Rotary cylinder and method for using same

Abstract

The present invention provides a rotary cylinder capable of reducing energy loss, and a method for using the same.　According to the present invention, there is provided a hydraulic rotary cylinder comprising a base and a rotary body configured to be capable of rotating relative to the base, wherein the rotary cylinder comprises an air supply unit, a gap is provided in an opposing region in which the rotary body and the base oppose each other, and the air supply unit is configured to be capable of supplying pressurized air to the gap via the base.

Description

Rotary cylinder and method of using the same

[0001] The present invention relates to a rotary cylinder installed in a machine tool and a method of using the same.

[0002] Patent Document 1 discloses a technique for cooling the inside of an oil sump by ventilating outside air in the oil sump by rotating a plurality of fans that rotate together with a rotating body in a rotary cylinder used in a machine tool.

[0003] Japanese Patent Application Laid-Open No. 2-51040

[0004] In the technique of Patent Document 1, although the generated heat is efficiently discharged and the temperature rise of the rotary cylinder is suppressed, since the heat generation itself is not suppressed, energy loss due to heat generation occurs.

[0005] The present invention has been made in view of such circumstances, and provides a rotary cylinder capable of reducing energy loss.

[0006] The present invention provides the following inventions: [1] A hydraulic rotary cylinder comprising a base and a rotating body configured to be rotatable relative to the base, comprising an air supply unit, wherein a gap is provided in the opposing region where the rotating body and the base face each other, and the air supply unit is configured to supply pressurized air to the gap via the base. [2] The rotary cylinder according to [1], wherein the rotating body comprises a first cylinder chamber and a second cylinder chamber for applying hydraulic pressure to a piston, the base comprises a first port, a second port and a first air supply port, the first port and the second port are configured to supply and discharge the hydraulic fluid to and from the first cylinder chamber and the second cylinder chamber, respectively, the opposing region is provided with a first connecting passage for connecting the first cylinder chamber and the first port and a second connecting passage for connecting the second cylinder chamber and the second port, and the first air supply port is configured to supply pressurized air to the gap. A rotary cylinder according to [3] [2], wherein the base comprises a pair of seal portions and a seal air supply portion, the pair of seal portions are respectively arranged on both sides of the gap in a direction along the rotation axis of the rotating body and are configured to prevent leakage of the hydraulic fluid, and the seal air supply portion is configured to supply pressurized air to the pair of seal portions from the outside in a direction along the rotation axis. A rotary cylinder according to any one of [4] [1] to [3], wherein the air supply portion is connected to the base via a check valve or a switching valve, the check valve or the switching valve is configured to prevent backflow of the working fluid including the hydraulic fluid and to control the air.[5] A method for using a rotary cylinder, the rotary cylinder comprising a rotating body, a base, and an air supply unit, wherein the rotating body is configured to rotate relative to the base and has a piston built inside, the base is configured to supply hydraulic fluid to the rotating body, a gap is provided in the opposing region where the rotating body and the base face each other, the air supply unit is configured to supply pressurized air to the gap, and the method for using a rotary cylinder includes: a first step of applying a predetermined oil pressure to the piston by supplying the hydraulic fluid to the rotating body via the base; a second step of stopping the supply of the hydraulic fluid to the rotating body while maintaining the state in which the predetermined oil pressure is applied to the piston; and a third step of discharging the hydraulic fluid from the gap by supplying pressurized air from the air supply unit to the gap.

[0007] The rotary cylinder of the present invention is equipped with an air supply unit that can supply pressurized air to the gap between the base and the rotating body through which hydraulic fluid is supplied from the base to the rotating body. Therefore, it is possible to forcibly discharge the hydraulic fluid filling this gap with pressurized air. Since air has a significantly lower viscosity than hydraulic fluid, even when the rotating body of the rotary cylinder rotates at high speed, heat generation in the gap between the base and the rotating body is suppressed, and the occurrence of energy loss due to heat generation is suppressed.

