JP6048549B1 - Refrigeration equipment - Google Patents

Abstract

[PROBLEMS] To improve a coefficient of performance (COP) of a refrigeration apparatus by promoting a decrease in operating frequency of a compressor during a low load period in a refrigerator during a cooling operation. A compressor control unit (83) operates an operating frequency (FQ) of a compressor (21a) so that a temperature of a refrigerant sucked into the compressor (21a) in a cooling operation becomes a target evaporation temperature (Te). ) To control. The target temperature setting unit (84) sets the target evaporating temperature (Te) from the start of the cooling operation until the pull-down period (PD) for decreasing the internal temperature (Tr) elapses. Set the reference temperature (Teref) lower than (Tset), and after the elapse of the pull-down period (PD), the operating frequency (FQ) of the compressor (21a) during the period when the user unit (12) is in the cooling state When the frequency index value (FQi) that depends on the value exceeds a predetermined reference value (FQref), the target evaporation temperature (Te) is corrected so that the target evaporation temperature (Te) becomes higher than the reference temperature (Teref). . [Selection] Figure 1

Description

  The present invention relates to a refrigeration apparatus.

  Conventionally, a refrigeration apparatus that performs a refrigeration cycle by circulating a refrigerant is known. Such a refrigeration apparatus is widely used for cooling a refrigerator or a freezer. For example, Patent Literature 1 discloses a refrigeration apparatus including an outdoor unit having a compressor and an outdoor heat exchanger, and a cooling unit (use side unit) having a use side heat exchanger.

  In the refrigeration apparatus of Patent Literature 1, an outdoor unit and a cooling unit are connected to form a refrigerant circuit. Moreover, in the cooling operation of this cooling device, the cooling unit cools the air in the thermo-on state (the use-side heat exchanger cools the air in the cabinet) according to the temperature of the cabinet air (inner chamber temperature) detected by the cabinet temperature sensor. State) or a thermo-off state (a state in which the air in the warehouse is not cooled by the use side heat exchanger). In this cooling device, the compressor is stopped when the cooling unit is in the thermo-off state, and the compressor is activated when the cooling unit is in the thermo-on state.

JP 2014-70830 A

  In the refrigeration apparatus of Patent Document 1, it is considered that the operating frequency of the compressor is controlled so that the temperature of the refrigerant sucked into the compressor (hereinafter referred to as “suction temperature”) becomes a predetermined target evaporation temperature. It is done. Note that in this case, the target evaporation temperature takes into account pressure loss (specifically, pipe length, pipe diameter, height difference, etc.) in the pipe between the liquid end of the use side heat exchanger and the suction port of the compressor. Thus, the temperature is set to be lower than the set temperature in the cabinet.

  Further, when the cooling operation is started, the use side unit is in a cooling state (a state in which the use side heat exchanger functions as an evaporator to cool the inside of the box), and the inside temperature gradually decreases. When a predetermined period (period for lowering the internal temperature) elapses from the start of the cooling operation, the internal temperature becomes a temperature in the vicinity of the internal set temperature, and the internal cooling load decreases. That is, the period after a predetermined period has elapsed since the start of the cooling operation is a period during which the internal temperature is stable near the internal set temperature and the internal cooling load is relatively low (hereinafter, It can be considered that it is described as “Low load period in the warehouse”.

  During the cooling operation, the cooling capacity required for the usage-side unit is relatively low. Therefore, the operating frequency of the compressor is lowered to reduce the coefficient of performance (COP) of the refrigeration system. It is preferable to improve. However, the lower the target evaporation temperature, the lower the operating frequency of the compressor during the low-load period during the cooling operation, and the more difficult it is to improve the coefficient of performance of the refrigeration apparatus.

  Therefore, an object of the present invention is to provide a refrigeration apparatus capable of improving the coefficient of performance by promoting the decrease in the operating frequency of the compressor during the low load period in the refrigerator during the cooling operation.

  1st invention has the heat source side unit (11) which has a compressor (21a) and a heat source side heat exchanger (23), and the utilization side which has a utilization side heat exchanger (51) and is provided in a store | warehouse | chamber A refrigerant circuit (15) in which the heat source side unit (11) and the usage side unit (12) are connected to circulate the refrigerant, and the usage side unit (12) In the cooling operation in which the heat source side heat exchanger (23) functions as a condenser, when the internal temperature (Tr) exceeds the internal set temperature range including the internal set temperature (Tset), the use side heat exchanger When the refrigerant is passed through (51) and the use side heat exchanger (51) functions as an evaporator, the inside temperature (Tr) falls below the set temperature range in the inside. It is configured to be in a dormant state in which the refrigerant flow in the heat exchanger (51) is shut off and cooling in the cabinet is suspended. And controlling the operating frequency (FQ) of the compressor (21a) so that the temperature of the refrigerant sucked into the compressor (21a) in the cooling operation becomes the target evaporation temperature (Te). The target evaporating temperature (Te) between the compressor control unit (83) and the pull-down period (PD) for decreasing the internal temperature (Tr) from the start of the cooling operation. The compressor is set to a reference temperature (Teref) lower than the set temperature (Tset) in the refrigerator, and after the pull-down period (PD) has elapsed, the compressor in the cooling continuation period in which the use side unit (12) is in the cooling state When the frequency index value (FQi) depending on the operating frequency (FQ) of (21a) exceeds a predetermined reference value (FQref), the target evaporation temperature (Te) is higher than the reference temperature (Teref). Target temperature setting to correct the target evaporation temperature (Te) so that (84) and a refrigeration apparatus which is characterized in that it comprises.

  In the first invention, by setting the target evaporation temperature (Te) to the reference temperature (Teref) from the start of the cooling operation until the pull-down period (PD) elapses, the user side in the pull-down period (PD) The cooling capacity of the unit (12) can be secured. Thereby, cooling in a store | warehouse | chamber can be performed appropriately in a pull-down period (PD).

  In the first invention, when the pull-down period (PD) elapses from the start of the cooling operation, the internal temperature (Tr) becomes a temperature in the vicinity of the internal set temperature (Tset), and the internal cooling load decreases. . That is, during the period after the pull-down period (PD) has elapsed since the start of the cooling operation, the internal temperature (Tr) is stable near the internal set temperature (Tset) and the internal cooling load is relatively low. It can be considered that the period is low (hereinafter referred to as “low load period in the warehouse”).

  In the first aspect of the invention, after the elapse of the pull-down period (PD), the frequency index value (FQi) in the cooling continuation period (period in which the use side unit (12) is in the cooling state) is the reference value (FQref). By adjusting the target evaporation temperature (Te) so that the target evaporation temperature (Te) is higher than the reference temperature (Teref) when the temperature exceeds When the compressor (21a) is driven at a relatively high operating frequency, the target evaporation temperature (Te) can be increased to promote a reduction in the operating frequency (FQ) of the compressor (21a) .

  According to a second aspect, in the first aspect, the frequency index value (FQi) corresponds to an average value (FQave) of the operating frequency (FQ) of the compressor (21a) during the cooling continuation period. It is the freezing apparatus characterized.

  In the second aspect of the invention, the target temperature setting unit (84) determines in advance the average value (FQave) of the operating frequency (FQ) of the compressor (21a) during the cooling continuation period after the elapse of the pull-down period (PD). If the reference value (FQref) is exceeded, the target evaporation temperature (Te) is corrected so that the target evaporation temperature (Te) is higher than the reference temperature (Teref). As a result, when the compressor (21a) is driven at a relatively high operating frequency during the low load period in the warehouse after the pull-down period (PD) has elapsed, the target evaporation temperature (Te) is increased and compression is performed. Reduction of the operating frequency (FQ) of the machine (21a) can be promoted.

  In a third aspect based on the first aspect, the frequency index value (FQi) is an operating frequency (FQi) of the compressor (21a) at a point in time when the usage-side unit (12) is brought into a rest state from a cooling state. ) Is a refrigeration apparatus characterized by that.

  In the third aspect of the invention, the target temperature setting unit (84) operates the operating frequency of the compressor (21a) at the time when the use side unit (12) goes from the cooling state to the resting state after the pull-down period (PD) has elapsed. When the FQ) exceeds a predetermined reference value (FQref), the target evaporation temperature (Te) is corrected so that the target evaporation temperature (Te) is higher than the reference temperature (Teref). As a result, when the compressor (21a) is driven at a relatively high operating frequency during the low load period in the warehouse after the pull-down period (PD) has elapsed, the target evaporation temperature (Te) is increased and compression is performed. Reduction of the operating frequency (FQ) of the machine (21a) can be promoted.

  In a fourth aspect based on any one of the first to third aspects, the target temperature setting section (84) is configured such that the target evaporation temperature (Te) exceeds a predetermined upper limit temperature (Temax). The refrigeration apparatus is characterized in that the target evaporation temperature (Te) is corrected so as not to occur.

  In the fourth invention, the target evaporation temperature (Te) is prevented from becoming too high by correcting the target evaporation temperature (Te) so that the target evaporation temperature (Te) does not exceed the upper limit temperature (Temax). be able to.

  In a fifth aspect based on any one of the first to fourth aspects, the target temperature setting unit (84) has the target evaporation temperature (Te) higher than the reference temperature (Teref). When the length of the cooling duration exceeds a predetermined duration threshold (Tth), the target evaporation temperature (Te) decreases and approaches the reference temperature (Teref) or the reference temperature The refrigeration apparatus is characterized in that the target evaporation temperature (Te) is corrected so as to coincide with (Teref).

