Screw compressor

Abstract

The utility model provides a screw compressor which comprises a compressor body, a compression cavity provided with a screw rotor is formed in the compressor body, the screw compressor further comprises an adjusting assembly, the adjusting assembly comprises a sliding valve and a piston fixedly connected with the sliding valve, and the piston is located in a piston cavity and divides the piston cavity into a first cavity and a second cavity. The second cavity is located on the side, away from the sliding valve, of the first cavity, the second cavity is provided with a pressurization opening and a pressure relief opening which communicate with the second cavity, and the pressure fluid regulation and control assembly can be controlled to increase pressure fluid into the second cavity or decrease pressure fluid from the second cavity so as to change the effective working length or the pressure ratio of the screw rotor. According to the screw compressor, the actual volume of the second cavity can be changed by controlling the amount of pressure fluid entering or flowing out of the second cavity, so that the position of the piston-slide valve is adjusted, the control logic of the screw compressor is simplified, the tedious degree of the control process is reduced, and adjustment is more timely and efficient.

Description

Technical Field

[0001] This utility model belongs to the field of air conditioning technology, specifically relating to a screw compressor. Background Technology

[0002] Screw compressors typically use the reciprocating motion of a slide valve and an oil piston to achieve capacity or pressure ratio regulation. Taking a single-unit two-stage screw compressor as an example, the difference between capacity and pressure ratio regulation lies in the structure and stroke of the slide valve. However, both capacity and pressure ratio regulation involve the compressor receiving control signals from the entire machine. Through the opening and closing of the solenoid valve, and under the influence of the suction and discharge pressure difference, lubricating oil enters and exits the oil cylinder, causing the slide valve and oil piston to reciprocate, thereby achieving the overall machine control requirements or objectives. Pressure ratio regulation, based on the actual suction and discharge pressures monitored by the entire machine, uses control logic to calculate the ratio of discharge pressure to suction pressure, controlling the opening and closing of the solenoid valve to adjust the movement of the slide valve, ensuring the external pressure ratio equals the internal pressure ratio, eliminating pressure losses caused by under-compression or over-compression, and achieving high-efficiency design. Capacity regulation, based on the actual capacity load monitored by the entire machine, uses control logic to determine whether the actual operating load has reached the target load, and then controls the opening and closing of the solenoid valve to adjust the movement of the slide valve, allowing the compressor to operate under load or unload, thus achieving overall machine load regulation.

[0003] Whether it's pressure ratio regulation or capacity regulation, there will be a process of repeated iterations of control logic, which in turn sends corresponding adjustment commands to the compressor. The control process is relatively complicated and has a time delay. Utility Model Content

[0004] Therefore, this utility model provides a screw compressor that can overcome the technical problems in related technologies where the adjustment of the pressure ratio or capacity of the screw compressor needs to be achieved through repeated iterations of control logic, resulting in a cumbersome control process and time delays.

[0005] To address the aforementioned problems, this utility model provides a screw compressor, including a compressor body with a compression chamber formed within it. A screw rotor is disposed within the compression chamber. The compressor body also includes an adjusting component for regulating the pressure ratio or capacity of the screw compressor. The adjusting component includes a slide valve and a piston fixedly connected to the slide valve. A piston chamber is also formed within the compressor body, with the piston positioned within the piston chamber and dividing it into a first chamber and a second chamber. The second chamber is located on the side of the first chamber furthest from the slide valve. The second chamber has a pressurization port and a depressurization port communicating with it. The compressor also includes a pressure fluid regulating component, which can be controlled to increase pressure fluid into the second chamber via the pressurization port or decrease pressure fluid from the second chamber via the depressurization port. This adjusts the volume of the second chamber, causing the slide valve to move and thus changing the effective working length or pressure ratio of the screw rotor.

