JP2008196826A - Refrigerating cycle apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a refrigerating cycle apparatus, exhibiting heat absorbing capability in the whole evaporator to improve the cooling capability of the evaporator while surely preventing the disadvantage that a liquid refrigerant is sucked in a compressor. <P>SOLUTION: This refrigerating cycle apparatus S including a refrigerant circuit formed by sequentially connecting the compressor 1, a radiator 2, an expansion valve 3 and the evaporator 4 by piping, includes: a header 5 connected to the outlet side of the evaporator 4; a first temperature sensor 20 for detecting the refrigerant temperature at an inlet of the evaporator 4; a second temperature sensor 22 for detecting the refrigerant temperature in the header 5; and a control device 30 (a control means) for controlling the valve opening of the expansion valve 3 based on the output of the both temperature sensors 20, 22. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a refrigeration cycle apparatus including a refrigerant circuit in which a compressor, a radiator, an expansion valve, and an evaporator are sequentially connected by piping.

  Conventionally, in this type of refrigeration cycle apparatus, a refrigerant circuit is configured by connecting a compressor, a radiator, an expansion valve, an evaporator, and the like by piping. And the refrigerant | coolant which became high temperature / high pressure by compressing with a compressor is thermally radiated with a heat radiator, and after a pressure falls with an expansion valve, it heat-exchanges with the circumference | surroundings with an evaporator and evaporates. And the refrigerant | coolant which came out of the evaporator repeated the cycle sucked into a compressor again. In such a refrigeration cycle apparatus, in order to prevent the disadvantage that liquid refrigerant returns to the compressor and the compressor is liquid compressed and damaged, the valve opening of the expansion valve is based on the state of the refrigerant flowing into the compressor. It was controlled.

Specifically, temperature sensors (such as temperature measurement thermist) that can detect the refrigerant temperature at the inlet / outlet of the evaporator are installed on the inlet side and the outlet side of the evaporator, respectively, and are detected by each temperature sensor. Based on the refrigerant temperature, the opening degree of the expansion valve is controlled so that the degree of superheat of the refrigerant coming out of the evaporator is sufficiently secured. Moreover, instead of the temperature sensor provided on the outlet side of the evaporator, a temperature sensor is provided immediately before the compressor to control the opening degree of the expansion valve (for example, see Patent Document 1).
JP 2001-241784 A

  When the valve opening degree of the expansion valve is controlled based on the refrigerant temperature at the inlet / outlet of the evaporator as described above, the disadvantage that the liquid refrigerant is sucked into the compressor can be eliminated, but the temperature provided at the outlet side of the evaporator Since the refrigerant is controlled to be in a gas (gas) state before reaching the sensor, the refrigerant is often in a gas state in the vicinity of the outlet in the evaporator, and the entire evaporator exhibits heat absorption capability. I couldn't let you. Even if the temperature sensor is provided immediately before the compressor instead of the temperature sensor provided on the outlet side of the evaporator and the expansion valve is controlled, the refrigerant remains in the refrigerant until the outlet of the evaporator. Alternatively, it was not possible to determine whether the gas was already in the vicinity of the outlet in the evaporator 4. Therefore, it has been difficult to exert endothermic ability in the entire evaporator.

  The present invention has been made to solve the problems of the related art, and while reliably preventing the inconvenience of the liquid refrigerant being sucked into the compressor, the evaporator exhibits the heat absorption capability, and the evaporator An object of the present invention is to provide a refrigeration cycle apparatus capable of improving the cooling capacity.

  The refrigeration cycle apparatus of the present invention includes a refrigerant circuit formed by sequentially connecting a compressor, a radiator, an expansion valve, and an evaporator, and includes a header connected to the outlet side of the evaporator, and an evaporator A first temperature sensor that detects the refrigerant temperature at the inlet, a second temperature sensor that detects the refrigerant temperature at the header or the refrigerant temperature at the header outlet, and the valve opening of the expansion valve based on the outputs of both the temperature sensors And control means for controlling.

  In the refrigeration cycle apparatus according to the second aspect of the present invention, the control means determines the degree of superheat of the refrigerant in the evaporator based on the outputs of the two temperature sensors. When the degree of superheating is small, the opening degree of the expansion valve is reduced.

  According to a third aspect of the present invention, there is provided a refrigeration cycle apparatus comprising an internal heat exchanger for exchanging heat between the refrigerant that has exited the radiator and the refrigerant that has exited the header.

  A refrigeration cycle apparatus according to a fourth aspect of the invention is characterized in that carbon dioxide is used as a refrigerant in the invention according to any one of the first to third aspects.

  According to the present invention, in a refrigeration cycle apparatus including a refrigerant circuit formed by sequentially connecting a compressor, a radiator, an expansion valve, and an evaporator, a header connected to the outlet side of the evaporator, and an evaporator inlet The first temperature sensor that detects the refrigerant temperature, the second temperature sensor that detects the refrigerant temperature in the header or the refrigerant temperature at the header outlet, and the valve opening degree of the expansion valve based on the outputs of both the temperature sensors For example, as in the second aspect of the present invention, the control means determines the degree of superheat of the refrigerant in the evaporator based on the outputs of the two temperature sensors, and if the degree of superheat is large, the expansion valve If the valve opening of the expansion valve is enlarged and the valve opening of the expansion valve is reduced when the degree of superheat is small, it can be controlled to an optimum state so that liquid refrigerant comes to the evaporator outlet. As a result, the cooling capacity can be improved by exhibiting endothermic capacity in the entire evaporator. Furthermore, power consumption can be reduced by improving the cooling capacity of the evaporator.

