Screw compressor slide valve regulating mechanism with oil-free pressure unloading function and control method thereof

Abstract

The application discloses a screw compressor slide valve adjusting mechanism with oil-free pressure unloading function, which comprises a flow piston, a volume ratio piston, a volume ratio slide valve, a flow slide valve, a compression spring, a guide rod, a three-position four-way electromagnetic reversing valve, a valve seat, a rudder and a valve core; the valve core is rotatably installed in the valve seat and is driven to rotate by the rudder; the valve core has an internal passage structure and can be driven to rotate to different working positions to control the communication between the oil pipe and each oil cavity, thereby selectively adjusting the flow of the flow slide valve and the volume ratio of the volume ratio slide valve. The screw compressor slide valve adjusting mechanism with oil-free pressure unloading function provided by the application can make the flow of the compressor to be unloaded to the minimum without the need of an oil pump to provide high oil pressure, so that the compressor is free from the dependence on the oil pump, unloading is performed by using the shutdown time, the startup time is shortened, and the structure is simplified.

Description

Technical Field

[0001] This invention belongs to the technical field of screw compressors, specifically relating to the function and control method of a screw compressor slide valve adjusting mechanism. Background Technology

[0002] Screw compressors are a type of positive displacement refrigeration compressor. They contain a pair of screw-shaped rotors that rotate within the compressor body, periodically completing the intake, compression, and exhaust processes. Due to their advantages such as a wide single-stage pressure ratio range, stepless flow rate adjustment, reliable operation, long service life, uniform air intake, smooth rotor operation, and no surge region, screw compressors have experienced rapid development and widespread application in the compressor industry.

[0003] Below the screw compressor rotor are flow rate valves and volumetric ratio valves. Both valves have arc surfaces corresponding to the outer circumference of the screw rotor, which, together with the arc surface of the compressor housing, form a seal against the outer circumference of the screw rotor; the flow rate valve also has a helical opening corresponding to the helix of the screw rotor.

[0004] When the flow rate valve and the volumetric ratio valve face are in contact, the outer circumference of the screw rotor is completely sealed, and the compressor flow rate is 100%. As the flow rate valve moves away from the volumetric ratio valve, the contact surface disappears, and the two valves form an opening below the rotor. The seal on the outer circumference of the screw rotor at this opening is broken, and compressed gas flows out towards the suction port. The larger the opening, the more gas flows away, the less gas is compressed, and the smaller the effective flow rate of the compressor. When the flow rate valve moves to its furthest position from the volumetric ratio valve, the compressor flow rate is 15%.

[0005] The position of the volume ratio spool valve end face determines the position of the flow rate spool valve's helical opening in the exhaust chamber when the flow rate spool valve end face is in contact with it. When the volume ratio spool valve end face is in the foremost position, the helical opening is also in the foremost position in the exhaust chamber, resulting in the largest exhaust volume and the smallest volume ratio, which is 2.0. Conversely, when the volume ratio spool valve end face is in the rearmost position, the helical opening is also in the rearmost position in the exhaust chamber, resulting in the smallest exhaust volume and the largest volume ratio, which is 5.0.

[0006] Two slide valves are connected to their respective pistons and cylinders. Two three-position four-way solenoid valves control the high and low pressure oil inflow and outflow directions of the two cylinders via dedicated valve seats, thereby driving the pistons and thus moving the slide valves to achieve regulation. The above is collectively referred to as the slide valve regulating mechanism of the screw compressor.

[0007] Currently, such institutions have the following drawbacks:

[0008] (1) The regulating function of the slide valve depends on the high and low oil pressure difference, and a special oil pump must be equipped to provide high and low pressure oil;

[0009] (2) Before starting the compressor, in order to reduce the starting current, the compressor should be started at the minimum flow rate. The specific procedure is as follows: before starting, start the oil pump to establish the high and low oil pressure difference, open the solenoid reversing valve to reduce the flow slide valve to the minimum position, and then start the compressor. There are many steps before starting, which takes a long time; the oil pump must be run in advance;

[0010] (3) Some units are not equipped with oil pumps due to structural issues. Due to the current functional limitations of the slide valve mechanism, the flow slide valve can only be reduced to a minimum during operation by using the high pressure at the exhaust end to facilitate the next start-up. If the compressor experiences a power outage, it cannot be automatically started next time and manual unloading is required. The current slide valve mechanism cannot well meet the operating requirements of oil pump-free compressor units;

[0011] (4) Flow regulation and volume ratio regulation will not be carried out at the same time, that is, the two control oil circuit systems will not work at the same time, and there is redundancy. Summary of the Invention

[0012] This invention is proposed to address the above-mentioned shortcomings, and aims to provide a screw compressor slide valve regulating mechanism and its control method with oil-free unloading function. This mechanism has an oil-free unloading function, which can reduce the compressor flow to a minimum without the need for an oil pump to provide high oil pressure, freeing the compressor from dependence on an oil pump, and also simplifies the structure and reduces costs.

[0013] To achieve the above objectives, the present invention provides a screw compressor slide valve regulating mechanism with oil-free unloading function, including a flow piston, a volume ratio piston, a volume ratio slide valve, a flow slide valve, a compression spring, a guide rod, a three-position four-way solenoid directional valve, a valve seat, a servo motor, and a valve core; one end of the guide rod is connected to the flow slide valve through a locking nut, and the other end is connected to the flow piston through a locking nut; the flow piston is disposed in the cylindrical cavity of the compressor and divides it into a first flow oil chamber and a second flow oil chamber; the first flow oil chamber is connected to a first flow oil pipe, and the second flow oil chamber is connected to a second flow oil pipe;

[0014] One end of the volume ratio slide valve is connected to the volume ratio piston via a locking nut. The volume ratio piston is disposed in the cylindrical cavity and divides it into a first volume ratio oil chamber and a second volume ratio oil chamber. The first volume ratio oil chamber is connected to a first volume ratio oil pipe, and the second volume ratio oil chamber is connected to a second volume ratio oil pipe. Both the flow slide valve and the volume ratio slide valve have axially penetrating circular holes inside. The compression spring is installed in the circular holes of the two slide valves and sleeved on the guide rod and is always in a compressed state to provide a spring force that pushes the flow slide valve and the volume ratio slide valve away from each other.

