A screw compressor internal volume ratio automatic adjusting device and method

Abstract

The application discloses a kind of screw compressor content volume ratio automatic regulating device and method, belong to compressor technical field, including content volume ratio regulating slide valve assembly, suction end plate, shell, exhaust end bearing seat and its cover plate, end cover, increase load solenoid valve, pressure sensor and computer control system.Content volume ratio regulating slide valve assembly includes content volume ratio regulating slide valve, guide key, slide valve guide rod, oil piston and spring, content volume ratio regulating slide valve can slide in shell slide valve cavity, realize content volume ratio continuous adjustable;The application compares by the real-time exhaust pressure of acquisition and the rated exhaust pressure value of setting, realizes the control of content ratio regulating slide valve by increase load solenoid valve and decrease load solenoid valve, and then can real-time accurate adjustment real-time exhaust pressure in shell slide valve cavity;Compared with the traditional content volume ratio slide valve position adjustment, the method not only can automatically adjust content volume ratio slide valve position, but also has high adjustment precision.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of compressor, and relates to a screw compressor content volume ratio automatic adjusting device and method. BACKGROUND

[0002] With the development of industrial level, the requirements for industrial equipment are increasingly stringent. As an indispensable device in the petroleum, petrochemical, metallurgical and refrigeration industries, the performance of a screw compressor has an extremely important influence on industrial development.

[0003] The screw compressor is affected by many factors under refrigeration conditions, and its operating compression ratio will fluctuate in a relatively large range, resulting in the occurrence of under-compression or over-compression phenomena, which will inevitably reduce the operating efficiency of the compressor. Therefore, in order to obtain the optimal compression ratio of the compressor and adapt it to changing external conditions, a slide valve mechanism is required to adjust the content volume ratio. At present, the content volume ratio slide valve position adjustment is mostly achieved manually. The worker moves the content volume ratio slide valve according to the pressure displayed on the pressure gauge connected to the rotor cavity, and then adjusts the pressure in the rotor cavity. However, because of the accuracy of the pressure gauge and the hysteresis of the worker's adjustment, the worker often needs to adjust the slide valve position multiple times to complete the adjustment, and the adjustment precision is low. This method is time-consuming and labor-intensive, increases the labor intensity of the worker, and reduces the operating efficiency of the compressor.

[0004] Therefore, for a screw compressor, if the content volume ratio adjusting slide valve can be automatically and accurately adjusted according to the actual working condition, the labor intensity of the worker is reduced, and the operating efficiency of the compressor is improved. SUMMARY

[0005] The present application aims to overcome the shortcomings of the prior art and provide a screw compressor content volume ratio automatic adjusting device and method, which can automatically and accurately adjust the position of the content volume ratio slide valve, thereby ensuring the optimal compression ratio of the compressor, adapting it to changing external conditions, reducing the labor intensity of the worker, and improving the operating efficiency of the compressor.

[0006] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0007] A screw compressor content volume ratio automatic adjusting method, comprising the following steps:

[0008] Step 1: setting the upper and lower limits of the rated discharge pressure value;

[0009] Step 2: collecting the real-time discharge pressure in the casing slide valve cavity through a pressure sensor; the pressure sensor is connected to the through hole on the content volume ratio adjusting slide valve to collect the real-time discharge pressure in the casing slide valve cavity;

[0010] Step 3, judging whether the real-time exhaust pressure is between the upper limit and the lower limit, if yes, stopping adjusting the real-time exhaust pressure; if no, moving the content volume ratio adjusting spool through the load increasing electromagnetic valve and the load reducing electromagnetic valve, and then adjusting the real-time exhaust pressure in the casing spool valve cavity.

[0011] Further improvement of the present application is:

[0012] Preferably, in step 3, if the real-time exhaust pressure is greater than the upper limit of the rated exhaust pressure value, the content volume ratio adjusting spool moves to the suction end; if the real-time exhaust pressure is less than the lower limit of the rated exhaust pressure value, the content volume ratio adjusting spool moves to the exhaust end.

