JPH03251661A - Heat pump system - Google Patents

Abstract

PURPOSE:To know a change in a high pressure more accurately by a construction wherein a heat exchanging element which can exchange heat with a suction-side gas pipe is provided nearer to the discharge-side gas pipe side than to a first restrictor in a first bypass pipe and a means for detecting the temperature of a liquefied refrigerant through the heat exchanging element is provided. CONSTITUTION:A refrigerant circulating circuit is constructed by connecting discharge- side gas pipes 6 and 25, a condensor 31, a high-pressure-side liquid pipe 17, an expansion mechanism 14, a low-pressure-side liquid pipe 13, an evaporator 11 and suction-side gas pipes 10 and 8 to a compressor 1 sequentially from the discharge side thereof. A means 74 for controlling the operation so that a refrigerant discharged from the compressor 1 be made to circulate from the condenser 31 side onto the evaporator 11 side, is provided. Moreover, the discharge-side gas pipes 6 and 25 and the low- pressure-side liquid pipe 13 are connected with each other, while a first bypass pipe 41 with a first restrictor 43 interposed is provided. In this first bypass pipe 41, a heat exchanging element 42 which can exchange heat with the suction-side gas pipes 10 and 8 is provided nearer to the discharge-side gas pipes 6 and 25 side than to the first restrictor 43, and the temperature of the refrigerant therein is detected by a detecting means 45.

Description

[Detailed description of the invention] (Industrial application field) This invention relates to a heat pump system.

(Prior Art) As a conventional example of a heat pump system, there can be mentioned, for example, a device described in Japanese Patent Application Laid-Open No. 63-32256. This device is configured as a multi-type air conditioner, with an outdoor unit containing an inverter-controlled compressor and an outdoor heat exchanger, and a plurality of indoor units, each with an indoor heat exchanger, connected in parallel to each other. The operation of the compressor is controlled with the compression capacity according to the change in the total of each air conditioning load given by the temperature difference between each detected room temperature and the set room temperature.

Then, the high-pressure side pressure, that is, the pressure corresponding to the condensation temperature in the indoor heat exchanger during heating, is detected by a temperature sensor installed in the middle part of the indoor heat exchanger, and the detected temperature reaches the allowable upper limit. If an abnormal increase in high pressure occurs, it is assumed that an abnormal increase in high pressure has occurred, and the control according to the air conditioning load change described above is interrupted and control is shifted to reduce the compression capacity of the compressor, thereby reducing the increase in high pressure. It is designed to suppress the

In addition, a temperature sensor is further installed at the outlet of the indoor heat exchanger so that the temperature difference between the intermediate temperature sensor and this temperature sensor is approximately constant, that is, the degree of supercooling of the condensed refrigerant is approximately constant. The opening degree of the electric expansion valve is controlled to ensure that.

(Problem to be solved by the invention) By the way, in the multi-type air conditioner as described above,
If the connecting piping connecting the indoor unit to the outdoor unit is long, the high pressure at the discharge part of the compressor will be higher than the condensing pressure at the indoor heat exchanger due to the pressure loss when flowing through this connecting piping. . In this way, the temperature sensor installed in a conventional indoor heat exchanger cannot accurately grasp the high pressure. This has caused problems such as malfunctions due to operating conditions that exceed these limits.

Furthermore, the inability to accurately grasp the condensing pressure as described above causes an inability to obtain an appropriate degree of supercooling when performing supercooling control.

This invention has been made in view of the above, and its purpose is to be able to more accurately detect changes in high pressure, and based on this detection result, to reliably prevent abnormal increases in high pressure. The purpose of the present invention is to provide a heat pump system that can perform accurate supercooling control.