  In addition, in the low load period in the warehouse after the elapse of the pull-down period (PD), heat outside the warehouse may enter the warehouse due to opening and closing of the door, and the cooling load in the warehouse may increase. Thus, when the cooling load in a store | warehouse | chamber becomes high, a cooling continuation period (period when the use side unit (12) is a cooling state) will become long.

  In the fifth aspect of the invention, the target evaporation temperature (Te) is lowered when the length of the cooling continuation period (period in which the use side unit (12) is in the cooling state) exceeds the duration threshold value (Tth). As a result, the cooling capacity of the usage-side unit (12) can be increased when the internal cooling load increases during the internal low load period after the pull-down period (PD) elapses.

  According to a sixth invention, in any one of the first to fifth inventions, the target temperature setting unit (84) is configured to connect the use-side heat exchanger (51) after the end of the cooling operation. The target evaporation temperature (Te) is set to the reference temperature (Teref) before the start of a defrosting operation that functions as a condenser and the heat source side heat exchanger (23) functions as an evaporator. Refrigeration equipment.

  In the said 6th invention, the heat dissipation capability (specifically, the heat dissipation capability of the utilization side heat exchanger (51)) can be ensured in the defrosting operation.

  In a seventh aspect based on any one of the first to sixth aspects, the pull-down period (PD) is determined so that the use side unit (12) changes from a cooling state to a dormant state from the start of the cooling operation. The refrigeration apparatus corresponds to a shorter period of a period until a certain time and a period from when the cooling operation starts until a predetermined time (T1) elapses.

  In said 7th invention, when a utilization side unit (12) changes from a cooling state to a dormant state after the start of cooling operation, the internal temperature (Tr) becomes a temperature in the vicinity of the internal set temperature (Tset). Can be considered. In addition, even if a sufficient time (that is, the predetermined time (T1)) has elapsed after the start of the cooling operation, it is considered that the internal temperature (Tr) is close to the internal set temperature (Tset). Can do.

  According to the first to third inventions, when the compressor (21a) is driven at a relatively high operating frequency in the low load period in the warehouse after the lapse of the pull-down period (PD), the target evaporation temperature ( Te) can be increased to promote a decrease in the operating frequency (FQ) of the compressor (21a), so that the coefficient of performance (COP) of the refrigeration apparatus can be improved during the low load period in the refrigerator during the cooling operation. it can.

  According to the fourth aspect of the invention, since the target evaporation temperature (Te) can be prevented from becoming too high, the cooling capacity of the user side unit (12) due to the increase in the target evaporation temperature (Te) is reduced. Can be prevented.

  According to the fifth aspect of the present invention, the cooling capacity of the use side unit (12) can be increased when the cooling load in the warehouse becomes high during the low load period in the warehouse after the lapse of the pull-down period (PD). The internal temperature (Tr) can be quickly brought close to the internal set temperature (Tset).

  According to the sixth aspect of the invention, since the heat radiation capability of the use side unit (12) can be ensured in the defrosting operation, the use side heat exchanger (51) can be appropriately defrosted in the defrosting operation. it can.

  According to the seventh aspect, the period from the start of the cooling operation to the time when the user-side unit (12) enters the resting state from the cooling state, and the time when the predetermined time (T1) has elapsed from the start of the cooling operation By setting the shorter period of the previous period as the pull-down period (PD), the internal temperature (Tr) is lowered in the pull-down period (DP) and the internal temperature (Tr) is set to the internal set temperature (Tset) The temperature can be in the vicinity of.

FIG. 1 is a piping diagram illustrating a configuration example of a refrigeration apparatus according to an embodiment. FIG. 2 is a flowchart showing the operation of the refrigeration apparatus. FIG. 3 is a piping diagram showing the refrigerant flow in the cooling operation. FIG. 4 is a piping diagram showing the refrigerant flow in the defrosting operation. FIG. 5 is a flowchart for explaining the operation of the target temperature setting unit in the cooling operation. FIG. 6 is a graph for explaining the frequency index value. FIG. 7 is a graph for explaining a change in the internal temperature. FIG. 8 is a graph for explaining a change in the operating frequency of the compressor in the comparative example of the refrigeration apparatus. FIG. 9 is a graph for explaining a change in the operating frequency of the compressor in the refrigeration apparatus according to the embodiment.

  Hereinafter, embodiments will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

(Refrigeration equipment)
FIG. 1 shows a configuration example of a refrigeration apparatus (10) according to an embodiment. The refrigeration apparatus (10) includes a heat source side unit (11) provided outside the storage, a use side unit (12) provided in a storage such as a refrigerator or a freezer, and a controller (80). The heat source side unit (11) includes a heat source side circuit (16) and a heat source side fan (17), and the usage side unit (12) includes a usage side circuit (18), a usage side fan (19), and Is provided. In this refrigeration system (10), the heat source side circuit (16) of the heat source side unit (11) and the usage side circuit (18) of the usage side unit (12) are connected to the liquid side communication pipe (13) and the gas side communication pipe ( 14), a refrigerant circuit (15) in which a refrigerant circulates and a vapor compression refrigeration cycle is performed is configured. Specifically, a liquid closing valve (V1) and a gas closing valve (V2) are provided at the liquid end and the gas end of the heat source side circuit (16), respectively, and the liquid closing valve (V1) and the gas closing valve (V2) One end of the liquid side connecting pipe (13) and one end of the gas side connecting pipe (14) are connected to the liquid side connecting pipe (13) and the gas side connecting pipe (14), respectively. Each gas end is connected.

<Heat source side circuit>
The heat source side circuit (16) includes first and second compressors (21a, 21b), a four-way switching valve (22), a heat source side heat exchanger (23), a supercooling heat exchanger (24), A supercooling expansion valve (31), an intermediate expansion valve (32), an intermediate on-off valve (33), an intermediate check valve (34), a receiver (35), a heat source side expansion valve (36), 1, second and third check valves (CV1, CV2, CV3), first and second oil separators (OSa, OSb), first and second discharge check valves (CVa, CVb), It has first and second capillary tubes (CTa, CTb) and an oil separation check valve (CVc).

  The heat source side circuit (16) includes a discharge refrigerant pipe (41), an intake refrigerant pipe (42), a heat source side liquid refrigerant pipe (43), an injection pipe (44), and first and second connections. Pipes (45, 46) and an oil return pipe (47) are provided.

《Compressor》
The first compressor (21a) is configured to compress and discharge the sucked refrigerant. The first compressor (21a) is provided with a suction port, an intermediate port, and a discharge port. The suction port is formed so as to communicate with the compression chamber (that is, the low-pressure compression chamber) in the suction stroke of the first compressor (21a). The intermediate port is formed so as to communicate with the compression chamber (that is, the compression chamber of intermediate pressure) during the compression stroke of the first compressor (21a). The discharge port is configured to communicate with the compression chamber (that is, the high-pressure compression chamber) in the discharge stroke of the first compressor (21a). For example, the first compressor (21a) is configured by a scroll compressor in which a compression chamber is formed between a fixed scroll and a movable scroll that mesh with each other. The second compressor (21b) has a configuration similar to that of the first compressor (21a).

  The first compressor (21a) has a variable operating frequency (capacity). In other words, the first compressor (21a) is configured such that by changing the output frequency of the inverter (not shown), the rotational speed of the motor provided therein changes, and the operating frequency changes. ing. On the other hand, the operating frequency (capacity) of the second compressor (21b) is fixed. That is, as for the 2nd compressor (21b), the rotation speed of the electric motor provided in the inside is constant, and the operating frequency is constant.

<4-way switching valve>
The four-way switching valve (22) includes a first state (state indicated by a solid line in FIG. 1) in which the first port and the third port communicate with each other and the second port and the fourth port communicate with each other, And the fourth port are in communication with each other and the second port and the third port are in communication with each other (a state indicated by a broken line in FIG. 1).

  The first port of the four-way switching valve (22) is connected to the discharge ports of the first and second compressors (21a, 21b) by the discharge refrigerant pipe (41), and the second port of the four-way switching valve (22) is The suction refrigerant pipe (42) is connected to the suction ports of the first and second compressors (21a, 21b). The third port of the four-way switching valve (22) is connected to the gas end of the heat source side heat exchanger (23), and the fourth port of the four-way switching valve (22) is connected to the gas closing valve (V2). .

<Discharge refrigerant piping>
The discharge refrigerant pipe (41) has first and second discharge pipes (41a, 41b) whose one ends are connected to discharge ports of the first and second compressors (21a, 21b), and first and second discharge pipes. It is comprised by the discharge main pipe (41c) which connects the other end of (41a, 41b) and the 1st port of the four-way selector valve (22).

<Suction refrigerant piping>
The suction refrigerant pipe (42) has first and second suction pipes (42a, 42b) connected at one end to the suction ports of the first and second compressors (21a, 21b), respectively, and the first and second suction pipes. The suction main pipe (42c) connects the other end of the pipe (42a, 42b) and the second port of the four-way selector valve (22).

《Heat source side heat exchanger》
The liquid end of the heat source side heat exchanger (23) is connected to one end of the heat source side liquid refrigerant pipe (43), and the gas end is connected to the third port of the four-way switching valve (22). Moreover, the heat source side fan (17) is arrange | positioned in the vicinity of the heat source side heat exchanger (23). The heat source side heat exchanger (23) is configured to exchange heat between the refrigerant and the heat source side air (that is, outside air) conveyed by the heat source side fan (17). For example, the heat source side heat exchanger (23) is configured by a cross-fin type fin-and-tube heat exchanger.