[0013] Preferably, when the content volume ratio adjusting spool moves to the suction end, the hydraulic oil flows through the path: the hydraulic oil enters the load increasing electromagnetic valve through the internal oil channel of the exhaust end bearing seat, the hydraulic oil flowing out of the load increasing electromagnetic valve enters the internal oil channel of the exhaust end bearing seat cover plate again, and then enters the internal oil channel of the end cover, flows into the oil piston cavity to drive the oil piston to move, and then drives the content volume ratio adjusting spool to move to the suction end.

[0014] Preferably, when the content volume ratio adjusting spool moves to the exhaust end, the hydraulic oil flows through the path: the hydraulic oil enters the internal oil channel of the end cover through the oil piston cavity, then enters the internal oil channel of the exhaust end bearing seat cover plate through the internal oil channel of the exhaust end bearing seat, and then enters the internal oil channel of the casing through the internal oil channel of the exhaust end bearing seat after passing through the load reducing electromagnetic valve, and finally enters the casing rotor cavity, so that the oil piston moves, thereby driving the content volume ratio adjusting spool to move to the exhaust end.

[0015] Preferably, in step 3, if the real-time exhaust pressure is between the upper limit and the lower limit of the rated exhaust pressure value, the load increasing electromagnetic valve and the load reducing electromagnetic valve are both closed.

[0016] A content volume ratio automatic adjusting device for a screw compressor, comprising a casing, an exhaust end bearing seat connected to the exhaust end of the casing, an exhaust end bearing seat cover plate connected to the outer end of the exhaust end bearing seat, an oil piston provided in the exhaust end bearing seat cover plate, a spool guide rod provided in the exhaust end bearing seat and the exhaust end bearing seat cover plate, and a content volume ratio adjusting spool provided in the casing.

[0017] A content volume ratio automatic adjusting device for a screw compressor, comprising a casing, an exhaust end bearing seat connected to the exhaust end of the casing, an exhaust end bearing seat cover plate connected to the outer end of the exhaust end bearing seat, an oil piston provided in the exhaust end bearing seat cover plate, a spool guide rod provided in the exhaust end bearing seat and the exhaust end bearing seat cover plate, and a content volume ratio adjusting spool provided in the casing.

[0018] The power output end of the oil piston is connected to the spool guide rod, and the other end of the spool guide rod is connected to the content volume ratio adjusting spool.

[0019] The load increasing electromagnetic valve and the load reducing electromagnetic valve are provided on the exhaust end bearing seat, and control the moving direction of the oil piston through the hydraulic oil.

[0020] A pressure sensor is inserted into the housing. The exhaust end of the internal volume ratio regulating slide valve has a through hole. One end of the through hole is connected to the exhaust end of the rotor cavity, and the other end of the through hole is connected to the pressure sensor.

[0021] The pressure sensor is connected to a computer control system, which is connected to a valve-controlled oil piston PLC control module. The valve-controlled oil piston PLC control module is connected to an increase-load solenoid valve and an decrease-load solenoid valve.

[0022] Preferably, the bottom of the volume ratio adjusting slide valve is provided with a vent groove, and the through hole and the pressure sensor are connected through the vent groove.

[0023] Preferably, the bottom of the volume ratio adjusting slide valve is provided with a guide groove, and the bottom of the housing is equipped with a slide valve guide key, the upper end of which extends into the guide groove.

[0024] Preferably, the oil piston has two circumferential sealing grooves, and sealing rings are installed in the sealing grooves.