(Means for Solving the Problem) Therefore, as shown in FIG. 1, in the heat pump system according to the first aspect, the compressor 1 has a discharge side gas pipe 6, 25, a condenser 31, the high pressure side liquid pipe 17, the expansion mechanism 14, the low pressure side liquid pipe 13, the evaporator 1l, and the suction side gas pipes 10 and 8 are connected to form a refrigerant circulation circuit, and the evaporator 11 is connected from the condenser 31 side to the evaporator 11. This heat pump system is provided with an operation control means 74 for controlling the operation so as to circulate the refrigerant discharged from the compressor l to the side, and the discharge side gas pipes 6 and 25 and the low pressure side liquid pipe 13 are connected to each other. The first aperture 43 is connected to the
A bypass pipe 4l is provided, and this first bypass pipe 41 includes:
Furthermore, a heat exchange part 42 capable of exchanging heat with the suction side gas pipes 10 and 8 is provided on the discharge side gas pipes 6 and 25 side of the first throttle 43, and a refrigerant that liquefies through this heat exchange part 42. A condensing temperature detection means 45 for detecting temperature is provided.

Further, in the heat pump system according to the second claim, in the heat pump system according to the first claim, the compressor 1 is constituted by a compressor with a variable compression capacity, and the temperature detected by the condensing temperature detecting means 45 is the first. A high pressure monitoring control means 85 is provided which issues a command to reduce the compression capacity of the compressor 1 to the operation control means 74 when the pressure exceeds one reference value.

Furthermore, the heat pump system according to the third aspect is the heat pump system according to the first or second aspect, in which the discharge side gas pipe 6. 25 and the suction side gas pipe 10.8, and controls the high pressure control valve 56 to open when the temperature detected by the condensing temperature detection means 45 exceeds the second reference value. Valve control means 86 is provided.

Furthermore, the liquid pump system according to claim 4 comprises:
As shown in FIG. 4, the expansion mechanism 14 includes an electric expansion valve 18, an intermediate temperature sensor 69 for detecting the intermediate temperature of the condenser 31, and an outlet temperature sensor 70 for detecting the outlet temperature of the condenser 31. and a supercooling degree control means 87 for controlling the opening degree of the electric expansion valve 18 in order to maintain the degree of supercooling of the condensed refrigerant substantially constant based on the temperatures detected by the temperature sensors 69 and 70. Further, an opening degree correcting means 88 is provided for controlling the opening degree of the electric expansion valve 18 in order to reduce the temperature difference between the temperatures detected by the intermediate temperature sensor 69 and the condensing temperature detecting means 45.

(Function) In the heat pump system according to the first aspect, a part of the gas refrigerant discharged from the compressor 1 bypasses through the first bypass pipe 41. At this time, in the heat exchange section 42, heat is radiated to the low-temperature evaporated gas refrigerant flowing back from the evaporator 11 to the compressor 1 through the suction side gas pipe 10.8, and the refrigerant is condensed.

In this way, for example, in a separate air conditioner or the like in which an outdoor unit containing the compressor 1 and the evaporator 11 and an indoor unit containing the condenser 31 are configured separately, the compressor 1 inside the outdoor unit, that is, the compressor 1 Since it is possible to detect the temperature of the condensed refrigerant in the vicinity of the refrigerant, the influence of pressure loss etc. in the connecting piping, which has conventionally occurred, is eliminated, and the high pressure can be grasped more accurately.

Then, when the detection 1 by the condensing temperature detection means 45 exceeds the reference temperature, control is performed to reduce the compression capacity of the compressor l whose compression capacity is variable, as in the heat pump system according to the second aspect, for example. According to the heat pump system according to claim 3, the discharge side gas pipe 6.25 is in a high pressure state and the suction side gas pipe 1 is in a low pressure state.
By controlling the opening of the high pressure control valve 56 that communicates with 0.8, it is possible to more reliably prevent abnormal increases in the respective high pressures.

Further, in the heat pump system according to the fourth aspect, since the high pressure is accurately grasped as described above and the opening degree of the electric expansion valve 18 is controlled so as to bring the intermediate temperature of the condenser 31 close to the above value, it is possible to More accurate supercooling control can be performed.

(Example) Next, a specific example of the heat pump system of the present invention will be described in detail with reference to the drawings.

FIG. 2 shows a refrigerant circuit diagram of an air conditioner according to an embodiment of the present invention. In the figure, X is an outdoor unit, and this outdoor unit X includes first to third indoor Units 1-A-C and 4th through expansion unit Y
A total of six indoor units, including the sixth indoor units D to F, are connected.