[0015] The valve seat is provided with a P port, a T port, an A port and a B port, and the three-position four-way solenoid directional valve is installed thereon. The P port is connected to the high-pressure output end of the high-pressure oil source through a high-pressure oil pipe, and the T port is connected to the oil tank through an oil tank pipe. The valve core has an A port and a B port for controlling the opening and closing of the oil circuit. The A port and the B port correspond to the A port and the B port of the valve core, respectively.

[0016] The valve core is rotatably mounted in the valve seat and driven to rotate by the servo motor. The valve core has an internal channel structure and can be driven to rotate to different working positions to control the communication between the oil pipe and each oil chamber, thereby selectively adjusting the flow rate of the flow slide valve and the volume ratio of the volume ratio slide valve. When the valve core is in the unloading position, the oil chambers on both sides of the flow piston and the oil chambers on both sides of the volume ratio piston are connected to each other, and the oil supply from the high-pressure oil source is cut off at the same time to eliminate the oil pressure difference on both sides of the two pistons. Under the elastic force of the compression spring, the flow slide valve is pushed to the minimum flow position and the volume ratio slide valve is pushed to the minimum volume ratio position, thereby realizing the oil pressure-free unloading function.

[0017] Furthermore, the end of the valve core extending out of the valve seat has a shaft extension structure and is connected to the output shaft of the servo motor via a transmission key and a transmission key sleeve, so that the servo motor can drive the valve core to rotate to different angles.

[0018] Furthermore, the valve core has three working positions, corresponding to a first predetermined angle, a second predetermined angle, and a third predetermined angle, respectively, and is used to realize flow regulation, volume ratio regulation, and oil-free unloading.

[0019] When the valve core is at the first predetermined angle, the A port and B port of the valve core are connected to the first flow oil pipe and the second flow oil pipe through the A port and B port of the valve seat, respectively, and the flow rate of the flow slide valve is regulated in cooperation with the three-position four-way solenoid directional valve.

[0020] When the valve core is at the second predetermined angle, the A and B ports of the valve core are connected to the first volume ratio oil pipe and the second volume ratio oil pipe through the A and B ports of the valve seat, respectively, and the volume ratio of the volume ratio slide valve is adjusted in cooperation with the three-position four-way solenoid directional valve.

[0021] When the valve core is at the third predetermined angle, its internal channel structure connects the oil chambers on both sides of the flow piston and the oil chambers on both sides of the volume ratio piston to each other, and simultaneously cuts off the oil supply from the high-pressure oil source to eliminate the oil pressure difference on both sides of the two pistons. Under the elastic force of the compression spring, the flow slide valve is pushed to the minimum flow position and the volume ratio slide valve is pushed to the minimum volume ratio position, thereby realizing the oil pressure-free unloading function.

[0022] Furthermore, a first flat groove is provided on the right side of the valve core, and a second flat groove is provided on the left side; when the valve core is at a third predetermined angle, the first flat groove connects the first volume ratio oil pipe and the second volume ratio oil pipe, the second flat groove connects the first flow oil pipe and the second flow oil pipe, and the A hole and B hole of the valve core are closed by the inner hole of the valve seat.

[0023] Furthermore, the first predetermined angle is 90°, used for flow rate adjustment; the second predetermined angle is 270°, used for volume ratio adjustment; and the third predetermined angle is 0°, used for oil-free unloading.

[0024] Furthermore, the valve core is provided with annular grooves on its A and B sides to ensure that the A port of the valve seat and the A hole of the valve core, and the B port of the valve seat and the B hole of the valve core are always connected within the corresponding angular range.

[0025] The present invention discloses a control method for a screw compressor slide valve adjustment mechanism with oil-free unloading function, comprising flow regulation, volume ratio regulation, and oil-free unloading steps. The flow regulation step involves rotating the valve core to the flow regulation position and adjusting the position of the flow slide valve by controlling the three-position four-way solenoid directional valve to switch the oil circuit. The volume ratio regulation step involves rotating the valve core to the volume ratio regulation position and adjusting the position of the volume ratio slide valve by controlling the three-position four-way solenoid directional valve to switch the oil circuit. The oil-free unloading step involves rotating the valve core to the unloading position after the compressor stops and there is no high-pressure oil supply, so that the oil pressure on both sides of the flow piston and the volume ratio piston is interconnected and balanced. The spring force of the compression spring pushes the flow slide valve to the minimum flow position and the volume ratio slide valve to the minimum volume ratio position.

[0026] Furthermore, in the flow regulation step, when the three-position four-way solenoid directional valve is in the straight-through position, high-pressure oil enters the first flow oil chamber through the A port of the valve seat and the A hole of the valve core, pushing the flow piston to the right to move the flow slide valve away from the volume ratio slide valve, thereby reducing the flow rate. Simultaneously, low-pressure oil is discharged back to the oil tank from the second flow oil chamber through the B hole of the valve core and the T port of the three-position four-way solenoid directional valve. When the three-position four-way solenoid directional valve is in the cross position, high-pressure oil enters through the B port of the valve seat... The flow path enters the second flow oil chamber through the B hole of the valve core, pushing the flow piston to the left to move the flow slide valve toward the volume ratio slide valve, thereby increasing the flow rate. Low-pressure oil is discharged from the first flow oil chamber through the A hole of the valve core and the T port of the three-position four-way solenoid valve back to the oil tank. When the flow slide valve moves to the target position, the three-position four-way solenoid valve is switched to the cut-off position, so that the oil in the first flow oil chamber and the second flow oil chamber is sealed and locked, thereby fixing the flow slide valve in that position.

[0027] Furthermore, in the volume ratio adjustment step, when the three-position four-way solenoid valve is in the straight-through position, high-pressure oil enters the first volume ratio oil chamber through the A port of the valve seat and the A hole of the valve core, pushing the volume ratio piston to the right, thereby causing the volume ratio slide valve to move to the right to increase the volume ratio. Low-pressure oil is discharged from the second volume ratio oil chamber through the B hole of the valve core and the T port of the three-position four-way solenoid valve back to the oil tank. When the three-position four-way solenoid valve is in the cross position, high-pressure oil enters the first volume ratio oil chamber through the B port of the valve seat and the A hole of the valve core, pushing the volume ratio piston to the right, thereby causing the volume ratio slide valve to move to the right to increase the volume ratio. The valve core's B-hole enters the second volume ratio oil chamber, pushing the volume ratio piston to the left, thereby causing the volume ratio slide valve to move to the left to reduce the volume ratio. Low-pressure oil flows from the first volume ratio oil chamber through the valve core's A-hole and the three-position four-way solenoid valve's T-port back to the oil tank. When the volume ratio slide valve moves to the target position, the three-position four-way solenoid valve is switched to the cut-off position, so that the oil in the first and second volume ratio oil chambers is sealed and locked, thereby fixing the volume ratio slide valve in that position.

