JP7716465B2 - Screw compressor and refrigeration cycle device - Google Patents

Description

This disclosure relates to a screw compressor and a refrigeration cycle device.

The technology described in Patent Document 1 is known as a technology for detecting the operating capacity of a screw compressor. Patent Document 1 states that "The detector 26 of the capacity detection device 25, which consists of a controller 28, a detector 26, and a display 27, is attached to the cylinder wall 10, and the detector 26 and controller 28 detect the position of the piston 9, i.e., the position of the slide valve 3, to determine the operating capacity of the compressor and output it to the display 27."

Japanese Patent Application Publication No. 9-158867

In the technology described in Patent Document 1, ultrasonic waves are transmitted to the piston 9 sliding inside the cylinder chamber 19, and reflected waves from the piston 9 are received (paragraph 0011). The ultrasonic waves are transmitted at set time intervals (paragraph 0018). This makes it possible to detect the position of the piston and determine the operating capacity of the compressor (paragraph 0011). However, as will be described in detail later, the inventors have conducted research and found that the operating capacity can be accurately determined without constantly knowing the position of the piston 9 throughout its 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 that can accurately grasp the operating capacity.

a screw rotor that is rotationally driven within the casing; a bypass flow path that communicates with a compression chamber formed between the casing and the screw rotor and the suction side of the compression chamber; a slide valve that is movable to adjust the opening 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 its movable range, wherein the calculation device has a correlation between a value of a current flowing through the compressor body and the operating capacity of the compressor body, the correlation including a first correlation that is used when the slide valve is located on one side of the predetermined position within the movable range of the slide valve, and a second correlation that is used when the slide valve is located on the other side , and the calculation device determines whether the first correlation or the second correlation is to be used based on the position of the slide valve detected by the detection mechanism, and determines the operating capacity from the value of the current flowing through the compressor body and the determined first correlation or second correlation . Other solutions will be described later in the detailed description of the invention.

This disclosure provides a screw compressor and refrigeration cycle device that can accurately grasp operating capacity.

FIG. 1 is a diagram illustrating the structure of the compressor body, showing the position of the slide valve when gas is compressed with the operating capacity at approximately 100%. FIG. 1 is a diagram illustrating the structure of the compressor body, showing the position of the slide valve when gas is compressed at approximately 50% operating capacity. 10 is a graph illustrating the relationship between torque and operating capacity, and motor efficiency and current value. FIG. 2 is a block diagram showing a specific hardware configuration of the arithmetic device. 10A and 10B are diagrams illustrating the structure of a compressor main body according to another embodiment. 6 is a diagram showing a state in which the slide valve has moved to a predetermined position so as to increase the operating capacity in the compressor body shown in FIG. 5. FIG. 6 is a diagram showing a state in which the slide valve has moved to a predetermined position so as to reduce the operating capacity in the compressor body shown in FIG. 5. FIG. 1 is a perspective view of a refrigeration cycle device according to the present disclosure. 1 is a system diagram of a refrigeration cycle device according to the present disclosure. FIG. 2 is a diagram illustrating a database provided in the computing device.

Below, modes for implementing the present disclosure (referred to as "embodiments") will be described with reference to the drawings. Within the description of one embodiment below, other embodiments that can be applied to the first embodiment will also be described as appropriate. The present disclosure is not limited to the single embodiment below, and different embodiments can be combined or modified as desired without significantly impairing the effects of the present disclosure. Furthermore, the same components will be given the same reference numerals, and duplicate descriptions will be omitted. Furthermore, components having the same functions will be given the same names. The contents shown are merely schematic, and for the sake of illustration, the actual configuration may be changed, and some components may be omitted or modified between drawings, without significantly impairing the effects of the present disclosure. Furthermore, the same embodiment does not necessarily have to include all of the components.

Figure 1 is a diagram explaining the structure of the screw compressor 100, showing the position of the slide valve 4 when compressing gas at approximately 100% operating capacity. The screw compressor 100 comprises the compressor main body 10 shown in Figure 1 and the computing device 20 shown in Figure 4 below. The hollow arrows shown covering the screw rotor 2 indicate the flow of refrigerant gas G sucked in from the intake port (not shown) of the compressor main body 10.

The compressor body 10 of the present disclosure is a variable-capacity screw compressor whose operating capacity can be changed. In the compressor body 10, a portion of the intake gas G (e.g., refrigerant, air, etc.) is returned to the intake side (i.e., bypassed). The amount of gas G returned to the intake side is changed by controlling the position of the slide valve 4.

The compressor body 10 comprises a casing 1, a screw rotor 2, a bypass flow path 3, a slide valve 4, and a detection mechanism 5.

