JP2018169064A - Engine driven-type air conditioner - Google Patents

Abstract

To provide an engine driven-type air conditioner for suppressing the lowering of refrigerant suction pressure in a heating operation by a low-temperature heating operation mode.SOLUTION: A control device 60 performs: second flow rate regulation valve full-closing processing for controlling a second flow rate regulation valve 18B so that the second flow rate regulation valve 18B is fully closed when setting an operation state to a low-temperature heating mode; first flow rate regulation valve opening control processing S202 for controlling an opening of a first flow rate regulation valve 18A so that a temperature Tw of cooling water circulating in a cooling water circuit 50 is maintained at a temperature not lower than a lower limit cooling water temperature Tw0 after the execution of the second flow rate regulation valve full-closing processing; and bypass valve control processing for controlling a hot-gas bypass opening/closing valve 18E interposed in hot-gas bypass piping 38 so that refrigerant suction pressure PL is maintained at pressure not higher than lower limit pressure PL0 after the execution of the first flow rate regulation valve opening control processing.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an engine-driven air conditioner.

  The engine-driven air conditioner can be configured to include an exhaust heat recovery heat exchanger that exchanges heat between the exhaust heat of the engine and the refrigerant. In this exhaust heat recovery heat exchanger, the refrigerant can be heated by exchanging heat between the refrigerant in the refrigerant circuit and the exhaust heat of the engine, for example, engine coolant that has cooled the engine.

  Patent Document 1 discloses an engine-driven air conditioner in which an exhaust heat recovery heat exchanger and an outdoor heat exchanger are connected in parallel in a refrigerant circuit. According to the engine-driven air conditioner described in Patent Literature 1, the refrigerant flow rate flowing through the exhaust heat recovery heat exchanger and the refrigerant flow rate flowing through the outdoor heat exchanger can be adjusted according to the outside air temperature.

Japanese Patent Laid-Open No. 11-316062

(Problems to be solved by the invention)
In an engine-driven air conditioner in which an outdoor heat exchanger and a heat exchanger for exhaust heat recovery are connected in parallel, the refrigerant exchanges heat with the outside air mainly in the outdoor heat exchanger during normal heating operation. Thus, the refrigerant is heated, and the heat exchanger for exhaust heat recovery is used to supplementarily heat the refrigerant. However, when the outside air temperature becomes extremely low, not only the refrigerant cannot be sufficiently heated by the outside air in the outdoor heat exchanger, but conversely, the refrigerant heat is taken away by the outside air. For this reason, when the outside air temperature becomes extremely low, the circulation of the refrigerant from the heating operation mode (normal heating operation mode) in which the refrigerant is mainly heated in the outdoor heat exchanger to the outdoor heat exchanger is prohibited. The operation state is switched to a heating operation mode (low temperature heating operation mode) in which the refrigerant is heated only by the heat exchanger for recovering exhaust heat.

  When the refrigerant is passed through the exhaust heat recovery heat exchanger at once when the operation state is switched from the normal heating operation mode to the low temperature heating operation mode, the temperature of the cooling water for cooling the engine decreases. The temperature drop of the cooling water induces various problems. For example, as the cooling water temperature decreases, the temperature of engine oil for lubricating the engine decreases. When the temperature of the engine oil is lowered to a temperature below the operating temperature range, deterioration of the engine oil is promoted.

  If the flow rate of the refrigerant flowing through the exhaust heat recovery heat exchanger is limited when switching from normal heating operation to low temperature heating operation to prevent the occurrence of problems due to cooling water temperature drop, exhaust heat recovery The pressure (refrigerant suction pressure) of the refrigerant sucked into the compressor via the heat exchanger for use decreases. When the refrigerant suction pressure decreases, there is a shortage of refrigerant flowing through the refrigerant circuit, and there is a possibility that the engine-driven air conditioner stops operating due to a low pressure abnormality. Moreover, when the rotation speed of the compressor is reduced in order to avoid a low pressure abnormality, the heat exchange amount of the refrigerant in the indoor heat exchanger is insufficient. Therefore, in this case, the heating capacity cannot be quickly increased after the operation state is switched from the normal heating operation mode to the low temperature heating operation mode. That is, the rising performance of the heating capacity at the time of switching the operation state from the normal heating operation mode to the low temperature heating operation mode is deteriorated. In order to prevent such deterioration of the start-up performance, it is desirable to suppress a decrease in the refrigerant suction pressure in the heating operation in the low-temperature heating operation mode.

  An object of the present invention is to provide an engine-driven air conditioner configured to suppress a decrease in refrigerant suction pressure during heating operation in a low-temperature heating operation mode.

(Means for solving the problem)
The present invention relates to an engine (10) that generates driving force, a cooling water circuit (50) through which cooling water for cooling the engine flows, an inlet (11a) for sucking refrigerant, and an outlet for discharging refrigerant. A compressor (11b) that operates by the driving force of the engine, sucks the refrigerant from the suction port, compresses the sucked refrigerant, and discharges the compressed refrigerant from the discharge port; An indoor heat exchanger (22) that is connected to the discharge outlet of the refrigerant through the first refrigerant pipe (31, 32) and exchanges heat between the refrigerant flowing from the first refrigerant pipe and the room air during heating operation. The refrigerant that is connected to the compressor via the second refrigerant pipe (34) and is connected to the compressor inlet via the third refrigerant pipe (33, 35, 36) and flows in from the second refrigerant pipe during the heating operation Outdoor heat exchange that exchanges heat with the outside air (14), a fourth refrigerant pipe (37) connecting the second refrigerant pipe and the third refrigerant pipe, a refrigerant interposed in the fourth refrigerant pipe, and a cooling water flowing through the cooling water circuit. A heat exchanger (15) for exhaust heat recovery that exchanges heat with the first flow rate adjusting valve (15) that is interposed in the fourth refrigerant pipe and that can adjust the flow rate of the refrigerant that flows to the heat exchanger for exhaust heat recovery during heating operation ( 18A), a second flow rate adjustment valve (18B) interposed in the second refrigerant pipe and capable of adjusting the flow rate of the refrigerant flowing from the second refrigerant pipe into the outdoor heat exchanger during the heating operation, and the outdoor heat during the heating operation A bypass pipe (38, 39) connecting the first refrigerant pipe or the second refrigerant pipe and the third refrigerant pipe so as to bypass the exchanger, and a bypass valve (18E, 18C) interposed in the bypass pipe; Control the first flow control valve, second flow control valve, and bypass valve An engine-driven air conditioner (1) comprising a control device (60), wherein the control device uses an outdoor heat exchanger when the outdoor air temperature (Ta) is equal to or lower than the temperature during heating operation. The second flow rate adjustment valve is controlled so that the second flow rate adjustment valve is fully closed when it is determined that the outside temperature at which the refrigerant cannot be sufficiently heated is equal to or lower than a predetermined threshold outside temperature (Ta0). After the two flow rate regulating valve full closing process (S201) and the second flow rate regulating valve full closing process, the temperature (Tw) of the cooling water flowing through the cooling water circuit is equal to or higher than a predetermined lower limit cooling water temperature (Tw0). During the execution of the first flow rate adjustment valve opening degree control process (S202) for controlling the opening degree of the first flow rate adjustment valve so as to be maintained at the temperature, and the first flow rate adjustment valve opening degree control process, the air is sucked into the compressor The pressure (PL) of the refrigerant to be An engine-driven air conditioner that performs a bypass valve control process (S302, S303, S402) for controlling the bypass valve so as to be maintained at a pressure equal to or higher than a lower limit pressure (PL0).

  According to the engine-driven air conditioner according to the present invention, when the outside air temperature is equal to or lower than the threshold outside air temperature during the heating operation, that is, when the heating operation in the low temperature heating operation mode is recommended, the second flow rate adjustment valve is Fully closed. Thereby, the distribution | circulation of the refrigerant | coolant to an outdoor heat exchanger is prohibited. Thereafter, the flow rate of the refrigerant flowing through the heat exchanger for exhaust heat recovery is adjusted so that the coolant temperature is maintained at a temperature equal to or higher than the lower limit coolant temperature by opening control of the first flow rate adjustment valve. During the opening degree control of the first flow rate adjusting valve, the bypass pipe connecting the first refrigerant pipe and the third refrigerant pipe or the bypass pipe connecting the second refrigerant pipe and the third refrigerant pipe is interposed. The bypass valve is controlled. By controlling the bypass valve and supplying the refrigerant from the first refrigerant pipe or the second refrigerant pipe to the third refrigerant pipe, the pressure of the refrigerant sucked from the third refrigerant pipe into the compressor (refrigerant suction pressure) is increased. The pressure is maintained at a pressure equal to or higher than the lower limit pressure.

