Screw compressor and refrigeration cycle device

Abstract

To provide a screw compressor capable of grasping an operating capacity accurately.SOLUTION: A screw compressor 100 has an operating capacity controlled within a range of an operating capacity including 0% to 20%, and comprises a compressor body 10. The compressor body 10 comprises: a casing 1; a screw rotor 2 that is rotationally driven in the casing 1; a bypass flow path 3 that communicates with a suction side of a compression chamber 12 from a compression chamber 11 formed between the casing 1 and the screw rotor 2; a slide valve 4 that is movable to adjust the opening of the bypass flow path 3; and a detection mechanism 5 that detects that the slide valve 4 has passed a predetermined position when the slide valve 4 moves within a movable range of the slide valve 4.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a screw compressor and a refrigeration cycle device.

Background Art

[0002] As a technique for detecting the operating capacity of a screw compressor, the technique described in Patent Document 1 is known. Patent Document 1 describes that "the detector 26 of the capacity detection device 25 including the controller 28, the detector 26, and the display 27 is attached to the cylinder wall 10, and the detector 26 and the controller 28 detect the position of the piston 9, that is, the position of the slide valve 3, to obtain the operating capacity of the compressor and output it to the display 27."

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the technique described in Patent Document 1, ultrasonic waves are transmitted to the piston 9 sliding inside the cylinder chamber 19, and the reflected waves from the piston 9 are received (paragraph 0011). The ultrasonic waves are transmitted at determined time intervals (paragraph 0018). From these, the position of the piston can be detected, and the operating capacity of the compressor is determined (paragraph 0011). However, as will be described in detail later, as a result of the inventor's study, it has been found that the operating capacity can be accurately grasped without always grasping the position of the piston 9 over the entire sliding range inside the cylinder chamber 19. The problem to be solved by the present disclosure is to provide a screw compressor and a refrigeration cycle device capable of accurately grasping the operating capacity.

Means for Solving the Problems

[0005] The screw compressor of the present disclosure isA screw compressor used in a range of operating capacities including 0% to 20% of the operating capacity, A compressor body and an arithmetic unit are provided. The compressor body includes a casing, a screw rotor that is rotationally driven within the casing, a bypass flow path that communicates from a compression chamber formed between the casing and the screw rotor to an intake side of the compression chamber, a slide valve that is movable so as to adjust an opening degree of the bypass flow path, and a detection mechanism that detects that the slide valve has passed through a predetermined position when the slide valve moves within a movable range of the slide valve. The arithmetic unit has a correlation between a current value flowing through the compressor body and an operating capacity of the compressor body. The correlation includes a first correlation used when the slide valve exists on one side with respect to the predetermined position within a movable range of the slide valve, and a second correlation used when the slide valve exists on the other side. determine which of the first correlation or the second correlation to use based on the position of the slide valve detected by the detection mechanism, and determine the operating capacity from the current value flowing through the compressor body and the determined first correlation or second correlation Other solutions will be described later in the mode for carrying out the invention.

Effect of the Invention

[0006] According to the present disclosure, it is possible to provide a screw compressor and a refrigeration cycle apparatus capable of accurately grasping an operating capacity.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Embodiments for Carrying Out the Invention

[0008] Hereinafter, embodiments (referred to as embodiments) for carrying out the present disclosure will be described with reference to the drawings. In the description of the following one embodiment, descriptions of other embodiments applicable to one embodiment will be made as appropriate. The present disclosure is not limited to the following one embodiment, and different embodiments can be combined with each other or arbitrarily modified within a range that does not significantly impair the effects of the present disclosure. Also, the same members are denoted by the same reference numerals, and overlapping descriptions are omitted. Furthermore, those having the same function are given the same name. The illustrated content is merely schematic, and for the convenience of illustration, it may be changed from the actual configuration within a range that does not significantly impair the effects of the present disclosure, or some members may be omitted or deformed between the drawings. Also, in the same embodiment, it is not always necessary to include all the configurations.

[0009] FIG. 1 is a diagram for explaining the structure of the screw compressor 100, and is a diagram showing the position of the slide valve 4 when compressing gas in a state where the operating capacity is approximately 100%. The screw compressor 100 includes a compressor body 10 shown in FIG. 1 and an arithmetic unit 20 shown in FIG. 4 described later. The white arrow shown covering the screw rotor 2 indicates the flow of the refrigerant of the gas G sucked from the suction port (not shown) of the compressor body 10.

[0010] The compressor body 10 of the present disclosure is a variable-capacity screw compressor capable of changing the operating capacity. In the compressor body 10, a part of the sucked gas G (for example, refrigerant, air, etc.) is returned to the suction side (that is, bypassed). The amount of the gas G returned to the suction side is changed by controlling the position of the slide valve 4.

[0011] The compressor body 10 includes a casing 1, a screw rotor 2, a bypass passage 3, a slide valve 4, and a detection mechanism 5.

[0012] The casing 1 includes an internal compression chamber 11 (chamber) that compresses the gas G sucked from an inlet (not shown) formed in the compressor body 10. The screw rotor 2 is rotationally driven within the casing 1. The screw rotor 2 is disposed in a chamber 12 formed inside the casing 1. A motor (not shown) is connected to the screw rotor 2, and the screw rotor 2 rotates by the drive of the motor. Only one screw rotor 2 is shown in FIG. 1, but for example, a pair of screw rotors 2 is provided. Then, the gas G is compressed in the compression chamber 11 formed between the meshing of the pair of screw rotors 2 and the casing 1.

