Rotating cylinder

Abstract

Provided is a rotating cylinder capable of handling the occurrence of a pressure drop of a working fluid in a cylinder chamber.　The present invention provides a rotating cylinder comprising a base and a rotating body configured to be rotatable relative to the base. The rotating body comprises a rotating body main body, a first piston, first and second cylinder chambers, first and second pressure holding valves, and a pressure adjustment unit. The pressure adjustment unit is connected to the first cylinder chamber and the second cylinder chamber, and is configured to at least partially mitigate a pressure drop of a working fluid when the pressure drop occurs in either the first cylinder chamber or the second cylinder chamber.

Description

Rotating cylinder

[0001] The present invention relates to a rotary cylinder installed in a machine tool.

[0002] Patent Document 1 discloses a rotary cylinder having a check valve built into the working fluid circuit for safety purposes, so that the pressure of the working fluid in the cylinder chamber does not drop suddenly even if the supply of working fluid is cut off due to a power outage or the like.

[0003] Japanese Patent Application Laid-Open No. 2018-024046

[0004] In the technology of Patent Document 1, if the sealing performance of the working fluid deteriorates and the supply of working fluid is cut off, the pressure in the cylinder chamber may suddenly drop. Also, if the pressure of the working fluid drops due to a malfunction of the pressure regulating valve or piping parts, or an incorrect setting of the pressure regulating valve, the check valve alone may not be enough to ensure safety. Another disadvantage is that it is not possible to detect a drop in pressure in the cylinder chamber.

[0005] The present invention has been made in view of the above circumstances, and aims to provide a rotary cylinder that can cope with the occurrence of a pressure drop of the working fluid in the cylinder chamber.

[0006] According to the present invention, the following inventions are provided: [1] A rotary cylinder including a base and a rotor configured to be rotatable relative to the base, the rotor including a rotor main body, a first piston, a first cylinder chamber, a second cylinder chamber, a first pressure retention valve, a second pressure retention valve, and a pressure adjustment unit, the first piston configured to be movable by supplying and discharging a working fluid to and from the first cylinder chamber and the second cylinder chamber, the first pressure retention valve and the second pressure retention valve configured to be able to retain the pressure of the working fluid supplied to the first cylinder chamber and the second cylinder chamber, respectively, and the pressure adjustment unit configured to alleviate at least a part of the pressure drop when a pressure drop of the working fluid occurs in at least one of the first cylinder chamber and the second cylinder chamber. [2] The rotary cylinder according to [1], wherein the pressure adjustment unit comprises a pressure adjustment passage, a second piston, and an elastic member, the pressure adjustment passage communicates with the first cylinder chamber and the second cylinder chamber, the second piston is slidably disposed within the pressure adjustment passage and has a head portion and a rod portion, the head portion divides the pressure adjustment passage into a first chamber communicating with the first cylinder chamber and a second chamber communicating with the second cylinder chamber, and the elastic member is configured to apply an elastic force to the second piston against displacement of the second piston. [3] The rotary cylinder according to [2], further comprising a position detection unit, the rod portion of the second piston has an extension portion extending outside the rotary body, the extension portion has a detection target portion, and the position detection unit is configured to detect the position of the detection target portion.[4] The rotary cylinder according to [1], wherein the first piston has a flange portion separating the first cylinder chamber and the second cylinder chamber, the pressure adjusting unit includes a second piston and an elastic member, the second piston is configured to operate by pressure received from the working fluid, has a head portion and a rod portion, the elastic member is configured to apply an elastic force to the second piston that resists displacement of the second piston, the head portion has a pressure receiving plate and a main shaft, the pressure receiving plate is configured so that a first pressure receiving surface and a second pressure receiving surface have different pressure receiving areas, and is disposed in at least one of the first cylinder chamber and the second cylinder chamber, the main shaft is connected to the first pressure receiving surface of the pressure receiving plate and is configured to be disposed in a state where it can slide in a through hole of the flange portion, and the center of gravity of the second piston is configured to coincide with the rotation axis of the rotating body. [5] The rotary cylinder according to [4], further comprising a detected part and a position detecting part, wherein the rod part is connected to the second pressure receiving surface of the pressure receiving plate and has an extending part extending outside the rotary body main body, the detected part is slidably supported on the rotary body main body, the extending part is configured to engage with the detected part, and the position detecting part is configured to detect the position of the detected part. [6] The rotary cylinder according to any one of [3] to [5], wherein the pressure adjusting part comprises a plurality of the elastic members, and the number of the elastic members that apply an elastic force to the second piston increases as the displacement of the second piston increases.

[0007] In the rotary cylinder of the present invention, when a pressure drop of the working fluid occurs in either the first cylinder chamber or the second cylinder chamber, the pressure adjustment unit at least partially alleviates this pressure drop, making it possible to deal with the occurrence of a pressure drop of the working fluid in the cylinder chamber of the rotary cylinder.