  As described above, when the control device controls the bypass valve as described above in the low temperature heating operation mode, a decrease in the refrigerant suction pressure when the heating operation is performed in the low temperature heating operation mode is suppressed.

  In the above invention, the lower limit cooling water temperature is determined in advance as a temperature at which occurrence of some malfunction is concerned due to a decrease in the temperature of the cooling water when the temperature of the cooling water flowing through the cooling water circuit is equal to or lower than that temperature. Good. The lower limit pressure may be determined in advance as a pressure that may cause a low pressure abnormality when the refrigerant suction pressure is equal to or lower than the pressure.

  In the present invention, the bypass pipe may be a hot gas bypass pipe (38) connecting the first refrigerant pipe (31) and the third refrigerant pipe (35). The bypass valve may be a hot gas bypass on / off valve (18E) interposed in the hot gas bypass pipe. In this case, the control device may control the opening and closing of the hot gas bypass valve so that the pressure of the refrigerant sucked into the compressor is maintained at a pressure equal to or higher than the lower limit pressure in the bypass valve control process.

  According to this, when the hot gas bypass on / off valve is opened by the bypass valve control process, the refrigerant is supplied from the first refrigerant pipe to the third refrigerant pipe via the hot gas bypass pipe. For this reason, the pressure of the refrigerant | coolant suck | inhaled by the compressor from 3rd refrigerant | coolant piping can be maintained to the pressure more than a minimum pressure.

  In the present invention, the bypass pipe may be a supercooling pipe (39) connecting the second refrigerant pipe (34) and the third refrigerant pipe (35). The bypass valve may be a third flow rate adjustment valve (18C) interposed in the subcooling pipe. In this case, a supercooling heat exchanger (16) for exchanging heat between the refrigerant flowing through the second refrigerant pipe and the refrigerant flowing through the supercooling pipe is interposed in the middle of the supercooling pipe. And a control apparatus is good to control the opening degree of a 3rd flow regulating valve so that the pressure of the refrigerant | coolant suck | inhaled by a compressor may be maintained in the pressure more than a minimum pressure by bypass valve control processing.

  When the opening degree of the third flow rate adjusting valve is increased or decreased, the supply amount of the refrigerant flowing from the second refrigerant pipe to the third refrigerant pipe via the supercooling pipe increases or decreases. Therefore, by controlling the opening of the third flow rate adjustment valve in the bypass valve control process, the pressure of the refrigerant sucked into the compressor from the third refrigerant pipe is maintained at a pressure equal to or higher than the lower limit pressure. The flow rate of the refrigerant supplied from the second refrigerant pipe to the third refrigerant pipe via the supercooling pipe can be adjusted.

It is a figure which shows schematic structure of an air conditioning apparatus. It is a flowchart which shows the flow of an operation mode setting process routine. It is a flowchart which shows the flow of a low-temperature heating operation control processing routine. It is a flowchart which shows the flow of a low voltage | pressure avoidance control processing routine. It is a flowchart which shows the flow of the low voltage | pressure avoidance control processing routine which concerns on a modification.

  Embodiments of the present invention will be described below with reference to the drawings. Drawing 1 is a figure showing the schematic structure of the engine drive type air harmony device concerning an embodiment. As shown in FIG. 1, the engine-driven air conditioner 1 according to the embodiment includes an outdoor unit 1a and an indoor unit 1b. The outdoor unit 1a is installed outdoors, and the indoor unit 1b is installed indoors. In this embodiment, the engine-driven air conditioner 1 has a plurality of indoor units 1b.

  The outdoor unit 1a includes an engine 10 that generates driving force, a compressor 11, an oil separator 12, a four-way valve 13, an outdoor heat exchanger 14, a waste heat recovery heat exchanger 15, and supercooling heat exchange. , Accumulator 17, first flow rate adjustment valve 18A, second flow rate adjustment valve 18B, third flow rate adjustment valve 18C, hot gas bypass opening / closing valve 18E, accumulator / four-way valve bypass opening / closing valve 18F, A control device 60 and a cooling water circuit 50 are provided. Each of the plurality of indoor units 1 b includes an indoor electronic expansion valve 21 and an indoor heat exchanger 22. Among the above-described configurations, the above-described devices other than the engine 10, the cooling water circuit 50, and the control device 60 are connected by a refrigerant pipe. Refrigerant circuit 100 is configured by each device and refrigerant piping except engine 10, cooling water circuit 50 and control device 60. A refrigerant flows in the refrigerant circuit 100.

  The engine 10 generates driving force by burning gaseous fuel such as LPG or LNG. In addition, it can replace with gaseous fuel and can also use liquid fuels, such as gasoline, or a solid fuel.

  The cooling water circuit 50 includes a cooling water passage 51 formed inside the engine 10, a cooling water pipe 52 connecting one opening end of the cooling water passage 51 and the other opening end, and a halfway of the cooling water pipe 52. And a cooling water pump 53 interposed. When the cooling water pump 53 is driven, cooling water for cooling the engine 10 flows in the cooling water circuit 50. As the cooling water flows through the cooling water passage 51, the engine 10 is cooled. The cooling water pipe 52 of the cooling water circuit 50 is connected to a heat exchanger 15 for exhaust heat recovery described later.

  The compressor 11 is connected to the engine 10 and operates upon receiving the driving force of the engine 10. The compressor 11 has a suction port 11a and a discharge port 11b. When the compressor 11 is operated by the driving force of the engine 10, the compressor 11 sucks the refrigerant gas from the suction port 11a, compresses the refrigerant gas therein, and discharges the compressed refrigerant gas from the discharge port 11b. In addition, although one compressor is shown in FIG. 1, the number of the compressors provided in one outdoor unit 1a may be plural.

  The discharge port 11 b of the compressor 11 is connected to one end of the discharge pipe 31. An oil separator 12 is interposed in the middle of the discharge pipe 31. The oil separator 12 collects oil (refrigeration oil) discharged from the discharge port 11b of the compressor 11. The recovered oil is returned to the suction port 11 a side of the compressor 11.

  The four-way valve 13 is connected to the other end of the discharge pipe 31. The four-way valve 13 has a first port 13a, a second port 13b, a third port 13c, and a fourth port 13d. The discharge port 11 b of the compressor 11 is connected to the first port 13 a of the four-way valve 13 via the discharge pipe 31. The indoor heat exchanger 22 installed in the room is connected to the second port 13b of the four-way valve 13 via the indoor unit side pipe 32. The outdoor heat exchanger 14 is connected to the third port 13 c of the four-way valve 13 via the outdoor unit side pipe 33. The accumulator 17 is connected to the fourth port 13d of the four-way valve 13 via an accumulator inlet pipe 35.

  The four-way valve 13 has a switching state during heating in which the first port 13a communicates with the second port 13b and the third port 13c communicates with the fourth port 13d, and the first port 13a communicates with the third port 13c. The cooling switching state in which the two ports 13b communicate with the fourth port 13d can be selectively realized. When the engine-driven air conditioner 1 performs a heating operation, the switching state of the four-way valve 13 is set to a switching state during heating. When the engine-driven air conditioner 1 performs a cooling operation, the switching state of the four-way valve 13 switches to a cooling time. Put into a state.

  When the switching state of the four-way valve 13 is the switching state during heating, the discharge port 11b of the compressor 11 connected to the first port 13a of the four-way valve 13 via the discharge pipe 31 and the second port of the four-way valve 13 The indoor heat exchanger 22 connected via the indoor unit side pipe 32 is connected to 13b. That is, the indoor heat exchanger 22 is connected to the discharge port 11b of the compressor 11 via the discharge pipe 31 and the indoor unit side pipe 32 during the heating operation. The discharge pipe 31 and the indoor unit side pipe 32 correspond to the first refrigerant pipe of the present invention.