[0013] The bypass passage 3 is a passage (pathway) that communicates from the compression chamber 11 (for example, a position during the compression of the gas G in the compression chamber 11) formed between the casing 1 and the screw rotor 2 to the suction side of the compression chamber 11. The gas G is sucked from an inlet (not shown) of the compressor body 10, and a part of the sucked gas G, which is the gas GB, passes through the bypass passage 3 and is returned to the suction side of the compression chamber 11. The remaining part of the gas G, which is the gas GP, is compressed in the compression chamber 11 and is discharged from the compressor body 10 through an outlet (not shown) after compression.

[0014] The slide valve 4 is movable to adjust the opening degree of the bypass passage 3. The slide valve 4 moves in the coaxial direction within a predetermined movement range from one side to the other side or from the other side to one side. The opening degree (cross-sectional area) of the bypass passage 3 is controlled by the movement of the slide valve 4, for example, in the horizontal direction. In the illustrated example, the opening degree of the bypass passage 3 can be reduced by moving the slide valve 4 horizontally away from the discharge port (not shown) and further to close the bypass passage 3. By reducing the opening degree of the bypass passage 3, the amount of the bypassed gas GB relatively decreases while the amount of the gas GP discharged after compression relatively increases. As a result, the operating capacity relatively increases. Also, by increasing the opening degree of the bypass passage 3, the amount of the bypassed gas GB relatively increases while the amount of the gas GP discharged after compression relatively decreases. As a result, the operating capacity relatively decreases.

[0015] The slide valve 4 includes a substantially cylindrical valve body 41, a rod 42, and, for example, a disc-shaped piston 43. The valve body 41 is in contact with the gas G compressed by the compressor body 10 and, for example, constitutes the wall surface of the bypass passage 3. In the moving direction of the slide valve 4, one side surface of the valve body 41 constitutes the wall surface of the bypass passage 3, and the other side surface constitutes the wall surface of the passage through which the compressed gas GP flows.

[0016] The piston 43 is accommodated in a chamber 13 (described later) different from the chamber 12 in which the valve body 41 is connected to and accommodated in the valve body 41. The valve body 41 and the piston 43 are connected by the rod 42. Therefore, by moving the piston 43 disposed outside the chamber 12, the valve body 41 can be moved horizontally inside the chamber 12 via the rod 42.

[0017] The piston 43 is housed in a chamber 13 formed inside the casing 1. The chamber 13 is formed independently of the chamber 12. The chamber 12 and the chamber 13 communicate with each other via a communication passage (not shown) through which the rod 42 passes. However, no gas or liquid is exchanged between the chamber 12 and the chamber 13. The end portions (e.g., upper and lower end portions) in a direction perpendicular to the moving direction (sliding direction) of the piston 43 have a shape (width, size) capable of closing the opening 521 facing the chamber 12 in the communication passage 52 (described later).

[0018] The position of the slide valve 4 is controlled by hydraulic pressure. The piston 43 connected to the valve body 41 has one surface 431 and the other surface 432. The piston 43 moves in the direction of the surface 432 due to the pressure of the oil FO existing on the surface 431 side. In the chamber 13, a chamber 131 is formed on the surface 431 side, and a chamber 132 is formed on the surface 432 side. That is, the chamber 13 includes the chambers 131 and 132. The chamber 131 is connected to a supply source and a discharge destination (both not shown) of the oil FO, and as described above, the oil FO exists in the chamber 131. The chamber 132 is connected to, for example, the suction side of the compression chamber 11 through the opening 25, and a gas FG exists in the chamber 132. The gas FG is, for example, a refrigerant existing on the suction side of the compression chamber 11. Therefore, the gas FG is a gas (e.g., refrigerant) at a relatively lower pressure than the compressed gas GP (e.g., refrigerant).

[0019] In the valve body 41, on the side (one side) facing the bypass passage 3, there is a gas GB that is not compressed (bypassed), so it is at a relatively low pressure. However, when the bypass passage 3 is closed, no gas GB exists on the side facing the bypass passage 3. On the other hand, in the valve body 41, on the side opposite to the bypass passage 3, that is, on the side (the other side) facing the compression chamber 11, there is a compressed gas GP. Therefore, a force is applied to the valve body 41 in the direction of closing the bypass passage 3 (from right to left in the drawing plane) by the pressure of the relatively high-pressure gas GP existing in the compression chamber 11.

[0020] FIG. 2 is a diagram for explaining the structure of the screw compressor 100 (compressor main body 10), and shows the position of the slide valve 4 when compressing gas in a state where the operating capacity is approximately 50%. When the operating capacity is changed from the state where the operating capacity shown in FIG. 1 is approximately 100% to the state where the operating capacity shown in FIG. 2 is approximately 50%, the slide valve 4 moves as indicated by the dashed arrow.

[0021] When the valves 21 and 23 are closed and the valve 22 is opened, relatively high-pressure oil FO flows into the chamber 131 through the flow path 24 as indicated by the solid arrow. The oil FO is supplied from a supply source (not shown) as described above. Due to the supply, the piston 43 is pushed from the side of the surface 431 toward the side of the surface 432 against the force applied to the valve body 41 by the pressure of the oil FO. As a result, the valve body 41 connected to the piston 43 moves to increase the opening degree of the bypass flow path 3 as indicated by the dashed arrow in FIG. 2. At this time, as the piston 43 moves, the gas FG existing in the chamber 132 is discharged from the chamber 132 through the opening 25 as indicated by the hollow arrow.

[0022] When returning from the state shown in FIG. 2 to the state shown in FIG. 1, the reverse operation of the above operation is performed. First, when the valves 22 and 23 are closed and the valve 21 is opened, the oil FO in the chamber 131 can be discharged to the discharge destination of the oil FO (not shown) through the flow path 24. As described above, a force in the direction of closing the bypass flow path 3 is applied to the valve body 41 by the compressed gas GP. Therefore, the valve body 41 moves in the direction of closing the bypass flow path 3 as indicated by the dashed arrow in FIG. 1 while pushing out the oil FO in the chamber 131 toward the discharge destination. At this time, as the piston 43 moves, the gas FG flows into the chamber 132 through the opening 25.

