WO2004036045A1

WO2004036045A1 - Variable inner volume ratio-type inverter screw compressor

Info

Publication number: WO2004036045A1
Application number: PCT/JP2003/013117
Authority: WO
Inventors: Nozomi Gotou; Kaname Ohtsuka
Original assignee: Daikin Industries, Ltd.
Priority date: 2002-10-16
Filing date: 2003-10-14
Publication date: 2004-04-29
Also published as: EP1553300B1; EP1553300A1; JP4147891B2; TWI230761B; EP1553300A4; AU2003271184A1; US20060039805A1; JP2004137934A; CN100406738C; TW200412397A; ES2503716T3; CN1705826A

Abstract

Regulating compression capability to a load is performed by a inverter (15) that regulates the revolution number of an electric motor (11). This makes unload control in the capability regulation unnecessary, preventing operational efficiency from lowering. Further, a capacity control valve for capacity control is eliminated for a simplified valve controlling mechanism. Regulating a variable inner volume ratio achieves the highest compressor efficiency corresponding to operating condition (capability). When a low inner volume ratio command is issued, a slide valve (19) is moved by a compression portion controller (27) in an axial direction toward the electric motor (11). This advances the completion time of a compression step to advance the discharge of a compressed gas. When a high inner volume ratio command is issued, the slide valve (19) is moved in an axial direction toward a piston (25), which delays the time of completion of the compression step to delay the discharge of a compression gas.

Description

Description Variable Internal Volume Ratio Type Inverter Cry Compressor Technical Field

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable internal volume ratio type inverter task compressor in which an internal volume ratio which is a ratio between a suction volume and a discharge volume of a screw compressor is made variable. Background art

Conventionally, there is a variable internal volume ratio type screw-type compressor in which the internal volume ratio is made variable as shown in FIG. 7 (for example, see Japanese Patent No. 3159762).

In the variable internal volume ratio type screw compressor, when it is necessary to change the internal volume ratio, the rod 2 is rotated by the step motor 1 to retreat the variable VI valve 3, for example. At that time, the displacement control valve 4 retreats with the retraction of the variable VI valve 3, and when the variable VI valve 3 is fixed to a new set position, it is fixed again in contact with the variable VI valve 3. . In this way, the tip of the displacement control valve 4 retreats to a position corresponding to the changed internal volume ratio, and newly defines the opening degree of the discharge port 5.

In this case, the internal volume ratio is determined by detecting the pressure P _dl immediately before the space formed by the rotor and the inner wall of the casing 7 communicates with the discharge space during operation, and calculating the difference between the detected pressure P _dl and the discharge pressure. Specified by giving a signal to step motor 1 to minimize ΔP. Alternatively, the optimal internal volume ratio is predicted by performing a trend analysis of parameters such as the suction pressure and the discharge pressure during operation with the control device 10, and a signal representing the value of the optimal internal volume ratio is given to the step motor 1. Specified by In the above configuration, the fluid sucked from the suction hole 6 is compressed by the female rotor (not shown) in the casing 7 and then discharged to the discharge hole 8 through the discharge port 5.

In this state, the load on the variable internal volume ratio type screw compressor fluctuates, When control becomes necessary, the hydraulic piston 9 moves forward based on the control command to advance the capacity control valve 4 by the required amount, so that the variable VI valve 3 and the capacity control valve 4 Creates a gap. Then, the fluid in the middle of compression is bypassed in a suction manner from the gap between the variable VI valve 3 and the capacity control valve 4.

That is, in the above-mentioned Patent No. 31599762, the full load capacity (10 0

The internal volume ratio of the compressed gas discharged from the displacement control valve 4 is made variable so as to achieve the highest compressor efficiency in accordance with the high and low pressure conditions during operation at 0% load).

However, the variable internal volume ratio type screw-type compressor disclosed in the above-mentioned conventional Japanese Patent No. 3159762 has the following problems.