  Further, when the switching state of the four-way valve 13 is the switching state during heating, the outdoor heat exchanger 14 connected to the third port 13c of the four-way valve 13 via the outdoor unit side pipe 33 and the four-way valve 13 The accumulator 17 connected to the four ports 13d via the accumulator inlet pipe 35 is connected. As will be described later, the accumulator 17 is connected to the suction port 11a of the compressor 11 via the suction pipe 36. That is, the outdoor heat exchanger 14 is connected to the suction port 11a of the compressor 11 through the outdoor unit side pipe 33, the accumulator inlet pipe 35, and the suction pipe 36 during the heating operation. The outdoor unit side pipe 33, the accumulator inlet pipe 35, and the suction pipe 36 correspond to the third refrigerant pipe of the present invention.

  The outdoor heat exchanger 14 connected to the third port 13c of the four-way valve 13 via the outdoor unit side pipe 33 exchanges heat between the refrigerant flowing inside and the outside air. The outdoor heat exchanger 14 is connected to the indoor heat exchanger 22 via an intermediate pipe 34. This intermediate pipe 34 corresponds to the second refrigerant pipe of the present invention. The indoor heat exchanger 22 exchanges heat between the refrigerant circulating in the interior and the room air.

  The supercooling heat exchanger 16 is interposed in the middle of the intermediate pipe 34. In addition, the indoor electronic expansion valve 21 is interposed in the intermediate pipe 34 on the indoor unit 1b side. The indoor electronic expansion valve 21 expands the refrigerant flowing therethrough. The opening degree of the indoor electronic expansion valve 21 can be adjusted. The flow rate of the refrigerant flowing through the indoor heat exchanger 22 is adjusted by adjusting the opening degree of the indoor electronic expansion valve 21. The opening degree of the indoor electronic expansion valve 21 is controlled based on an instruction from a microcomputer (not shown) provided on the indoor unit 1b side, except in special cases.

  The portion of the intermediate pipe 34 between position A and position B is branched into two pipes (pipe L1 and pipe L2). A one-way valve 18D is interposed in the pipe L1, and a second flow rate adjusting valve 18B is interposed in the pipe L2. During the cooling operation, the refrigerant flows through the pipe L1, and during the heating operation, the refrigerant flows through the pipe L2. The second flow rate adjusting valve 18B expands the refrigerant flowing therethrough. Moreover, the opening degree of the second flow rate adjusting valve 18B can be adjusted. By adjusting the opening of the second flow rate adjusting valve 18B, the flow rate of the refrigerant flowing into the outdoor heat exchanger 14 from the intermediate pipe 34 during the heating operation is adjusted.

  The accumulator 17 connected to the fourth port 13d of the four-way valve 13 via the accumulator inlet pipe 35 is further connected to the suction port 11a of the compressor 11 via the suction pipe 36. The accumulator 17 introduces a refrigerant from the accumulator inlet pipe 35 side, and gas-liquid separates the introduced refrigerant. The low-temperature and low-pressure gas refrigerant separated from the liquid refrigerant in the accumulator 17 is supplied to the suction port 11 a of the compressor 11 via the suction pipe 36.

  The intermediate pipe 34 (second refrigerant pipe) and the accumulator inlet pipe 35 (third refrigerant pipe) are connected by a fourth refrigerant pipe 37. As shown in FIG. 1, the connection position C of the fourth refrigerant pipe 37 to the intermediate pipe 34 is closer to the outdoor heat exchanger 14 than the portion of the intermediate pipe 34 where the supercooling heat exchanger 16 is interposed. Is the position. The fourth refrigerant pipe 37 connects the intermediate pipe 34 and the accumulator inlet pipe 35 so that the refrigerant flowing through the intermediate pipe 34 bypasses the outdoor heat exchanger 14 during the heating operation. The fourth refrigerant pipe 37 is provided with the first flow rate adjusting valve 18A and the exhaust heat recovery heat exchanger 15. The refrigerant flows from the fourth refrigerant pipe 37 into the exhaust heat recovery heat exchanger 15. Moreover, the opening degree of the first flow rate adjusting valve 18A can be adjusted. By adjusting the opening degree of the first flow rate adjusting valve 18A, the flow rate of the refrigerant flowing through the fourth refrigerant pipe 37 and flowing into the exhaust heat recovery heat exchanger 15 is adjusted.

  The heat exchanger 15 for exhaust heat recovery is configured by, for example, a plate heat exchanger. Further, as described above, the cooling water in the cooling water circuit 50 also circulates in the exhaust heat recovery heat exchanger 15. Accordingly, in the heat exchanger 15 for exhaust heat recovery, heat is exchanged between the refrigerant flowing through the heat exchanger 15 and the cooling water flowing through the cooling water circuit 50. The engine coolant flowing through the heat exchanger 15 for exhaust heat recovery is heated by removing heat from the engine 10. Therefore, the refrigerant flowing through the fourth refrigerant pipe 37 is heated by the engine cooling water in the exhaust heat recovery heat exchanger 15.

  Further, the discharge pipe 31 and the accumulator inlet pipe 35 are connected by a hot gas bypass pipe 38 (bypass pipe). The hot gas bypass pipe 38 connects the discharge pipe 31 and the accumulator inlet pipe 35 so as to bypass the outdoor heat exchanger 14 and the indoor heat exchanger 22. A hot gas bypass opening / closing valve 18E (bypass valve) is interposed in the hot gas bypass pipe 38. When the hot gas bypass opening / closing valve 18E is opened, the discharge pipe 31 and the accumulator inlet pipe 35 communicate with each other via the hot gas bypass pipe 38.

  The fourth refrigerant pipe 37 and the accumulator inlet pipe 35 (third refrigerant pipe) are connected by a supercooling pipe 39 (bypass pipe). As shown in FIG. 1, the connection position D of the subcooling pipe 39 to the fourth refrigerant pipe 37 includes the connection position C of the fourth refrigerant pipe 37 to the intermediate pipe 34 and the exhaust heat recovery heat exchanger 15. It is a position between the intervening parts. The first flow rate adjusting valve 18A is interposed at a position between the position D of the fourth refrigerant pipe 37 and the portion where the exhaust heat recovery heat exchanger 15 is interposed. As can be seen from FIG. 1, the supercooling pipe 39 bypasses the outdoor heat exchanger 14 via the fourth refrigerant pipe 37, and the intermediate pipe 34 (second refrigerant pipe) and the accumulator inlet pipe 35 (second pipe). 3 refrigerant pipes).

  A third flow rate adjustment valve 18C (bypass valve) and the supercooling heat exchanger 16 are interposed in the supercooling pipe 39. As described above, the supercooling heat exchanger 16 is also interposed in the intermediate pipe 34. In the supercooling heat exchanger 16, the refrigerant flowing through the intermediate pipe 34 and the refrigerant flowing through the supercooling pipe 39 exchange heat. The opening degree of the third flow rate adjusting valve 18C can be adjusted. By adjusting the opening degree of the third flow rate adjusting valve 18C, the flow rate of the refrigerant flowing through the supercooling pipe 39 and flowing into the supercooling heat exchanger 16 is adjusted.

  The third flow rate adjusting valve 18C has a function of expanding the refrigerant flowing therethrough. Therefore, the refrigerant that has flowed from the intermediate pipe 34 to the supercooling pipe 39 via the fourth refrigerant pipe 37 is expanded by the third flow rate adjusting valve 18C to be lowered in temperature. The refrigerant thus lowered in temperature and the refrigerant flowing through the intermediate pipe 34 exchange heat. Therefore, in the supercooling heat exchanger 16, the refrigerant flowing through the intermediate pipe 34 is cooled (supercooled), and the refrigerant flowing through the subcooling pipe 39 is heated.

  Further, the indoor unit side pipe 32 (first refrigerant pipe) and the suction pipe 36 (third refrigerant pipe) are connected by an accumulator / four-way valve bypass pipe 40. In the middle of the accumulator / four-way valve bypass pipe 40, an accumulator / four-way valve bypass opening / closing valve 18F is interposed. When the accumulator / four-way valve bypass opening / closing valve 18F is opened, the indoor unit side pipe 32 and the suction pipe 36 communicate with each other.

  The control device 60 is mainly composed of a microcomputer comprising a CPU, ROM, RAM, etc., and at least the rotational speed of the compressor 11 (or the rotational speed of the engine 10), the switching operation of the four-way valve 13, the hot gas bypass on-off valve 18E. The opening / closing operation of the first flow rate adjusting valve 18A, the opening amount of the second flow rate adjusting valve 18B, the opening amount of the third flow rate adjusting valve 18C, and the opening / closing operation of the accumulator / four-way valve bypass opening / closing valve 18F are controlled.

