JP2008075618A - Screw compressor system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a screw compressor system having a simple structure and inexpensively providing changing of an internal compression ratio. <P>SOLUTION: The screw compression system 1 is provided with a discharge port 10 communicated with a discharge chamber 9 of a screw compressor 2, a high pressure chamber 12 communicated with the discharge port 10, a low pressure chamber 13 holding gas with a lower pressure than the high pressure chamber 12, a piston 14 partitioning the high pressure chamber 12 and the low pressure chamber 13, a slide valve 17 joined to the piston 14, with one part exposed to the discharge chamber 9, a housing 11 housing the piston 14 and the slide valve 17, and an elastic body (a spring) 18 connecting at least one of the piston 14 or the slide valve 17 to the housing 111. It is characterized by that an exposed part 16 of the slide valve 17 exposed to the discharge chamber 9 changes the volume of the discharge chamber 9 by movement of the piston 14 and the slide valve 17 due to pressure change in a high pressure chamber 12 interior. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a screw compressor system, and more particularly to a screw compressor system capable of changing an internal compression ratio with a simple structure.

  Conventional general screw compressors have an internal compression ratio fixed by the shape of the discharge port of the housing of the compressor. For this reason, when the pressure at the discharge port is higher or lower than the pressure immediately before the discharge of the compressed gas, the pressure of the compressed gas immediately after the discharge increases or decreases, resulting in deterioration of energy efficiency or pulsation at the discharge port. There was a problem of generating noise.

In order to solve such problems, research on screw compressors that can change the internal compression ratio has been conducted, and the position of the opening to the discharge port is changed by a valve that slides in the direction of the rotation axis of the rotor. Some have variable compression ratios (see, for example, Patent Document 1).
JP-A-60-228789 (FIGS. 1 and 2)

  However, in a screw compressor in which the internal compression ratio is variable by changing the opening position to the discharge port by a valve that slides in the rotation axis direction of the rotor (see, for example, Patent Document 1), the valve shape is complicated due to the structure. Therefore, there is a problem that processing is difficult and manufacturing cost is high. Also, when controlling a valve that slides, complicated control is required, such as detecting the discharge pressure with a pressure sensor, calculating the optimum position with a microcomputer, and moving the valve with hydraulic pressure, which increases manufacturing and operating costs. There was a problem.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a screw compressor system having a simple structure and capable of changing the internal compression ratio at low cost.

  A screw compressor system according to the present invention includes a screw compressor including a screw compressor that sucks gas from an intake chamber with a pair of rotors, compresses the gas with the pair of rotors, and discharges the gas from a discharge chamber. A discharge port that communicates with a discharge chamber of the screw compressor, a high-pressure chamber that communicates with the discharge port, a low-pressure chamber that contains a gas having a pressure lower than that of the high-pressure chamber, the high-pressure chamber, and the A piston that partitions the low-pressure chamber; a slide valve that is coupled to the piston, a part of which is exposed to the discharge chamber of the screw compressor; a housing that houses the piston and the slide valve; and the piston and the slide valve At least one and an elastic body connecting the housing, and the piston and the slide valve are By moving the pressure change in the chamber portion, the exposed portion of the slide valve is exposed to the discharge chamber, is characterized in that changing the volume of the discharge chamber.

  A screw compressor system according to the present invention is coupled to a high-pressure chamber that communicates with a discharge port, a low-pressure chamber that contains gas at a pressure lower than that of the high-pressure chamber, a piston that partitions the high-pressure chamber and the low-pressure chamber, and a piston. A slide valve that is exposed to the discharge chamber of the screw compressor, a housing that accommodates the piston and the slide valve, and an elastic body that connects at least one of the piston and the slide valve to the housing, and the piston and the slide valve have a high pressure Since the exposed portion where the slide valve is exposed to the discharge chamber changes the volume of the discharge chamber by moving due to the pressure change in the chamber, the internal compression ratio can be changed with a simple structure without using a pressure sensor or the like. It becomes possible. Further, by appropriately setting the elastic coefficient of the elastic body, the pressure immediately before the discharge of the compressed gas and the pressure of the discharge port can be made substantially coincident, and the internal compression ratio with little energy loss can be achieved.

(Embodiment 1)
FIG. 1 is a system configuration diagram showing a configuration of a fuel cell system including a screw compressor system according to Embodiment 1 of the present invention. FIG. 1 shows an example in which the screw compressor system according to the present embodiment is applied to a fuel cell system, but the screw compressor system according to the present embodiment is also used as a supercharger for a gasoline engine vehicle, for example. be able to.