  Further, in the invention of claim 3, since the internal heat exchanger for exchanging heat between the refrigerant exiting the radiator and the refrigerant exiting the header in each of the above inventions is provided, the refrigerant exiting from the radiator is exchanged with the internal heat exchanger. It can be cooled by exchanging heat with the refrigerant that has left the header. As a result, the cooling capacity can be further improved.

  In particular, the header is connected to the outlet side of the evaporator, and the refrigerant that has flowed out of the header flows into the internal heat exchanger. Can be stabilized.

  Furthermore, even if liquid refrigerant is mixed with the refrigerant from the header, it can be evaporated by the internal heat exchanger, so the liquid refrigerant is sucked into the compressor. Thus, the inconvenience of the liquid compression by the compressor can be surely eliminated.

  In the refrigeration cycle apparatus according to any one of claims 1 to 3, the cooling capacity can be improved even when carbon dioxide is used as the refrigerant as in claim 4.

  The present invention, in a refrigeration cycle apparatus having a refrigerant circuit comprising a compressor, a radiator, an expansion valve, and an evaporator connected in sequence, reliably eliminates the disadvantage that liquid refrigerant is sucked into the compressor, It was made to solve the problem that it was difficult to achieve an optimal state in which liquid refrigerant came to the outlet of the evaporator. The header connected to the outlet side of the evaporator and the refrigerant at the inlet of the evaporator, aiming to improve the cooling capacity by demonstrating the endothermic capacity of the entire evaporator while reliably preventing the disadvantage of liquid compression of the compressor The first temperature sensor for detecting the temperature, the second temperature sensor for detecting the refrigerant temperature at the header or the refrigerant temperature at the header outlet, and the opening degree of the expansion valve are controlled based on the outputs of the two temperature sensors. This is realized by providing control means. Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a refrigerant circuit diagram of a refrigeration cycle apparatus according to an embodiment of the present invention. The refrigeration cycle apparatus S is composed of a refrigerant circuit in which a compressor 1, a radiator 2, an expansion valve 3, an evaporator 4 and the like are sequentially connected by piping. The refrigeration cycle apparatus S of the present embodiment is used, for example, for cooling purposes such as a refrigerator. Therefore, the evaporator 4 is installed so that the inside of the refrigerator can be cooled.

  The compressor 1 of the embodiment is a multi-stage (two-stage) compression type composed of an electric element (not shown) as a driving element, and a first compression element 1A and a second compression element 1B driven by the electric element. A refrigerant introduction pipe 10 for introducing a refrigerant into the first compression element 1A is connected to the suction side (inlet side) of the first compression element 1A which is a compressor and is in a low stage.

  Further, the discharge side (exit side) of the first compression element 1A and the suction side (inlet side) of the second compression element 1B which is a higher stage are connected by a refrigerant introduction pipe 11, and this refrigerant introduction pipe 11 is arrange | positioned so that the intermediate cooler 8 comprised outside the compressor 1 may be passed. The intermediate cooler 8 is for cooling the refrigerant sucked into the second compression element 1B after being compressed by the first compression element 1A. That is, the refrigerant compressed to the intermediate pressure by the first compression element 1A is cooled by the intermediate cooler 8, and then sucked into the second compression element 1B. Then, one end of the refrigerant discharge pipe 12 is connected to the discharge side of the second compression element 1B, and the refrigerant compressed by the compressor 1 is discharged from here.

  The other end of the refrigerant discharge pipe 12 is connected to the inlet of the radiator 2. The refrigerant pipe 13 connected to the outlet of the radiator 2 reaches the expansion valve 3 through the internal heat exchanger 7. The expansion valve 3 is constituted by an electric expansion valve whose throttle amount is controlled stepwise (step control) from a fully closed state to a fully open state by a control device 30 as control means of the refrigeration cycle apparatus S. The refrigerant pipe 14 exiting from the expansion valve 3 is connected to the inlet of the evaporator 4, and the refrigerant pipe 15 exiting from the evaporator 4 is connected to an inlet 42 of the header 5 described later. In addition, the refrigerant introduction pipe 10 of the compressor 1 is connected to the outlet 43 of the header 5, thereby forming an annular refrigerant circuit.

  Further, the internal heat exchanger 7 is heat for exchanging heat between the high-pressure side refrigerant flowing out of the radiator 2 and flowing through the refrigerant pipe 13 and the low-pressure side refrigerant flowing out of the header 5 and flowing through the refrigerant introduction pipe 10. It is an exchanger. In the figure, reference numeral 17 denotes a check valve. The check valve 17 is a midway portion of the refrigerant introduction pipe 10 with the suction side (first compression element 1A side) of the compressor 1 as a forward direction, and internal heat exchange. It is interposed downstream of the refrigerant in the vessel 7.

In the refrigerant circuit, CO ₂ (carbon dioxide), which is a natural refrigerant, is used as a refrigerant, which is friendly to the global environment and takes into consideration flammability and toxicity. In the present embodiment, the carbon dioxide refrigerant is compressed to a supercritical state, and is not condensed in the radiator 2. Therefore, only the temperature of the refrigerant is reduced, and the decompression in the expansion valve 3 reduces the pressure from the supercritical state to the gas phase (gas ) / Change to a two-phase mixed state in which liquid phases are mixed.