[0023] Returning to FIG. 1, the detection mechanism 5 detects that the slide valve 4 has passed through a predetermined position when the slide valve 4 moves within its movable range. That is, within the movable range of the slide valve 4, it is detected that the slide valve 4 is present at the predetermined position. In the example of the present disclosure, the detection mechanism 5 detects that the slide valve 4 has passed through the predetermined position by detecting the position of the piston 43 that moves together with the valve body 41 when the valve body 41 moves within a predetermined movable range. As described above, the valve body 41 and the piston 43 are integrally configured together with the rod 42. Therefore, when the slide valve 4 moves, by detecting that the piston 43 has passed through (is present at) the predetermined position, it is possible to indirectly detect that the slide valve 4 (particularly the valve body 41) has passed through the predetermined position.

[0024] Note that the valve body 41 and the piston 43 move integrally. Therefore, the slide valve 4 passing through (being present at) the predetermined position is synonymous with the valve body 41 passing through the predetermined position and the piston 43 passing through the predetermined position.

[0025] In the example of the present disclosure, the detection mechanism 5 is a pressure detection mechanism 51 installed in the communication passage 52 (for example, installed outside the chamber 13). The communication passage 52 communicates the inside and outside of the chamber 13 that houses the piston 43. When the slide valve 4 (the valve body 41 and the piston 43) moves, the pressure in the chamber 131 is different from the pressure in the chamber 132. For example, when the piston 43 is moving toward the side of the surface 432, the pressure in the chamber 131 is higher than the pressure in the chamber 132. Therefore, the pressure in the chamber 13 changes with the piston 43 as the boundary. Thus, by detecting the pressure change in the chamber 13 by the pressure detection mechanism 51 connected to the inside of the chamber 13, it is possible to detect that the piston 43 has reached the portion of the communication passage 52, that is, is present at the predetermined position.

[0026] The predetermined position detected during the movement of the slide valve 4 (particularly the valve body 41) is a position where the tendency of the correlation between the current value flowing through the compressor body 10 (operating current value) and the operating capacity of the compressor body 10 (hereinafter, appropriately referred to as the correlation of the present disclosure) changes. This point will be described with reference to FIG. 3.

[0027] FIG. 3 is a graph for explaining the relationship between torque, operating capacity, motor efficiency, and current value. The horizontal axis represents the torque of the compressor body 10. The torque of the compressor body 10 is correlated with the operating capacity of the compressor body 10, and for example, the torque and the operating capacity can often be regarded as the same. Therefore, the horizontal axis can be considered as the torque and the operating capacity of the compressor body 10. The torque on the horizontal axis is shown as a percentage (%) with the maximum torque (rated value) being 100%, and the operating capacity on the horizontal axis is shown as a percentage (%) with the maximum operating capacity (maximum capacity) being 100%. The left vertical axis is the motor efficiency (%), and the right vertical axis is the current value flowing through the compressor body 10.

[0028] The solid line is the current value flowing through the compressor body. The current value flowing through the compressor body 10 can be actually measured by an ammeter connected to the compressor body 10. The two-dot chain line is a graph when the graph G2 with an operating capacity (torque) of 50% or more is extrapolated to the region less than 50%. Details will be described later, but at 50% or more, the graph G2 is almost a straight line, and the slope of the graph G2 is about 1. On the other hand, at less than 50%, the graph G3 is a gentle curve, and the slope of the graph G3 is less than 1 (smaller than the slope of the graph G2). Therefore, the slope of the graph G4 shown by the two-dot chain line at less than 50% is about 1. The broken line is a graph showing the motor efficiency.

[0029] Looking at the relationship between the operating capacity (i.e., torque), motor efficiency, and current value, when the operating capacity is, for example, 50% or more, as the operating capacity increases, the motor efficiency gradually increases and asymptotically approaches 100%. On the other hand, the current value increases linearly. From these facts, when the operating capacity is 50% or more, even if the operating capacity fluctuates slightly, the motor efficiency is almost flat and does not fluctuate greatly, but the current value fluctuates greatly.

[0030] On the one hand, when the operating capacity is less than, for example, 50%, as the operating capacity increases, the motor efficiency rapidly increases from 0%. On the other hand, although the current value also increases, the way (degree) of increase is not linear but increases gently (such that the slope of the tangent is less than 1). From these facts, when the operating capacity is less than 50%, if the operating capacity fluctuates, the motor efficiency fluctuates greatly, but the degree of fluctuation of the current value is smaller than when it is 50% or more.

[0031] Thus, in the example of the present disclosure, with 50% as the boundary for the operating capacity (which can be regarded as equivalent to torque), the slope of the graph G1 (correlation), which is the current characteristic showing the relationship between the operating capacity and the current value, is different. And in the example of the present disclosure, the operating capacity is determined from the current value. Specifically, although details will be described later, for example, a database 27 in which the predetermined current value (predetermined value, theoretical value, etc.) when the operating capacity is 100% is recorded is used, and the operating capacity is determined from the predetermined current value and the actually measured value of the current value. For example, if I is recorded as the predetermined current value when the operating capacity is 100%, and the actually measured value of the current value is 0.7×I, the operating capacity is determined to be 70%.

[0032] However, as described above, if the same current characteristic is used regardless of the operating capacity, the accuracy of the determined operating capacity is low and there is a possibility that it cannot be calculated correctly. Specifically, for example, if the substantially linear graphs G2 and G4 (i.e., a single current characteristic) are used to calculate the operating capacity from the current value, in the region where the operating capacity is less than 50%, for example, since the graph G4 deviates from the actual graph G3, the operating capacity cannot be calculated correctly in this region. More specifically, for example, taking the above example of 70%, if the actually measured value of the current value is 0.3×I, if calculated in the same way as when it is 70% above, the operating capacity is determined to be 30%. However, since the current characteristic varies depending on the operating capacity as described above, the actual operating capacity may not be 30%.

