.

Here, the power cylinder 11 is divided into a first air chamber 20 and a second air chamber 18 as shown in the figure, and when the relay valve 5 is driven, the power cylinder 11 is separated from the first air chamber 20. The air tank 7 is connected to the first air chamber 20.
Is supplied with pressurized air. Therefore, when a clutch disengagement signal is output from the controller (not shown) to the solenoid valves 3 and 4, the solenoid valves 3 and 4 are driven and pressurized air is supplied via the relay valve 5 to the first air chamber of the power cylinder 11. 20
Supplied to As a result, the power piston 17 is driven in the direction of disengaging the clutch of the vehicle.

When the power piston 17 is driven back, the power piston 17 is driven back in the clutch engagement direction by a return spring 19 provided in the second air chamber 18. At this time, since the operation is such that the volume of the second air chamber 18 increases, it is conceivable that the pressure in the second air chamber 18 decreases and the return drive of the power piston 17 is hindered.

Therefore, by supplying air of a predetermined pressure to the second air chamber 18 and applying auxiliary pressure, the high pressure first air chamber 20 is quickly contracted, and the power piston 1
Control is performed such that 7 is quickly returned and driven. That is, as shown in FIGS. 5 and 6, when the clutch engagement signal is output to the solenoid valve 3, the instruction pressure to the relay valve 5 is released to the atmosphere via the solenoid valve 3, and the relay valve 5 is opened to the first position. The first air chamber 20 and the air tank 7 are shut off, and the first air chamber 20 and the second air chamber 18 are communicated with each other.

As a result, the exhaust air from the inside of the first air chamber 20 is supplied to the second air chamber 18 via the relay valve 5, and the back pressure of the power piston 17 is greatly increased to increase the power. A quick return drive of the piston 17 is performed.

[0011]

However, such a conventional vehicle booster device has the following problems. That is, as shown in FIG. 6, the power cylinder 1
1, an oil chamber 24 is provided, and the second air chamber 18 and the oil chamber 24 are provided adjacent to each other via an oil seal or the like. As a result, when the pressure in the second air chamber 18 increases, air may mix with the hydraulic oil in the oil chamber 24.

Further, when the air is mixed in the oil chamber 24 as described above, it is conceivable that the drive amount of the rod 25 becomes smaller than the desired state due to the compressibility of the air and the desired clutch engagement / disengagement cannot be performed. Therefore, in order to prevent the pressure in the second air chamber 18 from increasing more than necessary, check valves 43 and 44 are provided in the second air chamber 18, and
The check valves 45 and 46 may be provided in the pipe 42, but in order to release the high-pressure air in the first air chamber 20, it is necessary to provide many check valves as described above, which raises the manufacturing cost. There is.

Further, if one check valve is used to open such high-pressure air to the atmosphere, it is necessary to increase the passage area up to the check valve, which causes a problem that the degree of freedom in layout of each part is reduced. Incidentally, Japanese Utility Model Laid-Open No. 6-8056 discloses a technique relating to clutch connection, but this does not refer to a technique for assisting return drive, and solves the problem to be solved by the present application. is not.

The present invention was devised in view of the above-mentioned problems, and an object thereof is to provide an air cylinder control circuit capable of reliably performing a connecting / disconnecting operation while reducing manufacturing costs. To do.

[0015]

Therefore, in the air cylinder control circuit of the present invention according to claim 1, an air pressure source for supplying working air and a piston in one direction when the working air is supplied. And a second air chamber for operating the piston in a direction opposite to the one direction when the first air chamber for operating the first air chamber and the operating air for supplying the operating air are supplied to the second air chamber. A power cylinder having an exhaust valve that selectively opens to the outside, and an operating air from the air pressure source, which is interposed between the air pressure source and the first air chamber, is pressurized at a predetermined rate. A relay valve that selectively supplies the first air chamber, and an electromagnetic valve that is interposed between the air pressure source and the relay valve and that selectively supplies operating air from the air pressure source to the relay valve. In the air cylinder control circuit equipped with a valve, the relay is connected to the solenoid valve. Outlet capable of discharging the working air supplied to the valve is formed, communicating passage for communicating the exhaust outlet and the second air chamber is characterized by being provided.

[0016]

DETAILED DESCRIPTION OF THE INVENTION An air cylinder control circuit as an embodiment of the present invention will be described below with reference to FIGS. This air cylinder control circuit is provided in a vehicle equipped with a so-called semi-automatic transmission, and is configured so that the clutch mechanism can be automatically controlled to be engaged or disengaged or the driver can intentionally control the engagement or disengagement. There is.

As shown in FIGS. 1 and 2, the present apparatus includes a power piston (piston) 1 driven by compressed air.
7 is provided with a power cylinder 11, and the power cylinder 11 includes a solenoid valve (magnet valve) 3
By the operation of the relay valve 5 and compressed air is supplied and discharged at a predetermined time. Further, the air supply circuit is provided with an air tank 7 as an air pressure source for accumulating the working air, a pressure adjusting valve 2 for depressurizing the air pressure of the air tank 7 and sending out instruction pressure air through an air pipe g. There is.

The solenoid valve 3 is switched by the input of a clutch control signal from the controller 9, and is configured to control the supply / discharge of compressed air to / from the power cylinder 11 when required. That is, the air pipe g is connected to the input side of the solenoid valve 3 and the air pipe c is connected to the output side, and the air pipe g and the air pipe c are connected by switching the solenoid valve 3. In this case, the output from the pressure regulating valve 2 is configured to act as an instruction pressure for the relay valve 5.

The relay valve 5 supplies the pressurized air in the air tank 7 to the air piping b, based on the indicated pressure from the pressure regulating valve 2 inputted via the solenoid valve 3 and the air piping c.
It is configured to supply to the first air chamber 20 of the power cylinder 11 through the air pipe f. Further, the first air chamber 20 in the power cylinder 11 is configured to drive the power piston 17 in the disengagement direction of the clutch 50 (rightward in FIG. 1) of the vehicle by the supply of operating air from the relay valve 5. There is.

On the other hand, as shown in FIGS. 1 and 2, a return spring 19 is internally provided in the second air chamber 18 of the power cylinder 11.
The urging force of 9 drives the power piston 17 to return to the contact direction of the clutch 50. Further, the second air chamber 18 is provided with return drive auxiliary air supply means S for supplying instruction pressure air as return drive auxiliary air to the second air chamber 18 in order to speed up the return drive of the power piston 17. Has been.

This return drive auxiliary air supply means S has an air pipe (communication passage) d whose upstream end is connected to the exhaust port (exhaust port) 3A of the solenoid valve 3, and this air pipe d
The downstream end of the second through the opening 54 of the power cylinder 11.
Is connected to the air chamber 18. Therefore, when the air pipe c and the air pipe d are connected for communication, the air acting on the relay valve 5 is supplied to the second air chamber 18 via the exhaust port 3A of the solenoid valve 3.

Here, the air pressure in the air pipe c, that is, the indicated pressure of the relay valve 5 is, for example, atmospheric pressure +0.1 to 0.
When the indicated pressure is about 2 kg / cm ² and is supplied to the second air chamber 18, it acts as a back pressure when the power piston 17 is driven in the return direction, and the drive by the return spring 19 is further increased. It is configured to be energized to assist the return drive.

Further, in the second air chamber 18, a check valve for selectively opening the air supplied to the second air chamber 18 to the outside in order to adjust the supplied instruction pressure air to a predetermined pressure state. (Exhaust valve) 43 is equipped. Therefore, the exhaust air of the first air chamber 20 is used as the auxiliary air for the second air.
In the conventional technology of supplying the air to the air chamber 18 of the above, since the air pressure is too high, air may be mixed into the hydraulic oil in the adjacent oil chamber 24. By supplying the second pressure air having a relatively low pressure to the second air chamber 18 by the air supply means S, it is possible to reliably prevent the air from being mixed into the hydraulic oil and to appropriately adjust the pressure by the small check valve 43. Therefore, the present apparatus can be realized with inexpensive equipment. This also gives
The check valve 43 provided in the power cylinder 11 can be downsized and the number of check valves 43 used can be reduced, while maintaining the responsiveness of the clutch connection.
The cost can be reduced.

The clutch 50 has an automatic adjustment function for automatically adjusting the position where the clutch 50 is joined or disengaged (stroke amount of the power piston 17) due to wear of the clutch plate or the like. The above-mentioned oil chamber 24 is provided for automatically adjusting the clutch 50. Further, this automatic adjustment function is a well-known technique in the related art, and therefore its explanation is omitted here.

Now, the above-described structure for automatically connecting and disconnecting the clutch 50, the structure for connecting and disconnecting the clutch by the normal manual operation of the clutch pedal 41 is as follows. That is, as shown in FIG. 1, the clutch pedal 41 is connected to the master cylinder 61, and when the driver depresses the clutch pedal 41, the hydraulic pressure (hydraulic pressure) in the master cylinder 61 corresponding to the depression amount of the clutch pedal 41 is changed. ) Is to occur.

The hydraulic pressure generated in the master cylinder 61 is input to the power cylinder 11 through the hydraulic pipes C and B. Hydraulic pipe C here
Is connected to the oil chamber 32 through a pipe B, and the operating hydraulic pressure is supplied to the oil chamber 32. further,
When hydraulic oil is supplied to the oil chamber 32, the push rod 62
The pressure acts on the drive rod 62 and the driving force of the push rod 62 is transmitted to the power piston 17.

The master cylinder 61 is connected to a relay valve 58 via a pipe A, and the relay valve 58 is driven when hydraulic pressure is generated in the master cylinder 61. When the relay valve 58 is driven by depressing the clutch pedal 41 of the driver, the air pipe i and the air pipe a are communicatively connected, and the pressurized air from the air tank 7 is supplied to the air pipe i, the air pipe a,
The power is supplied to the first air chamber 20 of the power cylinder 11 via the double check valve 8a and the air pipe f. The backflow of air at this time is prevented by the double check valve 8a.

On the other hand, an air pipe e is connected to the relay valve 58. The downstream end of the air pipe e is connected to the second air chamber 18, and when the power piston 17 is driven back, the air in the air pipe a is transferred to the second air chamber 1.
It is configured so that it can be supplied to the inside. That is, when the driver depresses the clutch pedal 41, the hydraulic pressure in the pipe A decreases and the relay valve 58 returns to the normal state. At this time, the relay valve 58 cuts off the communication between the air pipe i and the air pipe a, and simultaneously connects the air pipe a and the air pipe e.

The air pipes d and e are configured to supply air to the second air chamber 18 through the port 54. The downstream end of the air pipe f is connected to the port 55, and the air passing through the double check valves 8 and 8 a is configured to be supplied to the first air chamber 20 via the port 55. FIG. 3 is a cross-sectional view showing a specific configuration of the booster body 60 of the present apparatus, and in FIG. 3, components having the same reference numerals as those in FIGS. 1 and 2 are the same components.

The booster body 60, as shown in FIG.
The power cylinder 11 and the relay valve 58 are integrally configured, and the control hydraulic pressure from the master cylinder 61 is supplied to the oil chamber 32 via the port 56 and the pipe B provided at the left end in the figure. Further, the pipe A is connected to the relay valve 58 through the oil chamber 32. When the hydraulic oil is supplied through the pipe A, the piston member 63 is driven to disconnect the air pipe a and the air pipe e, and the air pipe a and the air pipe i are connected for communication.

When air is supplied to the first air chamber 20, the power piston 17 moves the return spring 19
Driven against, the hydraulic pressure is generated at the tip of the power piston 17, and the rod 25 is driven by this hydraulic pressure. Although the air pipe d is not shown in this cross-sectional view, the phase of the air pipe d with respect to the air pipe i is about 90 ° around the central axis of the piston member 63.
It is provided at a shifted position.

The relay valve 5 is constructed, for example, as shown in FIG. That is, in the upper part of the relay valve 5 in the drawing, an air chamber 5A to which the instruction pressure air is supplied through the air pipe c is provided, and when the instruction pressure air is supplied, the piston 5B moves downward in the figure. It is designed to be driven. Further, the output side air chamber 5 is provided in the middle part in the figure.
C is formed and the air pipe b is connected. Further, an input side air chamber 5D is formed in the lower part of the drawing, and the air pipe h
Is connected.

Further, on the inner peripheral side of the input side air chamber 5D,
The cylindrical slider 5E is fitted and inserted into the slider 5E.
Of the valve seat 5 formed at the lower end of the output side air chamber 5C
The input side air chamber 5D is closed by contacting G. The lower portion of the piston 5B is configured to be able to contact the slider 5E, and when the piston 5B is driven downward by a predetermined amount or more, the piston 5B and slider 5E contact and the slider 5E moves downward. It is supposed to do.

Further, when the piston 5B is driven upward, a gap 5H is formed between the lower end edge of the piston 5B and the casing forming the output side air chamber 5C. The output side air chamber 5C is configured to communicate with the atmosphere opening portion 5F via the gap 5H. Since the relay valve 5 is configured as described above, the output side air chamber 5C normally has the gap 5H.
To the atmosphere opening portion 5F, and the air pipe b is open to the atmosphere.

The input side air chamber 5D has a slider 5E.
Since the upper end of the valve seat and the valve seat 5G are in contact with each other, the air pipe h is in a closed state and the air pipe h is in a dead end state. Then, when the instruction pressure air is supplied to the air chamber 5A, the piston 5B is driven downward in the drawing. At this time, piston 5B
When the lower end of the slider 5E contacts the upper end of the slider 5E and is driven further downward, the contact state between the upper end of the slider 5E and the valve seat 5G is released, and the output side air chamber 5C and the input side air chamber 5 are released.
The communication with D is established.

As a result, the air pipe h and the air pipe b are connected, and the air in the air tank 7 is supplied to the first air chamber 20. Since the air cylinder control circuit as one embodiment of the present invention is configured as described above, it operates as follows, for example. First, when the controller 9 outputs a clutch control signal for performing the clutch disengagement operation, the solenoid valve 3 is switched, and the air pipe g and the air pipe c are in a communication connection state. As a result, the instruction pressure air reduced to a predetermined pressure by the pressure adjusting valve 2 is input to the relay valve 5 via the air pipe c.

In the relay valve 5, when the command pressure air is supplied, the relay valve 5 is driven by the command pressure to connect the air pipe h and the air pipe b so that the air in the air tank 7 becomes air pipes h, b ,. It is supplied to the first air chamber 20 through f. As a result, the power piston 17 of the power cylinder 11 is driven to the right in the figure, and the clutch 50 is disengaged.

On the other hand, when the controller 9 outputs a clutch control signal for performing the clutch engagement operation, the solenoid valve 3 is switched in the opposite manner to the above, and the air pipe g
The connection state between the air pipe c and the air pipe c is released, and the state is changed to the state where the air pipe c and the air pipe d are connected. Therefore,
The supply of the instructed pressure air to the relay valve 5 is stopped, whereby the connection state between the air pipe b and the air pipe h is released, and the air supply from the air tank 7 to the first air chamber 20 is stopped. The air pipe b is open to the atmosphere.

As a result, the pressurization of the first air chamber 20 is stopped, and the driving of the power piston 17 in the breaking direction is stopped. In this state, the power piston 17 has
The urging force of the return spring 19 in the second air chamber 18 acts to start driving the power piston 17 in the contact direction (return direction).

Then, in the second air chamber 18, the return drive assisting operation by the return drive assisting air supply means S is performed. That is, by connecting the air pipe c and the air pipe d, the instruction pressure air acting on the relay valve 5 is supplied to the second air chamber 18 via the exhaust port 3A of the solenoid valve 3. .

As a result, the command pressure air of the relay valve 5 acts as a back pressure on the power piston 17, and an auxiliary operation is performed for the drive of the power piston 17 by the return spring 19. At this time, the second
The pressure in the air chamber 18 does not become a negative pressure but becomes a relatively low positive pressure state, and the power piston 17 is quickly driven in the returning direction without hindering the operation of the return spring 19.

Further, with respect to an excessive positive pressure, the inside of the second air chamber 18 is adjusted to an appropriate pressure by exhausting air by the check valve 43. This reliably prevents air from entering the oil chamber 24 adjacent to the power piston 17. When the clutch disengagement operation is performed artificially by depressing the clutch pedal 41 of the driver, the following operation is performed.

First, when the hydraulic pressure generated by the depression of the clutch pedal 41 is input to the power cylinder 11 through the hydraulic pipe C, the relay valve 5 is passed through the hydraulic pipe A.
The state where the instruction pressure is input to 8 is set. As a result, the relay valve 58 is switched, and the air pipe i and the air pipe a are communicated and connected. Then, the pressurized air in the air tank 7 is fed through the air pipes i, a, f to the first
Is supplied to the air chamber 20 and the power piston 17 is driven in the breaking direction.

On the other hand, when the clutch pedal 41 is released, the supply of the indicated pressure to the relay valve 58 through the hydraulic pipes C and A is released, and the relay valve 58 is switched. As a result, the connection between the air pipe i and the air pipe a is released, and the air pipe e and the air pipe a are connected. Therefore, the air supply from the air tank 7 to the first air chamber 20 is stopped.

Further, by connecting the air pipe e and the air pipe a, the pressure in the air pipe a is supplied to the second air chamber 18, and the auxiliary operation for the return drive of the power piston 17 is performed. Therefore, in the prior art in which the exhaust air from the first air chamber 20 side is supplied to the second air chamber 18 as auxiliary air, the air pressure supplied to the second air chamber 18 is too high, so There is a possibility that air may be mixed into the hydraulic oil in the oil chamber 24, but like the present device, it is provided with the return drive auxiliary air supply means S and the instruction pressure air of the relay valve 5 is used as the auxiliary air. With the configuration in which the air is supplied to the air chamber 18, the auxiliary air pressure is not too large, and it is possible to reliably prevent air from being mixed into the hydraulic oil. Further, since the pressure inside the second air chamber 18 can be appropriately adjusted by the small check valve 43, it is possible to prevent air mixing with inexpensive equipment.

Further, as a result, it is possible to reliably avoid a state in which the driving amount of the rod 25 becomes smaller than the desired state due to the mixing of air and the desired clutch engagement / disengagement becomes impossible. Further, in the case where the check valve 43 is stuck or clogged for some reason by supplying a relatively low pressure air, that is, the air under the pressure of the relay valve 5, to the second air chamber 18. Also, the power cylinder 11 can be operated smoothly.

Further, it is not necessary to equip a large number of check valves, and the above-mentioned operation can be realized at a low manufacturing cost. Further, with one check valve, the pressure inside the second air chamber 18 can be adjusted to an optimum pressure with an appropriate passage area, and the manufacturing cost can be suppressed. In addition, in the present embodiment, the case where the present device is applied to the clutch booster for performing the clutch connecting / disconnecting operation has been described, but the present device is not limited to the application of such a clutch booster, and the boosting force is increased by the air pressure. The present invention can be widely applied to a braking device for driving, a shift control cylinder for a transmission, an on / off mechanism such as an on / off clutch for power take-off.

[0048]

As described in detail above, according to the air cylinder control circuit of the present invention, by supplying the second air chamber with the relatively low pressure indicating pressure air through the communication passage, Since it is possible to reliably prevent air from entering and to appropriately adjust the pressure with a small exhaust valve, it is possible to realize the present device with inexpensive equipment. Further, as a result, the exhaust valve provided in the power cylinder can be downsized, the number of exhaust valves used can be reduced, and the cost can be reduced while maintaining the responsiveness of the clutch connection. is there. Further, one exhaust valve can adjust the pressure in the second air chamber to an optimum pressure with an appropriate passage area, which has the advantage of increasing the degree of freedom in layout of the check valve and other components. Further, by supplying a relatively low pressure air, that is, the air under the pressure of the relay valve, to the second air chamber, even if the exhaust valve is stuck or is clogged for some reason, The cylinder can be operated smoothly.

[Brief description of drawings]

FIG. 1 is a schematic overall view showing an air cylinder control circuit as an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a main part of an air cylinder control circuit according to an embodiment of the present invention.

FIG. 3 is a schematic cross-sectional view showing a specific configuration of an air cylinder control circuit as an embodiment of the present invention.

FIG. 4 is a schematic cross-sectional view showing the structure of a relay valve of an air cylinder control circuit according to an embodiment of the present invention.

FIG. 5 is a pneumatic circuit diagram schematically showing a configuration of a main part of a conventional vehicle booster device.

FIG. 6 is a cross-sectional view schematically showing a hardware configuration of a main part of a conventional vehicle booster device.

[Explanation of symbols]

 2 Pressure control valve (Reducing valve) 3 Solenoid valve (Magnet valve) 3A Exhaust port as exhaust port 4 Solenoid valve (Magnet valve) 5 Relay valve 5A Air chamber 5B Piston 5C Output side air chamber 5D Input side air chamber 5E Slider 5F Atmosphere opening part 5G Valve seat 5H Gap 7 Air tank as air pressure source 8,8a Double check valve 9 Controller 11 Power cylinder 17 Power piston (piston) 18 Second air chamber 19 Return spring 20 First air chamber 24 Oil chamber 25 Rod 32 Oil chamber 41 Clutch pedal 42 Piping 43 Check valve as exhaust valve 50 Clutch 54 to 56 port 58 Relay valve 60 Booster body 61 Master cylinder 62 Push rod 63 Piston member S Return drive auxiliary air supply means a to i Air piping as communication passage

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Koji Kondo 5-3-8, Shiba, Minato-ku, Tokyo Mitsubishi Motors Corporation

Claims (1)

[Claims] 1. An air pressure source for supplying operating air, a first air chamber for operating the piston in one direction when the operating air is supplied, and a piston which operates when the operating air is supplied. A power cylinder having a second air chamber that operates in a direction opposite to the one direction and an exhaust valve that selectively releases the operating air supplied to the second air chamber to the outside; A relay valve interposed between the air pressure source and the first air chamber, the relay air pressure-increasing the working air from the air pressure source at a predetermined ratio to selectively supply the operating air to the first air chamber; In an air cylinder control circuit having a solenoid valve interposed between the relay valve and the solenoid valve for selectively supplying the working air from the air pressure source to the relay valve, the solenoid valve is supplied to the relay valve. A discharge port capable of discharging the working air Characterized in that a communication passage which communicates the second air chamber is provided, an air cylinder control circuit.