[0008] Figure 1A is a perspective view of the rotating cylinder 1 of the first embodiment of the present invention, viewed from the front right, and Figure 1B is an exploded perspective view of the rotating cylinder 1, viewed from the rear left. Figure 2A is a cross-sectional view of the rotating cylinder 1 of Figure 1A, cut by a vertical plane passing through the rotation axis C, and Figure 2B is an enlarged view of region A in Figure 2A. Figure 3A is a cross-sectional view of the rotating cylinder 1 of Figure 1A, viewed from the front, cut by a plane perpendicular to the rotation axis C and passing through the first ports 2AR, 2AL, and Figure 3B is a cross-sectional view of the rotating cylinder 1, viewed from the front, cut by a plane perpendicular to the rotation axis C and passing through the second ports 2BR, 2BL. Figure 4A is an exploded perspective view of the sleeve portion 21 and the lower body 23, viewed from the front right, and Figure 4B is an exploded perspective view of the sleeve portion 21 and the lower body 23, viewed from below and from the rear left. Figure 5 is a schematic diagram showing the supply and discharge of working fluid (hydraulic oil / air) to the rotating cylinder 1. Figure 6A is a perspective view of the rotary cylinder 1A of the second embodiment of the present invention, viewed from the front right, and Figure 6B is an exploded perspective view of the rotary cylinder 1A, viewed from the rear left. Figure 7 is a cross-sectional view of the rotary cylinder 1A cut by a vertical plane passing through the rotation axis C of the rotary cylinder 1A in Figure 6A. Figure 8A is an enlarged view of region B in Figure 7, and Figure 8B is a schematic diagram showing the flow of working fluid (hydraulic oil / air) in the gap 10 of the opposing region. Figure 9A is a cross-sectional view viewed from the front of a cross section cut by a plane perpendicular to the rotation axis C of the rotary cylinder 1A and passing through the first port 2A, and Figure 9B is a cross-sectional view viewed from the front of a cross section cut by a plane perpendicular to the rotation axis C of the rotary cylinder 1A and passing through the second port 2B. Figure 10 is a schematic diagram showing the supply and discharge of working fluid (hydraulic oil / air) to the rotary cylinder 1A.

[0009] Embodiments of the present invention will be described below. The various features shown in the embodiments below can be combined with each other. Furthermore, each feature constitutes an independent invention.

[0010] <First Embodiment> <Configuration of Rotating Cylinder 1> As shown in Figures 1A and 1B, a hydraulic rotating cylinder 1 according to one embodiment of the present invention comprises a base 2 and a rotating body 3 configured to be rotatable relative to the base 2. The base 2 is normally connected to a machine tool in a nearly non-rotating state. The rotating body 3 is fixed to the spindle of the machine tool and rotates around the rotation axis C in conjunction with the rotation of the spindle.

[0011] <Rotating Body 3> As shown in Figures 1B and 2A, the rotating body 3 comprises a rotating body 31 and a piston 32. The rotating body 31 comprises a front body 31A, a rear body 31B, and a rear cap 31C. The front body 31A and the rear body 31B are connected to each other by bolts or the like. The front body 31A and the rear body 31B provide a housing space 33 for applying hydraulic pressure to the piston 32. The rear body 31B is provided with a first passage 40A and a second passage 40B through which hydraulic fluid for operating the piston 32 flows. The first passage 40A extends to the front body 31A. The rear cap 31C is connected to the rear body 31B by bolts 31D. The rotating body 31 is fixed to the spindle by bolts 31E that pass through the front body 31A and the rear body 31B.

[0012] The piston 32 is housed within the rotating body 31. The piston 32 is slidable in both directions along the rotation axis C. The piston 32 comprises a cylindrical portion 32A, a flange portion 32B, and a connecting portion 32C. The cylindrical portion 32A is cylindrical in shape. The flange portion 32B is configured to move along the inner circumferential surface of the rotating body 31. The flange portion 32B divides the housing space 33 into two, forming a first cylinder chamber 33A and a second cylinder chamber 33B. A pin 32D is fixed to the flange portion 32B, and this pin 32D is inserted into a hole in the rotating body 31. As a result, the piston 32 can rotate integrally with the rotating body 31.

[0013] In one example, the connecting portion 32C is a female threaded portion provided on the inner surface of the cylindrical portion 32A, and is configured to be connectable to a chuck device via a rod or the like having a male threaded portion. When the piston 32 moves back and forth along the rotation axis C, this reciprocating motion is transmitted to the chuck device, allowing the jaws of the chuck device to grip and release the workpiece.