<Heat source side liquid refrigerant piping>
One end of the heat source side liquid refrigerant pipe (43) is connected to the heat source side heat exchanger (23), and the other end is connected to the liquid closing valve (V1). In this example, the heat source side liquid refrigerant pipe (43) includes a first heat source side liquid pipe (43a) that connects the liquid end of the heat source side heat exchanger (23) and the receiver (35), and a receiver (35). A second heat source side liquid pipe (43b) connecting the supercooling heat exchanger (24), and a third heat source side liquid pipe (43c) connecting the supercooling heat exchanger (24) and the liquid shut-off valve (V1). ) And.

《Injection piping》
The injection pipe (44) connects the first intermediate part (Q1) of the heat source side liquid refrigerant pipe (43) and the intermediate ports of the first and second compressors (21a, 21b). In this example, the injection pipe (44) includes a first injection main pipe (44m) that connects the first intermediate part (Q1) of the heat source side liquid refrigerant pipe (43) and the supercooling heat exchanger (24), and one end. The second injection main pipe (44n) connected to the supercooling heat exchanger (24), the other end of the second injection main pipe (44n), and the intermediate ports of the first and second compressors (21a, 21b). The first and second injection branch pipes (44a, 44b) are connected to each other.

《Supercooling heat exchanger》
The supercooling heat exchanger (24) is connected to the heat source side liquid refrigerant pipe (43) and the injection pipe (44), and includes a refrigerant flowing through the heat source side liquid refrigerant pipe (43) and a refrigerant flowing through the injection pipe (44). Are configured to exchange heat. In this example, the supercooling heat exchanger (24) includes a first flow path (24a) connected between the second heat source side liquid pipe (43b) and the third heat source side liquid pipe (43c), The second flow path (24b) connected between the 1 injection main pipe (44m) and the second injection main pipe (44n), and the refrigerant flowing through the first flow path (24a) and the second flow path (24b ) To exchange heat. For example, the supercooling heat exchanger (24) is configured by a plate heat exchanger.

《Supercooling expansion valve》
The supercooling expansion valve (31) is located between the first intermediate part (Q1) of the heat source side liquid refrigerant pipe (43) and the supercooling heat exchanger (24) in the injection pipe (44) (in this example, the first It is provided in the injection main pipe (44m). Further, the supercooling expansion valve (31) is configured such that its opening degree can be adjusted. For example, the supercooling expansion valve (31) is constituted by an electronic expansion valve (motorized valve).

《Intermediate expansion valve》
The intermediate expansion valve (32) is located between the supercooling heat exchanger (24) and the intermediate port of the first compressor (21a) in the injection pipe (54) (in this example, the first injection branch pipe (44a)). Is provided. Further, the intermediate expansion valve (32) is configured so that its opening degree can be adjusted. For example, the intermediate expansion valve (32) is configured by an electronic expansion valve (motorized valve).

《Intermediate open / close valve and intermediate check valve》
The intermediate on-off valve (33) and the intermediate check valve (34) are provided between the supercooling heat exchanger (24) and the intermediate port of the second compressor (22a) in the injection pipe (54) (in this example, the first 2 injection branch pipe (44b)). In the second injection branch pipe (44b), an intermediate on-off valve (33) and an intermediate check valve (34) are sequentially arranged from the inlet side to the outlet side of the second injection branch pipe (44b).

  The intermediate on-off valve (33) is configured to be able to switch between opening and closing thereof. For example, the intermediate opening / closing valve (33) is constituted by a solenoid valve. The intermediate check valve (34) is configured to allow the refrigerant flow from the inlet side to the outlet side of the second injection branch pipe (44b) and to block the refrigerant flow in the reverse direction.

<Receiver>
The receiver (35) is connected between the heat source side heat exchanger (23) and the supercooling heat exchanger (24) in the heat source side liquid refrigerant pipe (43), and is connected to a condenser (specifically, heat source side heat The refrigerant condensed in the exchanger (23) or a later-described use side heat exchanger (51)) can be temporarily stored. In this example, the receiver (35) has a first heat source side liquid pipe (53a) connected to the inlet and a second heat source side liquid pipe (53b) connected to the outlet.

<< First connection piping >>
The first connection pipe (45) connects the second midway part (Q2) and the third midway part (Q3) of the heat source side liquid refrigerant pipe (43). The second halfway part (Q2) is located between the first halfway part (Q1) and the liquid shut-off valve (V1) in the heat source side liquid refrigerant pipe (43), and the third halfway part (Q3) is located on the heat source side It is located between the liquid end of the heat source side heat exchanger (23) and the receiver (35) in the liquid refrigerant pipe (43).

《Second connection piping》
The second connection pipe (46) connects the fourth midway part (Q4) and the fifth midway part (Q5) of the heat source side liquid refrigerant pipe (43). The fourth midway part (Q4) is located between the first halfway part (Q1) and the second halfway part (Q2) in the heat source side liquid refrigerant pipe (43), and the fifth halfway part (Q5) is located on the heat source side The liquid refrigerant pipe (43) is located between the liquid end of the heat source side heat exchanger (23) and the third midway part (Q3).

<Heat source side expansion valve>
The heat source side expansion valve (36) is provided in the second connection pipe (46). Moreover, the heat source side expansion valve (36) is comprised so that the opening degree can be adjusted. For example, the heat source side expansion valve (36) is configured by an electronic expansion valve (motorized valve).

《First check valve》
The first check valve (CV1) is provided between the third midway part (Q3) and the fifth midway part (Q5) of the heat source side liquid refrigerant pipe (43), and the first check valve (CV1) 3. The refrigerant flow toward the middle part (Q3) is allowed and the refrigerant flow in the opposite direction is blocked.

《Second check valve》
The second check valve (CV2) is provided between the second midway part (Q2) and the fourth midway part (Q4) of the heat source side liquid refrigerant pipe (43), and the second midway part (Q4) to the second midway part (Q4). 2 The refrigerant flow toward the middle part (Q2) is allowed and the refrigerant flow in the opposite direction is blocked.

《Third check valve》
The third check valve (CV3) is provided in the first connection pipe (45), and the refrigerant flows from the second midway part (Q2) to the third midway part (Q3) of the heat source side liquid refrigerant pipe (43). And the refrigerant flow in the opposite direction is blocked.

<< First oil separator and first discharge check valve >>
The first oil separator (OSa) and the first discharge check valve (CVa) are disposed between the first compressor (21a) and the first port of the four-way switching valve (22) in the discharge refrigerant pipe (41) (specifically Specifically, it is provided in the first discharge pipe (41a). In the first discharge pipe (41a), a first oil separator (OSa) and a first discharge check valve (CVa) are sequentially arranged from the inlet side to the outlet side of the first discharge pipe (41a). . The first oil separator (OSa) is configured to separate the refrigerating machine oil from the refrigerant discharged from the first compressor (21a) and store it inside. The first discharge check valve (CVa) is configured to allow the flow of the refrigerant from the inlet side to the outlet side of the first discharge pipe (41a) and prevent the refrigerant flow in the reverse direction.

《Second oil separator and second discharge check valve》
The second oil separator (OSb) is disposed between the second compressor (21b) and the first port of the four-way switching valve (22) in the discharge refrigerant pipe (41) (specifically, the second discharge pipe (41b )). In the second discharge pipe (41b), a second oil separator (OSb) and a second discharge check valve (CVb) are sequentially arranged from the inlet side to the outlet side of the second discharge pipe (41b). . The second oil separator (OSb) is configured so that the refrigeration oil can be separated from the refrigerant discharged from the second compressor (21b) and stored inside. The second discharge check valve (CVb) is configured to allow the refrigerant flow from the inlet side to the outlet side of the second discharge pipe (41b) and to block the refrigerant flow in the reverse direction.

<Oil return piping>
The oil return pipe (47) is a pipe for supplying the refrigeration oil stored in the first and second oil separators (OSa, OSb) to the injection pipe (44). In this example, the oil return pipe (47) includes first and second oil return pipes (47a, 47b) whose one ends are connected to the first and second oil separators (OSa, OSb), and the first and second oil return pipes (47). 2. Oil return main pipe (47c) connecting the other end of the oil return pipe (47a, 47b) and the middle part of the injection pipe (44) (specifically, the middle part (Q6) of the second injection main pipe (44n)) ) And.

<< First capillary tube >>
The first capillary tube (CTa) is located between the first oil separator (OSa) and the middle part (Q6) of the injection pipe (44) in the oil return pipe (47) (specifically, the first oil return pipe). (47a)).

《Second capillary tube and oil return check valve》
The second capillary tube (CTb) and oil return check valve (CVc) are located between the second oil separator (OSb) and the middle part (Q6) of the injection pipe (44) in the oil return pipe (47). Specifically, the second oil return pipe (47b) is provided. In the second oil return pipe (47b), an oil return check valve (CVc) and a second capillary tube (CTb) are sequentially arranged from the inlet side to the outlet side of the second oil return pipe (47b). . The oil return check valve (CVc) is configured to allow the refrigerant flow from the inlet side to the outlet side of the second oil return pipe (47b) and to block the refrigerant flow in the reverse direction.

