JP6747360B2 - Refrigeration cycle - Google Patents

Description

The present invention relates to a refrigeration cycle equipped with an injection circuit.

2. Description of the Related Art Conventionally, in a refrigerating cycle for adjusting the temperature inside a refrigerator car or the like, there is known a refrigerating cycle which is provided with an injection circuit in order to enhance a refrigerating capacity and improve a coefficient of performance (COP).

In the refrigeration cycle described in Patent Document 1, an electromagnetic valve is provided on the upstream side of the temperature type expansion valve provided in the injection circuit. This refrigeration cycle regulates the flow rate of the refrigerant injected into the compressor from the thermal expansion valve through the intermediate heat exchanger by performing the inching operation of the solenoid valve multiple times immediately after the operation is started. There is. As a result, this refrigeration cycle regulates the flow rate of the refrigerant injected from the injection circuit into the compressor even when the thermal expansion valve is opened more than necessary at the start of operation, thereby reducing the driving force of the compressor. It prevents the increase and liquid back phenomenon to the compressor. In addition, Patent Document 1 proposes to provide an electronic expansion valve whose flow passage opening can be adjusted by a control device, instead of providing a thermal expansion valve and a solenoid valve in an injection circuit.

Japanese Patent No. 5463192

However, the refrigeration cycle described in Patent Document 1 has a problem that the number of parts is increased and the manufacturing cost is increased because the injection circuit is provided with the solenoid valve. Further, if an electronic expansion valve or the like is provided in the injection circuit instead of the temperature expansion valve, there is a problem that the control for adjusting the flow path opening becomes complicated.

By the way, Patent Document 1 is intended to prevent an increase in the flow rate of the refrigerant injected from the injection circuit into the compressor when the temperature type expansion valve is opened more than necessary at the start of the operation of the refrigeration cycle. On the other hand, when the flow path of the thermal expansion valve is closed or the flow path opening is small at the start of the operation of the refrigeration cycle or at the time of switching the compressor in operation from thermo-off to thermo-on, it is different from the above. Problems may occur. That is, in that case, an abnormal state in which the pressure and temperature of the main circuit rapidly increase and the discharge pressure of the compressor also rapidly increases may occur transiently. At that time, if the operation of the compressor is stopped in order to prevent the discharge pressure of the compressor from rising, there is a concern that the refrigeration performance of the refrigeration cycle will be affected.

In view of the above points, an object of the present invention is to provide a refrigeration cycle capable of preventing an abnormal state that transiently occurs at the time of starting the compressor.

In order to achieve the above object, in the refrigeration cycle of the invention according to claim 1, the refrigerant compressed by the compressor (5, 51, 52) is condensed by the condenser (6), and the intermediate heat exchanger (7) is connected. A main circuit (2) for reducing pressure in the first expansion valve (8), evaporating it in the evaporator (9), and circulating it to the compressor after passing through;
The flow path opening degree of the refrigerant branched from the branch portion (15) provided in the pipe connecting the condenser and the intermediate heat exchanger is determined according to the degree of superheat of the refrigerant flowing downstream from the intermediate heat exchanger. Is reduced by a temperature type second expansion valve (17) that is automatically adjusted, heat is exchanged with the refrigerant flowing through the main circuit by the intermediate heat exchanger, and then the injection circuit (3) is injected into the compressor. ,
The rotation speed of the compressor is changed from 0 rpm to a predetermined instruction rotation speed from a normal change speed at which the rotation speed of the compressor is changed when the rotation speed of the compressor is changed from a rotation speed higher than 0 rpm to a predetermined instruction rotation speed. A control device (4) for slowing down the rate of change of the number of revolutions of the compressor when the number of revolutions is changed. The control device sets the changing speed at which the rotating speed of the compressor changes when the rotating speed of the compressor is changed from 0 rpm to a predetermined instructed rotating speed to half or less of the normal changing speed.

According to this, when the number of revolutions of the compressor is changed from 0 rpm to a predetermined instruction number of revolutions (hereinafter, referred to as "compressor start"), the speed at which the discharge pressure of the compressor rises becomes slow. Therefore, the time during which the refrigerant pressure in the main circuit is relatively small becomes long, and the flow path opening degree of the temperature-type second expansion valve changes to the superheat degree of the refrigerant flowing downstream of the intermediate heat exchanger during that time. Corresponding. Therefore, in this refrigeration cycle, it is possible to prevent transient occurrence of an abnormal state such as a sudden increase in the discharge pressure of the compressor due to a sudden increase in the pressure and temperature of the main circuit at the time of starting the compressor. it can.

Further, the refrigeration cycle of the invention according to claim 1 uses a thermal expansion valve, and the compressor is started without adding a component such as an electromagnetic valve unlike the refrigeration cycle described in Patent Document 1 described above. It is possible to prevent an abnormal condition that sometimes occurs transiently.

In the refrigeration cycle of the invention according to claim 2 , the refrigerant compressed by the compressor (5, 51, 52) is condensed in the condenser (6) and passed through the intermediate heat exchanger (7), and then the first A main circuit (2) for decompressing with an expansion valve (8), evaporating with an evaporator (9), and circulating with the compressor;
The flow path opening degree of the refrigerant branched from the branch portion (15) provided in the pipe connecting the condenser and the intermediate heat exchanger is determined according to the degree of superheat of the refrigerant flowing downstream from the intermediate heat exchanger. And an injection circuit (3) for decompressing with a temperature type second expansion valve (17) that is automatically adjusted, heat-exchanged with the refrigerant flowing through the main circuit in the intermediate heat exchanger, and then injecting the heat into the compressor. ,
When changing the rotation speed of the compressor from 0 rpm to a predetermined instruction rotation speed, after holding the rotation speed of the compressor at an intermediate rotation speed lower than the predetermined instruction rotation speed for a predetermined time, the intermediate rotation speed is changed to a predetermined rotation speed from the predetermined rotation speed. A control device (4) for changing the rotation speed to an instruction speed. The intermediate rotation speed is a range of the minimum rotation speed among the rotation speeds at which the compressor can be continuously operated.

According to this, at the time of starting the compressor, the refrigerant pressure in the main circuit is maintained in a relatively small state while the rotational speed of the compressor is maintained at the intermediate rotational speed. Meanwhile, the flow path opening degree of the temperature-type second expansion valve corresponds to the superheat degree of the refrigerant flowing on the downstream side of the intermediate heat exchanger. Therefore, in this refrigeration cycle, it is possible to prevent transient occurrence of an abnormal state such as a sudden increase in the discharge pressure of the compressor due to a sudden increase in the pressure and temperature of the main circuit at the time of starting the compressor. it can.