[0014] <Base 2> The base 2 comprises a sleeve portion 21, a bearing 22, and a lower body 23. The sleeve portion 21 is cylindrical. A pair of bearings 22 are provided inside the sleeve portion 21. The pair of bearings 22 support the rotating body 3, allowing the rotating body 3 to rotate relative to the base 2. In this embodiment, a gap 10 exists between the pair of bearings 22 in opposing regions where the inner circumferential surface of the sleeve portion 21 and the outer circumferential surface of the rotating body 3 face each other in the radial direction perpendicular to the rotation axis C. Because a gap 10 exists in the opposing regions, the base 2 and the rotating body 3 maintain a non-contact state. Furthermore, because the base 2 and the rotating body 3 are non-contact, even if the rotating body 3 rotates at high speed, the base 2 and the rotating body 3 will not seize up.

[0015] A pair of labyrinth seals 21C are provided on the outside of the pair of bearings 22 described above. The labyrinth seals 21C prevent hydraulic fluid from leaking to the outside. The hydraulic fluid captured by the labyrinth seals 21C is discharged to the lower body 23 through a communication hole or the like. However, since the labyrinth seals 21C have a small gap, they are connected to the outside air. Therefore, it is possible to discharge air to the outside through the labyrinth seals 21C.

[0016] As shown in Figures 1A and 1B, the base 2 is provided with first ports 2AR, 2AL and second ports 2BR, 2BL, respectively, configured to allow the supply and discharge of hydraulic fluid. As shown in Figure 3A, the first ports 2AR, 2AL each communicate with a first connecting passage 10A adjacent to the gap 10 in the opposing region. In this embodiment, the first connecting passage 10A is a groove formed around the entire circumference of the inner surface of the base 2. The first connecting passage 10A communicates with a first passage 40A via a first inlet 41A. Also, as shown in Figure 3B, the second ports 2BR, 2BL each communicate with a second connecting passage 10B adjacent to the gap 10 in the opposing region. In this embodiment, the second connecting passage 10B is also a groove formed around the entire circumference of the inner surface of the base 2. The second connecting passage 10B communicates with a second passage 40B via a second inlet 41B.

[0017] As shown in Figure 2A, the first passage 40A communicates with the first cylinder chamber 33A. Therefore, hydraulic fluid can be supplied to the first cylinder chamber 33A via the first passage 40A, and hydraulic fluid can be discharged from the first cylinder chamber 33A. Similarly, the second passage 40B communicates with the second cylinder chamber 33B. Therefore, hydraulic fluid can be supplied to the second cylinder chamber 33B via the second passage 40B, and hydraulic fluid can be discharged from the second cylinder chamber 33B. The first passage 40A and the second passage 40B are each equipped with a first check valve 34A and a second check valve 34B. The first check valve 34A and the second check valve 34B are so-called check valves and are configured to maintain the pressure of the hydraulic fluid in the first cylinder chamber 33A and the second cylinder chamber 33B. The first check valve 34A and the second check valve 34B are each pilot-operated check valves, and the passage and blocking of hydraulic fluid can be controlled by pilot pressure. For example, the pressure of the hydraulic fluid acting on the supply port can be used as the pilot pressure to release the pressure holding of the check valve on the discharge side.

[0018] As shown in Figures 4A and 4B, the lower body 23 is connected to the sleeve portion 21 by bolts 23A. The hydraulic fluid from the gap 10 in the opposing region and its vicinity flows down into the lower body 23 through the first discharge hole 21A and the second discharge hole 21B. The first discharge hole 21A and the second discharge hole 21B are each located near the inside of the pair of bearings 22. In addition, a pair of communication holes are provided outside the first discharge hole 21A and the second discharge hole 21B, that is, near the outside of the pair of bearings 22, for discharging the hydraulic fluid captured by the labyrinth seal portion 21C. Through this pair of communication holes, the hydraulic fluid flows down from the area around the labyrinth seal portion 21C into the lower body 23. The lower body 23 functions as an oil reservoir that receives the hydraulic fluid discharged from the gap 10 and its vicinity. The hydraulic fluid received in the lower body 23 is discharged from the drain port 23B.