<User side circuit>
The utilization side circuit (18) includes a utilization side heat exchanger (51), a utilization side on-off valve (52), a utilization side expansion valve (53), and a utilization side check valve (54). . Further, the use side circuit (18) is provided with a use side liquid refrigerant pipe (61), a use side gas refrigerant pipe (62), and a bypass pipe (63).

《Use side heat exchanger》
The liquid end of the use side heat exchanger (51) is connected to the liquid side connection pipe (13) by the use side liquid refrigerant pipe (61), and the gas end is connected to the gas side by the use side gas refrigerant pipe (62). Connected to pipe (14). Moreover, the utilization side fan (19) is arrange | positioned in the vicinity of the utilization side heat exchanger (51). The use side heat exchanger (51) is configured to exchange heat between the refrigerant and the use side air (that is, the internal air) conveyed by the use side fan (19). For example, the use side heat exchanger (51) is configured by a cross-fin type fin-and-tube heat exchanger.

《Use side liquid refrigerant piping and usage side gas refrigerant piping》
One end of the use side liquid refrigerant pipe (61) is connected to the liquid side connecting pipe (13), and the other end is connected to the liquid end of the use side heat exchanger (51). The use side gas refrigerant pipe (62) has one end connected to the gas end of the use side heat exchanger (51) and the other end connected to the gas side communication pipe (14).

《Use side open / close valve and use side expansion valve》
The use side on-off valve (52) and the use side expansion valve (53) are provided in the use side liquid refrigerant pipe (61). In the use side liquid refrigerant pipe (61), a use side on-off valve (52) and a use side expansion valve (53) are arranged in this order from one end side to the other end side of the use side liquid refrigerant pipe (61). .

  The use side on-off valve (52) is configured to be able to switch its opening and closing. For example, the use side on-off valve (52) is constituted by a solenoid valve. The use side expansion valve (53) is configured such that its opening degree can be adjusted. In this example, the use side expansion valve (53) is constituted by an external pressure equalization type temperature automatic expansion valve. That is, the use side expansion valve (53) includes a temperature sensing tube (63a) provided in the use side gas refrigerant pipe (62) and a pressure equalizing pipe (not shown) connected to the middle part of the use side gas refrigerant pipe (72). The opening degree is adjusted in accordance with the temperature of the temperature sensing cylinder (63a) and the refrigerant pressure of the pressure equalizing pipe.

<Bypass piping>
One end of the bypass pipe (63) is connected to a midway part between the use side expansion valve (53) and the use side heat exchanger (51) in the use side liquid refrigerant pipe (61), and the other end is used. The liquid refrigerant pipe (61) is connected to a midway part between the liquid side connecting pipe (13) and the use side on-off valve (52).

《Use side check valve》
The use-side check valve (54) is provided in the bypass pipe (63) and allows the refrigerant to flow from the use-side heat exchanger (51) side to the liquid-side connecting pipe (13) side, and in the opposite direction. It is configured to block the flow of the refrigerant.

<Various sensors>
The refrigeration apparatus (10) is provided with various sensors such as an intake temperature sensor (71), an intake pressure sensor (72), and an internal temperature sensor (73).

《Suction temperature sensor》
The suction temperature sensor (71) is configured to detect the temperature of the refrigerant sucked into the first and second compressors (21a, 21b) (hereinafter referred to as “suction temperature”). In this example, the suction temperature sensor (71) is installed in the suction main pipe (42c) and detects the refrigerant temperature at the installation location as the suction temperature.

<Suction pressure sensor>
The suction pressure sensor (72) is configured to detect the pressure of the refrigerant sucked into the first and second compressors (21a, 21b) (hereinafter referred to as “suction pressure”). In this example, the suction pressure sensor (72) is installed in the suction main pipe (42c) and detects the refrigerant pressure at the installation location as the suction pressure.

<Inside temperature sensor>
The internal temperature sensor (73) is configured to detect the temperature of the air in the internal space (hereinafter referred to as “internal temperature (Tr)”). In this example, the internal temperature sensor (73) is installed downstream of the air flow of the usage-side fan (19) in the usage-side unit (12), and detects the air temperature at the installation location as the internal temperature (Tr). To do.

<controller>
The controller (80) controls the operation of the refrigeration apparatus (10) by controlling each part of the refrigeration apparatus (10) based on the detection values of the various sensors. In this example, the controller (80) includes a main controller (81) provided in the heat source side unit (11) and a use side controller (86) provided in the use side unit (12).

<Main controller>
The main controller (81) controls the components provided in the heat source side unit (11). In this example, the main controller (81) includes an operation control unit (82), a compressor control unit (83), and a target temperature setting unit (84). The operation control unit (82) includes a heat source side fan (17) and various valves (in this example, a four-way switching valve (22), a supercooling expansion valve (31), and an intermediate expansion valve provided in the heat source side unit (11). (32) and intermediate on-off valve (33)) are controlled. The compressor control unit (83) controls the first and second compressors (21a, 21b). The target temperature setting unit (84) sets a target evaporation temperature (Te) described later.

《User side controller》
The use side controller (86) controls the components (in this example, the use side fan (19) and the use side on-off valve (52)) provided in the use side unit (12).

  Further, the use side controller (86) determines whether or not the operation of the refrigeration apparatus (10) should be started, and if it determines that the operation of the refrigeration apparatus (10) should be started, the cooling operation (cools the inside of the refrigerator). For starting the operation) and an operation start signal is transmitted to the main controller (81). Further, the use-side controller (86) determines whether or not the operation of the refrigeration apparatus (10) should be ended, and if it determines that the operation of the refrigeration apparatus (10) should be ended, the operation for the cooling operation is performed. At the same time, an operation end signal is transmitted to the main controller (81). For example, the usage-side controller (86) determines the operation start and operation end of the refrigeration apparatus (10) in response to an operation by the user (operation for instructing operation start and operation end).

  Further, the use side controller (86) determines whether or not to start the defrosting operation (operation for defrosting the use side heat exchanger (51)) during the period in which the cooling operation is performed, When it is determined that the defrosting operation should be started, an operation for the defrosting operation is started and a defrosting start signal is transmitted to the main controller (81). In addition, the use side controller (86) determines whether or not the defrosting operation should be terminated during the period during which the defrosting operation is performed, and determines that the defrosting operation should be terminated. And the operation for cooling operation is started, and a defrosting end signal is transmitted to the main controller (81). For example, the use side controller (86) determines that the defrosting operation should be started after a predetermined time (cooling operation time) has elapsed from the time when the cooling operation is started, and starts the defrosting operation. When a predetermined time (defrosting operation time) determined in advance has elapsed from the time, it is determined that the defrosting operation should be terminated.

<Operation of refrigeration equipment>
Next, the operation of the refrigeration apparatus (10) will be described with reference to FIG.

《Step (ST10)》
When the target temperature setting unit (84) receives the operation start signal from the use side controller (86), the target temperature setting unit (84) sets the target evaporation temperature (Te) to a predetermined reference temperature (Teref). The target evaporation temperature (Te) is a target temperature set with respect to the temperature of the refrigerant sucked into the first and second compressors (21a, 21b). The reference temperature (Teref) is set to a temperature lower than the internal set temperature (Tset). The internal set temperature (Tset) is a target temperature set for the internal temperature (Tr). The reference temperature (Teref) is the pressure loss (specifically, the pressure loss in the pipe between the liquid end of the use side heat exchanger (51) and the suction ports of the first and second compressors (21a, 21b). It is preferable to set in consideration of pipe length, pipe diameter, height difference, and the like. Specifically, the reference temperature (Teref) is obtained by subtracting a predetermined temperature (for example, a temperature included in a range from 10 ° C. to 17 ° C.) from the internal set temperature (Tset). Is set.

<Step (ST11): Cooling operation>
Next, the main controller (81) and the use side controller (86) control each part of the refrigeration apparatus (10) so that the cooling operation is performed in the refrigeration apparatus (10). In the cooling operation, in the refrigerant circuit (15), the heat source side heat exchanger (23) serves as a condenser, the supercooling heat exchanger (24) serves as a subcooler, and the use side heat exchanger (51) serves as an evaporator. Is performed to cool the interior. The refrigerant flow in the refrigerant circuit (15) during the cooling operation and the operation of the target temperature setting unit (84) during the cooling operation will be described in detail later.

  When the operation control unit (82) receives the operation start signal (or defrosting end signal) from the use side controller (86), the operation control unit (82) sets the four-way switching valve (22) to the first state, and the heat source side fan ( 17) is set to the drive state. Further, the operation control unit (82) is configured so that the degree of supercooling of the refrigerant in the supercooling heat exchanger (24) (specifically, the refrigerant at the outlet of the first flow path (24a) of the supercooling heat exchanger (24)). The degree of superheat of the refrigerant discharged from the first compressor (21a) is determined in advance by adjusting the opening degree of the supercooling expansion valve (31) so that the degree of supercooling of the refrigerant reaches a predetermined target supercooling degree. The opening degree of the intermediate expansion valve (32) is adjusted so as to achieve the target superheat degree. Further, the operation control unit (82) sets the intermediate on-off valve (33) to an open state and sets the heat source side expansion valve (36) to a fully closed state.

  Moreover, a compressor control part (83) will drive a 1st and 2nd compressor (21a, 21b), if the operation start signal (or defrost end signal) from a utilization side controller (86) is received. Set to. The compressor control unit (83) is configured to output the first and second compressors when the refrigerant pressure (that is, the suction pressure) detected by the suction pressure sensor (72) exceeds a predetermined low pressure range. (21a, 21b) is set to the driving state, and when the suction pressure falls below the low pressure range, the first and second compressors (21a, 21b) are set to the stopped state. The low pressure range will be described in detail later.