Further, the refrigeration cycle of the invention according to claim 2 also uses the thermal expansion valve similarly to the invention according to claim 1, and transiently at the time of starting the compressor without adding components such as a solenoid valve. It is possible to prevent the abnormal state that occurs.

In addition, the reference numerals in parentheses attached to the above-described respective components show an example of a correspondence relationship with a specific configuration described in an embodiment described later.

It is a figure which shows schematic structure of the refrigerating cycle which concerns on 1st Embodiment. It is a flow chart which shows the control method of the refrigerating cycle concerning a 1st embodiment. It is a graph which compared the change speed of the number of rotations at the time of starting of a compressor, and the normal change speed. It is a flow chart which shows control processing of a refrigerating cycle concerning a 2nd embodiment. It is a graph which compared the change of the number of rotations at the time of starting of a compressor, and the change of the number of rotations at the time of normal. It is a flow chart which shows control processing of a refrigerating cycle concerning a 3rd embodiment. It is a flow chart which shows control processing of a refrigerating cycle concerning a 4th embodiment. It is a flow chart which shows control processing of a refrigerating cycle concerning a 5th embodiment. It is a flowchart which shows the control processing of the refrigeration cycle which concerns on 6th Embodiment. It is a flow chart which shows control processing of a refrigerating cycle concerning a 7th embodiment. It is a figure which shows schematic structure of the refrigerating cycle which concerns on 8th Embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each of the following embodiments, the same or equivalent portions will be denoted by the same reference numerals for description.

(First embodiment)
The first embodiment will be described with reference to the drawings. The refrigeration cycle of the present embodiment is used, for example, to adjust the temperature of the interior space of a refrigeration vehicle or the like.

As shown in FIG. 1, the refrigeration cycle 1 includes a main circuit 2, an injection circuit 3, a control device 4, and the like. The main circuit 2 is connected to a compressor 5, a condenser 6, an intermediate heat exchanger 7, a first expansion valve 8 and an evaporator 9 by piping.

The compressor 5 is an electric compressor, and has an electric motor (not shown) and a refrigerant compression unit (not shown) that is rotationally driven by the electric motor. As the electric motor, various electric motors such as an AC motor or a DC motor can be adopted. The rotation of the electric motor is controlled by the drive signal of the control device 4. The refrigerant compression unit can employ various compression mechanisms such as a rotary compression mechanism or a scroll compression mechanism. The refrigerant compression unit of the present embodiment is a fixed capacity type compression mechanism in which the discharge capacity of the refrigerant per one rotation is fixed. The refrigerant compression unit rotates in synchronization with the rotation of the motor. In the following description, the rotation of the compressor 5 means the rotation of both the motor and the refrigerant compression section.

The refrigerant compression unit is configured to compress the refrigerant supplied from the low-pressure refrigerant suction port 5a and the refrigerant supplied from the intermediate-pressure refrigerant suction port 5b (that is, the injection port), and discharge the refrigerant from the refrigerant discharge port 5c. ing. The low-pressure refrigerant suction port 5 a is connected to a pipe of the main circuit 2 on the accumulator 11 side and sucks refrigerant from the main circuit 2. The intermediate pressure refrigerant suction port 5b is connected to the injection circuit 3, and the refrigerant is injected from the injection circuit 3. The refrigerant discharge port 5c is connected to a pipe on the condenser 6 side of the main circuit 2 and discharges the refrigerant to the main circuit 2.

The refrigerant inlet of the condenser 6 is connected to the pipe on the refrigerant discharge port 5c side of the compressor 5. The condenser 6 is a heat exchanger that condenses the refrigerant by exchanging heat between the outside air blown from the condenser blower 12 and the refrigerant. The drive of the blower 12 for the condenser is controlled by the drive signal of the control device 4.

A receiver 13 is provided on the refrigerant outlet side of the condenser 6. The receiver 13 separates the refrigerant flowing out of the condenser 6 into a gas-phase refrigerant and a liquid-phase refrigerant, and sends only the liquid-phase refrigerant to the downstream side. An intermediate heat exchanger 7 is provided in a pipe on the downstream side of the receiver 13 via a refrigeration valve 14 and a branch portion 15. The injection circuit 3 is connected between the branch portion 15 and the intermediate pressure refrigerant suction port 5b of the compressor 5. The intermediate heat exchanger 7 and the injection circuit 3 will be described later.

A first expansion valve 8 is provided on the refrigerant outlet side pipe of the intermediate heat exchanger 7. The first expansion valve 8 is a decompression device that decompresses and expands the refrigerant that has flowed out from the intermediate heat exchanger 7. The first expansion valve 8 of the present embodiment is a thermal expansion valve, and has a flow path adjusting mechanism 8a connected to the refrigerant inlet side pipe of the evaporator 9 and a temperature sensing element provided on the refrigerant outlet side of the evaporator 9. And a portion 8b. In the first expansion valve 8, the flow passage opening of the flow passage adjusting mechanism 8a is automatically adjusted by a mechanical mechanism so that the degree of superheat detected by the temperature sensing unit 8b approaches a preset predetermined value.

The refrigerant inlet of the evaporator 9 is connected to the refrigerant outlet side pipe of the flow path adjusting mechanism 8a included in the first expansion valve 8. The evaporator 9 is a heat exchanger for exchanging heat between the air circulated in the interior space by the blower 16 for the evaporator and the refrigerant in the gas-liquid two-phase state flowing out from the first expansion valve 8. The drive of the evaporator blower 16 is controlled by the drive signal of the control device 4, and blows the air circulating in the refrigerator to the evaporator 9. The air blown to the evaporator 9 by the evaporator blower 16 is cooled by the endothermic action of the latent heat of vaporization of the refrigerant flowing through the evaporator 9. Note that, in FIG. 1, the direction in which the air blown to the evaporator 9 by the drive of the blower 16 for the evaporator flows is indicated by an arrow with the symbol AF.

An accumulator 11 is provided on the refrigerant outlet side of the evaporator 9. The accumulator 11 separates the refrigerant flowing from the evaporator 9 into a gas-phase refrigerant and a liquid-phase refrigerant, stores the liquid-phase refrigerant, and supplies the gas-phase refrigerant to the compressor 5. The low pressure refrigerant suction port 5 a of the refrigerant compression section of the compressor 5 is connected to the refrigerant outlet side of the accumulator 11. Therefore, the refrigerant flowing out from the refrigerant outlet of the evaporator 9 flows toward the compressor 5 via the accumulator 11 and is sucked into the low-pressure refrigerant suction port 5a of the refrigerant compression section of the compressor 5.