[0033] Therefore, as described above, the arithmetic unit 20 has the correlation of the present disclosure. The correlation of the present disclosure is the correlation between the current value flowing through the compressor main body 10 and the operating capacity of the compressor main body 10 as described above, and is stored in advance in the arithmetic unit 20 in the form of, for example, a table, a graph, a mathematical formula, or the like. In the example of FIG. 3, the correlation of the present disclosure is the graph G1 constituted by the graphs G2 and G3. The correlation of the present disclosure includes a first correlation used when the slide valve 4 exists on one side with respect to the predetermined position in the movable range of the slide valve 4, and a second correlation used when the slide valve 4 exists on the other side.

[0034] As an example, if the predetermined position is the position of the slide valve 4 where the operating capacity is 50%, the first correlation is used when the operating capacity is, for example, 50% or more, and in the example of FIG. 3, it is the graph G2. Therefore, when the operating capacity is, for example, 50% or more, the current value and the operating capacity increase and decrease linearly. On the other hand, the second correlation is used when the operating capacity is, for example, less than 50%, and in the example of FIG. 3, it is the graph G3. Therefore, when the operating capacity is, for example, less than 50%, the current value and the operating capacity increase and decrease non-linearly.

[0035] Returning to FIG. 1 for explanation, as described above, the detection mechanism 5 detects that the slide valve 4 has passed through the predetermined position when the slide valve 4 moves. The predetermined position here is the position where the tendency of the correlation of the present disclosure changes. That is, as described with reference to FIG. 3 above, by the detection mechanism 5 detecting the passage of the position where the tendency of the correlation of the present disclosure changes (for example, the operating capacity of 50%), it is possible to grasp whether the slide valve 4 exists in the region where the operating capacity is, for example, 50% or more or less than 50%. In particular, the inflow or outflow of the oil FO into the chamber 13 can be controlled by the opening and closing control of the valves 21, 22, and 23. Therefore, by grasping the opening and closing states of the valves 21, 22, and 23, it is possible to grasp in which direction the slide valve 4 is heading with respect to the predetermined position. By these, according to the existing position of the slide valve 4, the correlation (the first correlation or the second correlation) can be properly used, and the calculation accuracy of the operating capacity calculated from the current value and the correlation can be improved.

[0036] In an example of the present disclosure, when the piston 43 is located farther from the detection mechanism 5 as viewed from the opening 25, the operating capacity is 50% or more. Thus, for example, when the piston 43 moves from right to left in the drawing, if the detection mechanism 5 detects the passage of the piston 43, for example, due to a pressure change, it is considered that the operating capacity has changed from less than 50% to 50% or more. Therefore, when it is 50% or more, the operating capacity is determined from the current value using the first correlation (graph G2).

[0037] On the other hand, when the piston 43 is located closer to the detection mechanism 5 as viewed from the opening 25, the operating capacity is less than 50%. Thus, for example, when the piston 43 moves from left to right in the drawing, if the detection mechanism 5 detects the passage of the piston 43, for example, due to a pressure change, it is considered that the operating capacity has changed from 50% or more to less than 50%. Therefore, when it is less than 50%, the operating capacity is determined from the current value using the second correlation (graph G3).

[0038] Note that the positions of the detection mechanism 5 and the communication passage 52 for detecting that the slide valve 4 has passed through a predetermined position can be determined, for example, by experiments, simulations, trial operations, or the like.

[0039] Also, regarding the graph G1 corresponding to the correlation, the shapes (trends) of the graph G2 and the graph G3 are different with the operating capacity of 50% as the boundary. However, the value of the operating capacity at which the trend of the graph G1 changes may not be 50%. That is, the predetermined position does not necessarily correspond to the position corresponding to the operating capacity of 50%. Therefore, the operating capacity corresponding to the above predetermined position can be appropriately set according to conditions such as the structure of the compressor main body 10 and the type of the gas G to be compressed. The determination method is not particularly limited, but it may be set to different values, for example, by experiments, simulations, trial operations, or the like.

[0040] Further, the predetermined position does not necessarily have to be only one corresponding to, for example, 50% of the operating capacity, and may be a plurality of positions corresponding to each of a plurality of operating capacities according to the shape of the graph G1 shown in FIG. 3, for example. By detecting a plurality of positions such as 25%, 50%, 75% of the operating capacity, for example, the operating capacity can be determined with higher accuracy.

[0041] Among the first correlation and the second correlation included in the correlation of the present disclosure, the first correlation is a correlation in which the current value increases in a first tendency with an increase in the operating capacity. The first correlation is, for example, the correlation shown by the graph G2 in the example of FIG. 3 above, and the graph G2 is, for example, a straight line. Therefore, in the graph G2, the current value increases linearly as described above with an increase in the operating capacity. On the other hand, the second correlation is a correlation in which the current value increases in a second tendency with an increase in the operating capacity. The second tendency is different from the first tendency. The second correlation is, for example, the correlation shown by the graph G3 in the example of FIG. 3 above, and the graph G3 is, for example, a curve in which the slope of the tangent line is less than 1. Therefore, in the graph G3, the current value increases gently as described above with an increase in the operating capacity. Since the current value changes in different tendencies as described above, the calculation accuracy of the operating capacity can be improved by using the correlation of the present disclosure.