  In the compressor control unit (83), the refrigerant temperature (that is, the suction temperature) detected by the suction temperature sensor (71) becomes the target evaporation temperature (Te) set by the target temperature setting unit (84). In this way, the operating frequency (FQ) of the first compressor (21a) is controlled. Specifically, the compressor control unit (83) increases the operating frequency (FQ) of the first compressor (21a) when the suction temperature is higher than the target evaporation temperature (Te). As a result, the suction temperature can be lowered to bring the suction temperature closer to the target evaporation temperature (Te). On the other hand, the compressor control unit (83) reduces the operating frequency (FQ) of the first compressor (21a) when the suction temperature is lower than the target evaporation temperature (Te). Thereby, the suction temperature can be raised to bring the suction temperature closer to the target evaporation temperature (Te).

  Further, when the usage-side controller (86) determines that the operation of the refrigeration apparatus (10) should be started (or the defrosting operation should be ended), the usage-side fan (19) is set to the driving state. Further, the use side controller (86) is configured such that the temperature of the air detected by the internal temperature sensor (73) (that is, the internal temperature (Tr)) includes the internal set temperature (Tset). When the temperature exceeds the set temperature (Tset) (for example, a temperature range having a median value in the chamber), the use side on-off valve (52) is set in an open state to allow the refrigerant to flow through the use side heat exchanger (51). . Thereby, a use side heat exchanger (51) functions as an evaporator. On the other hand, the use side controller (86) sets the use side on-off valve (52) to the closed state when the inside temperature (Tr) falls below the set temperature range inside the compartment, and the use side heat exchanger (51) Block the flow of refrigerant.

  In this way, the use side unit (12) causes the use side heat exchanger (51) to circulate the refrigerant when the internal temperature (Tr) exceeds the internal set temperature range in the cooling operation. When the exchanger (51) is in a cooling state that functions as an evaporator and the internal temperature (Tr) is below the internal set temperature range, the refrigerant flow in the use side heat exchanger (51) is shut off and stored. It becomes a dormant state in which the inside cooling is suspended.

  Further, in the use side unit (12), the temperature of the temperature sensing tube (53a) and the pressure equalizing pipe (not shown) are set so that the superheat degree of the refrigerant at the outlet of the use side heat exchanger (51) becomes a predetermined superheat degree. The opening degree of the use side expansion valve (53) changes in accordance with the refrigerant pressure.

《Step (ST12)》
The use side controller (86) determines whether or not the defrosting operation should be started in the cooling operation period (period in which the cooling operation is performed). And if a use side controller (86) determines with defrosting operation should be started, it will transmit a defrost start signal to a main controller (86). Next, the process proceeds to step (ST13).

<Step (ST13)>
When the target temperature setting unit (84) receives the defrosting start signal from the use side controller (86), the target temperature setting unit (84) sets the target evaporation temperature (Te) to the reference temperature (Teref). That is, the target temperature setting unit (84) sets the target evaporation temperature (Te) to the reference temperature (Teref) after the cooling operation is completed and before the defrosting operation is started.

<Step (ST14): Defrosting operation>
Next, the main controller (81) and the use side controller (86) control each part of the refrigeration apparatus (10) so that the defrosting operation is performed in the refrigeration apparatus (10). In the defrosting operation, in the refrigerant circuit (20), a refrigeration cycle is performed in which the use side heat exchanger (51) serves as a condenser and the heat source side heat exchanger (23) serves as an evaporator, and the use side heat exchanger (51). Is defrosted. The refrigerant flow in the refrigerant circuit (15) during the defrosting operation will be described in detail later.

  When the operation control unit (82) receives the defrosting start signal from the use side controller (86), the four-way switching valve (22) is set to the second state and the heat source side fan (17) is set to the driving state. To do. The operation control unit (82) sets the supercooling expansion valve (31) and the intermediate expansion valve (32) to a fully closed state, sets the intermediate on-off valve (33) to a closed state, and heat source side heat exchanger The opening degree of the heat source side expansion valve (36) is adjusted so that the superheat degree of the refrigerant at the outlet of (23) becomes a predetermined target superheat degree.

  Moreover, a compressor control part (83) will set a 1st and 2nd compressor (21a, 21b) to a drive state, if the defrost start signal from a utilization side controller (86) is received. In the compressor control unit (83), similarly to the cooling operation, the temperature of the refrigerant detected by the intake temperature sensor (71) (that is, the intake temperature) is set by the target temperature setting unit (84). The operating frequency (FQ) of the first compressor (21a) is controlled so as to reach the target evaporation temperature (Te).

  Moreover, if the use side controller (86) determines that the defrosting operation should be started, it sets the use side fan (19) to a stopped state. Moreover, a utilization side controller (86) sets a utilization side on-off valve (52) to an open state, and distribute | circulates a refrigerant | coolant to a utilization side heat exchanger (51). Thereby, a use side heat exchanger (51) functions as a condenser. That is, the usage-side unit (12) enters a heat dissipation state in which the usage-side heat exchanger (51) functions as a condenser by allowing the refrigerant to flow through the usage-side heat exchanger (51). In the use side unit (12), the use side expansion valve (53) is opened.

《Step (ST15)》
Next, a utilization side controller (86) determines whether a defrost operation should be complete | finished in a defrost operation period (period in which the defrost operation is performed). And if a use side controller (86) determines with defrosting operation having to be ended, a defrost end signal will be transmitted to a main controller (81). Next, the process proceeds to step (ST11).

<Flow of refrigerant during cooling operation>
Next, the refrigerant flow in the refrigerant circuit (15) during the cooling operation will be described with reference to FIG. In the cooling operation, the four-way selector valve (22) is set to the first state, the discharge ports of the first and second compressors (21a, 21b) and the gas end of the heat source side heat exchanger (33) communicate with each other, The suction ports of the first and second compressors (21a, 21b) communicate with the gas side communication pipe (14).

  The refrigerant discharged from the first and second compressors (21a, 21b) is discharged from the first and second oil separators (OSa, OSb) and the first and second discharge check valves (41) in the discharge refrigerant pipe (41). CVa, CVb), and then passes through the four-way switching valve (22) and flows into the heat source side heat exchanger (23). In the heat source side heat exchanger (23), the heat source side air (that is, outside air) ) To dissipate heat and condense. The refrigerant (high-pressure refrigerant) flowing out from the heat source side heat exchanger (23) passes through the first check valve (CV1) in the first heat source side liquid pipe (43a), and then the receiver (35) and the second heat source side. A refrigerant (passing through the liquid pipe (43b) in order and flowing into the first flow path (34a) of the supercooling heat exchanger (24) and flowing through the second flow path (24b) of the supercooling heat exchanger (24) ( The refrigerant is absorbed by the intermediate pressure refrigerant) and supercooled. The refrigerant flowing out of the first flow path (24a) of the supercooling heat exchanger (24) flows into the third heat source side liquid pipe (43c), and part of it flows into the first injection main pipe (44m), The remaining portion passes through the second check valve (CV2) in the third heat source side liquid pipe (43c), then passes through the liquid closing valve (V1) and flows into the liquid side connecting pipe (13).

  The refrigerant flowing into the first injection main pipe (44m) is depressurized in the supercooling expansion valve (31), flows into the second flow path (24b) of the supercooling heat exchanger (24), and then enters the supercooling heat exchanger ( Heat is absorbed from the refrigerant (high-pressure refrigerant) flowing through the first flow path (24a) of 24). The refrigerant flowing out from the second flow path (24b) of the supercooling heat exchanger (24) passes through the second injection main pipe (44n), and part of it flows into the first injection branch pipe (44a). The remaining part flows into the second injection branch pipe (44b). The refrigerant flowing into the first injection branch pipe (44a) is decompressed by the intermediate expansion valve (32) and flows into the intermediate port of the first compressor (21a). The refrigerant flowing into the second injection branch pipe (44b) sequentially passes through the intermediate opening / closing valve (33) and the intermediate check valve (34) and flows into the intermediate port of the second compressor (21b). The refrigerant that has passed through the intermediate port and has flowed into the first and second compressors (21a, 21b) is the refrigerant in the first and second compressors (21a, 21b) (specifically, the refrigerant in the compression chamber). ). That is, the refrigerant in the first and second compressors (21a, 21b) is cooled and compressed.

  On the other hand, the refrigerant flowing into the liquid side communication pipe (13) passes through the open use side on-off valve (52) in the use side liquid refrigerant pipe (61) of the use side unit (12) and passes through the use side expansion valve (52). 53), the pressure is reduced and flows into the use-side heat exchanger (51), and the use-side heat exchanger (51) absorbs heat from the use-side air (that is, the internal air) to evaporate. Thereby, utilization side air is cooled. The refrigerant flowing out of the use side heat exchanger (51) is divided into the use side gas refrigerant pipe (62), the gas side connecting pipe (14), the gas shutoff valve (V2) and the four-way switching valve (22) of the heat source side unit (11). ) And the suction refrigerant pipe (42) in order, and is sucked into the suction ports of the first and second compressors (21a, 21b).