The injection circuit 3 is a circuit that connects the branch portion 15 provided in the main circuit 2 and the intermediate pressure refrigerant suction port 5b of the compressor 5, and the second expansion valve 17 and the intermediate heat exchanger 7 are connected by piping. Has been done. The second expansion valve 17 is a decompression device that decompresses and expands the refrigerant, which has flowed out of the condenser 6 through the receiver 13 and then branched into the injection circuit 3 from the branch portion 15, to an intermediate pressure. The second expansion valve 17 is also a thermal expansion valve, and has a flow path adjusting mechanism 17a connected to the refrigerant inlet side pipe of the intermediate heat exchanger 7 in the injection circuit 3, and an intermediate heat exchanger in the injection circuit 3. 7 has a temperature sensing part 17b provided in the refrigerant outlet side pipe. Also in the second expansion valve 17, the flow passage opening of the flow passage adjusting mechanism 17a is automatically adjusted by the mechanical mechanism so that the degree of superheat detected by the temperature sensing unit 17b approaches a predetermined value set in advance.

The intermediate heat exchanger 7 includes a liquid-phase refrigerant flowing on the downstream side of the branch portion 15 in the main circuit 2 and a gas-liquid refrigerant that has flowed from the branch portion 15 to the injection circuit 3 and has been decompressed and expanded to an intermediate pressure by the second expansion valve 17. It is a heat exchanger that exchanges heat with a refrigerant in a two-phase state. The degree of supercooling of the refrigerant flowing through the main circuit 2 increases as it passes through the intermediate heat exchanger 7. On the other hand, the refrigerant flowing through the injection circuit 3 becomes a gas-phase refrigerant after passing through the intermediate heat exchanger 7, and is injected into the refrigerant compression section from the intermediate pressure refrigerant suction port 5b of the compressor 5. As a result, the refrigeration cycle 1 including the injection circuit 3 can improve the COP by increasing the refrigerating capacity of the evaporator 9 and reducing the superheat degree of the refrigerant compressed by the compressor 5.

Subsequently, the control device 4 will be described. The control device 4 includes a processor that performs control processing and arithmetic processing, a microcomputer that stores a storage unit such as ROM and RAM that stores programs and data, and peripheral circuits thereof. The storage unit of the control device 4 is composed of a non-transitional substantive storage medium. The control device 4 performs various control processing and arithmetic processing based on the program stored in the storage unit, and controls the operation of each device connected to the output port.

An internal temperature sensor 18 for detecting the internal temperature of the refrigerator, an outside air temperature sensor 19 for detecting the outside air temperature, etc. are electrically connected to the input port of the control device 4. The internal temperature sensor 18 of the present embodiment is a thermistor provided on the upstream side of the evaporator 9. The control device 4 can detect the temperature of the air circulating in the inside by the inside temperature sensor 18.

An operation panel 20 that can be operated by the user is electrically connected to the input port of the control device 4. The operation panel 20 is provided with a refrigerator operation switch 21 for operating the refrigeration cycle 1, a temperature setting switch 22 for setting a target temperature in the refrigerator, and the like.

The motor of the compressor 5 and the like are electrically connected to the output port side of the control device 4. The control device 4 calculates the heat load of the refrigeration cycle 1 based on the difference between the internal temperature detected by the internal temperature sensor 18 and the set temperature set by the temperature setting switch 22. The control device 4 supplies a drive current to the motor of the compressor 5 to control the rotation speed of the compressor 5 so that the rotation speed of the compressor 5 has a value corresponding to its heat load.

By the way, in general, the refrigeration cycle 1 is provided outside the refrigerator except for the evaporator 9. Therefore, when the drive of the compressor 5 is stopped, the flow path opening degree of the second expansion valve 17 controlled by the temperature sensing unit 17b provided in the injection circuit 3 is open. Therefore, if the flow path of the second expansion valve 17 is closed or the flow path opening degree is small when the operation of the refrigeration cycle 1 is started or when the compressor 5 is switched from thermo-off to thermo-on during the refrigeration cycle operation, An abnormal state in which the pressure and temperature of the circuit 2 rapidly increase and the discharge pressure of the compressor 5 also rapidly increases may occur transiently. At that time, if the operation of the compressor 5 is stopped in order to prevent the discharge pressure of the compressor 5 from rising, there is a concern that the refrigeration performance of the refrigeration cycle 1 will be affected.

Therefore, the refrigeration cycle 1 of the present embodiment employs the control method described below.

FIG. 2 is a flowchart showing a control process executed by the control device 4 included in the refrigeration cycle 1 of this embodiment. This processing is performed by the control device 4 executing the control program stored in the storage unit. In addition, this process is repeatedly executed at predetermined time intervals during the operation of the refrigeration cycle 1.

The operation of the refrigeration cycle 1 is started when the user operates the refrigerator operation switch 21 of the operation panel 20. In step S10, the control device 4 determines whether the refrigerator operation switch 21 is switched from off to on. When the control device 4 determines that the refrigerator operation switch 21 is switched from off to on, the control device 4 moves the process to step S20.

In step S20, the control device 4 calculates the instructed rotation speed of the compressor 5. Specifically, the control device 4 calculates the heat load of the refrigeration cycle 1 based on the difference between the internal temperature detected by the internal temperature sensor 18 and the set temperature set by the temperature setting switch 22. The control device 4 calculates the instructed rotation speed of the compressor 5 so as to correspond to the heat load.

Subsequently, in step S30, the control device 4 changes the rotation speed of the compressor 5 from 0 rpm when the refrigerator operation switch 21 is off to the predetermined instruction rotation speed calculated in step S20. At this time, the control device 4 suppresses the changing speed (that is, the increasing speed of the rotation speed) [rpm/s] at which the rotation speed of the compressor 5 changes. Specifically, the control device 4 makes the speed of increase in the number of revolutions of the compressor 5 at the time of start-up slower than the normal change speed. In this specification, the start-up of the compressor 5 means the time when the rotation speed of the compressor 5 is changed from 0 rpm to a predetermined instruction rotation speed. Further, in the present specification, the normal changing speed means a speed at which the rotation speed of the compressor 5 changes when the rotation speed of the compressor 5 is changed from a rotation speed larger than 0 rpm to a predetermined instruction rotation speed (that is, The rate of increase in the number of revolutions under normal conditions) [rpm/s].

