Load sensitive valve with pressure relief structure

Abstract

The utility model relates to the technical field of load-sensitive valves, in particular to a load-sensitive valve with a pressure relief structure. Comprising a valve body, a transversely-arranged switching valve cavity is formed in the valve body, a valve rod is installed in the switching valve cavity in a sliding mode, the valve body is further provided with an oil inlet P, an oil return opening T, a working oil opening A, a working oil opening B and a pressure relief opening, the oil inlet P is communicated with the switching valve cavity through an oil inlet cavity, the working oil opening A is communicated with the switching valve cavity through a second working cavity, and the pressure relief opening is communicated with the switching valve cavity through a second working cavity. The working oil port B is communicated with the switching valve cavity through the first working cavity, the oil return port T is communicated with the switching valve cavity through the oil return cavity, the pressure relief port is communicated with the switching valve cavity through the pressure relief cavity, the valve body is further provided with a pressure control cavity, and the two ends of the pressure control cavity are both communicated with the switching valve cavity. By means of the structure, when the valve rod is switched to the neutral position or the floating position from the ascending position or the descending position, oil in the pressure control cavity can flow into the pressure relief opening, so that no pressure exists in the pressure control cavity, and the energy-saving effect of the device is improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to load sensitive valve technical field, concretely relates to a load sensitive valve with pressure relief structure. BACKGROUND

[0002] Load sensitive valve is a kind of hydraulic control element, its main function is to adjust the flow and pressure of hydraulic system according to the demand of load, to realize energy saving and efficient control.Load sensitive valve is fed back to valve by sensing the pressure, flow and power variation signal of load, to realize control function.

[0003] In prior art, load sensitive valve is mainly composed of P inlet, oil inlet cavity, control pressure cavity, A working oil port, first working cavity, B working oil port, second working cavity, T return oil port, return oil cavity, which are arranged on valve body, and the communication between each cavity is switched by controlling the position of valve rod.When valve rod is switched from ascending position or descending position to neutral position or floating position, since there is oil in control pressure cavity when in ascending position or descending position, and when valve rod is switched to neutral position or floating position, control pressure cavity will have oil residue, i.e., there is still pressure in control pressure cavity, and pressure shuttle valve in control pressure cavity will send pressure signal to variable pump through LS oil passage, thereby affecting the energy saving effect, so a pressure relief structure is needed to empty the oil in control pressure cavity when valve rod is in neutral position or floating position. SUMMARY

[0004] In view of the above problems, the utility model provides a load sensitive valve with pressure relief structure to solve the problem that there is still pressure in control pressure cavity when valve rod is switched to neutral position or floating position in prior art, thereby affecting the energy saving effect.

[0005] The utility model is implemented by using the following technical scheme: a load sensitive valve with pressure relief structure, comprising valve body, the valve body is equipped with transversely arranged switching valve cavity, the valve rod is slidably installed in switching valve cavity, the valve body is also equipped with P inlet, T return oil port, A working oil port, B working oil port, pressure relief port, P inlet is communicated with switching valve cavity through oil inlet cavity, A working oil port is communicated with switching valve cavity through second working cavity, B working oil port is communicated with switching valve cavity through first working cavity, T return oil port is communicated with switching valve cavity through return oil cavity, pressure relief port is communicated with switching valve cavity through pressure relief cavity, the valve body is also equipped with control pressure cavity, and both ends of control pressure cavity are communicated with switching valve cavity;

[0006] When the valve rod is in the neutral position, the oil inlet chamber, the oil return chamber, the first working chamber, the second working chamber and the pressure control chamber are not communicated with each other, and the pressure relief chamber is communicated with the pressure control chamber through the switching valve chamber; when the valve rod is in the floating position, the first working chamber, the second working chamber and the oil return chamber are communicated with each other through the switching valve chamber, and the pressure relief chamber is communicated with the pressure control chamber through the switching valve chamber.

[0007] Through the above structure, when the valve rod is switched from the rising position or the falling position to the neutral position or the floating position, the pressure control chamber is communicated with the pressure relief chamber, so that the oil in the pressure control chamber can flow into the pressure relief port through the switching valve chamber and the pressure relief chamber, thereby making the pressure in the pressure control chamber zero, and the flow pump will not continue to distribute oil into the valve body, thereby improving the energy saving effect of the device.

