JP6317888B2 - Vapor compression refrigeration system - Google Patents

Description

  The present invention relates to a vapor compression refrigeration apparatus for cooling an electric heating element such as a computer.

  For example, in the invention described in Patent Document 1, switching control is performed between a case where a gas phase refrigerant is injected into a compression process and a case where a liquid phase refrigerant is injected into a compression process based on the refrigerant temperature discharged from the compressor. ing. Note that “injecting” refrigerant in the compression process is also referred to as “injection”.

JP-A-5-302760

  In Patent Document 1, an increase in the discharge temperature of the compression device is suppressed by injecting a liquid phase refrigerant into the compression process. However, it is necessary to separate the refrigerant to be injected into a gas phase refrigerant and a liquid phase refrigerant. Therefore, since a gas-liquid separator is required, the number of parts of the vapor compression refrigerator is increased.

  An object of this invention is to provide the vapor compression refrigerator which can suppress the increase in a number of parts, and can suppress the raise of discharge temperature in view of the said point.

  In order to achieve the above object, the present invention provides a high-pressure heat exchanger (3) for cooling a high-pressure refrigerant and a high-pressure heat exchanger (3) in a vapor compression refrigeration system that moves low-temperature heat to a high-temperature side. ), A low pressure heat exchanger (7) for depressurizing the low pressure refrigerant depressurized by the first decompression device (5), A compression device that compresses the refrigerant and discharges the refrigerant to the high-pressure heat exchanger (3) side, and includes a compression device (9) into which a refrigerant in a gas-liquid two-phase state is injected in a compression process.

  Hereinafter, the gas-liquid two-phase refrigerant injected in the compression process is referred to as an injection refrigerant. The compression process before the injected refrigerant is injected is called a first compression process. The compression process after the injected refrigerant is injected is called a second compression process.

  And in this invention, a liquid phase refrigerant | coolant can be inject | poured in a compression process, without providing a gas-liquid separator etc. The refrigerant whose temperature has been increased by being compressed in the first compression process is cooled by the injected liquid-phase refrigerant.

  For this reason, it can suppress that the temperature of the refrigerant | coolant discharged from a compression apparatus (9) passes through a 2nd compression process. Therefore, when a large refrigerating capacity is required, such as in summer when the outside air temperature is high, even when the discharge pressure of the compression device (9) is increased, it is possible to suppress the discharge temperature from significantly increasing.

  Further, since the gas-phase refrigerant is injected together with the liquid-phase refrigerant in the compression process, the efficiency of the vapor compression refrigerator can be improved as in the so-called “gas injection refrigerator”. That is, according to the present invention, the vapor compression refrigerator can be efficiently operated even when a large refrigeration capacity is required while suppressing an increase in the number of parts and an increase in discharge temperature.

  Incidentally, the reference numerals in parentheses for each of the above means are examples showing the correspondence with the specific means described in the embodiments described later, and the present invention is indicated by the reference numerals in the parentheses of the above respective means. It is not limited to specific means.

It is a mimetic diagram of a vapor compression refrigeration machine concerning a 1st embodiment of the present invention. It is a ph diagram which shows the action | operation of the vapor compression refrigerator which concerns on this invention. It is a schematic diagram of the vapor compression refrigerator which concerns on 2nd Embodiment of this invention. It is a schematic diagram of the vapor compression refrigerator which concerns on 3rd Embodiment of this invention. It is a control system block diagram of the vapor compression refrigeration machine concerning a 3rd embodiment of the present invention. It is a control flowchart of the vapor compression refrigerator which concerns on 3rd Embodiment of this invention. It is a schematic diagram of the vapor compression refrigerator which concerns on 4th Embodiment of this invention. It is a control flowchart of the vapor compression refrigerator which concerns on 4th Embodiment of this invention.

  The “embodiment of the invention” described below shows an example of the embodiment. In other words, the invention specific items described in the claims are not limited to the specific means and structures shown in the following embodiments.

  In the present embodiment, the present invention is applied to a vapor compression refrigerator that is operated at a high pressure side pressure lower than the critical pressure of the refrigerant. The vapor compression refrigerator cools indoor air indirectly by indirectly cooling an electric heating element such as a computer.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. It should be noted that at least one member or part described with at least a reference numeral is provided, except for cases where “plural”, “two or more” and the like are omitted.