[0008] 2A and 2B are diagrams schematically illustrating a connection state of the rotary cylinder 1 according to the first embodiment of the present invention. FIG. 2A is a perspective view of the rotary cylinder 1 according to the first embodiment of the present invention, and FIG. 2B is a perspective view of the rotary cylinder 1 viewed from another angle. FIG. 2B is a side cross-sectional view illustrating the configuration of the rotary cylinder 1 of FIG. 2. FIG. 4A is a perspective view of the rotary cylinder 1 with a portion of the rotor main body 31 cut away for convenience of explaining the pressure adjustment unit 5, and FIG. 4B is a diagram illustrating the pressure adjustment unit 5 viewed from another angle. FIG. 5A is a diagram schematically illustrating a state of the pressure adjustment unit 5 when the pressures of the first cylinder chamber 33a and the second cylinder chamber 33b are balanced. FIG. 5B is a diagram schematically illustrating a state of the pressure adjustment unit 5 when the pressure of the first cylinder chamber 33a is greater than the pressure of the second cylinder chamber 33b. FIG. 5C is a diagram schematically illustrating a state of the pressure adjustment unit 5 when the pressure of the first cylinder chamber 33a is smaller than the pressure of the second cylinder chamber 33b. Fig. 6A is a perspective view of the rotary cylinder 1 according to a second embodiment of the present invention, and Fig. 6B is a perspective view of the rotary cylinder 1 viewed from another angle. Fig. 7A is a schematic diagram illustrating a third embodiment in which springs 53a1 and 53a2 are concentrically arranged in the first chamber 51a and springs 53b1 and 53b2 are concentrically arranged in the second chamber 51b. Fig. 7B is a diagram illustrating a state in which the pressure in the second cylinder chamber 33b is high and both springs 53a1 and 53a2 are compressed. Fig. 8A is a side cross-sectional view showing the arrangement of a second piston 50 according to a fourth embodiment, Fig. 8B is a perspective view showing the connection between the flange portion 32b of the first piston 32 and the second piston 50, and Fig. 8C is a perspective view showing the schematic configuration of the second piston 50.Figure 9A is a diagram showing a schematic state of the second piston 50 when the pressures in the first cylinder chamber 33a and the second cylinder chamber 33b are balanced, Figure 9B is a diagram showing the state of the springs 59a and 59b in Figure 9A, Figure 9C is a diagram showing a schematic state of the second piston 50 when the pressure in the first cylinder chamber 33a is greater than the pressure in the second cylinder chamber 33b, Figure 9D is a diagram showing the state of the springs 59a and 59b in Figure 9C, Figure 9E is a diagram showing a schematic state of the second piston 50 when the pressure in the first cylinder chamber 33a is less than the pressure in the second cylinder chamber 33b, and Figure 9F is a diagram showing the state of the springs 59a and 59b in Figure 9E. Fig. 10A is an exploded perspective view showing the configuration of a second piston 50a and a sensor dog 54e according to the fifth embodiment, and Fig. 10B is an exploded perspective view of the second piston 50a and the sensor dog 54e viewed from a different angle. Fig. 11A is a side cross-sectional view showing the connection state of the second piston 50a and the sensor dog 54e, and Fig. 11B is a side cross-sectional view showing the arrangement of the second piston 50a. Fig. 12A is a diagram showing the attachment state of the spring 59a, and Fig. 12B is a diagram showing the attachment state of the spring 59b. Fig. 13A is a perspective view showing the configuration of the second piston 50a, and Fig. 13B is a perspective view of the second piston 50a viewed from a different angle. 14A to 14C are diagrams illustrating the state in which the first abutment surface 43a, which is located at a shallow position in the insertion hole, abuts against the spring 59a, and FIG. 14D to 14F are diagrams illustrating the state in which the second abutment surface 44a, which is located at a deep position in the insertion hole, abuts against the spring 59a. FIG. 14A and FIG. 14D show the state in which the second piston 50a is separated from the front body 31a, FIG. 14B and FIG. 14E show the state in which the second piston 50a is close to the front body 31a, and FIG. 14C and FIG. 14F show the state in which the second piston 50a is even closer to the front body 31a.

[0009] The following describes embodiments of the present invention. The various features shown in the following embodiments can be combined with each other. Furthermore, each feature can be an invention independently.

[0010] 1 , the rotary cylinder 1 is used to operate a chuck device 10. The chuck device 10 includes a plurality of jaws 10a (only one jaw 10a is shown here for convenience) for gripping a workpiece to be lathed, for example. The rotary cylinder 1 is connected to a fluid supply unit 14 via a first hose 16a and a second hose 16b. The fluid supply unit 14 includes a hydraulic pump or the like capable of adjusting pressure, and is configured to supply a working fluid (e.g., hydraulic oil) in a tank 13 toward the rotary cylinder 1 at a set pressure.

[0011] A supply switching unit 15 capable of controlling opening and closing of a flow path using a plurality of valves or the like is provided between the liquid delivery unit 14 and the rotary cylinder 1. The supply switching unit 15 normally supplies the working fluid from the liquid delivery unit 14 to the rotary cylinder 1 via either a first hose 16a or a second hose 16b. The working fluid supplied via the first hose 16a is supplied to the first cylinder chamber 33a and generates a pressure that moves the first piston 32 backward in the axial direction (to the left in the figure). On the other hand, the working fluid supplied via the second hose 16b is supplied to the second cylinder chamber 33b and generates a pressure that moves the first piston 32 forward in the axial direction (to the right in the figure).

[0012] The forward / backward movement of the first piston 32 along the axial direction is transmitted to the chuck device 10 via the rod 11, etc., and becomes the driving force for the gripping / releasing operation of the jaws 10a. The rotating cylinder 1 is connected to a spindle (not shown) via a coupling portion, and rotates as the spindle rotates.

[0013] When the working fluid is supplied through the first hose 16a, the first cylinder chamber 33a reaches the desired pressure, and the second cylinder chamber 33b reaches atmospheric pressure. Typically, the supply of working fluid to the first port 2a (described later) continues even after the first cylinder chamber 33a reaches the desired pressure. The working fluid supplied to the first hose 16a passes through gaps in the rotary joint and returns to the tank 13 via the second hose 16b and the drain hose 17. Similarly, when the working fluid is supplied through the second hose 16b, the second cylinder chamber 33b reaches the desired pressure, and the first cylinder chamber 33a reaches atmospheric pressure. If the supply of working fluid to the second port 2b (described later) continues in this state, the working fluid passes through gaps in the rotary joint and returns to the tank 13 via the first hose 16a and the drain hose 17.

[0014] The purpose of this embodiment is to adjust the pressure (reduce pressure drop) and detect the pressure in the first cylinder chamber 33a and the second cylinder chamber 33b of the rotary cylinder 1 in order to ensure safe and proper operation of the chuck device 10. The configuration of the rotary cylinder 1 will be described in more detail below.

[0015] 2 and 3, the rotary cylinder 1 according to one embodiment of the present invention includes a base 2 and a rotor 3 configured to be rotatable relative to the base 2. The base 2 is normally connected to a machine tool so as to be in a substantially non-rotating state. The rotor 3 is fixed to a spindle of the machine tool and rotates about a rotation axis C in association with rotation of the spindle.