The control device 4 slows the speed of increase in the rotation speed of the compressor 5 at the time of starting the compressor 5, so that the speed at which the discharge pressure of the compressor 5 increases becomes slow. Therefore, the time during which the refrigerant pressure in the main circuit 2 is relatively small becomes long, and the flow path opening of the temperature type second expansion valve 17 is provided downstream of the intermediate heat exchanger 7 during that time. This corresponds to the degree of superheat of the refrigerant detected by the temperature sensing unit 17b. Therefore, at the time of starting the compressor 5, it is possible to prevent a transient occurrence of an abnormal state in which the pressure and the temperature of the main circuit 2 rapidly increase and the discharge pressure of the compressor 5 also rapidly increases.

Note that the control device 4 preferably sets the changing speed at which the rotation speed of the compressor 5 changes at the time of starting the compressor 5 to half or less of the normal changing speed. As a result, the time required for the rotational speed of the compressor 5 to reach the predetermined instructed rotational speed is twice or more the time required for the normal change speed. Therefore, the flow path opening degree of the temperature type second expansion valve 17 is sufficiently secured for a time corresponding to the degree of superheat of the refrigerant detected by the temperature sensing unit 17b.

On the other hand, in step S10 described above, when the refrigerator operation switch 21 is continuously turned on, the control device 4 determines that the refrigerator operation switch 21 has not been switched from off to on, and the process is performed in step S40. Move to.

In step S40, the control device 4 calculates the instructed rotation speed of the compressor 5 as in step S20.

Subsequently, in step S50, the control device 4 changes the rotation speed of the compressor 5 to the predetermined instruction rotation speed calculated in step S40. At this time, the control device 4 sets the changing speed at which the rotation speed of the compressor 5 changes (that is, the increasing speed of the rotation speed) as the normal changing speed.

After step S30 or step S50, the process is once terminated, and after the elapse of a predetermined time, the processes of steps S10 to S50 described above are executed again.

Next, FIG. 3 shows a graph comparing the changing speed at which the rotation speed of the compressor 5 changes at the time of starting the compressor 5 with the normal changing speed.

In FIG. 3, a change in the rotation speed of the compressor 5 at the start of the compressor 5 is shown by a solid line A, and a change in the rotation speed of the compressor 5 at a normal time is shown by a broken line B. In addition, the normal time refers to a time when the rotation speed of the compressor 5 is changed from a predetermined rotation speed α larger than 0 rpm to a predetermined instruction rotation speed β.

The slope of the solid line A represents the changing speed of the rotation speed of the compressor 5 when the compressor 5 is started, and the slope of the broken line B represents the changing speed of the rotation speed of the compressor 5 in normal time. The slope of the solid line A is gentler than the slope of the broken line B. Therefore, it can be seen that the changing speed of the rotation speed of the compressor 5 at the time of starting the compressor 5 is slower than the changing speed of the rotation speed of the compressor 5 at the normal time.

The refrigeration cycle 1 of the first embodiment described above has the following operational effects.

(1) In the first embodiment, the control device 4 makes the changing speed of the rotation speed of the compressor 5 at the time of starting the compressor 5 slower than the normal changing speed. As a result, when the compressor 5 is started, the speed at which the discharge pressure of the compressor 5 rises becomes slow. Therefore, the time when the refrigerant pressure in the main circuit 2 is relatively small becomes long, and the opening degree of the flow path of the temperature-type second expansion valve 17 becomes equal to the superheat degree of the refrigerant flowing downstream from the intermediate heat exchanger 7 during that time. Corresponding. Therefore, in the refrigerating cycle 1, when the compressor 5 is started, the pressure and temperature of the main circuit 2 suddenly increase, and the discharge pressure of the compressor 5 also suddenly increases. Can be prevented.

Further, the refrigeration cycle 1 of the first embodiment uses a thermal expansion valve, and further, without adding a component such as a solenoid valve as in the refrigeration cycle 1 described in Patent Document 1 described above, It is possible to prevent an abnormal state that transiently occurs at the time of starting.

(2) In the first embodiment, it is preferable that the control device 4 sets the changing speed of the rotation speed of the compressor 5 at the time of starting the compressor 5 to half or less of the normal changing speed. Accordingly, when the compressor 5 is started, the time required for the rotational speed of the compressor 5 to reach the predetermined instructed rotational speed can be set to be twice or more the time at the normal changing speed. Therefore, it is possible to secure a sufficient time for the opening degree of the flow path of the temperature-type second expansion valve 17 to correspond to the degree of superheat of the refrigerant flowing on the downstream side of the intermediate heat exchanger 7.

(Second embodiment)
The second embodiment will be described. The second embodiment is a modification of the first embodiment with respect to a part of the control processing executed by the control device 4, and is similar to the first embodiment in the other respects, and therefore is different from the first embodiment. Only the part will be described.

FIG. 4 is a flowchart showing a control process executed by the control device 4 included in the refrigeration cycle 1 of the second embodiment. This process is repeatedly executed at predetermined time intervals during the operation of the refrigeration cycle 1.

The processing of steps S10, S20, and S40 is the same as the processing described in the first embodiment.

In step S35 following step S20, the control device 4 first increases the rotation speed of the compressor 5 from 0 rpm when the refrigerator operation switch 21 is off to the intermediate rotation speed, and at the intermediate rotation speed for a predetermined time. Hold. The intermediate rotation speed is a rotation speed lower than the instructed rotation speed, and is stored in the control device 4 in advance. After a lapse of a predetermined time, the control device 4 increases the intermediate rotation speed to the predetermined instruction rotation speed calculated in step S20.

While the control device 4 holds the rotation speed of the compressor 5 at the intermediate rotation speed for a predetermined time when the compressor 5 is started, the refrigerant pressure in the main circuit 2 is maintained in a relatively small state. Meanwhile, the opening degree of the flow path of the temperature-type second expansion valve 17 corresponds to the degree of superheat of the refrigerant flowing on the downstream side of the intermediate heat exchanger 7. Therefore, at the time of starting the compressor 5, it is possible to prevent a transient occurrence of an abnormal state in which the pressure and the temperature of the main circuit 2 rapidly increase and the discharge pressure of the compressor 5 also rapidly increases.