(First embodiment)
1. Configuration of Vapor Compression Refrigerator etc. As shown in FIG. 1, the vapor compression refrigerator 1 according to the present embodiment includes a high pressure heat exchanger 3, a first pressure reduction device 5, a low pressure heat exchanger 7, a compression device 9, and the like. It has. The high-pressure heat exchanger 3 cools the high-pressure refrigerant (hereinafter also referred to as discharge refrigerant) discharged from the compression device 9.

  That is, the high-pressure heat exchanger 3 cools the discharged refrigerant by exchanging heat between the outdoor air and the discharged refrigerant. In the present embodiment, as shown in a ph diagram (also referred to as a Mollier diagram) shown in FIG. 2, the pressure of the discharged refrigerant is smaller than the critical pressure of the refrigerant. For this reason, the discharged refrigerant in the gas phase is cooled and condensed (liquefied) by the high-pressure heat exchanger 3.

  As shown in FIG. 1, the first decompression device 5 decompresses the high-pressure refrigerant cooled by the high-pressure heat exchanger 3. Normally, the degree of supercooling of the refrigerant flowing out from the high-pressure heat exchanger 3 is 0 (zero) or small as shown in FIG. For this reason, the refrigerant decompressed by the first decompression device 5 is normally in a gas-liquid two-phase state.

  In the low pressure heat exchanger 7, the low pressure liquid phase refrigerant decompressed by the first decompression device 5 is evaporated. That is, in the low-pressure heat exchanger 7, the air supplied to the room and the refrigerant decompressed by the first decompression device 5 are subjected to heat exchange, thereby mainly evaporating (vaporizing) the liquid-phase refrigerant and Cooling.

  The compression device 9 compresses the low-pressure refrigerant and discharges it to the high-pressure heat exchanger 3 side. As shown in FIG. 1, the compression device 9 includes a first compression device 9A and a second compression device 9B. The first compressor 9 </ b> A sucks and compresses the gas phase refrigerant out of the refrigerant flowing out of the low pressure heat exchanger 7. For this reason, a gas-liquid separator 11 is provided on the suction side of the first compression device 9A.

  The gas-liquid separator 11 separates the refrigerant flowing out from the low-pressure heat exchanger 7 into a gas phase refrigerant and a liquid phase refrigerant, and stores the separated liquid phase refrigerant. For this reason, when the required refrigeration capacity (also referred to as a refrigerant load) is small, surplus refrigerant is stored in the gas-liquid separator 11 as a liquid phase refrigerant. When the cooling load increases, the liquid-phase refrigerant stored in the gas-liquid separator 11 evaporates, increasing the amount of refrigerant circulating in the vapor compression refrigerator 1 and increasing the refrigerating capacity.

  The second compressor 9B sucks and compresses the refrigerant discharged from the first compressor 9A and the refrigerant decompressed by the second decompressor 13. Then, the refrigerant discharged from the second compression device 9B flows into the high-pressure heat exchanger 3 as the discharge refrigerant.

  The second compression device 9B is constituted by a fixed capacity type compressor driven by an electric motor (not shown). The fixed capacity method refers to a compressor having a constant theoretical discharge amount that is discharged when the compressor rotates once. For this reason, the theoretical discharge amount discharged per unit time is proportional to the rotation speed of the electric motor, that is, the second compression device 9B.

  The second compressor controller 15 controls the rotation speed of the second compressor 9B, that is, the electric motor. The second compression device controller 15 is constituted by a microcomputer having a CPU, a ROM, a ROM, and the like. Then, the second compressor control unit 15, that is, the CPU executes control according to a program stored in advance in a nonvolatile storage unit such as a ROM.

  The pressure detector 15A detects the pressure of the refrigerant flowing into the high-pressure heat exchanger 3, that is, the discharge refrigerant. Then, the second compressor controller 15 controls the operation of the second compressor 9B based on the pressure detected by the pressure detector 15A.

  That is, the second compressor control unit 15 performs the second compression per unit time so that the discharge pressure of the second compressor 9B, that is, the pressure detected by the pressure detector 15A is equal to or lower than a predetermined pressure set in advance. The theoretical discharge amount discharged from the compression device 9B is variably controlled.