[0016] As shown in FIG. 3 , the rotor 3 incorporates a reciprocating first piston 32. The rotary cylinder 1 is configured to supply a working fluid for reciprocating the first piston 32 into the rotor 3 through the base 2. As shown in FIG. 2 , the base 2 is provided with a first port 2a and a second port 2b configured to enable the supply and discharge of the working fluid. As shown in FIG. 3 , the first port 2a and the second port 2b are provided in a radially opposing portion 1a where the base 2 and the rotor 3 are radially opposed. The working fluid is exchanged between the base 2 and the rotor 3 at the radially opposing portion 1a. Sealing members (e.g., O-rings) are provided between various components to prevent leakage of the working fluid.

[0017] <Rotating Body 3> As shown in Figure 3, the rotating body 3 includes a rotating body main body 31, a first piston 32, a first cylinder chamber 33a, a second cylinder chamber 33b, a first pressure retention valve 34a, and a second pressure retention valve 34b. The rotating body main body 31 includes a front body 31a, a rear body 31b, and a rear cap 31c. The rear body 31b is connected to the front body 31a by bolts or the like. The rear cap 31c is connected to the rear body 31b by bolt 31e. The rotating body main body 31 is fixed to the spindle by bolt 31f that passes through the front body 31a and the rear body 31b.

[0018] The first piston 32 is disposed in the accommodation space 31g of the rotating body main body 31 and is slidable in the direction of the rotation axis. The first piston 32 includes a cylindrical portion 32a, a flange portion 32b, and a connecting portion 32c. The accommodation space 31g includes a cylindrical space 31g1 and a flange space 31g2. The cylindrical portion 32a is accommodated in the cylindrical space 31g1, and the flange portion 32b is accommodated in the flange space 31g2. The flange space 31g2 is divided by the flange portion 32b into a first cylinder chamber 33a and a second cylinder chamber 33b. The first piston 32 is configured to be movable by supplying and discharging working fluid to and from the first cylinder chamber 33a and the second cylinder chamber 33b.

[0019] A pin 32d fixed to the flange portion 32b is inserted into a hole formed in the rotating body main body 31, allowing the first piston 32 to rotate integrally with the rotating body main body 31. 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 the chuck device 10 via a rod 11 or the like having a male threaded portion. The rod 11 is configured to transmit the reciprocating motion of the first piston 32 to the chuck device 10, allowing the jaws 10a to grip and release the grip of a workpiece.

[0020] The rotating body main body 31 is provided with a first flow path 31h1 connecting the first port 2a and the first cylinder chamber 33a, and a second flow path 31h2 connecting the second port 2b and the second cylinder chamber 33b. The first flow path 31h1 is connected to the first hose 16a via the first port 2a. The second flow path 31h2 is connected to the second hose 16b via the second port 2b. The first flow path 31h1 and the second flow path 31h2 enable the supply and discharge of working fluid to the first cylinder chamber 33a and the second cylinder chamber 33b. The first pressure retention valve 34a and the second pressure retention valve 34b are disposed in the first flow path 31h1 and the second flow path 31h2, respectively, and are configured to maintain the pressure of the working fluid in the first cylinder chamber 33a and the second cylinder chamber 33b. The first pressure retention valve 34a and the second pressure retention valve 34b are each configured as a pilot-operated check valve, and the passage and blocking of the working fluid can be controlled by pilot pressure. As the pilot pressure, for example, it is preferable to use the pressure of the hydraulic oil acting on the supply side port, and to use a configuration in which this acts to release the pressure retention of the pressure retention valve on the discharge side.

[0021] <Base 2> The base 2 includes a base body 21, bearings 22, and an oil reservoir 23. The base body 21 is cylindrical, and the bearings 22 are provided inside the base body 21. The rotating body 3 is supported by the pair of bearings 22 and is rotatable relative to the base 2. The area between the pair of bearings 22 forms the radially opposing portion 1a. In the radially opposing portion 1a, the base 2 and the rotating body 3 face each other without contacting each other, with a small gap between them.

[0022] The oil reservoir 23 is connected to the base body 21 by bolts (not shown). A discharge passage communicating with the oil reservoir 23 is provided in the base body 21, and a portion of the working fluid supplied through the first port 2a or the second port 2b is discharged from the discharge passage through a gap in the rotary joint at the radially opposing portion 1a. The working fluid discharged from the discharge passage to the oil reservoir 23 returns to the tank 13 via the drain hose 17. In principle, the first piston 32 does not move axially during the rotational operation of the rotary cylinder 1, but the supply and discharge of working fluid are continuous to ensure that the thrust of the rod 11 is maintained.

[0023] <Pressure Adjustment Unit 5> Next, the pressure adjustment unit 5 will be described using Figures 4 and 5. In Figures 4A and 4B, a portion of the rotating body main body 31 is cut away for convenience in order to show the pressure adjustment unit 5 built into the rotating body main body 31. The pressure adjustment unit 5 is connected to the first cylinder chamber 33a and the second cylinder chamber 33b. When a pressure drop of the working fluid occurs in either the first cylinder chamber 33a or the second cylinder chamber 33b, the pressure adjustment unit 5 is configured to alleviate at least a portion of this pressure drop.

[0024] 5A to 5C, the pressure adjustment unit 5 includes a pressure adjustment flow path 51, a second piston 52, and springs 53a and 53b. The pressure adjustment flow path 51 communicates with the first cylinder chamber 33a and the second cylinder chamber 33b. The second piston 52 is slidably disposed within the pressure adjustment flow path 51. The second piston 52 has a head portion 52a and a rod portion 52b. The head portion 52a divides the pressure adjustment flow path 51 into a first chamber 51a that communicates with the first cylinder chamber 33a and a second chamber 51b that communicates with the second cylinder chamber 33b.