[0028] Furthermore, in the oil-free unloading step, after the compressor stops, the valve core is rotated to the unloading position, so that the second flat groove of the valve core connects the first flow oil pipe and the second flow oil pipe, the first flat groove connects the first volume ratio oil pipe and the second volume ratio oil pipe, and the A hole and B hole of the valve core are closed by the inner hole of the valve seat, thereby making the oil pressure on both sides of the flow piston and the volume ratio piston interconnected and pressure balanced; in the state of no pressure difference, the elastic force of the compression spring pushes the flow slide valve to the minimum flow position and pushes the volume ratio slide valve to the minimum volume ratio position.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] Firstly, this invention features oil-free unloading, eliminating the need for an oil pump to provide high oil pressure and allowing the compressor flow rate to be reduced to a minimum, thus freeing the compressor from dependence on an oil pump. This invention utilizes a special valve core channel structure to connect the oil chambers on both sides of the slide valve piston, simultaneously cutting off the high-pressure oil supply. Under the action of the compression spring, the flow rate slide valve and the volume ratio slide valve are automatically pushed to their minimum positions, achieving the function of unloading the compressor to a minimum load state without the need for an oil pump to provide high oil pressure. This design eliminates the dependence of traditional slide valve regulation on high and low oil pressure differences and the need for a dedicated oil pump, freeing the compressor from dependence on an oil pump, simplifying the system structure, and reducing equipment costs.

[0031] Secondly, this invention utilizes downtime for unloading, shortening startup time and reducing startup load. Because of its oil-free automatic unloading capability, the compressor does not require an oil pump to establish an oil pressure difference for pre-unloading before startup, reducing startup steps and preparation time. The compressor can start directly under minimum load, significantly reducing starting current surges and starting torque load, avoiding tripping that may occur during full-load startup, and improving startup safety and speed.

[0032] Thirdly, this invention features automatic unloading upon shutdown, adapting to the operation of oil-pump-free units. After the compressor stops, the valve core rotates to the unloading position, automatically balancing the oil pressure on both sides. The compression spring then resets the slide valve to its minimum capacity / minimum volume ratio position. Thus, even if the compressor suddenly stops due to power failure, the slide valve can automatically unload and reset under oil-pressure-free conditions, preparing for the next startup without manual intervention. This avoids the risk of traditional units failing to unload after shutdown, leading to a full-load start-up. This invention effectively meets the operational requirements of oil-pump-free compressor units, improving the system's self-recovery capability and operational reliability after power failure.

[0033] Fourth, this invention integrates flow regulation and volume ratio regulation into one unit, reducing control redundancy. This invention uses a single valve core to switch between controlling the flow rate slide valve and the volume ratio slide valve at different angles, combining the two regulation functions into one. By setting a first predetermined angle (e.g., 90°) for flow regulation and a second predetermined angle (e.g., 270°) for volume ratio regulation, a single mechanism can handle both regulation needs. Since capacity regulation and volume ratio regulation do not need to be performed simultaneously, the two independent oil circuits and solenoid valves configured for this purpose in traditional designs actually have functional redundancy. This invention integrates them, allowing the same set of valves to switch and control them separately, eliminating redundant control oil circuits and components, and significantly simplifying the structure of the slide valve regulation system. This not only reduces the number of components and potential failure points, lowering manufacturing and maintenance costs, but also makes the control logic more unified and concise, improving the reliability of the system.

[0034] Fifth, this invention employs a servo valve core drive, enabling precise and rapid adjustment and control. The valve core is rotated and positioned by a servo motor, with its end rigidly connected to the servo motor output shaft via a shaft extension and transmission key, ensuring reliable transmission. The servo drive can precisely rotate the valve core to predetermined angular positions (e.g., unloading position 0°, flow rate adjustment position 90°, volume ratio adjustment position 270°), making switching operations rapid and accurate, without positioning errors or lag. This guarantees the response speed and control precision of the spool valve adjustment, allowing for rapid switching between capacity adjustment and volume ratio adjustment modes according to operating conditions, resulting in smoother and more reliable operation.

[0035] Sixth, the valve core channel of this invention is rationally designed, ensuring smooth oil circuit switching and lockable positioning. The annular groove structure on both sides of the valve core ensures that within a certain angle range of valve core rotation, port A of the valve seat is always connected to port A of the valve core, and port B is always connected to port B. This prevents interruption of the oil circuit due to slight angular deviations in the valve core, thus ensuring smooth and stable oil pressure control switching and avoiding hydraulic shock or control failure. Furthermore, after the spool valve is adjusted to the target position, switching the three-position four-way solenoid valve to the neutral position closes the high and low pressure oil circuits, locking them in the oil chambers on both sides of the spool valve piston, forming a hydraulic lock. This locking mechanism firmly fixes the spool valve in the target position, preventing spool valve retraction or drift due to pressure fluctuations, ensuring the stability of the compressor's operating conditions and the durability of its regulating effect during partial load operation. Attached Figure Description

[0036] Figure 1 This is a cross-sectional view of the slide valve adjustment mechanism of the screw compressor with oil-free unloading function according to an embodiment of the present invention;

[0037] Figure 2 A schematic diagram illustrating the adjustment principle of the slide valve adjustment mechanism for a screw compressor with oil-free unloading function provided in an embodiment of the present invention;

[0038] Figure 3 This is a schematic diagram showing the valve core at 90°.

[0039] Figure 4 This is a schematic diagram showing the valve core at 270°.

[0040] Figure 5 This is a schematic diagram showing the valve core at 0°.