The casing 1 has an internal compression chamber 11 (chamber) that compresses gas G drawn in through an intake port (not shown) formed in the compressor body 10. The screw rotor 2 is driven to rotate 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 when driven by the motor. While only one screw rotor 2 is shown in Figure 1, a pair of screw rotors 2 may be provided, for example. The gas G is compressed in the compression chamber 11 formed between the pair of screw rotors 2 and the casing 1 when they mesh with each other.

The bypass flow path 3 is a flow path (passage) that connects the compression chamber 11 (for example, a position midway through the compression of 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. Gas G is drawn into the suction port (not shown) of the compressor main body 10, and a portion of the drawn gas G, gas GB, passes through the bypass flow path 3 and is returned to the suction side of the compression chamber 11. The remaining portion of gas G, gas GP, is compressed in the compression chamber 11 and, after compression, is discharged from the compressor main body 10 through the discharge port (not shown).

The slide valve 4 is movable to adjust the opening of the bypass flow path 3. The slide valve 4 moves coaxially within a predetermined range, from one side to the other or from the other side to the one side. The opening (cross-sectional area) of the bypass flow path 3 is controlled by moving the slide valve 4, for example, horizontally. In the illustrated example, the opening of the bypass flow path 3 can be reduced by moving the slide valve 4 horizontally away from the discharge port (not shown) and further so as to block the bypass flow path 3. By reducing the opening of the bypass flow path 3, the amount of bypassed gas GB decreases relatively, while the amount of gas GP discharged after compression increases relatively. This relatively increases the operating capacity. Furthermore, by increasing the opening of the bypass flow path 3, the amount of bypassed gas GB increases relatively, while the amount of gas GP discharged after compression decreases relatively. This relatively reduces the operating capacity.

The slide valve 4 comprises a substantially cylindrical valve body 41, a rod 42, and, for example, a disk-shaped piston 43. The valve body 41 comes into contact with the gas G compressed by the compressor body 10, and forms, for example, the wall surface of the bypass flow path 3. In the direction of movement of the slide valve 4, one surface of the valve body 41 forms the wall surface of the bypass flow path 3, and the other surface forms the wall surface of the flow path through which the compressed gas GP flows.

The piston 43 is connected to the valve body 41 and is housed in a chamber 13 (described below) that is different from the chamber 12 in which the valve body 41 is housed. The valve body 41 and piston 43 are connected by a rod 42. Therefore, by moving the piston 43, which is located outside the chamber 12, the valve body 41 can be moved horizontally within the chamber 12 via the rod 42.

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 chambers 12 and 13 communicate with each other via a communication passage (not shown) through which the rod 42 passes. However, no exchange of gas or liquid takes place between the chambers 12 and 13. The ends (e.g., upper and lower ends) of the piston 43 perpendicular to the direction of movement (sliding direction) have a shape (width, size) that allows them to close the opening 521 of the communication passage 52 (described below) that faces the chamber 12.

The position of the slide valve 4 is controlled hydraulically. The piston 43 connected to the valve body 41 has one surface 431 and the other surface 432. The piston 43 moves toward surface 432 due to the pressure of the oil FO present on the surface 431 side. Chamber 13 includes chambers 131 and 132. Chamber 131 is connected to the oil FO supply source and discharge destination (neither shown), and as described above, oil FO is present in chamber 131. Chamber 132 is connected to, for example, the suction side of compression chamber 11 through opening 25, and gas FG is present in chamber 132. The gas FG is, for example, a refrigerant present on the suction side of compression chamber 11. Therefore, gas FG is a gas (e.g., a refrigerant) at a relatively lower pressure than the compressed gas GP (e.g., a refrigerant).

The side of the valve body 41 facing the bypass flow path 3 (one side) is under relatively low pressure because uncompressed (bypassed) gas GB is present. However, if the bypass flow path 3 is blocked, no gas GB is present on the side facing the bypass flow path 3. On the other hand, the compressed gas GP is present on the side of the valve body 41 opposite the bypass flow path 3, i.e., the side facing the compression chamber 11 (the other side). Therefore, a force is applied to the valve body 41 in a direction that blocks the bypass flow path 3 (from right to left on the page) due to the pressure of the relatively high-pressure gas GP present in the compression chamber 11.

Figure 2 is a diagram explaining the structure of the screw compressor 100 (compressor body 10), showing the position of the slide valve 4 when compressing gas at an operating capacity of approximately 50%. When the operating capacity is changed from the operating capacity of approximately 100% shown in Figure 1 above to the operating capacity of approximately 50% shown in Figure 2, the slide valve 4 moves as shown by the dashed arrow.

When valves 21 and 23 are closed and valve 22 is opened, relatively high-pressure oil FO flows into chamber 131 through flow path 24, as indicated by the solid arrow. As described above, oil FO is supplied from a supply source (not shown). This supply pushes piston 43 from surface 431 toward surface 432, resisting the force exerted on valve body 41 by the pressure of the oil FO. As a result, valve body 41 connected to piston 43 moves to increase the opening of bypass flow path 3, as indicated by the dashed arrow in Figure 2. At this time, as piston 43 moves, gas FG present in chamber 132 is discharged from chamber 132 through opening 25, as indicated by the hollow arrow.