The above outdoor unit) X has a compressor l installed inside,
This compressor 1 is of a so-called twin-verter type, in which a first compressor 2 whose rotation speed is variable by inverter control and a second compressor 3 whose rotation speed is constant are connected in parallel and housed in a housing. It is a compressor, and the first and second compressors 2.3
The suction sides of are respectively connected to each other via a first accumulator 4.5. The discharge pipe 6 of the compressor 1 and the suction pipe 8 in which the second accumulation tank is interposed are each connected to a four-way switching valve 9, and one switching port of the four-way switching valve 9 is connected to the Sequentially, the first gas pipe 10,
The outdoor heat exchanger 11, the first liquid pipe 13 in which the dryer filter 12 is interposed, the first electric expansion valve 14, the liquid receiver 15, and the second liquid pipe 17 in which the first closing valve 16 is interposed are connected in sequence. has been done. The tip side of the second liquid pipe 17 is provided with a second electric expansion valve 18...18, and first to fourth liquid branch pipes connected to the source side communication pipe connection port 19...19. It is branched into 20-23. - On the other hand, a second gas pipe 25 in which a second closing valve 24 is interposed is connected to the other switching port of the four-way switching valve 9.
The tip side of 5 is a gas side communication piping connection port 26, respectively.
...26 are branched into first to fourth gas branch pipes 27 to 30.

In this way, each of the four liquid branch pipes 20 to 23 and the gas branch pipes 27 to
Although it is possible to connect four indoor units to the outdoor unit X provided with 30, in the above embodiment,
Each indoor heat exchanger 31 of the first to third indoor units A to C is installed between the three sets of liquid branch pipes 20 to 22 and gas branch pipes 27 to 29.
31 (only the first indoor unit A is shown), and an expansion unit Y is connected to the fourth liquid branch pipe 23 and the fourth gas branch pipe 30 instead of the indoor unit.

The second expansion unit Y connects the other end of the expansion liquid pipe 32, one end of which is connected to the fourth liquid branch pipe 23, to three expansion liquid branch pipes each having a third electric expansion valve 33, 33 interposed therein. 34・
34, and the other end of the expansion gas pipe 35, one end of which is connected to the fourth gas branch pipe 30, is a gas side expansion pipe that branches into three expansion gas branch pipes 36. It consists of And each of the above-mentioned expansion liquid branch pipes 34 and 3
4 and the expansion gas branch pipes 36, 36, each of the indoor heat exchangers 31, 31 (4th to 6th indoor units) D-F
(only indoor unit D is shown) are connected to each other.

Further, in the above device, a first bypass pipe 41 for high pressure saturation temperature detection is provided which interconnects the second gas pipe 25 and the first liquid pipe 13.
By arranging the pipe wall along the first gas pipe 10 in the middle part, it is possible to exchange heat between the refrigerant flowing through the first gas pipe 10 and the first bypass pipe 41, respectively. A heat exchange section 42 is provided. A first restrictor 43 made of a capillary tube is sequentially provided on the first liquid pipe 13 side of the heat exchange section 42, and a refrigerant flow is allowed in the direction from the second gas pipe 25 side toward the first liquid pipe 13 side. A first check valve 44 is interposed, and a condensing temperature detection device is provided on the pipe wall between the heat exchange section 42 and the first throttle 43, and includes a thermistor or the like for detecting the temperature of the refrigerant flowing inside. A sensor (condensation temperature detection means) 45 is attached.

In the above configuration, the second ′ interposed in the fourth liquid branch pipe 23 is connected to the dynamic expansion valve 18 and the expansion liquid branch pipes 34 and 34.
With the third electric expansion valves 33 and 33 interposed in the piping, a piping section with both ends closed when the operation is stopped is created, and when performing vacuum drying during installation or pump down operation during maintenance,
Signal operations are required to open each of the electric expansion valves, making the work complicated. Therefore, the piping of the source side connection piping connection boat 19 is connected to the first bypass pipe 41 from the second electric expansion valve 18 in the fourth liquid branch pipe 23.
A second bypass pipe 4 in which a third closing valve 46 and a second throttle 47 are interposed in a piping section between the throttle 43 and the first check valve 44.
Connected by 8.