[0025] The springs 53a and 53b are configured to apply an elastic force to the second piston 52 that resists displacement of the second piston 52. Here, the springs 53a and 53b correspond to the elastic members of the present invention. The springs 53a and 53b are compression springs and are disposed in the first chamber 51a and the second chamber 51b, respectively. The spring 53a is disposed so as to abut against the head portion 52a of the second piston 52 and the wall surface of the first chamber 51a that faces the head portion 52a. The spring 53b is disposed so as to abut against the head portion 52a of the second piston 52 and the wall surface of the second chamber 51b that faces the head portion 52a. In this embodiment, the springs 53a and 53b are disposed in a slightly compressed state, but they may also be disposed with a free length or with a slight gap provided. In addition, the springs 53a and 53b may be arranged in a constantly compressed state so that the second piston 52 does not enter a free length state regardless of the stroke position.

[0026] FIG. 5A shows a state in which the pressures in the first cylinder chamber 33a and the second cylinder chamber 33b are balanced (for example, both chambers are at atmospheric pressure).

[0027] For example, when the first piston 32 is retracted in the axial direction, as shown in Fig. 5B, working fluid is supplied to the first cylinder chamber 33a so that the pressure in the first cylinder chamber 33a reaches a desired pressure. As the pressure in the first cylinder chamber 33a increases, the pressure difference between the first cylinder chamber 33a and the second cylinder chamber 33b increases, generating a force that presses the head portion 52a of the second piston 52 from the first chamber 51a toward the second chamber 51b. As a result, the spring 53b in the second chamber 51b is compressed.

[0028] On the other hand, when the first piston 32 is advanced in the axial direction, as shown in Fig. 5C, working fluid is supplied to the second cylinder chamber 33b so that the pressure in the second cylinder chamber 33b reaches a desired pressure. As the pressure in the second cylinder chamber 33b increases, the pressure difference between the first cylinder chamber 33a and the second cylinder chamber 33b increases, generating a force that presses the head portion 52a of the second piston 52 from the second chamber 51b toward the first chamber 51a. As a result, the spring 53a in the first chamber 51a is compressed.

[0029] In the state shown in FIG. 5B or 5C , if a pressure drop occurs in the first cylinder chamber 33a or the second cylinder chamber 33b, where the desired pressure should be maintained, due to a power outage or other reason, the pressure adjustment unit 5 functions to mitigate the pressure drop. Specifically, when the pressure difference between the first cylinder chamber 33a and the second cylinder chamber 33b decreases, the compressed spring 53a or the spring 53b attempts to return to its original position. The restoring force of this spring 53a or the spring 53b presses the head portion 52a of the second piston 52, applying pressure to the second cylinder chamber 33b or the first cylinder chamber 33a. In other words, the pressure drop occurring in the first cylinder chamber 33a or the second cylinder chamber 33b is mitigated by the restoring force of the spring 53b or the spring 53a. In other words, even if hydraulic fluid leaks from the first cylinder chamber 33a or the second cylinder chamber 33b, the head portion 52a of the second piston 52 moves to compensate for the leaked volume. The volume compensation effect of the second piston 52 is particularly effective when an incompressible working fluid such as hydraulic oil is used.

[0030] Furthermore, the pressure adjusting unit 5 has not only a pressure maintaining function but also a pressure abnormality detecting function. A more detailed explanation will be given using Figures 5A to 5C. The rod portion 52b of the second piston 52 has an extension portion 52b1 that extends to the outside of the rotor main body 31. A sensor dog 54 (corresponding to the part to be detected) is attached to the extension portion 52b1. Here, the extension portion 52b1 is male-threaded, and the sensor dog 54 is fixed with two nuts, but the manner of fixation is not limited to this.

[0031] A sensor 55 (corresponding to a position detection unit) configured to detect the position of the sensor dog 54 is provided near the sensor dog 54. The sensor dog 54 rotates together with the spindle, but the sensor 55 detects the position of the sensor dog 54 in a non-contact manner at a stationary position. The sensor 55 may be an optical sensor, a linear sensor, a laser displacement meter, an image sensor, a proximity sensor, a magnetic sensor, or the like, as appropriate.

[0032] When the first cylinder chamber 33a and the second cylinder chamber 33b are at appropriate pressures, the second piston 52 moves to its intended position. The position of the second piston 52 can be determined by detecting the position of the sensor dog 54 with the sensor 55. Therefore, if a pressure abnormality occurs in the first cylinder chamber 33a and the second cylinder chamber 33b, this abnormality can be detected based on the position information of the sensor dog 54.

[0033] The pressure adjustment unit 5 is provided at a position inside the rotating body main body 31 so as not to interfere with the arrangement positions of the first flow path 31h1, the second flow path 31h2, the first pressure retention valve 34a, the second pressure retention valve 34b, etc. In this embodiment, four pressure adjustment units 5 are provided inside the rotating body main body 31. However, the number of pressure adjustment units 5 may be fewer than four (for example, one to three). Furthermore, five or more pressure adjustment units 5 may be provided as long as physical interference with the first flow path 31h1, the second flow path 31h2, the first pressure retention valve 34a, the second pressure retention valve 34b, etc. is avoided. Increasing the number of pressure adjustment units 5 improves the pressure retention performance as an accumulator that stores pressure in preparation for a pressure drop in the first cylinder chamber 33a and the second cylinder chamber 33b.

[0034] 6A and 6B, a rotary cylinder 1 according to a second embodiment will be described. In this embodiment, four pressure adjustment units 5 are also built into the rotor main body 31. However, in this embodiment, the same number of sensor dogs 54a to 54d as the pressure adjustment units 5 are provided. The sensor dogs 54a to 54d are independently attached to their corresponding pressure adjustment units 5. Furthermore, in each of the multiple pressure adjustment units 5, the springs 53b and 53a are configured to have different spring constants (corresponding to the elastic coefficients).