[0041] Figure 6 This is a schematic diagram of the internal structure of the valve seat according to an embodiment of the present invention;

[0042] Figure 7 This is a schematic diagram showing the connection between the valve seat and the pipeline;

[0043] Figure 8 This is a schematic diagram of the annular groove;

[0044] Figure 9 This is a three-dimensional structural diagram of the valve core according to an embodiment of the present invention;

[0045] Figure 10 This is a three-dimensional structural diagram of the valve seat according to an embodiment of the present invention;

[0046] Figure 11 This is a schematic diagram illustrating the operation of the volume ratio adjustment function in an embodiment of the present invention;

[0047] Figure 12 This is a schematic diagram illustrating the operation of the hydraulic unloading function in an embodiment of the present invention.

[0048] In the diagram: 1-First flow rate oil chamber; 2-Flow rate piston; 3-Second flow rate oil chamber; 4-First volume ratio oil chamber; 5-Volume ratio piston; 6-Second volume ratio oil chamber; 7-Volume ratio slide valve; 8-Flow rate slide valve; 9-Compression spring; 10-Guide rod; 11-Second volume ratio oil pipe; 12-First volume ratio oil pipe; 13-Three-position four-way solenoid directional valve; 14-Valve seat; 15-Second flow rate oil pipe; 16-First flow rate oil pipe; 17-Steering motor; 18-Transmission key sleeve; 19-Transmission key; 20-Valve core; 21-High pressure oil pipe; 22-Oil tank oil pipe; 23-End cap; 24-Annular groove; C1-First flat groove; C2-Second flat groove. Detailed Implementation

[0049] The following detailed examples illustrate the implementation of this invention, but they do not constitute a limitation on the invention and are merely illustrative. Furthermore, the advantages of this invention will become clearer and easier to understand by explaining them. The directions mentioned in the description, such as "up," "down," "left," "right," "front," and "back," correspond only to the directions shown in the accompanying drawings and do not represent actual directions.

[0050] See Figure 1The present invention relates to a screw compressor slide valve regulating mechanism with oil-free unloading function, comprising a flow piston 2, a volume ratio piston 5, a volume ratio slide valve 7, a flow slide valve 8, a compression spring 9, a guide rod 10, a three-position four-way solenoid directional valve 13, a valve seat 14, a servo motor 17, and a valve core 20; one end of the guide rod 10 is connected to the flow slide valve 8 via a locking nut, and the other end is connected to the flow piston 2 via a locking nut. The flow piston 2 is disposed within the cylindrical cavity of the compressor and divides it into a first flow oil chamber 1 and a second flow oil chamber 3. The first flow oil chamber 1 is connected to a first flow oil pipe. 16 is connected, the second flow oil chamber 3 is connected to the second flow oil pipe 15; one end of the volume ratio slide valve 7 is connected to the volume ratio piston 5 through a locking nut, the volume ratio piston 5 is set in the cylindrical cavity and divides it into the first volume ratio oil chamber 4 and the second volume ratio oil chamber 6, the first volume ratio oil chamber 4 is connected to the first volume ratio oil pipe 12, and the second volume ratio oil chamber 6 is connected to the second volume ratio oil pipe 11; both the flow slide valve 8 and the volume ratio slide valve 7 are provided with axially penetrating round holes, and the compression spring 9 is installed in the round holes of the two slide valves and sleeved on the guide rod 10 and is always under compression. The valve seat 14 is provided with a P port, a T port, an A port, and a B port, and a three-position four-way solenoid directional valve 13 is installed thereon. The P port is connected to the high-pressure output terminal of the high-pressure oil source through the high-pressure oil pipe 21, and the T port is connected to the oil tank through the oil tank pipe 22. The valve core 20 has an A port and a B port for controlling the oil circuit opening and closing. The A port and the B port correspond to the A port and the B port of the valve core 20, respectively. The valve core 20 is rotatably installed in the valve seat 14 and is driven to rotate by the servo motor 17. The valve core 20 has an internal channel structure. The mechanism can be driven to rotate to different working positions to control the connection between the oil pipe and each oil chamber, thereby selectively adjusting the flow rate of the flow valve 8 and the volume ratio of the volume ratio valve 7. When the valve core 20 is in the unloading position, the oil chambers on both sides of the flow piston 2 and the oil chambers on both sides of the volume ratio piston 5 are connected to each other, and the oil supply of the high-pressure oil source is cut off at the same time to eliminate the oil pressure difference on both sides of the two pistons. Under the elastic force of the compression spring 9, the flow valve 8 is pushed to the minimum flow position and the volume ratio valve 7 is pushed to the minimum volume ratio position, thereby realizing the oil pressure-free unloading function.

[0051] In this embodiment, the guide rod 10 of the screw compressor slide valve adjusting mechanism with oil-free unloading function is connected to the flow slide valve 8 at its right end via a locking nut, and to the flow piston 2 at its left end via a locking nut. All three can move axially within the cylindrical cavity of the compressor. The flow piston 2 divides the cylinder into a first flow oil chamber 1 and a second flow oil chamber 3. The first flow oil chamber 1 is connected to the first flow oil pipe 16, and the second flow oil chamber 3 is connected to the second flow oil pipe 15. The volume ratio slide valve 7 is connected to the volume ratio piston 5 at its left end via a locking nut. Both can move axially within the cylindrical cavity of the compressor. The volume ratio piston 5 divides the cylinder structure within the compressor cavity into a first volume ratio oil chamber 4 and a second volume ratio oil chamber 6. The first volume ratio oil chamber 4 is connected to the first volume ratio oil pipe 12, and the second volume ratio oil chamber 6 is connected to the second volume ratio oil pipe 11. Both the volumetric ratio slide valve 7 and the flow rate slide valve 8 have internal circular hole structures. A compression spring 9 is installed within these circular hole structures and is fitted onto the guide rod 10. When the flow rate slide valve 8 and the volumetric ratio slide valve 7 move freely within the compressor's cylindrical cavity, the compression spring 9 remains in a compressed state. The valve seat 14 is installed above the compressor's volumetric ratio oil chamber. A three-position four-way solenoid directional valve 13 is installed above the valve seat 14. The first flow rate oil pipe 16, the second flow rate oil pipe 15, the first volumetric ratio oil pipe 12, and the second volumetric ratio oil pipe 11 are connected to the valve seat 14.