As a result, a vacuum pump is connected to the vacuum port of the third closing valve 46 to perform vacuum drying of the both end closed portions, and
The refrigerant sealed during this time can be recovered to the outdoor heat exchanger 11 side through the second bypass pipe 48 and the first bypass pipe 41 by opening the third closing valve 46 .

Further, an oil separator 51, a second check valve 52, and a first on-off valve 53 are sequentially provided in the discharge pipe 6 from the compressor 1 side. Further, a third bypass pipe 54 is further provided which is branched from the discharge pipe 6 and connected to the first liquid pipe 13, and a second on-off valve 55 interposed in the third bypass pipe 54 is opened. By directly supplying the discharged gas refrigerant from the compressor 1 to the outdoor heat exchanger 11 through the third bypass pipe 54, the outdoor heat exchanger 11
It is designed to perform a defrosting operation to remove frost that has formed during the winter.

Further, the discharge pipe 6 and the suction pipe 8 are connected to a high pressure control valve 56
and a third throttle 57 are interconnected by a fourth bypass pipe (bypass pipe for preventing abnormal pressure rise) 58, and when the high pressure control valve 56 is opened, the discharge pipe 6 and the suction pipe 8 are connected to each other. By communicating through the fourth bypass pipe 58, abnormal rise in high pressure during operation is prevented. In addition, the oil separator 51 allows the refrigerating machine oil separated therein to flow back to the compressor 1.
It is connected to the suction pipe 8 by a fifth bypass pipe 60 in which a fourth throttle 59 is interposed.

Also, a sixth bypass pipe 61 that allows a part of the liquid refrigerant in the liquid receiver 15 to flow back directly to the second accumulator 7
is provided, and the temperature of the refrigerant evaporated through the fifth throttle 62 provided in the sixth bypass pipe 61 is detected by the evaporation temperature detection sensor 63 as the saturation temperature corresponding to the evaporation pressure.

Further, a third on-off valve 65,65 is interposed in the fourth gas branch pipe 30 in parallel with a third check valve 64 that allows refrigerant flow in the refrigerant circulation direction during cooling operation, which will be described later. This is provided assuming that one large indoor unit is connected between the fourth gas branch pipe 30 and the fourth liquid branch pipe 23 instead of the expansion unit Y. At this time, heating operation is performed on the A-C side of the first to third indoor units, and when the heating is stopped in the large indoor unit, the amount of circulating refrigerant is reduced by suppressing the increase in the amount of liquid accumulated in the large indoor unit. In order to prevent the decrease, control is performed to close the third on-off valve 65. In the figure, 66...66 are mufflers 67 respectively interposed in the gas branch pipes 27 to 30, the expansion gas branch pipes 36 and 36, and the fourth bypass pipe 58.
...67 is the gas branch pipe 27 to 30, the expansion gas branch pipe 36
・36 indicates a superheat degree detection sensor attached to the cooling mode, and 6B indicates a heating superheat degree detection sensor attached to the suction pipe 8.

In the air conditioner with the above configuration, first, cooling operation is performed by placing the four-way switching valve 9 in the switching position shown by the broken line in the figure, opening the first on-off valve 53, and closing the second and third on-off valves 55 and 65. This is done by operating the compressor 1 at a low temperature. At this time, the refrigerant discharged from the compressor 1 is transferred to the discharge pipe 6, the four-way switching valve 9, and the first
It flows into the outdoor heat exchanger 11 through the gas pipe 10, and after being condensed in the outdoor heat exchanger 11, it passes through the first liquid pipe 13, the second liquid pipe 17, and then flows into each liquid branch pipe 20 to 23 and the expansion liquid branch pipe. 34.3
4, and circulates to each indoor heat exchanger 31...31. After evaporating in these indoor heat exchangers 31...31, the expansion gas branch pipes 36, 36 and the gas branch pipe 2
7 to 30, the gases merge, and are returned to the compressor 1 through the second gas pipe 25, the four-way switching valve 9, and the suction pipe 8. In this case, the cooling superheat degree detection sensor 67
The temperature difference (degree of superheat) between the refrigerant temperature after evaporation in each indoor unit) A-F detected by 67 and the evaporation pressure equivalent saturation temperature detected by evaporation temperature detection sensor 63 is set as the reference degree of superheat. The opening degree of each of the second and third electric expansion valves 18.33 is controlled so as to do so. Note that the first electric expansion valve 14 is kept fully open, and the second and third electric expansion valves 18 and 33 corresponding to the indoor units in the cooling-off room are kept fully open.