  In addition, “variably controlling the theoretical discharge amount discharged from the second compression device 9B per unit time so that the discharge pressure of the second compression device 9B is equal to or lower than a predetermined pressure” specifically refers to, for example, Is as follows.

  When the discharge pressure of the second compression device 9B exceeds the predetermined pressure, the second compression device controller 15 reduces the current rotation speed of the second compression device 9B by a preset rotation speed ΔN. Thereafter, the discharge pressure of the second compression device 9B is detected again.

  At this time, when the discharge pressure of the second compression device 9B becomes equal to or lower than the predetermined pressure, the second compression device controller 15 maintains the changed rotation speed. When the discharge pressure of the second compressor 9B exceeds the predetermined pressure, the second compressor controller 15 again reduces the current rotational speed of the second compressor 9B by the rotational speed ΔN again. The discharge pressure of the second compression device 9B is detected again.

  And when the discharge pressure of the 2nd compression apparatus 9B becomes below predetermined pressure, the control part 15 for 2nd compression apparatuses maintains the rotation speed after a change. When the discharge pressure of the second compressor 9B exceeds the predetermined pressure, the second compressor controller 15 further reduces the current rotational speed of the second compressor 9B by the rotational speed ΔN. The discharge pressure of the second compression device 9B is detected again.

In this way, the second compressor controller 15 continues to decrease the rotational speed of the second compressor 9B by the rotational speed ΔN until the discharge pressure of the second compressor 9B becomes equal to or lower than the predetermined pressure.
The second decompression device 13 decompresses the high-pressure refrigerant cooled by the high-pressure heat exchanger 3 to a pressure higher than the pressure of the refrigerant decompressed by the first decompression device 5. As described above, the degree of supercooling of the refrigerant flowing out from the high-pressure heat exchanger 3 is 0 (zero) or small.

  For this reason, the refrigerant decompressed by the second decompression device 13 is also in a gas-liquid two-phase state, like the refrigerant decompressed by the first decompression device 5. That is, the gas-liquid two-phase refrigerant is injected into the compressor 9 during the compression process.

  The second decompression device 13 includes a variable throttle device (not shown), a discharge refrigerant temperature detector 13A, a second decompression device controller 13B, and the like. The variable throttle device has an electric actuator (not shown) that changes and adjusts the throttle opening. The discharge refrigerant temperature detector 13A detects the temperature of the refrigerant flowing into the high-pressure heat exchanger 3, that is, the discharge refrigerant.

  Based on the temperature detected by the discharged refrigerant temperature detector 13A, the second pressure reducing device control unit 13B controls the operation of the variable throttle device, that is, the actuator to change the throttle opening of the second pressure reducing device 13. .

  That is, the second pressure reducing device controller 13B depressurizes the refrigerant to a pressure at which the temperature of the refrigerant flowing into the high-pressure heat exchanger 3, that is, the detected temperature of the discharged refrigerant temperature detector 13A is equal to or lower than a predetermined temperature set in advance. To do. The “predetermined temperature” is a temperature that is appropriately determined based on the heat-resistant temperature on the high-pressure side of the vapor compression refrigerator 1 or the like.

  The first decompression device 5 has the same configuration as the second decompression device 13. That is, the second decompression device 13 includes a variable throttle device (not shown), a heating degree detector 5A, a first decompression device controller 5B, and the like.

  The variable throttle device has an electric actuator (not shown) that changes and adjusts the throttle opening. The heating degree detector 5 </ b> A detects the temperature of the refrigerant flowing out from the low pressure heat exchanger 7. Based on the temperature detected by the heating degree detector 5A, the first decompression device control unit 5B has a preset heating degree of the refrigerant flowing out of the low pressure heat exchanger 7 and a value that is 0 or more. The throttle opening degree of the first pressure reducing device 5 is controlled so as to be a value of.

  Both the first decompression device control unit 5B and the second decompression device control unit 13B are constituted by a microcomputer having a CPU, a ROM, a ROM, and the like. And both control part 5B, 13B performs control according to the program previously memorize | stored in non-volatile memory | storage parts, such as ROM.