[0025] Preferably, the housing has a housing shoulder at the exhaust end and an intake end plate on the intake end face of the housing.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] This invention discloses an automatic adjustment method for the internal volume ratio of a screw compressor. This method compares the collected real-time exhaust pressure with the set rated exhaust pressure value, and controls the internal volume ratio adjustment slide valve through the load increase solenoid valve and the load decrease solenoid valve, thereby enabling real-time and precise adjustment of the real-time exhaust pressure in the slide valve chamber of the compressor housing. Compared with the traditional internal volume ratio slide valve position adjustment, this method can not only automatically adjust the position of the internal volume ratio slide valve, but also has high adjustment accuracy.

[0028] This invention discloses an automatic volume ratio adjustment device for a screw compressor, comprising a volume ratio adjustment slide valve assembly, a housing, an exhaust end bearing seat and its cover plate, an end cover, a load-increasing / reducing solenoid valve, a pressure sensor, a computer control system, and a valve-controlled oil piston PLC control module. The aforementioned volume ratio adjustment slide valve assembly includes a volume ratio adjustment slide valve, a guide key, a slide valve guide rod, an oil piston, and a spring. The volume ratio adjustment slide valve can slide within the slide valve cavity of the housing, achieving continuous adjustment of the volume ratio. The aforementioned pressure sensor is placed at the bottom of the housing to detect the real-time exhaust pressure p1; the aforementioned load-increasing / reducing solenoid valve is placed on the exhaust end bearing seat. The computer control system compares p1 with the system-set rated exhaust pressure value pk, controlling the on / off state of the load-increasing / reducing solenoid valve to allow hydraulic oil to enter and exit the oil piston cavity, thereby driving the slide valve to move and achieving automatic adjustment of the volume ratio. Through the above-mentioned automatic adjustment device and method, precise adjustment of the volume ratio can be achieved, effectively avoiding over-compression or under-compression, and improving the compressor's compression efficiency and the unit's refrigeration energy efficiency.

[0029] Furthermore, an intake end plate is installed on the intake end face inside the housing to prevent compressed gas from leaking from the gap between the housing and the slide valve.

[0030] Furthermore, to ensure that the sensor hole on the housing and the through hole on the slide valve remain connected, a groove 120mm long and 10mm wide is provided at the bottom of the slide valve, so that the sensor hole and the through hole on the slide valve can be connected through this groove during the movement of the slide valve.

[0031] Furthermore, to ensure that as little oil as possible leaks into the spring cavity from the gap between the oil piston and the bearing housing cover plate hole at the exhaust end, two annular sealing grooves are provided on the oil piston, and sealing rings are installed in the grooves.

[0032] Furthermore, to prevent the slide valve from moving excessively toward the intake side and colliding with the motor, a shoulder is provided on the housing. Attached Figure Description

[0033] Figure 1 This is a control flowchart for the automatic adjustment of the volume ratio slide valve in this invention.

[0034] Figure 2 This is a cross-sectional view of the overall structure of the present invention;

[0035] The markings in the diagram are as follows: 1 - end cap; 2 - exhaust end bearing seat cover plate; 3 - exhaust end bearing seat; 4 - housing; 5 - through hole; 6 - pressure sensor; 7 - internal volume ratio adjustment slide valve; 8 - slide valve guide key; 9 - load increase solenoid valve; 10 - load decrease solenoid valve; 11 - slide valve guide rod; 12 - spring; 13 - oil piston.

[0036] Figure 3 The groove is opened at the bottom of the exhaust end of the volume ratio regulating slide valve 7, of which 15 is a venting groove.

[0037] Figure 4 This is a partially enlarged cross-sectional view of the overall structure of this invention. 14 is the intake end plate; 20 is the guide groove.

[0038] Figure 5 This is a structural diagram of the intake end plate.

[0039] Figure 6 This is a diagram showing the installation position of the intake end plate on the housing.

[0040] Figure 7 This refers to the oil piston with a sealing groove and its relative position to the exhaust end bearing housing cover. 16 is an annular sealing groove one; 17 is an annular sealing groove two.