On the other hand, the heating operation is performed by placing the four-way switching valve 9 in the switching position shown by the solid line in the figure as described above, opening the third on-off valve 65, and operating the compressor 1. As a result, the refrigerant discharged from the compressor 1 passes through the discharge side gas pipe of the discharge pipe 6 and the second gas pipe 25, and then is divided into the gas branch pipes 27 to 30 and the expansion gas branch pipes 36 and 36 to generate heat in each room. exchanger 3
1..31, and after being condensed in each indoor heat exchanger 31..31 which functions as a condenser, it passes through each expansion liquid branch pipe 34, 34 and liquid branch pipes 20 to 23, and then merges. , second liquid pipe (high pressure side liquid pipe) 17, first electric expansion valve (
via the expansion mechanism) 14, the first liquid pipe (low pressure side liquid pipe) 13,
It flows into the outdoor heat exchanger 11 which functions as an evaporator. After being evaporated in this outdoor heat exchanger 11, it is returned to the compressor 1 through the first gas pipe 10 and the suction side gas pipe of the suction pipe 8. In this case, the first
The electric expansion valve 14 controls the degree of superheating of the circulating refrigerant. Further, the opening degree of each second and third electric expansion valve 18.33 is controlled so that the degree of subcooling of the refrigerant condensed after passing through each indoor heat exchanger 31 is approximately constant. This point will be discussed later. In addition, the second one corresponds to the room where heating is stopped.
, the third electric expansion valve 18.33 is set to a predetermined stop opening degree (an opening degree that allows a small amount of refrigerant to flow in proportion to natural heat radiation).
to be maintained.

During such heating operation, a part of the refrigerant discharged from the compressor 1 bypasses from the second gas pipe 25 to the first liquid pipe 13 through the first bypass pipe 41. At this time, a low-temperature gas refrigerant evaporated in the outdoor heat exchanger 11 is flowing through the first gas pipe 10, and therefore, the refrigerant flowing through the first bypass pipe 41 is
It is condensed by heat exchange with the low temperature gas refrigerant flowing through the first gas pipe 10. This condensation temperature is detected by the condensation temperature detection sensor 45, and the operation of the compressor 1 is controlled while monitoring this detected temperature change. This will be explained with reference to the operation control system diagram.

As shown in the figure, each of the indoor units A to F is each equipped with an indoor control device f71 (only indoor units A and D are shown), and each indoor control device 71 includes a remote control 72 for operation operation and A room temperature sensor 73 for detecting room temperature is connected to each of them. Each of the operation remote controllers 72 has an operation switch and a temperature setting switch for setting a desired room temperature, and when the operation switch is ON and the room temperature detected by the room temperature sensor 73 reaches the set temperature. (when indoor thermostat is ON),
The operation request signal, the temperature difference signal ΔT between the detected room temperature and the set temperature, and the S value corresponding to the rated capacity of the indoor heat exchanger 31 in each indoor unit) A to F (for example, the rated capacity is 22
40kca I/h is “1” 2800kca
l/h is "1.25", 3550kcal/h is "1.5", 4500kcal/h is "2"...
) is output from each indoor control device 71.