[0052] See Figures 6-8 A three-position four-way solenoid directional valve 13 is mounted on the upper end face of valve seat 14. Valve seat 14 is equipped with ports P, T, A, and B. High-pressure oil from the high-pressure oil source enters valve seat 14 through high-pressure oil pipe 21 and then enters the three-position four-way solenoid directional valve 13 through port P. The three-position four-way solenoid directional valve 13 can switch between three positions: straight-through, cross-connection, and cut-off. When the three-position four-way solenoid directional valve 13 is in different positions, it connects or disconnects ports P, T, A, and B of valve seat 14 as required. High-pressure oil from the high-pressure oil source enters port P of valve seat 14 through high-pressure oil pipe 21. In the straight-through position, port P of valve seat 14 is connected to port A, and port B is connected to port T; in the cross-connection position, port P of valve seat 14 is connected to port B, and port A is connected to port T; in the cut-off position, ports P, T, A, and B of valve seat 14 are not connected to each other. Low-pressure return oil flows into the oil tank pipe 22 through the T port of valve seat 14 and returns to the oil tank. In the straight-through position, high-pressure oil is output from port A, and low-pressure oil enters from port B. In the cross position, high-pressure oil is output from port B, and low-pressure oil enters from port A. After entering the three-position four-way solenoid directional valve 13, the low-pressure oil flows back to the T port of valve seat 14 through its T port. The T port of valve seat 14 is connected to the oil tank through the oil tank pipe 22, allowing the low-pressure oil to flow back to the oil tank. In the cut-off position, all four oil ports (P, T, A, and B) are closed; at this time, the oil in the oil holes inside valve seat 14 and valve core 20 no longer flows.

[0053] The A port of valve seat 14 communicates with the A-side annular groove of valve core 20, and the A-side annular groove communicates with the A-hole of valve core 20. Due to the annular groove structure, the A port of valve seat 14 remains connected to the A-hole of valve core 20 regardless of the angle to which valve core 20 is rotated. Similarly, the B port of valve seat 14 communicates with the B-side annular groove of valve core 20, and the B-side annular groove communicates with the B-hole of valve core 20. Therefore, the B port of valve seat 14 remains connected to the B-hole of valve core 20.

[0054] The valve core 20 has a shaft extension structure that extends beyond the end cover 23. A transmission key 19 is provided on the shaft extension of the valve core 20, which connects to a transmission key sleeve 18. The transmission key sleeve 18 is connected to the shaft extension of the servo motor 17. In this way, the servo motor 17 can drive the valve core 20 to rotate. Figures 2-5 As shown, rotating the valve core 20 to different angles (0° / 90° / 270°) allows the A and B ports of the valve core 20 to connect to the flow rate oil passage or volume ratio oil passage of the valve seat 14, or to be disconnected from the oil passage of the valve seat 14. By applying different electrical signals to the servo motor 17 of the slide valve regulating mechanism, the rotation angle of the valve core 20 is controlled to realize the compressor's flow rate regulation, volume ratio regulation, and oil pressure unloading functions, respectively.

[0055] The control method for the slide valve regulating mechanism of the screw compressor with oil-free unloading in this embodiment includes the following steps:

[0056] (a) The process of compressor flow regulation

[0057] 1. Flow unloading: Input a 0.5ms pulse signal to the servo motor 17 to rotate the valve core 20 to a 90° position. Figure 6 The state shown is as follows. At this time, the A and B ports of the valve core 20 are connected to the flow oil circuit inside the valve seat 14; the three-position four-way solenoid directional valve 13 is placed in the straight-through position (the P port of the valve seat 14 is connected to the A port, and the B port is connected to the T port). High-pressure oil from the high-pressure oil source enters the P port of the valve seat 14 through the high-pressure oil pipe 21, connects to the A port of the valve seat 14 through the straight-through position, and then enters the first flow oil pipe 16 connected to the valve seat 14 through the A-side annular groove-A port of the valve core 20, flows into the first flow oil chamber 1, drives the flow piston 2 to move to the right, and drives the flow slide valve 8 to move to the right; the flow slide valve 8 gradually moves away from the volume ratio slide valve 7, the opening between the two becomes larger and larger, and the effective flow of the compressor gradually decreases. Meanwhile, the low-pressure oil from the second flow oil chamber 3 enters the valve seat 14 through the second flow oil pipe 15, then flows through the B-side annular groove of the valve core 20 to the B port of the valve seat 14, and is connected to the T port of the valve seat 14 through the straight-through position, finally returning to the oil tank through the oil tank pipe 22. When the flow piston 2 moves to the right limit position, the opening between the flow slide valve 8 and the volume ratio slide valve 7 reaches its maximum, that is, about 15% of the minimum flow.

[0058] 2. Flow Increase: With valve core 20 at 90°, place the three-position four-way solenoid directional valve 13 in the cross position (the P port of valve seat 14 is connected to the B port, and the A port is connected to the T port). High-pressure oil enters the P port of valve seat 14 through high-pressure oil pipe 21, connects to the B port of valve seat 14 through the cross position, and then enters the second flow oil pipe 15 connected to valve seat 14 through the B-side annular groove-B hole of valve core 20, flowing into the second flow oil chamber 3, pushing the flow piston 2 to move to the left, and causing the flow slide valve 8 to move to the left; the flow slide valve 8 gradually approaches the volume ratio slide valve 7, and the opening between the two becomes smaller and smaller, and the effective flow of the compressor gradually increases. At the same time, the low-pressure oil in the first flow oil chamber 1 enters the valve seat 14 through the first flow oil pipe 16, then flows to the A port of valve seat 14 through the A hole-A-side annular groove of valve core 20, and connects to the T port of valve seat 14 through the cross position, and finally returns to the oil tank through the oil tank pipe 22. When the flow piston 2 moves to the left limit position, the left end face of the flow slide valve 8 is pressed against the right end face of the volume ratio slide valve 7, reaching 100% maximum flow.

[0059] 3. Fixed Flow Rate: When the flow rate slide valve 8 is in any position, the three-position four-way solenoid directional valve 13 is placed in the cut-off position (the P, T, A, and B ports of the valve seat 14 are not connected to each other), cutting off the external communication with the valve seat 14. The hydraulic oil in the first flow rate oil chamber 1 and the second flow rate oil chamber 3 is sealed in its respective oil chamber, and the flow rate piston 2 is no longer moved by hydraulic pressure. At this time, although the flow rate slide valve 8 still has a slight tendency to move left and right under the combined force of the spring force of the compression spring 9 and the gas pressure in the compressor cavity, the volume of these two oil chambers cannot be changed because the hydraulic oil in the first flow rate oil chamber 1 and the second flow rate oil chamber 3 cannot flow out or in, so the flow rate piston 2 cannot move. If the combined force of the compression spring 9 acts to the left, the oil pressure in the first flow rate oil chamber 1 increases, offsetting the combined force; if the combined force acts to the right, the oil pressure in the second flow rate oil chamber 3 increases, similarly offsetting the combined force. Ultimately, the position of the flow piston 2 in the cylinder remains unchanged (as if "locked"), and correspondingly the position of the flow slide valve 8 also remains unchanged, meaning that the compressor flow is fixed at the current state.