[0019] <Supplying and Discharging of Working Fluid (Hydraulic Oil / Air) to Rotating Cylinder 1> Figure 5 schematically shows a system (which may also be called a rotating cylinder system) for supplying and discharging working fluid (hydraulic oil / air) to and from the rotating cylinder 1. The hydraulic oil to be supplied to the rotating cylinder 1 is contained in a tank 12. The hydraulic oil in the tank 12 is sent to the hydraulic oil supply unit 14 by a pump 13. The hydraulic oil supply unit 14 has, for example, a switching valve such as a solenoid valve, and is configured to supply hydraulic oil to any one of the first ports 2AR, 2AL or the second ports 2BR, 2BL, and to receive hydraulic oil discharged from the other. In this embodiment, an example is shown in which hydraulic oil is supplied to the first port 2AL and hydraulic oil from the second port 2BL is received. Also, as shown in Figure 5, the second port 2BR is blocked by a plug, and the first port 2AR is connected to the air supply unit 15.

[0020] The air supply unit 15 is connected to a factory air source 15A, such as a compressor, and is configured to receive pressurized air from the factory air source 15A. The air supply unit 15 has a switching valve, a pressure control valve (such as a pressure reducing valve), a flow control valve, etc., and is capable of supplying pressurized air from the factory air source 15A at a desired pressure, through a desired flow path, and at a desired flow rate. The air supply unit 15 is connected to the first port 2AR via a check valve 15B. The check valve 15B is configured to be open when pressurized air is supplied from the air supply unit 15 to the first port 2AR, and closed at other times. Therefore, the check valve 15B prevents backflow of working fluid (hydraulic oil / air) from the first port 2AR to the air supply unit 15, and also makes it possible to control the air (e.g., switching control of air passage and blocking). Here, an example is shown in which the air supply unit 15 is connected to the base 2 via a check valve 15B, but the air supply unit 15 may also be connected to the base 2 via a switching valve such as a solenoid valve.

[0021] Furthermore, the hydraulic fluid discharged to the lower body 23 returns to the tank 12 via a drain port 23B and a drain hose or the like in a discharge path 11. A branch section 11A is provided in the middle of the discharge path 11, allowing air mixed with the hydraulic fluid to be discharged to the outside via an exhaust section 16 from the branch section 11A. The exhaust section 16 may be a simple outlet, but it is preferable to have a filter or the like to capture oil mist, etc.

[0022] <Operation of Rotary Cylinder 1 (How to Use Rotary Cylinder 1)> Here, an example of machining using the rotary cylinder 1, specifically lathe machining, will be explained. Initially, the rotary cylinder 1 is in a stopped state. First, in order to move the jaws of the chuck device to a position where they contact the workpiece, hydraulic fluid is supplied from the hydraulic fluid supply unit 14 to the first port 2AL at a predetermined pressure. The hydraulic fluid supplied to the first port 2AL is sent to the first cylinder chamber 33A via the first passage 40A, moving the piston 32 to the left side in Figure 2A. As a result, the hydraulic fluid in the second cylinder chamber 33B is pushed out and discharged to the second port 2BL and the discharge path 11 via the second passage 40B. The piston 32 moves to a predetermined position and stops. At this time, the jaws of the chuck device are gripping the workpiece. Simultaneously with the piston 32 stopping, a thrust force corresponding to the hydraulic pressure is generated in the rod, and the jaws grip the workpiece with the desired gripping force (first step). Even when the hydraulic pressure is high, the check valve 15B is functioning, so hydraulic fluid does not enter the air supply unit 15 from the first port 2AR via the first connecting passage 10A.

[0023] After the desired gripping force is obtained on the chuck device side, the supply of hydraulic fluid to the first port 2AL is stopped (second step). Since the first port 2AL is connected to the outside air via the first connecting passage 10A and the labyrinth seal portion 21C, the pressure in the first port 2AL becomes atmospheric pressure after the supply of hydraulic fluid is stopped. On the other hand, since the first check valve 34A is functioning, the hydraulic fluid pressure (oil pressure) in the first cylinder chamber 33A is maintained.

[0024] Subsequently, pressurized air is supplied from the air supply unit 15 to the first port 2AR. The pressure of the pressurized air should be set to a suitable pressure from, for example, a range of 0.15 MPa to 1.0 MPa. After the pressurized air supplied from the air supply unit 15 to the first port 2AR reaches the first connecting passage 10A, it spreads out on both sides in the direction along the rotation axis C, as shown in Figure 2B, and functions to expel the hydraulic fluid filling the gap 10 (third step). In Figure 2B, the state in which the pressurized air expels the hydraulic fluid from the gap 10 is indicated by a solid arrow, and the state in which the expelled hydraulic fluid is discharged to the lower body 23 is schematically indicated by a dashed arrow. After the discharge of the hydraulic fluid filling the gap 10 is complete, the supply of pressurized air may be stopped, but it is preferable to continue supplying pressurized air from the viewpoint of preventing nearby hydraulic fluid from entering the gap 10.