[0006] In some embodiments, the pressure fluid control assembly includes a loading pipeline controllably connected to the outlet of a pressure fluid source and an unloading pipeline controllably connected to the return port of a pressure fluid unloading component. A first flow meter is connected in series on the loading pipeline, and a second flow meter is connected in series on the unloading pipeline.

[0007] In some embodiments, a first solenoid valve is connected in series on the loading pipeline, and a second solenoid valve is connected in series on the unloading pipeline.

[0008] In some embodiments, the pressure fluid control assembly includes a loading pipeline controllably connected to the outlet of a pressure fluid source and an unloading pipeline controllably connected to the return outlet of a pressure fluid unloading component, wherein the loading pipeline and the unloading pipeline share a third flow meter.

[0009] In some embodiments, the third flow meter is connected in series to the loading pipeline and divides the loading pipeline into a downstream loading section connected to the pressurization port and a controllable upstream loading section connected to the outlet. The unloading pipeline has an upstream unloading section connected to the upstream loading section and controllable, and a downstream unloading section connected between the third flow meter and the return port. A first solenoid valve is connected in series to the upstream loading section, and a second solenoid valve is connected in series to the downstream unloading section.

[0010] In some embodiments, the unloading upstream pipe section and the loading upstream pipe section are connected at a first position. A first check valve is connected in series on the loading upstream pipe section between the first position and the outlet. The first check valve is open from the outlet to the pressurization port and closed in the reverse direction. A second check valve is connected in series on the unloading upstream pipe section. The second check valve is open from the pressure relief port to the third flow meter and closed in the reverse direction.

[0011] In some embodiments, the piston and the slide valve are fixed together by a piston rod, and an elastic element is provided in the first cavity. The elastic element is sleeved on the piston rod and clamped between the piston's end face away from the second cavity and the inner wall of the first cavity.

[0012] The screw compressor provided by this utility model has the following beneficial effects:

[0013] By setting a pressurization port and a depressurization port on the second chamber, and controlling the pressure fluid regulation component, the entry and exit of the pressurized fluid in the second chamber can be controlled to change the position of the piston in the piston chamber. This, in turn, drives the slide valve to move and change the effective working length or pressure ratio of the screw rotor, thereby achieving load regulation or pressure ratio regulation of the screw compressor. In specific applications, the amount of pressurized fluid entering or leaving the second chamber can be controlled to change the actual volume of the second chamber, thereby achieving piston-slide valve position adjustment. This simplifies the control logic of the screw compressor, reduces the complexity of the control process, and makes the adjustment more timely and efficient. Attached Figure Description

[0014] To more clearly illustrate the embodiments of this utility model or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. The drawings in the following description are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0015] Figure 1 This is a schematic diagram (simplified diagram) of some components in the pressure fluid control assembly and adjustment assembly of the screw compressor in one embodiment of the present invention;

[0016] Figure 2 yes Figure 1 The diagram shows the state in which the first solenoid valve is in the connected state and the second solenoid valve is in the cut-off state. The diagram shows that the pressurized fluid flows into the second chamber through the pressurization port to increase the capacity of the pressurized fluid in the second chamber, thereby driving the piston and slide valve to move to the left. In the diagram, F1 is the axial (piston rod axial) resultant force of the pressurized fluid in the second chamber and the pressure of the compressed fluid (if there is an elastic element, it also includes the elastic force of the elastic element) on the left end face of the slide valve.

[0017] Figure 3 yes Figure 1The diagram shows the state in which the first solenoid valve is cut off and the second solenoid valve is connected. The diagram shows that the pressure fluid flows out of the second chamber through the pressure relief port to reduce the volume of the pressure fluid in the second chamber, thereby driving the piston and slide valve to move to the right. In the diagram, F2 is the axial resultant force of the pressure fluid in the second chamber and the pressure of the compressed fluid (if there is an elastic element, it also includes the elastic force of the elastic element) on the left end face of the slide valve.

[0018] Figure 4 This is a schematic diagram (simplified diagram) of some components in the pressure fluid control assembly and adjustment assembly of the screw compressor in another embodiment of the present invention;

[0019] Figure 5 yes Figure 4 The diagram shows the state in which the first solenoid valve is in the connected state and the second solenoid valve is in the cut-off state. The diagram shows that the pressurized fluid flows into the second chamber through the pressurization port to increase the capacity of the pressurized fluid in the second chamber, thereby driving the piston and slide valve to move to the left. In the diagram, F1 is the axial (piston rod axial) resultant force of the pressurized fluid in the second chamber and the pressure of the compressed fluid (if there is an elastic element, it also includes the elastic force of the elastic element) on the left end face of the slide valve.

[0020] Figure 6 yes Figure 4 The diagram shows the state in which the first solenoid valve is cut off and the second solenoid valve is connected. The diagram shows that the pressure fluid flows out of the second chamber through the pressure relief port to reduce the volume of the pressure fluid in the second chamber, thereby driving the piston and slide valve to move to the right. In the diagram, F2 is the axial resultant force of the pressure fluid in the second chamber and the pressure of the compressed fluid (if there is an elastic element, it also includes the elastic force of the elastic element) on the left end face of the slide valve.

[0021] The attached figures are labeled as follows:

[0022] 1. Piston; 11. Piston rod; 2. Piston chamber; 21. First chamber; 22. Second chamber; 221. Pressurization port; 222. Depressurization port; 31. Loading pipeline; 311. First flow meter; 312. First solenoid valve; 32. Unloading pipeline; 321. Second flow meter; 322. Second solenoid valve; 33. Third flow meter; 341. First check valve; 342. Second check valve. Detailed Implementation

[0023] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present utility model or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of the present utility model without creative effort are within the scope of protection of the present utility model.

[0024] In the description of this utility model, it should be understood that the directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description. Unless otherwise stated, these directional terms 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, and therefore should not be construed as a limitation on the scope of protection of this utility model. The directional terms "inner" and "outer" refer to the inner and outer contours of each component itself.

[0025] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90° or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0026] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be construed as limiting the scope of protection of this utility model.

[0027] See Figure 1 and Figure 6As shown, according to an embodiment of the present invention, a screw compressor is provided, including a compressor body (not shown in the figure, not indexed). A compression chamber (not shown in the figure, not indexed) is formed within the compressor body. A screw rotor (not shown in the figure, not indexed, which can be a single screw or a twin screw) is provided within the compression chamber. The rotor is driven to rotate by a motor to achieve the purpose of compressing fluid. The screw compressor also includes an adjusting component (not shown in the figure, not indexed) for adjusting the pressure ratio or capacity of the screw compressor. The adjusting component includes a slide valve (not shown in the figure, not indexed) and a piston 1 fixedly connected to the slide valve. Thus, the movement of the slide valve and the piston 1 is synchronized. It is understood that the slide valve can be part of the wall of the compression chamber. A piston chamber 2 is also formed within the compressor body, and the piston 1 is located within the piston chamber 2. The piston chamber 2 is divided into two independent chambers, a first chamber 21 and a second chamber 22. The second chamber 22 is located on the side of the first chamber 21 away from the slide valve. The second chamber 22 is configured with a pressurization port 221 and a depressurization port 222 communicating with it. It also includes a pressure fluid control component (not shown in the figure, not indexed). The pressure fluid control component can be controlled to increase the pressure fluid into the second chamber 22 via the pressurization port 221 (i.e., the pressurization port 221 is for the inflow of pressure fluid) or decrease the pressure fluid from the second chamber 22 via the depressurization port 222 (i.e., the depressurization port 222 is for the outflow of pressure fluid). By adjusting the volume of the second chamber 22, the slide valve is moved, thereby changing the effective working length of the screw rotor (i.e., the length of the part where the slide valve and the screw rotor mate) or the pressure ratio of the screw rotor. The aforementioned pressure fluid can be, for example, lubricating oil. It is understandable that compressors with load regulation (i.e., capacity regulation) specifically change the effective working length of the screw rotor, while compressors with pressure ratio regulation specifically change the pressure ratio of the screw rotor.

[0028] In this technical solution, by setting a pressurization port 221 and a depressurization port 222 on the second chamber 22, the pressure fluid inlet and outlet in the second chamber 22 can be controlled by controlling the pressure fluid regulation component to change the position of piston 1 in piston chamber 2, thereby driving the slide valve to move and change the effective working length or pressure ratio of the screw rotor, thus realizing the load regulation or pressure ratio regulation of the screw compressor. In specific applications, the actual volume of the second chamber 22 can be changed by controlling the amount of pressure fluid entering or leaving the second chamber 22, thereby realizing the position adjustment of piston-slide valve. This helps to simplify the control logic of the screw compressor, reduce the complexity of the control process, and make the adjustment more timely and efficient.

[0029] See details Figures 1 to 3As shown, in a specific embodiment, the pressure fluid control component includes a loading pipeline 31 that is controllably connected to the outlet (e.g., oil supply port) of a pressure fluid source (e.g., a hydraulic oil pump, not shown in the figure) and an unloading pipeline 32 that is controllably connected to the return port of a pressure fluid unloading component (the aforementioned pressure fluid unloading component can be the oil phase of a hydraulic oil pump, in which case the corresponding return port is also the oil return port). A first flow meter 311 is connected in series on the loading pipeline 31, and a second flow meter 321 is connected in series on the unloading pipeline 32.

[0030] In this technical solution, by connecting a first flow meter 311 and a second flow meter 321 in series on the loading pipeline 31 and the unloading pipeline 32 respectively, the pressure fluid entering and flowing out of the second chamber 22 can be recorded in real time. Then, by subtracting the sum of the flow rates of the pressure fluid recorded by the two flow meters, the accurate volume of the pressure fluid in the second chamber 22 can be obtained. Then, the accurate position of the piston 1, that is, the relative position of the slide valve and the screw rotor, can be obtained by using the piston diameter or the piston chamber diameter. In this way, the pressure ratio or load state of the screw compressor can be efficiently and timely adjusted without having to iterate the pressure ratio or flow rate multiple times and then convert it into digital control of the lubricating oil flow rate in the compressor cylinder as in the prior art, making the control simpler.

[0031] In some embodiments, a first solenoid valve 312 is connected in series on the loading pipeline 31, and a second solenoid valve 322 is connected in series on the unloading pipeline 32. The specific positions of the first solenoid valve 312 and the second solenoid valve 322 are not particularly limited, but are preferably close to the second cavity 22, for example, they can be assembled on the outer wall surface of the second cavity 22.

[0032] In this technical solution, by configuring a first solenoid valve 312 and a second solenoid valve 322 on the loading pipeline 31 and the unloading pipeline 32 respectively, the component integration and structural compactness of the device can be improved.

[0033] See details Figures 4 to 6 As shown, in another specific embodiment, the pressure fluid control component includes a loading pipe 31 controllably connected to the outlet of the pressure fluid source and an unloading pipe 32 controllably connected to the return port of the pressure fluid unloading component. The loading pipe 31 and the unloading pipe 32 share a third flow meter 33. It is understood that while the third flow meter 33 records the flow rate, the corresponding control system also needs to independently record the flow rate of the third flow meter 33 corresponding to the loading (inflow) and unloading (return) respectively, so as to obtain the accurate volume of the pressure fluid in the second cavity 22 by subtracting the sum of the loading flow rate from the sum of the unloading flow rate.

[0034] In this technical solution, the loading pipeline 31 and the unloading pipeline 32 share a third flow meter 33, which can reduce the number of flow meters used, thereby reducing manufacturing costs and the number of equipment failure points.

[0035] In some embodiments, the third flow meter 33 is connected in series to the loading pipeline 31 and divides the loading pipeline 31 into a downstream loading pipeline section (not labeled in the figure) connected to the pressurization port 221 and a upstream loading pipeline section (not labeled in the figure) connected to the outlet and capable of controllable switching. The unloading pipeline 32 has an upstream unloading pipeline section (not labeled in the figure) connected to the upstream loading pipeline section and capable of controllable switching, and a downstream unloading pipeline section (not labeled in the figure) connected between the third flow meter 33 and the return port. A first solenoid valve 312 is connected in series on the upstream loading pipeline section, and a second solenoid valve 322 is connected in series on the downstream unloading pipeline section.

[0036] In this technical solution, the first solenoid valve 312 is set in the upstream pipe section of the loading pipeline, and the second solenoid valve 322 is set in the downstream pipe section of the unloading pipeline. Under the premise that the loading pipeline 31 and the unloading pipeline 32 share the third flow meter 33, independent control of the inflow and outflow of the second chamber 22 is guaranteed.

[0037] In some embodiments, the unloading upstream pipe section and the loading upstream pipe section are connected at a first position (not indicated in the figure). A first one-way valve 341 is connected in series on the loading upstream pipe section between the first position and the outlet. The first one-way valve 341 is open from the outlet to the pressurization port 221 and closed in the reverse direction. A second one-way valve 342 is connected in series on the unloading upstream pipe section. The second one-way valve 342 is open from the pressure relief port 222 to the third flow meter 33 and closed in the reverse direction.

[0038] In this technical solution, by connecting the first check valve 341 and the second check valve 342 in series on the loading upstream pipe section and the unloading upstream pipe section respectively, the pressure fluid control component only needs to control the opening and closing of the aforementioned first solenoid valve 312 and the second solenoid valve 322 to achieve inflow and return control under the premise of sharing the third flow meter 33. This simplifies the component layout and pipeline design, making control simpler.

[0039] In some embodiments, the piston 1 and the slide valve are fixed together by a piston rod 11. An elastic element (not shown in the figure) is also provided in the first cavity 21. The elastic element is sleeved on the piston rod 11 and is clamped between the end face of the piston 1 facing away from the second cavity 22 and the inner wall surface of the first cavity 21. The aforementioned elastic element can be a helical spring.

[0040] In this technical solution, by fitting an elastic element on the piston rod 11, force can be applied to the piston 1 when the equipment stops abnormally, so that the piston 1 can return to its initial position, that is, the state in which there is no pressure flow in the second chamber 22 (at this time, the volume of the second chamber 22 is 0).

[0041] According to an embodiment of the present invention, a control method for a screw compressor as described above is also provided, comprising the following steps:

[0042] The target operating condition of the screw compressor is obtained, and the target pressure fluid volume V0 of the second chamber 22 corresponding to the target operating condition is obtained according to the target operating condition. It is understood that different target operating conditions correspond to different aforementioned target pressure fluid volumes V0, and the specific correspondence can be clearly determined by design calculation.

[0043] The real-time pressure fluid volume V of the second chamber 22 is obtained. Specifically, the real-time pressure fluid volume V is the difference between the sum of the inflow flow rate detected by the first flow meter 311 and the sum of the outflow flow rate detected by the second flow meter 321 in each instance, or the real-time pressure fluid volume V is the difference between the sum of the inflow flow rate detected by the third flow meter 33 in each instance and the sum of the outflow flow rate detected in each instance.

[0044] The pressure fluid control component determines whether to add pressure fluid into the second cavity 22 (i.e., control the pressure fluid to flow into the second cavity 22) or reduce pressure fluid from the second cavity 22 (i.e. control the pressure fluid to flow out of the second cavity 22) by judging the relationship between the real-time pressure fluid volume V and the target pressure fluid volume V0. In this process, the pressure fluid flowing through it is detected in real time by the first flow meter 311, the second flow meter 321 or the third flow meter 33, and the inflow or outflow is stopped after the pressure fluid inflow or outflow is detected to reach the target flow rate.

[0045] Specifically, determining the relationship between the real-time pressure fluid volume V and the target pressure fluid volume V0 to control whether the pressure fluid regulation component adds pressure fluid to or reduces pressure fluid from the second cavity 22 specifically includes:

[0046] When V = V0, the pressure fluid control component is controlled to neither increase nor decrease the pressure fluid in the second chamber 22, so that the position of the slide valve remains unchanged; or...

[0047] When V > V0, the pressure fluid control component reduces the pressure fluid from the second chamber 22, causing the slide valve to slide closer to the second chamber 22 to reduce the effective working length or pressure ratio of the screw rotor until V = V0, at which point the reduction of pressure fluid stops; or...

[0048] When V < V0, the pressure fluid control component is controlled to increase the pressure fluid into the second chamber 22, so that the slide valve slides away from the second chamber 22 to increase the effective working length or pressure ratio of the screw rotor, until V = V0 and the increase of the pressure fluid stops.

[0049] In some embodiments, when the screw compressor includes a first flow meter 311, a second flow meter 321, a first solenoid valve 312, and a second solenoid valve 322,

[0050] When V = V0, both the first solenoid valve 312 and the second solenoid valve 322 are controlled to be in the off state; when V > V0, the second solenoid valve 322 is controlled to be turned on and the first solenoid valve 312 is turned off, and when the real-time flow detected by the second flow meter 321 is V - V0, the second solenoid valve 322 is controlled to be turned off. At this time, Figure 1 The orientation shown is for reference only. The piston 1 will slide from left to right under the influence of the pressure difference on both sides (e.g., Figure 3 and Figure 6 (As shown); when V < V0, the first solenoid valve 312 is turned on and the second solenoid valve 322 is turned off. When the real-time flow rate detected by the first flow meter 311 is V0-V, the first solenoid valve 312 is turned off. At this time, with... Figure 1 The orientation shown is for reference only. The piston 1 will slide from right to left under the action of the pressure difference on both sides (e.g., Figure 2 and Figure 5 (as shown); or,

[0051] When the screw compressor includes a third flow meter 33, a first solenoid valve 312, a second solenoid valve 322, a first check valve 341, and a second check valve 342, when V = V0, both the first solenoid valve 312 and the second solenoid valve 322 are controlled to be in the cut-off state; when V > V0, the second solenoid valve 322 is controlled to be turned on and the first solenoid valve 312 is turned off, and when the real-time flow detected by the third flow meter 33 is V-V0, the second solenoid valve 322 is controlled to be turned off; when V < V0, the first solenoid valve 312 is controlled to be turned on and the second solenoid valve 322 is turned off, and when the real-time flow detected by the third flow meter 33 is V0-V, the first solenoid valve 312 is controlled to be turned off.

[0052] For example, if it is a pressure ratio adjustment, the current pressure ratio is 3.0 (that is, the current operating condition is a pressure ratio of 3.0), and the corresponding oil volume in the cylinder (that is, the volume in the aforementioned second chamber 22) is V = 1.5L (this volume is also the current pressure fluid volume V0 when the pressure ratio is 3.0). Now, if we want to adjust the pressure ratio to 2.4, the corresponding target pressure fluid volume is V0 = 1.8L. At this time, V0 > V, that is, we need to add another 0.3L of oil to the cylinder. Drive the piston 1 to move away from the second chamber 22 in a direction (which can be defined as leftward movement) to the specified distance. During this process, the pressure fluid flowing into the second chamber 22 is detected in real time by the first flow meter 311 until the 0.3L of lubricating oil stops flowing in.

[0053] It should be noted that, during the initial design phase of the compressor, whether for pressure ratio or capacity adjustment, the volume of lubricating oil (i.e., the aforementioned pressurized fluid) that the corresponding cylinder (i.e., the second chamber 22 mentioned above, hereinafter the same) can hold when the slide valve moves has already been calculated and formed into a database, which is incorporated into the overall machine control logic. For example, at a pressure ratio of 3.0, the volume V of lubricating oil that the cylinder can hold is... 3.0 (Specific values ​​should be determined reasonably based on the actual piston chamber diameter, etc.); at 75% load, the volume V of lubricating oil that the cylinder can hold. 75％ In this way, different types of databases can be formed. During the operation of the whole machine, known data in the control logic can be called up at any time for comparison (that is, a one-to-one correspondence is formed between the target operating condition and the target pressure fluid volume V0).

[0054] by Figures 1 to 3 Taking the illustrated embodiment as an example, in a certain operating state of the whole machine, the volume data V11, V12, V13, ..., V1n and V21, V22, V23, ..., V2n of the two flow meters Q1 (corresponding to the first flow meter) and Q2 (corresponding to the second flow meter) on the compressor loading and unloading oil circuit can be obtained from the whole machine control logic. The cumulative volume of the two flow meters V1 = V11 + V12 + V13 + ... + V1n and V2 = V21 + V22 + V23 + ... + V2n can be calculated. Then, the volume of lubricating oil in the cylinder in the current state V = V1 - V2 can be calculated. The aforementioned V1 is the sum of V11, V12, V13, ..., V1n, and V2 is the sum of V21, V22, V23, ..., V2n.

[0055] If a target operating condition needs to be reached, the corresponding volume of lubricating oil in the cylinder is V0. The overall control logic will calculate the difference ΔV between V0 and V, and control the opening or closing of the solenoid valves (i.e., the aforementioned first and second solenoid valves, hereinafter the same) based on the difference ΔV to supply or discharge oil, thereby achieving the specified volume V0. If V < V0, the compressor will receive the overall control command, open the loading solenoid valve (i.e., the aforementioned first solenoid valve 312, hereinafter the same), and close the unloading solenoid valve (i.e., the aforementioned second solenoid valve 322, hereinafter the same). Under the action of the pressure difference, the slide valve and oil piston move as a whole to the left of the diagram. The moving distance is controlled by the flow meter Q1. When the specified flow rate ΔV is reached, the loading solenoid valve is closed, and operation continues. Similarly, if V > V0, the compressor will receive the overall control command, open the unloading solenoid valve, and close the loading solenoid valve. Under the action of the pressure difference, the slide valve and oil piston move as a whole to the right of the diagram. The moving distance is controlled by the flow meter Q2. When the specified flow rate ΔV is reached, the unloading solenoid valve is closed, and operation continues.

[0056] In this technical solution, by connecting a first flow meter 311 and a second flow meter 321 in series on the loading pipeline 31 and the unloading pipeline 32 respectively, the pressure fluid entering and flowing out of the second chamber 22 can be recorded in real time. Then, by subtracting the sum of the flow rates of the pressure fluid recorded by the two flow meters, the accurate volume of the pressure fluid in the second chamber 22 can be obtained. Then, the accurate position of the piston 1, that is, the relative position of the slide valve and the screw rotor, can be obtained by using the piston diameter or the piston chamber diameter. In this way, the pressure ratio or load state of the screw compressor can be efficiently and timely adjusted. Unlike the prior art, there is no need to iterate the pressure ratio or flow rate multiple times and then convert it into digital control of the lubricating oil flow in the compressor cylinder. The control is simpler and can effectively prevent the energy efficiency and load fluctuation problems of the compressor during the slide valve adjustment process caused by control delay.

[0057] The first flow meter 311, the second flow meter 321 and the third flow meter 33 of this utility model can all be conventional commercially available parts. It is preferred to use a flow meter equipped with a functional module that can calculate the flow rate and convert it into volume in real time. Of course, the aforementioned conversion can also be achieved by using the relevant functional module in the control module of the compressor.

[0058] It will be readily understood by those skilled in the art that, without conflict, the advantageous technical features of the above-mentioned methods can be freely combined and superimposed.

[0059] The above description is merely a preferred embodiment of this utility model and is not intended to limit the utility model. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this utility model should be included within the protection scope of this utility model. The above description is only a preferred embodiment of this utility model. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of this utility model, and these improvements and modifications should also be considered within the protection scope of this utility model.

Claims

1. A screw compressor, characterized in that, The compressor includes a compressor body, a compression chamber formed within the compressor body, a screw rotor disposed within the compression chamber, and an adjusting assembly for adjusting the pressure ratio or capacity of the screw compressor. The adjusting assembly includes a slide valve and a piston (1) fixedly connected to the slide valve. A piston chamber (2) is also formed within the compressor body, the piston (1) being located within the piston chamber (2) and dividing the piston chamber (2) into two independent chambers: a first chamber (21) and a second chamber (22). The second chamber (22) is located within the first chamber (21). On the side away from the slide valve, the second chamber (22) is constructed with a pressurizing port (221) and a depressurizing port (222) communicating with it, and also includes a pressure fluid control component. The pressure fluid control component can be controlled to increase the pressure fluid into the second chamber (22) via the pressurizing port (221) or decrease the pressure fluid from the second chamber (22) via the depressurizing port (222) so as to drive the slide valve to move by adjusting the volume of the second chamber (22), thereby changing the effective working length of the screw rotor or the pressure ratio of the screw rotor.

2. The screw compressor according to claim 1, characterized in that, The pressure fluid control component includes a loading pipeline (31) controllably connected to the outlet of the pressure fluid source and an unloading pipeline (32) controllably connected to the return port of the pressure fluid unloading component. A first flow meter (311) is connected in series on the loading pipeline (31), and a second flow meter (321) is connected in series on the unloading pipeline (32).

3. The screw compressor according to claim 2, characterized in that, A first solenoid valve (312) is connected in series on the loading pipeline (31), and a second solenoid valve (322) is connected in series on the unloading pipeline (32).

4. The screw compressor according to claim 1, characterized in that, The pressure fluid control component includes a loading pipeline (31) that is controllably connected to the outlet of the pressure fluid source and an unloading pipeline (32) that is controllably connected to the return port of the pressure fluid unloading component. The loading pipeline (31) and the unloading pipeline (32) share a third flow meter (33).

5. The screw compressor according to claim 4, characterized in that, The third flow meter (33) is connected in series to the loading pipeline (31) and divides the loading pipeline (31) into a downstream loading pipeline connected to the pressurization port (221) and a upstream loading pipeline connected to the outlet and capable of being controlled to open and close. The unloading pipeline (32) has an upstream unloading pipeline connected to the upstream loading pipeline and capable of being controlled to open and close, and an downstream unloading pipeline connected between the third flow meter (33) and the return port. A first solenoid valve (312) is connected in series on the upstream loading pipeline, and a second solenoid valve (322) is connected in series on the downstream unloading pipeline.

6. The screw compressor according to claim 5, characterized in that, The unloading upstream pipe section and the loading upstream pipe section are connected at a first position. A first one-way valve (341) is connected in series on the loading upstream pipe section between the first position and the outlet. The first one-way valve (341) is open from the outlet to the pressurization port (221) and closed in the reverse direction. A second one-way valve (342) is connected in series on the unloading upstream pipe section. The second one-way valve (342) is open from the pressure relief port (222) to the third flow meter (33) and closed in the reverse direction.

7. The screw compressor according to any one of claims 1 to 6, characterized in that, The piston (1) and the slide valve are fixed together by the piston rod (11). An elastic element is also provided in the first cavity (21). The elastic element is sleeved on the piston rod (11) and is clamped between the end face of the piston (1) away from the second cavity (22) and the inner wall surface of the first cavity (21).

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