[0008] Preferably, the first pressure relief groove and the second pressure relief groove are arranged on the side wall of the valve rod, when the valve rod is in the neutral position, the first pressure relief groove is located between the pressure control chamber and the pressure relief chamber and communicates the two chambers; when the valve rod is in the floating position, the second pressure relief groove is located between the pressure control chamber and the pressure relief chamber and communicates the two chambers. Through the arrangement of the first pressure relief groove, when the valve rod is in the neutral position, the oil in the pressure control chamber can flow into the pressure relief chamber through the switching valve chamber and the first pressure relief groove; similarly, through the arrangement of the second pressure relief groove, when the valve rod is in the floating position, the oil in the pressure control chamber can flow into the pressure relief chamber through the switching valve chamber and the second pressure relief groove.

[0009] Preferably, the first pressure relief groove and the second pressure relief groove are square grooves, and two first pressure relief grooves and two second pressure relief grooves are arranged, and the two first pressure relief grooves and the two second pressure relief grooves are symmetrically arranged. Through the arrangement of the two square first pressure relief grooves and the second pressure relief grooves, the pressure relief grooves can reduce the occupied space as much as possible without affecting the pressure relief, and the processing is more convenient.

[0010] Preferably, two annular first lubricating grooves and two annular second lubricating grooves are arranged on the side wall of the valve rod, the two first lubricating grooves are respectively communicated with two ends of the first pressure relief groove, and the two second lubricating grooves are respectively communicated with two ends of the second pressure relief groove. Through the arrangement of the first lubricating groove and the second lubricating groove, the friction between the valve rod and the valve body can be reduced, and the stability of the device is improved.

[0011] Preferably, a pressure compensation valve is further arranged on the valve body, the pressure compensation valve comprises a compensation valve chamber arranged on the valve body, a compensation valve core is slidably arranged in the compensation valve chamber, a first spring is arranged between the compensation valve core and the compensation valve chamber, the P oil inlet is communicated with one end of the compensation valve chamber away from the first spring, the oil inlet chamber is communicated with the middle part of the compensation valve chamber, and the pressure control chamber is communicated with one end of the compensation valve chamber close to the first spring. Through the arrangement of the compensation valve chamber, the device can adjust the pressure of the oil chamber in the valve body, and the stability of the device is further improved.

[0012] Preferably, a hydraulic lock for controlling the on-off between the second working cavity and the switching valve cavity is further installed on the valve body, the hydraulic lock comprises a lock cavity arranged on the valve body, a first communication cavity in communication with the side of the lock cavity, and a second communication cavity in communication with the bottom of the lock cavity, the first communication cavity is in communication with the second working cavity, the bottom of the second communication cavity is in communication with the switching valve cavity, a lock core capable of sliding up and down and controlling the on-off between the first communication cavity and the second communication cavity is installed in the lock cavity, and a lock core lifting rod capable of sliding up and down is installed below the position of the lock core on the valve body. Through the arrangement of the lock core lifting rod, when the valve rod is in a floating state, the lock core lifting rod can be moved upward to lift the lock core, so that the second working cavity, the first communication cavity, the second communication cavity, the switching valve cavity, the oil return cavity and the first working cavity are in communication.

[0013] Preferably, a plug is fixedly installed on the top of the lock cavity, and a second spring is arranged between the bottom of the plug and the top of the lock core. Through the arrangement of the second spring, the lock core can be reset to cut off the first communication cavity and the second communication cavity again.

[0014] Preferably, a mounting hole is vertically arranged in the middle of the lock core, a plug ball capable of moving up and down is installed in the mounting hole, a baffle is installed at the top end of the mounting hole, and a through hole is arranged in the middle of the baffle; a top block capable of entering the mounting hole and lifting the plug ball is arranged at the top end of the lock core lifting rod. Through the arrangement of the mounting hole and the plug ball, the plug ball is lifted first before the lock core is opened, so that the flow of pilot oil is completed, the pressure is balanced, and the lock core can be more stable when it is opened.

[0015] Preferably, a third spring is arranged in the mounting hole and located between the plug ball and the baffle. Through the arrangement of the third spring, the plug ball can be reset to prevent the first communication cavity and the second communication cavity from being in communication.