[0035] The position of the second piston 52 when the first cylinder chamber 33a and the second cylinder chamber 33b are at appropriate pressures, and the responsiveness of the second piston 52 to the pressure difference between the first cylinder chamber 33a and the second cylinder chamber 33b, can be adjusted by the spring constants of the springs 53a and 53b. As in this embodiment, the range of detectable pressures is increased by detecting the respective positions of the second pistons 52 in the multiple pressure adjustment units 5 using multiple sensor dogs 54a to 54d. Although the multiple sensor dogs 54a to 54d also rotate with the rotation of the spindle, the position information of a specific one of the sensor dogs 54a to 54d detected by the sensor 55 can be identified by analyzing continuous position detection data.

[0036] If only a spring with a large spring constant is used to detect a large pressure difference, it is conceivable that the second piston 52 will move only slightly or will not move at all when the pressure difference between the first cylinder chamber 33a and the second cylinder chamber 33b is small. However, in this embodiment, such a disadvantage does not occur, and it is possible to detect a wide range of pressure differences.

[0037] Third Embodiment In this embodiment, an example will be described in which a single pressure adjustment unit 5 is used to detect a wide range of pressure differences. Here, as shown in FIGS. 7A and 7B , two types of springs with different spring constants are arranged in the single pressure adjustment unit 5. Springs 53a1 and 53a2 are concentrically arranged in the first chamber 51a, and springs 53b1 and 53b2 are concentrically arranged in the second chamber 51b. The spring constants of the springs 53a1 and 53b1 are set to small values, while the spring constants of the springs 53a2 and 53b2 are set to large values. As shown in FIG. 7A , the head portion 52a of the second piston 52 abuts against the springs 53a1 and 53b1, while gaps are provided between the head portion 52a of the second piston 52 and the springs 53a2 and 53b2.

[0038] With this configuration, when the pressure difference between the first cylinder chamber 33a and the second cylinder chamber 33b is small, the force from the spring 53a1 or 53b1, which has a small spring constant, acts on the head portion 52a of the second piston 52. When the pressure difference between the first cylinder chamber 33a and the second cylinder chamber 33b increases, the forces from both the spring 53a1 and the spring 53a2, or both the spring 53b1 and the spring 53b2, act on the head portion 52a of the second piston 52. FIG. 7B shows a state in which the pressure in the second cylinder chamber 33b increases and both the spring 53a1 and the spring 53a2 are compressed. As shown in FIGS. 7A and 7B, as the displacement of the second piston 52 increases, the number of springs applying elastic force to the second piston 52 increases. In this way, in the third embodiment, a wide range of pressure differences can be detected using a single pressure adjustment unit 5.

[0039] <Fourth Embodiment> In the first to third embodiments, the second piston 52 is disposed near the outer peripheral surface of the rotating body main body 31. Generally, the farther the center of gravity of a rotating object is from the center of rotation, the more susceptible it is to the influence of centrifugal force. Therefore, when the rotating body main body 31 rotates at high speed, it is conceivable that the centrifugal force acting on the second piston 52 will increase. Furthermore, it is conceivable that the static friction caused by this centrifugal force will make it difficult for the second piston 52 to move when the pressure difference between the first cylinder chamber 33a and the second cylinder chamber 33b is small. If the second piston 52 becomes difficult to move, it will become difficult to detect the pressure difference between the first cylinder chamber 33a and the second cylinder chamber 33b based on the position of the sensor dog 54.

[0040] As shown in FIGS. 8A to 8C , this embodiment uses a second piston 50 having a different configuration from the second piston 52 described above. The second piston 50 is configured to operate under pressure from the working fluid and includes a pressure-receiving plate (here, a first annular plate 56 a and a second annular plate 56 b), a main shaft 57, a first thin shaft 58 a, and a second thin shaft 58 b. Springs 59 a and 59 b are disposed near the second piston 50. The springs 59 a and 59 b are configured to apply elastic force to the second piston 50 against the displacement of the second piston 50. The second piston 50 includes a head portion 50H formed by the first annular plate 56 a, the second annular plate 56 b, and the main shaft 57, and a rod portion 50L formed by the first thin shaft 58 a and the second thin shaft 58 b. Here, the pressure-receiving plate is formed by a pair of plates, the first annular plate 56 a and the second annular plate 56 b. However, the pressure plate is not limited to being composed of a pair of plates. For example, the pressure plate may be composed of one plate, or three or more plates. As long as the pressure plate has sufficient rigidity to withstand the centrifugal force of the rotation of the rotary cylinder 1 and can perform smooth guiding operation when the second piston 50 and the sensor dog 54 are fixed, it is possible to arrange the pressure plate only in either the first cylinder chamber 33a or the second cylinder chamber 33b.

[0041] The first annular plate 56a and the second annular plate 56b are arranged parallel to each other at a predetermined interval, and their opposing surfaces are connected to both ends of multiple main shafts 57. Although three main shafts 57 are used here, this is not limiting. The main shafts 57 penetrate the flange portion 32b of the first piston 32 and are configured to be slidable in through-holes in the flange portion 32b. One end of the first thin shaft 58a is connected to the first annular plate 56a, and the other end is slidably inserted in a through-hole provided in the front body 31a of the rotor main body 31. One end of the second thin shaft 58b is connected to the second annular plate 56b, and the other end is slidably inserted in a through-hole provided in the rear body 31b of the rotor main body 31. The other end of the second thin shaft 58b has an extension portion 58b1 extending outward from the rear body 31b. A sensor dog 54 (corresponding to the detected portion) is fixed to the extension 58b1. That is, the second piston 50 is integrated with the sensor dog 54, and the position of the second piston 50 is determined by detecting the position of the sensor dog 54. The second piston 50 moves axially due to the pressure difference between the first cylinder chamber 33a and the second cylinder chamber 33b. At this time, the first annular plate 56a and the second annular plate 56b are guided by the front body 31a and the rear body 31b, respectively. However, for design convenience, the first annular plate 56a and the second annular plate 56b may be guided by the first piston 32. A spring 59a is disposed between the first annular plate 56a and the front body 31a, and a spring 59b is disposed between the second annular plate 56b and the rear body 31b. In this embodiment, six springs 59a and six springs 59b are disposed, but this is not limited to this. Here, the springs 59a and 59b are arranged so as to be constantly compressed, and apply a pressing force to the first annular plate 56a and the second annular plate 56b, respectively.