In addition, it is preferable that the intermediate rotation speed is within a range of the minimum rotation speed among the rotation speeds of the compressor 5 that can be continuously operated. It should be noted that the range of the minimum rotation speed may be the minimum rotation speed at which the compressor 5 can be substantially operated, and in addition to the minimum rotation speed indicated in the design of the compressor 5, ±10 with respect to the minimum rotation speed. It includes a range of error of about %. As a result, the refrigerant pressure in the main circuit 2 is maintained at the lowest state within the range in which the compressor 5 can be continuously operated while the rotational speed of the compressor 5 is maintained at the intermediate rotational speed. Therefore, the above-mentioned abnormal state is more likely to occur transiently until the flow path opening degree of the temperature-type second expansion valve 17 corresponds to the degree of superheat of the refrigerant flowing on the downstream side of the intermediate heat exchanger 7. It can be surely prevented.

On the other hand, in step S10 described above, when the refrigerator operation switch 21 is continuously turned on, the process proceeds to step S40. After the control device 4 calculates the instructed rotation speed of the compressor 5 in step S40, the process proceeds to step S55.

Subsequently, in step S55, the control device 4 changes the rotation speed of the compressor 5 to the predetermined instruction rotation speed calculated in step S40. At this time, the control device 4 sets the changing speed at which the rotation speed of the compressor 5 changes as the normal changing speed, and continuously changes the rotation speed to a predetermined instruction rotation speed.

After step S35 or step S55, the process is once terminated, and after a lapse of a predetermined time, the processes of steps S10 to S55 described above are executed again.

Next, FIG. 5 shows a graph comparing changes in the rotation speed of the compressor 5 at the time of starting the compressor 5 and changes in the rotation speed of the compressor 5 at the normal time.

In FIG. 5, a change in the rotation speed of the compressor 5 at the start of the compressor 5 is shown by a solid line A, and a change in the rotation speed of the compressor 5 at a normal time is shown by a broken line B.

The slope of the solid line A represents the changing speed of the rotation speed of the compressor 5 when the compressor 5 is started, and the slope of the broken line B represents the changing speed of the rotation speed of the compressor 5 in normal time.

The slope of solid line A from time t0 to time t10, the slope of solid line A from time t20 to time t30, and the slope of broken line B are the same. However, as indicated by the solid line A, the rotation speed of the compressor 5 at the start of the compressor 5 is maintained at the intermediate rotation speed γ from the time t10 to the time t20. The intermediate rotation speed γ is in the range of the minimum rotation speed among the rotation speeds of the compressor 5 that can be continuously operated. As described above, in the second embodiment, it is possible to maintain the refrigerant pressure of the main circuit 2 at the lowest pressure in the range where the compressor 5 can be continuously operated from time t0 to time t20.

The refrigeration cycle 1 of the second embodiment described above has the following operational effects.

(1) In the second embodiment, when the compressor 5 is started, the control device 4 holds the rotation speed of the compressor 5 at the intermediate rotation speed for a predetermined time, and then changes from the intermediate rotation speed to the predetermined instruction rotation speed. Let As a result, at the time of starting the compressor 5, the refrigerant pressure in the main circuit 2 is maintained at a relatively low level while the rotational speed of the compressor 5 is maintained at the intermediate rotational speed. Meanwhile, the opening degree of the flow path of the temperature-type second expansion valve 17 corresponds to the degree of superheat of the refrigerant flowing on the downstream side of the intermediate heat exchanger 7. Therefore, in the refrigerating cycle 1, when the compressor 5 is started, the pressure and temperature of the main circuit 2 suddenly increase, and the discharge pressure of the compressor 5 also suddenly increases. Can be prevented.

Further, the refrigeration cycle 1 of the second embodiment also uses the temperature type expansion valve, and further, without adding a component such as an electromagnetic valve unlike the refrigeration cycle 1 described in Patent Document 1 described above, It is possible to prevent an abnormal state that transiently occurs at the time of starting.

(2) In the second embodiment, the intermediate rotation speed is preferably in the range of the minimum rotation speed of the rotation speeds of the compressor 5 that can be continuously operated. As a result, at the time of starting the compressor 5, the refrigerant pressure of the main circuit 2 is maintained at the lowest pressure in the range where continuous operation of the compressor 5 is possible while the rotational speed of the compressor 5 is maintained at the intermediate rotational speed. It is possible. Therefore, the above-mentioned abnormal state is more likely to occur transiently until the flow path opening degree of the temperature-type second expansion valve 17 corresponds to the degree of superheat of the refrigerant flowing on the downstream side of the intermediate heat exchanger 7. It can be surely prevented.

(Third Embodiment)
A third embodiment will be described. The third embodiment is a modification of the first embodiment with respect to a part of the control processing executed by the control device 4, and the other aspects are the same as those of the first embodiment, and therefore are different from the first embodiment. Only the part will be described.

FIG. 6 is a flowchart showing a control process executed by the control device 4 included in the refrigeration cycle 1 of the third embodiment. This process is repeatedly executed at predetermined time intervals during the operation of the refrigeration cycle 1.

The operation of the refrigeration cycle 1 is started when the user operates the refrigerator operation switch 21 of the operation panel 20. In step S15, the control device 4 determines whether or not the thermo-off state is changed to the thermo-on state.

When performing the thermostat operation, the control device 4 calculates a first threshold value obtained by adding a first predetermined value to the set temperature and a second threshold value obtained by adding a second predetermined value from the set temperature. The control device 4 stops driving the compressor 5 when the internal temperature detected by the internal temperature sensor 18 becomes equal to or lower than the first threshold value. On the other hand, the control device 4 starts driving the compressor 5 when the internal temperature detected by the internal temperature sensor 18 becomes equal to or higher than the second threshold value. That is, the thermo-off state is a state in which the driving of the compressor 5 is stopped from when the internal cold storage temperature becomes equal to or lower than the first threshold value to equal to or higher than the second threshold value. On the other hand, the thermo-on state is a state in which the compressor 5 is driven from when the internal cold storage temperature becomes equal to or higher than the second threshold value to become equal to or lower than the first threshold value.

When the control device 4 determines that the thermo-off state is switched to the thermo-on state, the control device 4 shifts the processing to step S20. On the other hand, when the thermo-on state continues, the control device 4 determines that the thermo-off state has not been switched to the thermo-on state, and moves the process to step S40. The processing of steps S20 to S50 following step S15 is the same as the processing described in the first embodiment.

The third embodiment described above can also achieve the same operational effects as the first and second embodiments.