  Further, temperature sensors and pressure sensors are attached to various portions of the refrigerant circuit 100. Among these various sensors, the suction temperature sensor 61 is attached to the suction pipe 36 and detects the temperature of the refrigerant sucked into the compressor 11 from the suction pipe 36 (refrigerant suction temperature). The discharge temperature sensor 62 is attached to the discharge pipe 31 and detects the temperature of the refrigerant discharged from the compressor 11 to the discharge pipe 31 (refrigerant discharge temperature). The suction pressure sensor 63 is attached to the suction pipe 36 and detects the pressure of the refrigerant (refrigerant suction pressure PL) drawn from the suction pipe 36 into the suction port 11a of the compressor 11. The first opening degree sensor 64 is attached to the first flow rate adjustment valve 18A, and detects the opening degree of the first flow rate adjustment valve 18A. The second opening degree sensor 65 is attached to the second flow rate adjustment valve 18B and detects the opening degree of the second flow rate adjustment valve 18B. The third opening degree sensor 66 is attached to the third flow rate adjusting valve 18C and detects the opening degree of the third flow rate adjusting valve 18C. In addition, a temperature sensor, a pressure sensor, or the like may be attached to other parts of the refrigerant circuit 100 or in the vicinity thereof. Various information detected by each sensor is input to the control device 60.

  A cooling water temperature sensor 67 is attached to a portion of the cooling water pipe 52 of the cooling water circuit 50 where the cooling water flowing out of the cooling water passage 51 formed in the engine 10 flows. The coolant temperature sensor 67 detects the coolant temperature Tw after cooling the engine 10. Information regarding the coolant temperature Tw detected by the coolant temperature sensor 67 is input to the control device 60.

  An outdoor temperature sensor 68 is attached to the outdoor unit 1a. The outside air temperature sensor 68 detects the outside air temperature Ta. Information regarding the outside air temperature Ta detected by the outside air temperature sensor 68 is input to the control device 60.

  Next, the air conditioning operation of the engine-driven air conditioner 1 having the above configuration will be described. In the engine-driven air conditioner 1 according to the present embodiment, the switching state of the four-way valve 13 during heating operation is switched to the heating switching state, and the switching state of the four-way valve 13 during cooling operation is switched to the cooling switching state. The control device 60 controls the switching operation of the four-way valve 13. In FIG. 1, the main flow of the refrigerant during the cooling operation is indicated by a dotted arrow, and the main flow of the refrigerant during the heating operation is indicated by a solid arrow.

  First, the heating operation will be described. When the compressor 11 is activated by driving the engine 10, the compressor 11 sucks the low-temperature low-pressure gas refrigerant in the suction pipe 36 from the suction port 11a and compresses the sucked low-temperature low-pressure gas refrigerant to generate a high-temperature high-pressure gas refrigerant. To do. Then, the generated high-temperature and high-pressure gas refrigerant is discharged from the discharge port 11b. The high-temperature high-pressure gas refrigerant discharged from the discharge port 11b flows through the discharge pipe 31.

  An oil separator 12 is interposed in the middle of the discharge pipe 31. The oil separator 12 collects oil mixed in the refrigerant flowing through the discharge pipe 31. A hot gas bypass pipe 38 is connected in the middle of the discharge pipe 31. When the hot gas bypass opening / closing valve 18E interposed in the hot gas bypass pipe 38 is open, a part of the high-temperature high-pressure gas refrigerant in the discharge pipe 31 flows through the hot gas bypass pipe 38 and reaches the accumulator inlet pipe 35. Further, it is introduced into the accumulator 17 from the accumulator inlet pipe 35. When the hot gas bypass on-off valve 18E is closed, all of the high-temperature high-pressure gas refrigerant in the discharge pipe 31 enters the first port 13a of the four-way valve 13.

  Since the switching state of the four-way valve 13 is set to a switching state during heating operation, the first port 13a of the four-way valve 13 communicates with the second port 13b during heating operation. Therefore, the high-temperature high-pressure gas refrigerant that has entered the first port 13 a of the four-way valve 13 from the discharge pipe 31 flows out of the four-way valve 13 from the second port 13 b and flows into the indoor unit side pipe 32. And the refrigerant | coolant which flows through the indoor unit side piping 32 flows in into the indoor heat exchanger 22 by the side of the indoor unit 1b. The high-temperature and high-pressure gas refrigerant that has flowed into the indoor heat exchanger 22 exchanges heat with the indoor air while circulating in the indoor heat exchanger 22, and heat is discharged into the room to condense. That is, the indoor heat exchanger 22 functions as a condenser during heating operation. At this time, the room air is warmed by the heat discharged from the high-temperature and high-pressure gas refrigerant, and the room is heated.

  A part of the refrigerant condensed by discharging heat to the indoor air is liquefied and flows out from the indoor heat exchanger 22 to the intermediate pipe 34. And it expands with the indoor side electronic expansion valve 21 interposed in the middle of the intermediate pipe 34, and is made into intermediate pressure, and is further liquefied by passing the supercooling heat exchanger 16 by the side of the outdoor unit 1a after that. . A part of the refrigerant flowing out of the supercooling heat exchanger 16 flows through the fourth refrigerant pipe 37 connected to the intermediate pipe 34 from the intermediate pipe 34. The refrigerant flowing from the intermediate pipe 34 through the fourth refrigerant pipe 37 enters the exhaust heat recovery heat exchanger 15 provided in the fourth refrigerant pipe 37, and the exhaust heat recovery heat exchanger 15 causes cooling water and heat to flow. Exchange. The flow rate of the refrigerant flowing into the exhaust heat recovery heat exchanger 15 is adjusted by the first flow rate adjusting valve 18A interposed in the fourth refrigerant pipe 37. The refrigerant that has exchanged heat with the cooling water in the heat exchanger 15 for exhaust heat recovery flows from the fourth refrigerant pipe 37 through the accumulator inlet pipe 35 and is introduced into the accumulator 17. In addition, a part of the refrigerant flowing into the fourth refrigerant pipe 37 from the intermediate pipe 34 flows through the supercooling pipe 39 and flows into the supercooling heat exchanger 16. Then, the supercooling heat exchanger 16 exchanges heat with the refrigerant flowing through the intermediate pipe 34 and then flows into the accumulator inlet pipe 35. The flow rate of the refrigerant flowing from the supercooling pipe 39 into the supercooling heat exchanger 16 is adjusted by the third flow rate adjusting valve 18C interposed in the supercooling pipe 39.

  On the other hand, the refrigerant that did not flow from the intermediate pipe 34 to the fourth refrigerant pipe 37 flows through the pipe L2 of the intermediate pipe 34 and passes through the second flow rate adjustment valve 18B interposed in the pipe L2. The refrigerant is expanded and the pressure is reduced by the second flow rate adjusting valve 18B. The refrigerant that has passed through the second flow rate adjusting valve 18B flows into the outdoor heat exchanger 14, exchanges heat with the outside air while flowing through the outdoor heat exchanger 14, and takes away the heat of the outside air to evaporate. That is, the outdoor heat exchanger 14 functions as an evaporator during heating operation. In addition, the flow rate of the refrigerant flowing into the outdoor heat exchanger 14 from the intermediate pipe 34 is adjusted by the second flow rate adjustment valve 18B.

  The refrigerant evaporated by taking the heat of the outdoor air in the outdoor heat exchanger 14 is partially vaporized and flows out from the outdoor heat exchanger 14 to the outdoor unit side pipe 33, and then enters the third port 13 c of the four-way valve 13. Since the third port 13c of the four-way valve 13 communicates with the fourth port 13d during the heating operation, the refrigerant that has entered the third port 13c of the four-way valve 13 from the outdoor unit side pipe 33 passes through the fourth port 13d. And flows through the accumulator inlet pipe 35. The refrigerant that has flowed through the accumulator inlet pipe 35 is introduced into the accumulator 17. In the accumulator 17, the introduced refrigerant is separated into gas and liquid, and the low-temperature and low-pressure gas refrigerant separated from the liquid refrigerant flows into the suction pipe 36. Then, the gas refrigerant in the suction pipe 36 returns to the suction port 11 a of the compressor 11. By repeating such a refrigerant circulation cycle, room heating is continued.