[0060] (II) The process of adjusting the volume ratio of the compressor

[0061] 1. Increased volume ratio: Input a 1ms pulse signal to the servo motor 17 to rotate the valve core 20 to a 270° position, such as... Figure 11The state shown is as follows. At this time, the A and B ports of the valve core 20 are connected to the corresponding volume ratio oil circuit inside the valve seat 14; the three-position four-way solenoid directional valve 13 is placed in the straight-through position (the P port of the valve seat 14 is connected to the A port, and the B port is connected to the T port). High-pressure oil from the high-pressure oil source enters the P port of the valve seat 14 through the high-pressure oil pipe 21, connects to the A port of the valve seat 14, and then enters the first volume ratio oil pipe 12 connected to the valve seat 14 through the A-side annular groove-A port of the valve core 20, flows into the first volume ratio oil chamber 4, drives the volume ratio piston 5 to move to the right, and the rightward movement of the volume ratio piston 5 drives the volume ratio slide valve 7 to move to the right, increasing the volume ratio. When the volume ratio piston 5 moves to the right, the low-pressure oil in the second volume ratio oil chamber 6 flows back through the second volume ratio oil pipe 11. The low-pressure oil then enters the corresponding oil hole of the valve seat 14 through the second volume ratio oil pipe 11, then enters the B hole of the valve core 20, passes through the B-side annular groove, returns to the B port of the valve seat 14, enters the three-position four-way solenoid directional valve 13 from the B port, and enters the T port of the valve seat 14 through the straight-through position, and returns to the oil tank through the oil tank pipe 22. When the volume ratio piston 5 moves to the right limit position, the volume ratio is at its maximum, i.e., 5.0.

[0062] If the volume ratio slide valve 7 is blocked by the flow slide valve 8 on the right side during the rightward movement of the volume ratio slide valve 7, the "flow unloading" process is executed first, causing the flow slide valve 8 to temporarily move to the right to make way for the volume ratio slide valve 7; after the volume ratio slide valve 7 is in place, the "flow loading" process is executed to move the flow slide valve 8 to the left to the required position.

[0063] 2. Volumetric Ratio Reduction: With valve core 20 at the 270° position, place the three-position four-way solenoid directional valve 13 in the cross position (the P port of valve seat 14 is connected to the B port, and the A port is connected to the T port). High-pressure oil from the high-pressure oil source enters the three-position four-way solenoid directional valve 13 through the P port of valve seat 14 via high-pressure oil pipe 21, and after output, enters the B port of valve seat 14, passes through the annular groove of valve core 20, enters the B hole of valve core 20, and then enters the second volumetric ratio oil pipe 11 connected to valve seat 14, and then enters the second volumetric ratio oil chamber 6. Under the action of high-pressure oil, the volumetric ratio piston 5 moves to the left, and the leftward movement of the volumetric ratio piston 5 drives the volumetric ratio slide valve 7 to move to the left, thus reducing the internal volumetric ratio of the compressor. Meanwhile, the leftward movement of the volume ratio piston 5 will cause the low-pressure oil in the first volume ratio oil chamber 4 to flow back through the first volume ratio oil pipe 12. The low-pressure oil then enters the corresponding oil hole of the valve seat 14 through the first volume ratio oil pipe 12, then enters the A hole of the valve core 20, passes through the A-side annular groove, returns to the A port of the valve seat 14, enters the three-position four-way solenoid directional valve from the A port, and finally flows out from the T port of the valve seat 14, returning to the oil tank through the oil tank pipe 22. When the volume ratio piston 5 moves to the left limit position, the volume ratio is at its minimum, i.e., 2.0.

[0064] 3. Fixed Volume Ratio: When the volume ratio spool valve 7 is in any position, the three-position four-way solenoid directional valve 13 is placed in the cut-off position (the P, T, A, and B ports of valve seat 14 are not connected to each other), cutting off the oil circuit connection with valve seat 14. The hydraulic oil in the first volume ratio chamber 4 and the second volume ratio chamber 6 is now sealed within their respective chambers, and the volume ratio piston 5 is no longer moved by hydraulic pressure. Although the volume ratio spool valve 7 still tends to move to the left under the spring force of the compression spring 9, the volume of these two chambers cannot change because the hydraulic oil in the first volume ratio chamber 4 and the second volume ratio chamber 6 cannot flow, thus preventing the volume ratio piston 5 from moving. If the spring force of spring 9 acts to the left, the oil pressure in the first volume ratio chamber 4 increases, counteracting this force. Ultimately, the position of the volume ratio piston 5 in the cylinder remains unchanged (as if "locked"), and correspondingly, the position of the volume ratio spool valve 7 also remains unchanged, maintaining the current volume ratio state.

[0065] (iii) Hydraulic unloading

[0066] After the unit shuts down, there is no high-pressure oil in the high-pressure oil pipe 21. A 1.5ms pulse signal is input to the servo motor 17, causing the valve core 20 to rotate to the 0° position. Figure 12 The state shown is as follows. At this time, both holes A and B of the valve core 20 are closed by the inner hole of the valve seat 14. The second flat groove C2 on the left side of the valve core 20 connects the first flow oil pipe 16 and the second flow oil pipe 15 to each other, thereby connecting the first flow oil chamber 1 and the second flow oil chamber 3 to each other. The oil pressure on both sides of the flow piston 2 is equal, and the flow piston 2 is in a "free" state in the flow cylinder. The first flat groove C1 on the right side of the valve core 20 connects the first volume ratio oil pipe 12 and the second volume ratio oil pipe 11 to each other, thereby connecting the first volume ratio oil chamber 4 and the second volume ratio oil chamber 6 to each other. The oil pressure on both sides of the volume ratio piston 5 is equal, and the volume ratio piston 5 is in a "free" state in the volume ratio cylinder.