[0041] Figure 8This diagram shows the relative positions of the motor, housing shoulder, and internal volume ratio adjustment valve. 18 represents the motor; 19 represents the housing shoulder. Detailed Implementation

[0042] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0043] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. The terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, unless otherwise explicitly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection or a detachable connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal connection of two elements. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0044] One embodiment of the present invention discloses an automatic adjustment method for the internal volume ratio of a screw compressor, the method comprising the following steps:

[0045] Step 1: Set the upper and lower limits of the rated exhaust pressure value;

[0046] The method of this invention is based on an automated process. First, an upper and lower limit for the rated exhaust pressure value is set in the host computer, forming a target range for the exhaust pressure within the slide valve chamber. 下 ≤p1≤p 上 The host computer inputs the target exhaust pressure to the valve control piston PLC control module;

[0047] Step 2: Collect the real-time exhaust pressure in the valve chamber of the housing using pressure sensor 6;

[0048] The pressure sensor 6 is directly connected to the valve chamber of the housing, and can collect the exhaust pressure in the valve chamber in real time. At the same time, the collected value of the pressure sensor 6 is transmitted to the valve control piston PLC control module.

[0049] Step 3: Determine whether the real-time exhaust pressure is between the upper and lower limits. If it is, stop adjusting the real-time exhaust pressure. If it is not, adjust the internal volume ratio regulating slide valve 7 by using the load increase solenoid valve 9 and the load decrease solenoid valve 10, thereby adjusting the real-time exhaust pressure in the slide valve chamber of the housing.

[0050] Specifically, it is mainly used to control the on / off state of the load increase solenoid valve 9 and the load decrease solenoid valve 10. The two solenoid valves work together to adjust the movement of the internal volume adjustment slide valve 7. By adjusting the movement of the internal volume adjustment slide valve 7 in the slide valve chamber of the housing, the exhaust pressure of the slide valve chamber of the housing is adjusted.

[0051] After receiving the exhaust pressure collected by pressure sensor 6, the valve-controlled oil piston PLC control module compares it with the target range of exhaust pressure, specifically including the following three cases:

[0052] (1) If p1>p 上 Then the computer control system transmits the signal of decreasing internal volume ratio to the valve control piston control module, the load solenoid valve 9 opens, thereby causing the internal volume ratio adjusting slide valve 7 to move toward the intake end, and the real-time exhaust pressure p1 value decreases.

[0053] (2) If p1 <p 下 Then the computer control system transmits the signal of increasing internal volume ratio to the valve control piston control module, the unloading solenoid valve opens, thereby causing the internal volume ratio adjusting slide valve to move towards the exhaust end, and the real-time exhaust pressure p1 value increases.

[0054] (3) If p 下 ≦p1≦p 上 If the computer control system stops comparing the p value, it transmits the signal indicating that the internal volume ratio adjustment is complete to the valve control piston PLC control module. The load increase / decrease solenoid valves are closed, the position of the internal volume ratio adjustment slide valve is fixed, and the system completes this exhaust pressure monitoring and slide valve position adjustment.

[0055] Furthermore, because the movement of the load-increasing solenoid valve 9 and the load-reducing solenoid valve 10 has been changed from manual to automatic adjustment, the overall control oil circuit has been altered, specifically as follows:

[0056] If p1>p 上 The computer control system then transmits a signal to the load-increasing solenoid valve 9 and the load-reducing solenoid valve 10 to the control module of the oil control piston 13. The load-increasing solenoid valve 9 opens. The hydraulic oil flows through the following path: internal oil passage of exhaust end bearing seat 3 → load-increasing solenoid valve 9 → internal oil passage of exhaust end bearing seat 3 → internal oil passage of exhaust end seat cover plate 2 → internal oil passage of end cover 1 → oil piston chamber of exhaust end seat cover plate 2. The oil pushes the oil piston 13 to move, thereby causing the internal volume ratio adjusting slide valve 7 to move towards the intake end, reducing the real-time exhaust pressure p1 value. When drilling holes in the reinforcing ribs of the oil passage of exhaust end seat cover plate 2, only one hole needs to be drilled, shortening the part processing time.