[0042] The arithmetic unit 20 corrects the correlation based on the preset value of the current value determined from the correlation of the present disclosure when the operating capacity is a predetermined capacity and the measured value of the current value when the operating capacity is the predetermined capacity. Due to post facto factors such as the aging deterioration of the compressor main body 10 and the aging deterioration of the refrigeration cycle device 200 (described later), the correlation of the present disclosure stored in advance may deviate. For example, if dirt adheres to the inside of the compression chamber 11 or structures such as heat exchangers constituting the refrigeration cycle device 200, the current value may become larger than at the initial stage of operation even if the operating capacity is the same. That is, if the initial correlation is used based on the measured current value, an operating capacity larger than the actual operating capacity may be determined. Therefore, in the example of the present disclosure, the correlation of the present disclosure is corrected based on the preset value and the measured value. Thereby, a decrease in the determination accuracy of the operating capacity can be suppressed.

[0043] For example, by opening the valve 21 and closing the valves 22 and 23 as described above, the bypass passage 3 is blocked, and the operating capacity becomes 100%. Then, taking the operating capacity of 100% as a predetermined capacity, by comparing the actually measured value of the current value at this time with the specified value of the current value when the predetermined capacity is 100% using the correlation of the present disclosure, the necessity for correction can be determined. And, for example, the difference between the actually measured value and the specified value is calculated, and correction may be performed when the difference exceeds a predetermined threshold value at which correction is determined to be necessary.

[0044] The specific method of correction is not particularly limited. For example, by correcting the correlation of the present disclosure and the database 27 so that the current value (predetermined current value; default value) recorded in the following database 27 as the current value when the operating capacity is 100% approaches the actually measured value of the current value when the operating capacity is also 100%, correction can be executed. Further, the correction is not limited to only once, and may be performed a plurality of times, for example, at predetermined time intervals.

[0045] The arithmetic unit 20 notifies the notification device 26 (FIG. 4) when the difference between the above-mentioned default value and the above-mentioned actually measured value exceeds a predetermined threshold value. The predetermined threshold value mentioned here is a value determined in advance and is a reference value (index value) for making a notification. The notification device 26 is, for example, a monitor such as an alarm, a notification device, or a display. By correcting the correlation as described above, the accuracy of determining the operating capacity can be maintained over a long period. However, by notifying when a "deviation" that cannot be corrected occurs, the user can be prompted, for example, to perform maintenance on the compressor main body 10. As a result, the deviation can be recovered, and the accuracy of determining the operating capacity can be recovered. Also, it is possible to notify regardless of the magnitude of the "deviation", and thereby, the user can be informed of the possibility of future maintenance or the like.

[0046] FIG. 4 is a block diagram showing a specific hardware configuration of the arithmetic unit 20. For convenience, the compressor main body 10 and the notification device 26 connected to the arithmetic unit 20 are also shown in FIG. 4.

[0047] The arithmetic unit 20 is configured to include, for example, a CPU (Central Processing Unit) 1001, a RAM (Random Access Memory) 1002, a ROM (Read Only Memory) 1003, an I / F (Inter Face) 1004, a bus 1005, and the like. The CPU 1001, the RAM 1002, the ROM 1003, and the I / F 1004 are connected via, for example, the bus 1005. The arithmetic unit 20 is embodied by a predetermined determination program (for example, a control method for the screw compressor 100) stored in the ROM 1003 being expanded in the RAM 1002 and executed by the CPU 1001. The transmission and reception of signals and information between the arithmetic unit 20 and various devices (the compressor main body 10, the notification device 26, a server not shown, etc.), an external network, etc. are performed hardware-wise through the I / F 1004.

[0048] FIG. 5 is a diagram for explaining the structure of the compressor main body 10 according to another embodiment. In FIGS. 5 and FIGS. 6 and 7 described later, only the vicinity of the chamber 13 of the compressor main body 10 is shown for simplicity of illustration. Also, the illustration of the oil FO and the gas FG is omitted.

[0049] In the embodiment shown in FIG. 5, a plurality of communication passages 52 are provided. Along with this, a pressure detection mechanism 51 is provided for each communication passage 52. In the illustrated example, the communication passages 52 include communication passages 522 and 523. The pressure detection mechanism 51 includes pressure detection mechanisms 511 and 512. The pressure detection mechanism 511 is provided in the communication passage 522, and the pressure detection mechanism 512 is provided in the communication passage 523. Also, the opening 521 includes openings 5211 and 5212. The opening 5211 is connected to the communication passage 522, and the opening 5212 is connected to the communication passage 523.

[0050] In the example of FIG. 5, when the valve body 41 is present at the position where the operating capacity is 50%, the position of the surface 431 constituting the piston 43 is a predetermined position. However, the predetermined position may be the position of the surface 432 or between the surface 431 and the surface 432.

[0051] FIG. 5 illustrates a state where the slide valve 4 is in a predetermined position. The plurality of communication passages 52 are formed as follows. That is, when the slide valve 4 is in the predetermined position, at least one opening 5211 among the openings 521 connected to each of the plurality of communication passages 52 is disposed so as to be exposed to the chamber 131 on one side of the piston 43. At the same time, at least one other opening 5212 among the openings 521 connected to each of the plurality of communication passages 52 is disposed so as to be exposed to the chamber 132 on the other side of the piston 43. Therefore, when the slide valve 4 moves and is in the predetermined position, the pressure detection mechanism 511 detects the pressure in the chamber 131 (the pressure of the oil FO), and the pressure detection mechanism 512 detects the pressure in the chamber 132 (the pressure of the gas FG).

[0052] When the slide valve 4 is in the predetermined position, neither of the openings 5211 and 5212 is entirely exposed to the chamber 13, but only a part of each is exposed. As for the degree of exposure, it is sufficient that the pressure detection mechanism 511 opens the opening to such an extent that it can detect the pressure of the oil FO in the chamber 131, and the pressure detection mechanism 512 can detect the pressure of the gas FG in the chamber 132. However, the smaller the degree of exposure, the more quickly it can be detected that the predetermined position has been reached.