  By the way, in such a refrigeration cycle apparatus S, the refrigerant is not completely evaporated in the evaporator 4, and the liquid state refrigerant (liquid phase refrigerant) remains, and the liquid state refrigerant remains mixed. When returning to the compressor 1, the compressor 1 is liquid-compressed and damaged, so the refrigerant sucked into the compressor 1 needs to be surely in a gaseous state. Therefore, based on the refrigerant temperature of the evaporator 4, the valve opening degree of the expansion valve 3 must be controlled to ensure a sufficient degree of superheat of the refrigerant sucked into the compressor 1.

  In this case, in the conventional refrigeration cycle apparatus, as shown in FIG. 8, temperature sensors 20 and 25 each comprising a temperature measurement thermistor are attached to a pipe 14 on the inlet side of the evaporator 4 and a pipe 15 on the outlet side of the evaporator 4, respectively. The opening degree of the expansion valve 3 is controlled based on the temperature of the refrigerant detected by the temperature sensors 20 and 25.

  Specifically, when the refrigerant is completely evaporated in the evaporator 4 and the refrigerant discharged from the evaporator 4 is completely gas, the refrigerant temperature detected by the temperature sensor 25 becomes high. That is, the temperature difference between the refrigerant detected by the temperature sensor 20 and the refrigerant detected by the temperature sensor 25 increases. On the other hand, when the refrigerant is not completely evaporated by the evaporator 4 and the liquid state refrigerant is mixed, the refrigerant temperature detected by the temperature sensor 25 is low. That is, the temperature difference between the refrigerant detected by the temperature sensor 20 and the refrigerant detected by the temperature sensor 25 is reduced.

  Therefore, in the conventional refrigeration cycle apparatus, based on the output of the refrigerant temperature detected by the temperature sensor 20 and the temperature sensor 25 by the control device (control means), the refrigerant detected by both the temperature sensors 20 and 25 is changed. The opening degree of the expansion valve 3 is controlled so that the temperature difference becomes large, and the refrigerant is completely evaporated by the evaporator 4, thereby reliably preventing liquid compression of the compressor 1.

  However, when the expansion valve 3 is controlled as described above, the refrigerant exiting the evaporator 4 can be completely in the gaseous state, but the refrigerant is already in the gaseous state near the outlet in the evaporator 4, The entire evaporator 4 could not exhibit the endothermic ability.

  Further, in place of the temperature sensor 25 provided on the outlet side of the evaporator 4, a temperature sensor is provided on the suction side of the compressor 1 (the refrigerant introduction pipe 10 on the outlet side of the internal heat exchanger 7 in FIG. 8). Even if the expansion valve 3 is controlled based on the refrigerant temperature detected by the temperature sensor 20 at the inlet of the evaporator 4, the refrigerant sucked into the compressor 1 is controlled to be completely gas as described above. However, it was impossible to determine whether or not the refrigerant was in the liquid state in the evaporator 4 up to the vicinity of the outlet. Accordingly, in this case as well, it is difficult to exhibit the endothermic capacity in the entire evaporator 4.

  Therefore, in the present invention, the header 5 on the outlet side of the evaporator 4, the first temperature sensor (temperature measurement thermistor) for detecting the refrigerant temperature at the evaporator inlet, the refrigerant temperature in the header 5, or the header A second temperature sensor (such as a temperature measurement thermistor) that detects the refrigerant temperature at the five outlets is provided, and the valve opening degree of the expansion valve 3 is controlled based on the outputs of both temperature sensors.

  Specifically, in this embodiment, the temperature sensor 25 for detecting the outlet temperature of the evaporator 4 is eliminated, a header 5 is provided on the outlet side of the evaporator 4, and a temperature for newly detecting the refrigerant temperature in the header 5 is provided. While installing the sensor 22 (second temperature sensor), the control device 30 controls the valve of the expansion valve 3 based on the temperature sensor 20 (first temperature sensor) on the inlet side of the evaporator 4 and the output of the temperature sensor 22. The opening degree is controlled stepwise (step control).

  The header 5 can store the refrigerant in the liquid state from the evaporator 4. The header 5 of the embodiment is composed of a vertically long cylindrical container 40, and an inlet 42 is formed at a substantially center in the axial direction of the bottom surface 40 </ b> B of the container 40, and the inlet 42 has the evaporator 4. A refrigerant pipe 15 connected to the outlet is connected, and one end of the refrigerant pipe 15 is above the inside of the container 40 and opens at a position above the liquid level of the liquid refrigerant stored in the container 40. ing. Further, an outlet 43 is formed at the approximate center of the top surface 40T of the container 40 in the axial direction. The outlet 43 is connected to the refrigerant introduction pipe 10 that reaches the suction side of the first compression element 1 </ b> A of the compressor 10.

  As a result, of the refrigerant that has flowed into the container 40 of the header 5 from the refrigerant pipe 15 connected to the inlet 42, the liquid refrigerant is stored in the container 40, and only the gaseous refrigerant is connected to the outlet 43. The refrigerant is introduced from the header 5 through the refrigerant introduction pipe 10.

  The temperature sensor 20 is provided between the outlet of the expansion valve 3 and the inlet of the evaporator 4 or immediately after entering the evaporator 4. The temperature sensor 20 according to the present embodiment is attached to the middle portion of the refrigerant pipe 14 that connects the outlet of the expansion valve 3 and the inlet of the evaporator 4 in a heat exchange manner. As shown in FIG. 2, the temperature sensor 22 of the present embodiment is a position directly above the opening 15A of the refrigerant pipe 15 connected to the inlet of the container 40 of the header 5, that is, the liquid stored in the header 5. A heat exchanger is attached to the side surface of the container 40 above the maximum liquid level of the refrigerant. Therefore, the temperature sensor 22 substantially detects the refrigerant temperature in the header 5 from the temperature of the header 5 itself cooled by the refrigerant flowing into the header 5. In this case, the internal heat exchanger 7 is located on the refrigerant downstream side of the temperature sensor 22.