2. Features of the Vapor Compression Refrigerating Machine According to this Embodiment In this embodiment, as shown in FIG. 1, the gas-liquid two-phase refrigerant decompressed by the second decompression device 13 passes through a gas-liquid separator or the like. Without being injected into the compression device 9 in the compression process. For this reason, the refrigerant whose temperature has been increased due to the compression in the first compression process by the first compression device 9A is cooled by evaporating the injected liquid-phase refrigerant.

  The gas-phase refrigerant discharged from the first compressor 9A, the injected gas-phase refrigerant and the refrigerant evaporated and vaporized by the injection are sucked into the second compressor 9B and discharged to the high-pressure heat exchanger 3 side. The

  For this reason, as shown in part A of FIG. 2, the degree of heating of the gas-phase refrigerant sucked into the second compression device 9B becomes small, so that the temperature of the refrigerant discharged from the compression device 9 through the second compression process Can be prevented from significantly rising. Therefore, when a large refrigeration capacity is required, such as in summer when the outside air temperature is high, even when the discharge pressure of the compressor 9 is increased, it is possible to suppress the discharge temperature from being greatly increased.

  Further, since the gas-phase refrigerant is injected together with the liquid-phase refrigerant in the compression process, the efficiency of the vapor compression refrigerator can be improved as in the so-called “gas injection refrigerator”. That is, in the present invention, the vapor compression refrigerator 1 can be efficiently operated even when a large refrigeration capacity is required while suppressing an increase in the number of parts and an increase in the discharge temperature.

(Second Embodiment)
In the present embodiment, the throttle opening degree of the second decompression device 13 and the rotation speed of the second compression device 9B are controlled in consideration of the suction pressure of the second compression device 9B. Specifically, as shown in FIG. 3, a second pressure detector 15B for detecting the pressure of the refrigerant sucked into the second compression device 9B is provided. Hereinafter, the pressure detector 15A is referred to as a first pressure detector 15A.

  The control unit 15 for the second compression device according to the present embodiment uses a pressure ratio or a pressure difference between the discharge pressure detected by the first pressure detector 15A and the suction pressure detected by the second pressure detector 15B. Thus, the rotational speed of the second compression device 9B is controlled so that the discharge pressure is equal to or lower than a predetermined pressure set in advance. The “pressure ratio” refers to the ratio between the discharge pressure and the suction pressure of the compressor.

  That is, in the present embodiment, the relationship between the discharge pressure and the pressure ratio and the rotation speed of the second compression device 9B is stored in the ROM in the form of a map or a function value. The second compression device controller 15 determines the rotational speed based on the pressure ratio calculated from the pressures detected by the first pressure detector 15A and the second pressure detector 15B, the map, and the like, and performs the second compression. The apparatus 9B is controlled.

  In the present embodiment, the detection signal of the second pressure detector 15B is also input to the second pressure reducing device controller 13B. The controller 13B for the second decompression device controls the temperature of the refrigerant flowing into the high-pressure heat exchanger 3, that is, the discharge refrigerant discharged from the second compression device 9B, in a range where the pressure ratio is equal to or higher than a preset allowable minimum pressure ratio. However, the pressure of the refrigerant is reduced to a pressure that is equal to or lower than a predetermined temperature set in advance.

  The allowable minimum pressure ratio is a pressure ratio determined by the specifications of each compression apparatus and the like, and means a pressure ratio at which the compression apparatus cannot be operated at a pressure ratio smaller than the pressure ratio. The allowable minimum pressure ratio of the second compression device 9B according to this embodiment is about 1.2.

  When the second decompression device controller 13B according to the present embodiment determines that the pressure ratio is smaller than the allowable minimum pressure ratio when the refrigerant is decompressed to a pressure at which the temperature of the discharged refrigerant is equal to or lower than the predetermined temperature ( Hereinafter, the time when this determination is made is referred to as a limit determination), and the refrigerant is decompressed until the pressure ratio reaches the allowable minimum pressure ratio.

  Therefore, when the second pressure reducing device controller 13B makes a limit determination, the second compressor 9B is prioritized over the control of the discharge refrigerant temperature. This is because when the pressure ratio becomes smaller than the allowable minimum pressure ratio, the second compression device 9B is practically stopped and the circulation of the refrigerant is delayed, so that the vapor compression refrigerator 1 is stopped.

