Fluid circuit for air cylinder

Abstract

A fluid circuit for a pneumatic cylinder (10) is connected to a switching valve (28) equipped with exhaust ports (30A, 30B). The head-side pressure chamber (22) is connected to the switching valve via a first pipe (26A), and the rod-side pressure chamber (24) is connected to the switching valve via a second pipe (26B). A first throttling section (32A) is disposed at the connection between the first pipe and the switching valve or near the first output port of the switching valve, and a second throttling section (32B) is disposed at the connection between the second pipe and the switching valve or near the second output port of the switching valve.

Description

Technical Field

[0001] This invention relates to the fluid circuit of a pneumatic cylinder, which includes a throttling section. Prior Technology

[0002] Previously, in order to limit the speed of a pneumatic cylinder, it is known to use a technique of configuring a fixed throttling section (fixed flow limiting orifice) at the feed and discharge ports of the pneumatic cylinder. Furthermore, in order to adjust the speed of the pneumatic cylinder to the most suitable level, it is known to use a technique of configuring a variable throttling section (variable flow limiting orifice) at the feed and discharge ports of the pneumatic cylinder.

[0003] For example, Japanese Patent Application Publication No. 2019-44952 describes a pneumatic cylinder equipped with a first speed controller and a second speed controller. The first speed controller is an opening in the cylinder outlet portion that supplies compressed air to the first cylinder chamber of the pneumatic cylinder. The second speed controller is an opening in the cylinder outlet portion that supplies compressed air to the second cylinder chamber of the pneumatic cylinder.

[0004] However, if a pneumatic cylinder with a throttling section at the feed / exhaust port operates at high speed and frequency, a large amount of heat energy will accumulate in the cylinder chamber, causing a significant rise in temperature throughout the cylinder. If the pneumatic cylinder does not have sufficient heat resistance, or if its operating speed and frequency are higher than assumed, its durability may be compromised. Specifically, the increased cylinder temperature may negatively impact rubber components such as seals and throttle valves. Summary of the Invention

[0005] [The problem the invention aims to solve]

[0006] The purpose of this invention is to solve the aforementioned problems. [Technical means used to solve the problem]

[0007] The fluid circuit of the pneumatic cylinder of the present invention is connected to a switching valve equipped with an exhaust port. The pneumatic cylinder comprises a head-side pressure chamber and a rod-side pressure chamber, divided by a piston. The head-side pressure chamber is connected to the first output port of the switching valve via a first pipe, and the rod-side pressure chamber is connected to the second output port of the switching valve via a second pipe. The switching valve switches the air supply and exhaust of the head-side pressure chamber and the rod-side pressure chamber. A first throttling section is disposed at the connection between the first pipe and the switching valve, or near the first output port of the switching valve, and a second throttling section is disposed at the connection between the second pipe and the switching valve, or near the second output port of the switching valve.

[0008] Based on the fluid circuit of the pneumatic cylinder described above, the volume of air that can store heat generated by the throttling section includes the volume of the first pipe and the volume of the second pipe. Therefore, in addition to suppressing the rise in air temperature, the temperature rise of the pneumatic cylinder is also suppressed because the switching valve is cooled by the exhaust from the exhaust port.

[0009] In the fluid circuit of the pneumatic cylinder of the present invention, a first throttling section is provided at the connection between the first pipe and the switching valve or near the first output port of the switching valve, and a second throttling section is provided at the connection between the second pipe and the switching valve or near the second output port of the switching valve. Therefore, in addition to increasing the heat capacity of the air, a cooling effect can also be obtained, and the temperature rise of the pneumatic cylinder can be suppressed.

[0010] The aforementioned objectives, features, and advantages can be readily understood by referring to the following description of the embodiments, which are illustrated in the accompanying drawings. Simple Explanation of the Diagram

[0011] [Figure 1] is a diagram used to illustrate the basic concept of the present invention.

[0012] [Figure 2] is a concept diagram of Comparative Example 1.

[0013] [Figure 3] is a concept diagram of Comparative Example 2.

[0014] [Figure 4] is a table summarizing the measurement data related to the present invention and comparative examples.

[0015] [Figure 5] is an external view of the fluid circuit of the pneumatic cylinder according to the first embodiment of the present invention.