[0067] After the compressor stops, the high-pressure side pressure decreases and the low-pressure side pressure increases, and the high and low pressures tend to be equal, so the resultant pressure on both sides of the slide valve approaches zero. The compression spring 9 between the volume ratio slide valve 7 and the flow rate slide valve 8 is always in a compressed state. The spring force of the compression spring 9 pushes the volume ratio slide valve 7 to the left and the flow rate slide valve 8 to the right.

[0068] Under the elastic force of the compression spring 9, the flow slide valve 8 drives the flow piston 2 to move to the right: the oil in the second flow oil chamber 3 is squeezed into the second flow oil pipe 15, enters the valve seat 14, flows into the first flow oil pipe 16 through the second flat groove C2 of the valve core 20 and returns to the first flow oil chamber 1; under the spring force of the compression spring 9, the flow slide valve 8 and the flow piston 2 move to the right continuously until the right limit position, and stop.

[0069] Similarly, the volume ratio slide valve 7 drives the volume ratio piston 5 to move to the left: the oil in the first volume ratio oil chamber 4 is squeezed into the first volume ratio oil pipe 12, enters the valve seat 14, flows into the second volume ratio oil pipe 11 through the first flat groove C1 of the valve core 20 and returns to the second volume ratio oil chamber 6; under the action of the spring force of the compression spring 9, the volume ratio slide valve 7 and the volume ratio piston 5 continuously move to the left until the left limit position, and stop.

[0070] In this state, the flow piston 2 moves to the right limit position, and the opening between the flow slide valve 8 and the volume ratio slide valve 7 reaches its maximum, i.e., 15% of the minimum flow rate; when the volume ratio piston 5 moves to the left limit position, the volume ratio is at its minimum, i.e., 2.0. The entire mechanism operates under the spring force of the compression spring 9, without the need for an oil pump or unit to provide high-pressure oil, thus achieving oil-free unloading function.

[0071] The above are merely specific embodiments of the present invention. It should be noted that any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the protection scope of the present invention. Any other aspects not described in detail are prior art.

Claims

1. A screw compressor slide valve adjusting mechanism with oil-free unloading function, characterized in that: It includes a flow piston (2), a volume ratio piston (5), a volume ratio slide valve (7), a flow slide valve (8), a compression spring (9), a guide rod (10), a three-position four-way solenoid directional valve (13), a valve seat (14), a servo motor (17), and a valve core (20); one end of the guide rod (10) is connected to the flow slide valve (8) through a locking nut, and the other end is connected to the flow piston (2) through a locking nut; the flow piston (2) is set in the cylindrical cavity of the compressor and is divided into a first flow oil chamber (1) and a second flow oil chamber (3), the first flow oil chamber (1) is connected to the first flow oil pipe (16), and the second flow oil chamber (3) is connected to the second flow oil pipe (15); One end of the volume ratio slide valve (7) is connected to the volume ratio piston (5) through a locking nut. The volume ratio piston (5) is disposed in the cylindrical cavity and divided into a first volume ratio oil chamber (4) and a second volume ratio oil chamber (6). The first volume ratio oil chamber (4) is connected to the first volume ratio oil pipe (12), and the second volume ratio oil chamber (6) is connected to the second volume ratio oil pipe (11). The flow slide valve (8) and the volume ratio slide valve (7) are both provided with axially penetrating circular holes. The compression spring (9) is installed in the circular holes of the two slide valves and sleeved on the guide rod (10) and is always in a compressed state to provide elastic force to the flow slide valve (8) and the volume ratio slide valve (7) to move away from each other. The valve seat (14) is provided with a P port, a T port, an A port and a B port, and the three-position four-way solenoid directional valve (13) is installed thereon. The P port is connected to the high-pressure output end of the high-pressure oil source through a high-pressure oil pipe (21), and the T port is connected to the oil tank through an oil tank pipe (22). The valve core (20) has an A port and a B port for controlling the opening and closing of the oil circuit. The A port and the B port correspond to the A port and the B port of the valve core (20) respectively. The valve core (20) is rotatably mounted in the valve seat (14) and driven to rotate by the servo motor (17). The valve core (20) has an internal channel structure and can be driven to rotate to different working positions to control the connection between the oil pipe and each oil chamber, thereby selectively adjusting the flow rate of the flow valve (8) and the volume ratio of the volume ratio valve (7). When the valve core (20) is in the unloading position, the oil chambers on both sides of the flow piston (2) and the oil chambers on both sides of the volume ratio piston (5) are connected to each other, and the oil supply of the high pressure oil source is cut off at the same time to eliminate the oil pressure difference on both sides of the two pistons. Under the elastic force of the compression spring (9), the flow valve (8) is pushed to the minimum flow position and the volume ratio valve (7) is pushed to the minimum volume ratio position, thereby realizing the unloading function without oil pressure.

2. The screw compressor slide valve adjusting mechanism with oil-free unloading function according to claim 1, characterized in that: The valve core (20) has a shaft extension structure at the end extending out of the valve seat (14), and is connected to the output shaft of the servo motor (17) via a transmission key (19) and a transmission key sleeve (18) so that the servo motor (17) can drive the valve core (20) to rotate to different angles.

3. The screw compressor slide valve adjusting mechanism with oil-free unloading function according to claim 2, characterized in that: The valve core (20) has three working positions, corresponding to the first predetermined angle, the second predetermined angle and the third predetermined angle, respectively, and is used to realize flow regulation, volume ratio regulation and oil-free unloading; When the valve core (20) is at the first predetermined angle, the A and B holes of the valve core (20) are connected to the first flow oil pipe (16) and the second flow oil pipe (15) through the A and B ports of the valve seat (14) respectively, and the flow of the flow slide valve (8) is regulated in cooperation with the three-position four-way solenoid directional valve (13). When the valve core (20) is at the second predetermined angle, the A and B holes of the valve core (20) are connected to the first volume ratio oil pipe (12) and the second volume ratio oil pipe (11) through the A and B ports of the valve seat (14) respectively, and the volume ratio of the volume ratio slide valve (7) is adjusted in cooperation with the three-position four-way solenoid directional valve (13). When the valve core (20) is at the third predetermined angle, the oil chambers on both sides of the flow piston (2) and the oil chambers on both sides of the volume ratio piston (5) are connected to each other, and the oil supply of the high pressure oil source is cut off at the same time to eliminate the oil pressure difference on both sides of the two pistons. Under the elastic force of the compression spring (9), the flow slide valve (8) is pushed to the minimum flow position and the volume ratio slide valve (7) is pushed to the minimum volume ratio position, thereby realizing the oil pressure unloading function.