When returning from the state shown in Figure 2 to the state shown in Figure 1, the operations described above are reversed. First, valves 22 and 23 are closed and valve 21 is opened, allowing oil FO in chamber 131 to be discharged through flow path 24 to the oil FO discharge destination (not shown). As described above, the compressed gas GP applies a force to valve body 41 in a direction that blocks bypass flow path 3. As a result, valve body 41 moves in a direction that blocks bypass flow path 3, as shown by the dashed arrow in Figure 1, while pushing oil FO in chamber 131 toward the discharge destination. At this time, gas FG flows into chamber 132 through opening 25 as piston 43 moves.

Returning to FIG. 1 , the detection mechanism 5 detects that the slide valve 4 has passed a predetermined position as the slide valve 4 moves within its movable range. In other words, it detects that the slide valve 4 is at a predetermined position within its movable range. In the example disclosed herein, the detection mechanism 5 detects that the slide valve 4 has passed a predetermined position by detecting the position of the piston 43, which moves with the valve body 41, as the valve body 41 moves within its predetermined movable range. As described above, the valve body 41 and the piston 43 are integrally configured with the rod 42. Therefore, by detecting that the piston 43 has passed (is at) a predetermined position as the slide valve 4 moves, it is possible to indirectly detect that the slide valve 4 (particularly the valve body 41) has passed a predetermined position.

The valve body 41 and piston 43 move together. Therefore, the slide valve 4 passing through a predetermined position (being at a predetermined position) is synonymous with the valve body 41 passing through the predetermined position and the piston 43 passing through the predetermined position.

In the example disclosed herein, the detection mechanism 5 is a pressure detection mechanism 51 installed in the communication passage 52 (e.g., installed outside the chamber 13). The communication passage 52 connects the inside and outside of the chamber 13, which houses the piston 43. When the slide valve 4 (valve body 41 and piston 43) moves, the pressure in chamber 131 differs from the pressure in chamber 132. For example, when the piston 43 moves toward surface 432, the pressure in chamber 131 is higher than the pressure in chamber 132. Therefore, the pressure in chamber 13 changes across the piston 43. For this reason, by detecting the pressure change in chamber 13 using the pressure detection mechanism 51, which is connected to the inside of chamber 13, it is possible to detect that the piston 43 has reached the communication passage 52, i.e., that it is in a predetermined position.

The predetermined position detected when the slide valve 4 (particularly the valve body 41) moves is the position where the tendency of the correlation between the current value (operating current value) flowing through the compressor body 10 and the operating capacity of the compressor body 10 (hereinafter referred to as the correlation in this disclosure as appropriate) changes. This point will be explained with reference to Figure 3.

Figure 3 is a graph illustrating the relationship between torque and operating capacity and 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; for example, torque and operating capacity are often considered to be the same. Therefore, the horizontal axis can be thought of as the torque and operating capacity of the compressor body 10. The torque on the horizontal axis is expressed as a percentage (%) with the maximum torque (rated value) being 100%, and the operating capacity on the horizontal axis is expressed as a percentage (%) with the maximum operating capacity (maximum capacity) being 100%. The vertical axis on the left represents motor efficiency (%), and the vertical axis on the right represents the current value flowing through the compressor body 10.

The solid line represents the current value flowing through the compressor body. The current value flowing through the compressor body 10 can be measured using an ammeter connected to the compressor body 10. The two-dot chain line represents the extrapolation of graph G2, where the operating capacity (torque) is 50% or higher, to the region below 50%. As will be described in detail later, at 50% or higher, graph G2 is an almost straight line, with a slope of approximately 1. On the other hand, at less than 50%, graph G3 is a gentle curve, with a slope of less than 1 (smaller than the slope of graph G2). Therefore, at less than 50%, the slope of graph G4, shown by the two-dot chain line, is approximately 1. The dashed line represents motor efficiency.

Looking at the relationship between operating capacity (i.e., torque), motor efficiency, and current value, when the operating capacity is, for example, 50% or above, as the operating capacity increases, motor efficiency increases gradually and asymptotically approaches 100%. Meanwhile, the current value increases linearly. From these facts, when the operating capacity is 50% or above, even if the operating capacity fluctuates slightly, motor efficiency will almost plateau and will not fluctuate greatly, but the current value will fluctuate greatly.