[0057] If p1 <p 下The computer control system then transmits the signal to increase the internal volume ratio to the control module of valves 9 and 10 and oil control piston 13. The unloading solenoid valve 10 opens, and the hydraulic oil flows through the following path: oil piston chamber of exhaust end cover plate 2 → internal oil passage of end cover 1 → internal oil passage of exhaust end cover plate 2 → internal oil passage of exhaust end bearing seat 3 → unloading solenoid valve 10 → internal oil passage of exhaust end bearing seat 3 → internal oil passage of housing 4 → rotor chamber of housing 4. The oil piston 13 moves, causing the internal volume ratio adjusting slide valve 7 to move towards the exhaust end, increasing the real-time exhaust pressure p1. During this process, when the oil returns to the rotor chamber of housing 4, the internal oil passages of housing 4 allow the oil to return to the upper side of the rotor chamber, enabling cooling. This contrasts with the conventional return to the lower part of the gap between the motor and rotor, where the oil accumulates and is not fully utilized, and is also detrimental to air intake.

[0058] Because the entire adjustment process described above requires no manual input of the upper and lower pressure limits in the early stages, except for special circumstances, there is no other manual operation during the control process. Based on this, in order to realize the above-mentioned automatic adjustment method of the internal volume ratio of the screw compressor and make the entire adjustment process smoother and more efficient, one embodiment of the present invention provides a device for facilitating the automatic adjustment of the internal volume ratio of the screw compressor.

[0059] See Figure 2 The automatic volume ratio adjustment device for the screw compressor includes a volume ratio adjustment slide valve assembly, a suction end plate, a housing 4, a discharge end bearing seat 3 and its cover plate 2, an end cover 1, an increase-load solenoid valve 9 and an decrease-load solenoid valve 10, a pressure sensor 6, and a computer control system. The aforementioned volume ratio adjustment slide valve assembly includes a volume ratio adjustment slide valve 7, a slide valve guide key 8, a slide valve guide rod 11, an oil piston 13, and a spring 12. The volume ratio adjustment slide valve 7 can slide within the slide valve cavity of the housing, achieving continuous adjustment of the volume ratio.

[0060] One end of the housing 4 is the intake end and the other end is the exhaust end. The exhaust end of the housing is connected to the exhaust end bearing seat 3. The outer end of the exhaust end bearing seat 3 is connected to the exhaust end bearing seat cover plate 2. The outer end of the exhaust end bearing seat cover plate 2 is connected to the end cover 1.

[0061] The housing 4 has two main cavities: a rotor cavity 14 and a housing slide valve cavity. The two cavities are connected. The outer end of the slide valve guide rod 11 is connected to the oil piston 13, and the inner end of the slide valve guide rod 11 is connected to the volume ratio regulating slide valve 7. A spring 12 is fitted on the slide valve guide rod 11 in the exhaust end bearing seat cover plate 2. The slide valve guide rod 11 is mainly placed in the cavity of the exhaust end bearing seat 3, and the volume ratio regulating slide valve 7 is mainly in the housing slide valve cavity. By compressing the spring 12 with the slide valve guide rod 11, the slide valve guide rod 11 can move along its axis, thereby driving the volume ratio regulating slide valve 7 to slide in the housing slide valve cavity, thus regulating the exhaust pressure.

[0062] Based on the above structure, most existing devices directly install a pressure gauge on the housing 4 that is connected to the rotor cavity. The operator adjusts the movement of the oil piston 13 by adjusting the load increase solenoid valve 9 and the load decrease solenoid valve 10 based on the pressure displayed on the pressure gauge, thereby adjusting the movement of the internal volume ratio regulating valve 7.