  In the example shown in FIG. 1, the screw compressor system 1 according to the present embodiment sucks air (gas) through an air filter 30 and compresses air to a predetermined pressure. The compressed air is sent to the fuel cell 40, where oxygen in the air reacts with hydrogen supplied from a fuel tank (not shown) of the fuel cell system or the like to generate power. At this time, the pressure adjusting device 50 provided on the downstream side of the fuel cell 40 adjusts the pressure of the air discharged from the screw compressor system 1 so that the pressure of the air in the fuel cell 40 is optimal for power generation. The pressure adjusting device 50 may be a butterfly valve, for example, or may be a simple pressure loss element that cannot change an opening area such as an orifice.

  Since the fuel cell 40 requires various air flow rates and air pressures depending on the power generation amount, the screw compressor system 1 supplies the air amount required by the fuel cell 40 by changing the rotation speed by the motor and inverter that drive the screw compressor system 1. . Then, the pressure adjusting device 50 changes the pressure loss so that the pressure of the air electrode of the fuel cell 40 becomes a desired pressure. At this time, not only the air electrode of the fuel cell 40 but also the pressure of the discharge port (described later) of the screw compressor system 1 changes.

  FIG. 2 is a cross-sectional view showing a general screw compressor. Fig.2 (a) is a longitudinal cross-sectional view of the general screw compressor 2, FIG.2 (b) is BB sectional drawing of Fig.2 (a). The screw compressor system 1 according to this embodiment will be described later.

  As shown in FIG. 2B, the general screw compressor 2 includes a pair of rotors 3 and 4, one of which is a male rotor 3 and the other is a female rotor 4. The rotors 3 and 4 are accommodated in the rotor chamber 6 of the compressor casing 5. The male rotor 3 is coupled to the rotation shaft 7, and the rotation of the rotation shaft 7 causes the male rotor 3 and the female rotor 4 to rotate in opposite directions.

  The male rotor 3 and the female rotor 4 are formed with tooth lines, and the tooth lines of the male rotor 3 and the female rotor 4 are engaged with each other. The screw compressor 2 sucks a gas such as air from the intake chamber 8 when the male rotor 3 and the female rotor 4 rotate in opposite directions to increase the meshing volume. The gas is compressed by reducing the meshing volume by the rotation of the rotors 3 and 4, and the compressed gas is discharged from the discharge chamber 9. In such a general screw compressor 2, the internal compression ratio (the pressure ratio of the gas before suction and the pressure ratio of the gas after discharge) is fixed depending on the volume and shape of the discharge chamber 9.

  FIG. 3 is a cross-sectional view showing the screw compressor system according to Embodiment 1 of the present invention. FIG. 3 shows a cross section of the same discharge chamber as in FIG. The screw compressor 2 of the screw compressor system 1 according to the present embodiment is substantially the same as the screw compressor 2 shown in FIG.

  As shown in FIG. 3, the screw compressor system 1 according to the present embodiment has a discharge port 10 that communicates with the discharge chamber 9 of the screw compressor 2. The discharge port 10 communicates with a high-pressure chamber 12 formed in the housing 11 via a branch pipe 12a, and the housing 11 is adjacent to the high-pressure chamber 12 and accommodates a gas having a pressure lower than that of the high-pressure chamber. Is formed. The housing 11 of the screw compressor system 1 may be formed integrally with the compressor casing 5 of the screw compressor 2.

  The high-pressure chamber 12 and the low-pressure chamber 13 are partitioned by a piston 14 so that when the pressure inside the high-pressure chamber 12 changes according to the pressure change of the discharge port 10, the piston 14 moves in the left-right direction in FIG. It has become. The high-pressure chamber 12 and the low-pressure chamber 13 are configured such that gas cannot be exchanged by a seal member 14 a provided on the piston 14. In the present embodiment, the low pressure chamber 13 communicates with the intake chamber 8 of the screw compressor 2 through the communication pipe 15 so as to prevent generation of noise when gas is discharged from the low pressure chamber 13. The low pressure chamber 13 may be opened to the outside air, for example, and may be maintained at substantially atmospheric pressure.