[0025] After the hydraulic fluid is removed from the gap 10, the rotation of the rotating body 3 is started. During lathe machining, the rotating body 3 rotates at high speed, for example, 100 to 10,000 revolutions per minute, but since the gap 10 is filled with air instead of hydraulic fluid, heat generation in the gap 10 is suppressed.

[0026] Here, we will briefly explain the principle of heat generation. When the rotating body 3 rotates, the hydraulic fluid in the gap 10 is sheared, and a resistive torque T is generated due to the viscous resistance of the hydraulic fluid. Almost 100% of the load due to this resistive torque is converted into heat. The amount of heat generated per unit time Q is expressed by the following formula. (T: resistive torque, ω: rotational speed, τ: shear stress, μ: viscosity of hydraulic fluid, h: shear radius gap, S: shear area, R: shear radius, L: total shear width)

[0027] For example, in the case of hydraulic fluid with viscosity grade 32, its viscosity is 0.073 [Pa·s] at 20°C, 0.043 [Pa·s] at 30°C, and 0.018 [Pa·s] at 50°C. On the other hand, air has a viscosity of 0.000018 [Pa·s] at 20°C, 0.000019 [Pa·s] at 30°C, and 0.000020 [Pa·s] at 50°C. Thus, in this invention, we focus on the fact that the viscosity of air is about 1 / 4000 (20°C) to 1 / 900 (50°C) of the viscosity of hydraulic fluid, and by filling the gap 10 with air, we suppress heat generation in the gap 10. However, although the calculation formula shows that the heat generation Q becomes less than 1 / 1000 of the conventional value because the hydraulic fluid is replaced with air and its viscosity is reduced to less than 1 / 1000, in reality, about 1 / 4 of the heat generation that would occur when the gap 10 is filled with hydraulic fluid remains. This is because heat remains in the pair of bearings 22, but even considering the heat generated by the bearings 22, the heat generation is reduced by about 75% compared to the conventional value. Note that the heat generation value described here is just one example obtained from an evaluation test, and the value will differ depending on the design of the rotating cylinder, the type of hydraulic fluid, the rotational speed, and other conditions.

[0028] As described above, according to this embodiment, the hydraulic fluid filling the gap 10 can be quickly discharged by pressurized air. Therefore, heat generation due to shear is effectively suppressed compared to the case where hydraulic fluid is present in the gap 10. Furthermore, heat generation due to shear can also be suppressed in existing rotary hydraulic cylinders by appropriately applying the air supply unit 15, etc.

[0029] <Second Embodiment> Next, the rotary cylinder 1A according to the second embodiment will be described with reference to Figures 6 to 10. The basic configuration of the rotary cylinder 1A is the same as that of the rotary cylinder 1 according to the first embodiment, so the explanation will be omitted. In the rotary cylinder 1A, as shown in Figure 6A, the first port 2A and the second port 2B are provided only on the right side when facing forward. The first port 2A and the second port 2B are provided at the lower part of the sleeve portion 21. On the other hand, as shown in Figure 6B, an exhaust port 16A is provided on the left side when facing forward. The exhaust port 16A is connected to the upper part of the lower body 23.

[0030] Furthermore, in the first embodiment of the rotary cylinder 1, the first connecting passage 10A and the second connecting passage 10B were grooves formed over the entire circumference of the inner surface of the base 2, whereas in the rotary cylinder 1A, the first connecting passage 10A and the second connecting passage 10B are grooves formed over the entire circumference of the outer surface of the rotating body 3. With this configuration, in the first connecting passage 10A and the second connecting passage 10B of the second embodiment, no concave areas where hydraulic fluid tends to accumulate are formed on the lower side of the opposing region. As a result, the discharge of hydraulic fluid from the gap 10 becomes smoother.

[0031] <First air supply port 2C, second air supply port 2D, and third air supply port 2E> As shown in Figure 7, a first air supply port 2C and a seal air supply section 20 are provided on the upper part of the sleeve section 21. In this embodiment, the seal air supply section 20 is composed of a second air supply port 2D and a third air supply port 2E, but is not limited to this. The first air supply port 2C is configured to supply pressurized air to the gap 10 from above. The second air supply port 2D and the third air supply port 2E are each configured to supply pressurized air to the labyrinth seal section 21C from above.