[0016] Preferably, fourth and fifth grooves are arranged on the valve rod, when the valve rod is in a floating position, the second communication cavity is in communication with the oil return cavity through the fifth groove, and the first working cavity is in communication with the oil return cavity through the fourth groove. Through the arrangement of the fourth and fifth grooves, when the valve rod is in a floating state, the first working cavity can be in communication with the oil return cavity through the fourth groove, and the second communication cavity can be in communication with the oil return cavity through the fifth groove.

[0017] In summary, the beneficial effects of the present application are as follows:

[0018] Through the setting of the pressure relief port, the pressure relief port is communicated with the switching valve cavity through the pressure relief cavity, and when the valve rod is in the neutral position, the pressure relief cavity can be communicated with the pressure control cavity through the first pressure relief groove, and when the valve rod is in the floating position, the pressure relief cavity can be communicated with the pressure control cavity through the second pressure relief groove, so that the oil in the pressure control cavity can flow into the pressure relief port when the valve rod is in the neutral position or the floating position, so that the pressure in the pressure control cavity is zero, the pressure signal transmitted by the LS oil way is zero, that is, the flow pump will not deliver oil into the valve body, thereby improving the energy saving effect of the device. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 It is a sectional view of the valve body when the valve rod is in the neutral position in the utility model;

[0020] Figure 2 It is a sectional view of the valve body when the valve rod is in the neutral position in the utility model;

[0021] Figure 3 It is Figure 1 It is a local enlarged view of "A" area in the utility model;

[0022] Figure 4 It is Figure 2 It is a local enlarged view of "B" area in the utility model;

[0023] Figure 5 It is a structural schematic view of the valve rod in the utility model;

[0024] Figure 6 It is Figure 2 It is a local enlarged view of "C" area in the utility model.

[0025] In the drawing: 1-valve body; 10-switching valve cavity; 11-P oil inlet; 12-oil inlet cavity; 13-pressure control cavity; 14-B working oil port; 15-first working cavity; 16-A working oil port; 17-second working cavity; 18-T oil return port; 19-oil return cavity;

[0026] 2-valve rod; 21-first groove; 22-second groove; 23-third groove; 24-fourth groove; 25-fifth groove; 26-first lubricating groove; 27-first pressure relief groove; 28-second pressure relief groove; 29-second lubricating groove;

[0027] 31-first communication cavity; 32-second communication cavity; 41-pressure relief cavity; 42-pressure relief port;

[0028] 5-pressure compensating valve; 51-compensating valve cavity; 52-compensating valve core; 53-first spring;

[0029] 6 - hydraulic lock; 61 - plug; 62 - lock cavity; 63 - second spring; 64 - lock core; 65 - baffle; 66 - third spring; 67 - mounting hole; 68 - plug ball; 69 - lock core top rod. DETAILED DESCRIPTION

[0030] The specific embodiments of the present application will be further described in detail below with reference to the accompanying drawings and examples. The following examples are used to illustrate the present application, but not to limit the scope of the present application.

[0031] In the description of the present application, it should be understood that the terms "center", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0032] The following is a description of the preferred embodiments of the present application in conjunction with the accompanying drawings.

[0033] As shown in Figures 1 to 4 The present application provides a load-sensitive valve with a pressure relief structure, comprising a valve body 1, a switching valve cavity 10 is arranged transversely on the valve body 1, a valve rod 2 is slidably installed in the switching valve cavity 10, a P oil inlet 11, a T oil return port 18, an A working oil port 16, a B working oil port 14 and a pressure relief port 42 are further arranged on the valve body 1, the P oil inlet 11 is communicated with the switching valve cavity 10 through an oil inlet cavity 12, the A working oil port 16 is communicated with the switching valve cavity 10 through a second working cavity 17, the B working oil port 14 is communicated with the switching valve cavity 10 through a first working cavity 15, the T oil return port 18 is communicated with the switching valve cavity 10 through an oil return cavity 19, and the pressure relief port 42 is communicated with the switching valve cavity 10 through a pressure relief cavity 41, and a pressure control cavity 13 is further arranged on the valve body 1, both ends of the pressure control cavity 13 are communicated with the switching valve cavity 10.