On the other hand, when the operating capacity is, for example, less than 50%, motor efficiency increases sharply from 0% as the operating capacity increases. Meanwhile, the current value also increases, but the manner (degree) of increase is not linear, but increases gradually (so that the slope of the tangent line is less than 1). For these reasons, when the operating capacity is less than 50%, motor efficiency fluctuates greatly when the operating capacity fluctuates, but the degree of fluctuation in the current value is smaller than when the operating capacity is 50% or more.

In this way, in the example of the present disclosure, the slope of graph G1 (correlation), which is the current characteristic showing the relationship between operating capacity and current value, changes when the operating capacity (which can be viewed as the same as torque) reaches 50%. In the example of the present disclosure, the operating capacity is determined from the current value. Specifically, details will be provided later, but for example, a database 27 that records the default current value (default value, theoretical value, etc.) when the operating capacity is 100% is used, and the operating capacity is determined from the default current value and the actual measured current value. For example, if I is recorded as the default current value when the operating capacity is 100%, and the actual measured current value is 0.7 x I, the operating capacity is determined to be 70%.

However, as mentioned above, if the same current characteristics are used regardless of the operating capacity, the operating capacity determined will be less accurate and may not be calculated correctly. Specifically, if the operating capacity is calculated from the current value using, for example, the approximately linear graphs G2 and G4 (i.e., a single current characteristic), graph G4 will deviate from the actual graph G3 below 50%, and the operating capacity cannot be calculated correctly in this region. More specifically, for example, in the above example of 70%, if the actual measured current value is 0.3 x I, the operating capacity will be determined to be 30% if calculated in the same way as for 70%. However, because the current characteristics differ depending on the operating capacity as mentioned above, the actual operating capacity may not be 30%.

As described above, the calculation device 20 has the correlation of the present disclosure. The correlation (relationship) 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 pre-stored in the calculation device 20 in the form of, for example, a table, graph, or formula. In the example of Figure 3, the correlation of the present disclosure is graph G1 made up of graphs G2 and G3. The correlation of the present disclosure includes a first correlation used when the slide valve 4 is on one side of the predetermined position within the movable range of the slide valve 4, and a second correlation used when it is on the other side.

As an example, if the specified 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 higher, as shown by graph G2 in the example in Figure 3. Therefore, when the operating capacity is, for example, 50% or higher, the current value and operating capacity increase or decrease linearly. On the other hand, the second correlation is used when the operating capacity is, for example, less than 50%, as shown by graph G3 in the example in Figure 3. Therefore, when the operating capacity is, for example, less than 50%, the current value and operating capacity increase or decrease nonlinearly.

Returning to FIG. 1 , as described above, the detection mechanism 5 detects that the slide valve 4 has passed a predetermined position during its movement. The predetermined position here refers to the position where the correlation trend of the present disclosure changes. That is, as described above with reference to FIG. 3 , the detection mechanism 5 detects the passage of a position where the correlation trend of the present disclosure changes (e.g., an operating capacity of 50%), thereby determining whether the slide valve 4 is in a region where the operating capacity is above 50% or below 50%. In particular, the inflow or outflow of oil FO into chamber 13 can be controlled by controlling the opening and closing of valves 21, 22, and 23. Therefore, by determining the opening and closing states of valves 21, 22, and 23, it is possible to determine which direction the slide valve 4 is moving relative to the predetermined position. This allows the use of a correlation (first correlation or second correlation) depending on the position of the slide valve 4, improving the calculation accuracy of the operating capacity calculated from the current value and correlation.

In the example disclosed herein, when the piston 43 is located farther away from the detection mechanism 5 as viewed from the opening 25, the operating capacity is 50% or more. Therefore, for example, when the piston 43 moves from right to left on the page, if the detection mechanism 5 detects the passage of the piston 43 due to a change in pressure, the operating capacity is considered to have changed from less than 50% to 50% or more. Therefore, when the operating capacity is 50% or more, the first correlation (graph G2) is used to determine the operating capacity from the current value.

On the other hand, when viewed from the opening 25, the piston 43 is closer than the detection mechanism 5, the operating capacity is less than 50%. Therefore, for example, when the piston 43 moves from left to right on the page, if the detection mechanism 5 detects the passage of the piston 43 due to a change in pressure, the operating capacity is considered to have changed from 50% or more to less than 50%. Therefore, when the operating capacity is less than 50%, the second correlation (graph G3) is used to determine the operating capacity from the current value.

The positions of the detection mechanism 5 and communication passage 52 for detecting when the slide valve 4 has passed a predetermined position can be determined, for example, through experiments, simulations, trial runs, etc.

Furthermore, for graph G1 corresponding to the correlation, the shapes (trends) of graphs G2 and G3 differ at the boundary of 50% operating capacity. However, the operating capacity value at which the trend of graph G1 changes may not be 50%. In other words, the predetermined position does not have to be a position corresponding to 50% operating capacity. Therefore, the operating capacity corresponding to the above-mentioned predetermined position can be set appropriately depending on conditions such as the structure of the compressor main body 10 and the type of gas G to be compressed. There are no particular restrictions on the method of determination, and different values may be set, for example, through experiments, simulations, trial runs, etc.