  In the heating operation, the accumulator / four-way valve bypass opening / closing valve 18F is closed in principle. Therefore, the refrigerant flowing through the indoor unit side pipe 32 during the heating operation does not flow through the accumulator / four-way valve bypass pipe 40.

  Next, the cooling operation will be described. When the compressor 11 is operated, the high-temperature and high-pressure gas refrigerant is discharged from the discharge port 11 b of the compressor 11 to the discharge pipe 31. The high-temperature high-pressure gas refrigerant flows through the discharge pipe 31 and enters the first port 13 a of the four-way valve 13 via the oil separator 12.

  Since the switching state of the four-way valve 13 is the switching state during cooling operation, the first port 13a of the four-way valve 13 communicates with the third port 13c during cooling operation. Therefore, the high-temperature high-pressure gas refrigerant that has entered the first port 13a of the four-way valve 13 from the discharge pipe 31 flows out of the four-way valve 13 from the third port 13c and flows into the outdoor unit side pipe 33. The high-temperature and high-pressure gas refrigerant that has flowed into the outdoor unit side pipe 33 flows into the outdoor heat exchanger 14. The refrigerant that has flowed into the outdoor heat exchanger 14 exchanges heat with the outside air while circulating in the outdoor heat exchanger 14, and heat is discharged to the outside air to condense. That is, the outdoor heat exchanger 14 functions as a condenser during the cooling operation.

  The refrigerant that is condensed by discharging heat to the outside air is partially liquefied and flows out from the outdoor heat exchanger 14 to the intermediate pipe 34. The liquid refrigerant (or gas-liquid two-phase refrigerant) that has flowed out to the intermediate pipe 34 passes through the pipe L1. The refrigerant that has passed through the pipe L1 passes through the supercooling heat exchanger 16 that is interposed in the intermediate pipe 34. Further, a part of the refrigerant that has passed through the pipe L1 flows from the intermediate pipe 34 through the fourth refrigerant pipe 37 through the supercooling pipe 39, and further, the supercooling heat exchange interposed in the supercooling pipe 39. Pass through vessel 16. Then, in the supercooling heat exchanger 16, the refrigerant flowing through the intermediate pipe 34 and the refrigerant flowing through the supercooling pipe 39 exchange heat. By this heat exchange, the refrigerant flowing through the intermediate pipe 34 is supercooled. Further, during the cooling operation, the first flow rate adjustment valve 18A is opened as necessary (for example, when the refrigerant temperature decreases because the outside air temperature is low during cooling). When the first flow rate adjustment valve 18A is opened, the refrigerant flowing through the fourth refrigerant pipe 37 flows to the exhaust heat recovery heat exchanger 15 via the first flow rate adjustment valve 18A. The refrigerant exchanges heat with the cooling water in the heat exchanger 15 for exhaust heat recovery. The refrigerant heat-exchanged in the heat exchanger 15 for exhaust heat recovery flows through the accumulator inlet pipe 35 and is introduced into the accumulator 17.

  Of the refrigerant passing through the supercooling heat exchanger 16, the refrigerant passing through the supercooling heat exchanger 16 from the supercooling pipe 39 side then flows into the accumulator inlet pipe 35. On the other hand, the refrigerant that has passed through the supercooling heat exchanger 16 from the intermediate pipe 34 side then passes through the indoor-side electronic expansion valve 21 interposed in the intermediate pipe 34 on the indoor unit 1b side. The refrigerant is expanded by the indoor-side electronic expansion valve 21, and the pressure is reduced so as to easily evaporate. The refrigerant whose pressure has been reduced by the indoor electronic expansion valve 21 then flows into the indoor heat exchanger 22. The refrigerant that has flowed into the indoor heat exchanger 22 exchanges heat with the indoor air while flowing through the indoor heat exchanger 22, and takes the heat of the indoor air to evaporate. That is, the indoor heat exchanger 22 functions as an evaporator during the cooling operation. At this time, the refrigerant removes heat from the room air, thereby cooling the room air and cooling the room.

  A part of the refrigerant evaporated by taking the heat of the indoor air is vaporized, flows out from the indoor heat exchanger 22 to the indoor unit side pipe 32, and goes to the four-way valve 13. Then, it enters the second port 13b of the four-way valve 13. Since the second port 13b of the four-way valve 13 communicates with the fourth port 13d during cooling operation, the refrigerant that has entered the second port 13b of the four-way valve 13 from the indoor unit side pipe 32 passes through the fourth port 13d. 13 flows out and flows into the accumulator inlet pipe 35. The refrigerant that has flowed through the accumulator inlet pipe 35 is introduced into the accumulator 17. In the accumulator 17, the introduced refrigerant is separated into gas and liquid, and the separated low-temperature and low-pressure gas refrigerant flows out to the suction pipe 36. Then, the gas refrigerant that has flowed into the suction pipe 36 from the accumulator 17 returns to the suction port 11 a of the compressor 11. By repeating such a refrigerant circulation cycle, room cooling is continued.

  Further, during the cooling operation, the accumulator / four-way valve bypass opening / closing valve 18F is opened as necessary. When the accumulator / four-way valve bypass opening / closing valve 18F is opened, a part of the refrigerant flowing out of the indoor heat exchanger 22 and flowing through the indoor unit side pipe 32 flows into the accumulator / four-way valve bypass pipe 40. The refrigerant flowing into the accumulator / four-way valve bypass pipe 40 flows from the accumulator / four-way valve bypass pipe 40 to the suction pipe 36, and is then sucked into the compressor 11 from the suction port 11 a of the compressor 11. The refrigerant flowing through the accumulator / four-way valve bypass pipe 40 during the cooling operation is sucked into the compressor 11 without passing through the four-way valve 13 and the accumulator 17. For this reason, the pressure loss which arises by passing through the four-way valve 13 and the accumulator 17 can be reduced.

  During the heating operation and the cooling operation described above, the flow rate of the refrigerant flowing through the refrigerant circuit 100 is normally controlled based on the air conditioning load. In this case, the control device 60 determines the rotation speed of the compressor 11, the opening degree of the first flow rate adjustment valve 18A, the opening degree of the second flow rate adjustment valve 18B, and the opening degree of the third flow rate adjustment valve 18C based on the air conditioning load. Determine the target opening. And the control apparatus 60 controls the opening degree of each valve so that the opening degree of each valve mentioned above may turn into the target opening degree while controlling the compressor 11 to act | operate with the determined rotation speed. Note that the air conditioning load is the work amount of the refrigerant required for the required air conditioning. The air conditioning load can be obtained, for example, by the product of the temperature difference between the room temperature and the set temperature and the operating capacity of the indoor heat exchanger 22.

  Further, as described above, a part of the refrigerant flowing out of the indoor heat exchanger 22 and flowing through the intermediate pipe 34 during the heating operation flows through the fourth refrigerant pipe 37 from the intermediate pipe 34, and the exhaust heat recovery heat exchanger 15. To the accumulator inlet pipe 35 (third refrigerant pipe). Further, the refrigerant that did not flow from the intermediate pipe 34 to the fourth refrigerant pipe 37 flows to the accumulator inlet pipe 35 (third refrigerant pipe) via the outdoor heat exchanger 14. Therefore, during the heating operation, the outdoor heat exchanger 14 and the exhaust heat recovery heat exchanger 15 are connected in parallel in the refrigerant circuit 100. That is, during the heating operation, two heat exchangers for heating (evaporating) the refrigerant are arranged in parallel.

  In the normal heating operation, the first flow rate adjustment valve 18A and the second flow rate adjustment valve are set so that most of the refrigerant flowing out of the indoor heat exchanger 22 and flowing through the intermediate pipe 34 flows into the outdoor heat exchanger 14. An opening ratio with 18B is set. Therefore, in the case of normal heating operation, the refrigerant is heated mainly by exchanging heat with the outside air in the outdoor heat exchanger 14, and the heat exchanger 15 for exhaust heat recovery supplementarily heats the refrigerant. Used. Such a heating operation state in which the refrigerant is heated by heat exchange with the outside air mainly in the outdoor heat exchanger 14 is referred to as a normal heating operation mode.