  Here, based on the refrigerant temperature detected by the temperature sensors 20 and 22, the control device 30 controls the valve opening degree of the expansion valve 3 stepwise (step control). Specifically, the control device 30 determines the degree of superheat of the refrigerant in the evaporator 4 based on the outputs of both the temperature sensors 20 and 22, and expands the valve opening of the expansion valve when the degree of superheat is large, When the degree is small, the opening degree of the expansion valve is reduced.

  In this case, the header 5 is provided as in the present invention, and the temperature sensor 22 is attached to the header 5 and the refrigerant temperature in the header 5 is detected, so that the expansion valve 3 is opened according to the presence or absence of liquid refrigerant in the header 5. You will be able to control the degree. That is, when the refrigerant discharged from the evaporator 4 is almost in a gaseous state, the liquid refrigerant in the header 5 is little or disappears, so that the refrigerant temperature in the header 5 increases accordingly. As a result, the temperature difference between the refrigerant entering the evaporator 4 and the refrigerant in the header 5 increases. On the other hand, when the refrigerant discharged from the evaporator 4 is in a gas-liquid mixed state and the liquid content increases, the amount of liquid in the header 5 increases, and the refrigerant entering the evaporator 4 and the refrigerant in the header 5 The temperature difference from

  Therefore, based on the temperature difference between the refrigerant in the header 5 detected by the temperature sensor 22 and the refrigerant at the inlet of the evaporator 4 detected by the temperature sensor 20, a predetermined amount of liquid refrigerant accumulates in the header 5. It is assumed that the opening degree of the expansion valve 3 is controlled by the control device 30 so as to be in the state. That is, the temperature difference between the refrigerant detected by the temperature sensor 22 and the refrigerant detected by the temperature sensor 20 is within a predetermined range where a predetermined amount of liquid refrigerant is accumulated in the header 5, that is, a predetermined upper limit value. It is set in advance so as to be between Tmax and a predetermined lower limit value Tmin, and the valve opening degree of the expansion valve 3 is controlled by the control device 30 so as to be within the set range. Specific control of the expansion valve 3 will be described in detail later.

  Next, the operation of the refrigeration cycle apparatus S of the present embodiment will be described with reference to the ph diagram (Mollier diagram) of FIG. First, when the power of the refrigeration cycle apparatus S is turned on, the control device 30 energizes an electric element (not shown) of the compressor 1. Thereby, the first and second compression elements 1A and 1B are driven, and the low-temperature and low-pressure refrigerant from the evaporator 4 is sucked into the first compression element 1A from the refrigerant introduction pipe 10 (state A in FIG. 3). ). The refrigerant sucked into the first compression element 1A is compressed to an intermediate pressure and discharged to the refrigerant introduction pipe 11 (state B in FIG. 3). The intermediate pressure refrigerant discharged to the refrigerant introduction pipe 11 is cooled in the process of passing through the intermediate cooler 5 (state C in FIG. 3). Thereby, since the refrigerant | coolant suck | inhaled by the 2nd compression element 1B can be cooled, the compression efficiency in the 2nd compression element 1B can be improved. Furthermore, the temperature increase of the refrigerant compressed and discharged by the second compression element 1B can be suppressed, and the cooling capacity (refrigeration capacity) in the evaporator 4 can be improved.

  The refrigerant cooled by the intercooler 5 and brought into the state of C in FIG. 3 is sucked into the second compression element 1B and is compressed in the second stage to become high-temperature and high-pressure refrigerant gas, and the refrigerant discharge pipe 12 Further, it is discharged to the outside of the compressor 1. At this time, the refrigerant is compressed to an appropriate supercritical pressure (state D in FIG. 3). The refrigerant discharged from the compressor 1 flows into the radiator 2 through the refrigerant discharge pipe 12 and radiates heat there (state E in FIG. 3). Then, the refrigerant exits the radiator 2 and enters the refrigerant pipe 13 to enter the internal heat exchanger. Pass 7

  The high-pressure side refrigerant discharged from the radiator 2 flowing through the refrigerant pipe 13 in the process of flowing through the internal heat exchanger 7 exchanges heat with the low-pressure side refrigerant discharged from the header 5. As a result, the high-pressure side refrigerant flowing through the refrigerant pipe 13 is further cooled by being deprived of heat by the low-pressure side refrigerant flowing through the refrigerant introduction pipe 10 (state F in FIG. 3).

  Due to the presence of the internal heat exchanger 7, the refrigerant on the high-pressure side that has passed through the radiator 2 is deprived of heat by the refrigerant on the low-pressure side and is cooled, so that the state from E to F in FIG. Therefore, the degree of supercooling of the refrigerant increases, and the entropy difference in the evaporator 4 can be expanded. Thereby, the cooling capacity in the evaporator 4 can be improved.

  The refrigerant that has been cooled by the internal heat exchanger 7 and has reached the state of F in FIG. 3 reaches the expansion valve 3. Then, the pressure of the refrigerant is reduced by the pressure reducing action in the expansion valve 3 (state G in FIG. 3), and in this state, the refrigerant flows into the evaporator 4 and evaporates, and exhibits a cooling action by absorbing heat from the surrounding air. (State H in FIG. 3). The refrigerant evaporated in the evaporator 4 flows into the header 5. At this time, the refrigerant discharged from the evaporator 4 is not in a completely gaseous state but in a two-phase mixed state in which liquid is mixed, and the liquid phase component of this refrigerant is separated in the header 5 and is stored in the container 40 of the header 5. Stored.