Furthermore, the predetermined position does not have to be just one, corresponding to, for example, 50% operating capacity, but may be multiple positions corresponding to multiple operating capacities, depending on, for example, the shape of graph G1 shown in Figure 3. For example, by detecting multiple positions, such as 25%, 50%, 75% operating capacity, the operating capacity can be determined with even greater accuracy.

Of the first and second correlations included in the correlations disclosed herein, the first correlation is a correlation in which the current value increases in a first trend as the operating capacity increases. For example, in the example of Figure 3 above, the first correlation is the correlation shown by graph G2, which is, for example, a straight line. Therefore, in graph G2, the current value increases linearly as the operating capacity increases, as described above. On the other hand, the second correlation is a correlation in which the current value increases in a second trend as the operating capacity increases. The second trend is a trend different from the first trend. For example, in the example of Figure 3 above, the second correlation is the correlation shown by graph G3, which is, for example, a curve with a tangent slope of less than 1. Therefore, in graph G3, the current value increases gradually as the operating capacity increases, as described above. Because the current value changes in different trends as described above, using the correlations disclosed herein can improve the accuracy of calculating the operating capacity.

The calculation device 20 corrects the correlation based on the default current value determined from the correlation of the present disclosure when the operating capacity is a predetermined capacity and the actual measured current value when the operating capacity is the predetermined capacity. The pre-stored correlation of the present disclosure may become misaligned due to subsequent factors such as aging of the compressor main body 10 and aging of the refrigeration cycle device 200 (described below). For example, if dirt adheres to the interior of the compression chamber 11 or to structures such as the heat exchanger that make up the refrigeration cycle device 200, the current value may become higher than at the start of operation, even if the operating capacity remains the same. In other words, if an initial correlation based on the actually measured current value is used, an operating capacity greater 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 default value and the actual measured value. This prevents a decrease in the accuracy of determining the operating capacity.

For example, as described above, by opening valve 21 and closing valves 22 and 23, bypass flow path 3 is blocked, and the operating capacity becomes 100%. Then, with 100% operating capacity as the predetermined capacity, the actual measured current value at this time can be compared with the specified current value at 100% predetermined capacity using the correlation disclosed herein to determine whether correction is necessary. Then, for example, the difference between the actual measured value and the specified value can be calculated, and correction can be performed when this difference exceeds a predetermined threshold value at which correction is deemed necessary.

The specific method of correction is not particularly limited. For example, correction can be performed by correcting the correlation and database 27 of the present disclosure so that the current value (default current value) recorded in database 27 described below as the current value at 100% operating capacity approaches the actual measured current value at 100% operating capacity. Furthermore, correction is not limited to being performed only once, but may be performed multiple times, for example, at predetermined time intervals.

The computing device 20 notifies the notification device 26 (Figure 4) when the difference between the preset value and the actual measured value exceeds a predetermined threshold. The predetermined threshold here is a predetermined value and a reference value (index value) for issuing a notification. The notification device 26 is, for example, an alarm, annunciator, display, or other monitor. By correcting the correlation as described above, the accuracy of determining the operating capacity can be maintained over a long period of time. However, by issuing a notification when a deviation that cannot be corrected occurs, the user can be prompted to perform maintenance on the compressor main body 10, for example. This allows the deviation to be corrected and the accuracy of determining the operating capacity to be restored. It is also possible to issue a notification regardless of the magnitude of the deviation, thereby informing the user of the possibility of future maintenance, etc.

Figure 4 is a block diagram showing the specific hardware configuration of the computing device 20. For convenience, Figure 4 also shows the compressor main body 10 and the alarm device 26 connected to the computing device 20.

The calculation device 20 is configured with, for example, a CPU (Central Processing Unit) 1001, RAM (Random Access Memory) 1002, ROM (Read Only Memory) 1003, I/F (Interface) 1004, bus 1005, etc. The CPU 1001, RAM 1002, ROM 1003, and I/F 1004 are connected, for example, via bus 1005. The calculation device 20 is realized by a predetermined judgment program (for example, a control method for the screw compressor 100) stored in ROM 1003 being expanded into RAM 1002 and executed by the CPU 1001. In terms of hardware, signals and information are exchanged between the computing device 20 and various devices (compressor main body 10, notification device 26, server (not shown), etc.), external networks, etc. via I/F 1004.

Figure 5 is a diagram illustrating the structure of a compressor body 10 according to another embodiment. For simplicity's sake, Figure 5 and Figures 6 and 7 below only show the compressor body 10 near the chamber 13. Furthermore, the oil FO and gas FG are not shown.