  The piston 14 is coupled to a slide valve 17 having an exposed portion 16 exposed to the discharge chamber 9 of the screw compressor 2, and the piston 14 and the slide valve 17 move together in the housing 11. Here, the moving direction of the piston 14 and the slide valve 17 is a direction perpendicular to the rotation axis of the rotors 3 and 4. The piston 14 and the slide valve 17 may be formed integrally. Further, the piston 14 and the housing 11 are connected by a spring 18 so that the piston 14 and the slide valve 17 are pushed back when they move to the discharge chamber 9 side (the right side in FIG. 3). 3 shows an example in which two springs 18 are provided in the low-pressure chamber 13, the spring 18 may be another elastic body, and at least one of the piston 14 and the slide valve 17 and the housing 11 are connected. As long as it connects, you may provide in another position.

  A seal member 16 a is provided around the exposed portion 16 of the slide valve 17 so that gas cannot pass between the discharge chamber 9 and the low pressure chamber 13. Also, a seal member 17a is provided at the end of the slide valve 17 opposite to the exposed portion 16, so that gas cannot pass between the high pressure chamber 12 and the external space. In the present embodiment, as shown in FIG. 3, the slide valve 17 is provided so as to penetrate the high pressure chamber 12 and the low pressure chamber 13.

  The housing 11 is provided with a stopper 19 that contacts the piston 14 when the pressure in the high-pressure chamber 13 exceeds a predetermined value, restricts the movement of the piston 14 and the slide valve 17, and further exposes the exposed portion. 16 is not exposed to the discharge chamber 9. Furthermore, a stopper 20 is also provided on the high pressure chamber 12 side of the housing 11, and when the pressure in the high pressure chamber 13 becomes a predetermined value or less, it contacts the slide valve 17 (more specifically, a limiter adjusting mechanism 17b, which will be described later). Thus, the movement of the piston 14 and the slide valve 17 is restricted, and the slide valve 17 is not pushed further into the high pressure chamber 12 side. The position where the stopper for restricting the movement of the piston 14 and the slide valve 17 is provided is not limited to the position shown in FIG. 3 as long as the position is in contact with at least one of the piston 14 and the slide valve 17.

  A limiter adjustment mechanism 17b is provided at the end of the slide valve 17 opposite to the exposed portion 16. The limiter adjustment mechanism 17b is attached to the main body of the slide valve 17 with a screw structure, for example, and is exposed when the limiter adjustment mechanism 17b contacts the stopper 20 by adjusting the screwing amount of the limiter adjustment mechanism 17b. The volume at which the portion 16 is exposed to the discharge chamber 9 can be changed. Thereby, it is possible to finely adjust the variation in the internal compression ratio caused by the variation in processing of the slide valve 17 or the like.

  Here, the operation of the screw compressor system 1 according to the present embodiment will be described using the fuel cell system of FIG. 1 as an example. When the fuel cell 40 is stopped, the limiter adjusting mechanism 17b is in contact with the stopper 20 as shown in FIG. 3, and the volume at which the exposed portion 16 is exposed to the discharge chamber 9 is minimized. . At this time, the volume of the discharge chamber 9 is maximum, and the internal compression ratio is minimum.

  When the fuel cell 40 is activated and the fuel cell 40 requests air having a predetermined pressure and flow rate necessary for power generation, the rotational speed of the screw compressor system 1 increases and the pressure adjusting device 50 is removed from the screw compressor system 1. The throttle amount is adjusted so that the supplied air has the required pressure. Accordingly, the pressure of the discharge port 10 also rises, and the pressure of the high-pressure chamber 12 that communicates with the discharge port 10 also rises. When the pressure in the high-pressure chamber 12 rises, the piston 14 is pushed by the pressure, and the piston 14 and the slide valve 17 move to the right side in FIG. At this time, the volume of the exposed portion 16 where the slide valve 17 is exposed to the discharge chamber 9 increases, and the volume of the discharge chamber 9 decreases. Thereby, the timing at which gas is discharged from the rotors 3 and 4 is delayed, and the internal compression ratio is increased. Note that the tip of the exposed portion 16 and the end of the tooth of the rotor 4 are substantially parallel so that the discharge chamber 9 is kept airtight even when the slide valve 17 moves. Further, the piston 14 comes into contact with the stopper 19 when the fuel cell 40 has the maximum output.

  When the output of the fuel cell 40 decreases, the pressure of the fuel cell 40 and the discharge port 10 is lowered by the pressure adjusting device 50, and the piston 14 and the slide valve 17 move to the left side of the drawing in FIG. As a result, the volume of the exposed portion 16 where the slide valve 17 is exposed to the discharge chamber 9 decreases, and the volume of the discharge chamber 9 increases. Thereby, the timing at which gas is discharged from the rotors 3 and 4 is advanced, and the internal compression ratio is lowered.