  In the first and second oil separators (OSa, OSb), the refrigeration oil is separated from the refrigerant (that is, the refrigerant discharged from the first and second compressors (21a, 21b)). It is stored in the first and second oil separators (OSa, OSb). The refrigerating machine oil stored in the first oil separator (OSa) flows into the oil return main pipe (47c) after passing through the first capillary tube (CTa) in the first oil return pipe (47a). The refrigerating machine oil stored in the second oil separator (OSb) passes through the oil return check valve (CVc) and the second capillary tube (CTb) in order in the second oil return pipe (47b), and then returns to the oil. It flows into the main pipe (47c). The refrigeration oil that has flowed into the oil return main pipe (47c) flows into the second injection main pipe (44n) and merges with the refrigerant that flows through the second injection main pipe (54n).

<Flow of refrigerant during defrosting operation>
Next, the refrigerant flow in the refrigerant circuit (15) during the defrosting operation will be described with reference to FIG. In the defrosting operation, the four-way switching valve (22) is set to the second state, the discharge ports of the first and second compressors (21a, 21b) and the gas side communication pipe (14) communicate with each other. The suction port of the second compressor (21a, 21b) and the gas end of the heat source side heat exchanger (23) communicate with each other.

  The refrigerant discharged from the first and second compressors (21a, 21b) is discharged from the first and second oil separators (OSa, OSb) and the first and second discharge check valves (41) in the discharge refrigerant pipe (41). After passing through CVa, CVb), the gas passes through the four-way switching valve (22) and the gas shut-off valve (V2) in order, and flows into the gas side connecting pipe (14). The refrigerant that has flowed into the gas side communication pipe (14) passes through the use side gas refrigerant pipe (62) of the use side unit (12) and flows into the use side heat exchanger (51). In 51), it dissipates heat and condenses. Thereby, the frost adhering to the use side heat exchanger (51) is heated and melted. A part of the refrigerant flowing out of the use side heat exchanger (51) passes between the open use side expansion valve (53) and the open use side on-off valve (52) in the use side liquid refrigerant pipe (61). Passing in order, the remainder passes through the use side check valve (54) in the bypass pipe (63). The refrigerant that has passed through the open-side use-side on-off valve (52) in the use-side liquid refrigerant pipe (61) joins the refrigerant that has passed through the use-side check valve (54) in the bypass pipe (63), and communicates with the liquid side. It flows into the pipe (13).

  The refrigerant that has passed through the liquid side connection pipe (13) passes through the liquid closing valve (V1) of the heat source side unit (11) and flows into the third heat source side liquid pipe (43c). The refrigerant that has flowed into the third heat source side liquid pipe (43c) flows into the first connection pipe (45) in the second midway part (Q2), and the second check valve (CV2) in the first connection pipe (45). And flows into the midway part (third midway part (Q3)) of the first heat source side liquid pipe (43a). The refrigerant that has flown into the middle of the first heat source side liquid pipe (43a) passes through the receiver (35), the second heat source side liquid pipe (43b), and the first flow path (24a) of the supercooling heat exchanger (24). And then flows into the third heat source side liquid pipe (43c). The refrigerant that has flowed into the third heat source side liquid pipe (43c) flows into the second connection pipe (46) in the fourth midway portion (Q4), and is depressurized in the heat source side expansion valve (36) to be first heat source side liquid. It flows into the middle part (5th middle part (Q5)) of the pipe (43a). The refrigerant that has flown into the middle part of the first heat source side liquid pipe (43a) flows into the heat source side heat exchanger (23), and from the heat source side air (that is, outside air) in the heat source side heat exchanger (23). It absorbs heat and evaporates. The refrigerant flowing out of the heat source side heat exchanger (23) passes through the four-way switching valve (22) and the suction refrigerant pipe (42) in order, and is sucked into the suction ports of the first and second compressors (21a, 21b). Is done.

<Operation of target temperature setting unit in cooling operation>
Next, the operation of the target temperature setting unit (84) in the cooling operation will be described with reference to FIG.

<Step (ST21)>
First, the target temperature setting unit (84) determines whether or not the use side unit (12) is in a dormant state. In this example, when the usage-side unit (12) goes from the cooling state to the dormant state in the cooling operation, the pressure of the refrigerant sucked into the first and second compressors (21a, 21b) (that is, the suction pressure) decreases. And below the low pressure range. Further, when the usage-side unit (12) is changed from the resting state to the cooling state in the cooling operation, the suction pressure rises and exceeds the low pressure range. In other words, the low pressure range is set to the suction pressure when the lower limit value can be considered that the usage-side unit (12) has gone from the cooling state to the hibernation state, and the upper limit value is cooled from the hibernation state to the usage side unit (12). It is set to the suction pressure when it can be considered that the condition has been reached. Then, the target temperature setting unit (84) determines that the use side unit (12) is in the cooling state when the suction pressure exceeds the low pressure range, and the use side when the suction pressure is below the low pressure range. It is determined that the unit (12) is in a dormant state. That is, when the suction pressure decreases and falls below the low pressure range, the target temperature setting unit (84) determines that the use side unit (12) has changed from the cooling state to the rest state, and the suction pressure increases and the low pressure When the range is exceeded, it is determined that the usage-side unit (12) has changed from the resting state to the cooling state. If it is determined that the usage-side unit (12) is in a dormant state, the process proceeds to step (ST23), and if not, the process proceeds to step (ST22).

<Step (ST22)>
When it is not determined in step (ST21) that the usage-side unit (12) is in the dormant state (that is, when the usage-side unit (12) is in the cooling state), the target temperature setting unit (84) performs the cooling operation. It is determined whether or not a predetermined time (T1) determined in advance has elapsed since the start of the process. The predetermined time (T1) is required from the start of the cooling operation until the internal temperature (Tr) decreases and the internal temperature (Tr) becomes a temperature in the vicinity of the internal set temperature (Tset). The time is set (for example, 24 hours). If it is determined that the predetermined time (T1) has elapsed, the process proceeds to step (ST23), and if not, the process proceeds to step (ST21).

  Thus, in step (ST21, ST22), the target temperature setting unit (84) has a period for reducing the internal temperature (Tr) from the start of the cooling operation (hereinafter referred to as “pull-down period (PD)”). It is determined whether or not it has elapsed. That is, in this example, the pull-down period (PD) includes the period from the start of the cooling operation to the time when the usage-side unit (12) enters the dormant state from the cooling state, and the predetermined time (T1) from the start of the cooling operation. ) Corresponds to the shorter of the period up to the point of time. And if it determines with the pull-down period (PD) having passed since the start of cooling operation, it will progress to step (ST23).

《Step (ST23)》
Next, the target temperature setting unit (84) determines whether or not the use side unit (12) is in a cooling state. In this example, the target temperature setting unit (84) determines that the use side unit (12) is in a cooling state when the suction pressure exceeds the low pressure range, and when the suction pressure is below the low pressure range, It determines with a use side unit (12) being a dormant state. That is, when the suction pressure decreases and falls below the low pressure range, the target temperature setting unit (84) determines that the use side unit (12) has changed from the cooling state to the rest state, and the suction pressure increases and the low pressure When the range is exceeded, it is determined that the usage-side unit (12) has changed from the resting state to the cooling state. If it is determined that the usage-side unit (12) is in the cooling state, the process proceeds to step (ST24).

<Step (ST24)>
Next, the target temperature setting unit (84) starts measuring the elapsed time (Ton) from the time when it is determined in step (ST23) that the use side unit (12) is in the cooling state. That is, the target temperature setting unit (84) measures the length of a period during which the use side unit (12) is in a cooling state (hereinafter referred to as “cooling continuation period”). In this example, the cooling continuation period is a period from the time when the user-side unit (12) changes from the dormant state to the cooled state to the next point when the user unit (12) changes from the cooled state to the dormant state, or the end of the pull-down period (PD) This corresponds to the period from the time point to the time point when the next use side unit (12) enters the rest state from the cooling state.

<Step (ST25)>
Next, the target temperature setting unit (84) determines whether or not the use side unit (12) is in a dormant state. If the user unit (12) is in the dormant state, the process proceeds to step (ST26), and if not, the process proceeds to step (ST29).

《Step (ST26)》
Next, the target temperature setting unit (84) has a reference value (FQref) in which the frequency index value (FQi) in the cooling continuation period (that is, the period in which the use side unit (12) is in the cooling state) is determined in advance It is determined whether it exceeds.

  The frequency index value (FQi) depends on the operating frequency (FQ) of the first compressor (21a) during the cooling continuation period. For example, as shown in FIG. 6, the frequency index value (FQi) may be a value corresponding to the average value (FQave) of the operating frequency (FQ) of the first compressor (21a) during the cooling continuation period. Alternatively, the frequency index value (FQi) may be a value corresponding to the operating frequency (FQ) of the first compressor (21a) at the time when the usage-side unit (12) changes from the cooling state to the resting state.

  The reference value (FQref) is a value that serves as a criterion for determining whether or not the operating frequency of the first compressor (21a) is relatively high. For example, the reference value (FQref) is set to a value corresponding to 60% of the maximum value (FQmax) of the operating frequency (FQ) of the first compressor (21a).

  If it is determined that the frequency index value (FQi) exceeds the reference value (FQref), the process proceeds to step (ST27), and if not, the process proceeds to step (ST23).

《Step (ST27)》
Next, the target temperature setting unit (84) determines whether or not the current target evaporation temperature (Te) is a predetermined upper limit temperature (Temax). In this example, the upper limit temperature (Temax) is the target evaporation temperature (Te) when it can be assumed that the cooling capacity of the user unit (12) can be secured so that the inside of the cabinet is appropriately cooled in the cooling operation. Is set to Specifically, the upper limit temperature (Temax) is set to a temperature obtained by adding a predetermined temperature (for example, 3 ° C.) to the reference temperature (Teref). If it is determined that the current target evaporation temperature (Te) is the upper limit temperature (Temax), the process proceeds to step (ST23), and if not, the process proceeds to step (ST28).