In the embodiment shown in FIG. 5, multiple communication passages 52 are provided. A pressure detection mechanism 51 is also 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. Furthermore, 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.

In the example of Figure 5, the predetermined position is the position of surface 431 that constitutes piston 43 when valve body 41 is at a position where the operating capacity is 50%. However, the predetermined position may also be the position of surface 432, or it may be between surfaces 431 and 432.

Figure 5 shows the slide valve 4 in a predetermined position. The multiple communication passages 52 are formed as follows. That is, when the slide valve 4 is in a predetermined position, at least one opening 5211 of the openings 521 connected to each of the multiple communication passages 52 is exposed to the chamber 131 on one side of the piston 43. At the same time, at least another opening 5212 of the openings 521 connected to each of the multiple communication passages 52 is exposed to the chamber 132 on the other side of the piston 43. Therefore, when the slide valve 4 moves and the slide valve 4 is in a 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).

When the slide valve 4 is in the predetermined position, neither the entire opening 5211 nor the opening 5212 is exposed to the chamber 13, but only a portion of each. The degree of exposure is sufficient so that the pressure detection mechanism 511 can detect the pressure of the oil FO in chamber 131, and the pressure detection mechanism 512 can detect the pressure of the gas FG in chamber 132. However, a smaller degree of exposure makes it possible to more quickly detect that the predetermined position has been reached.

A wall 55, which constitutes part of the casing 1, is formed between the communication passages 522 and 523. The surface 551 of the wall 55 facing the chamber 13 comes into contact with the peripheral surface 433 of the piston 43 when the slide valve 4 is in a predetermined position. This prevents oil FO and gas FG from leaking between the chambers 131 and 132.

Figure 6 shows the state in which the slide valve 4 has moved to a predetermined position in the compressor body 10 shown in Figure 5 to increase the operating capacity. In Figure 6, the position of the slide valve 4 (particularly the piston 43) before movement is shown by a two-dot chain line.

When the piston 43 was positioned as shown by the two-dot chain line in Figure 6, both pressure detection mechanisms 511 and 512 detected the pressure in chamber 131 (oil FO pressure). In this state, when the slide valve 4 moved leftward (toward the suction port) and the piston 43 reached a predetermined position (the position shown by the solid line in Figure 6), the pressure detection mechanism 511 continued to detect the pressure in chamber 131, while the pressure detection mechanism 512 detected the pressure in chamber 132, not chamber 131. That is, during the movement of the slide valve 4, for example, just before (or when) the circumferential surface 433 of the piston 43 reached the predetermined position, the opening 5212 was exposed to chamber 132. This established communication between the communication passage 523 and chamber 132, and the pressure detection mechanism 512 detected a pressure change from the pressure in chamber 131 (e.g., a relatively high pressure) to the pressure in chamber 132 (e.g., a relatively low pressure). When this pressure change is detected, it can be assumed that the slide valve 4 has reached a predetermined position, and it can be determined that the operating capacity is, for example, 50%.

Figure 7 shows the state in which the slide valve 4 in the compressor body 10 shown in Figure 5 has moved to a predetermined position to reduce the operating capacity. Contrary to the case in Figure 6 above, when the piston 43 was in the position indicated by the two-dot chain line in Figure 6, both 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 moved to the right (toward the discharge port) and the piston 43 reached a predetermined position (the position indicated by the solid line in Figure 7), the pressure detection mechanism 512 continued to detect the pressure in chamber 132, while the pressure detection mechanism 511 detected the pressure in chamber 131, not chamber 132. That is, during the movement of the slide valve 4, for example, just before (or when) the face 431 of the piston 43 reaches the predetermined position, the opening 5211 is exposed to chamber 131. This connects the communication passage 522 to the chamber 131, and the pressure detection mechanism 511 detects a change in pressure from the pressure in chamber 132 (e.g., a relatively low pressure) to the pressure in chamber 131 (e.g., a relatively high pressure). When this pressure change is detected, it can be assumed that the slide valve 4 has reached a predetermined position, and it can be determined that the operating capacity is, for example, 50%.

In this way, the pressure detection mechanisms 511, 512 detect a change in pressure from chamber 131 to chamber 132, or from chamber 132 to chamber 131, when the slide valve 4 reaches a predetermined position. This detection makes it possible to detect that the slide valve 4 has reached a predetermined position. Therefore, it is possible to detect that the slide valve 4 has passed through the predetermined position regardless of whether the operating capacity increases or decreases.

The number of communication passages 52 is not limited to two as shown in the example, and may be three or more.

Figure 8 is a perspective view of a refrigeration cycle apparatus 200 of the present disclosure. In the example of the present disclosure, the refrigeration cycle apparatus 200 is a water-cooled screw chiller unit capable of producing chilled water. The refrigeration cycle apparatus 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 example shown, the computing device 20 included in the screw compressor 100 is provided on the control panel 104. Meanwhile, the compressor main body 10 included in the screw compressor 100 is provided adjacent to the control panel 104. However, the computing device 20 may also be provided integrally with the compressor main body 10.