[0042] The thrust of the second piston 50 is determined by the total cross-sectional area of ​​the main shaft 57, the total cross-sectional area of ​​the first thin shaft 58a, the total cross-sectional area of ​​the second thin shaft 58b, and the pressure difference between the first cylinder chamber 33a and the second cylinder chamber 33b. Figures 9A and 9B show a state in which the pressures in the first cylinder chamber 33a and the second cylinder chamber 33b are the same. The second piston 50 is stationary at an intermediate position within its movable range. Figures 9C and 9D show a state in which the pressure in the first cylinder chamber 33a is higher than the pressure in the second cylinder chamber 33b. Within the first cylinder chamber 33a, the pressure within the chamber is applied to both main surfaces of the first annular plate 56a. However, the pressure-receiving area to which the pressure is applied is larger on the main surface connected to the first thin shaft 58a (the second pressure-receiving surface 56a2) than on the main surface connected to the main shaft 57 (the first pressure-receiving surface 56a1). As a result, the force applied to the second pressure-receiving surface 56a2 of the first annular plate 56a becomes greater, and the second piston 50 moves leftward in the drawing. Note that, under the same circumstances, if the diameters of the main shaft 57 and the first thin shaft 58a are reversed, the size of the pressure-receiving area is reversed, and the second piston 50 moves in the opposite direction (rightward in the drawing) from the above case.

[0043] 9E and 9F show a state in which the pressure in the second cylinder chamber 33b is higher than the pressure in the first cylinder chamber 33a. In the second cylinder chamber 33b, the pressure in the chamber is applied to both main surfaces of the second annular plate 56b. However, the pressure-receiving area to which the pressure is applied is larger on the main surface connected to the second thin shaft 58b (second pressure-receiving surface 56b2) than on the main surface connected to the main shaft 57 (first pressure-receiving surface 56b1). As a result, the force applied to the second pressure-receiving surface 56b2 of the second annular plate 56b is greater, and the second piston 50 moves to the right in the figures.

[0044] In this embodiment, the total cross-sectional area of ​​the main shaft 57 is configured to be approximately twice the total cross-sectional area of ​​the first thin shaft 58a and the total cross-sectional area of ​​the second thin shaft 58b, but is not limited to this. The greater the difference between the total cross-sectional area of ​​the main shaft 57 and the total cross-sectional area of ​​the first thin shaft 58a and the total cross-sectional area of ​​the second thin shaft 58b, the greater the difference in area between the first pressure-receiving surfaces 56a1, 56b1 and the second pressure-receiving surfaces 56a2, 56b2, and the thrust of the second piston 50 increases. On the other hand, the smaller the difference between the total cross-sectional area of ​​the main shaft 57 and the total cross-sectional area of ​​the first thin shaft 58a and the total cross-sectional area of ​​the second thin shaft 58b, the smaller the difference in area between the first pressure-receiving surfaces 56a1, 56b1 and the second pressure-receiving surfaces 56a2, 56b2, and the thrust of the second piston 50 decreases. Also, here, the main shaft 57, the first thin shaft 58a, and the second thin shaft 58b are arranged coaxially, but even if they are not arranged coaxially, there is no particular problem with the operation of the second piston 50. Furthermore, because the thrust force is determined by the sum of the cross-sectional areas of the main shaft 57, the first thin shaft 58a, and the second thin shaft 58b, the numbers of main shafts 57, first thin shafts 58a, and second thin shafts 58b may vary depending on the design.

[0045] The operation of the second piston 50 when a pressure drop occurs in the first cylinder chamber 33a or the second cylinder chamber 33b will be briefly described below. As described above, the second piston 50 moves due to a thrust from the higher-pressure side of the first cylinder chamber 33a or the second cylinder chamber 33b to the lower-pressure side. When a pressure drop occurs in the first cylinder chamber 33a or the second cylinder chamber 33b, the compressed spring 59a or the spring 59b attempts to return to its original position. The restoring force of this spring 59a or the spring 59b pushes back the second piston 50 (particularly the main shaft 57), thereby partially or completely mitigating the pressure drop that occurs in the first cylinder chamber 33a or the second cylinder chamber 33b.

[0046] The position of the second piston 50 can be detected by detecting the position of the sensor dog 54. Moreover, because the center of gravity of the second piston 50 is configured to coincide with the rotation axis C of the rotating body 3, it is hardly affected by centrifugal force even when the rotating body 3 is rotating at high speed. As a result, the second piston 50 moves smoothly in accordance with the pressure difference between the first cylinder chamber 33a and the second cylinder chamber 33b, making it possible to more reliably detect the pressures in the first cylinder chamber 33a and the second cylinder chamber 33b and the occurrence of abnormalities even when the rotating body 3 is rotating at high speed. Furthermore, because the first annular plate 56a and the second annular plate 56b are guided by the front body 31a and the rear body 31b at separate positions, the operation of the second piston 50 is stable.

[0047] Fifth Embodiment Next, a second piston 50a according to a fifth embodiment will be described using Figures 10 to 14. As shown in Figures 10A and 10B, the basic configuration of the second piston 50a is the same as that of the second piston 50 according to the fourth embodiment described above. However, while the second piston 50 has the sensor dog 54 fixed to the end of the second thin shaft 58b, this embodiment employs a configuration in which the sensor dog 54e moves in conjunction with the second piston 50a by engaging the second thin shaft 58b of the second piston 50a with the sensor dog 54e.