《Step (ST28)》
Next, the target temperature setting unit (84) corrects the target evaporation temperature (Te) so that the target evaporation temperature (Te) becomes high. Specifically, the target temperature setting unit (84) increases the target evaporation temperature (Te) by a predetermined temperature (for example, 1 ° C.). Next, the process proceeds to step (ST23).

<Step (ST29)>
On the other hand, when it is not determined in step (ST25) that the usage-side unit (12) is in a dormant state (that is, when the usage-side unit (12) is in a cooling state), the target temperature setting unit (84) It is determined whether the elapsed time (Ton) exceeds a predetermined duration threshold value (Tth). In this example, the duration threshold (Tth) is the cooling duration when the cooling load in the warehouse is considered high after the elapse of the pull-down period (PD) (the period during which the usage unit (12) is in the cooling state) ) (For example, 1 hour). If the elapsed time (Ton) exceeds the duration threshold value (Tth), the process proceeds to step (ST30). Otherwise, the process proceeds to step (ST25).

<Step (ST30)>
Next, the target temperature setting unit (84) determines whether or not the target evaporation temperature (Te) is the reference temperature (Teref). If it is determined that the target evaporation temperature (Te) is the reference temperature (Teref), the process proceeds to step (ST25), and if not, the process proceeds to step (ST31).

《Step (ST31)》
Next, the target temperature setting unit (84) corrects the target evaporation temperature (Te) so that the target evaporation temperature (Te) decreases and approaches the reference temperature (Teref) or coincides with the reference temperature (Teref). . Specifically, the target temperature setting unit (84) decreases the target evaporation temperature (Te) by a predetermined temperature (for example, 1 ° C.). Next, the process proceeds to step (ST24). That is, the elapsed time (Ton) is set to zero, and the measurement of the elapsed time (Ton) is resumed.

<Change in internal temperature>
Next, a change in the internal temperature (Tr) will be described with reference to FIG.

  When the time (t0) is reached, the operation of the refrigeration apparatus (10) is started, the cooling operation is started, and the use side unit (12) is in a cooling state. Thereby, cooling in a store | warehouse | chamber is started and store | warehouse | chamber interior temperature (Tr) falls gradually.

  When the time (t1) comes, the internal temperature (Tr) falls below the internal set temperature range, and the use side unit (12) goes from the cooling state to the dormant state. That is, the use side unit (12) performs the thermo-off operation. This ends the pull-down period (PD). That is, in the example of FIG. 7, the pull-down period (PD) is a period from the start time of the cooling operation to the time point when the usage-side unit (12) enters the sleep state from the cooling state. In addition, when the use side unit (12) is changed from the cooling state to the dormant state, the inside cooling is stopped, and the inside temperature (Tr) gradually increases.

  At time (t2), the internal temperature (Tr) exceeds the internal set temperature range, and the use side unit (12) is changed from the resting state to the cooling state. That is, the use side unit (12) performs a thermo-on operation. Thereby, the inside cooling is restarted and the inside temperature (Tr) gradually decreases.

  At time (t3), the internal temperature (Tr) falls below the internal set temperature range, and the use side unit (12) is changed from the cooling state to the inactive state. Thereby, cooling in a store | warehouse | chamber is stopped and the store | warehouse | chamber interior temperature (Tr) rises gradually.

  During the period from time (t3) to time (t4), the thermo-off operation (operation from the cooling state to the hibernation state) and the thermo-on operation (operation from the hibernation state to the cooling state) alternate Repeatedly. Thereby, the internal temperature (Tr) can be stabilized in the vicinity of the internal set temperature (Tset).

  When the time (t4) comes, the cooling operation is finished, the defrosting operation is started, and the use side unit (12) is in a heat dissipation state. Thereby, defrosting of a use side heat exchanger (51) is started. In addition, the internal temperature (Tr) gradually rises with the heat radiation in the use-side soot exchanger (51).

  At time (t5), the defrosting operation is completed and the cooling operation is restarted, and the use side unit (12) is in the cooling state. Thereby, the inside cooling is restarted and the inside temperature (Tr) gradually decreases.

  As described above, when the cooling operation is started, the use side unit (12) is in a cooling state, and the internal temperature (Tr) gradually decreases. When the pull-down period (PD) elapses from the start of the cooling operation, the internal temperature (Tr) becomes a temperature in the vicinity of the internal set temperature (Tset), and the internal cooling load decreases. That is, in the period after the pull-down period (PD) has elapsed from the start of the cooling operation (in FIG. 7, the period from time (t1) to time (t4)), the internal temperature (Tr) is the internal set temperature (Tr). It can be considered that the period is stable in the vicinity of (Tset) and the cooling load in the storage is relatively low (hereinafter referred to as “internal storage low load period”).

<Change in compressor operating frequency>
Next, a change in the operating frequency (FQ) of the first compressor (21a) during the cooling operation period will be described with reference to FIGS. FIG. 8 shows changes in the internal temperature (Tr) in the case where the target evaporation temperature (Te) is always the reference temperature (Teref) during the cooling operation period (that is, the comparative example of the refrigeration apparatus (10)). It shows the change in operating frequency (FQ). FIG. 9 shows the change in the internal temperature (Tr) in the case where the target evaporation temperature (Te) is corrected according to the frequency index value (FQi) during the cooling operation period (that is, the refrigeration apparatus (10) according to this embodiment). And changes in operating frequency (FQ).

  8 and 9, the cooling operation is started at time (t0), and the cooling operation is ended at time (t1). For convenience of explanation, in FIGS. 8 and 9, the inside of the storage in the period (pause continuation period) from the time when the usage-side unit (12) changes from the cooling state to the hibernation state to the time when the use unit (12) changes from the hibernation state to the next cooling state. A change in temperature (Tr) and a change in operating frequency (FQ) are not shown.

<< Changes in comparative examples of refrigeration equipment >>
As shown in FIG. 8, in the comparative example of the refrigeration apparatus (10), the target evaporation temperature (Te) is a constant value (reference temperature (Teref)) in the period from time (t1) to time (t2). . In addition, the operating frequency (FQ) of the first compressor (21a) is close to the maximum value (FQmax) of the operating frequency (FQ) in the pull-down period (PD), and the elapse of the pull-down period (PD) Later it gradually decreases.

<< Change in Refrigerating Apparatus According to Embodiment >>
On the other hand, as shown in FIG. 9, in the refrigeration apparatus (10) according to this embodiment, the target evaporation temperature (Te) is corrected in the period from time (t1) to time (t2). In the example of FIG. 9, the reference value (FQref) is set to a value corresponding to 60% of the maximum value (FQmax) of the operating frequency (FQ) of the first compressor (21a), and the target temperature setting unit ( 84) is configured to increase the target evaporation temperature (Te) by 1 ° C. when it is determined that the frequency index value (FQi) exceeds the reference value (FQref).

  Specifically, at time (t11), the target temperature setting unit (84) determines the frequency index value (FQi) (for example, from time (t1) to time (t1) to time (t1) It is determined that the average value (FQave) of the operating frequency (FQi) of the first compressor (21a) in the period up to t11) exceeds the reference value (FQref), and the target evaporation temperature (Teref) is increased by 1 ° C. Next, at time (t12), the target temperature setting unit (84) determines that the frequency index value (FQi) in the period from time (t11) to time (t12) exceeds the reference value (FQref). Increase target evaporation temperature (Te) by 1 ° C. Next, at time (t13), the target temperature setting unit (84) determines that the frequency index value (FQi) in the period from time (t12) to time (t13) exceeds the reference value (FQref). Increase target evaporation temperature (Te) by 1 ° C.

  In the refrigeration apparatus (10) according to this embodiment, when the target temperature setting unit (84) corrects the target evaporation temperature (Te) so that the target evaporation temperature (Te) becomes high, the compressor control unit (83) The operating frequency (FQ) of the first compressor (21a) is lowered so that the temperature of the refrigerant sucked into the first compressor (21a) increases. That is, by correcting the target evaporation temperature (Te) so that the target evaporation temperature (Te) becomes higher at the time (t11, t12, t13), the target evaporation temperature (Te) becomes a constant value. Further, it is possible to promote a decrease in the operating frequency (FQ) of the first compressor (21a) in the low load period in the refrigerator during the cooling operation (in FIG. 9, the period from time (t1) to time (t2)). .

  Note that when the operating frequency (FQ) of the first compressor (21a) is reduced, the cooling capacity of the use side unit (12) is reduced, so the period during which the use side unit (12) is in the cooling state (cooling) (Continuation period) becomes longer, and the period during which the first compressor (21a) is set in the driving state also becomes longer. Generally, the operation efficiency of the compressor tends to be higher when the compressor is driven at a low operating frequency for a long time than when the compressor is driven at a high operating frequency for a short time. Therefore, during the low load period during the cooling operation, the operating frequency (FQ) of the first compressor (21a) is decreased to improve the operating efficiency of the first compressor (21a) and to improve the refrigeration apparatus (10 ) Coefficient of performance (COP) can be improved.