(Fourth Embodiment)
A fourth embodiment will be described. The fourth embodiment is a modification of the second embodiment, which is a part of the control processing executed by the control device 4, and is similar to the second embodiment in the other respects, and thus is different from the second embodiment. Only the part will be described.

FIG. 7 is a flowchart showing a control process executed by the control device 4 included in the refrigeration cycle 1 of the fourth embodiment. This process is repeatedly executed at predetermined time intervals during the operation of the refrigeration cycle 1.

The operation of the refrigeration cycle 1 is started when the user operates the refrigerator operation switch 21 of the operation panel 20. In step S15, the control device 4 determines whether or not the thermo-off state is changed to the thermo-on state. When the control device 4 determines that the thermo-off state is switched to the thermo-on state, the control device 4 moves the process to step S20. On the other hand, when the thermo-on state continues, the control device 4 determines that the thermo-off state has not been switched to the thermo-on state, and moves the process to step S40. The processing of steps S20, S35, S40, and S55 following step S15 is the same as the processing described in the second embodiment.

The fourth embodiment described above can also achieve the same effects as the first to third embodiments.

(Fifth Embodiment)
A fifth embodiment will be described. The fifth embodiment differs from the third embodiment in that a part of the control processing executed by the control device 4 is changed, and other aspects are the same as those in the third embodiment. Only the part will be described.

FIG. 8 is a flowchart showing a control process executed by the control device 4 included in the refrigeration cycle 1 of the fifth embodiment. This process is repeatedly executed at predetermined time intervals during the operation of the refrigeration cycle 1.

The operation of the refrigeration cycle 1 is started when the user operates the refrigerator operation switch 21 of the operation panel 20. In step S15, the control device 4 determines whether or not the thermo-off state is changed to the thermo-on state. When the control device 4 determines that the thermo-off state is switched to the thermo-on state, the control device 4 shifts the processing to step S20.

In step S20, the control device 4 calculates the instructed rotation speed of the compressor 5.

In step S21 following step S20, the control device 4 starts changing the rotation speed of the compressor 5 from 0 rpm toward the instructed rotation speed at a predetermined change speed.

In next step S22, the control device 4 determines whether or not the discharge pressure of the compressor 5 is equal to or higher than a predetermined value. As the predetermined value, a value at which the above-mentioned abnormal state may transiently occur is set based on an experiment or the like, and is stored in the control device 4 in advance. When the control device 4 determines that the discharge pressure of the compressor 5 is equal to or higher than the predetermined value, the process proceeds to step S30.

In the process of step S30, the rotation speed of the compressor 5 is changed to a predetermined command rotation speed while suppressing the increase speed of the rotation speed of the compressor 5 as in the first embodiment. After that, the process proceeds to step S36.

On the other hand, when it is determined in step S22 that the discharge pressure of the compressor 5 is lower than the predetermined value, the control device 4 skips step S30 described above and moves the process to step S36.

In step S36, the control device 4 determines whether or not the rotation speed of the compressor 5 has reached the instructed rotation speed. When the control device 4 determines that the rotation speed of the compressor 5 has not reached the instructed rotation speed, the control device 4 repeatedly executes the processing of step S22 or step S30 described above.

When the control device 4 determines in step S36 that the rotation speed of the compressor 5 has reached the designated rotation speed, the control device 4 ends the process once.

In the process of step S15 described above, when the thermo-on state continues, the control device 4 determines that the thermo-off state has not been switched to the thermo-on state, and moves the process to step S40. The processing of steps S40 and S50 is the same as the processing described in the first and third embodiments.

In step S56 following step S50, the control device 4 determines whether or not the rotation speed of the compressor 5 has reached the instructed rotation speed. When the control device 4 determines in step S56 that the rotation speed of the compressor 5 has reached the instructed rotation speed, the control device 4 once ends the processing.

After step S36 or step S56, the processes of steps S15 to S56 described above are executed again after a lapse of a predetermined time.

In the process of step S22 described above, the control device 4 determines whether or not the discharge pressure of the compressor 5 is equal to or higher than a predetermined value, but the value used as the determination reference by the control device 4 is not limited to this. That is, in the process of step S22 described above, the control device 4 selects one of the discharge pressure of the compressor 5, the suction pressure of the compressor 5, the intermediate pressure, the discharge temperature of the compressor 5, the suction temperature of the compressor 5, and the intermediate temperature. Any one of these values or a plurality of values may be used as the criterion. The intermediate pressure is the pressure of the refrigerant flowing in any position of the main circuit 2, and the intermediate temperature is the temperature of the refrigerant flowing in any position of the main circuit 2.

The fifth embodiment described above can also achieve the same operational effects as the first to fourth embodiments.

(Sixth Embodiment)
A sixth embodiment will be described. The sixth embodiment differs from the fifth embodiment in that part of the control processing executed by the control device 4 is changed, and the other aspects are the same as those in the fifth embodiment. Only the part will be described.

FIG. 9 is a flowchart showing a control process executed by the control device 4 included in the refrigeration cycle 1 of the sixth embodiment. This process is repeatedly executed at predetermined time intervals during the operation of the refrigeration cycle 1.

The processing of steps S15, S20, S21, S30, S36, S40, S50 and S56 is the same as the processing described in the fifth embodiment.

In the sixth embodiment, in step S23 subsequent to step S21, the control device 4 determines whether or not the changing speed of the discharge pressure of the compressor 5 is a predetermined value or more. As the predetermined value, a value at which the above-mentioned abnormal state may transiently occur is set based on an experiment or the like, and is stored in the control device 4 in advance. When the control device 4 determines that the change speed of the discharge pressure of the compressor 5 is equal to or higher than the predetermined value, the process proceeds to step S30.

In the process of step S23, the control device 4 determines whether or not the changing speed of the discharge pressure of the compressor 5 is equal to or higher than a predetermined value, but the value used as the determination reference by the control device 4 is not limited to this. .. That is, in the process of step S23 described above, the control device 4 controls the discharge pressure change speed of the compressor 5, the suction pressure change speed of the compressor 5, the intermediate pressure change speed, and the discharge temperature change speed of the compressor 5. Any one of a change rate of the suction temperature of the compressor 5 and a change rate of the intermediate temperature, or a plurality of values may be used as the determination criterion.

The sixth embodiment described above can also achieve the same effects as the first to fifth embodiments.

(Seventh embodiment)
The seventh embodiment will be described. In the seventh embodiment, a part of the control processing executed by the control device 4 is changed from that of the first embodiment, and other parts are the same as those of the first embodiment, and therefore are different from the first embodiment. Only the part will be described.