  When the limit determination is not made, that is, when the pressure ratio is determined to be equal to or higher than the allowable minimum pressure ratio, the second pressure reducing device control unit 13B depressurizes the refrigerant to a pressure at which the temperature of the discharged refrigerant becomes equal to or lower than the predetermined temperature. .

  In FIG. 3, the second compression device controller 15, the second decompression device control unit 13 </ b> B, and the first decompression device control unit 5 </ b> B are described separately, but in the same manner as in a third embodiment to be described later. The second compressor controller 15, the second decompressor controller 13B, and the first decompressor controller 5B may be integrated into a single controller.

(Third embodiment)
1. Outline of Vapor Compression Refrigerating Machine In the first embodiment, the discharge pressure of the second compression device 9B is set to a predetermined pressure or lower by controlling the rotation speed of the second compression device 9B.

  On the other hand, in the present embodiment, as shown in FIG. 4, the second compression device 9B is configured by a plurality of compressors 9C to 9E connected in series, and the position of the compression process (hereinafter referred to as the refrigerant injection) The position is referred to as “injection pressure”) and the timing to control the discharge pressure of the second compression device 9B to be equal to or lower than a predetermined pressure set in advance.

  That is, the second compression device 9B according to this embodiment includes a plurality of compressors 9C to 9E, a distributor 9J, and a plurality of valves 9F to 9H. The distributor 9J distributes the refrigerant injected into the compression device 9 to the plurality of compressors 9C to 9E.

  The plurality of valves 9F to 9H open and close the refrigerant passages L1 to L3 from the distributor 9J to the plurality of compressors 9C to 9E. That is, the refrigerant is injected into the compression device 9 in the compression process at an injection pressure corresponding to the opened valve among the plurality of valves 9F to 9H.

  Then, the second compression device control unit 15 and the second pressure reduction device control unit 13B cooperate with each other, and the discharge pressure of the second compression device 9B, that is, the discharge pressure of the compressor 9E is set to a predetermined pressure. The throttle opening degree of the second pressure reducing device 13, the rotational speeds of the plurality of compressors 9C to 9E, and the opening and closing of the plurality of valves 9F to 9H are controlled as follows.

2. Control Example of Second Compression Device Control Unit and Second Pressure Reduction Device Control Unit In the present embodiment, at least the second compression device control unit 15 and the second pressure reduction device control unit 13B include one control device (hereinafter, It is described as a control device 15). That is, the computer constituting the control device 15 has a CPU, a RAM, a ROM and the like as shown in FIG. A program for controlling the opening and closing of the plurality of valves 9F to 9H is stored in advance in a nonvolatile storage unit such as a ROM.

  Detection signals from the pressure detector 15A, the outside air temperature detector 17A, the blown air temperature detector 17B, and the discharged refrigerant temperature detector 13A are input to the control device 15. The control device 15 uses the signals of the detectors 15A and 17A to 17C to set the throttle opening of the second decompression device 13, the rotational speeds of the plurality of compressors 9C to 9E, according to a preset control procedure (program), And the opening and closing of each of the plurality of valves 9F to 9H is controlled.

  The pressure detector 15 </ b> A detects the pressure of the refrigerant flowing into the high pressure heat exchanger 3. The outside air temperature detector 17A detects the temperature of the outdoor air, that is, the air that cools the discharged refrigerant. The blown air temperature detector 17 </ b> B detects the temperature of the indoor air cooled by the low pressure heat exchanger 7. The discharged refrigerant temperature detector 13A detects the temperature of the refrigerant discharged from the compressor 9, that is, the compressor 9E.

  FIG. 6 is a flowchart illustrating an example of control executed by the control device 15. This control is executed by the CPU by reading a program stored in the nonvolatile storage unit. When the program is read, first, a temperature difference ΔT between the blow-out temperature T1 detected by the blown air temperature detector 17B and the preset indoor air temperature To is calculated (S10).

  Next, the rotational speed of the first compressor 9A (hereinafter referred to as a target rotational speed Ne) is determined based on the temperature difference ΔT, and the rotational speed of the first compressor 9A is controlled to the target rotational speed Ne. (S20). The target rotation speed Ne is stored in advance in the ROM as a function value of the temperature difference ΔT.