[0016] [Figure 6] is a cross-sectional view of the fluid circuit of the pneumatic cylinder in Figure 5.

[0017] [Figure 7] is a cross-sectional view of the fluid circuit of the pneumatic cylinder according to the second embodiment of the present invention. Implementation

[0018] First, the basic concept of the present invention will be explained while comparing it with Comparative Example 1 and Comparative Example 2. In the present invention, a throttling part (flow limiting orifice) is provided at the connection between the air supply pipe to the pneumatic cylinder and the switching valve, or near the output port of the switching valve. The description of the present invention also includes the configuration common to Comparative Example 1 and Comparative Example 2.

[0019] As shown in Figure 1, the pneumatic cylinder 10 includes a cylinder barrel 12, a head cover 14, a rod cover 16, and a piston 18. The head-side pressure chamber 22, located between the piston 18 and the head cover 14, is connected to the first output port 31A of the switching valve 28 via a first pipe 26A. The rod-side pressure chamber 24, located between the piston 18 and the rod cover 16, is connected to the second output port 31B of the switching valve 28 via a second pipe 26B. The switching valve 28 is equipped with a first exhaust port 30A and a second exhaust port 30B, both open to the atmosphere.

[0020] The switching valve 28 is switchable between a first position and a second position. In the first position, air from the fluid supply source 38 is supplied to the head-side pressure chamber 22 through the first pipe 26A, and air in the rod-side pressure chamber 24 is opened to the atmosphere through the second pipe 26B. In the second position, air from the fluid supply source 38 is supplied to the rod-side pressure chamber 24 through the second pipe 26B, and air in the head-side pressure chamber 22 is opened to the atmosphere through the first pipe 26A. When the switching valve 28 is switched to the first position, the piston rod 20 is pushed out. When the switching valve 28 is switched to the second position, the piston rod 20 is retracted.

[0021] The common aspects of this invention with Comparative Examples 1 and 2 are as described above. In this invention, a first throttling section 32A is disposed at the connection between the first piping 26A and the switching valve 28, or near the first output port 31A of the switching valve 28. Furthermore, a second throttling section 32B is disposed at the connection between the second piping 26B and the switching valve 28, or near the second output port 31B of the switching valve 28.

[0022] In Comparative Example 1, as shown in FIG2, a first throttling section 34A is provided at the connection point (head-side opening) between the head-side pressure chamber 22 and the first piping 26A. Furthermore, a second throttling section 34B is provided at the connection point (rod-side opening) between the rod-side pressure chamber 24 and the second piping 26B.

[0023] In Comparative Example 2, as shown in FIG3, a first throttling section 36A is disposed midway through the first pipe 26A, and a second throttling section 36B is disposed midway through the second pipe 26B. In Comparative Example 2, the portion of the first pipe 26A extending from the first throttling section 36A to the pneumatic cylinder 10 is referred to as the "downstream portion of the first pipe 26A". Similarly, the portion of the second pipe 26B extending from the second throttling section 36B to the pneumatic cylinder 10 is referred to as the "downstream portion of the second pipe 26B".

[0024] Next, we will explain the generation and movement of heat in Comparative Example 1 and the accompanying temperature rise of the pneumatic cylinder 10.

[0025] During the extension of the piston rod 20, air is filled into the head-side pressure chamber 22 through the first throttling section 34A. As the air passes through the first throttling section 34A, a portion of its energy is converted into heat energy. This heat, while raising the air temperature, enters the head-side pressure chamber 22 along with the air. This heat is transmitted through the air as a medium to the components of the pneumatic cylinder 10, such as the head cover 14, causing their temperature to rise. Furthermore, a portion of this heat is transmitted from the first throttling section 34A to the components of the pneumatic cylinder 10 via thermal conduction. While heat is also generated when the air in the rod-side pressure chamber 24 passes through the second throttling section 34B during the extension of the piston rod 20, this heat has a small impact on the pneumatic cylinder 10.