[0063] See Figure 3 The volume ratio regulating slide valve 7 of the present invention has a vent groove 15 along the axis at the lower part of the exhaust end. One end of the vent groove 15 has a through hole 5, and the other end is connected to the pressure sensor 6. The through hole 5 is located at the exhaust end of the volume ratio regulating slide valve 7. Figure 1 The through hole 5 (located at the left end of the internal volume ratio regulating slide valve 7) penetrates the upper and lower end faces of the internal volume ratio regulating slide valve 7. One end of the through hole 5 is connected to the exhaust end of the rotor chamber, and the other end is connected to the pressure sensor 6 through the vent groove 15. Therefore, the exhaust pressure of the internal volume ratio regulating slide valve 7 can be measured in real time. Preferably, the axis of the through hole 5 is perpendicular to the axis of the internal volume ratio regulating slide valve 7. The pressure sensor 6 is installed at the bottom of the housing 4. The pressure sensor 6 is inserted into the housing 4 from the bottom and is connected to the through hole 5 at the exhaust end of the internal volume ratio regulating slide valve through the vent groove 15. The vent groove 15 can transmit the pressure at the through hole 5 to the pressure sensor 6 in real time, thereby detecting the real-time exhaust pressure p1.

[0064] See Figure 5 , Figure 6 and Figure 7 In this invention, the suction end plate 14 is bolted to the suction end face inside the housing 4 to control the suction end face gap. Simultaneously, it prevents compressed gas from leaking from the gap between the housing 4 and the slide valve 7. The bottom of the internal volume ratio adjusting slide valve 7, near the lower part of the suction end, also has a guide groove 20. The slide valve guide key 8 is installed at the bottom of the housing 4, with its top placed within the guide groove 20, allowing the internal volume ratio adjusting slide valve 7 to move axially and preventing circumferential movement that could cause jamming.

[0065] See Figure 8 The oil piston 13 has two annular sealing grooves around its circumference, namely annular sealing groove one 16 and annular sealing groove two 17, which are used to place sealing rings. When the oil piston 13 moves on the exhaust end bearing seat cover plate, it improves the overall sealing performance.

[0066] See Figure 8 The housing 4 has a housing shoulder 19 at its exhaust end. The housing shoulder 19 can prevent the internal volume ratio adjustment slide valve 17 from being over-adjusted, which could lead to accidental contact with the motor 18. The motor is installed in the motor cavity. The motor rotor and the male rotor are connected by the extended shaft. When the motor rotor rotates, it drives the male rotor to rotate. The male rotor meshes with the female rotor to rotate, thereby achieving compression.

[0067] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for automatically adjusting the internal volume ratio of a screw compressor, characterized in that, Includes the following steps: Step 1: Set the upper and lower limits of the rated exhaust pressure value; Step 2: The real-time exhaust pressure in the housing slide valve cavity is collected by the pressure sensor (6); the pressure sensor (6) is connected to the through hole (5) on the internal volume ratio adjustment slide valve (7), so that the pressure sensor (6) is directly connected to the housing slide valve cavity to collect the real-time exhaust pressure in the housing slide valve cavity. Step 3: Determine if the real-time exhaust pressure is between the upper and lower limits. If it is, stop adjusting the real-time exhaust pressure. If not, the volume ratio adjustment slide valve (7) is moved by the load increase solenoid valve (9) and the load decrease solenoid valve (10) to adjust the real-time exhaust pressure in the slide valve chamber of the housing; In step 3, if the real-time exhaust pressure is greater than the upper limit of the rated exhaust pressure, the internal volume ratio adjustment slide valve (7) moves towards the intake end; if the real-time exhaust pressure is less than the lower limit of the rated exhaust pressure, the internal volume ratio adjustment slide valve (7) moves towards the exhaust end. When the volume ratio regulating slide valve (7) moves toward the intake end, the hydraulic oil flows through the internal oil passage of the exhaust end bearing seat (3) into the load-increasing solenoid valve (9). The hydraulic oil flowing out of the load-increasing solenoid valve (9) then enters the internal oil passage of the exhaust end bearing seat (3) into the internal oil passage of the exhaust end bearing seat cover plate (2), and then enters the internal oil passage of the end cover (1), flowing into the oil piston chamber of the exhaust end bearing seat cover plate (2) to drive the oil piston (13) to move, thereby driving the volume ratio regulating slide valve (7) to move toward the intake end. When the volume ratio regulating slide valve (7) moves toward the exhaust end, the hydraulic oil flows through the following path: the hydraulic oil enters the oil passage inside the end cover (1) through the oil piston chamber of the exhaust end bearing seat cover plate (2), then enters the oil passage inside the exhaust end bearing seat (3) through the oil passage inside the exhaust end bearing seat cover plate (2), passes through the unloading solenoid valve (10), enters the oil passage inside the housing (4) through the oil passage inside the exhaust end bearing seat (3), and finally enters the rotor chamber of the housing (4), causing the oil piston (13) to move, thereby causing the volume ratio regulating slide valve (7) to move toward the exhaust end.