The signals output from each indoor control device 71 of the first to third indoor units) A to C are directly input to the outdoor control device (operation control means) 74 provided in the outdoor unit The signals output from each indoor control device 71 of the 6th to 6th indoor units D-F connected to the outdoor unit X via the unit Y are
The information is input to an expansion control device 75 provided in the interior. In the intermediate signal processing section 76 within this expansion control device 75,
The integrated value 5to of each S value from the indoor unit that is emitting the operation request signal among the fourth to sixth indoor units D-F
tal and the cumulative temperature difference ΔTtota between each temperature difference signal ΔT
l are calculated, and these 5total and ΔTtotal are transmitted to the outdoor control device 74 together with the operation request signal.

On the other hand, the outdoor control bag W74 and the first
Inverter control device 7 for frequency controlling the compressor 2
7. In the outdoor control device 74, an operation request unit grasping section 78, a valve control section 79, and a compressor operation control section 80 are provided. At the same time, an operation unit signal corresponding to the indoor unit outputting the operation request signal is output to the valve control section 79 and the compressor operation control section 80. As a result, the valve control section 79 first controls the switching operation of the four-way switching valve 9 during the heating operation described above, and the first switching operation.
, the opening degree of the second electric expansion valve 14.18 is controlled. Further, the opening degree of the third electric expansion valve 33 is controlled by the expansion control device 7.
This is performed by the expansion valve control section 81 in 5.

On the other hand, the compressor operation control section 80 first sets the initial operating frequency when there is a change in the operating unit signal, that is, when there is a change in the number of operating indoor units. This is done by calculating the value ΣS, which is the sum of the S value and 5total from each indoor control device 71 and expansion control device 75 that have operation requests, and the total temperature difference ΣΔT, which is the sum of ΔT and ΔTtotal, and then calculating these ΣS and The initial frequency corresponding to the combination with ΣΔT is set as the initial operating frequency. For this purpose, the compressor operation control section 80 stores in advance appropriate operating frequencies for various combinations of ΣS and ΣΔT. Then, the compressor 1 starts operating with a compression capacity corresponding to this initial operating frequency. After reaching the operating state corresponding to the above initial operating frequency, the operating frequency is sequentially changed so that ΣΔT becomes 0 by P control and ■ @ control according to subsequent changes in ΣΔT, and the compressor Continue operation in step 1. During this control, if a change occurs in the number of operating indoor units, a new control is performed from the setting of the initial operating frequency.

It should be noted that the operation of the compressor 1 is performed at the operating frequency of the first compressor 2.
When the frequency is within the upper limit driving frequency (for example, 105 Hz), only this first compressor 2 is operated independently, and when the upper limit driving frequency is exceeded, the second compressor 3 is operated and the operating frequency is By outputting the difference ΔF obtained by subtracting the frequency (for example, commercial frequency 60 tz) corresponding to the compression capacity of the second compressor 3 to the inverter control device 77, the difference between the first compressor 2 and the second compressor 3 is Perform simultaneous operation.

The compressor 1 is operated by load response control according to the indoor air conditioning load as described above, while monitoring whether the high pressure side pressure is within the normal range. A high pressure monitoring control section (high pressure monitoring and control means) 85 is further provided within the high pressure monitoring control section 14 . This high pressure monitoring control section 8
5, the temperature detected by the condensing temperature detection sensor 45 is set as a first reference value TI as the upper limit temperature of the normal operation range.
(for example, 53° C.), and if it is detected that T1 has been exceeded, a compression capacity reduction command is output to the compressor operation control section 80. As a result, the compressor operation control unit 80 switches from the current operating frequency to droop control in which the compression capacity of the compressor 1 is successively reduced at a rate of, for example, 8 Hz/min. As a result, the high pressure decreases, and therefore, when the temperature detected by the condensing temperature detection sensor 45 decreases to the return temperature, the load response control for the compressor 1 is restarted.

Furthermore, despite the droop control as described above, if the temperature detected by the condensing temperature detection sensor 45 exceeds the second reference temperature (for example, 65° C.) set as the operating limit temperature, the outdoor control A high pressure valve control section (high pressure valve control means) 86 provided in the device 74 controls the fourth
An operation of opening the high pressure control valve 56 provided in the bypass pipe 58 is further performed. This allows the discharge pipe 6 to communicate directly with the suction pipe 8, thereby reducing the high pressure.