[0026] During the retraction of the piston rod 20, air is filled into the rod-side pressure chamber 24 through the second throttling section 34B. As the air passes through the second throttling section 34B, a portion of its energy is converted into heat energy. This heat, while raising the air temperature, enters the rod-side pressure chamber 24 along with the air. This heat is transmitted through the air as a medium to the components of the pneumatic cylinder 10, such as the rod cover 16, causing their temperature to rise. A portion of this heat is transferred from the second throttling section 34B to the components of the pneumatic cylinder 10 via thermal conduction. While the air in the head-side pressure chamber 22 also generates heat when passing through the first throttling section 34A during the retraction of the piston rod 20, this heat has a small impact on the pneumatic cylinder 10.

[0027] Furthermore, a portion of the heat accumulated in the head-side pressure chamber 22 during the extension of the piston rod 20 is released along with air from the first throttling section 34A toward the first pipe 26A during the subsequent retraction of the piston rod 20. Also, a portion of the heat accumulated in the rod-side pressure chamber 24 during the retraction of the piston rod 20 is released along with air from the second throttling section 34B toward the second pipe 26B during the subsequent extension of the piston rod 20.

[0028] Thus, the heat generated during the extension and retraction of the piston rod 20 will be accumulated in the pneumatic cylinder 10 to a certain extent. If the piston 18 reciprocates repeatedly, the temperature of the pneumatic cylinder 10 will rise until the heat released by the pneumatic cylinder 10, which is mainly due to natural heat dissipation, reaches a state of equilibrium with the heat received by the pneumatic cylinder 10. In Comparative Example 1, the pneumatic cylinder 10 reaches a very high temperature.

[0029] Next, we will explain the generation and movement of heat in Comparative Example 2, and the accompanying temperature rise of the pneumatic cylinder 10.

[0030] During the extension of the piston rod 20, air is filled through the first throttling section 36A to the downstream portion of the first pipe 26A and the head-side pressure chamber 22. As the air passes through the first throttling section 36A, a portion of the energy held by the air is converted into heat energy. This heat, while raising the air temperature, is transported along with the air to the downstream portion of the first pipe 26A and the head-side pressure chamber 22. This heat is transmitted through the air as a medium to the components of the pneumatic cylinder 10, such as the head cover 14, causing the temperature of these components to rise. Furthermore, a portion of the aforementioned heat is transmitted via thermal conduction from the first throttling section 36A to the first pipe 26A, and further from the first pipe 26A to the components of the pneumatic cylinder 10.

[0031] During the retraction of the piston rod 20, air is filled through the second throttling section 36B to the downstream portion of the second pipe 26B and the rod-side pressure chamber 24. As the air passes through the second throttling section 36B, a portion of the energy held by the air is converted into heat energy. This heat, while raising the temperature of the air, is transported along with the air to the downstream portion of the second pipe 26B and the rod-side pressure chamber 24. This heat is transmitted through the air as a medium to the components of the pneumatic cylinder 10, such as the rod cover 16, causing the temperature of these components to rise. Furthermore, a portion of the aforementioned heat is transmitted via thermal conduction from the second throttling section 36B to the second pipe 26B, and further from the second pipe 26B to the components of the pneumatic cylinder 10.

[0032] Thus, the heat generated during the extension and retraction of the piston rod 20 is not only accumulated in the pneumatic cylinder 10, but is also distributed and accumulated through the downstream portion of the first pipe 26A and the downstream portion of the second pipe 26B.

[0033] If the piston 18 reciprocates repeatedly, the temperature of the pneumatic cylinder 10 will rise until the heat released by the pneumatic cylinder 10, which is mainly based on natural heat dissipation, reaches a state of equilibrium with the heat received by the pneumatic cylinder 10. In this case, the volume of the air containing the heat will not only include the volume of the head-side pressure chamber 22 and the rod-side pressure chamber 24, but also the volume of the downstream portion of the first pipe 26A and the downstream portion of the second pipe 26B. Therefore, compared with Comparative Example 1, the air has a larger heat capacity, and the air will not reach the high temperature of Comparative Example 1, nor will the pneumatic cylinder 10 reach the high temperature of Comparative Example 1.

[0034] Next, it will be explained that the generation, movement, and release (cooling) of heat in this invention, and the accompanying temperature rise of the pneumatic cylinder 10.

