CN116085260A

CN116085260A - Device and method for adjusting internal volume ratio of compressor

Info

Publication number: CN116085260A
Application number: CN202211723360.5A
Authority: CN
Inventors: 钟仁志; 袁军; 林晓健
Original assignee: Xinlei Compressor Co Ltd
Current assignee: Xinlei Compressor Co Ltd
Priority date: 2022-12-30
Filing date: 2022-12-30
Publication date: 2023-05-09

Abstract

The invention relates to the field of compressors, in particular to an internal volume ratio adjusting device and method of a compressor, wherein the device comprises a machine body, a pair of rotors which are meshed with each other and are rotatably arranged in the machine body and used for compressing air, a slide valve which is arranged on the exhaust side of the rotors and is slidably arranged in a channel of the machine body and used for changing the size of a radial exhaust port, a pressure adjusting cavity is arranged at the end of the channel away from the exhaust side, an oil inlet hole for inflow of hydraulic oil and an oil outlet hole for outflow of the hydraulic oil are arranged in the pressure adjusting cavity, and the pressure of the hydraulic oil directly acts on the slide valve to balance the pressure at two ends of the slide valve and adjust the internal volume ratio. The invention adopts hydraulic oil to directly push the slide valve to move, so that the structure is simplified, the slide valve can be directly processed on the original machine body, and the cost is reduced. Through the opening and closing of the oil inlet hole and the oil outlet hole in the pressure adjusting cavity, the slide valve is moved, the slide valve can be accurately controlled at a required position, and the adjusted internal volume ratio is ensured to be accurate.

Description

Device and method for adjusting internal volume ratio of compressor

Technical Field

The invention relates to the field of compressors, in particular to a device and a method for adjusting the internal volume ratio of a compressor.

Background

A compressor is a fluid machine for lifting low-pressure gas to high-pressure gas, and as an example of a conventional screw compressor, the compressor includes a pair of female and male rotors provided in a cylinder body and engaged with each other, one side of the female and male rotors being an intake side and the other side being an exhaust side, and air is sucked from the intake side, compressed by the female and male rotors to form compressed air, and then discharged from the exhaust side.

The internal volume ratio is an important parameter of the screw compressor, and is defined as

Wherein V is _s For the volume value at which the interdental volume communicates with the vent, i.e. the volume value at the end of the compression process, V _d The volume value at the moment when the interdental volume is disconnected from the suction orifice, i.e. the volume value at the end of the suction process. The internal volume ratio is closely related to the design and actual conditions of the screw compressor, and this parameter needs to be adjusted frequently during the operation of the screw compressor in order to reduce energy consumption and improve operating conditions.

The Chinese patent application (CN 103470505A) discloses an energy and internal volume ratio integrated regulating mechanism of screw compressor, in which an internal volume ratio slide valve capable of moving along the axial direction of female rotor and male rotor is set on the exhaust side of female rotor and male rotor, and the left end of said slide valve is equipped with a guide bar, on which an oil piston is fixedly connected, and the oil piston is controlled by means of hydraulic oil to move so as to implement movement of internal volume ratio slide valve and change internal volume ratio V _i 。

However, the above structure has the following problems: first, in order to control the movement of the internal volume ratio slide valve by using the hydraulic cylinder, it is necessary to additionally install the hydraulic cylinder on the main body of the screw machine, so that the main body needs to be reserved for installation in design. Next, since the internal volume ratio spool is indirectly controlled to move by the movement of the piston, the position where the internal volume ratio spool is actually moved is restricted by the hydraulic oil in the hydraulic cylinder, and once the pressure of the hydraulic oil in the hydraulic cylinder changes, the internal volume ratio spool is immediately caused to move, so that the internal volume ratio deviates from a predetermined value, and quick return is not possible.

Disclosure of Invention

In order to solve the problem that the position of the internal volume ratio slide valve is difficult to accurately locate at the correct position when the internal volume ratio is regulated, the invention aims to provide the internal volume ratio regulating device and method of the compressor, firstly, the use of a hydraulic cylinder in the prior art is canceled, the internal volume ratio slide valve is directly controlled to move by hydraulic oil, and the space of a machine body is effectively utilized; secondly, an oil inlet hole for the hydraulic oil to enter and an oil outlet hole for the hydraulic oil to flow out are formed in the machine body, and the position of the oil outlet hole corresponds to the position of the required internal volume ratio exactly, so that the internal volume ratio sliding valve can be positioned at the correct position no matter how the pressure of the hydraulic oil changes.