In other words, the variable internal volume ratio technology in the above-mentioned conventional variable internal volume ratio type screw-type compressor uses the compressed gas discharged from the discharge port 5 so that the maximum compressor efficiency is obtained in accordance with the high and low pressure conditions during operation. Although the internal volume ratio is variable, it is set to match the full load capacity (100% load). At the time of partial load capacity (part load), capacity adjustment (unload control) is performed by bypassing the fluid during compression from the gap between the variable VI valve 3 and the capacity control valve 4 to the suction side. There is a problem that the efficiency is low because of this.

In addition, since it has a variable VI valve 3 that changes the internal volume ratio and a capacity control valve 4 that performs capacity control, the variable VI valve 3 control mechanism when the internal volume ratio changes and the capacity control valve 4 control when the capacity is controlled There is a problem that the valve control mechanism must be provided separately and the valve control mechanism is complicated. Disclosure of the invention

Therefore, an object of the present invention is to provide a variable internal volume ratio type screw-type compressor capable of always operating at maximum efficiency according to the load (operating condition).

In order to achieve the above object, a variable internal volume ratio type inverter task compressor of the present invention has a variable internal volume in which the internal volume ratio is made variable by changing the end point of the compression process in the screw compression section. A ratio valve, a motor for driving the screw compression section in rotation, and an inverter for controlling the rotation frequency of the motor in accordance with the load. It is characterized by having.

According to the above configuration, when adjusting the compression capacity according to the load, the rotation frequency of the electric motor is controlled by the inverter. Thus, the capacity adjustment is performed without performing the unload control. Then, the opening of the variable internal volume ratio valve is controlled so that the maximum compressor efficiency according to the adjusted rotation frequency of the electric motor is obtained, and the end point of the compression process in the screw compression unit is set. . As a result, maximum efficiency operation is always possible according to the load.

Further, the variable internal volume ratio type inverter screw compressor according to the present invention is characterized in that the opening degree of the variable internal volume ratio valve is determined based on the suction side pressure and the discharge side pressure in the screw compression section and the rotation frequency of the electric motor. It is characterized by having a control unit for controlling

According to the above configuration, at the time of the variable internal volume ratio, the opening of the variable internal volume ratio valve is controlled by the control unit based on the suction side pressure and the discharge side pressure in the screw compression unit and the rotation frequency of the electric motor. Is controlled. Therefore, by using a predetermined relationship between the compression ratio, the rotation frequency of the motor, and the optimum internal volume ratio, the internal volume ratio is adjusted according to the rotation frequency of the motor adjusted by the inverter. It is controlled accurately and easily to achieve the highest compressor efficiency. BRIEF DESCRIPTION OF THE FIGURES

FIGS. 1A and 1B are main part configuration diagrams of a variable internal volume ratio type inverter task compressor of the present invention.

FIG. 2 is a diagram showing a capacity-internal volume ratio control system in the variable internal volume ratio type Inverter Task Compressor shown in FIG.

FIG. 3 is a diagram showing a capacity / internal volume ratio control system different from FIG.

FIG. 4 is a diagram showing the relationship between the compression ratio and the optimum internal volume ratio for each operating frequency. FIG. 5 is a diagram showing the relationship between the refrigeration capacity and the compressor efficiency for each compression ratio.

FIGS. 6A and 6B are diagrams showing the relationship between the internal volume and the pressure in the screw compressor.

FIG. 7 is a cross-sectional view of a conventional variable internal volume ratio type screw-type compressor. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments. FIG. 1 is a schematic configuration diagram of a variable internal volume ratio type impeller task compressor of the present embodiment. 1A shows a low internal volume ratio, and FIG. 1B shows a high internal volume ratio.