FIG. 10 is a flowchart showing a control process executed by the control device 4 included in the refrigeration cycle 1 of the seventh embodiment. This process is repeatedly executed at predetermined time intervals during the operation of the refrigeration cycle 1.

The processing of steps S10, S20, S30, S40 and S50 is the same as the processing described in the first embodiment.

In the seventh embodiment, in step S25 subsequent to step S20, the control device 4 determines whether or not the instructed rotation speed calculated in step S20 is equal to or higher than a predetermined value. As the predetermined value, a value at which the above-mentioned abnormal state may transiently occur is set based on an experiment or the like, and is stored in the control device 4 in advance. When determining that the instructed rotation speed is equal to or higher than the predetermined value, the control device 4 moves the process to step S30. On the other hand, when the control device 4 determines that the instructed rotation speed is smaller than the predetermined value, the process proceeds to step S50.

In step S25, the control device 4 determines whether or not the instruction rotational speed calculated in step S20 is equal to or higher than a predetermined value, and the change range of the instruction rotational speed is within the usable range of the compressor 5. You may judge whether it is more than a predetermined ratio. The predetermined ratio is a value that may cause the above-mentioned abnormal state transiently, set based on experiments, and is stored in the control device 4 in advance. In that case, when the control device 4 determines that the variation range of the instructed rotation speed is equal to or more than the predetermined ratio of the usable range of the compressor 5, the process proceeds to step S30. On the other hand, when the control device 4 determines that the variation width of the instructed rotation number is smaller than the predetermined ratio of the usable range of the compressor 5, the process proceeds to step S50.

The seventh embodiment described above can also achieve the same operational effects as the first to sixth embodiments.

(Eighth Embodiment)
The eighth embodiment will be described. In the eighth embodiment, the configuration of the compressor included in the refrigeration cycle 1 is changed from that of the first embodiment, and the other points are the same as those of the first embodiment, and therefore the parts different from the first embodiment will be described. Only explained.

As shown in FIG. 11, in the eighth embodiment, the compressor includes a low stage side compressor 51 and a high stage side compressor 52. Both the low-stage compressor 51 and the high-stage compressor 52 are electric compressors, and the rotation is controlled by the control device 4.

The refrigerant suction port 51a of the low-stage compressor 51 is supplied with refrigerant from a pipe on the accumulator 11 side of the main circuit 2. The refrigerant discharge port 51c of the low-stage compressor 51 and the refrigerant suction port 52a of the high-stage compressor 52 are connected via a pipe. The injection circuit 3 is connected to the merging portion 23 provided in the middle of the pipe. Therefore, the refrigerant suction port 52a of the high-stage compressor 52 is supplied with the refrigerant discharged from the refrigerant discharge port 51c of the low-stage compressor 51 and the refrigerant of the injection circuit 3. The high-stage compressor 52 compresses the intermediate-pressure refrigerant in which those refrigerants are mixed, and discharges it from the refrigerant discharge port 52c toward the condenser 6.

The same effects as those of the first to seventh embodiments can also be obtained with the configuration of the eighth embodiment described above.

(Other embodiments)
The present invention is not limited to the above-described embodiments, but can be appropriately modified within the scope described in the claims. Further, the above embodiments are not unrelated to each other, and can be appropriately combined unless a combination is obviously impossible. Further, in each of the above-mentioned embodiments, it is needless to say that the elements constituting the embodiment are not necessarily indispensable except when explicitly indicated as being indispensable and when it is considered to be indispensable in principle. Yes. Further, in each of the above-mentioned embodiments, when numerical values such as the number of components of the embodiment, numerical values, amounts, ranges, etc. are mentioned, it is clearly limited to a particular number when explicitly stated to be essential. It is not limited to the specific number except for the case where it is done. Further, in each of the above-mentioned embodiments, when referring to the shape of the components and the like, the positional relationship, etc., the shape, unless otherwise explicitly specified and in principle limited to a specific shape, the positional relationship, etc., the shape, It is not limited to the positional relationship or the like.

(1) In each of the above-described embodiments, an example in which the refrigeration cycle 1 is applied to a refrigeration vehicle that transports frozen foods and the like has been described, but the present invention is not limited to this. The refrigeration cycle 1 can be applied to another moving body, a building, and the like.

(2) In each of the above embodiments, the schematic configuration of the refrigeration cycle 1 has been described, but the configuration of the refrigeration cycle 1 is not limited to this. The refrigeration cycle 1 can also have other configurations added to the configurations described in the respective embodiments. For example, the refrigeration cycle 1 may be provided with an oil separator on the downstream side of the compressors 5, 51, 52, and the evaporator 9 may be utilized by utilizing a part of the refrigerant discharged from the compressors 5, 51, 52. You may provide the defrosting apparatus which melts the frost adhering to.

(3) In each of the above-described embodiments, the refrigeration cycle 1 has been described as an example in which the internal temperature sensor 18 detects the internal temperature, but the present invention is not limited to this. The refrigeration cycle 1 may be configured to, for example, estimate the temperature inside the refrigerator from the detection value of the pressure sensor that detects the refrigerant pressure on the refrigerant suction side of the compressors 5 and 51.

(Summary)
According to the first aspect described in part or all of the above-described embodiments, the refrigeration cycle includes a main circuit, an injection circuit, and a control device. In the main circuit, the refrigerant compressed by the compressor is condensed by the condenser, passed through the intermediate heat exchanger, decompressed by the first expansion valve, evaporated by the evaporator, and circulated to the compressor. The injection circuit decompresses the refrigerant diverted from the branch portion provided in the pipe connecting the condenser and the intermediate heat exchanger with the temperature-type second expansion valve, and the refrigerant flowing through the main circuit with the intermediate heat exchanger. After heat exchange, it is injected into the compressor. The temperature-type second expansion valve automatically adjusts the flow path opening degree according to the degree of superheat of the refrigerant flowing downstream from the intermediate heat exchanger. Here, the speed at which the rotation speed of the compressor changes when the rotation speed of the compressor is changed from a rotation speed greater than 0 rpm to a predetermined designated rotation speed is called a normal change speed. The control device makes the changing speed at which the rotating speed of the compressor changes when changing the rotating speed of the compressor from 0 rpm to a predetermined instruction rotating speed slower than the normal changing speed.

According to the second aspect, the control device sets the change speed at which the rotation speed of the compressor changes when changing the rotation speed of the compressor from 0 rpm to a predetermined instruction rotation speed to half or less of the normal change speed. ..