For the purpose of the invention, the following technical scheme is adopted for implementation:

the utility model provides a compressor internal volume ratio adjusting device, includes the fuselage, intermeshing and rotation set up the fuselage in, be used for compressing a pair of rotor to the air, set up in the exhaust side of rotor and slide the passageway that sets up in the fuselage, be used for changing radial gas vent size's slide valve, the passageway keep away from the end of exhaust side and be provided with pressure regulation chamber, pressure regulation intracavity has the inlet port that supplies hydraulic oil inflow and supplies the oil outlet that hydraulic oil flows, the pressure of hydraulic oil directly acts on the slide valve, balances the pressure at slide valve both ends, adjusts internal volume ratio.

Preferably, the oil inlet holes are arranged on the side wall of the pressure regulating cavity far away from the exhaust side, and at least two oil outlet holes are arranged on the side wall of the pressure regulating cavity far away from the exhaust side, and at least one oil outlet hole is arranged on the bottom wall of the pressure regulating cavity; the oil inlet and the oil outlet are respectively provided with a corresponding oil way and a valve for controlling the opening and the closing of the oil way.

Preferably, the three oil outlets comprise a first oil outlet arranged on the side wall of the pressure regulating cavity far away from the exhaust side, a second oil outlet A and a second oil outlet B arranged on the bottom wall of the pressure regulating cavity, and the second oil outlet B is relatively closer to the exhaust side than the second oil outlet A.

Preferably, the two oil outlets comprise a third oil outlet arranged on the side wall of the pressure regulating cavity far away from the exhaust side, and a fourth oil outlet arranged on the bottom wall of the pressure regulating cavity.

A method for regulating internal volume ratio of compressor features that the hydraulic oil is introduced into pressure regulating cavity from oil inlet, the pressure is applied to the end of slide valve to push the slide valve to move until the oil outlet shielded by slide valve is exposed, and the hydraulic oil is discharged from said oil outlet to keep the slide valve at target position for regulating internal volume ratio.

A method for regulating the internal volume ratio of compressor features that the hydraulic oil is discharged from the oil outlet exposed outside the slide valve, so the slide valve is retracted to the position where the oil outlet is, and the internal volume ratio is regulated.

Compared with the prior art, the invention has the beneficial effects that: the slide valve is directly pushed to move by hydraulic oil, so that the hydraulic cylinder is not arranged like the prior art, the structure is simplified, the slide valve can be directly machined on the original machine body, and the cost is reduced. And through the switching of inlet port and oil outlet in the pressure regulating chamber, realize the removal of slide valve, can be with the accurate control of slide valve in required position, ensure that the internal volume ratio after the regulation is accurate.

Drawings

FIG. 1 is a schematic cross-sectional view of a low pressure stage internal volume ratio adjustment device.

FIG. 2 is a schematic cross-sectional view of the low pressure stage at an internal volume ratio of 1.5.

FIG. 3 is a schematic cross-sectional view of the low pressure stage at an internal volume ratio of 2.5.

FIG. 4 is a schematic cross-sectional view of the low pressure stage at an internal volume ratio of 3.3.

Fig. 5 is a schematic cross-sectional view of the low pressure stage at an internal volume ratio of 4.1.

FIG. 6 is a schematic cross-sectional view of a high pressure stage internal volume ratio adjustment device.

Fig. 7 is a schematic cross-sectional view of the high pressure stage at an internal volume ratio of 1.5.

Fig. 8 is a schematic cross-sectional view of the high pressure stage at an internal volume ratio of 2.5.

Fig. 9 is a schematic cross-sectional view of the high pressure stage at an internal volume ratio of 3.0.

Detailed Description

The present application describes a specific structure of an internal volume ratio adjusting device using a two-stage screw compressor as an example. The two-stage screw compressor is provided with a low-pressure stage compression mechanism and a high-pressure stage compression mechanism, air enters from the low-pressure stage, is primarily compressed by the low-pressure stage compression mechanism, enters into the high-pressure stage compression mechanism for compression again, and is finally discharged.

Fig. 1 shows a sectional view of a low pressure stage of a screw compressor, comprising a body 1, a pair of low pressure stage rotors 2 disposed inside the body 1 and engaged with each other, a first intake port 11 being provided at the top of the body 1 and the first intake port 11 being on the intake side of the low pressure stage rotors 2, a first exhaust port 12 being provided at the lower right end of the body 1 and the first exhaust port 12 being on the exhaust side of the low pressure stage rotors 2.