  If the outside air temperature becomes extremely low during execution of the heating operation in the normal heating operation mode, the outdoor heat exchanger 14 cannot heat the refrigerant with the outside air, and conversely, the outdoor heat exchanger 14 A situation occurs in which the heat is taken away by the open air. In the present embodiment, in order to prevent such a situation from occurring, when the outside air temperature becomes extremely low, the flow of the refrigerant from the normal heating operation mode to the outdoor heat exchanger 14 is prohibited to exhaust heat. The operating state is switched to a low-temperature heating operation mode, which is a heating operation mode in which the refrigerant is heated only by the recovery heat exchanger 15.

  FIG. 2 is a flowchart showing a flow of an operation mode setting process routine executed by the control device 60 to set the operation state to either the normal heating operation mode or the low temperature heating operation mode during the heating operation. This routine is repeatedly executed during the heating operation. When the routine shown in FIG. 2 is started, the control device 60 first determines that the outside air temperature Ta detected by the outside air temperature sensor 68 is the threshold outside air temperature Ta0 in step (hereinafter abbreviated as S) 101 in FIG. It is determined whether or not: Here, the threshold outside temperature Ta0 is a threshold temperature at which the refrigerant cannot be sufficiently heated by the outdoor heat exchanger 14 during heating operation when the outside temperature Ta is equal to or lower than that temperature (in other words, the outside temperature Ta is When the temperature is higher than the temperature, the temperature is predetermined as a threshold temperature at which the refrigerant can be sufficiently heated by the outdoor heat exchanger 14 during the heating operation.

  When the outside air temperature Ta is higher than the threshold outside air temperature Ta0 (S101: No), the control device 60 advances the process to S103 and sets the operation state to the normal heating operation mode. Thereafter, the control device 60 ends this routine. When the operation state is set to the normal heating operation mode, the control device 60 executes the above-described normal heating operation.

  On the other hand, when the outside air temperature Ta is equal to or lower than the threshold outside air temperature Ta0 (S101: Yes), the control device 60 proceeds to S102 and sets the operation state to the low temperature heating operation mode. Thereafter, the control device 60 ends this routine.

  When the control device 60 executes the operation mode setting process described above, the operation state is changed from the normal heating operation mode when the outside air temperature Ta becomes equal to or lower than the threshold outside air temperature Ta0 during the heating operation in the normal heating operation mode. Switch to low temperature heating operation mode.

  Further, when the operation state is set to the low-temperature heating operation mode in the operation mode setting process, that is, when it is determined that the outside air temperature Ta is equal to or lower than the threshold outside air temperature Ta0, the control device 60 performs the low-temperature heating operation control process. Execute. FIG. 3 is a flowchart showing the flow of a low-temperature heating operation control routine executed by the control device 60. When this routine is started, the control device 60 first outputs a fully closed signal to the second flow rate adjusting valve 18B in S201 of FIG. 3 (second flow rate adjusting valve fully closed process). As a result, the second flow rate adjustment valve 18B is fully closed. When the second flow rate adjustment valve 18B is fully closed, the refrigerant flow into the outdoor heat exchanger 14 is prohibited.

  When the process of S201 is executed, the refrigerant that has been flowing to the outdoor heat exchanger 14 so far also flows into the heat exchanger 15 for exhaust heat recovery. In this way, when the flow rate of the refrigerant flowing through the exhaust heat recovery heat exchanger 15 increases at a stretch, heat exchange between the cooling water and the refrigerant in the exhaust heat recovery heat exchanger 15 is promoted, and accordingly, the cooling water temperature Decreases.

  A decrease in cooling water temperature induces various problems. For example, when the coolant temperature decreases, the temperature of engine oil for lubricating the engine 10 also decreases. Engine oil is usually used at a temperature within a predetermined use temperature range, and deterioration is accelerated when used at a temperature lower than the use temperature range. Therefore, when the cooling water temperature is too low, deterioration of the engine oil is promoted.

  Therefore, in the present embodiment, after the process of S201 is performed, the process proceeds to S202 so that the flow rate of the refrigerant flowing through the exhaust heat recovery heat exchanger 15 is not increased at a stroke due to the process of S201 and the cooling water temperature is not decreased more than necessary. Then, the opening degree of the first flow rate adjusting valve 18A is controlled. Specifically, in S202, the control device 60 opens the first flow rate adjustment valve 18A so that the cooling water temperature Tw detected by the cooling water temperature sensor 67 is maintained at a temperature equal to or higher than the lower limit cooling water temperature Tw0. Control the degree. For example, in S202, the control device 60 adjusts the first flow rate so that the cooling water temperature Tw matches the lower limit cooling water temperature Tw0 or a preset temperature that is slightly higher than the lower limit cooling water temperature Tw0. The opening degree of the valve 18A can be controlled. Here, the lower limit cooling water temperature Tw0 is a threshold temperature (when the cooling water temperature Tw is equal to or lower than the lower limit cooling water temperature Tw0), which may cause some trouble due to a decrease in the temperature of the cooling water (for example, promotion of deterioration of the engine oil described above). In other words, when the cooling water temperature Tw is higher than that temperature, the temperature is predetermined as a threshold temperature that does not cause any trouble due to a decrease in the temperature of the cooling water. The process of S202 corresponds to the first flow rate adjustment valve opening degree control process of the present invention.

  After executing the process of S202, the control device 60 advances the process to S203, and determines whether or not the current operation state is the low-temperature heating operation mode. When the current operation state is the low-temperature heating operation mode (S203: Yes), the process is returned to S201, and the above-described process is repeated. On the other hand, when the current operation state is not the low-temperature heating operation mode (S203: No), the control device 60 ends this routine.

  When the controller 60 executes the low-temperature heating operation process described above and controls the opening of the first flow rate adjustment valve 18A so that the cooling water temperature does not decrease more than necessary (below the lower limit cooling water temperature Tw0), Occurrence of defects due to water temperature drop is prevented. However, the process of S202 restricts the flow rate of the refrigerant flowing into the exhaust heat recovery heat exchanger 15 by restricting the first flow rate adjustment valve 18A in order to maintain the cooling water temperature at a temperature equal to or higher than the lower limit cooling water temperature Tw0. It is also a process to do. When the flow rate of the refrigerant flowing into the exhaust heat recovery heat exchanger 15 is limited, the flow rate of the refrigerant flowing out of the exhaust heat recovery heat exchanger 15 and sucked into the compressor 11 may be reduced. When the flow rate of the refrigerant sucked into the compressor 11 decreases, the flow rate may be lower than the flow rate of the refrigerant discharged from the compressor 11 according to the air conditioning load. In this case, there is a possibility that the refrigerant on the suction side of the compressor 11 runs short and the refrigerant suction pressure PL decreases. In particular, when the compressor 11 rotates at a high speed, the refrigerant suction pressure PL decreases.

  When the refrigerant suction pressure PL drops below a predetermined pressure, the control device 60 detects a low pressure abnormality, and the heating operation of the engine-driven air conditioner 1 is urgently stopped.

  Incidentally, as the flow rate of the refrigerant sucked into the compressor 11 decreases, the rotation speed of the compressor 11 is decreased so that the refrigerant having a flow rate corresponding to the flow rate is discharged from the compressor 11, thereby reducing the refrigerant suction pressure. It can be suppressed. However, on the other hand, the compressor 11 cannot be operated at the number of rotations commensurate with the air conditioning load, and as a result, the necessary heat exchange amount in the indoor heat exchanger 22 is insufficient. Then, there is a possibility that the temperature of the indoor air (outlet temperature) blown out from the outlet of the indoor heat exchanger 22 is lowered. That is, when the rotation speed of the compressor 11 is decreased along with the execution of the low-temperature heating operation control process, the rising performance of the heating capacity at the time of mode switching from the normal heating operation mode to the low-temperature heating operation mode is deteriorated.

  In the present embodiment, the control device 60 executes a low pressure avoidance process in order to suppress a decrease in the refrigerant suction pressure accompanying the execution of the low temperature heating operation control process. FIG. 4 is a flowchart showing a flow of a low pressure avoidance processing routine executed by the control device 60. This routine is repeatedly executed during the heating operation. When this routine is started, the control device 60 first determines in S301 of FIG. 3 whether or not the opening degree control of the first flow rate adjusting valve 18A is being executed in the low temperature heating operation control process. If this determination result is No, the control device 60 ends this routine. On the other hand, when the determination result of S301 is Yes, that is, when the opening degree control of the first flow rate adjustment valve 18A is being executed in the low-temperature heating operation control process, the control device 60 advances the process to S302.