In FIG. 1, reference numeral 11 denotes an electric motor, which includes a stator 12 fixed to a casing (not shown) and a rotor 13 fixed to one end of a main shaft 14 and rotating. The motor 11 is inverter-driven by an inverter 15. Both ends of the main shaft 14 are supported by bearings 16 and 17, and a screw rotor 18 is attached to the other end of the main shaft 14. Then, when the main shaft 14 is rotated by the electric motor 11, the screw rotor 18 is rotated, and the suction gas is compressed by a screw groove (not shown) on the outer peripheral surface. It has a discharge port 20 of a predetermined length in the axial direction, and a cylindrical slide valve 19 facing the outer peripheral surface of the screw rotor 18. The gas compressed by the screw rotor 18 is supplied to the discharge port 2. Discharged from 0. One end of a plurality of rods 22 slidably supported by a support plate 21 is attached to an end surface of the slide valve 19 on the side opposite to the electric motor 11. The other end of each rod 22 is attached to one connecting plate 23. A cylinder 24 is provided at the center of the surface of the support plate 21 on the anti-screw rotor 18 side, and a biston rod 26 attached to the anti-screw rotor 18 side of the biston 25 stored in the cylinder 24 The connecting plate 23 is attached to the tip of the. Thus, as the biston 25 moves in the axial direction, the slide valve 19 moves in the axial direction via the piston rod 26, the connecting plate 23, and the port 22.

The working fluid supplied to and discharged from the working chambers on both sides of the piston 25 in the cylinder 24 is controlled by the fluid control device 28 based on a control signal from the compression section controller 27. The specific configuration of the fluid control device 28 is such that when the internal volume ratio is reduced, the piston 25 is moved toward the screw rotor 18 as shown in FIG. In the case of raising, it is particularly limited as long as the configuration is such that the biston 25 is moved to the side opposite to the screw rotor 18 as shown in FIG. 1B. It is not specified.

In the variable internal volume ratio type inverter screw compressor having the above configuration, the capacity adjustment for the load is performed by controlling the number of revolutions of the electric motor 11 by the inverter 15. By doing so, there is no need to perform unload control at the time of capacity adjustment, and a decrease in operating efficiency can be suppressed. Furthermore, the capacity control valve for controlling the capacity can be eliminated, and the valve control mechanism can be simplified.

On the other hand, the position of the slide valve 19 is controlled by the compression section controller 27 so that the above-mentioned variable internal volume ratio has the highest efficiency according to the operation state. At the time of the low internal volume ratio command, the slide valve 19 (that is, the start position of the discharge port 20) is moved to the axial motor 11 side, so that the end point of the compression process in the compression section is accelerated. Discharge gas quickly. On the other hand, at the time of the high internal volume ratio command, the slide valve 19 (that is, the start position of the discharge port 20) is moved to the axial piston 25 side to delay the end of the compression process in the compression section and perform compression. The gas is discharged late. That is, in the present embodiment, the variable internal volume ratio valve is configured by the slide valve 19.

As described above, when the rotation speed of the electric motor 11 is set by the inverter 15 and the position of the slide valve 19 is set by the compression unit controller 27, the suction gas sucked from the suction port is Then, it passes through the motor 11 and is guided to the screw port 18. Then, the fluid is compressed by the screw groove formed on the outer peripheral surface of the screw rotor 18 and is discharged from the discharge port 20 of the slide valve 19.

Hereinafter, the rotation speed control of the electric motor 11 and the position control of the slide valve 19 in the present embodiment will be described.

FIG. 2 is a diagram illustrating a capacity / internal volume ratio control system in the variable internal volume ratio type Inverter Task compressor. In FIG. 2, a screw compressor 31 mounted on a refrigerator to compress and heat a refrigerant will be described as an example.

The refrigerator includes a screw compressor 31, a condenser 32, an expansion valve 33, and an evaporator 34, which are sequentially connected in a ring shape. The high-temperature and high-pressure refrigerant discharged from the screw compressor 31 is subjected to heat exchange with cooling water or air in the condenser 32. It is condensed and supplied to the expansion valve 33 as a low-temperature and high-pressure liquid refrigerant. Then, the low-temperature and low-pressure liquid refrigerant decompressed by the expansion valve 33 evaporates by heat exchange with water in the evaporator 34 and returns to the screw compressor 31 as a low-pressure gas. Then, the cold water cooled by the evaporator 34 is used for cooling.

A temperature sensor 35 is attached to the refrigerant pipe of the evaporator 34.