  The gas phase refrigerant separated from the liquid phase component flows into the refrigerant introduction pipe 10 connected to the inside of the container 40 and passes through the internal heat exchanger 7. Then, the low-pressure side refrigerant flowing through the refrigerant introduction pipe 10 in the process of flowing through the internal heat exchanger 7 exchanges heat with the high-pressure side refrigerant coming out of the radiator 2 flowing through the refrigerant pipe 13 described above. As a result, the low-pressure side refrigerant flowing through the refrigerant introduction pipe 10 takes heat from the high-pressure side refrigerant flowing through the refrigerant pipe 13 and is subjected to the heating action to be in the state of FIG. The refrigerant heated by the internal heat exchanger 7 repeats the cycle of being sucked into the first compression element 1A of the compressor 1.

  Next, the valve opening degree control of the expansion valve 3 during the operation will be described in detail with reference to FIG. First, as described above, when energization of the compressor 1 is started by the control device 30 (step S1 in FIG. 4), the control device 30 proceeds to step S2 and detects the outputs of the temperature sensors 20 and 22. That is, the temperature sensor 20 detects the refrigerant temperature (evaporator inlet temperature) Te entering the evaporator 4, and the temperature sensor 22 detects the refrigerant temperature (header side temperature) Th in the header 5.

  If each temperature sensor 20 and 22 detect each refrigerant | coolant temperature Te and Th as mentioned above, the control apparatus 30 will transfer to step S3 next, and will calculate a superheat degree. That is, the control device 30 calculates the superheat degree SH from the respective refrigerant temperatures Th and Te detected in step S2. Specifically, the control device 30 calculates the difference (SH = Th−Te) between the refrigerant temperature Te entering the evaporator 4 and the refrigerant temperature Th in the header 5.

  Next, the control device 30 proceeds to step S4, and compares the degree of superheat SH calculated in step S3 with the predetermined upper limit value Tmax set in advance as described above. When the degree of superheat SH is higher than the upper limit value Tmax, the control device 30 proceeds to step S5 and expands the valve opening degree of the expansion valve 3. That is, that the degree of superheat SH is higher than the upper limit value Tmax means that there is no liquid in the header 5 and the refrigerant near the outlet of the evaporator 4 is almost in a gaseous state.

  Therefore, when it is determined in step S4 that the superheat degree SH is higher than the upper limit value Tmax as described above, the control device 30 proceeds to step S5 and increases the valve opening degree of the expansion valve 3. Specifically, the control device 30 of the present embodiment opens the expansion valve 3 for a predetermined step (for example, one step), and then returns to step S2. Thus, when the degree of superheat SH is higher than the upper limit value Tmax, the amount of throttle of the expansion valve 3 is reduced by increasing the valve opening degree of the expansion valve 3, and more refrigerant flows through the evaporator 4. .

  On the other hand, when the superheat degree SH is equal to or lower than the upper limit value Tmax in step S4, the control device 30 next proceeds to step S6, and compares the superheat degree SH with a predetermined lower limit value Tmin. If the degree of superheat SH is lower than the lower limit value Tmin, the control device 30 proceeds to step S7 and reduces the valve opening of the expansion valve 3. That is, the fact that the degree of superheat SH is lower than the lower limit value Tmin means that the amount of liquid in the refrigerant exiting the evaporator 4 is large and the amount of liquid in the header 5 is excessive. In this case, the liquid refrigerant may not be separated by the header 5, and the liquid refrigerant may flow into the refrigerant into the refrigerant introduction pipe 10.

  Therefore, when it is determined in step S6 that the degree of superheat SH is lower than the lower limit value Tmin as described above, the control device 30 proceeds to step S7 and reduces the valve opening of the expansion valve 3. Specifically, the control device 30 of the present embodiment closes the expansion valve 3 for a predetermined step (for example, one step), and then returns to step S2. Thus, when the degree of superheat SH is lower than the lower limit value Tmin, the throttle opening of the expansion valve 3 is reduced, so that the throttle amount of the expansion valve 3 increases and the amount of refrigerant flowing to the evaporator 4 decreases. The liquid content of the refrigerant coming out of the evaporator 4 can be reduced.

  On the other hand, if the degree of superheat SH is equal to or greater than the lower limit value Tmin in step S6, the optimal state in which the liquid refrigerant has reached the outlet of the evaporator 4 and a predetermined amount of liquid refrigerant has accumulated in the header 5 It means that. Therefore, when the superheat degree SH is not less than the lower limit value Tmin in step S6, the control device 30 proceeds to step S8, maintains the valve opening degree of the expansion valve 3 (with the expansion valve 3 as it is), and Return to step S2. Then, the control device 30 repeatedly executes the control operation from the start of the power supply until it stops.

  As described in detail above, the header 5, the temperature sensor 20 that detects the refrigerant temperature at the inlet of the evaporator 4, and the temperature sensor 22 that detects the refrigerant temperature in the header 5 are provided on the outlet side of the evaporator 4, The control device 30 determines the superheat degree SH of the refrigerant in the evaporator 4 based on the outputs of the temperature sensors 20 and 22, and when the superheat degree SH is larger than a predetermined upper limit value Tmax, the expansion valve 3 is opened. When the degree of superheat SH is smaller than the predetermined lower limit value Tmin, the opening degree of the expansion valve 3 is reduced so that liquid refrigerant comes to the outlet of the evaporator 4 as described above. It can be controlled to an optimum state.