[0034] As shown in Figure 2 , Figure 3 , Figure 4 As shown in the drawings, a first pressure relief groove 27 and a second pressure relief groove 28 are arranged on the side wall of the valve rod 2, specifically, the first pressure relief groove 27 and the second pressure relief groove 28 can be annular grooves or square grooves, since the oil in the pressure control cavity 13 is not much, the oil in the pressure control cavity 13 can be quickly drained through the square grooves, therefore, in order to reduce the space of the first pressure relief groove 27 and the second pressure relief groove 28 and make them better processed, the first pressure relief groove 27 and the second pressure relief groove 28 are arranged in square shape, two first pressure relief grooves 27 and two second pressure relief grooves 28 are arranged, and the two first pressure relief grooves 27 and the two second pressure relief grooves 28 are symmetrically arranged.

[0035] In addition, two annular first lubricating grooves 26 and two annular second lubricating grooves 29 are arranged on the side wall of the valve rod 2, the two first lubricating grooves 26 are respectively communicated with two ends of the first pressure relief groove 27, and the two second lubricating grooves 29 are respectively communicated with two ends of the second pressure relief groove 28. When the valve rod 2 is in the neutral position, oil enters the first lubricating groove 26, when the valve rod 2 is in the floating position, oil enters the second lubricating groove 29, and when oil enters the first lubricating groove 26 and the second lubricating groove 29, the friction between the valve rod 2 and the valve body 1 is reduced.

[0036] The valve rod 2 is provided with a first groove 21, a second groove 22, a third groove 23, a fourth groove 24 and a fifth groove 25. The valve rod 2 in the device has four position states, i.e. the neutral position, the rising position, the falling position and the floating position.

[0037] When the valve rod 2 is in the rising position, the oil inlet chamber 12 is communicated with the first end of the control pressure chamber 13 through the first groove 21, the second end of the control pressure chamber 13 is communicated with the second communication chamber 32 through the fifth groove 25, and the first working chamber 15 is communicated with the oil return chamber 19 through the third groove 23; when the valve rod 2 is in the falling position, the oil inlet chamber 12 is communicated with the first working chamber 15 through the second groove 22, and the second communication chamber 32 is communicated with the oil return chamber 19 through the fifth groove 25; when the valve rod is in the neutral position, the oil inlet chamber 12, the oil return chamber 19, the first working chamber 15, the second working chamber 17 and the control pressure chamber 13 are not communicated with each other; when the valve rod 2 is in the floating position, the first working chamber 15 is communicated with the oil return chamber 19 through the fourth groove 24, and the second communication chamber 32 is communicated with the oil return chamber 19 through the fifth groove 25. The communication between the above-mentioned chambers belongs to the prior art and is not the invention point of the present application, and is not related to the invention point of the present application when the valve rod 2 is in the rising position or the falling position, so the drawings are not set.

[0038] The main invention point of the present application is that when the valve rod 2 is in the neutral position, the pressure relief chamber 41 is communicated with the control pressure chamber 13 through the first pressure relief groove 27, and when the valve rod 2 is in the floating position, the pressure relief chamber 41 is communicated with the control pressure chamber 13 through the second pressure relief groove 28. By communicating the control pressure chamber 13 with the pressure relief chamber 41, when the valve rod 2 is in the neutral position or the floating position, the oil in the control pressure chamber 13 can flow into the pressure relief port 42, so that the oil in the control pressure chamber 13 is reduced to zero, the LS oil passage does not transmit pressure signals, the flow pump no longer controls the flow of oil to the valve body 1, and the energy-saving effect of the device is better.

[0039] The valve body 1 is further provided with a pressure compensation valve 5, which comprises a compensation valve cavity 51 arranged on the valve body 1, a compensation valve core 52 slidingly arranged in the compensation valve cavity 51, a first spring 53 arranged between the compensation valve core 52 and the compensation valve cavity 51, the P oil inlet 11 being in communication with one end of the compensation valve cavity 51 away from the first spring 53, the oil inlet cavity 12 being in communication with the middle part of the compensation valve cavity 51, and the pressure control cavity 13 being in communication with the other end of the compensation valve cavity 51 close to the first spring 53.