  Thereafter, using the target rotational speed Ne and the outside air temperature T2 detected by the outside air temperature detector 17A as parameters, the target discharge refrigerant pressure (hereinafter referred to as target pressure HPo) and the target discharge refrigerant temperature (hereinafter referred to as target). Temperature HTo) is determined (S30). The target pressure HPo and the target temperature HTo are stored in advance in the ROM as function values of the target rotational speed Ne and the outside air temperature T2.

  Next, after determining which one of the plurality of valves 9F to 9H is to be opened and the other valves are to be closed or all the valves 9F to 9H are to be closed based on the target temperature HTo, according to the determination contents Opening and closing of the plurality of valves 9F to 9H is controlled (S40). In the present embodiment, control is performed so that only one of the plurality of valves 9F to 9H is opened and the other valves are closed.

  Specifically, the valves 9F to 9H are controlled to open and close as follows. That is, when the temperature difference between the target temperature HTo and the discharged refrigerant temperature detected by the discharged refrigerant temperature detector 13A is larger than a predetermined first predetermined temperature difference, the valve 9F is opened and the valves 9G and 9H are opened. Is closed.

  When the temperature difference is smaller than a predetermined second predetermined temperature difference, the valve 9H is opened and the valves 9F and 9G are closed. When the temperature difference is not more than the first predetermined temperature difference and not less than the second predetermined temperature difference, the valve 9G is opened and the valves 9F and 9H are closed. The second predetermined temperature is smaller than the first predetermined temperature difference.

  When it is determined which of the plurality of valves 9F to 9H is to be opened (S40), the throttle opening degree of the second decompression device 13 is such that the refrigerant flowing out of the high-pressure heat exchanger 3 is used as the valve to be opened. The opening is controlled so that the pressure can be reduced to the corresponding injection pressure (S50). When it is determined that all the valves 9F to 9H are closed, the second pressure reducing device 13 is fully closed or has a minimum throttle opening.

  When it is determined that all the valves 9F to 9H are to be closed, the first compressor 9A and the compressors 9C to 9E are (a) the same number of rotations in the first compressor 9A and the compressors 9C to 9E. (B) The rotational speed is controlled so that the refrigerant pressure discharged from the compressor 9, that is, the compressor 9E, becomes the target pressure HPo (S60).

  Therefore, when the theoretical discharge amounts of the first compressor 9A and the compressors 9C to 9E are all the same, in S60, the first compressor 9A and the compressors 9C to 9E all have the same rotational speed.

  When it is determined that only the valve 9F is opened and the other valves 9G and 9H are closed, (a) the rotational speeds of the compressors 9C to 9E are the same, and (b) the refrigerant pressure discharged from the compressor 9E is The number of revolutions is controlled so as to be the target pressure HPo (S70).

That is, when the theoretical discharge amounts of the first compressor 9A and the compressors 9C to 9E are all the same, at least the compressors 9C to 9E have the same rotational speed in S70.
When it is determined that only the valve 9G is opened and the other valves 9F and 9H are closed, (a) the rotational speeds of the first compressor 9A and the compressor 9C are the same, and (b) the rotational speeds of the compressors 9D and 9E. And (c) the rotational speed is controlled so that the refrigerant pressure discharged from the compressor 9E becomes the target pressure HPo (S80).

  That is, when the theoretical discharge amounts of the first compressor 9A and the compressors 9C to 9E are all the same, in S80, the first compressor 9A and the compressor 9C have the same rotational speed, and the compressor 9D, The rotation speed of 9E is the same.

  When it is determined that only the valve 9H is opened and the other valves 9F and 9G are closed, (a) the rotational speeds of the first compressor 9A and the compressors 9C and 9D are the same, and (b) from the compressor 9E The rotational speed is controlled so that the discharged refrigerant pressure becomes the target pressure HPo (S90).

That is, when the theoretical discharge amounts of the first compressor 9A and the compressors 9C and 9D are all the same, in S90, the first compressor 9A and the compressors 9C and 9D have the same rotational speed.
When the processing of S60 to S90 is completed, it is determined whether or not the pressure detected by the pressure detector 15A (hereinafter referred to as discharge pressure) is smaller than the target pressure HPo (S100). When it is determined that the discharge pressure is equal to or higher than the target pressure HPo (S100: NO), S50 is executed. When it is determined that the discharge pressure is smaller than the target pressure HPo (S100: YES), S10 is executed.