Figure 9 is a system diagram of the refrigeration cycle apparatus 200 of the present disclosure. A refrigeration cycle is formed by circulating (flowing) refrigerant through refrigerant piping 105 between the compressor main body 10, condenser 101, expansion mechanism 102, and evaporator 103. In the example of the present disclosure, the condenser 101 is the heat source side heat exchanger, and the evaporator 103 is the user side heat exchanger. However, the combination is not limited to this, and it is sufficient that one of the heat exchangers, the condenser 101 or the evaporator 103, is the heat source side heat exchanger and the other is the user side heat exchanger.

The refrigerant compressed in the compressor main body 10 flows into the condenser 101 (heat source side heat exchanger) through the refrigerant piping 105. In the condenser 101, the refrigerant exchanges heat with cooling water, which dissipates the heat contained in the refrigerant. This causes the refrigerant to cool in the condenser 101. The cooled refrigerant flows into the expansion mechanism 102 through the refrigerant piping 105, where it expands and further cools. After cooling, the refrigerant flows into the evaporator 103 (user side heat exchanger) through the refrigerant piping 105. In the evaporator 103, the cooled refrigerant cools water, producing chilled water that is supplied to consumers. The refrigerant, which has cooled the water and raised its temperature, is returned to the compressor main body 10.

Figure 10 is a diagram showing the database 27 provided in the computing device 20. The database 27 records the specified values of the above-mentioned current values linked to the first temperature and the second temperature. The first temperature is the actual measured value (actual temperature) of the temperature of the cooling water (an example of a fluid) that has undergone heat exchange with the refrigerant in the condenser 101 (heat source side heat exchanger). The second temperature is the actual measured value (actual temperature) of the temperature of the chilled water (an example of a fluid) that has undergone heat exchange with the refrigerant in the evaporator 103 (use side heat exchanger).

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

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

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

The current values recorded in database 27 are "default 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. The current values recorded in database 27 are also current values (e.g., experimental values) at 100% operating capacity that have been determined in advance through experiments, simulations, trial runs, etc. Therefore, the current value flowing through compressor main body 10 operating at 100% operating capacity is normally the current value recorded in database 27, depending on the actually measured first and second temperatures.

On the other hand, if the operating capacity falls below 100%, the current value flowing through the compressor main body 10 will also become smaller than the current value recorded in the database 27. However, the current value does not always decrease in the same manner (e.g., linearly); as described above, the decreasing trend (correlation) changes once the operating capacity reaches a predetermined value (e.g., 50%). Therefore, the detection mechanism 5 is used to determine whether the operating capacity is above or below a predetermined value, and depending on the determination result, either the first correlation or the second correlation, which indicates the tendency of different phenomena, is used. This allows the operating capacity to be determined accurately using the first correlation or the second correlation, which is used depending on the position of the slide valve 4.

In this way, the calculation device 20 determines a predetermined current value associated with the actually measured first and second temperatures, i.e., a predetermined value, based on the first and second temperatures and the database 27. Furthermore, the calculation device 20 determines whether to use the first correlation or the second correlation of the present disclosure based on the position of the slide valve 4 detected by the detection mechanism 5. The calculation device 20 then determines the operating capacity from the determined predetermined value, the actually measured value of the current flowing through the compressor main body 10, and the first correlation or the second correlation that has been determined to be used. By determining the operating capacity in this manner, the accuracy of determining the operating capacity can be improved.

In this disclosure, it is not necessary to constantly grasp the position of the slide valve 4 throughout its entire range of movement (whether it passes through any point during movement). By grasping whether it has passed a predetermined position, such as 50% operating capacity, i.e., whether the slide valve 4 is in the predetermined position, the operating capacity can be accurately determined. This allows for easy determination of the operating capacity.

The refrigeration cycle device 200 to which the screw compressor 100 of the present disclosure can be applied is not limited to a water-cooled chiller unit, but may also be, for example, an air-cooled chiller unit, a refrigerator, a showcase, an air conditioner, etc. Therefore, if the refrigeration cycle device 200 is, for example, an air-cooled chiller unit, the first temperature may be the outside air temperature. Also, if the refrigeration cycle device 200 is, for example, a refrigerator, the second temperature may be, for example, the temperature of cold air supplied to the freezer compartment. In this way, the fluid to be measured for the first and second temperatures may be either a liquid or a gas, and the liquid is not limited to water, and the gas is not limited to air.

Furthermore, the gas compressed by the screw compressor 100 is not limited to a refrigerant, but may be other gases such as air or nitrogen.