  Thereby, the heat absorption capability can be exhibited in the entire evaporator 4 and the cooling capability can be improved. Further, the power consumption can be reduced by improving the cooling capacity of the evaporator 4.

  Further, by providing an internal heat exchanger 7 for exchanging heat between the refrigerant that has exited the radiator 2 and the refrigerant that has exited the header 5, the header 5 is removed from the refrigerant that has exited the radiator 2 by the internal heat exchanger 7. It can be cooled by exchanging heat with the refrigerant. Thereby, the cooling capacity can be further improved. In particular, the header 5 is connected to the outlet side of the evaporator 4, and the refrigerant flowing out of the header 5 is caused to flow into the internal heat exchanger 7, so that the refrigerant that has passed through the header flowing into the internal heat exchanger 7 is usually gaseous. Therefore, the heat exchange in the internal heat exchanger 7 is stabilized, so that the state of the refrigerant flowing in the refrigerant circuit can be stabilized.

  Furthermore, by providing the internal heat exchanger 7 on the refrigerant downstream side of the temperature sensor 22 as in the present embodiment, even if liquid refrigerant is mixed in the refrigerant from the header 5, the internal heat exchange is performed. Since it can be evaporated in the vessel 7, the disadvantage that the liquid refrigerant is sucked into the compressor 1 and the compressor 1 performs liquid compression can be surely eliminated.

  Furthermore, even when carbon dioxide refrigerant is used as the refrigerant of the refrigeration cycle apparatus as in this embodiment, sufficient cooling capacity can be obtained by the present invention. Therefore, the refrigeration cycle apparatus using the carbon dioxide as a refrigerant as in this embodiment can be used for cooling purposes such as a refrigerator, and the versatility of the refrigeration cycle apparatus can be enhanced.

  In the present embodiment, the description has been given using the two-stage compression compressor 1 including the first compression element 1A and the second compression element 1B as the compressor. However, the compressor is a two-stage compressor as in the embodiment. The compressor is not limited to a compressor having a compression element, and a compressor having three, four, or more compression element elements may be applied. Further, it is also possible to use a single stage compressor 1 as shown in FIG.

  Next, another embodiment of the present invention will be described with reference to FIG. In FIG. 6, the same reference numerals as those in FIGS. 1 to 5 have the same or similar effects or actions, and thus the description thereof is omitted here.

  In the said Example (Example 1), the temperature sensor 22 is installed in the side surface of the header 5, the refrigerant | coolant temperature in the header 5 is detected with the temperature sensor 22, and the output of both temperature sensors 20 and 22 is made into the control apparatus 30. The valve opening degree of the expansion valve 3 is controlled based on this, but in this embodiment, instead of the temperature sensor 22 of the first embodiment, a temperature sensor for detecting the refrigerant temperature at the outlet of the header 5 as shown in FIG. 23 (second temperature sensor) is installed, and the control device 30 controls the valve opening degree of the expansion valve 3 based on the outputs of the temperature sensors 20 and 23.

  That is, the temperature sensor 23 of the present embodiment is attached to the middle of the refrigerant introduction pipe 10 connected to the outlet of the header 5 in a heat exchange manner. Therefore, the temperature sensor 23 substantially detects the temperature of the refrigerant that has exited the header 5 from the temperature of the refrigerant introduction pipe 10 that has been cooled by the refrigerant that has exited the header 5.

  In this case, the control device 30 controls the valve opening degree of the expansion valve 3 stepwise (step control) based on the refrigerant temperature detected by the temperature sensors 20 and 23. . Specifically, the control device 30 determines the degree of superheat of the refrigerant in the evaporator 4 based on the outputs of both the temperature sensors 20 and 23, and when the degree of superheat is large, the valve opening of the expansion valve is increased, When the degree is small, the opening degree of the expansion valve is reduced.

  As in this embodiment, the temperature sensor 23 is attached to the refrigerant introduction pipe 10 connected to the outlet of the header 5 and the temperature of the refrigerant discharged from the header 5 is detected to determine the presence or absence of liquid refrigerant in the header 5. be able to. That is, when the refrigerant discharged from the evaporator 4 is almost in a gaseous state, the liquid refrigerant in the header 5 is little or disappears, so that the temperature of the refrigerant flowing in the refrigerant introduction pipe 10 is increased accordingly. As a result, the temperature difference between the refrigerant entering the evaporator 4 and the refrigerant at the outlet of the header 5 (the refrigerant flowing through the refrigerant introduction pipe 10) increases. On the other hand, when the liquid refrigerant is stored in the header 5 and the refrigerant flowing in the refrigerant introduction pipe 10 is in a gaseous state, the refrigerant entering the evaporator 4 and the refrigerant at the outlet of the header 5 (that is, The temperature difference with the refrigerant flowing in the refrigerant introduction pipe 10 becomes smaller than the above. Furthermore, when the amount of liquid in the header 5 becomes excessive and liquid components are mixed in the refrigerant flowing in the refrigerant introduction pipe 10, the temperature difference between the refrigerant entering the evaporator 4 and the refrigerant at the outlet of the header 5 is further reduced. Become.

  As described above, a temperature difference is generated between the refrigerant detected by the temperature sensor 20 and the refrigerant detected by the temperature sensor 23 depending on the state of the refrigerant at the outlet of the header 5 and the state in the header 5. In consideration of the above, by controlling the valve opening degree of the expansion valve 3, an optimal state in which the refrigerant in the liquid state comes to the outlet of the evaporator 4 and is in the gaseous state at the inlet of the compressor 1. can do.