  In S302, the control device 60 determines whether or not the refrigerant suction pressure PL detected by the suction pressure sensor 63 is equal to or lower than a first pressure PL1 that is predetermined as a pressure slightly higher than the lower limit pressure PL0. Here, the lower limit pressure PL0 is a threshold value of pressure (when the refrigerant suction pressure PL is equal to or lower than the lower limit pressure PL0, the control device 60 may detect a low pressure abnormality and the engine-driven air conditioner 1 may stop urgently) In other words, when the refrigerant suction pressure PL is higher than that pressure, it is predetermined as a threshold value of pressure at which there is no possibility of occurrence of low pressure abnormality.

  When it is determined in S302 that the refrigerant suction pressure PL is higher than the first pressure PL1 (S302: No), the control device 60 ends this routine. On the other hand, when it is determined in S302 that the refrigerant suction pressure PL is equal to or lower than the first pressure PL1 (S302: Yes), the control device 60 advances the process to S303.

  In S303, the control device 60 outputs an opening operation signal to the hot gas bypass on-off valve 18E. As a result, the hot gas bypass on-off valve 18E is opened. When the hot gas bypass on-off valve 18E is opened, a part of the high-temperature and high-pressure gas refrigerant that is discharged from the compressor 11 and flows through the discharge pipe 31 flows through the hot gas bypass pipe 38 to the accumulator inlet pipe 35, and further the accumulator. 17 to the intake pipe 36. Since the high-temperature and high-pressure gas refrigerant is supplied to the suction side of the compressor 11 in this way, the refrigerant suction pressure PL increases. The processing of S302 and S303 corresponds to the bypass valve control processing of the present invention.

  The hot gas bypass opening / closing valve 18E opened in the process of S303 closes when the refrigerant suction pressure PL rises to a pressure set value higher than the first pressure PL1, for example, PL1 + 0.5 MPa. May control the hot gas bypass on-off valve 18E. Further, the hot gas bypass opening / closing valve 18E may be controlled by the valve opening time. In this case, for example, as shown in FIG. 4, the control device 60 outputs an open operation signal to the hot gas bypass on / off valve 18E in S303, then proceeds to S304, and performs hot gas bypass on / off by executing the processing of S303. It is determined whether or not the valve opening time t of the valve 18E has reached a predetermined time t0. When the valve opening time t has not reached the predetermined time t0 (S304: No), it waits until the valve opening time t reaches the predetermined time t0. When the valve opening time t has reached the predetermined time t0 (S304: Yes), the control device 60 advances the process to S305 and outputs a closing operation signal to the hot gas bypass on-off valve 18E. As a result, the hot gas bypass on-off valve 18E is closed. Thereafter, the control device 60 returns the process to S301 and repeats the above-described process.

  As a result of the execution of the low pressure avoidance control process described above, the hot gas bypass on / off valve 18E is discharged from the compressor 11 in order to open for a predetermined time t0 when the refrigerant suction pressure PL is lowered to the first pressure PL1 or less. A high-temperature and high-pressure gas refrigerant is supplied to the suction side of the compressor 11. For this reason, the refrigerant suction pressure PL increases. As a result, the refrigerant suction pressure PL can be maintained at a pressure equal to or higher than the lower limit pressure PL0 lower than the first pressure PL1. Therefore, it is possible to suppress a decrease in the refrigerant suction pressure PL when performing the heating operation in the low-temperature heating operation mode, and thus it is possible to prevent the occurrence of problems due to the decrease in the refrigerant suction pressure PL.

  Further, since the lowering of the refrigerant suction pressure PL is suppressed by the execution of the low pressure avoidance control process, the compression according to the air conditioning load is performed without reducing the rotation speed of the compressor 11 during the heating operation in the low temperature heating operation mode. The machine 11 can be activated. Therefore, a sufficient amount of refrigerant can be supplied to the indoor heat exchanger 22, and a necessary heat exchange amount in the indoor heat exchanger 22 can be ensured. As a result, it is possible to prevent a decrease in the outlet temperature of the indoor heat exchanger 22 when the operation state is switched from the normal heating operation mode to the low temperature heating operation mode. That is, it is possible to suppress the deterioration of the rising performance of the heating capacity when the operation state is switched from the normal heating operation mode to the low temperature heating operation mode.

  Furthermore, since the hot gas bypass opening / closing valve 18E is opened in the low pressure avoidance control process, the high-temperature refrigerant gas is supplied to the suction pipe 36, so that the temperature of the refrigerant sucked into the compressor 11 can be increased. For this reason, it is possible to suppress the temperature drop of the refrigerant sucked into the compressor 11, thereby causing a problem due to the temperature drop of the refrigerant sucked into the compressor 11 (for example, liquid refrigerant sucked into the compressor 11. This can prevent the occurrence of liquid compression of the compressor 11).

  In the low pressure avoidance control process described above, the decrease in the refrigerant suction pressure PL is suppressed by opening the hot gas bypass opening / closing valve 18E. However, if the opening time of the hot gas bypass opening / closing valve 18E is too long, the air conditioning Ability is reduced. Therefore, the opening time of the hot gas bypass opening / closing valve 18E should be as short as possible within a range in which the refrigerant suction pressure PL is maintained at a pressure equal to or higher than the lower limit pressure PL0 and deterioration of rising performance at the time of mode switching can be suppressed. good.

(Modification)
A modified example of the low pressure avoidance control process will be described. FIG. 5 is a flowchart showing the flow of the low-pressure avoidance control process according to the modification. When this routine is started, the control device 60 first determines in S401 of FIG. 3 whether or not the opening degree control of the first flow rate adjustment valve 18A is being executed in the low temperature heating operation control process. If this determination result is No, the control device 60 ends this routine. On the other hand, when the determination result in S401 is Yes, that is, when the opening degree control of the first flow rate adjustment valve 18A is being executed in the low-temperature heating operation control process, the control device 60 advances the process to S402.

  In S402, the control device 60 executes an opening degree control process for the third flow rate adjustment valve 18C. In this case, the control device 60 adjusts the opening of the third flow rate adjustment valve 18C so that the refrigerant suction pressure PL detected by the suction pressure sensor 63 is maintained at a pressure equal to or higher than the lower limit pressure PL0.

  When the opening degree of the third flow rate adjusting valve 18C increases, the flow rate of the refrigerant flowing from the intermediate pipe 34 to the subcooling pipe 39 via the fourth refrigerant pipe 37 increases. The supercooling pipe 39 is connected to the suction pipe 36 via the accumulator inlet pipe 35 and the accumulator 17. Therefore, when the flow rate of the refrigerant flowing into the supercooling pipe 39 increases, the flow rate of the refrigerant supplied to the suction pipe 36 also increases, and thereby the refrigerant suction pressure PL increases. In this way, the refrigerant suction pressure PL can be controlled by controlling the opening degree of the third flow rate adjusting valve 18C.

  In this case, for example, in S402, the control device 60 controls the third flow rate adjustment valve 18C so that the refrigerant suction pressure PL matches the first pressure PL1 that is predetermined as a pressure slightly higher than the lower limit pressure PL0. The opening degree can be controlled. Alternatively, when the refrigerant suction pressure PL detected by the suction pressure sensor 63 is equal to or lower than the first pressure PL1, the control device 60 changes the opening of the third flow rate adjustment valve 18C by a predetermined opening from the current opening. The opening degree of the third flow rate adjusting valve 18C can be controlled so as to increase. The process of S402 corresponds to the bypass valve control process of the present invention.

  After executing the process of S402, the control device 60 returns the process to S401 and repeats the above process.

  By executing the low pressure avoidance control process described above, the opening of the third flow rate adjustment valve 18C is controlled so that the refrigerant suction pressure PL is maintained at a pressure equal to or higher than the lower limit pressure PL0. For this reason, it is possible to prevent a decrease in the refrigerant suction pressure PL, and in turn, it is possible to prevent a malfunction due to a decrease in the refrigerant suction pressure PL.