[0053] Also, a wall 55 that forms a part of the casing 1 is formed between the communication passage 522 and the communication passage 523. The surface 551 of the wall 55 facing the chamber 13 contacts the circumferential surface 433 of the piston 43 when the slide valve 4 is in the predetermined position. For this reason, the outflow of the oil FO and the gas FG between the chamber 131 and the chamber 132 is suppressed.

[0054] FIG. 6 is a view showing a state where the slide valve 4 has moved to a predetermined position so that the operating capacity increases in the compressor main body 10 shown in FIG. 5. In FIG. 6, the position of the slide valve 4 (particularly the piston 43) before movement is illustrated by a two-dot chain line.

[0055] When the piston 43 was at the position shown by the two-dot chain line in Fig. 6, both of the pressure detection mechanisms 511 and 512 detected the pressure in chamber 131 (the pressure of oil FO). In this state, when the slide valve 4 moves leftward in the drawing (the suction port side), and the piston 43 reaches a predetermined position (the position shown by the solid line in Fig. 6), the pressure detection mechanism 511 continues to detect the pressure in chamber 131, while the pressure detection mechanism 512 detects the pressure in chamber 132 instead of chamber 131. That is, during the movement of the slide valve 4, for example, just before (when) the peripheral surface 433 of the piston 43 reaches a predetermined position, the opening 5212 is exposed to chamber 132. Thereby, the communication passage 523 and chamber 132 communicate with each other, and the pressure detection mechanism 512 detects the pressure change from the pressure in chamber 131 (for example, relatively high pressure) to the pressure in chamber 132 (for example, relatively low pressure). And when the pressure change is detected, it can be considered that the slide valve 4 has reached a predetermined position, and for example, it can be determined that the operating capacity is 50%.

[0056] Fig. 7 is a view showing a state in which the slide valve 4 has moved to a predetermined position so that the operating capacity becomes small in the compressor main body 10 shown in Fig. 5. Contrary to the case of Fig. 6 above, when the piston 43 was at the position shown by the two-dot chain line in Fig. 6, both of the pressure detection mechanisms 511 and 512 detected the pressure in chamber 132 (the pressure of gas FG). In this state, when the slide valve 4 moves rightward in the drawing (the discharge port side), and the piston 43 reaches a predetermined position (the position shown by the solid line in Fig. 7), the pressure detection mechanism 512 continues to detect the pressure in chamber 132, while the pressure detection mechanism 511 detects the pressure in chamber 131 instead of chamber 132. That is, during the movement of the slide valve 4, for example, just before (when) the surface 431 of the piston 43 reaches a predetermined position, the opening 5211 is exposed to chamber 131. Thereby, the communication passage 522 and chamber 131 communicate with each other, and the pressure detection mechanism 511 detects the pressure change from the pressure in chamber 132 (for example, relatively low pressure) to the pressure in chamber 131 (for example, relatively high pressure). And when the pressure change is detected, it can be considered that the slide valve 4 has reached a predetermined position, and for example, it can be determined that the operating capacity is 50%.

[0057] As described above, when the slide valve 4 reaches a predetermined position, the pressure detection mechanisms 511 and 512 detect a pressure change from the pressure in chamber 131 to the pressure in chamber 132 or from the pressure in chamber 132 to the pressure in chamber 131. And by this detection, it can be detected that the slide valve 4 has reached the predetermined position. Therefore, regardless of an increase or decrease in the operating capacity, the passage of the slide valve 4 through the predetermined position can be detected.

[0058] Note that the number of communication passages 52 is not limited to two in the illustrated example, and may be three or more.

[0059] FIG. 8 is a perspective view of the refrigeration cycle device 200 of the present disclosure. The refrigeration cycle device 200 is a water-cooled screw chiller unit capable of generating chilled water in the example of the present disclosure. The refrigeration cycle device 200 includes a screw compressor 100, a condenser 101, an expansion mechanism 102 (such as an expansion valve), an evaporator 103, and a control panel 104 that controls the screw compressor 100. In the illustrated example, the arithmetic unit 20 provided in the screw compressor 100 is provided in the control panel 104. On the other hand, the compressor main body 10 provided in the screw compressor 100 is provided close to the control panel 104. However, the arithmetic unit 20 may be provided integrally with the compressor main body 10.

[0060] FIG. 9 is a system diagram of the refrigeration cycle device 200 of the present disclosure. A refrigeration cycle is constituted by the circulation (flow) of refrigerant through the refrigerant pipe 105 between the compressor main body 10, the condenser 101, the expansion mechanism 102, and the evaporator 103. Among these, in the example of the present disclosure, the condenser 101 is a heat source side heat exchanger, and the evaporator 103 is a utilization side heat exchanger. However, the combination is not limited to this, and as long as one of the heat exchangers of the condenser 101 or the evaporator 103 is a heat source side heat exchanger and the other heat exchanger is a utilization side heat exchanger.

[0061] The refrigerant compressed by the compressor body 10 flows into the condenser 101 (heat source side heat exchanger) through the refrigerant pipe 105. In the condenser 101, cooling water for dissipating the heat possessed by the refrigerant and the refrigerant are heat-exchanged. As a result, the refrigerant is cooled down in the condenser 101. The cooled-down refrigerant flows into the expansion mechanism 102 through the refrigerant pipe 105, and the refrigerant expands in the expansion mechanism 102 and is further cooled down. The refrigerant after the temperature drop flows into the evaporator 103 (utilization side heat exchanger) through the refrigerant pipe 105. In the evaporator 103, water is cooled by the cooled-down refrigerant, and chilled water supplied to the consumer is obtained. The refrigerant that has cooled the water and increased in temperature is returned to the compressor body 10.