A detection signal representing the cooling water temperature Tw of 35 is input to the rotation speed output unit 37 of the control device 36. Then, the rotation speed output unit 37 uses the cooling water temperature Tw based on the input detection signal as information on the load side, for example, based on the difference from the set temperature, for the motor 11 for obtaining the required refrigerating capacity. The rotation frequency Hz is calculated and output to the optimum internal volume ratio output section 38 and the inverter 15 of the control device 36. The inverter 15 controls the rotation speed of the electric motor 11 based on the rotation frequency Hz received above. In this way, the capacity is adjusted for the load.

On the other hand, a low pressure side pressure sensor 40 is mounted on the suction side of the screw compression section 39 including the screw rotor 18 and the slide valve 19, and a high pressure side pressure sensor 41 is mounted on the discharge side. Then, a detection signal indicating the low pressure LP from the low pressure side pressure sensor 40 and a detection signal indicating the high pressure HP from the high pressure side pressure sensor 41 are input to the optimum internal volume ratio output unit 38. Then, the optimum internal volume ratio output unit 38 detects the operation status after setting the rotation speed of the motor 11 based on the low pressure LP on the suction side and the high pressure HP on the discharge side based on the input detection signal. You. Then, a calculation process is performed based on the low pressure LP, the high pressure HP, and the rotation frequency Hz from the rotation speed output unit 37, and an optimum internal volume ratio at the current rotation frequency Hz is calculated. Output. Then, the compression unit controller 27 controls the operation of the fluid control device 28 based on the received internal volume ratio. Thus, the internal volume ratio control according to the operating condition is performed.

By the way, when the configuration of the fluid control device 28 includes an element (such as an external drive motor for operating a pilot valve) that performs an operation proportional to the axial movement of the slide valve 19, Can detect the position of the slide valve 19 based on the operation position of the above element. In this case, the detection signal indicating the position SV of the slide valve 19 from the fluid control device 28 is transmitted to the optimal internal volume ratio via the compression unit controller 27 or directly. Input to output section 38. Then, the optimum internal volume ratio output section 38 obtains the current internal volume ratio value based on the received position SV of the slide valve 19, and performs feedback control of the optimum internal volume ratio. By doing so, variable internal volume ratio control can be performed with high accuracy.

When the configuration of the fluid control device 28 is a configuration that cannot detect the position of the slide valve 19 (for example, a configuration including a pipe and a solenoid valve), the optimal internal volume ratio output unit 38 is The output internal volume ratio value from the start is integrated. Then, feedback control can be performed by calculating the control amount ΔνI to the optimum internal volume ratio value using the integrated 內 partial volume ratio value as the current internal volume ratio value.

FIG. 3 is a diagram showing a capacity / internal volume ratio control system different from FIG. In FIG. 3, the screw compressor 31 is also mounted on the refrigerator. The control device 51 and the inverter 54 have different configurations from those in FIG. Hereinafter, the same members as those in FIG. 2 are denoted by the same reference numerals, and the operation of the control device 51 and the inverter 54 will be mainly described.

As in the case of FIG. 2, the detection signal indicating the cooling water temperature from the temperature sensor 35 is input to the rotation speed output unit 52 of the control device 51. In addition, the detection signal indicating the low pressure LP from the low pressure side pressure sensor 40 and the detection signal indicating the high pressure HP from the high pressure side pressure sensor 41 are output to the optimum internal volume ratio output section 53 of the controller 51. Is entered. Then, the rotation frequency output section 52 calculates the rotation frequency Hz of the motor 11 for obtaining the required refrigerating capacity based on the cooling water temperature Tw, and the inverter 54 controls the rotation number of the motor 11. . Thus, the capacity adjustment for the load is performed. The inverter 54 in the present embodiment is capable of detecting the drive voltage V and the drive current A (or the drive power W) of the motor 11, and detects the detected drive voltage V and drive current A. Or the drive power W) is returned to the rotation speed output unit 52. Then, the rotation frequency output unit 52 converts the calculated rotation frequency Hz and the received drive voltage V and drive current A (or the drive power W) into the optimum internal volume ratio output unit 53. Sent out.