[0040] When the P oil inlet 11 is balanced, the pressure at the P oil inlet 11 is equal to the elastic force of the first spring 53 plus the pressure of the pressure control cavity 13, and when the pressure in the pressure control cavity 13 is zero, the pressure of the P oil inlet 11 is greater than the elastic force of the first spring 53, at which time the compensation valve core 52 moves away from the P oil inlet 11, thereby cutting off the communication between the P oil inlet 11 and the oil inlet cavity 12, so that the oil cannot flow into the valve body, thereby improving the energy saving effect of the device. In addition, the pressure compensation valve 5 can also adjust the stability of the oil pressure in the valve body 1, thereby improving the control effect of the device.

[0041] The valve body 1 is further provided with a hydraulic lock 6 for controlling the communication between the second working cavity 17 and the switching valve cavity 10, which comprises a lock cavity 62 arranged on the valve body 1, a first communication cavity 31 in communication with the side of the lock cavity 62, and a second communication cavity 32 in communication with the bottom of the lock cavity 62, the first communication cavity 31 being in communication with the second working cavity 17, and the bottom of the second communication cavity 32 being in communication with the switching valve cavity 10, a lock core 64 being slidingly arranged in the lock cavity 62 and capable of controlling the communication between the first communication cavity 31 and the second communication cavity 32, and a lock core top rod 69 being slidingly arranged below the lock core 64.

[0042] The bottom of the lock core top rod 69 is provided with a slope, when the valve rod 2 is in the neutral position, the bottom of the lock core top rod 69 is located at the lowermost part of the slope, when the valve rod 2 moves to the up position or the floating position, the lock core top rod 69 is lifted up to lift the lock core 64, thereby making the first communication cavity 31 and the second communication cavity 32 communicate, in order to make the lock core top rod 69 be lifted up by the valve rod 2 more conveniently, the bottom of the lock core top rod 69 is provided with a spherical surface; when the valve rod 2 moves to the down position, the lock core top rod 69 is lifted up by the oil pressure.

[0043] In order to facilitate the reset of the lock core 64, a plug 61 is fixedly arranged on the top of the lock cavity 62, and a second spring 63 is arranged between the bottom of the plug 61 and the top of the lock core 64.

[0044] A mounting hole 67 is vertically provided in the middle of the lock cylinder 64. A ball stop 68 that can move up and down is installed in the mounting hole 67. A baffle 65 is installed at the top of the mounting hole 67. A through hole is provided in the middle of the baffle 65. A top block is provided at the top of the lock cylinder push rod 69 that can enter the mounting hole 67 and lift the ball stop 68.

[0045] In order to reset the ball stopper 68, a third spring 66 is provided in the mounting hole 67, and the third spring 66 is located between the ball stopper 68 and the baffle 65.

[0046] The above description is only a preferred embodiment of the present utility model. It should be noted that for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of the present utility model, and these improvements and substitutions should also be considered within the protection scope of the present utility model.

Claims

1. A load sensitive valve with pressure relief structure, comprising a valve body (1), a transversely arranged switching valve cavity (10) is arranged on the valve body (1), a valve rod (2) is slidably installed in the switching valve cavity (10), characterized in that, The valve body (1) is further provided with a P oil inlet (11), a T oil return port (18), an A working oil port (16), a B working oil port (14), and a pressure relief port (42). The P oil inlet (11) is communicated with the switching valve cavity (10) through an oil inlet cavity (12). The A working oil port (16) is communicated with the switching valve cavity (10) through a second working cavity (17). The B working oil port (14) is communicated with the switching valve cavity (10) through a first working cavity (15). The T oil return port (18) is communicated with the switching valve cavity (10) through an oil return cavity (19). The pressure relief port (42) is communicated with the switching valve cavity (10) through a pressure relief cavity (41). The valve body (1) is further provided with a pressure control cavity (13), and both ends of the pressure control cavity (13) are communicated with the switching valve cavity (10). When the valve rod (2) is in the neutral position, the oil inlet cavity (12), the oil return cavity (19), the first working cavity (15), the second working cavity (17), and the pressure control cavity (13) are not communicated with each other. The pressure relief cavity (41) is communicated with the pressure control cavity (13) through the switching valve cavity (10). When the valve rod (2) is in the floating position, the first working cavity (15), the second working cavity (17), and the oil return cavity (19) are communicated with each other through the switching valve cavity (10). The pressure relief cavity (41) is communicated with the pressure control cavity (13) through the switching valve cavity (10).