When the low pressure stage compression mechanism is operated, a motor (not shown) drives a pair of low pressure stage rotors 2 to rotate, so that external air enters the machine body 1 from the first air inlet 11 and is sucked into the inside of the pair of low pressure stage rotors 2, and as the pair of low pressure stage rotors 2 continue to rotate, the air gradually flows rightward while being compressed, and finally is discharged from the right end of the lower part of the low pressure stage rotors 2, so as to enter the first air outlet 12, and then flows to the high pressure stage.

It is noted that after the two low-pressure stage rotors 2 have engaged each other, the size of the opening on the exhaust side (also called radial exhaust port) is entirely defined by the geometry of the rotors themselves, and cannot be changed, so that the internal volume ratio is fixed. However, the environment in which the compressor is actually used is necessarily different from the design condition, so that the external pressure ratio and the internal volume ratio are generally not equal, which results in that the compressor cannot exert the full performance. The external pressure ratio is the ratio of the discharge pressure to the suction pressure. For low pressure stages, i.e. low pressure stage external pressure ratio

For the inter-stage pressure at the first exhaust port 12 +.>

And the suction pressure at the first inlet 11 +.>

Is a ratio of (2). For the high-pressure stage hereinafter, the high-pressure stage external pressure ratio +.>

At the second exhaust port and at the second intake port

Is a ratio of (2). When the external pressure ratio is equal to the internal volume ratio, the performance of the compressor is optimal; when the external pressure ratio is greater than the internal volume ratio, the compressor is under-compressed; when the external pressure ratio is less than the internal volume ratio, the compressor is in over-compression. Either under-compression or over-compression can affect the efficiency of the compressor.

In order to adjust the internal volume ratio so that the internal volume ratio approaches (preferably is equal to) the external pressure ratio to improve the performance of the compressor, as shown in fig. 1, a low-pressure stage spool valve 3 is further provided below the low-pressure stage rotor 2 (the structure of the low-pressure stage spool valve 3 itself is not limited, any spool valve structure in the prior art may be adopted), the main body 1 is provided with a first passage 13 for the low-pressure stage spool valve 3 to move left and right at a position where the low-pressure stage spool valve 3 is located, and a first pressure adjusting chamber 4 is formed between the left end of the low-pressure stage spool valve 3 and the main body 1, and the low-pressure stage spool valve 3 can be driven to move left and right in the first passage 13 by changing the pressure of the first pressure adjusting chamber 4, thereby adjusting the internal volume ratio.

When the low-pressure stage spool valve 3 moves to a position relatively close to the first discharge port 12, the radial discharge port is minimized, and the internal volume ratio of the compressor reaches a set maximum value. As the low pressure stage spool valve 3 moves away from the first exhaust port 12 (shown moving to the left in fig. 1), the radial exhaust port gradually increases so that the exhaust process starts in advance and the internal volume ratio gradually decreases. When the left end of the low-pressure stage slide valve 3 is connected to the inner wall of the left side of the body 1, the internal volume ratio of the compressor reaches a set minimum value. By adjusting the internal volume ratio to be adapted to the actual external pressure ratio, the over-compression can be reduced, thereby achieving an energy saving effect.

Unlike the structure of controlling the movement of the spool valve by the hydraulic cylinder in the prior art, in this embodiment, the hydraulic cylinder is not provided any more to control the movement of the spool valve, but the low-pressure stage spool valve 3 is directly controlled to move by hydraulic oil.