  As described above, when the controller 60 included in the engine-driven air conditioner 1 according to the embodiment of the present invention and the modification thereof determines that the outside air temperature Ta is equal to or less than the threshold outside air temperature Ta0 during the heating operation. The operation state is set to the low-temperature heating operation mode. In addition, the control device 60 performs a second flow rate adjustment valve full-close process S201 for controlling the second flow rate adjustment valve 18B so that the second flow rate adjustment valve 18B is fully closed when the operation state is set to the low-temperature heating mode. After the second flow rate adjustment valve fully closing process S201, the opening degree of the first flow rate adjustment valve 18A is maintained so that the temperature Tw of the coolant flowing through the coolant circuit 50 is maintained at a temperature equal to or higher than the lower limit coolant temperature Tw0. During the execution of the first flow rate adjustment valve opening degree control process S202 for controlling the flow rate and the first flow rate adjustment valve opening degree control process, the bypass piping (in order to maintain the refrigerant suction pressure PL at a pressure equal to or higher than the lower limit pressure PL0) Bypass valve control processing (S302, S303, S402) for controlling bypass valves (hot gas bypass on / off valve 18E, third flow rate adjusting valve 18C) interposed in hot gas bypass pipe 38 and supercooling pipe 39) And, to run.

  According to the above-described embodiment and its modification, the control device 60 controls the bypass valve as described above when in the low-temperature heating operation mode, so that the refrigerant suction pressure PL at the time of performing the heating operation in the low-temperature heating operation mode. Can be suppressed.

  As mentioned above, although embodiment and the modification of this invention were described, this invention should not be limited to the said embodiment and modification. For example, in the embodiment and the modified example, the hot gas bypass on / off valve 18E or the third flow rate adjustment valve 18C is controlled in order to suppress the decrease in the refrigerant suction pressure PL when the heating operation is performed in the low temperature heating operation mode. showed that. However, the control target valves for suppressing the decrease in the refrigerant suction pressure PL are not limited to these valves (hot gas bypass on-off valve 18E and third flow rate adjusting valve 18C). For example, in FIG. 1, an accumulator / four-way valve bypass pipe 40 includes a first refrigerant pipe (indoor unit side pipe 32) and a third refrigerant pipe (suction pipe 36) so as to bypass the outdoor heat exchanger 14 during heating operation. And connected. Therefore, by controlling the accumulator / four-way valve bypass opening / closing valve 18F interposed in the accumulator / four-way valve bypass pipe 40, a decrease in the refrigerant suction pressure PL during the heating operation in the low-temperature heating operation mode is suppressed. be able to. In the above embodiment, the example in which the hot gas bypass on / off valve 18E is controlled to be opened / closed in the low pressure avoidance control process to suppress the decrease in the refrigerant suction pressure PL has been described. May be configured to suppress a decrease in the refrigerant suction pressure PL. Thus, the present invention can be modified without departing from the gist thereof.

DESCRIPTION OF SYMBOLS 1 ... Engine-driven air conditioner, 10 ... Engine, 11 ... Compressor, 11a ... Inlet, 11b ... Discharge port, 13 ... Four-way valve, 14 ... Outdoor heat exchanger, 15 ... Heat exchanger for exhaust heat recovery, 16 ... Supercooling heat exchanger, 17 ... Accumulator, 18A ... First flow rate adjustment valve, 18B ... Second flow rate adjustment valve, 18C ... Third flow rate adjustment valve (bypass valve), 18E ... Hot gas bypass on-off valve (bypass valve) ), 18F: Accumulator / four-way valve bypass opening / closing valve, 21 ... Indoor side electronic expansion valve, 22 ... Indoor heat exchanger, 31 ... Discharge pipe (first refrigerant pipe), 32 ... Indoor unit side pipe (first refrigerant pipe) 33 ... Outdoor unit side pipe (third refrigerant pipe), 34 ... Intermediate pipe (second refrigerant pipe), 35 ... Accumulator inlet pipe (third refrigerant pipe), 36 ... Suction pipe (third refrigerant pipe), 37 ... Fourth refrigerant pipe, 38 ... Gas bypass piping (bypass piping), 39 ... Supercooling piping (bypass piping), 40 ... Accumulator / four-way valve bypass piping, 50 ... Cooling water circuit, 60 ... Control device, 63 ... Suction pressure sensor, 67 ... Cooling water temperature Sensor: 68 ... Outside air temperature sensor, 100 ... Refrigerant circuit, PL ... Refrigerant suction pressure, PL0 ... Lower limit pressure, PL1 ... First pressure, Ta ... Outside air temperature, Ta0 ... Threshold outside air temperature, Tw ... Cooling water temperature, Tw0 ... Lower limit Cooling water temperature, S201 ... second flow rate adjustment valve full closing process, S202 ... first flow rate adjustment valve opening control process, S302, S303, S402 ... bypass valve control process,

Claims (3)

An engine that generates driving force;
A cooling water circuit through which cooling water for cooling the engine flows;
It has a suction port for sucking refrigerant and a discharge port for discharging refrigerant, and is operated by the driving force of the engine to suck the refrigerant from the suction port, compress the sucked refrigerant, and discharge the compressed refrigerant to the discharge port. A compressor discharging from the outlet;
An indoor heat exchanger connected to the discharge port of the compressor via a first refrigerant pipe and exchanging heat between the refrigerant flowing in from the first refrigerant pipe and room air during heating operation;
A refrigerant and outside air that are connected to the indoor heat exchanger via a second refrigerant pipe and connected to the suction port of the compressor via a third refrigerant pipe, and flown from the second refrigerant pipe during heating operation. An outdoor heat exchanger that exchanges heat;
A fourth refrigerant pipe connecting the second refrigerant pipe and the third refrigerant pipe;
A heat exchanger for exhaust heat recovery which is interposed in the fourth refrigerant pipe and exchanges heat between the refrigerant flowing through the fourth refrigerant pipe and the cooling water flowing through the cooling water circuit;
A first flow rate adjustment valve that is interposed in the fourth refrigerant pipe and that can adjust the flow rate of the refrigerant flowing to the exhaust heat recovery heat exchanger during heating operation;
A second flow rate adjustment valve interposed in the second refrigerant pipe and capable of adjusting the flow rate of the refrigerant flowing from the second refrigerant pipe into the outdoor heat exchanger during heating operation;
A bypass pipe connecting the first refrigerant pipe or the second refrigerant pipe and the third refrigerant pipe so as to bypass the outdoor heat exchanger during heating operation;
A bypass valve interposed in the bypass pipe;
A control device for controlling the first flow rate adjusting valve, the second flow rate adjusting valve, and the bypass valve;
An engine-driven air conditioner comprising:
In the heating operation, the control device has determined that the outside air temperature is equal to or lower than a predetermined threshold outside air temperature as an outside temperature at which the refrigerant cannot be sufficiently heated by the outdoor heat exchanger when the outside air temperature is equal to or lower than the temperature. A second flow rate adjustment valve full closing process for controlling the second flow rate adjustment valve so that the second flow rate adjustment valve is fully closed;
The opening degree of the first flow rate adjustment valve is maintained so that the temperature of the cooling water flowing through the cooling water circuit is maintained at a temperature equal to or higher than a predetermined lower limit cooling water temperature after the second flow rate adjustment valve full closing process is performed. A first flow rate adjusting valve opening control process for controlling
Bypass valve control for controlling the bypass valve so that the pressure of the refrigerant sucked into the compressor is maintained at a pressure equal to or higher than a predetermined lower limit pressure during execution of the first flow rate adjustment valve opening degree control process. Process and execute,
Engine-driven air conditioner. The engine-driven air conditioner according to claim 1,
The bypass pipe is a hot gas bypass pipe connecting the first refrigerant pipe and the third refrigerant pipe;
The bypass valve is a hot gas bypass opening / closing valve interposed in the hot gas bypass pipe,
The control device controls the opening and closing of the hot gas bypass valve so that the pressure of the refrigerant sucked into the compressor is maintained at a pressure equal to or higher than the lower limit pressure in the bypass valve control process. Air conditioner. The engine-driven air conditioner according to claim 1,
The bypass pipe is a supercooling pipe that connects the second refrigerant pipe and the third refrigerant pipe;
The bypass valve is a third flow rate adjustment valve interposed in the supercooling pipe,
In the middle of the supercooling pipe, a supercooling heat exchanger for exchanging heat between the refrigerant flowing through the second refrigerant pipe and the refrigerant flowing through the supercooling pipe is interposed,
The control device controls the opening of the third flow rate adjustment valve so that the pressure of the refrigerant sucked into the compressor is maintained at a pressure equal to or higher than the lower limit pressure in the bypass valve control process. Engine-driven air conditioner.

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