2. The load sensing valve with pressure relief structure according to claim 1, wherein, The side wall of the valve rod (2) is provided with a first pressure relief groove (27) and a second pressure relief groove (28). When the valve rod (2) is in the neutral position, the first pressure relief groove (27) is located between the pressure control cavity (13) and the pressure relief cavity (41) and communicates the two cavities. When the valve rod (2) is in the floating position, the second pressure relief groove (28) is located between the pressure control cavity (13) and the pressure relief cavity (41) and communicates the two cavities.

3. The load sensing valve with pressure relief structure according to claim 2, wherein, The first pressure relief groove (27) and the second pressure relief groove (28) are both square grooves. The first pressure relief groove (27) and the second pressure relief groove (28) are both provided with two. The two first pressure relief grooves (27) and the second pressure relief grooves (28) are symmetrically arranged.

4. The load sensing valve with pressure relief structure according to claim 3, wherein, The side wall of the valve rod (2) is provided with two annular first lubricating grooves (26) and two annular second lubricating grooves (29). The two first lubricating grooves (26) are respectively communicated with both ends of the first pressure relief groove (27). The two second lubricating grooves (29) are respectively communicated with both ends of the second pressure relief groove (28).

5. The load sensing valve with pressure relief structure according to claim 1, wherein, The valve body (1) is further provided with a pressure compensation valve (5). The pressure compensation valve (5) comprises a compensation valve cavity (51) arranged on the valve body (1). A compensation valve core (52) is slidably arranged in the compensation valve cavity (51). A first spring (53) is arranged between the compensation valve core (52) and the compensation valve cavity (51). The P oil inlet (11) is communicated with one end of the compensation valve cavity (51) away from the first spring (53). The oil inlet cavity (12) is communicated with the middle part of the compensation valve cavity (51). The pressure control cavity (13) is communicated with one end of the compensation valve cavity (51) close to the first spring (53).

6. The load sensing valve with pressure relief structure according to claim 1, wherein, The valve body (1) is further provided with a hydraulic lock (6) for controlling the connection and disconnection between the second working chamber (17) and the switching valve chamber (10). The hydraulic lock (6) comprises a lock chamber (62) arranged on the valve body (1). The valve body (1) is further provided with a first communication chamber (31) in communication with the side of the lock chamber (62), and a second communication chamber (32) in communication with the bottom of the lock chamber (62). The first communication chamber (31) is in communication with the second working chamber (17), and the bottom of the second communication chamber (32) is in communication with the switching valve chamber (10). A lock core (64) capable of sliding up and down is arranged in the lock chamber (62) to control the connection and disconnection between the first communication chamber (31) and the second communication chamber (32). A lock core top rod (69) capable of sliding up and down is arranged below the lock core (64) on the valve body (1).

7. The load sensing valve with pressure relief structure according to claim 6, wherein, A plug (61) is fixedly arranged on the top of the lock chamber (62). A second spring (63) is arranged between the bottom of the plug (61) and the top of the lock core (64).

8. The load sensing valve with pressure relief structure according to claim 7, wherein, A mounting hole (67) is vertically arranged in the middle of the lock core (64). A plug ball (68) capable of moving up and down is arranged in the mounting hole (67). A baffle (65) is arranged at the top of the mounting hole (67). A through hole is arranged in the middle of the baffle (65). The top end of the lock core top rod (69) is provided with a top block capable of entering the mounting hole (67) and lifting the plug ball (68).

9. The load sensing valve with pressure relief structure according to claim 8, wherein, A third spring (66) is arranged in the mounting hole (67) between the plug ball (68) and the baffle (65).

10. The load sensing valve with pressure relief structure according to claim 6, wherein, The valve rod (2) is provided with a fourth groove (24) and a fifth groove (25). When the valve rod (2) is in a floating position, the second communication chamber (32) is in communication with the oil return chamber (19) through the fifth groove (25), and the first working chamber (15) is in communication with the oil return chamber (19) through the fourth groove (24).

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