[0062] FIG. 10 is a diagram showing a database 27 provided in the arithmetic unit 20. The database 27 records the specified values of the current values associated with the first temperature and the second temperature. The first temperature is the measured value (actual temperature) of the temperature of the cooling water (an example of a fluid) that has been heat-exchanged with the refrigerant in the condenser 101 (heat source side heat exchanger). The second temperature is the measured value (actual temperature) of the temperature of the chilled water (an example of a fluid) that has been heat-exchanged with the refrigerant in the evaporator 103 (utilization side heat exchanger).

[0063] The first temperature is, for example, the temperature of the cooling water (used) used to cool the refrigerant in the condenser 101, and is also the measured value of the outlet temperature of the condenser 101. The first temperature can be measured, for example, by a temperature sensor 111 installed on the downstream side of the cooling water flow of the condenser 101. In the database 27 shown in FIG. 10, the item on the horizontal axis is the first temperature, and for example, temperatures T1 to T10 are recorded.

[0064] The second temperature is the temperature of the chilled water (chilled water supplied to the consumer) obtained by cooling the refrigerant in the evaporator 103, and is also the measured value of the outlet temperature of the evaporator 103. The second temperature can be measured, for example, by a temperature sensor 112 installed on the downstream side of the chilled water flow of the evaporator 103. In the database 27, the item on the vertical axis is the second temperature, and for example, temperatures T11 to T20 are recorded. Note that in the present disclosure, chilled water and cooling water are different waters although they have similar names.

[0065] In the database 27, as described above, the specified value of the current value flowing through the compressor main body 10 is associated with the first temperature and the second temperature. For example, when the first temperature is T1, for each of the second temperatures T11 to T20, predetermined current values (predetermined values) A1, A11, A21…, A71, A81, A91 are associated. Therefore, if the first temperature and the second temperature are determined, the predetermined value of the current value recorded in the database 27 is determined.

[0066] The current values recorded in the database 27 are "predetermined values" (also referred to as initial values, theoretical values, estimated values, etc.) recorded for each of the first temperature as the cooling water temperature and the second temperature as the chilled water temperature. Also, the current values recorded in the database 27 are the current values (for example, experimental values) when the operating capacity is 100%, which are determined in advance by experiments, simulations, trial operations, etc. Therefore, the current value flowing through the compressor main body 10 operating at 100% of the operating capacity usually becomes the current value recorded in the database 27 according to the measured first temperature and second temperature.

[0067] On the other hand, if the operating capacity becomes less than 100%, accordingly, the current value flowing through the compressor main body 10 also becomes smaller than the current value recorded in the database 27. However, the current value does not always decrease in the same trend (for example, linearly). As described above, the tendency of decrease (correlation) changes with the operating capacity reaching a predetermined value (for example, 50%). Therefore, the detection mechanism 5 is used to determine whether the operating capacity is equal to or greater than the predetermined value or less than the predetermined value, and according to the determination result, the first correlation or the second correlation indicating the tendency of different phenomena is selectively used. Thereby, the operating capacity can be accurately determined using the first correlation or the second correlation selectively used according to the position of the slide valve 4.

[0068] In this way, the arithmetic unit 20 determines a preset current value, i.e., a preset value, associated with the measured first temperature and second temperature, from the first temperature, the second temperature, and the database 27. Further, the arithmetic unit 20 determines which of the first correlation or the second correlation among the correlations of the present disclosure is to be used based on the position of the slide valve 4 detected by the detection mechanism 5. Then, the arithmetic unit 20 determines the operating capacity from the determined preset value, the measured value of the current value flowing through the compressor main body 10, and the first correlation or the second correlation for which the use has been determined. By determining the operating capacity in this way, the determination accuracy of the operating capacity can be improved.

[0069] In the present disclosure, it is not always necessary to constantly grasp the existing position (presence or absence of passage during movement) of the slide valve 4 over the entire movable direction of the slide valve 4. Then, for example, by grasping whether or not a predetermined position such as 50% of the operating capacity has been passed, that is, whether or not the slide valve 4 is present at the predetermined position, the operating capacity can be accurately determined. Thereby, the operating capacity can be determined simply.

[0070] The refrigeration cycle apparatus 200 to which the screw compressor 100 of the present disclosure can be applied is not limited to a water-cooled chiller unit, and may be, for example, an air-cooled chiller unit, a refrigerator, a showcase, an air conditioner, or the like. Therefore, when the refrigeration cycle apparatus 200 is, for example, an air-cooled chiller unit, the first temperature can be the outside air temperature. Further, for example, when the refrigeration cycle apparatus 200 is, for example, a refrigerator, the second temperature can be, for example, the cold air temperature supplied to the refrigerating chamber. Thus, the fluid to be measured for the first temperature and the second temperature may be either a liquid or a gas, the liquid is not limited to water, and the gas is not limited to air.

[0071] Further, the gas compressed by the screw compressor 100 is not limited to a refrigerant, and may be a gas such as air or nitrogen.

Description of Reference Numerals

[0072] 1 Casing 10 Compressor Main Body 100 Screw Compressor 101 Condenser 102 Expansion mechanism 103 Evaporator 104 Control panel 105 Refrigerant pipe 11 Compression chamber 111 Temperature sensor 112 Temperature sensor 12 Chamber 13 Chamber 131 Chamber 132 Chamber 2 Screw rotors 20 Arithmetic unit 200 Refrigeration cycle device 21 Valve 22 Valve 23 Valve 24 Flow path 25 Opening 26 Notification device 27 Database 3 Bypass flow path 4 Slide valve 41 Valve body 42 Rod 43 Piston 431 Surface 432 Surface 433 Peripheral surface 5 Detection mechanism 51 Pressure detection mechanism 511 Pressure detection mechanism 512 Pressure detection mechanism 52 Communication path 521 Opening 5211 Opening 5212 Opening 522 Communication path 523 Communication path 55 Wall

Claims

1. A screw compressor used in a range of operating capacities including 0% to 20% of the operating capacity, comprising: a compressor body and an arithmetic unit; wherein the compressor body includes: a casing; a screw rotor that is rotationally driven within the casing; a bypass flow path that communicates from a compression chamber formed between the casing and the screw rotor to the suction side of the compression chamber; a slide valve that is movable to adjust the opening degree of the bypass flow path; a detection mechanism that detects that the slide valve has passed a predetermined position when the slide valve moves within the movable range of the slide valve; and wherein the arithmetic unit: has a correlation between the current value flowing through the compressor body and the operating capacity of the compressor body; the correlation includes a first correlation used when the slide valve is present on one side with respect to the predetermined position within the movable range of the slide valve, and a second correlation used when the slide valve is present on the other side; determines which of the first correlation or the second correlation to use based on the position of the slide valve detected by the detection mechanism, and determines the operating capacity from the current value flowing through the compressor body and the determined first correlation or second correlation. A screw compressor characterized by the above.

2. The screw compressor according to claim 1, wherein the position of the slide valve is controlled by hydraulic pressure, and the slide valve includes a valve body that is contacted by the gas compressed by the compressor body, and a piston that is connected to the valve body and is housed in a chamber different from the chamber in which the valve body is housed; the detection mechanism detects that the slide valve has passed a predetermined position by detecting the position of the piston. A screw compressor characterized by the above.

3. The screw compressor according to claim 2, wherein the detection mechanism is a pressure detection mechanism installed in a communication path that communicates the inside and outside of the chamber that houses the piston. A screw compressor characterized by the above.

4. The screw compressor according to claim 3, wherein a plurality of the communication paths are provided, and the pressure detection mechanism is provided for each of the communication paths; when the slide valve is in the predetermined position, at least one of the openings connected to each of the plurality of communication paths is disposed so as to be exposed to the chamber on one side of the piston. At least one other opening among the openings connected to each of the plurality of communication passages is disposed so as to be exposed to the chamber on the other side of the piston. A plurality of the communication passages are formed. A screw compressor characterized by this.

5. A screw compressor according to any one of claims 1 to 4, The predetermined position is a position where the tendency of the correlation changes. A screw compressor characterized by this.

6. A screw compressor according to any one of claims 1 to 4, The first correlation is a correlation in which the current value increases in a first tendency with an increase in the operating capacity. The second correlation is a correlation in which the current value increases in a second tendency different from the first tendency with an increase in the operating capacity. A screw compressor characterized by this.

7. A screw compressor according to any one of claims 1 to 4, The arithmetic unit corrects the correlation based on a predetermined value of the current value determined from the correlation when the operating capacity is a predetermined capacity and an actually measured value of the current value when the operating capacity is the predetermined capacity. A screw compressor characterized by this.

8. A screw compressor according to claim 7, The arithmetic unit notifies a notification device when the difference between the predetermined value and the actually measured value exceeds a predetermined threshold value. A screw compressor characterized by this.

9. A screw compressor, a condenser, an expansion mechanism, and an evaporator are provided. The screw compressor is used in a range of operating capacity including 0% to 20% of the operating capacity, and includes a compressor main body and an arithmetic unit. The compressor main body is A casing, A screw rotor that is rotationally driven within the casing, A bypass flow path that communicates from a compression chamber formed between the casing and the screw rotor to the suction side of the compression chamber, A slide valve that is movable so as to adjust the opening degree of the bypass flow path, A detection mechanism that detects that the slide valve has passed through a predetermined position when the slide valve moves within the movable range of the slide valve. The arithmetic unit is It has a correlation between the current value flowing through the compressor main body and the operating capacity of the compressor main body. The correlation includes a first correlation used when the slide valve exists on one side with respect to the predetermined position within the movable range of the slide valve and a second correlation used when the slide valve exists on the other side. Based on the position of the slide valve detected by the detection mechanism, determine which of the first correlation or the second correlation to use, and determine the operating capacity from the current value flowing through the compressor body and the determined first correlation or second correlation. A refrigeration cycle apparatus characterized by the above.

10. A refrigeration cycle apparatus comprising a screw compressor, a condenser, an expansion mechanism, and an evaporator, wherein a refrigerant circulates between a heat source side heat exchanger which is one of the condenser and the evaporator and a utilization side heat exchanger which is the other heat exchanger, The screw compressor includes a compressor body and an arithmetic unit. The compressor body A casing, A screw rotor that is rotationally driven within the casing, A bypass flow path that communicates from a compression chamber formed between the casing and the screw rotor to the suction side of the compression chamber, A slide valve that is movable so as to adjust the opening degree of the bypass flow path, And a detection mechanism that detects that the slide valve has passed a predetermined position when the slide valve moves within the movable range of the slide valve. The arithmetic unit Has a correlation between the current value flowing through the compressor body and the operating capacity of the compressor body, The correlation includes a first correlation used when the slide valve exists on one side with respect to the predetermined position within the movable range of the slide valve, and a second correlation used when the slide valve exists on the other side. A database that records a predetermined value of the current value associated with a first temperature which is a measured value of the temperature of the fluid heat-exchanged with the refrigerant in the heat source side heat exchanger and a second temperature which is a measured value of the temperature of the fluid heat-exchanged with the refrigerant in the utilization side heat exchanger. Determine the predetermined value from the first temperature, the second temperature, and the database. Based on the position of the slide valve detected by the detection mechanism, determine which of the first correlation or the second correlation to use. Determine the operating capacity from the determined predetermined value, the measured value of the current value flowing through the compressor body, and the determined first correlation or second correlation. A refrigeration cycle apparatus characterized by the above.

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