  Thus, the internal compression ratio of the screw compressor 2 increases when the pressure of the discharge port 10 increases, and the internal compression ratio of the screw compressor 2 decreases when the pressure of the discharge port 10 decreases. By appropriately determining the elastic coefficient of the spring 18, the pressure of the discharge port 10 and the pressure of the gas immediately before discharge can be made substantially coincident. Here, the force F <b> 1 applied to the piston 14 (rightward in FIG. 3) is obtained by multiplying the pressure difference between the high pressure chamber 12 and the low pressure chamber 13 and the area of the piston 14. The force F2 applied to the slide valve 17 (leftward in FIG. 3) is obtained by multiplying the difference between the pressure in the discharge chamber 9 and the atmospheric pressure by the cross-sectional area of the slide valve 17. As a result, the moving amount x of the slide valve 17 is x = (F1-F2) / k, where k is the spring constant of the spring 18, and the volume of the exposed portion 16 exposed to the discharge chamber 9 is appropriate for this x. By adjusting the internal compression ratio, it is possible to change the internal compression ratio so that the pressure at the discharge port 10 and the pressure of the gas immediately before discharge are substantially the same.

  In the present embodiment, the high-pressure chamber 12 that communicates with the discharge port 10, the low-pressure chamber 13 that contains a gas lower in pressure than the high-pressure chamber 12, the piston 14 that partitions the high-pressure chamber 12 and the low-pressure chamber 13, and the piston 14 are combined. , A slide valve 17 that is partially exposed to the discharge chamber 9 of the screw compressor 2, a housing 11 that houses the piston 14 and the slide valve 17, and a spring 18 that connects the piston 14 and the housing 11. Since the slide valve 17 is moved by the pressure change in the high pressure chamber 12 and the exposed portion 16 where the slide valve 17 is exposed to the discharge chamber 9 changes the volume of the discharge chamber 9, the pressure sensor is not used. The internal compression ratio can be changed with a simple structure. Further, by appropriately setting the spring constant of the spring 18, the pressure immediately before the discharge of the compressed gas and the pressure of the discharge port can be substantially matched, and the internal compression ratio with little energy loss can be achieved.

  Furthermore, since the movement of the piston 14 and the slide valve 17 is limited by the stoppers 19 and 20 within a range where the internal compression ratio becomes the maximum value and the minimum value, the screw compressor system 1 can be operated safely and with high energy efficiency. It becomes possible.

(Embodiment 2)
FIG. 4 is a cross-sectional view showing a screw compressor system according to Embodiment 2 of the present invention. Since the screw compressor 2 of the screw compressor system 1 according to the present embodiment is the same as the screw compressor 2 according to the first embodiment, the illustration thereof is omitted in FIG. 4 and only the housing 11 is shown. Moreover, the screw compressor system 1 which concerns on this embodiment is the same as that of the screw compressor system which concerns on Embodiment 1 except the point shown below, and attaches | subjects and demonstrates the same code | symbol to the same component.

  In the screw compressor system 1 according to the present embodiment, the shock absorbers 19a and 20a are provided on the stoppers 19 and 20 that restrict the movement of the piston 14 and the slide valve 17. The cushioning materials 19a and 20a are provided at a portion where the piston 14 or the slide valve 17 contacts, and are made of rubber, for example.

  Thereby, the collision noise generated when the piston 14 or the slide valve 17 is seated on the stoppers 19 and 20 can be reduced, and a low noise screw compressor system can be realized. Other effects are the same as those of the screw compressor system 1 according to the first embodiment.

(Embodiment 3)
FIG. 5 is a cross-sectional view illustrating a screw compressor system according to Embodiment 3 of the present invention. Since the screw compressor 2 of the screw compressor system 1 according to the present embodiment is the same as the screw compressor 2 according to the first embodiment, the illustration thereof is omitted in FIG. 5 and only the housing 11 is shown. Moreover, the screw compressor system 1 which concerns on this embodiment is the same as that of the screw compressor system which concerns on Embodiment 1 except the point shown below, and attaches | subjects and demonstrates the same code | symbol to the same component. Further, it is assumed that the screw compressor system 1 according to the present embodiment is not provided with the limiter adjustment mechanism 17b.

  In the screw compressor system 1 according to the present embodiment, in addition to the spring 18 that couples the piston 14 and the housing 11, a spring 18a having a spring constant (elastic coefficient) different from that of the spring 18 is provided. In this embodiment, the spring 18a connects the stopper 20 of the housing 11 and the slide valve 17. However, the position where the additional spring is provided connects at least one of the piston 14 and the slide valve 17 to the housing 11. If it does, it will not be limited to said position. Further, an additional spring or an elastic body may be connected in series to the spring 18 that couples the piston 14 and the housing 11.

  In the screw compressor system 1 according to the present embodiment, the plurality of springs 18 and 18a having different spring constants (elastic coefficients) are connected to the piston 14 and the slide valve 17, and therefore have at least two types of natural frequencies. It becomes. Thereby, when the spring 18 or the spring 18a is surging, the vibrations cancel each other, so that surging can be reduced. Other effects are the same as those of the screw compressor system 1 according to the first embodiment.

(Embodiment 4)
FIG. 6 is a cross-sectional view showing a screw compressor system according to Embodiment 4 of the present invention. Since the screw compressor 2 of the screw compressor system 1 according to the present embodiment is the same as the screw compressor 2 according to the first embodiment, the illustration is omitted in FIG. 6 and only the housing 11 is shown. Moreover, the screw compressor system 1 which concerns on this embodiment is the same as that of the screw compressor system which concerns on Embodiment 1 except the point shown below, and attaches | subjects and demonstrates the same code | symbol to the same component. Further, it is assumed that the screw compressor system 1 according to the present embodiment is not provided with the limiter adjustment mechanism 17b.

  In the screw compressor system 1 according to the present embodiment, a dashpot 21 that connects the slide valve 17 and the housing 11 is provided. In this embodiment, it is assumed that the dash pot 21 connects the stopper 20 of the housing 11 and the slide valve 17. However, the dash pot 21 is provided at least one of the piston 14 and the slide valve 17 and the housing 11. If it connects, it will not be limited to said position.

  In the screw compressor system 1 according to the present embodiment, since the dash pot 21 that connects the slide valve 17 and the housing 11 is provided, the slide valve 17 can be stably operated. Other effects are the same as those of the screw compressor system 1 according to the first embodiment.

(Embodiment 5)
FIG. 7 is a cross-sectional view showing a screw compressor system according to Embodiment 5 of the present invention. In addition, since the screw compressor 2 of the screw compressor system 1 according to the present embodiment is the same as the screw compressor 2 according to the first embodiment, the illustration thereof is omitted in FIG. Moreover, the screw compressor system 1 which concerns on this embodiment is the same as that of the screw compressor system which concerns on Embodiment 1 except the point shown below, and attaches | subjects and demonstrates the same code | symbol to the same component.

  In the screw compressor system 1 according to the present embodiment, a motor 22 is connected to the limiter adjustment mechanism 17b, and a control means 23 composed of a microprocessor or the like is electrically connected to the motor 22. In the present embodiment, the limiter adjusting mechanism 17b is attached to the main body of the slide valve 17 with a screw structure, and the screwing amount can be adjusted by rotating the motor 22. The control means 23 automatically changes the screwing amount of the limiter adjustment mechanism 17b according to the detection value of a pressure sensor (not shown) provided at the discharge port 10, for example. Thereby, when the limiter adjusting mechanism 17 b comes into contact with the stopper 20, the volume of the exposed portion 16 exposed to the discharge chamber 9 can be changed.

  For example, when the screw compressor system 1 is operated at a low internal compression ratio to dry the fuel cell 40, the control unit 23 increases the screwing amount of the limiter adjusting mechanism 17b to increase the volume of the discharge chamber 9. Can do. Further, when dust accumulates in the piping downstream of the discharge port 10 and the pressure loss increases, the screwing amount of the limiter adjusting mechanism 17b can be reduced, the volume of the discharge chamber 9 can be reduced, and a high internal compression ratio can be obtained. it can. Further, when the discharge port 10 is provided with a pressure sensor (not shown) and the average pressure of the discharge port 10 becomes high, the screwing amount of the limiter adjusting mechanism 17b is reduced to increase the internal compression ratio. Also good. In this embodiment, the limiter adjusting mechanism 17b is attached to the main body of the slide valve 17 with a screw structure. However, the limiter adjusting mechanism 17b may have another structure, and the limiter adjusting mechanism may be driven by a driving source other than the motor. Adjustment of 17b may be performed.