[0035] During the extension of the piston rod 20, air is filled into the entire first pipe 26A and the head-side pressure chamber 22 through the first throttling section 32A. As the air passes through the first throttling section 32A, a portion of the energy held by the air is converted into heat energy. This heat, while raising the temperature of the air, is transported along with the air to the first pipe 26A and the head-side pressure chamber 22. This heat is transmitted to the components of the pneumatic cylinder 10, such as the head cover 14, via the air as a medium, causing the temperature of these components to rise. Furthermore, a portion of the aforementioned heat is transmitted from the first throttling section 32A to the first pipe 26A via thermal conduction, and further from the first pipe 26A to the components of the pneumatic cylinder 10.

[0036] During the extension of the piston rod 20, the air filled into the second pipe 26B and the rod-side pressure chamber 24 is discharged to the atmosphere through the second throttling section 32B and the second exhaust port 30B attached to the switching valve 28. When the air is discharged from the second exhaust port 30B, it expands rapidly in an adiabatic state, causing its temperature to drop. Therefore, the switching valve 28 is cooled, as are the first throttling section 32A and the second throttling section 32B. This achieves the effect of cooling the first pipe 26A, the second pipe 26B, and the air inside them. Furthermore, although the air filled into the second pipe 26B and the rod-side pressure chamber 24 generates heat when passing through the second throttling section 32B during the extension of the piston rod 20, this heat does not affect the pneumatic cylinder 10.

[0037] During the retraction of the piston rod 20, air is filled into the second pipe 26B and the rod-side pressure chamber 24 through the second throttling section 32B. As the air passes through the second throttling section 32B, a portion of its energy is converted into heat energy. This heat, while raising the air temperature, is transported along with the air to the second pipe 26B and the rod-side pressure chamber 24. This heat is transmitted through the air as a medium to the components of the pneumatic cylinder 10, such as the rod cover 16, causing their temperature to rise. Furthermore, a portion of this heat is transmitted via thermal conduction from the second throttling section 32B to the second pipe 26B, and further from the second pipe 26B to the components of the pneumatic cylinder 10.

[0038] During the retraction of the piston rod 20, the air filling the first pipe 26A and the head-side pressure chamber 22 is discharged to the atmosphere through the first throttling section 32A and the first exhaust port 30A attached to the switching valve 28. When the air is discharged from the first exhaust port 30A, it expands rapidly in an adiabatic state, causing the air temperature to drop. Therefore, the switching valve 28 is cooled, and the first throttling section 32A and the second throttling section 32B are also cooled. Furthermore, the first pipe 26A, the second pipe 26B, and the air inside them are cooled. Also, although the air filling the first pipe 26A and the head-side pressure chamber 22 generates heat when passing through the first throttling section 32A during the retraction of the piston rod 20, this heat does not affect the pneumatic cylinder 10.

[0039] Thus, the heat generated during the extension and retraction of the piston rod 20 is not only accumulated in the pneumatic cylinder 10, but is also distributed and accumulated through the entire first piping 26A and the entire second piping 26B. Furthermore, by cooling the switching valve 28 during the extension and retraction of the piston rod 20, the first piping 26A, the second piping 26B, and the air inside them can be cooled.

[0040] If the piston 18 reciprocates repeatedly, the temperature of the pneumatic cylinder 10 will rise until the heat released and the heat received by the pneumatic cylinder 10 reach equilibrium. In the present invention, the volume of the air containing the heat is not only the volume of the head-side pressure chamber 22 and the rod-side pressure chamber 24, but also the entire volume of the first pipe 26A and the entire volume of the second pipe 26B. Compared with Comparative Example 2, the heat capacity of the air is greater. Furthermore, because the first throttling section 32A and the second throttling section 32B are directly connected to the switching valve 28, the air inside the first pipe 26A and the second pipe 26B can be cooled. Therefore, the air is less likely to become hot, and the temperature rise of the pneumatic cylinder 10 can be sufficiently suppressed.

[0041] In order to understand the temperature of each part when the piston 18 reciprocates (vibrates) according to a predetermined cycle, experiments were conducted on the fluid circuits of each pneumatic cylinder 10 of Comparative Example 1 and Comparative Example 2. The parts are cylinder 12, head cover 14, rod cover 16, switching valve 28, first throttling sections 32A, 34A, 36A, and second throttling sections 32B, 34B, 36B.

[0042] For the pneumatic cylinder 10 used, the inner diameter of the cylinder barrel 12 is 10 mm, and the stroke of the piston 18 is 45 mm. For the first piping 26A used, the inner diameter is 4 mm and the length is 500 mm. Similarly, for the second piping 26B used, the inner diameter is 4 mm and the length is 500 mm. The flow-limiting orifice diameter of the first throttling sections 32A, 34A, and 36A is set to 1.1 mm, and the flow-limiting orifice diameter of the second throttling sections 32B, 34B, and 36B is set to 1.8 mm. For the cycle time of the switching valve 28, the time from switching to the first position to switching to the second position, and the time from switching to the second position to switching to the first position, are both set to 35 ms.

[0043] In this invention, the distance from the pneumatic cylinder 10 to the first throttling section 32A is 500 mm, the same as the length of the first piping 26A. Furthermore, the distance from the pneumatic cylinder 10 to the second throttling section 32B is 500 mm, the same as the length of the second piping 26B. In Comparative Example 1, the distance from the pneumatic cylinder 10 to the first throttling section 34A is zero, and the distance from the pneumatic cylinder 10 to the second throttling section 34B is zero. In Comparative Example 2, the first throttling section 36A is located exactly at the center of the first piping 26A, and the second throttling section 36B is located exactly at the center of the second piping 26B. Therefore, the distance from the pneumatic cylinder 10 to the first throttling section 36A is 250 mm, and the distance from the pneumatic cylinder 10 to the second throttling section 36B is 250 mm.

[0044] The temperatures (maximum temperatures) of various parts of the pneumatic cylinder 10 were measured after 5 minutes of operation at room temperature (25°C). The results are summarized in Figure 4.

[0045] In Comparative Example 1, the cylinder barrel 12 was heated to 100°C, the head cover 14 was heated to 111°C, and the rod cover 16 was heated to 63°C. In Comparative Example 2, the cylinder barrel 12 was heated to 64°C, the head cover 14 was heated to 50°C, and the rod cover 16 was heated to 46°C.

[0046] In this invention, the temperature of the cylinder 12 only rises to 56°C, and the temperatures of the head cover 14 and the rod cover 16 only rise to 39°C. It can be understood that the temperature rise of the constituent parts of the pneumatic cylinder 10 of this invention is sufficiently suppressed.

[0047] Furthermore, it can be understood that in Comparative Example 1, the temperature of the switching valve 28 is 17°C lower than room temperature, indicating that the switching valve 28 is considerably cooled. Also, in Comparative Example 1, the temperature of the head cover 14 is significantly higher than the temperature of the rod cover 16. This demonstrates that the thermal effects occurring in the first throttling section 34A, whose flow-limiting orifice diameter is smaller than that of the second throttling section 34B, are substantial.

[0048] (First Embodiment) The fluid circuit 40 of the pneumatic cylinder according to the first embodiment of the present invention will be described with reference to Figures 5 and 6. The fluid circuit 40 of the pneumatic cylinder includes a pneumatic cylinder 42, a first pipe 58, a second pipe 60, a first speed controller 62 (first throttling section), a second speed controller 64 (second throttling section), and a switching valve 66.

[0049] The switching valve 66 comprises: a housing 68 having an internal valve port 68a, and a slidable valve body 70 disposed in the valve port 68a. The housing 68 includes a first exhaust port 72 with a silencer and a second exhaust port 74 with a silencer. The housing 68 also includes: a supply port 68b connected to a fluid supply source (not shown), a first output port 68c connected to a first speed controller 62, and a second output port 68d connected to a second speed controller 64.

[0050] The variable throttling unit, also known as the first speed controller 62, consists of a valve body 62a having an internal air passage 62c and a needle valve body 62b inserted into the air passage 62c. The end of the needle valve body 62b extending outward from the valve body 62a has a gripping portion 62d. By rotating this gripping portion 62d, the area of ​​the air passage 62c can be changed. The valve body 62a is L-shaped. One end of the valve body 62a is connected to the first output port 68c of the switching valve 66, and the other end of the valve body 62a is connected to the first piping 58.

[0051] The variable throttling unit, also known as the second speed controller 64, is similar to the first speed controller 62, consisting of a valve body 64a and a needle valve body 64b. One end of the valve body 64a is connected to the second output port 68d of the switching valve 66, and the other end of the valve body 64a is connected to the second piping 60.