  Therefore, in this embodiment, based on the difference between the refrigerant temperature at the outlet of the header 5 detected by the temperature sensor 23 and the refrigerant temperature at the inlet of the evaporator 4 detected by the temperature sensor 20, the temperature difference is transferred to the header 5. In a state where liquid refrigerant is accumulated and the refrigerant opening pipe 10 provided with such a temperature sensor 23 controls the valve opening degree of the expansion valve 3 by the control device 30 so that the refrigerant is in a gaseous state. And That is, the temperature difference between the refrigerant detected by the temperature sensor 23 and the refrigerant detected by the temperature sensor 20 is a state where a predetermined amount of liquid refrigerant is accumulated in the header 5, and the refrigerant is introduced into the refrigerant introduction pipe 10. Is set in advance so as to be within a predetermined range in which the gas becomes a gas, that is, between a predetermined upper limit value Tmax and a predetermined lower limit value Tmin, and is expanded by the control device 30 so as to be within the set range. It is assumed that the valve opening degree of the valve 3 is controlled.

  Here, the valve opening degree control of the expansion valve 3 will be described in detail. Since the operation of the refrigeration cycle apparatus S is the same as that of the first embodiment, description thereof is omitted here. The valve opening control of the expansion valve 3 will be described with reference to FIG. 4 used in the first embodiment.

  First, when the control device 30 starts energizing the compressor 1 (step S1 in FIG. 4) as in the above embodiment, the control device 30 proceeds to step S2 and detects the outputs of the temperature sensors 20, 23. That is, the temperature sensor 20 detects the refrigerant temperature (evaporator inlet temperature) Te entering the evaporator 4 and the temperature sensor 23 detects the refrigerant temperature (header side temperature) Th at the outlet of the header 5 flowing through the refrigerant introduction pipe 10. Is detected.

  If each temperature sensor 20 and 23 detect each refrigerant | coolant temperature Te and Th as mentioned above, the control apparatus 30 will transfer to step S3 next, and will calculate a superheat degree. That is, the control device 30 calculates the superheat degree SH from the respective refrigerant temperatures Th and Te detected in step S2. Specifically, the control device 30 calculates the difference (SH = Th−Te) between the refrigerant temperature Te entering the evaporator 4 and the refrigerant temperature Th coming out of the header 5.

  Next, the control device 30 proceeds to step S4, and compares the degree of superheat SH calculated in step S3 with the predetermined upper limit value Tmax set in advance as described above. When the degree of superheat SH is higher than the upper limit value Tmax, the control device 30 proceeds to step S5 and expands the valve opening degree of the expansion valve 3. That is, the fact that the degree of superheat SH is higher than the upper limit value Tmax means that there is no liquid in the header 5 and the refrigerant near the outlet of the evaporator 4 is almost in a gaseous state.

  Therefore, when it is determined in step S4 that the superheat degree SH is higher than the upper limit value Tmax as described above, the control device 30 proceeds to step S5 and increases the valve opening degree of the expansion valve 3. Specifically, the control device 30 of the present embodiment opens the expansion valve 3 for a predetermined step (for example, one step), and then returns to step S2. Thus, when the degree of superheat SH is higher than the upper limit value Tmax, the amount of throttle of the expansion valve 3 is reduced by increasing the valve opening degree of the expansion valve 3, and more refrigerant flows through the evaporator 4. .

  On the other hand, when the superheat degree SH is equal to or lower than the upper limit value Tmax in step S4, the control device 30 next proceeds to step S6, and compares the superheat degree SH with a predetermined lower limit value Tmin. If the degree of superheat SH is lower than the lower limit value Tmin, the control device 30 proceeds to step S7 and reduces the valve opening of the expansion valve 3. That is, the fact that the degree of superheat SH is lower than the lower limit value Tmin means that the amount of refrigerant in the evaporator 4 is large, the amount of liquid in the header 5 becomes excessive, and the liquid refrigerant in the header 5 cannot be separated. This means that liquid refrigerant may be mixed in the refrigerant passing through the refrigerant introduction pipe 10.

  Therefore, when it is determined in step S6 that the degree of superheat SH is lower than the lower limit value Tmin as described above, the control device 30 proceeds to step S7 and reduces the valve opening of the expansion valve 3. Specifically, the control device 30 of the present embodiment closes the expansion valve 3 for a predetermined step (for example, one step), and then returns to step S2. Thus, when the degree of superheat SH is lower than the lower limit value Tmin, the throttle opening of the expansion valve 3 is reduced, so that the throttle amount of the expansion valve 3 increases and the amount of refrigerant flowing to the evaporator 4 decreases. The liquid content of the refrigerant coming out of the evaporator 4 can be reduced.

  On the other hand, if the degree of superheat SH is equal to or greater than the lower limit value Tmin in step S6, the liquid state refrigerant comes to the outlet of the evaporator 4 and the gas is in the gaseous state at the inlet of the compressor 1. Means. Therefore, when the superheat degree SH is not less than the lower limit value Tmin in step S6, the control device 30 proceeds to step S8, maintains the valve opening degree of the expansion valve 3 (with the expansion valve 3 as it is), and Return to step S2. And the control apparatus 30 repeatedly performs this control operation until it stops from the starting of a power supply.