  In the screw compressor system 1 according to the present embodiment, the control unit 23 that automatically changes the volume of the exposed portion 16 exposed to the discharge chamber 9 when the limiter adjusting mechanism 17b contacts the stopper 20 is provided. For example, the internal compression ratio can be optimized according to the pressure loss downstream of the discharge port 10. Other effects are the same as those of the screw compressor system 1 according to the first embodiment.

  Needless to say, the present invention is not limited to the above-described embodiments, and includes various modifications and improvements that can be made within the scope of the technical idea. For example, the screw compressor system 1 according to the present invention can be used as a compressor of a refrigeration apparatus in which the pressure of the discharge port 10 varies.

1 is a system configuration diagram illustrating a configuration of a fuel cell system including a screw compressor system according to Embodiment 1 of the present invention. It is sectional drawing which shows a general screw compressor. It is sectional drawing which shows the screw compressor system which concerns on Embodiment 1 of this invention. It is sectional drawing which shows the screw compressor system which concerns on Embodiment 2 of this invention. It is sectional drawing which shows the screw compressor system which concerns on Embodiment 3 of this invention. It is sectional drawing which shows the screw compressor system which concerns on Embodiment 4 of this invention. It is sectional drawing which shows the screw compressor system which concerns on Embodiment 5 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Screw compressor system 2 Screw compressor 3 Male rotor 4 Female rotor 5 Compressor casing 6 Rotor chamber 7 Rotating shaft 8 Intake chamber 9 Discharge chamber 10 Discharge port 11 Housing 12 High pressure chamber 12a Branch pipe 13 Low pressure chamber 14 Piston 14a, 16a , 17a Seal member 15 Communication pipe 16 Exposed portion 17 Slide valve 17b Limiter adjustment mechanism 18 Spring 19, 20 Stopper 19a, 20a Buffer material 21 Dashpot 22 Motor 23 Control means 30 Air filter 40 Fuel cell 50 Pressure adjustment device

Claims (11)

A screw compressor system comprising a screw compressor that sucks gas from an intake chamber with a pair of rotors, compresses the gas with the pair of rotors, and discharges the gas from a discharge chamber,
A discharge port communicating with the discharge chamber of the screw compressor;
A high pressure chamber communicating with the discharge port;
A low-pressure chamber containing gas having a pressure lower than that of the high-pressure chamber;
A piston that partitions the high pressure chamber and the low pressure chamber;
A slide valve coupled to the piston, a part of which is exposed to the discharge chamber of the screw compressor;
A housing that houses the piston and the slide valve;
An elastic body connecting at least one of the piston and the slide valve and the housing;
With
The screw compressor, wherein the piston and the slide valve are moved by a pressure change in the high pressure chamber, so that an exposed portion where the slide valve is exposed to the discharge chamber changes a volume of the discharge chamber. system.   The housing is provided with a stopper that contacts at least one of the piston and the slide valve when the pressure in the high pressure chamber becomes equal to or higher than a predetermined value or lower than a predetermined value, and restricts movement of the piston and the slide valve. The screw compressor system according to claim 1, comprising: a screw compressor system according to claim 1.   The screw compressor system according to claim 2, wherein the stopper includes a buffer material in a portion that contacts at least one of the piston and the slide valve.   The said slide valve has a limiter adjustment mechanism which can change the volume of the said exposed part when at least one of the said piston and the said slide valve and the said stopper contact. A screw compressor system as described in.   5. The screw compressor according to claim 4, wherein the limiter adjusting mechanism changes a volume of the exposed portion when at least one of the piston and the slide valve comes into contact with the stopper by a screw structure. system.   The screw compressor system according to claim 4, wherein the limiter adjusting mechanism includes a control unit that automatically changes a volume of the exposed portion.   The screw compressor system according to any one of claims 1 to 6, wherein the elastic body includes a spring.   The screw compressor system according to claim 7, wherein the elastic body includes a plurality of springs having different elastic coefficients.   The screw compressor system according to any one of claims 1 to 8, further comprising a dashpot connected to at least one of the piston and the slide valve and the housing.   The screw compressor system according to any one of claims 1 to 9, wherein the low pressure chamber communicates with an intake chamber of the screw compressor.   The screw compressor system according to any one of claims 1 to 10, wherein a moving direction of the piston and the slide valve is perpendicular to a rotation axis of the pair of rotors.