Specifically, as shown in fig. 2, the first pressure adjusting chamber 4 has a side wall (an inner wall far from the exhaust side, which is shown as a left end inner wall in fig. 2) and a bottom wall (a bottom surface inside the first pressure adjusting chamber 4), a first oil inlet hole 41 into which hydraulic oil enters is provided on the side wall of the first pressure adjusting chamber 4, a first oil outlet hole 42 through which hydraulic oil flows out is also provided on the side wall of the first pressure adjusting chamber 4, a second oil outlet hole 43 through which hydraulic oil flows out is provided on the bottom wall of the first pressure adjusting chamber 4, at least one of the second oil outlet holes 43 may be increased according to actual needs, and in this embodiment, two second oil outlet holes 43 are respectively referred to as a second oil outlet hole a431 and a second oil outlet hole B432, and the second oil outlet hole B432 is located on the right side of the first oil outlet hole a 431. As shown in fig. 2, the first oil inlet hole 41 is connected to a first oil inlet passage 4101, and a first valve 4102 (for example, a solenoid valve) for controlling opening and closing of the oil inlet passage 4101 is provided in the first oil inlet passage 4101. The first oil outlet hole 42 is connected to a first oil outlet passage 4201, and the first oil outlet passage 4201 is provided with a second valve 4202 for controlling the first oil outlet passage 4201 to open and close. The second oil outlet hole 43 is connected with a second oil outlet path, and a third valve for controlling the second oil outlet path to open and close is arranged on the second oil outlet path, in this embodiment, the second oil outlet path includes a second oil outlet path a4301 and a second oil outlet path B4302 which are connected with the second oil outlet hole a431 and the second oil outlet hole B432 respectively, and the third valve includes a third valve a for controlling the second oil outlet path a4301 to open and close and a third valve B for controlling the second oil outlet path B4302.

When the low-pressure stage spool valve 3 of the present embodiment moves, four different internal volume ratios of 1.5, 3.5, 3.3 and 4.1 can be formed, respectively, and how this is achieved will be described in order below. It should be noted that the specific value of the internal volume ratio may be changed according to actual needs, and only the position of the second oil outlet hole 43 needs to be changed accordingly.

Referring to fig. 2, when the second valve 4202 controls the first oil outlet passage 4201 to be opened and the remaining valves to be closed, the hydraulic oil in the first pressure adjusting chamber 4 may flow into the first oil outlet passage 4201 through the first oil outlet hole 42, and the low pressure stage spool 3 moves leftward due to the existence of the exhaust side pressure, and thus the hydraulic oil in the first pressure adjusting chamber 4 may be finally discharged all into the first oil outlet passage 4201, and the low pressure stage spool 3 is held at the leftmost side of the first passage 13, at which time the internal volume ratio is 1.5. It should be noted that at compressor start-up, the low pressure stage slide valve 3 should be in this position to ensure low load start-up. The low pressure stage slide valve 3 also needs to be placed in this position for a period of time when the compressor is shut down to ensure that it can start at low load at a later start.

Referring to fig. 3, when the first and third valves 4102 and a control the oil inlet passage 4101 and the second oil outlet passage a4301 to be opened, respectively, and the remaining valves are closed, hydraulic oil in the first oil inlet passage 4101 may enter the first pressure adjusting chamber 4 through the first oil inlet hole 41 to push the low-pressure stage spool 3 to move rightward until the left end of the low-pressure stage spool 3 moves to a position where the second oil outlet passage a431 is located, at which time hydraulic oil may flow into the second oil outlet passage a4301 through the second oil outlet passage a431 to hold the low-pressure stage spool 3 at this position, at which time the internal volume ratio is 2.5.

Referring to fig. 4, when the first and third valves 4102 and B control the oil feed passage 4101 and the second oil discharge passage B4302 to be opened, respectively, and the remaining valves are closed, hydraulic oil in the first oil feed passage 4101 may enter the first pressure adjusting chamber 4 through the first oil feed hole 41 to push the low-pressure stage spool 3 to move rightward until the left end of the low-pressure stage spool 3 moves to a position where the second oil discharge hole B432 is located, at which time hydraulic oil may flow into the second oil discharge passage B4302 through the second oil discharge hole B432 to hold the low-pressure stage spool 3 at the position where the internal volume ratio is 3.3.

Referring to fig. 5, when the first valve 4102 controls the oil feed passage 4101 to be opened and the remaining valves to be closed, hydraulic oil in the first oil feed passage 4101 may enter the first pressure adjusting chamber 4 through the first oil feed hole 41 to push the low pressure stage spool 3 to move rightward until the right end of the low pressure stage spool 3 abuts against the inner wall of the machine body 1, at which time the low pressure stage spool 3 is in the rightmost position, in which case high pressure hydraulic oil in the first oil feed passage 4101 is continuously injected into the first pressure adjusting chamber 4, and the low pressure stage spool 3 is held in this position by the pressures of the left and right sides of the low pressure stage spool 3, at which time the internal volume ratio is 4.1.