(Fourth embodiment)
In the vapor compression refrigerator 1 according to the third embodiment, the present embodiment considers the suction pressures of the first compressor 9A and the compressors 9C to 9E in the same manner as the second embodiment. And the number of rotations of the first compressor 9A and the compressors 9C to 9E are controlled.

  That is, in the present embodiment, as shown in FIG. 7, pressure detectors 15C to 15F for detecting the suction pressure are provided on the suction sides of the first compressor 9A and the compressors 9C to 9E. Pressure detectors 15G and 15H for detecting the discharge pressure are provided on the discharge side of the compressors 9C and 9D.

  Note that the pressure detectors 15D to 15F correspond to the second pressure detector 15B according to the second embodiment. Detection signals from the pressure detectors 15D to 15H are input to the second compressor controller 15 and the second decompressor controller 13B.

  FIG. 8 is a flowchart illustrating an example of control executed by the control device 15 according to the present embodiment. In FIG. 8, the same control numbers as those of the third embodiment, that is, FIG. 6, are given the same step numbers. Hereinafter, in FIG. 8, only different points from the third embodiment will be described.

  In S50 of FIG. 8, the control device 15, that is, the second decompression device control unit 13B, discharges refrigerant in a range where the pressure ratio of the compressors 9C to 9E is equal to or higher than the allowable minimum pressure ratio, as in the second embodiment. The refrigerant is depressurized to a pressure at which the temperature becomes a predetermined temperature or lower.

  The control unit (not shown) for controlling the second compression device control unit 15 and the first compression device 9A is similar to the second embodiment in S60, S70, S90, and S90 in FIG. , The number of rotations is determined based on the discharge pressure and the pressure ratio stored in advance, the map showing the relationship between the rotation number and the detected pressure ratio, and the first compressor 9A and the compressors 9C to 9E are controlled. .

  Specifically, in S60, the rotation speed is controlled so that the pressure ratios in the first compressor 9A and the compressors 9C to 9E are the same, and the refrigerant pressure discharged from the compressor 9E becomes the target pressure HPo. Is done. In S70, the rotation speed is controlled so that the pressure ratios in the compressors 9C to 9E are the same, and the refrigerant pressure discharged from the compressor 9E becomes the target pressure HPo.

  In S80, the pressure ratios of the first compressor 9A and the compressor 9C are the same, the pressure ratios of the compressors 9D and 9E are the same, and the refrigerant pressure discharged from the compressor 9E becomes the target pressure HPo. The rotation speed is controlled. In S90, the rotation speed is controlled so that the pressure ratios in the first compressor 9A and the compressors 9C and 9D are the same, and the refrigerant pressure discharged from the compressor 9E becomes the target pressure HPo.

  In addition, when the pressure ratio of the first compressor 9A and the compressors 9C to 9E determined in the processing of S60 to S90 is smaller than the allowable minimum pressure ratio, the first compressor 9A and the like correspond to the allowable minimum pressure ratio. The number of rotations is controlled.

(Other embodiments)
In the above-described embodiment, the second compressor 9B is configured as a fixed capacity compressor, but the present invention is not limited to this, and the second compressor 9B is configured as a variable capacity compressor. May be.

  In the above-described embodiment, the compression device 9 is configured by the plurality of compression devices 9A and 9B. However, the present invention is not limited to this, and the compression device 9 is configured by a single compressor having an injection port. It may be configured. In addition, the format of the compression apparatus 9 is not ask | required. That is, any method such as a reciprocating method, a rotary method, a vane method, a scroll method, or the like may be used.

  In the above-described embodiment, the first pressure reducing device 5 and the second pressure reducing device 13 are variable throttles that can change the throttle opening, but the present invention is not limited to this, for example, a capillary tube or the like. An ejector having both a fixed throttle and a pump action may be used as the pressure reducing device.

  In the above-described embodiment, the vapor compression refrigerator according to the present invention is applied to an air conditioner. However, the present invention is not limited to this, and an electric heating element such as a computer is supplied with a fluid such as a refrigerant or cooling water. It can also be applied to a method of cooling by circulating in an electric heater.

  In the above embodiment, the refrigerant pressure on the high pressure side is lower than the critical pressure of the refrigerant. However, the present invention is not limited to this, and supercritical refrigeration in which the refrigerant pressure on the high pressure side is equal to or higher than the critical pressure of the refrigerant. It can also be applied to machines. In the supercritical refrigerator, the high-pressure heat exchanger 3 does not condense the refrigerant.