Then, the optimum internal volume ratio output section 53 is connected to the low pressure LP and high pressure HP from the pressure sensors 40 and 41 and the rotation from the rotation speed output section 52, as in the case of FIG. Calculation processing is performed based on the rotation frequency Hz and the position SV of the slide valve 19 from the fluid control device 28 to calculate the control amount ΔVI to the optimal internal volume ratio, and the compression controller 27 Output to

Further, in the present embodiment, the change in the drive voltage V and the drive current A (or drive power W) from the rotation speed output unit 52 is stored by the optimum external volume ratio output unit 53. Then, while repeating the above-described internal volume ratio operation, the internal volume ratio control is performed so that the drive voltage V and the drive current A or the drive power W) are minimized.

Thereafter, as in the case of FIG. 2, the operation of the fluid control device 28 is controlled by the compression unit controller 27 based on the received control amount ΔVI, and the internal volume ratio according to the operating condition is reduced. Feedback controlled.

In this case, as in the case of FIG. 2, if the configuration of the fluid control device 28 cannot detect the position of the slide valve 19, the optimum internal volume ratio output section 53 is The control amount ΔVI of the optimum internal volume ratio value is calculated using the integrated internal volume ratio value obtained by integrating the output internal volume ratio values from the time of startup as the current internal volume ratio value.

By the way, in the optimum internal volume ratio output sections 38, 53 of the control devices 36, 51 shown in FIGS. 2 and 3, arithmetic processing is performed to calculate the control amount AVI to the optimum internal volume ratio. I have to. Low pressure LP from the low pressure side pressure sensor 40, high pressure HP from the high pressure side pressure sensor 41, and rotation frequency output section 37, 52 And are sequentially stored in the memory. Then, the low pressure LP, the high pressure HP, and the rotation frequency Hz are compared with the low pressure LP, the high pressure HP, and the rotation frequency Hz during the previous operation of the internal volume ratio. It is also possible to obtain the control amount Δν I for

FIG. 4 shows the compression ratio represented by the ratio (Η Ρ / L Ρ) between the high pressure Η から from the high pressure side pressure sensor 41 and the low pressure L から from the low pressure side pressure sensor 40, and the optimal internal volume ratio. The following shows the relationship for each operating frequency Hz (= 3 O Hz, 6 O Hz, 9 O Hz). The straight line in FIG. 4 is a theoretical value represented by VI = (HP / LP) ^{1 / k} (k: refrigerant specific heat ratio). The relationship between the compression ratio, the optimal internal volume ratio, and the operating frequency Hz is determined for each refrigerant, and the arithmetic expression for performing the arithmetic processing by the optimal internal volume ratio output units 38, 53 shown in FIGS. 2 and 3 is used. Incorporate the above relationship into

By doing so, the control amount ΔνI to the optimal internal volume ratio at the current rotation frequency Hz can be accurately calculated by the arithmetic processing by the optimal internal volume ratio output sections 38, 53.

As described above, in the present embodiment, the electric motor 1 in the screw compressor is used.

1 is driven by an inverter by an inverter 15. Further, the axial position of the slide valve 19 that defines the discharge start position is supplied to and discharged from the working chamber in the cylinder 24 by the fluid control device 28 based on a control signal from the compression unit controller 27. Control by controlling the working fluid.

Then, the capacity adjustment for the load is performed by the rotation frequency output units 37, 52 constituting the control devices 36, 51, by the rotation frequency for obtaining the refrigerating capacity that requires the cooling water temperature T as information on the load side. Hz is calculated, and the inverters 15 and 54 control the rotation speed of the electric motor 11 so as to be at this rotation frequency Hz. Therefore, it is possible to eliminate the necessity of the unload control at the time of capacity adjustment, and to suppress a decrease in operation efficiency. Furthermore, the valve control mechanism can be simplified by eliminating the capacity control valve for performing the capacity control.