[0052] The pneumatic cylinder 42 comprises a cylinder barrel 44, a head cover 46, a rod cover 48, a piston 50, and a piston rod 52. The head-side pressure chamber 54, located between the piston 50 and the head cover 46, is connected to the first piping 58. The rod-side pressure chamber 56, located between the piston 50 and the rod cover 48, is connected to the second piping 60.

[0053] The switching valve 66 corresponds to the sliding position of the spool valve body 70 and can be switched between the first position where the piston rod 52 is pushed out and the second position where the piston rod 52 is retracted. As shown in Figure 6, the switching valve 66 is in the first position.

[0054] When the switching valve 66 is in the first position, the air passage 62c of the first speed controller 62 is connected to the supply port 68b, and the air passage 64c of the second speed controller 64 is connected to the second exhaust port 74. Air from the fluid supply source is supplied to the first piping 58 and the head-side pressure chamber 54 through the first speed controller 62. Furthermore, air from the second piping 60 and the rod-side pressure chamber 56 is discharged to the atmosphere from the second exhaust port 74 through the second speed controller 64.

[0055] When the switching valve 66 is in the second position, the air passage 64c of the second speed controller 64 is connected to the supply port 68b, and the air passage 62c of the first speed controller 62 is connected to the first exhaust port 72. Air from the fluid supply source is supplied to the second piping 60 and the rod-side pressure chamber 56 through the second speed controller 64. Furthermore, air from the first piping 58 and the head-side pressure chamber 54 is discharged to the atmosphere from the first exhaust port 72 through the first speed controller 62.

[0056] During the extension of piston rod 52, the heat generated when air passes through the first speed controller 62 is transported along with the air to the first piping 58 and the head-side pressure chamber 54. During the retraction of piston rod 52, the heat generated when air passes through the second speed controller 64 is transported along with the air to the second piping 60 and the rod-side pressure chamber 56. That is, the volume of air containing the generated heat is not only the volume of the head-side pressure chamber 54 and the rod-side pressure chamber 56, but also the total volume of the first piping 58 and the total volume of the second piping 60, thus increasing the heat capacity of the air. Therefore, the air is less likely to become hot, and the temperature rise of the pneumatic cylinder 42 is suppressed.

[0057] Furthermore, during the extension of piston rod 52, air is discharged from the second exhaust port 74, and its temperature decreases due to adiabatic expansion. During the retraction of piston rod 52, air is discharged from the first exhaust port 72, and its temperature also decreases due to adiabatic expansion. As a result, switching valve 66 is cooled, as are the first speed controller 62 and the second speed controller 64. This also achieves the effect of cooling the first piping 58, the second piping 60, and the air inside them. Therefore, the temperature rise of pneumatic cylinder 42 is suppressed.

[0058] According to this embodiment, the volume of air that accumulates heat generated by the first speed controller 62 and the second speed controller 64 includes the volume of the first piping 58 and the volume of the second piping 60. Therefore, the temperature rise of the air is suppressed, and the temperature rise of the pneumatic cylinder 42 is suppressed. Furthermore, since the switching valve 66 is cooled along with the exhaust from the first exhaust port 72 and the second exhaust port 74, the temperature rise of the pneumatic cylinder 42 is suppressed.

[0059] In this embodiment, although the first and second throttling sections are variable throttling sections, they can also be fixed throttling sections. Furthermore, the first and second throttling sections can be in the form of narrowing only the air flowing into the cylinder, but not the air exiting the cylinder (throttling sections on the inlet side). Also, although the switching valve 66 has two exhaust ports, they can be combined into a single exhaust port.

[0060] (Second Implementation) Next, the fluid circuit 80 of the pneumatic cylinder according to the second embodiment of the present invention will be described with reference to FIG7. Furthermore, the same reference numerals will be used for configurations that are the same as or equivalent to the fluid circuit 40 of the pneumatic cylinder described above, and detailed descriptions will be omitted.