  In the second and fourth embodiments, the second compression device 9B and the second pressure reduction device 13 are controlled using the pressure ratio, but the present invention is not limited to this, and the discharge pressure and the suction pressure The second compression device 9B and the second decompression device 13 may be controlled using a pressure difference.

  That is, the relationship between the discharge pressure, the discharge refrigerant temperature, the pressure difference, and the rotation speed of the second compressor 9B is stored in the ROM in the form of a map or a function value. Then, after the second decompression device controller 13B and the second compression device controller 15 determine the throttle opening and the rotational speed based on the map and the like, the second decompression device 9B and the second decompression device 13 are moved. Control.

  The present invention is not limited to the above-described embodiment as long as it matches the gist of the invention described in the claims.

DESCRIPTION OF SYMBOLS 1 ... Vapor compression refrigerator 3 ... High pressure heat exchanger 5 ... 1st decompression device 7 ... Low pressure heat exchanger 9 ... Compression device 9A ... 1st compression device 9B ... 2nd compression device 11 ... Gas-liquid separator 13 ... 1st 2 Pressure reducing device

Claims (7)

In the vapor compression refrigeration system that moves the heat on the low temperature side to the high temperature side,
A high-pressure heat exchanger that cools the high-pressure refrigerant;
A first decompression device that decompresses the high-pressure refrigerant cooled in the high-pressure heat exchanger;
A low-pressure heat exchanger that evaporates the low-pressure refrigerant decompressed by the first decompression device;
A compression device that compresses a low-pressure refrigerant and discharges the refrigerant to the high-pressure heat exchanger side, and sucks the first compression device, the refrigerant discharged from the first compression device, and the gas-liquid two-phase refrigerant. A compression device in which a refrigerant in a gas-liquid two-phase state is injected in a compression process by having a second compression device to compress;
A first pressure detector for detecting the pressure of the refrigerant discharged from the second compression device;
A second pressure detector for detecting the pressure of the refrigerant sucked into the second compression device;
A control unit for a second compression device that controls the operation of the second compression device, wherein a pressure difference or a pressure between a pressure detected by the first pressure detector and a pressure detected by the second pressure detector A vapor compression refrigeration apparatus comprising: a second compressor control unit that uses a ratio to make the pressure detected by the first pressure detector not more than a predetermined pressure set in advance. A second decompression device that decompresses the high-pressure refrigerant cooled by the high-pressure heat exchanger to a pressure higher than the pressure of the refrigerant decompressed by the first decompression device;
The vapor compression refrigeration apparatus according to claim 1, wherein the gas-liquid two-phase refrigerant decompressed by the second decompression device is injected into the compression device.   The second pressure reducing device has a function of depressurizing the refrigerant to a pressure at which a temperature of the refrigerant flowing into the high-pressure heat exchanger is equal to or lower than a predetermined temperature set in advance. 2. The vapor compression refrigeration apparatus according to 2. The second decompression device includes:
A temperature detector that detects a temperature of the refrigerant flowing into the high-pressure heat exchanger; and a controller for a second pressure reducing device that changes a throttle opening based on the temperature detected by the temperature detector. The vapor compression refrigeration apparatus according to claim 3. The second pressure reducing device is configured such that the temperature of the refrigerant flowing into the high-pressure heat exchanger is a pressure that is equal to or lower than a predetermined temperature within a range where the pressure ratio is equal to or higher than a preset allowable minimum pressure ratio. The vapor compression refrigeration apparatus according to any one of claims 2 to 4, wherein the vapor compression refrigeration apparatus has a function of reducing pressure.   6. The vapor compression according to claim 1, wherein the second compression device controller variably controls a theoretical discharge amount discharged from the second compression device per unit time. 7. Type refrigeration equipment. The second compression device includes:
Multiple compressors,
A distributor for distributing the injected refrigerant to the plurality of compressors; and a plurality of valves for opening and closing each refrigerant passage from the distributor to the plurality of compressors;
The vapor compression refrigeration apparatus according to any one of claims 1 to 6, wherein the second compressor control unit controls opening and closing of each of the plurality of valves.