[0032] The first air supply port 2C is provided primarily to further shorten the time it takes for the hydraulic fluid to be discharged from the gap 10. As shown in Figures 8A and 8B, in this embodiment, pressurized air from the first air supply port 2C is supplied to a position between the first connecting passage 10A and the second connecting passage 10B in the direction along the rotation axis C. As shown in Figure 8B, the pressurized air from the first air supply port 2C spreads to both sides in the direction along the rotation axis C, functioning to expel the hydraulic fluid filling the gap 10. In Figure 8B, the state in which the pressurized air expels the hydraulic fluid is shown by solid arrows, and the state in which the expelled hydraulic fluid is discharged to the lower body 23 is schematically shown by dashed arrows.

[0033] The second air supply port 2D and the third air supply port 2E are provided primarily to prevent oil mist from leaking from the labyrinth seal portion 21C. The pressurized air supplied from the second air supply port 2D and the third air supply port 2E to the labyrinth seal portion 21C from the outside forms an airflow from the labyrinth seal portion 21C toward the bearing 22. Therefore, even if oil mist generated by the pressurized air from the first air supply port 2C diffuses toward the labyrinth seal portion 21C, it will be pushed back by the airflow formed by the pressurized air from the second air supply port 2D and the third air supply port 2E.

[0034] Pressurized air at a desired pressure is supplied from the air supply unit 15 to the first air supply port 2C, the second air supply port 2D, and the third air supply port 2E. The pressure of the pressurized air should be set to a suitable pressure from, for example, a range of 0.15 MPa to 1.0 MPa. If the oil mist that may be generated by the pressurized air from the first air supply port 2C does not leak to the outside from the labyrinth seal portion 21C, the supply of pressurized air from the second air supply port 2D and the third air supply port 2E may be stopped.

[0035] As shown in Figures 9A and 9B, since the exhaust port 16A is connected to the lower body 23, the air from the working fluid (hydraulic oil and air) discharged to the lower body 23 can be discharged to the outside through the exhaust port 16A. Since the exhaust port 16A is connected to the upper part of the lower body 23, hydraulic oil is less likely to leak from the exhaust port 16A. In particular, even if the hydraulic oil hits the inner wall of the lower body 23 and bounces back, it is less likely to splash to the location of the exhaust port 16A and less likely to leak to the outside from the exhaust port 16A.

[0036] <Supplying and Discharging of Working Fluid (Hydraulic Oil / Air) to Rotating Cylinder 1A> Figure 10 schematically shows a system for supplying and discharging working fluid (hydraulic oil / air) to and from the rotating cylinder 1A. The basic configuration of each part is generally the same as in the first embodiment.

[0037] The air supply unit 15 is connected to the first air supply port 2C via a check valve 15B. The check valve 15B may be built into the first air supply port 2C, or it may be placed at any position in the flow path between the first air supply port 2C and the air supply unit 15. The air supply unit 15 is also connected to the second air supply port 2D and the third air supply port 2E. Here, the configuration is shown in which the first air supply port 2C, the second air supply port 2D, and the third air supply port 2E are each exposed to the outside, but it is also possible to have only one opening exposed to the outside and to provide branched flow paths that communicate with each port as appropriate in the flow path inside the sleeve unit 21.

[0038] Furthermore, the exhaust section 16 is connected to the exhaust port 16A. In the lower body 23, air mixed with the hydraulic fluid may be discharged to the outside through the exhaust port 16A, but it is preferable to provide a member (such as a filter) in the exhaust section 16 to prevent the scattering of oil mist.

[0039] As described above, according to the rotary cylinder 1A of the second embodiment, pressurized air can be supplied to the gap 10 from the first air supply port 2C located directly above the gap 10, thus shortening the time required to remove the hydraulic fluid from the gap 10. Furthermore, if pressurized air is continuously supplied from the first air supply port 2C, it is difficult for new hydraulic fluid to enter the gap 10. In the second embodiment, since the configuration makes it difficult for hydraulic fluid to remain near the gap 10, the air supply from the first air supply port 2C can be stopped, but reliability can be increased by continuously supplying air at a reduced flow rate. Moreover, by starting the supply of pressurized air from the second air supply port 2D and the third air supply port 2E at the same time as or before starting the supply of pressurized air from the first air supply port 2C, leakage of oil mist from the labyrinth seal portion 21C is prevented.