2. The method for automatically adjusting the internal volume ratio of a screw compressor according to claim 1, characterized in that, In step 3, if the real-time exhaust pressure is between the upper and lower limits of the rated exhaust pressure, both the load-increasing solenoid valve (9) and the load-reducing solenoid valve (10) are closed.

3. An automatic volume ratio adjustment device for a screw compressor used to implement the automatic volume ratio adjustment method of the screw compressor as described in claim 1, characterized in that, Includes a housing (4), the exhaust end of the housing (4) is connected to an exhaust end bearing seat (3), and the outer end of the exhaust end bearing seat (3) is connected to an exhaust end bearing seat cover plate (2). An oil piston (13) is provided in the exhaust end bearing seat cover plate (2), a slide valve guide rod (11) is provided in both the exhaust end bearing seat (3) and the exhaust end bearing seat cover plate (2), and an internal volume ratio adjustment slide valve (7) is provided in the housing (4). The power output end of the oil piston (13) is connected to the slide valve guide rod (11), and the other end of the slide valve guide rod (11) is connected to the internal volume ratio regulating slide valve (7); The exhaust end bearing housing (3) is equipped with a load-increasing solenoid valve (9) and a load-reducing solenoid valve (10). The load-increasing solenoid valve (9) and the load-reducing solenoid valve (10) control the movement direction of the oil piston (13) through hydraulic oil. A pressure sensor (6) is inserted into the housing (4). The exhaust end of the internal volume ratio regulating slide valve (7) is provided with a through hole (5). One end of the through hole (5) is connected to the exhaust end of the rotor cavity, and the other end of the through hole (5) is connected to the pressure sensor (6). The pressure sensor (6) is connected to a computer control system, which is connected to a valve control piston PLC control module. The valve control piston PLC control module is connected to the load-increasing solenoid valve (9) and the load-reducing solenoid valve (10).

4. The automatic volume ratio adjustment device for a screw compressor according to claim 3, characterized in that, The bottom of the volume ratio regulating slide valve (7) is provided with a vent groove (15), and the through hole (5) and the pressure sensor (6) are connected through the vent groove (15).

5. The automatic volume ratio adjustment device for a screw compressor according to claim 3, characterized in that, The bottom of the volume ratio regulating slide valve (7) is provided with a guide groove (20), and the bottom of the housing (4) is provided with a slide valve guide key (8), the upper end of which extends into the guide groove (20).

6. The automatic volume ratio adjustment device for a screw compressor according to claim 3, characterized in that, The oil piston (13) has two circumferential sealing grooves, and sealing rings are installed in the sealing grooves.

7. The automatic volume ratio adjustment device for a screw compressor according to claim 3, characterized in that, The housing (4) has a housing shoulder (19) at the exhaust end and an intake end plate (14) on the intake end face of the housing (4).

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