In this way, by detecting the saturation temperature equivalent to the condensing pressure within the outdoor unit, changes in the high pressure can be more accurately grasped, and thereby control to suppress the rise in pressure can be performed more reliably. It has become a thing.

Next, supercooling control during heating operation in the air conditioner will be explained. First, as shown in FIG. 2, the indoor heat exchanger 31 is equipped with an intermediate temperature sensor 69 that detects the temperature at an intermediate portion thereof, and an outlet temperature sensor 70 that detects the outlet temperature.

Then, as shown in FIG. 4, the subcooling degree control means 87 controls each of the second electric expansion valves so that the temperature difference between the two temperature sensors 69 and 70, that is, the subcooling degree SC of the condensed refrigerant, becomes approximately constant. 18 opening degree controls are performed.

Furthermore, this air conditioner is equipped with an opening correction means 88 as shown in the figure, which means that the temperature D cn detected by the intermediate temperature sensor 69 is the temperature I detected by the condensing temperature detection sensor 45. ) cm of the second electric expansion valve 1.
This is for correcting the opening degree of 8.

The control procedure in the supercooling degree control means 87 and the opening degree correction means 88 will be explained based on the flowchart of FIG. 5. First, when the operation is started (step S1), the opening degree of the second electric expansion valve 18 is set to an initial opening degree stored in advance in a table or the like (step S2). Next step S
3, the condensation temperature sensor 45 and the intermediate temperature sensor 69 detect the temperatures DCI and DcR, respectively, and it is determined in step S4 whether or not they are substantially equal. Both D
If ew and DI are not equal, the intermediate temperature sensor 69
Since the detected temperature D cn is not the high pressure saturation temperature, the opening degree of the second electric expansion valve 18 is corrected according to the difference between the two D C1% DCR (step s5).

On the other hand, when both D0 and D cn are equal, in step S6, the degree of supercooling SC is determined based on the temperatures detected by the intermediate temperature sensor 69 and the outlet temperature sensor 70. In step S7), the degree of supercooling SC is determined as the target. When the opening degree is approximately equal to the value, the opening degree is maintained (step S8).
1. When it is not substantially equal to the target value, the opening degree of the second electric expansion valve 18 is controlled according to the deviation (step S9).

By performing the above control, even if the volume, path shape, connecting piping length, etc. of the indoor heat exchanger 31 vary, the degree of subcooling SC of the condensed refrigerant in the indoor heat exchanger 31 can be maintained. However, this is performed based on the appropriate high-pressure saturation temperature DCI, and as a result, the temperature detected by the intermediate temperature sensor 69 of the indoor heat exchanger 31 reaches the supercooling range and proper supercooling control is not performed. This makes it possible to avoid inconvenient situations such as becoming unable to do so.

The above description has been made by taking as an example the heating operation of a multi-type air conditioner capable of switching between cooling and heating. In the above configuration, the heat exchange section 42 of the first bypass pipe 41 exchanges heat with the suction pipe 8. Provided at a possible location, or the first bypass pipe 41
It is possible within the scope of the present invention to provide other configurations such as connecting the pump to the discharge pipe 6 and interposing an on-off valve to shut off the flow during cooling operation. Further, the present invention can also be applied to heat pump systems other than the above-mentioned multi-type air conditioner.

(Effect of the invention) As described above, in the heat pump system according to the first claim, since the condensation temperature can be detected near the compressor, for example, the connecting piping that occurs in the conventional multi-type air conditioner can be used. without being affected by pressure loss, etc.
By detecting the condensation temperature, changes in the high pressure can be more accurately grasped.

Based on the detected temperature, control is performed to reduce the compression capacity of a compressor with variable compression capacity, for example, as in the heat pump system according to the second claim, or as in the heat pump system according to the third claim. Second, by controlling the opening of a high-pressure control valve that connects the discharge-side gas pipe in a high-pressure state and the suction-side gas pipe in a low-pressure state to communicate with each other, abnormal increases in high pressure can be more reliably prevented. I can do it.