[0061] The fluid circuit 80 of the pneumatic cylinder includes a pneumatic cylinder 42, a first pipe 58, a second pipe 60, a first connector 86, a second connector 88, and a switching valve 66. The first connector 86 is an L-shaped connector that connects the first output port 68c of the switching valve 66 to the first pipe 58. The second connector 88 is an L-shaped connector that connects the second output port 68d of the switching valve 66 to the second pipe 60.

[0062] The fixed throttling sections, namely the first throttling section 82 and the second throttling section 84, are housed within the switching valve 66. Specifically, the first throttling section 82 is positioned near the first output port 68c of the switching valve 66, at a predetermined location within the valve hole 68a of the housing 68, and between the first output port 68c and the valve hole 68a. Similarly, the second throttling section 84 is positioned near the second output port 68d of the switching valve 66, at a predetermined location within the valve hole 68a of the housing 68, and between the second output port 68d and the valve hole 68a.

[0063] According to this embodiment, the volume of air in which heat is stored due to the first throttling section 82 and the second throttling section 84 is the volume of the first piping 58 and the second piping 60. Therefore, the temperature rise of the air is suppressed, and the temperature rise of the pneumatic cylinder 42 is suppressed. Furthermore, because the switching valve 66, which houses the first throttling section 82 and the second throttling section 84, is cooled along with the exhaust from the first exhaust port 72 and the second exhaust port 74, the temperature rise of the pneumatic cylinder 42 is suppressed.

[0064] In this invention, a first throttling section and a second throttling section are provided at the positions with the smallest flow path area and the highest throttling effect in the flow path from the pneumatic cylinder to the switching valve. This invention also includes cases where other throttling sections with a flow path area wider than the first and second throttling sections are arranged in the flow path from the pneumatic cylinder to the switching valve.

[0065] This invention is not limited to the above-described embodiments; various configurations may be adopted without departing from the spirit of the invention.

[0066] 10: Pneumatic cylinder 12: Cylinder 14: Headgear 16: Pole Cover 18: Piston 20: Piston rod 22: Head pressure chamber 24: Rod-side pressure chamber 26A: 1st piping 26B: 2nd piping 28: Switching valve 30A: First exhaust port 30B: Second exhaust port 31A: First output port 31B: Second Output Port 32A, 34A, 36A: First throttling section 32B, 34B, 36B: Second throttling section 34A: First throttling section 34B: Second throttling section 36A: First throttling section 36B: Second throttling section 38: Fluid supply source 40: Fluid circuit 42: Pneumatic cylinder 44: Cylinder 46: Headgear 48: Pole Cover 50: Piston 52: Piston rod 54: Head pressure chamber 56: Rod-side pressure chamber 58: 1st piping 60: 2nd piping 62: First speed controller 62a: Valve body 62b: Needle valve body 62c: Air passage 62d: Grasping section 64: Second speed controller 64a: Valve body 64b: Needle valve body 64c: Air Pathway 66: Switching valve 68: Shell 68a: Valve port 68b: Supply Port 68c: First output port 68d: Second output port 70: Slide valve body 72: First exhaust port 74: Second exhaust port 80: Fluid Circuit 82: First Throttling Section 84: Second throttling section 86: Connector 1 88: Second connector

Claims

1. A fluid circuit for a pneumatic cylinder connected to a switching valve with an exhaust port, the pneumatic cylinder having a head-side pressure chamber and a rod-side pressure chamber divided by a piston, the head-side pressure chamber being connected to a first output port of the switching valve via a first pipe, the rod-side pressure chamber being connected to a second output port of the switching valve via a second pipe, the switching valve switching the air supply and exhaust of the head-side pressure chamber and the rod-side pressure chamber, a first throttling section being disposed at the connection between the first pipe and the switching valve, and a second throttling section being disposed at the connection between the second pipe and the switching valve; one end of the valve body of the first throttling section is connected to the first output port, and the other end of the valve body of the first throttling section is connected to the first pipe; one end of the valve body of the second throttling section is connected to the second output port, and the other end of the valve body of the second throttling section is connected to the second pipe.

2. The fluid circuit of the pneumatic cylinder as described in request item 1, wherein, The aforementioned first throttling section and the aforementioned second throttling section are variable throttling sections.

3. The fluid circuit of the pneumatic cylinder as described in request item 1, wherein, The aforementioned first throttling section and the aforementioned second throttling section are throttling sections on the inlet side.

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