[0048] The second piston 50a is also provided with a first annular plate 56a and a second annular plate 56b, each configured so that the first and second pressure-receiving surfaces have different pressure-receiving areas. The main shaft 57 is attached to the first pressure-receiving surface side of the first annular plate 56a and the second annular plate 56b, and a first thin shaft 58a and a second thin shaft 58b are attached to the second pressure-receiving surface side of the first annular plate 56a and the second annular plate 56b. The second thin shaft 58b has an extension portion 58b2 that extends outward from the rear body 31b of the rotor main body 31. The extension portion 58b2 has an engagement groove 58b3. The engagement groove 58b3 is configured to engage with an engagement portion 54e2 provided on the sensor dog 54e. 10A and 10B, for the sake of convenience, the second piston 50a and the sensor dog 54e are shown separated from each other, but in reality, the engagement groove 58b3 and the engagement portion 54e2 are positioned so as to engage with each other in the axial direction.

[0049] A shaft portion 54e1 is fixed to the sensor dog 54e with a fastener such as a bolt. The shaft portion 54e1 is inserted into a hole provided in the rotating body main body 31, and the sensor dog 54e is supported so as to be slidable along the axial direction on the rotating body main body 31. More specifically, as shown in FIG. 11A , a receiving hole 40 for receiving the shaft portion 54e1 is provided in the rotating body main body 31. The depth of the receiving hole 40 is preferably greater than the length of the shaft portion 54e1. A slide bush (also referred to as a linear bush) 41 for smoothly sliding the shaft portion 54e1 in the axial direction is provided on the inner circumferential surface of the receiving hole 40.

[0050] In this embodiment, the sensor dog 54e, the shaft portion 54e1, and the engaging portion 54e2 are integrated to correspond to the detection target of the present invention. Although this embodiment employs a configuration in which three equally spaced shaft portions 54e1 are supported by three slide bushes 41, the number of shaft portions 54e1 and slide bushes 41 is not limited to three. The number of shaft portions 54e1 and slide bushes 41 can be increased or decreased as appropriate, taking into account available installation space, costs, and the like. Furthermore, because the combination of the shaft portion 54e1 and the slide bush 41 is intended to smoothly move the sensor dog 54e in the axial direction, a configuration other than the slide bush 41 can be employed as long as it performs the same function. For example, a cylindrical portion can be provided on the rotor main body 31 side (right side in FIG. 11 ) of the sensor dog 54e, and the inner circumferential surface of the cylindrical portion can be guided by the outer circumferential surface of the rotor main body 31.

[0051] By adopting this configuration, the sensor dog 54e and the second piston 50a can be smoothly interlocked without fixing the sensor dog 54e to the second piston 50a. Because the sensor dog 54e and the second piston 50a are not fixed and the sensor dog 54e is independently supported by the rotor main body 31, even if an external force, such as the sensor dog 54e's own weight when placed on a workbench, is applied to the sensor dog 54e during assembly, the external force is unlikely to be transmitted to the second piston 50a. This prevents the second piston 50a from being damaged by an external force applied to the sensor dog 54e. In particular, by providing some play in directions other than the axial direction at the engagement point between the engagement groove 58b3 and the engagement portion 54e2, it is possible to more effectively prevent external forces from being transmitted to the second piston 50a.

[0052] In this embodiment, springs 59a and 59b are also used to apply an elastic force to the second piston 50a that resists the displacement of the second piston 50a. The functions of the springs 59a and 59b are similar to those of the fourth embodiment, but the arrangement of the springs 59a and 59b is further improved. Specifically, as shown in FIGS. 12A and 12B , the spring 59a is supported by a pin 42a provided on the front body 31a. The spring 59b is supported by a pin 42b provided on the rear body 31b. The springs 59a and 59b are stably supported by the pins 42a and 42b, respectively. Specifically, the bodies of the pins 42a and 42b are inserted into the holes of the springs 59a and 59b, respectively, and the heads of the pins 42a and 42b are configured to be larger than the inner diameters of the holes of the springs 59a and 59b, respectively. Therefore, even when the springs 59a and 59b are in their natural length state where no external force is applied to them, they are unlikely to come off the pins 42a and 42b.

[0053] 13A, the second pressure-receiving surface 56a2 of the first annular plate 56a is provided with a first contact surface 43a and a second contact surface 44a that contact the spring 59a. Also, as shown in FIG. 13B, the second pressure-receiving surface 56b2 of the second annular plate 56b is provided with a first contact surface 43b and a second contact surface 44b that contact the spring 59b. Here, the first contact surface 43a, the first contact surface 43b, the second contact surface 44a, and the second contact surface 44b are disposed on steps in the insertion holes through which the pins 42a and 42b are inserted. The first contact surface 43a and the first contact surface 43b are formed at shallower positions in the insertion holes, while the second contact surface 44a and the second contact surface 44b are formed at deeper positions in the insertion holes.

[0054] 14A to 14C illustrate the contact state between the first contact surface 43a, which is located at a shallow position in the insertion hole, and the spring 59a. FIGS. 14D to 14F illustrate the contact state between the second contact surface 44a, which is located at a deep position in the insertion hole, and the spring 59a. FIGS. 14A to 14F are enlarged views of region X in FIG. 11B, but are simplified for ease of explanation. The spring 59a is configured to apply an elastic force to the first annular plate 56a of the second piston 50a that resists displacement of the second piston 50a (here, displacement in the direction toward the front body 31a). In FIGS. 14A and 14D, neither the first contact surface 43a nor the second contact surface 44a contacts the spring 59a.

[0055] 14B and 14E show a state in which the displacement of the second piston 50a has increased (here, the second piston 50a has approached the front body 31a). In this state, the first contact surface 43a is in contact with the spring 59a and applies an elastic force to the second piston 50a (FIG. 14B). Meanwhile, the second contact surface 44a has not yet contacted the spring 59a (FIG. 14E). In this way, until the displacement of the second piston 50a reaches a certain magnitude, the elastic force from some of the springs 59a is applied to the second piston 50a.