Further, the above-mentioned variable internal volume ratio is adjusted by the optimum internal volume ratio output sections 38, 53 of the control devices 36, 51 to the low pressure LP on the suction side, the high pressure HP on the discharge side, and the rotational frequency Hz. Calculate the optimum internal volume ratio (or Δ VI) at the current rotation frequency Hz based on the above formula, and calculate the axial position of the slide valve 19 by the compression unit controller 27 and the fluid control device 28. This is done by setting and defining the start position of the ejection. Therefore, the internal volume ratio can be set so that the highest compressor efficiency according to the rotation frequency Hz of the motor 11 is obtained.

Therefore, according to the present embodiment, it is possible to minimize a decrease in compressor efficiency when controlling the rotation frequency Hz of the starry compressor 31 in order to adjust the capacity with respect to the load.

Figure 5 shows the relationship between refrigeration capacity and compressor efficiency. The horizontal axis shows the refrigerating capacity Q, expressed as a percentage with the refrigerating capacity at 60 Hz in a variable internal volume ratio type screw compressor using both the conventional variable internal volume ratio and unload control as 100%. hand I have. On the other hand, the vertical axis shows compressor efficiency. Further, the compression ratio is changed to 2.1, 3.9, 5.5, 7.9.

According to the figure, in the case of the variable internal volume ratio type inverter task-type compressor using the variable internal volume ratio and inverter control in this embodiment in combination, a conventional variable internal volume ratio and unload control are used together. Compared to the variable internal volume ratio type screw compressor, the compressor efficiency can be increased at any compression ratio at a refrigerating capacity Q of 100% or less. Of course, the lower the refrigerating capacity, the greater the compressor efficiency can be increased, and a greater effect can be obtained. Also, in the case of the variable internal volume ratio type inverter task compressor, capacity adjustment with respect to load is performed by inverter control. Therefore, the ability adjustment of 100% or more can be performed. In the case of a conventional screw compressor in which the capacity adjustment for the load is performed by the unload control, the capacity adjustment of 100% or more cannot be performed naturally.

By the way, in the case of a screw compressor, even under the same pressure condition, there is a difference in the internal pressure depending on the rotation frequency, so that there is an optimum internal volume ratio value corresponding to each frequency. Figure 6 shows the relationship between the internal volume and the pressure at a frequency of 30 Hz (Figure 6A) and at a frequency of 90 Hz (Figure 6B). The dotted line in the figure is a curve showing the relationship between the internal volume and the pressure when the internal volume ratio is fixed to the optimum internal volume ratio at a frequency of 60 Hz. The one-point line is a curve showing the relationship between the internal volume and the pressure during theoretical adiabatic compression. In the above fixed internal volume ratio, when the frequency is 30 Hz, insufficient compression occurs at the time (A), and the pressure decreases rapidly. When the frequency is 90 Hz, overcompression occurs at the point (B), and the pressure is much higher than the theoretical value. From the above, it is not possible to simply apply an inverter to the capacity control of a screw compressor.

However, as shown in the present embodiment, by using a variable internal volume ratio, as shown by the solid line, compression insufficiency that occurred at a frequency of 30 Hz at a fixed internal volume ratio is eliminated, and pressure fluctuations are reduced. The width can be reduced. In addition, when the frequency is 90 Hz at the time of the fixed volume ratio, the width of the pressure fluctuation can be reduced by eliminating the over-compression that has occurred. In the above-described embodiment, the description of the capacity / internal volume ratio control system in the variable internal volume ratio type impeller screw compressor is applied to a refrigerator as an example. It is not limited to this. In short, in FIGS. 2 and 3, the detection signals input to the rotation speed output units 37 and 52 of the control devices 36 and 51 only need to be signals indicating the state of the load.

Claims

The scope of the claims

1. A variable internal volume ratio valve (19) that changes the internal volume ratio by changing the end point of the compression process in the screw compression section (39);

An electric motor (11) that rotationally drives the screw compression section (39);

A variable internal volume ratio type inverter task compressor comprising an inverter (15) for controlling a rotation frequency of the electric motor (11) according to a load.

2. The variable internal volume ratio type inverter task compressor according to claim 1, wherein a suction side pressure and a discharge side pressure in the screw compression unit (39) and a rotation frequency of the motor (11) are used. And a controller (36, 51, 27, 28) for controlling the opening of the variable internal volume ratio valve (19).