  As described above in detail, the header 5, the temperature sensor 20 that detects the refrigerant temperature at the inlet of the evaporator 4, and the temperature sensor 23 that detects the refrigerant temperature at the outlet of the header 5 are provided on the outlet side of the evaporator 4. The control device 30 determines the superheat degree SH of the refrigerant in the evaporator 4 based on the outputs of the temperature sensors 20 and 23. If the superheat degree SH is larger than the predetermined upper limit value Tmax, the valve of the expansion valve 3 is determined. When the opening degree is increased and the degree of superheat SH is smaller than the predetermined lower limit value Tmin, the same effect as in the above embodiment can be obtained by reducing the valve opening degree of the expansion valve 3.

  That is, also in the case of the present embodiment, it is possible to control to an optimum state in which the liquid refrigerant comes to the outlet of the evaporator 4. Thereby, the heat absorption capability can be exhibited in the entire evaporator 4 and the cooling capability can be improved. Further, the power consumption can be reduced by improving the cooling capacity of the evaporator 4.

  Further, by providing an internal heat exchanger 7 for exchanging heat between the refrigerant that has exited the radiator 2 and the refrigerant that has exited the header 5, the header 5 is removed from the refrigerant that has exited the radiator 2 by the internal heat exchanger 7. It can be cooled by exchanging heat with the refrigerant. Thereby, the cooling capacity can be further improved. In particular, the header 5 is connected to the outlet side of the evaporator 4, and the refrigerant flowing out of the header 5 is caused to flow into the internal heat exchanger 7, so that the refrigerant that has passed through the header flowing into the internal heat exchanger 7 is usually gaseous. Therefore, the heat exchange in the internal heat exchanger 7 is stabilized, so that the state of the refrigerant flowing in the refrigerant circuit can be stabilized.

  Further, by providing the internal heat exchanger 7 on the refrigerant downstream side of the temperature sensor 23 as in this embodiment, even if liquid refrigerant is mixed in the refrigerant from the header 5, the internal heat exchange is performed. Since it can be evaporated in the vessel 7, the disadvantage that the liquid refrigerant is sucked into the compressor 1 and the compressor 1 performs liquid compression can be surely eliminated.

  Furthermore, even when carbon dioxide refrigerant is used as the refrigerant of the refrigeration cycle apparatus as in this embodiment, sufficient cooling capacity can be obtained by the present invention. Therefore, the refrigeration cycle apparatus using the carbon dioxide as a refrigerant as in this embodiment can be used for cooling purposes such as a refrigerator, and the versatility of the refrigeration cycle apparatus can be enhanced.

  In the present embodiment, the description has been given using the two-stage compression compressor 1 including the first compression element 1A and the second compression element 1B as the compressor. However, the compressor is a two-stage compressor as in the embodiment. The compressor is not limited to a compressor having a compression element, and a compressor having three, four, or more compression element elements may be applied. Further, a single-stage compressor 1 may be used as shown in FIG.

  Furthermore, in the refrigeration cycle apparatus of each of the above embodiments, carbon dioxide is used as the refrigerant. However, in the inventions of claims 1 to 3, the refrigerant is not limited to carbon dioxide. Therefore, the inventions described above are effective even when other refrigerants are used in addition to carbon dioxide as the refrigerant in the refrigeration cycle apparatus.

It is a refrigerant circuit figure of the refrigerating cycle device of one example of the present invention. (Example 1) FIG. 2 is an enlarged longitudinal sectional view of a header shown in FIG. It is a flowchart which shows control of the refrigerating-cycle apparatus of FIG. FIG. 2 is a ph diagram (Mollier diagram) of the refrigeration cycle apparatus of FIG. 1. It is a refrigerant circuit diagram which shows an example at the time of using another compressor (compressor of a single stage compression type) as a compressor of the refrigeration cycle apparatus of FIG. It is a refrigerant circuit figure of the refrigerating cycle device of other examples of the present invention. (Example 2) It is a refrigerant circuit figure which shows an example at the time of using another compressor (compressor of a single stage compression type) as a compressor of the refrigeration cycle apparatus of FIG. It is a refrigerant circuit diagram of the conventional refrigeration cycle apparatus.

Explanation of symbols

S Refrigeration cycle equipment 1 Multistage compression compressor (compressor)
DESCRIPTION OF SYMBOLS 1A 1st compression element 1B 2nd compression element 2 Radiator 3 Expansion valve 4 Evaporator 5 Header 7 Internal heat exchanger 8 Intermediate cooler 9 Check valve 10, 11 Refrigerant introduction pipe 12 Refrigerant discharge pipe 13, 14, 15 Refrigerant piping 20 Temperature sensor (first temperature sensor)
22, 23 Temperature sensor (second temperature sensor)
30 Control device (control means)

Claims (4)

In a refrigeration cycle apparatus having a refrigerant circuit in which a compressor, a radiator, an expansion valve, and an evaporator are sequentially connected by piping,
A header connected to the outlet side of the evaporator; a first temperature sensor that detects a refrigerant temperature at the evaporator inlet; and a second temperature that detects a refrigerant temperature at the header or a refrigerant temperature at the header outlet. A refrigeration cycle apparatus comprising: a temperature sensor; and control means for controlling a valve opening degree of the expansion valve based on outputs of both temperature sensors.   The control means determines the degree of superheat of the refrigerant in the evaporator based on the outputs of the temperature sensors, and expands the valve opening of the expansion valve when the degree of superheat is large, and the degree of superheat is small The refrigeration cycle apparatus according to claim 1, wherein the opening degree of the expansion valve is reduced.   The refrigeration cycle apparatus according to claim 1 or 2, further comprising an internal heat exchanger for exchanging heat between the refrigerant exiting the radiator and the refrigerant exiting the header.   The refrigeration cycle apparatus according to any one of claims 1 to 3, wherein carbon dioxide is used as the refrigerant.

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