<Effects of the embodiment>
As described above, the target temperature setting unit (84) sets the target evaporation temperature (Te) to the reference temperature (Teref) from the start of the cooling operation until the pull-down period (PD) elapses (step ( ST10)). Thereby, since the cooling capacity of the usage-side unit (12) can be ensured in the pull-down period (PD), the interior can be appropriately cooled in the pull-down period (PD).

  Further, the target temperature setting unit (84) sets the frequency index value (FQi) in the cooling continuation period (period in which the usage-side unit (12) is in the cooling state) after the elapse of the pull-down period (PD) to the reference value ( If it exceeds FQref), the target evaporation temperature (Te) is corrected so that the target evaporation temperature (Te) becomes higher than the reference temperature (Teref) (steps (ST21 to ST28)). As a result, the target evaporation temperature (Te) is increased when the first compressor (21a) is driven at a relatively high operating frequency during the low load period in the refrigerator after the pull-down period (PD) has elapsed. Thus, it is possible to promote a decrease in the operating frequency (FQ) of the first compressor (21a). Thereby, the coefficient of performance (COP) of the refrigeration apparatus (10) can be improved during the low load period in the refrigerator during the cooling operation.

  In addition, if the target evaporation temperature (Te) increases during the low load period during the cooling operation, the cooling capacity of the use side unit (12) decreases, so the amount of frost adhering to the use side heat exchanger (51) Can be reduced. Therefore, the defrosting operation period (period during which the defrosting operation is performed) can be shortened, and the power consumption required for the defrosting operation can be reduced.

  The target temperature setting unit (84) corrects the target evaporation temperature (Te) so that the target evaporation temperature (Te) does not exceed the upper limit temperature (Temax) (step (ST27)). If the target evaporation temperature (Te) becomes too high, the cooling capacity of the use side unit (12) may be insufficient, and the inside of the warehouse may not be properly cooled. Therefore, the target evaporation temperature (Te) can be prevented from becoming too high by correcting the target evaporation temperature (Te) so that the target evaporation temperature (Te) does not exceed the upper limit temperature (Temax). Insufficient cooling capacity of the user unit (12) due to an increase in the evaporation temperature (Te) can be prevented. Thereby, the inside of a store | warehouse | chamber can be cooled appropriately in cooling operation.

  In addition, the target temperature setting unit (84) is configured to provide a cooling continuation period (a period during which the use side unit (12) is in a cooling state) when the target evaporation temperature (Te) is higher than the reference temperature (Teref). ) Exceeds the duration threshold (Tth), the target evaporation temperature (Te) decreases so that the target evaporation temperature (Te) approaches or coincides with the reference temperature (Teref). Is corrected (steps (ST29 to ST31)). In addition, in the low load period in the warehouse after the elapse of the pull-down period (PD), heat outside the warehouse may enter the warehouse due to opening and closing of the door, and the cooling load in the warehouse may increase. Thus, when the cooling load in a store | warehouse | chamber becomes high, a cooling continuation period (period when the use side unit (12) is a cooling state) will become long. Therefore, by reducing the target evaporation temperature (Te) when the length of the cooling duration exceeds the duration threshold (Tth), the inside cooling during the inside low load period after the pull-down period (PD) has elapsed When the load becomes high, the cooling capacity of the use side unit (12) can be increased, and the internal temperature (Tr) can be quickly brought close to the internal set temperature (Tset).

  In addition, the target temperature setting unit (84) sets the target evaporation temperature (Te) to the reference temperature (Teref) after the end of the cooling operation and before the start of the defrosting operation (step (ST13)). As a result, the heat radiation capacity of the usage side unit (12) (specifically, the heat radiation capacity of the usage side heat exchanger (51)) can be ensured in the defrosting operation, so the usage side heat exchange in the defrosting operation. The defrosting of the vessel (51) can be performed appropriately.

  In addition, the pull-down period (PD) is the period from the start of the cooling operation to the time when the user unit (12) goes from the cooling state to the dormant state, and the predetermined time (T1) has elapsed from the start of the cooling operation. This corresponds to the shorter period of the period up to the time point. In addition, when the use side unit (12) goes from a cooling state to a dormant state after the start of the cooling operation, the internal temperature (Tr) may be regarded as being in the vicinity of the internal set temperature (Tset). it can. In addition, even if a sufficient time (that is, the predetermined time (T1)) has elapsed after the start of the cooling operation, it is considered that the internal temperature (Tr) is close to the internal set temperature (Tset). Can do. Therefore, the period from the start of the cooling operation to the time when the user-side unit (12) enters the dormant state from the cooling state and the period from the start of the cooling operation to the time when the predetermined time (T1) has elapsed are short. By setting this period as the pull-down period (PD), the internal temperature (Tr) is lowered in the pull-down period (DP) to bring the internal temperature (Tr) to a temperature close to the internal set temperature (Tset). be able to.

(Other embodiments)
In the above description, the period from the start of the cooling operation to the time when the user-side unit (12) enters the dormant state from the cooling state to the time when the predetermined time (T1) has elapsed from the start of the cooling operation. As an example, the shorter period of the period is set as the pull-down period (PD). However, the pull-down period (PD) indicates that the user unit (12) has changed from the cooling state to the dormant state from the start of the cooling operation. It may be a period until a certain point. That is, step (ST22) shown in FIG. 5 may be omitted. Alternatively, the pull-down period (PD) may be a period from the start of the cooling operation to the time when a predetermined time (T1) has elapsed. That is, step (ST21) shown in FIG. 5 may be omitted.

  Moreover, the above embodiment is an essentially preferable example, and is not intended to limit the scope of the present invention, its application, or its use.

  As described above, the above-described refrigeration apparatus is useful as a refrigeration apparatus that cools the interior of the refrigerator.

DESCRIPTION OF SYMBOLS 10 Refrigeration apparatus 11 Heat source side unit 12 Use side unit 15 Refrigerant circuit 21a 1st compressor (compressor)
21b Second compressor 22 Four-way switching valve 23 Heat source side heat exchanger 24 Supercooling heat exchanger 51 Usage side heat exchanger 52 Usage side on-off valve 53 Usage side expansion valve 71 Suction temperature sensor 72 Suction pressure sensor 76 Internal temperature sensor 80 controller 81 main controller 82 operation control unit 83 compressor control unit 84 target temperature setting unit 86 use side controller

Claims (7)

A heat source side unit (11) having a compressor (21a) and a heat source side heat exchanger (23);
A utilization side unit (12) provided in the warehouse having a utilization side heat exchanger (51),
The heat source side unit (11) and the use side unit (12) are connected to form a refrigerant circuit (15) in which the refrigerant circulates, and the use side unit (12) is connected to the heat source side heat exchanger (23 ) Function as a condenser, when the internal temperature (Tr) exceeds the internal set temperature range including the internal set temperature (Tset), the refrigerant is circulated through the use side heat exchanger (51). Refrigerant in the use side heat exchanger (51) when the use side heat exchanger (51) is in a cooling state that functions as an evaporator and the inside temperature (Tr) falls below the set temperature range in the inside A refrigeration apparatus configured to be in a dormant state in which the circulation of the storage is interrupted and cooling in the warehouse is suspended,
Compressor control unit (83) for controlling the operating frequency (FQ) of the compressor (21a) so that the temperature of the refrigerant sucked into the compressor (21a) in the cooling operation becomes the target evaporation temperature (Te) When,
The target evaporation temperature (Te) is lower than the internal set temperature (Tset) from the start of the cooling operation until the pull-down period (PD) for decreasing the internal temperature (Tr) elapses. Set to the reference temperature (Teref), and after the elapse of the pull-down period (PD), the operating frequency (FQ) of the compressor (21a) during the cooling continuation period in which the use side unit (12) is in the cooling state. The target evaporation temperature (Te) is set so that the target evaporation temperature (Te) becomes higher than the reference temperature (Teref) when the dependent frequency index value (FQi) exceeds a predetermined reference value (FQref). And a target temperature setting section (84) for correcting the refrigeration apparatus. In claim 1,
The frequency index value (FQi) corresponds to an average value (FQave) of operating frequencies (FQ) of the compressor (21a) during the cooling continuation period. In claim 1,
The refrigeration apparatus, wherein the frequency index value (FQi) corresponds to an operating frequency (FQ) of the compressor (21a) at a time when the use side unit (12) changes from a cooling state to a dormant state. In any one of Claims 1-3,
The refrigeration apparatus wherein the target temperature setting unit (84) corrects the target evaporation temperature (Te) so that the target evaporation temperature (Te) does not exceed a predetermined upper limit temperature (Temax). In any one of Claims 1-4,
When the target evaporation temperature (Te) is higher than the reference temperature (Teref), the target temperature setting unit (84) has a predetermined duration threshold value (Tth) ), The target evaporation temperature (Te) is corrected so that the target evaporation temperature (Te) decreases and approaches the reference temperature (Teref) or coincides with the reference temperature (Teref). Refrigeration equipment. In any one of Claims 1-5,
The target temperature setting unit (84) is an exception that allows the use side heat exchanger (51) to function as a condenser and the heat source side heat exchanger (23) to function as an evaporator after the end of the cooling operation. Before the start of the frost operation, the target evaporation temperature (Te) is set to the reference temperature (Teref). In any one of Claims 1-6,
The pull-down period (PD) is a period from the start time of the cooling operation to a time point when the usage-side unit (12) goes from a cooling state to a dormant state, and a predetermined time from the start time of the cooling operation. A refrigeration apparatus corresponding to a shorter period of the period until (T1) elapses.

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