According to this, at the time of starting the compressor, it is possible to make the time required for the rotation speed of the compressor to reach the predetermined instructed rotation speed to be at least twice as long as the time at the normal changing speed. Therefore, it is necessary to secure a sufficient time for the opening degree of the flow path of the temperature-type second expansion valve to correspond to the degree of superheat of the refrigerant detected by the temperature-sensing cylinder provided on the downstream side of the intermediate heat exchanger. You can

According to the third aspect, the refrigeration cycle includes a main circuit, an injection circuit and a control device. In the main circuit, the refrigerant compressed by the compressor is condensed by the condenser, passed through the intermediate heat exchanger, decompressed by the first expansion valve, evaporated by the evaporator, and circulated to the compressor. The injection circuit decompresses the refrigerant diverted from the branch portion provided in the pipe connecting the condenser and the intermediate heat exchanger with the temperature-type second expansion valve, and the refrigerant flowing through the main circuit with the intermediate heat exchanger. After heat exchange, it is injected into the compressor. The temperature-type second expansion valve automatically adjusts the flow passage opening degree according to the degree of superheat of the refrigerant flowing downstream from the intermediate heat exchanger. When changing the rotation speed of the compressor from 0 rpm to a predetermined instruction rotation speed, the control device holds the rotation speed of the compressor at an intermediate rotation speed lower than the predetermined instruction rotation speed for a predetermined time and then from the intermediate rotation speed. The speed is changed to a predetermined designated rotation speed.

According to the fourth aspect, the intermediate rotation speed is in the range of the minimum rotation speed among the rotation speeds of the compressor that can be continuously operated.

According to this, at the time of starting the compressor, while the rotation speed of the compressor is maintained at the intermediate rotation speed, it is possible to maintain the refrigerant pressure of the main circuit at the lowest pressure in the range where the compressor can be continuously operated. It is possible. Therefore, it is possible to more reliably prevent the above-mentioned abnormal state from transiently occurring until the flow path opening degree of the temperature-type second expansion valve corresponds to the superheat degree of the refrigerant flowing on the downstream side of the intermediate heat exchanger. Can be prevented.

In addition, the range of the minimum rotation speed may be the minimum rotation speed at which the compressor can substantially operate, and in addition to the minimum rotation speed indicated in the design of the compressor, about ±10% of the minimum rotation speed. It includes the error range of.

According to the fifth aspect, the compressor has a low-pressure refrigerant suction port to which the refrigerant is supplied from the main circuit and an intermediate-pressure refrigerant suction port to which the refrigerant is supplied from the injection circuit.

According to this, as a compressor corresponding to the injection circuit, a compressor having a low pressure refrigerant suction port and an intermediate pressure refrigerant suction port is exemplified.

According to the sixth aspect, the compressor has a low-stage compressor and a high-stage compressor. Refrigerant is supplied from the main circuit to the low-stage compressor. The high-stage compressor is supplied with the refrigerant discharged from the low-stage compressor and the refrigerant from the injection circuit.

According to this, as a configuration of the refrigeration cycle, a configuration in which an injection circuit is connected to a pipe connecting the low-stage compressor and the high-stage compressor is exemplified.

1 Refrigeration cycle 2 Main circuit 3 Injection circuit 4 Controllers 5, 51, 52 Compressor 6 Condenser 7 Intermediate heat exchanger 8 First expansion valve 9 Evaporator 17 Second expansion valve

Claims (4)

The refrigerant compressed by the compressors (5, 51, 52) is condensed in the condenser (6), passed through the intermediate heat exchanger (7), and then decompressed by the first expansion valve (8) to be an evaporator. A main circuit (2) that is evaporated in (9) and circulates in the compressor;
The flow path opening degree of the refrigerant branched from the branch portion (15) provided in the pipe connecting the condenser and the intermediate heat exchanger is determined according to the degree of superheat of the refrigerant flowing downstream from the intermediate heat exchanger. And an injection circuit (3) for decompressing with a temperature type second expansion valve (17) that is automatically adjusted, heat-exchanged with the refrigerant flowing through the main circuit in the intermediate heat exchanger, and then injecting the heat into the compressor. ,
The rotation speed of the compressor is changed from 0 rpm to a predetermined instruction rotation speed based on a normal change speed at which the rotation speed of the compressor is changed when the rotation speed of the compressor is changed from a rotation speed higher than 0 rpm to a predetermined instruction rotation speed. A control device (4) for slowing down the speed of change of the number of revolutions of the compressor when changing to a number ,
A refrigeration cycle in which the control device sets a change speed at which the rotation speed of the compressor changes when changing the rotation speed of the compressor from 0 rpm to a predetermined instruction rotation speed to half or less of the normal change speed . The refrigerant compressed by the compressors (5, 51, 52) is condensed in the condenser (6), passed through the intermediate heat exchanger (7), and then decompressed by the first expansion valve (8) to be an evaporator. A main circuit (2) that is evaporated in (9) and circulates in the compressor;
The flow path opening degree of the refrigerant branched from the branch portion (15) provided in the pipe connecting the condenser and the intermediate heat exchanger is determined according to the degree of superheat of the refrigerant flowing downstream from the intermediate heat exchanger. And an injection circuit (3) for decompressing with a temperature type second expansion valve (17) that is automatically adjusted, heat-exchanged with the refrigerant flowing through the main circuit in the intermediate heat exchanger, and then injecting the heat into the compressor. ,
When changing the rotation speed of the compressor from 0 rpm to a predetermined instruction rotation speed, after holding the rotation speed of the compressor at an intermediate rotation speed lower than the predetermined instruction rotation speed for a predetermined time, the intermediate rotation speed is changed to a predetermined rotation speed from the predetermined rotation speed. A control device (4) for changing the rotation speed to an instruction speed ,
The intermediate rotation speed is a range of the minimum rotation speed among the rotation speeds at which the compressor can be continuously operated . The compressor (5) has a low-pressure refrigerant suction port (5a) to which a refrigerant is supplied from the main circuit, and an intermediate pressure refrigerant suction port (5b) to which a refrigerant is supplied from the injection circuit. The refrigeration cycle according to claim 1 or 2 . The compressor has a low-stage compressor (51) and a high-stage compressor (52),
Refrigerant is supplied to the low-stage compressor from the main circuit,
Wherein the high-pressure stage compressor, wherein the refrigerant discharged from the low-stage compressor, refrigerant is supplied from the injection circuit, the refrigeration cycle according to claim 1 or 2.

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