[0040] In the second embodiment described above, an example was explained in which the first port 2A and the second port 2B are provided only on the right side when facing forward. However, as in the first embodiment, the first port 2A and the second port 2B may also be provided on both the left and right sides. In this case, it is advisable to take measures to prevent physical interference with the first port 2A and the second port 2B, such as adjusting the height position of the exhaust port 16A.

[0041] <Other Embodiments> ・Since the present invention only requires that hydraulic fluid be discharged from the gap 10 by supplying pressurized air to the gap 10 in the opposing region, various variations can be adopted for the configuration for supplying pressurized air. For example, a configuration can be adopted in which pressurized air is supplied from a confluence in the middle of the flow path for supplying hydraulic fluid. ・The check valve 15B may be replaced with a switching valve such as a solenoid valve. In that case, it is preferable to operate the switching valve when the hydraulic fluid in the gap 10 is at atmospheric pressure, and then supply pressurized air from the air supply unit 15. ・If the conditions are such that oil mist does not leak from the labyrinth seal unit 21C, the second air supply port 2D and the third air supply port 2E become unnecessary. ・Even if the pressure inside the cylinder chamber decreases while the rotating body 3 is rotating, a series of operations, such as supplying hydraulic fluid to increase the pressure and then discharging the hydraulic fluid from the gap with pressurized air, can be performed while the rotating body 3 is rotating. Furthermore, if some of the hydraulic fluid filling the gap 10 is replaced with air, the overall viscosity of the working fluid (hydraulic fluid and air) will decrease accordingly, and a heat generation suppression effect can be expected. For this reason, it is not always necessary to replace all of the hydraulic fluid in the gap 10 with air. The operation of the piston 32 described above is merely an example, and the direction of operation of the piston 32 and the method of supplying and discharging the hydraulic fluid may differ depending on the workpiece gripping configuration of the chuck device.

[0042] 1: Rotating cylinder, 2: Base, 3: Rotating body, 10: Gap, 10A: First connecting passage, 10B: Second connecting passage, 15: Air supply section

Claims

1. A hydraulic rotary cylinder comprising a base and a rotating body configured to rotate relative to the base, wherein an air supply unit is provided, a gap is provided in the opposing region where the rotating body and the base face each other, and the air supply unit is configured to supply pressurized air to the gap via the base.

2. A rotary cylinder according to claim 1, wherein the rotating body comprises a first cylinder chamber and a second cylinder chamber for applying hydraulic pressure to a piston, the base comprises a first port, a second port and a first air supply port, the first port and the second port are configured to supply and discharge hydraulic fluid to and from the first cylinder chamber and the second cylinder chamber, the opposing region is provided with a first connecting passage for connecting the first cylinder chamber and the first port and a second connecting passage for connecting the second cylinder chamber and the second port, and the first air supply port is configured to supply pressurized air to the gap.

3. A rotary cylinder according to claim 2, wherein the base comprises a pair of seal portions and a seal air supply portion, the pair of seal portions are respectively arranged on both sides of the gap in a direction along the rotation axis of the rotating body and are configured to prevent leakage of the hydraulic fluid, and the seal air supply portion is configured to supply pressurized air to the pair of seal portions from the outside in a direction along the rotation axis.

4. A rotary cylinder according to any one of claims 1 to 3, wherein the air supply unit is connected to the base via a check valve or a switching valve, and the check valve or the switching valve is configured to prevent backflow of a working fluid containing hydraulic oil and to control the air.

5. A method for using a rotary cylinder, comprising: the rotary cylinder comprising a rotating body, a base, and an air supply unit, the rotating body being configured to rotate relative to the base and having a piston built in, the base being configured to supply hydraulic fluid to the rotating body, a gap being provided in the opposing region where the rotating body and the base face each other, the air supply unit being configured to supply pressurized air to the gap, a first step of applying a predetermined oil pressure to the piston by supplying the hydraulic fluid to the rotating body via the base, a second step of stopping the supply of the hydraulic fluid to the rotating body while maintaining the state in which the piston is subjected to the predetermined oil pressure, and a third step of discharging the hydraulic fluid from the gap by supplying pressurized air from the air supply unit to the gap.

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