Furthermore, in the heat pump system according to the fourth aspect, supercooling control can be performed based on an appropriate high-pressure saturation temperature, so that even when the volume of the condenser, the path shape, and the length of the connecting piping are significantly changed, Also, it becomes possible to perform supercooling control with high precision.

[Brief explanation of drawings]

FIG. 1 is a functional block diagram of the present invention, and FIG. 2 is a refrigerant circuit diagram of a multi-type air conditioner according to an embodiment of the present invention.
FIG. 3 is an operational control system diagram of the air conditioner, FIG. 4 is a functional block diagram for performing supercooling control, and FIG. 5 is a flowchart of an example of the control procedure. 1...Compressor, 6...Discharge piping (discharge side gas pipe),
8... Suction pipe (suction side gas pipe), lO... First gas pipe (suction side gas pipe), 11... Outdoor heat exchanger (evaporator), 13... First liquid pipe ( low pressure side liquid pipe), 14...
1st electric expansion valve (expansion mechanism), 17...2nd liquid pipe (high pressure side liquid pipe), 18...2nd electric expansion valve, 25...2nd gas pipe (discharge side gas pipe), 31... Indoor heat exchanger (
condenser), 41... first bypass pipe, 42... heat exchange section, 43... first throttle, 45... condensing temperature detection sensor (condensing temperature detection means), 56... high pressure control valve, 5
8...4th bypass pipe (bypass pipe for preventing abnormal pressure increase)
, 69... Intermediate temperature sensor, 70... Outlet temperature sensor, 74... Outdoor control device (operation control means), 85.
...High pressure monitoring control unit (high pressure monitoring and control means), 86...
High pressure valve control section (high pressure valve control means), 87... Supercooling degree control means, 88... Opening degree correction means.

Claims (1)

[Claims] 1. The compressor (1) is equipped with, in order from the discharge side, a discharge side gas pipe (6) (25), a condenser (31), and a high pressure side liquid pipe (17).
), expansion mechanism (14), low pressure side liquid pipe (13), evaporator (
11), connect the suction side gas pipes (10) and (8) to form a refrigerant circulation circuit, and discharge from the compressor (1) from the condenser (31) side to the evaporator (11) side. A heat pump system comprising an operation control means (74) for controlling operation to circulate refrigerant, and interconnecting the discharge side gas pipes (6) (25) and the low pressure side liquid pipe (13). At the same time, a first bypass pipe (41) with a first throttle (43) interposed therein is provided, and this first bypass pipe (41) is further provided with a discharge side gas pipe (
6) A heat exchange part (42) capable of exchanging heat with the suction side gas pipes (10) and (8) is provided on the (25) side, and the temperature of the refrigerant liquefied is detected through this heat exchange part (42). A heat pump system characterized in that it is provided with a condensing temperature detection means (45). 2. The compressor (1) is configured with a variable compression capacity compressor, and when the temperature detected by the condensing temperature detection means (45) exceeds the first reference value, the compressor (1) The heat pump system according to claim 1, further comprising high pressure monitoring control means (85) for issuing a compression capacity reduction command to the operation control means (74). 3. Furthermore, the above-mentioned discharge side gas pipe (6
) (25) and the suction side gas pipes (10) and (8), and when the temperature detected by the condensing temperature detection means (45) exceeds the second reference value, the high pressure control valve ( 56
3. The heat pump system according to claim 1, further comprising high pressure valve control means (86) for controlling the valve to open. 4. The expansion mechanism (14) includes an electric expansion valve (18), and an intermediate temperature sensor (69) that detects the intermediate temperature of the condenser (31) and an outlet temperature of the condenser (31). The opening of the electric expansion valve (18) is controlled to maintain the degree of subcooling of the condensed refrigerant approximately constant based on the temperature detected by the outlet temperature sensor (70) and both temperature sensors (69) and (70). The electric expansion valve (18) is further provided with a supercooling degree control means (87) to reduce the temperature difference detected between the intermediate temperature sensor (69) and the condensing temperature detection means (45). Opening correction means (88
) The heat pump system according to claim 1, further comprising: