Gas cylinder

An air cylinder includes a cylinder, a piston rod, a piston, and a controller. The piston rod has one end disposed in the cylinder and the other end protruding from the cylinder. The piston is provided at the one end of the piston rod and moves the piston rod by moving in the cylinder. The controller supplies gas into one of a space, which is a space in the cylinder directed on the piston rod side with respect to the piston, and a space, which is a space in the cylinder opposite to the space with respect to the piston, and sucks gas from an interior of the other of the spaces.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based on and claims priority from Japanese Patent Application No. 2017-133812 filed on Jul. 7, 2017 with the Japan Patent Office, the disclosure of which is incorporated herein in its entirety by reference.

TECHNICAL FIELD

Various aspects and exemplary embodiments of the present disclosure relate to a gas cylinder.

BACKGROUND

An air cylinder, which uses air pressure as a power source, is used to provide power to various devices such as a robot arm. The air cylinder is also used for a semiconductor manufacturing device or a semiconductor transport device in order to provide power to various points. See, for example, Japanese Patent Application Laid-Open No. 2003-322109.

SUMMARY

One aspect of the present disclosure provides a gas cylinder including a cylinder, a piston rod, a piston, and a gas controller. The piston rod has one end disposed in the cylinder and the other end protruding from the cylinder. The piston is provided at the one end of the piston rod and moves the piston rod by moving in the cylinder. The gas controller supplies gas into one of a space, which is a space in the cylinder directed on the side of the piston rod with respect to the piston, and a space, which is a space in the cylinder opposite to the space with respect to the piston, and sucks gas from the interior of the other of the spaces.

DESCRIPTION OF EMBODIMENT

Recently, because of multi-functionality or operation complexity of the manufacturing device or the transport device, a plurality of driving devices are provided in the manufacturing device or the transport device. For this reason, the manufacturing device or the transport device tends to be increased in size, and thus there is a need for reduction in size of the device. To realize the reduction in size of the device, it is also important to reduce a size of the air cylinder. However, the reduction in size of the air cylinder causes a decrease in cross-sectional area of a piston and deterioration in thrust of the piston. Therefore, it is difficult to reduce the size of the air cylinder because necessary thrust needs to be ensured.

According to one exemplary embodiment, a disclosed gas cylinder has a cylinder, a piston rod, a piston, and a gas controller. The piston rod has one end disposed in the cylinder and the other end protruding from the cylinder. The piston is provided at one end of the piston rod and moves the piston rod by moving in the cylinder. The gas controller supplies compressed gas into one of a first space, which is a space in the cylinder at the side of the piston rod with respect to the piston, and a second space, which is a space in the cylinder opposite to the first space with respect to the piston, and sucks gas from an interior of the other of the first and second spaces.

According to one exemplary embodiment of the disclosed gas cylinder, a plurality of pistons may be further provided on the piston rod along the piston rod. In addition, partition walls, which divide third spaces surrounded by an inner wall of the cylinder and the two adjacent pistons in an extension direction of the piston rod, may be provided in the cylinder for every two adjacent pistons. In addition, in each of the third spaces, the first space may be a space in the cylinder at the side of one end of the piston rod with respect to the partition wall, and the second space may be a space in the cylinder at the side of the other end of the piston rod with respect to the partition wall.

According to one exemplary embodiment of the disclosed gas cylinder, the gas controller may suck the gas from the interior of the first space and may supply the compressed gas into the second space when the piston rod is moved in a direction in which the other end of the piston rod is moved away from the cylinder.

According to one exemplary embodiment of the disclosed gas cylinder, the gas controller may supply the compressed gas into the first space and may suck the gas from the interior of the second space when the piston rod is moved in a direction in which the other end of the piston rod is moved toward the cylinder.

According to one exemplary embodiment of the disclosed gas cylinder, the gas controller may suck the gas from the space in the cylinder using a vacuum pump.

According to one exemplary embodiment of the disclosed gas cylinder, the gas may be dry air.

According to one exemplary embodiment of the disclosed gas cylinder, a seal member is disposed between the cylinder and the piston rod.

According to one exemplary embodiment of the disclosed gas cylinder, a lubricant is applied on a surface of the outer circumference of the piston rod.

According to one exemplary embodiment, disclosed is a method of operating a gas cylinder including a cylinder, a piston rod having one end disposed in the cylinder and a remaining end protruding from the cylinder, a piston provided at the one end of the piston rod and configured to move the piston rod by moving inside the cylinder. The method includes: supplying a compressed gas into a first space, which is a space in the cylinder on a side of the piston rod with respect to the piston, and sucking gas from an interior of a second space, which is a space in the cylinder opposite to the first space with respect to the piston at the same time, thereby pressing out the piston rod; and supplying a compressed gas into the second space, and sucking gas from an interior of the first space at the same time, thereby pulling back the piston rod.

According to one exemplary embodiment, a disclosed gas cylinder has a cylinder, a piston rod, a plurality of pistons, one or more partition walls, and a gas controller. The piston rod has one end disposed in the cylinder and a remaining end protruding from the cylinder. The plurality of pistons are provided at the one end of the piston rod and at one or more positions between the one end and the remaining end of the piston rod, and are configured to move the piston rod by moving in the cylinder. Each of the one or more partition walls is provided in the cylinder for every two adjacent pistons so as to divide a space surrounded by an inner wall of the cylinder and the two adjacent pistons in an extension direction of the piston rod. The gas controller supplies supply a compressed gas into one of a group of first spaces, which are spaces in the cylinder on a side of the remaining end of the piston rod with respect to each of the pistons, and a group of second spaces, which are spaces in the cylinder opposite to the group of first spaces with respect to the each of the of pistons, respectively, and sucks gas from an interior of the other of the group of first spaces and the group of second spaces.

According to various aspects and exemplary embodiments of the present disclosure, it is possible to increase thrust of the gas cylinder.

Hereinafter, Examples of the disclosed gas cylinder will be described in detail with reference to the drawings. Further, the disclosed gas cylinder is not limited by the following Examples.

[Configuration of Air Cylinder10]

FIG. 1is a block diagram illustrating an example of an air cylinder10according to Example 1. In the present Example, as illustrated inFIG. 1for example, the air cylinder10has a controller11, an air supply unit12, a plurality of valves14-1and14-2, and an air cylinder main body20. Further, hereinafter, the valves14-1and14-2are simply referred to as valves14when the valves14-1and14-2are not distinguished from each other but collectively referred. In the present Example, the air cylinder10is used for, for example, a drive unit in a transport system for transporting a semiconductor wafer in a device for processing the semiconductor wafer, or a drive unit for a pusher pin for moving a semiconductor wafer upward and downward with respect to a placement table in the processing device. The air cylinder10is an example of a gas cylinder.

The air supply unit12has a regulator120, a mist separator121, an air filter122, a tank123, and a compressor124. The compressor124sucks atmospheric air and compresses the sucked air to produce compressed air. The tank123stores the compressed air produced by the compressor124. The air filter122removes particles in the compressed air stored in the tank123. The mist separator121produces dry air by removing moisture from the compressed air from which the particles are removed by the air filter122. The regulator120adjusts pressure of the dry air, from which the moisture is removed by the mist separator121and which is supplied to the valves14, to predetermined pressure. Hereinafter, the dry air, which is outputted to the valves14from the air supply unit12, is referred to as compressed air.

The air cylinder main body20has a cylinder21and a piston rod24. The cylinder21is provided with a port22and a port23, the compressed air is supplied into the cylinder21from one of the port22and the port23, and air in the cylinder21is sucked from the other of the port22and the port23. In the present Example, the air in the cylinder21is sucked by a gas discharge device13. In the example illustrated inFIG. 1, the air in the cylinder21is sucked from the port22, and the compressed air is supplied into the cylinder21from the port23such that the piston rod24is pushed out from the cylinder21. Meanwhile, the compressed air is supplied into the cylinder21from the port22, and the air in the cylinder21is sucked from the port23such that the piston rod24is pulled back into the cylinder21.

For example, the gas discharge device13has a vacuum pump such as a dry pump (DP) or a turbo molecular pump (TMP). The gas discharge device13may divert a vacuum pump used for a device for processing a semiconductor wafer.

Each of the valves14has three ports and a control terminal. In each of the valves14, one port is connected to the air supply unit12, another port is connected to the gas discharge device13, and the remaining port is connected to the air cylinder main body20. In addition, the control terminal of each of the valves14is connected to the controller11. Each of the valves14switches between a first state and a second state based on a control signal supplied to the control terminal from the controller11. The first state is a state in which the port connected to the air supply unit12and the port connected to the air cylinder main body20are in communication with each other. The second state is a state in which the port connected to the gas discharge device13and the port connected to the air cylinder main body20are in communication with each other.

The controller11controls the operations of pushing out and pulling back the piston rod24with respect to the cylinder21by controlling the control signal supplied to the control terminal of each of the valves14. The controller11and the plurality of valves14are an example of a gas controller.

[Configuration of Air Cylinder Main Body20]

FIG. 2is a cross-sectional view illustrating an example of the air cylinder main body20according to Example 1. In the present Example, the air cylinder main body20has the cylinder21and the piston rod24. The cylinder21is provided with the port22and the port23. For example, as illustrated inFIG. 2, one end24aof the piston rod24is disposed in the cylinder21, and the other end24bof the piston rod24protrudes from the cylinder21. A seal member27such as, for example, an O-ring is disposed between the cylinder21and the piston rod24, and hermeticity of a space in the cylinder21is maintained by the seal member27even when the piston rod24moves.

A piston25is provided at the one end24aof the piston rod24. The piston25moves in the cylinder21to move the piston rod24. A diameter of a cross section of the piston25in an extension direction of the piston rod24is slightly shorter than an inner diameter of the cylinder21. A seal member26such as, for example, an O-ring is provided around an outer circumference of the piston25, and the seal member26is closely attached to the outer circumference of the piston25and an inner surface of the cylinder21. By the piston25and the seal member26, the space in the cylinder21is hermetically divided into a space S1which is at the side of the piston rod24with respect to the piston25, and a space S2which is opposite to the space S1with respect the piston25. The space S1is in communication with the port22, and the space S2is in communication with the port23. The space S1is an example of the first space, and the space S2is an example of the second space.

A lubricant is applied onto the inner wall of the cylinder21. Therefore, the piston25may move in the cylinder21in the extension direction of the piston rod24while the space S1and the space S2are hermetically defined by the seal member26.

[Operation of Air Cylinder10]

When pushing out the piston rod24, the controller11controls the respective valves14, as illustrated inFIG. 3, for example.FIG. 3is a view illustrating an example of a method of supplying and sucking compressed air when pushing out the piston rod24according to Example 1. In each of the valves14illustrated inFIG. 3, the port, which is indicated in black, is the port controlled so that the compressed air passes through the port, and the port, which is indicated in white, is the port controlled so that the compressed air is blocked.

When pushing out the piston rod24, the controller11controls the valve14-1so that the valve14-1is in the second state, and controls the valve14-2so that the valve14-2is in the first state, as illustrated inFIG. 3, for example. Specifically, the controller11controls the valve14-1so that the port connected to the gas discharge device13and the port connected to the port22of the air cylinder main body20are in communication with each other, and controls the valve14-2so that the port connected to the air supply unit12and the port connected to the port23of the air cylinder main body20are in communication with each other.

Therefore, the compressed air outputted from the air supply unit12is supplied into the space S2in the cylinder21through the valve14-2and the port23, and force is applied to the piston25, in the direction in which the piston rod24is pushed out, by the compressed air supplied into the space S2. In addition, the compressed air in the space S1in the cylinder21is sucked by the gas discharge device13through the port22and the valve14-1such that the pressure in the space S1becomes approximate to the vacuum pressure. Therefore, a surface of the piston25, which is at the side of the space S1, is pulled to the side of the space S1. Therefore, the piston25moves in the cylinder21toward the space S1, and the piston rod24is pushed out.

Here, thrust A in the direction in which the piston rod24is pushed out is expressed by the following Equation (1), for example.
A=SP1×PC+SP2×P0−SR×P0(1)

In Equation (1), SP1represents a cross-sectional area of the piston25in the extension direction of the piston rod24, SRrepresents a cross-sectional area of the piston rod24, and SP2represents an area obtained by subtracting SRfrom SP1. In addition, in Equation (1), PCrepresents pressure of the compressed air, and P0represents atmospheric pressure. Further, the pressure PCrepresents gauge pressure, and the pressure P0represents absolute pressure.

In the present Example, the pressure in the space, which is sucked by the gas discharge device13, is several tens of millitorrs, for example, that is, sufficiently low compared to the atmospheric pressure P0or the pressure PCof the compressed air such that the pressure in the space may approximate to 0. For example, assuming that a diameter of a cross section of the piston25is 20 mm and a diameter of a cross section of the piston rod24is 10 mm, the thrust A, in the direction in which the piston rod24is pushed out, against the pressure PCof the compressed air is illustrated inFIG. 4, for example.

FIG. 4is a view illustrating an example of a relationship between pressure of compressed air and thrust when pushing out the piston rod24according to Example 1.FIG. 4illustrates thrust of the air cylinder having another configuration as a Comparative Example. In the air cylinder according to the Comparative Example, the air in the space S1is not sucked by the gas discharge device13, but the space S1is opened to the atmosphere through the port22.

Referring toFIG. 4, when the pressure PCof the compressed air is 0.1 MPa, the thrust is about 30 N in the Comparative Example, but in the air cylinder10according to the present Example, the thrust A in the direction in which the piston rod24is pushed out is increased to the extent that the air discharged from the interior of the cylinder21is sucked using the gas discharge device13. In addition, both of the thrust of the air cylinder according to the Comparative Example and the thrust of the air cylinder10according to the present Example are increased as the pressure of the compressed air is increased, but at either pressure of the compressed air, the thrust of the air cylinder10according to the present Example is greater than the thrust of the air cylinder according to the Comparative Example.

Therefore, in a case in which the cylinder21having the inner diameter equal to the inner diameter of the cylinder according to the Comparative Example is used, the air cylinder10according to the present Example may have greater thrust than the air cylinder according to the Comparative Example. In addition, in a case in which the thrust equal to the thrust according to the Comparative Example is obtained, the cylinder21having the inner diameter smaller than the inner diameter of the cylinder according to the Comparative Example may be used such that the air cylinder main body20may be reduced in size. For this reason, the air cylinder10including the air cylinder main body20may be reduced in size such that a device in which the air cylinder10is incorporated may be reduced in size.

When pulling back the piston rod24, the controller11controls the respective valves14, as illustrated inFIG. 5, for example.FIG. 5is a view illustrating an example of a method of supplying and sucking compressed air when pulling back the piston rod24according to Example 1. When pulling back the piston rod24, the controller11controls the valve14-1so that the valve14-1is in the first state, and controls the valve14-2so that the valve14-2is in the second state, as illustrated inFIG. 5, for example. Specifically, the controller11controls the valve14-1so that the port connected to the air supply unit12and the port connected to the port22of the air cylinder main body20are in communication with each other, and controls the valve14-2so that the port connected to the gas discharge device13and the port connected to the port23of the air cylinder main body20are in communication with each other.

Therefore, the compressed air outputted from the air supply unit12is supplied into the space S1in the cylinder21through the valve14-1and the port22, and force is applied to the surface of the piston25at the side of the space S1, by the compressed air supplied into the space S1, in the direction in which the piston rod24is pulled back. In addition, the compressed air in the space S2in the cylinder21is sucked by the gas discharge device13through the port23and the valve14-2such that the pressure in the space S2becomes approximate to the vacuum pressure. Therefore, the surface of the piston25at the side of the space S2, is pulled to the side of the space S2. Therefore, the piston25moves in the cylinder21toward the space S2, and the piston rod24is pulled back.

Thrust A′ in the direction in which the piston rod24is pulled back is expressed by the following Equation (2), for example.
A′=SP2×PC+SP1×P0(2)

Here, when pulling back the piston rod24in the air cylinder10according to the present Example, the compressed air is supplied into the space S1from the port22, and the air in the space S2is sucked from the port23by the gas discharge device13. Therefore, the air cylinder10according to the present Example may increase the thrust when pulling back the piston rod24in comparison with the air cylinder in which the port23is opened to the atmosphere. In addition, in a case in which the thrust equal to the thrust of the air cylinder in the related art is obtained, the cylinder21having the inner diameter smaller than the inner diameter of the air cylinder in the related art may be used in the air cylinder10according to the present Example such that the air cylinder main body20may be reduced in size. For this reason, the air cylinder10including the air cylinder main body20may be reduced in size such that a device in which the air cylinder10is incorporated may be reduced in size.

The air cylinder10according to the present Example is a so-called double-action air cylinder in which the compressed air is supplied into the space S2and the air is sucked from the interior of the space S1using the gas discharge device13when pushing out the piston rod24, and the compressed air is supplied into the space S1and the air is sucked from the interior of the space S2using the gas discharge device13when pulling back the piston rod24. However, the disclosed technology may also be applied to a so-called single-action air cylinder in which the compressed air is supplied and the air is sucked by the gas discharge device13when performing any of the operations of pushing out and pulling back the piston rod24.

[Configuration of Air Cylinder10]

FIG. 6is a block diagram illustrating an example of an air cylinder10according to Example 2. In the present Example, as illustrated inFIG. 6for example, the air cylinder10has a controller11, an air supply unit12, a plurality of valves14-1to14-4, and an air cylinder main body30. Further, hereinafter, the valves14-1to14-4are simply referred to as valves14when the valves14-1to14-4are not distinguished from one another but collectively referred. In addition, because the blocks indicated inFIG. 6by the same reference numerals as the blocks inFIG. 1have equal and the same functions as the blocks inFIG. 1except for the following description, descriptions thereof will be omitted.

The air cylinder main body30has a cylinder31and a piston rod34. The cylinder31is provided with a plurality of ports32-1and32-2and a plurality of ports33-1and33-2. Further, hereinafter, the plurality of ports32-1and32-2are simply referred to as ports32when the plurality of ports32-1and32-2are not distinguished from each other but collectively referred, and the plurality of ports33-1and33-2are simply referred to as ports33when the plurality of ports33-1and33-2are not distinguished from each other but collectively referred.

Compressed air is supplied into the cylinder31from one of the ports32and33, and air in the cylinder31is sucked from the other of the ports32and33. Even in the present Example, the air in the cylinder31is sucked by a gas discharge device13. In the example inFIG. 6, the compressed air is supplied into the cylinder31from the respective ports33, and the air in the cylinder31is sucked from the respective ports32such that the piston rod34is pushed out from the cylinder31. Meanwhile, the air in the cylinder31is sucked from the respective ports33, and the compressed air is supplied into the cylinder31from the respective ports32such that the piston rod34is pulled back into the cylinder31.

[Configuration of Air Cylinder Main Body30]

FIG. 7is a cross-sectional view illustrating an example of the air cylinder main body30according to Example 2. In the present Example, the air cylinder main body30has the cylinder31and the piston rod34. The cylinder31is provided with the plurality of ports32and the plurality of ports33. For example, as illustrated inFIG. 7, one end34aof the piston rod34is disposed in the cylinder31, and the other end34bof the piston rod34protrudes from the cylinder31. A seal member37is disposed between the cylinder31and the piston rod34, and hermeticity of a space in the cylinder31is maintained by the seal member37even when the piston rod34moves.

The piston rod34is provided with a plurality of pistons35-1and35-2. The piston35-2is provided at one end34aof the piston rod34, and the piston35-1is provided in the cylinder31at a position between the one end34aand the other end34bof the piston rod34. Further, hereinafter, the pistons35-1and35-2are simply referred to as pistons35when the pistons35-1and35-2are not distinguished from each other but collectively referred.

A seal member36such as, for example, an O-ring is provided around an outer circumference of each of the pistons35, and the seal member36is closely attached to the outer circumference of each of the pistons35and an inner surface of the cylinder31. By the pistons35and the seal members36, the space in the cylinder31is hermetically divided into spaces S1which are at the side of the other end34bof the piston rod34with respect to the pistons35, and spaces S2which are opposite to the spaces S1with respect to the pistons35.

The cylinder31has therein a space S3formed to be surrounded by the inner wall of the cylinder31and the two adjacent pistons35in the extension direction of the piston rod34. In addition, a partition wall38, which divides the space S3in the extension direction of the piston rod34, is provided in the cylinder31. Based on the partition wall38, the space S1is a space in the cylinder31at the side of the one end34aof the piston rod34(i.e., a side where the piston35-2is provided), and the space S2is a space in the cylinder31at the side of the other end34bof the piston rod34(i.e., a side where the piston35-1is provided). A seal member39such as, for example, an O-ring is provided between the partition wall38and the piston rod34, and the seal member39is closely attached to the partition wall38and the outer circumference of the piston rod34. By the partition wall38and the seal member39, the space S3between the two adjacent pistons35is hermetically divided into the space S1and the space S2.

A lubricant is applied onto the outer circumference of the piston rod34. Therefore, the piston rod34may move in the cylinder31in the extension direction of the piston rod34while the space S1and the space S2are hermetically defined by the partition wall38and the seal member39.

In the example inFIG. 7, the port32-1is in communication with the space S1, which is at the side of the other end34bof the piston rod34with respect to the piston35-1, and the port33-1is in communication with the space S2, which is at the side of the one end34aof the piston rod34with respect to the piston35-1. In addition, the port32-2is in communication with the space S1, which is at the side of the other end34bof the piston rod34with respect to the piston35-2, and the port33-2is in communication with the space S2, which is at the side of the one end34aof the piston rod34with respect to the piston35-2.

[Operation of Air Cylinder10]

When pushing out the piston rod34, the controller11controls the respective valves14, as illustrated inFIG. 8, for example.FIG. 8is a view illustrating an example of a method of supplying and sucking compressed air when pushing out the piston rod34according to Example 2. In the present Example, when pushing out the piston rod34, the controller11controls the valves14-1and14-3so that the valves14-1and14-3are in the second state, and controls the valves14-2and14-4so that the valves14-2and14-4are in the first state, as illustrated inFIG. 8, for example. Specifically, the controller11controls the respective valves14-1and14-3so that the port connected to the gas discharge device13and the port connected to each of the ports32of the air cylinder main body30are in communication with each other. In addition, the controller11controls the respective valves14-2and14-4so that the port connected to the air supply unit12and the port connected to each of the ports33of the air cylinder main body30are in communication with each other.

Therefore, the compressed air outputted from the air supply unit12is supplied into the spaces S2in the cylinder31from the respective ports33through the valves14-2and14-4, and force is applied to the respective pistons35, in the direction in which the piston rod34is pushed out, by the compressed air supplied into the spaces S2. In addition, the air in the spaces S1in the cylinder31is sucked by the gas discharge device13from the respective ports32through the valves14-1and14-3such that the pressure in the spaces S1becomes approximate to the vacuum pressure. Therefore, surfaces of the respective pistons35, which are at the side the spaces S1, are pulled to the side of the spaces S1. Therefore, the respective pistons35move in the cylinder31toward the spaces S1, and the piston rod34is pushed out.

Here, in the present Example, thrust A in the direction in which the piston rod34is pushed out is expressed by the following Equation (3), for example.
A={SP1+SP2}×PC+2×P0×(SP2−SR)  (3)

In the above Equation (3), SRrepresents a cross-sectional area of the piston rod34.

In the present Example, for example, assuming that a diameter of a cross-sectional area of the piston35in the extension direction of the piston rod34is 20 mm and a diameter of a cross section of the piston rod34is 10 mm, the thrust A, against the pressure of the compressed air, in the direction in which the piston rod34is pushed out is the same as that inFIG. 9, for example.FIG. 9is a view illustrating an example of a relationship between pressure of compressed air and thrust when pushing out the piston rod34according to Example 2.FIG. 9also illustrates both the thrust of the air cylinder according to the Comparative Example and the thrust of the air cylinder10according to Example 1.

In the air cylinder10according to the present Example, the plurality of pistons35are provided on the piston rod34, and the compressed air is supplied and the air is sucked by the gas discharge device13with respect to the respective pistons35. Therefore, the air cylinder10according to the present Example may increase the thrust A in comparison with the Comparative Example, as illustrated inFIG. 9, for example. In addition, the air cylinder10according to the present Example may increase the thrust in comparison with the air cylinder in Example 1.

When pulling back the piston rod34, the controller11controls the respective valves14, as illustrated inFIG. 10, for example.FIG. 10is a view illustrating an example of a method of supplying and sucking compressed air when pulling back the piston rod34according to Example 2. In the present Example, when pulling back the piston rod34, the controller11controls the valves14-1and14-3so that the valves14-1and14-3are in the first state, and controls the valves14-2and14-4so that the valves14-2and14-4are in the second state, as illustrated inFIG. 10, for example. Specifically, the controller11controls the respective valves14-1and14-3so that the port connected to the air supply unit12and the port connected to each of the ports32of the air cylinder main body30are in communication with each other. In addition, the controller11controls the respective valves14-2and14-4so that the port connected to the gas discharge device13and the port connected to each of the ports33of the air cylinder main body30are in communication with each other.

Therefore, the compressed air outputted from the air supply unit12is supplied into the spaces S1in the cylinder31from the respective ports32through the valves14-1and14-3, and force is applied to the respective pistons35, in the direction in which the piston rod34is pulled back, by the compressed air supplied into the spaces S1. In addition, the air in the spaces S2in the cylinder31is sucked by the gas discharge device13from the respective ports33through the valves14-2and14-4such that the pressure in the spaces S2becomes approximate to the vacuum pressure. Therefore, the surfaces of the respective pistons35, which are at the side of the spaces S2, are pulled to the side of the spaces S2. Therefore, the respective pistons35move in the cylinder31toward the spaces S2, and the piston rod34is pulled back.

In the present Example, thrust A′ in the direction in which the piston rod34is pulled back is expressed by the following Equation (4), for example.
A′=2×SP2×PC+SP1×P0+SP2×P0−SR×P0(4)

Here, when pulling back the piston rod34in the air cylinder10according to the present Example, the compressed air is supplied into the spaces S1from the ports32, and the air in the spaces S2is sucked from the ports33by the gas discharge device13. Therefore, the air cylinder10according to the present Example may further increase the thrust when pulling back the piston rod34in comparison with the air cylinder in the related art in which the port33is opened to the atmosphere.

The air cylinder10according to the present Example is a so-called double-action air cylinder in which the compressed air is supplied into the respective spaces S2and the air is sucked from the interior of the respective spaces S1using the gas discharge device13when pushing out the piston rod34, and the compressed air is supplied into the respective spaces S1and the air is sucked from the interior of the respective spaces S2using the gas discharge device13when pulling back the piston rod34. However, the disclosed technology may also be applied to a so-called single-action air cylinder in which the compressed air is supplied and the air is sucked by the gas discharge device13when performing any of the operations of pushing out and pulling back the piston rod34.

The respective examples of the air cylinder10have been described above. As apparent from the above description, according to the air cylinder10according to the respective examples, it is possible to increase thrust of the air cylinder. In addition, according to the air cylinder10according to the respective examples, it is possible to realize the thrust equal to the thrust in the related art using the air cylinder10that has a smaller size than the air cylinder in the related art.

The disclosed technology is not limited to the aforementioned Examples and may be variously modified within the scope of the subject matter thereof.

For example, in the respective examples, the compressed dry air is used as the gas to be supplied into the air cylinder main body20or the air cylinder main body30, but the disclosed technology is not limited thereto. As another example, any compressed gas may be supplied into the air cylinder main body20or the air cylinder main body30in accordance with an environment in which the air cylinder10is used.

In the aforementioned Example 2, the air cylinder main body30having the two pistons35-1and35-2provided on the piston rod34has been described as an example, but the disclosed technology is not limited thereto. As another example of the air cylinder main body30, n (n is an integer of 3 or more) pistons35may be provided on the piston rod34, as illustrated inFIG. 11, for example.FIG. 11is a cross-sectional view illustrating another example of the air cylinder main body30according to Example 2.

In this case, (n−1) partition walls38, which divide the space S3surrounded by the inner wall of the cylinder31and the two adjacent pistons35in the extension direction of the piston rod34, are provided in the cylinder31in which a partition wall38is provided every two pistons35adjacent in the extension direction of the piston rod34. In the space S3, the space in the cylinder31on the side of the one end34aof the piston rod34with respect to the partition wall38is the space S1, and the space in the cylinder31on the side of the other end34bof the piston rod34is the space S2.

In the air cylinder10illustrated inFIG. 11, thrust A in the direction in which the piston rod34is pushed out is expressed by the following Equation (5), for example.
A={SP1+(n−1)×SP2}×PC+n×P0×(SP2−SR)  (5)

In the air cylinder10illustrated inFIG. 11, thrust A′ in the direction in which the piston rod34is pulled back is expressed by the following Equation (6), for example.
A′=n×SP2×PC+P0×{SP1+(n−1)×(SP2−SR)}  (6)

Even in the case of the air cylinder10illustrated inFIG. 11, it is possible to increase the thrust of the air cylinder.

The two ports, which are used to supply and suck the compressed air, are provided for the spaces S1and S2, respectively, one by one, in the cylinder21in the aforementioned Example 1, but the plurality of ports may be provided for the space S1, and the plurality of ports may be provided for the space S2. Similarly, the two ports, which are used to supply and suck the compressed air, are provided for the respective spaces S1and S2, respectively, one by one, in the cylinder31even in the aforementioned Example 2, but the plurality of ports may be provided for the respective spaces S1, and the plurality of ports may be provided for the respective spaces S2.