4. The screw compressor slide valve adjusting mechanism with oil-free unloading function according to claim 3, characterized in that: The valve core (20) has a first flat groove (C1) on the right side and a second flat groove (C2) on the left side. When the valve core (20) is at a third predetermined angle, the first flat groove (C1) connects the first volume ratio oil pipe (12) and the second volume ratio oil pipe (11), the second flat groove (C2) connects the first flow oil pipe (16) and the second flow oil pipe (15), and the A hole and B hole of the valve core (20) are closed by the inner hole of the valve seat (14).

5. The screw compressor slide valve adjusting mechanism with oil-free unloading function according to claim 4, characterized in that: The first predetermined angle is 90°, used for flow rate adjustment; the second predetermined angle is 270°, used for volume ratio adjustment; and the third predetermined angle is 0°, used for oil-free unloading.

6. The screw compressor slide valve adjusting mechanism with oil-free unloading function according to claim 5, characterized in that: The valve core (20) has annular grooves (24) on its A and B sides respectively, which are used to ensure that the A port of the valve seat (14) and the A hole of the valve core (20), and the B port of the valve seat (14) and the B hole of the valve core (20) are always connected within the corresponding angle range.

7. A control method for a screw compressor slide valve adjusting mechanism with oil-free unloading function as described in any one of claims 4 to 6, characterized in that: The process includes flow regulation, volume ratio regulation, and oil-free unloading steps. The flow regulation step involves rotating the valve core (20) to the flow regulation position and adjusting the position of the flow slide valve (8) by controlling the three-position four-way solenoid directional valve (13) to switch the oil circuit. The volume ratio regulation step involves rotating the valve core (20) to the volume ratio regulation position and adjusting the position of the volume ratio slide valve (7) by controlling the three-position four-way solenoid directional valve (13) to switch the oil circuit. The oil-free unloading step involves rotating the valve core (20) to the unloading position after the compressor stops and there is no high-pressure oil supply, so that the oil pressure on both sides of the flow piston (2) and the volume ratio piston (5) is connected and the pressure is balanced. The elastic force of the compression spring (9) pushes the flow slide valve (8) to the minimum flow position and pushes the volume ratio slide valve (7) to the minimum volume ratio position.

8. The control method according to claim 7, characterized in that: In the flow regulation step, when the three-position four-way solenoid valve (13) is in the straight-through position, high-pressure oil enters the first flow oil chamber (1) through the A port of the valve seat (14) and the A port of the valve core (20), pushing the flow piston (2) to the right to drive the flow slide valve (8) away from the volume ratio slide valve (7), thereby reducing the flow rate. At the same time, low-pressure oil is discharged back to the oil tank from the second flow oil chamber (3) through the B port of the valve core (20) and the T port of the three-position four-way solenoid valve (13); when the three-position four-way solenoid valve (13) is in the cross position, high-pressure oil enters the first flow oil chamber (1) through the B port of the valve seat (14) and the A port of the valve core (20), pushing the flow piston (2) to the right to drive the flow slide valve (8) away from the volume ratio slide valve (7), thereby reducing the flow rate. The B hole of the valve core (20) enters the second flow oil chamber (3), pushing the flow piston (2) to move to the left to drive the flow slide valve (8) toward the volume ratio slide valve (7), thereby increasing the flow rate. Low-pressure oil is discharged from the first flow oil chamber (1) through the A hole of the valve core (20) and the T port of the three-position four-way solenoid directional valve (13) back to the oil tank. When the flow slide valve (8) moves to the target position, the three-position four-way solenoid directional valve (13) is switched to the cut-off position, so that the oil in the first flow oil chamber (1) and the second flow oil chamber (3) is sealed and locked, thereby fixing the flow slide valve (8) in this position.

9. The control method according to claim 8, characterized in that: In the volume ratio adjustment step, when the three-position four-way solenoid directional valve (13) is in the straight-through position, high-pressure oil enters the first volume ratio oil chamber (4) through the A port of the valve seat (14) and the A hole of the valve core (20), pushing the volume ratio piston (5) to the right, thereby driving the volume ratio slide valve (7) to the right to increase the volume ratio. Low-pressure oil is discharged from the second volume ratio oil chamber (6) through the B hole of the valve core (20) and the T port of the three-position four-way solenoid directional valve (13) back to the oil tank. When the three-position four-way solenoid directional valve (13) is in the cross position, high-pressure oil enters the first volume ratio oil chamber (4) through the B port of the valve seat (14) and the A hole of the valve core (20). (20) The B hole enters the second volume ratio oil chamber (6), pushing the volume ratio piston (5) to move to the left, thereby driving the volume ratio slide valve (7) to move to the left to reduce the volume ratio. Low-pressure oil is discharged from the first volume ratio oil chamber (4) through the A hole of the valve core (20) and the T port of the three-position four-way solenoid valve (13) back to the oil tank. When the volume ratio slide valve (7) moves to the target position, the three-position four-way solenoid valve (13) is switched to the cut-off position, so that the oil in the first volume ratio oil chamber (4) and the second volume ratio oil chamber (6) is sealed and locked, thereby fixing the volume ratio slide valve (7) in this position.

10. The control method according to claim 9, characterized in that: In the oil-free unloading step, after the compressor stops and there is no high-pressure oil supply in the high-pressure oil pipe (21), the valve core (20) is rotated to the unloading position, so that the second flat groove (C2) of the valve core (20) connects the first flow oil pipe (16) and the second flow oil pipe (15), the first flat groove (C1) connects the first volume ratio oil pipe (12) and the second volume ratio oil pipe (11), and the A hole and B hole of the valve core (20) are closed by the inner hole of the valve seat (14), so that the oil pressure on both sides of the flow piston (2) and the volume ratio piston (5) are connected to each other and the pressure is balanced; in the state of no pressure difference, the elastic force of the compression spring (9) pushes the flow slide valve (8) to the minimum flow position and pushes the volume ratio slide valve (7) to the minimum volume ratio position.

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