REFRIGERATION CYCLE DEVICE 20 Calculation device 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 Circumferential 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 (10)

A screw compressor used in an operating capacity range including 0% to 20% of the operating capacity,
The compressor includes a compressor body and a computing device.
The compressor body includes:
A casing;
a screw rotor that is rotationally driven within the casing;
a bypass flow path communicating from a compression chamber formed between the casing and the screw rotor to a 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 a movable range of the slide valve,
The computing device
There is a correlation between the current value flowing through the compressor body and the operating capacity of the compressor body,
the correlations include a first correlation used when the slide valve is located on one side of the predetermined position within the movable range of the slide valve, and a second correlation used when the slide valve is located on the other side ,
Whether to use the first correlation or the second correlation is determined based on the position of the slide valve detected by the detection mechanism, and an operating capacity is determined based on the value of the current flowing through the compressor body and the determined first correlation or the determined second correlation.
A screw compressor characterized by: 2. The screw compressor according to claim 1,
a position of the slide valve is controlled by hydraulic pressure, and the slide valve includes a valve body that comes into contact with 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 a chamber in which the valve body is housed,
The screw compressor, wherein the detection mechanism detects that the slide valve has passed a predetermined position by detecting a position of the piston. 3. The screw compressor according to claim 2,
The screw compressor, wherein the detection mechanism is a pressure detection mechanism installed in a communication passage that communicates the inside and outside of the chamber that accommodates the piston. 4. The screw compressor according to claim 3,
a plurality of communication passages are provided, and the pressure detection mechanism is provided for each of the communication passages;
When the slide valve is in the predetermined position,
At least one of the openings connected to each of the plurality of communication passages is disposed to be exposed to a 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 a chamber on the other side of the piston,
A screw compressor, characterized in that a plurality of the communication passages are formed. The screw compressor according to any one of claims 1 to 4,
The screw compressor, wherein the predetermined position is a position where a tendency of the correlation changes. The screw compressor according to any one of claims 1 to 4,
the first correlation is a correlation in which the current value increases with a first tendency as the operating capacity increases,
the second correlation is a correlation in which the current value increases with a second trend different from the first trend as the operating capacity increases. The screw compressor according to any one of claims 1 to 4,
the calculation device corrects the correlation based on a preset value of the current value determined from the correlation when the operating capacity is a predetermined capacity and an actual measured value of the current value when the operating capacity is the predetermined capacity. 8. The screw compressor according to claim 7,
The screw compressor, wherein the arithmetic unit notifies an alarm device when a difference between the preset value and the actual measured value exceeds a predetermined threshold. The compressor includes a screw compressor, a condenser, an expansion mechanism, and an evaporator.
The screw compressor is used in an operating capacity range including 0% to 20% and includes a compressor body and a computing device;
The compressor body includes:
A casing;
a screw rotor that is rotationally driven within the casing;
a bypass flow path communicating from a compression chamber formed between the casing and the screw rotor to a 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 a movable range of the slide valve,
The computing device
There is a correlation between the current value flowing through the compressor body and the operating capacity of the compressor body,
the correlations include a first correlation used when the slide valve is located on one side of the predetermined position within the movable range of the slide valve, and a second correlation used when the slide valve is located on the other side ,
Whether to use the first correlation or the second correlation is determined based on the position of the slide valve detected by the detection mechanism, and an operating capacity is determined based on the value of the current flowing through the compressor body and the determined first correlation or the determined second correlation.
A refrigeration cycle device characterized by: The system includes a screw compressor, a condenser, an expansion mechanism, and an evaporator, and a refrigerant circulates between a heat source side heat exchanger, which is one of the heat exchangers of the condenser or the evaporator, and a user side heat exchanger, which is the other heat exchanger.
The screw compressor includes a compressor body and a computing device,
The compressor body includes:
A casing;
a screw rotor that is rotationally driven within the casing;
a bypass flow path communicating from a compression chamber formed between the casing and the screw rotor to a 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 a movable range of the slide valve,
The computing device
There is a correlation between the current value flowing through the compressor body and the operating capacity of the compressor body,
the correlations include a first correlation used when the slide valve is located on one side of the predetermined position within the movable range of the slide valve, and a second correlation used when the slide valve is located on the other side,
a database that records predetermined values of the current value associated with a first temperature that is an actual measurement value of the temperature of a fluid that has undergone heat exchange with the refrigerant in the heat source side heat exchanger and a second temperature that is an actual measurement value of the temperature of a fluid that has undergone heat exchange with the refrigerant in the user side heat exchanger;
determining the predetermined value from the first temperature, the second temperature and the database;
determining whether to use the first correlation or the second correlation based on the position of the slide valve detected by the detection mechanism;
the operating capacity is determined from the determined preset value and the first correlation or the second correlation determined between an actual measurement value of a current flowing through the compressor body.