Fig. 6 shows a sectional view of a high pressure stage of a screw compressor, similar to a low pressure stage, including a body 1', a pair of high pressure stage rotors 2' provided inside the body 1' and engaged with each other, the body 1' being internally provided with a second air inlet 11' communicating with the low pressure stage, and the second air inlet 11' being on an intake side of the high pressure stage rotor 2', a lower right end of the body 1' being provided with a second air outlet 12', and the second air outlet 12' being on an exhaust side of the high pressure stage rotor 2'.

When the high-pressure stage compression mechanism is operated, the motor (not shown) drives the pair of high-pressure stage rotors 2 'to rotate, so that air compressed by the low-pressure stage enters the machine body 1 from the second air inlet 11', is sucked into the inside of the pair of high-pressure stage rotors 2', gradually flows rightward while being compressed along with the continued rotation of the pair of high-pressure stage rotors 2', and finally is discharged from the right end of the lower part of the high-pressure stage rotors 2', so as to enter the second air outlet 12'.

As in the case of the low pressure stage, as shown in fig. 6, a high pressure stage spool 3 'is provided at a lower portion of the high pressure stage rotor 2', a second passage 13 'through which the high pressure stage spool 3' moves left and right is provided in a position where the main body 1 'is located at the high pressure stage spool 3', and a second pressure adjusting chamber 4 'is formed between a left end of the high pressure stage spool 3' and the main body 1', and the high pressure stage spool 3' can be driven to move left and right in the second passage 13 'by changing the pressure of the second pressure adjusting chamber 4', thereby adjusting the internal volume ratio.

As shown in fig. 7, the second pressure adjusting chamber 4' also has a side wall and a bottom wall, the side wall of the second pressure adjusting chamber 4' is provided with a second oil inlet hole 41' for hydraulic oil to enter, the side wall of the second pressure adjusting chamber 4' is also provided with a third oil outlet hole 44 for hydraulic oil to flow out, the bottom wall of the second pressure adjusting chamber 4' is provided with a fourth oil outlet hole 45 for hydraulic oil to flow out, and the number of the fourth oil outlet holes 45 is at least one, and can be increased according to actual needs, in this embodiment, the number of the fourth oil outlet holes 45 is one. As shown in fig. 7, the second oil inlet hole 41' is connected to a second oil inlet passage 4101', and a fourth valve 4102' for controlling the opening and closing of the second oil inlet passage 4101' is provided in the second oil inlet passage 4101 '. The third oil outlet 44 is connected with a third oil outlet 4401, and the third oil outlet 4401 is provided with a fifth valve 4402 for controlling the third oil outlet 4401 to open and close. The fourth oil outlet hole 45 is connected with a fourth oil outlet path 4501, and a sixth valve 4502 for controlling the fourth oil outlet path 4501 to open and close is arranged on the fourth oil outlet path 4501.

In fig. 7, the second oil inlet passage 4101' and the third oil outlet passage 4401 partially overlap each other due to the view angle, and are actually independent passages.

When the high-pressure stage spool valve 3' of the present embodiment moves, three different internal volume ratios of 1.5, 2.5 and 3.0 are formed, respectively, and how this is achieved is described in order below.

Referring to fig. 7, when the fifth valve 4402 controls the third oil outlet passage 4401 to be opened and the remaining valves to be closed, the hydraulic oil in the second pressure regulating chamber 4' may flow into the third oil outlet passage 4401 through the third oil outlet hole 44, and the high-pressure stage spool 3' may move leftward due to the presence of the exhaust side pressure, so that the hydraulic oil in the second pressure regulating chamber 4' may be finally discharged into the third oil outlet passage 4401 entirely, and the high-pressure stage spool 3' may be held at the leftmost side of the second passage 13', at which time the internal volume ratio is 1.5. It should be noted that at compressor start-up, the low pressure stage slide valve 3 should be in this position to ensure low load start-up. The high pressure stage slide valve 3' also needs to be placed in this position for a period of time when the compressor is shut down to ensure that it can start at low load at a later start.

Referring to fig. 8, when the fourth valve 4102 'and the sixth valve 4502 control the second oil feed path 4101' and the fourth oil discharge path 4501 to be opened, respectively, and the remaining valves are closed, hydraulic oil in the second oil feed path 4101 'may enter the second pressure adjusting chamber 4' through the second oil feed hole 41', thereby pushing the high-pressure stage spool 3' to move rightward until the left end of the high-pressure stage spool 3 'moves to the position where the fourth oil discharge hole 45 is located, at which time hydraulic oil may flow into the fourth oil discharge path 4501 through the fourth oil discharge hole 45, thereby maintaining the high-pressure stage spool 3' at the position where the internal volume ratio is 2.5.

Referring to fig. 9, when the fourth valve 4102 'controls the second oil intake passage 4101 to be opened and the remaining valves to be closed, the hydraulic oil in the second oil intake passage 4101' may enter the second pressure adjusting chamber 4 'through the second oil intake hole 41' to push the high-pressure stage spool 3 'to move rightward until the right end of the high-pressure stage spool 3' abuts against the inner wall of the machine body 1', at which time the high-pressure stage spool 3' is at the rightmost position, in which case the hydraulic oil of high pressure in the second oil intake passage 4101 'is continuously injected into the second pressure adjusting chamber 4', and the high-pressure stage spool 3 'is maintained at this position by the pressures on the left and right sides of the high-pressure stage spool 3', at which time the internal volume ratio is 3.0.

The invention has the following technical effects: the slide valve is directly pushed to move by hydraulic oil, so that the hydraulic cylinder is not arranged like the prior art, the structure is simplified, the slide valve can be directly machined on the original machine body, and the cost is reduced. And through the switching of inlet port and oil outlet in the pressure regulating chamber, realize the removal of slide valve, can be with the accurate control of slide valve in required position, ensure that the internal volume ratio after the regulation is accurate.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art. The generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An internal volume ratio adjusting device of a compressor comprises a machine body (1; 1 '), a pair of rotors (2; 2 ') which are meshed with each other and are rotatably arranged in the machine body (1; 1 ') and used for compressing air, a slide valve (3; 3 ') which is arranged on the exhaust side of the rotors (2; 2 ') and is slidably arranged in a channel (13; 13 ') of the machine body (1; 1 ') and used for changing the size of a radial exhaust port, and the internal volume ratio adjusting device is characterized in that the end of the channel (13; 13 ') away from the exhaust side is provided with a pressure adjusting cavity (4; 4 '), an oil inlet hole (41; 41 ') for inflow of hydraulic oil and an oil outlet hole for outflow of the hydraulic oil are arranged in the pressure adjusting cavity (4; 4 '), and the pressure of the hydraulic oil directly acts on the slide valve (3; 3 ') to balance the pressure at two ends of the slide valve (3; 3 ') so as to adjust the internal volume ratio.

2. The compressor internal volume ratio adjusting device according to claim 1, wherein the oil inlet holes (41; 41 ') are provided in a side wall of the pressure adjusting chamber (4; 4') away from the exhaust side, and at least two of the oil outlet holes are provided, wherein at least one oil outlet hole is provided in a side wall of the pressure adjusting chamber away from the exhaust side, and at least one oil outlet hole is provided in a bottom wall of the pressure adjusting chamber; the oil inlet hole (41; 41') and the oil outlet hole are respectively provided with a corresponding oil way and a valve for controlling the opening and the closing of the oil way.

3. The compressor internal volume ratio adjusting device according to claim 2, wherein three of the oil outlet holes are provided, including a first oil outlet hole (42) provided in a side wall of the pressure adjusting chamber (4; 4') remote from the discharge side, a second oil outlet hole a (431) and a second oil outlet hole B (432) provided in a bottom wall of the pressure adjusting chamber, the second oil outlet hole B (432) being relatively closer to the discharge side than the second oil outlet hole a (431).

4. The compressor internal volume ratio adjusting device according to claim 2, wherein the two oil outlet holes include a third oil outlet hole (44) provided in a side wall of the pressure adjusting chamber (4; 4') remote from the discharge side, and a fourth oil outlet hole (45) provided in a bottom wall of the pressure adjusting chamber.

5. A method for adjusting the internal volume ratio of a compressor is characterized in that hydraulic oil enters a pressure adjusting cavity (4; 4 ') from an oil inlet hole (41; 41'), pressure is applied to the end part of a slide valve (3; 3 '), the slide valve (3; 3') is pushed to move until an oil outlet hole originally shielded by the slide valve (3; 3 ') is exposed, the hydraulic oil is discharged from the oil outlet hole, and the slide valve (3; 3') is kept at a target position, so that the internal volume ratio is adjusted.

6. A method for adjusting the internal volume ratio of a compressor is characterized in that hydraulic oil is discharged from an oil outlet hole exposed outside a slide valve (3; 3 '), so that the slide valve (3; 3') is retracted to a position where the oil outlet hole is located, and the internal volume ratio is adjusted.