[0056] 14C and 14F show a state in which the displacement of the second piston 50a is further increased (here, the second piston 50a is closer to the front body 31a). In this state, the first contact surface 43a contacts the spring 59a, and the second contact surface 44a contacts the spring 59a. Therefore, the elastic force from all of the springs 59a is applied to the second piston 50a. As described above, in this embodiment, the number of springs 59a applying elastic force to the second piston 50a increases as the displacement of the second piston 50a increases. Similarly, on the rear body 31b side, as the second piston 50a approaches the rear body 31b, the first contact surface 43b and the spring 59b first contact each other, and then the second contact surface 44b and the spring 59b contact each other (not shown).

[0057] By applying the elastic force resisting the displacement of the second piston 50a in a stepped manner, accurate detection is possible, even at low pressures. Here, an example in which the step portion is formed at two different depths is shown, but three or more depths are also possible. Furthermore, the first contact surface 43a, the first contact surface 43b, the second contact surface 44a, and the second contact surface 44b are formed in a concave (hole) shape to make the rotary cylinder 1 as compact as possible in the axial direction. However, if there is no particular restriction on the axial size of the rotary cylinder 1, the first contact surfaces 43a, 43b and the second contact surfaces 44a, 44b may be formed in a convex shape. Furthermore, as in the third embodiment described above, it is also possible to adopt a configuration in which multiple springs with different spring constants are concentrically arranged (see FIGS. 7A and 7B ).

[0058] In this embodiment, the center of gravity of the second piston 50a coincides with the rotation axis C of the rotor 3, so that, as in the fourth embodiment, a decrease in the pressure detection accuracy of the second piston 50a can be prevented even during high-speed rotation. Here, the first annular plate 56a and the second annular plate 56b are guided by the front body 31a and the rear body 31b at separate positions, respectively, stabilizing the operation of the second piston 50a. It is also possible to adopt a configuration in which the first annular plate 56a and the second annular plate 56b are guided by the outer circumferential surface of the first piston 32. As in the fourth embodiment, the pressure-receiving plate is not limited to a pair of plates, the first annular plate 56a and the second annular plate 56b, but rather, a single plate or three or more plates can be used.

[0059] As described above, according to the first to fifth embodiments, the pressure difference between the first cylinder chamber 33 a and the second cylinder chamber 33 b can be appropriately measured. By detecting the positions of the sensor dogs (54, 54 a, 54 b, 54 c, 54 d, 54 e) using the sensor 55, it is possible to detect when the pressure drops below a set value, whether the rotary cylinder 1 is stopped or rotating, and to take action such as issuing a warning or stopping the machine, ensuring safety.

[0060] <Other Embodiments> In the above-described embodiment, a compression spring is used, but a tension spring may also be used. In this case, it is preferable to use a hook or the like to hook the head portion 52 a of the second piston 52 and the wall surface of the pressure adjustment flow path 51. Also, an elastic member other than a spring (e.g., rubber) may also be used.

[0061] 1: Rotating cylinder, 2: Base, 3: Rotating body, 5: Pressure adjusting section, 32: First piston, 33a: First cylinder chamber, 33b: Second cylinder chamber, 50: Second piston, 51: Pressure adjusting flow path, 51a: First chamber, 51b: Second chamber, 52: Second piston, 54: Sensor dog, 55: Sensor

Claims

1. A rotary cylinder comprising a base and a rotor configured to be rotatable relative to the base, wherein the rotor comprises a rotor main body, a first piston, a first cylinder chamber, a second cylinder chamber, a first pressure retention valve, a second pressure retention valve, and a pressure adjustment unit, wherein the first piston is configured to be movable by supplying and discharging working fluid to the first cylinder chamber and the second cylinder chamber, wherein the first pressure retention valve and the second pressure retention valve are configured to be able to retain the pressure of the working fluid supplied into the first cylinder chamber and the second cylinder chamber, respectively, and wherein the pressure adjustment unit is configured to alleviate at least a portion of the pressure drop when a pressure drop of the working fluid occurs in at least one of the first cylinder chamber and the second cylinder chamber.

2. A rotary cylinder as claimed in claim 1, wherein the pressure adjustment section comprises a pressure adjustment flow path, a second piston, and an elastic member, the pressure adjustment flow path communicates with the first cylinder chamber and the second cylinder chamber, the second piston is slidably disposed within the pressure adjustment flow path and has a head portion and a rod portion, the head portion divides the pressure adjustment flow path into a first chamber communicating with the first cylinder chamber and a second chamber communicating with the second cylinder chamber, and the elastic member is configured to apply an elastic force to the second piston that resists displacement of the second piston.

3. A rotary cylinder according to claim 2, further comprising a position detection unit, wherein the rod portion of the second piston has an extension portion extending to the outside of the rotating body main body, the extension portion having a detectable portion, and the position detection unit is configured to detect the position of the detectable portion.

4. A rotary cylinder as claimed in claim 1, wherein the first piston has a flange portion separating the first cylinder chamber and the second cylinder chamber, the pressure adjusting portion comprises a second piston and an elastic member, the second piston is configured to operate by pressure received from the working fluid and has a head portion and a rod portion, the elastic member is configured to apply an elastic force to the second piston that resists displacement of the second piston, the head portion has a pressure receiving plate and a main shaft, the pressure receiving plate is configured so that the pressure receiving areas of the first pressure receiving surface and the second pressure receiving surface are different and is disposed in at least one of the first cylinder chamber and the second cylinder chamber, the main shaft is connected to the first pressure receiving surface of the pressure receiving plate and is configured so as to be disposed in a state where it can slide in the through hole of the flange portion, and the rotary cylinder is configured so that the center of gravity of the second piston coincides with the rotation axis of the rotating body.

5. A rotary cylinder as claimed in claim 4, further comprising a detectable part and a position detecting part, wherein the rod part is connected to the second pressure receiving surface of the pressure receiving plate and has an extension part extending outside the rotating body, the detectable part is slidably supported on the rotating body, the extension part is configured to engage with the detectable part, and the position detecting part is configured to detect the position of the detectable part.

6. A rotary cylinder according to any one of claims 3 to 5, wherein the pressure adjusting section comprises a plurality of elastic members, and is configured so that the number of elastic members that apply an elastic force to the second piston increases as the displacement of the second piston increases.

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