JP5753977B2 - Refrigeration cycle equipment - Google Patents

Description

  The present invention relates to a refrigeration cycle apparatus.

  Conventionally, this type of refrigeration cycle apparatus includes a pressure switch or a pressure sensor that detects that the refrigerant pressure has abnormally increased (see, for example, Patent Document 1).

  FIG. 7 shows a refrigeration cycle apparatus mounted on a heat pump water heater. 1 is a compressor, 2 is a radiator, 3 is an expansion valve, 4 is an evaporator, 5 is an internal heat exchanger, and these are annular in this order. The refrigerant circuit 6 is formed.

  FIG. 8 is a cross-sectional view of the internal heat exchanger 5, 21 is a high-pressure side flow path of the internal heat exchanger 5, and 22 is a low-pressure side flow path. 14 is a water inlet pipe and 15 is a hot water outlet pipe. A pressure switch 51 is connected to a branch pipe 55 branched from the refrigerant circuit 6 between the compressor 1 and the radiator 2. A switch means 52 is provided on an AC power supply circuit supplied to the refrigeration cycle apparatus. The AC power supply circuit is configured on the control board 23 of the refrigeration cycle apparatus.

  The high-pressure refrigerant discharged from the compressor 1 is supplied to the radiator 2, performs heat exchange with water in the radiator 2, dissipates heat, and then passes through the high-pressure channel 21 of the internal heat exchanger 5 to the expansion valve 3. Supplied. The low-pressure refrigerant decompressed by the expansion valve 3 is supplied to the evaporator 4 and absorbs heat, and then sucked into the compressor 1 through the low-pressure side passage 22 of the internal heat exchanger 5.

  In the internal heat exchanger 5, the heat energy is usually transferred from the refrigerant flowing through the high-pressure side passage 21 to the refrigerant flowing through the low-pressure side passage 22, so that the refrigerant is in an operating condition where the amount of refrigerant is excessive. It plays a role in regulating the amount.

  On the other hand, in this type of refrigeration cycle apparatus, by operating the pressure switch 51 when the pressure of the refrigerant discharged from the compressor 1 exceeds a preset threshold, the operation of the refrigeration cycle apparatus is stopped, An abnormal rise in discharge pressure is prevented.

  This is because, in a refrigeration cycle apparatus (for example, a refrigeration cycle apparatus mounted on an air conditioner using R410A as a refrigerant) in which the discharge pressure of the refrigerant discharged from the compressor 1 is equal to or lower than the critical pressure, the refrigerant in the condenser Although the discharge pressure can be estimated from the condensation temperature of the refrigeration and an abnormal increase in the discharge pressure can be recognized, the refrigeration cycle apparatus in which the discharge pressure exceeds the critical pressure (for example, a refrigeration installed in a heat pump water heater that uses carbon dioxide as a refrigerant) This is because it is difficult to estimate the discharge pressure from the refrigerant temperature in the radiator 2 in the cycle device.

  The pressure switch 51 operates when the pressure of the refrigerant discharged from the compressor 1 exceeds a preset threshold value, and the switch means 52 is switched from on to off in accordance with the operation of the pressure switch 51 to switch the AC power source. Shut off the circuit.

  By providing these, even in the refrigeration cycle apparatus in which the refrigerant is in a supercritical state on the high-pressure side, it is possible to recognize an abnormal increase in discharge pressure, stop the operation of the refrigeration cycle apparatus, and increase the discharge pressure abnormally. Play a role to prevent.

  Alternatively, instead of the pressure switch, there may be provided a discharge pressure estimation means for estimating the discharge pressure (see, for example, Patent Document 2).

  The refrigeration cycle apparatus shown in FIG. 9 does not include pressure detection means such as a pressure switch or a pressure sensor, but includes discharge pressure estimation means 11 that estimates the discharge pressure from the operating state of the refrigeration cycle apparatus.

  The compressor current value detection means 7 detects the current flowing to the motor of the compressor 1, the compressor rotation speed detection means 53 detects the rotation speed of the motor, and the refrigerant sent from the radiator 2 to the expansion valve 3. A radiator outlet temperature detecting means 54 for detecting the temperature and an evaporator temperature detecting means 8 for detecting the refrigerant temperature in the evaporator 4 are provided. The discharge pressure estimating means 11 includes at least the compressor current value detecting means 7 and the compression. Based on the values detected by the machine rotation speed detection means 53, the radiator outlet temperature detection means 54, and the evaporator temperature detection means 8, the power consumption of the motor, the evaporator temperature, and the discharge previously recorded by the discharge pressure estimation means 11 The discharge pressure is estimated using the correlation with the pressure and the like.

  By providing the discharge pressure estimating means 11, the discharge pressure can be recognized without a pressure switch or a pressure sensor.

JP 2006-90658 A JP 20043692 A

  However, the refrigeration cycle apparatus described in Patent Document 1 has a problem that a circuit loss occurs in the switch means 52 of the pressure switch 51 and the energy consumption efficiency of the refrigeration cycle apparatus is reduced.

  On the other hand, the refrigeration cycle apparatus described in Patent Document 2 includes discharge pressure estimation means 11 that estimates the discharge pressure from the operating state of the refrigeration cycle apparatus without including pressure detection means such as a pressure switch and a pressure sensor. Although the circuit loss due to the pressure detection means does not occur, when the refrigeration cycle apparatus includes an internal heat exchanger between the evaporator and the compressor, the heat of the internal heat exchanger in a transient state such as immediately after startup The suction temperature and density change due to a sudden change in the exchange amount, and the discharge pressure estimation means 11 estimates using the correlation with the electric power consumption, evaporator temperature, discharge pressure, etc. recorded in advance. The accuracy of the discharged pressure was impaired.

  The present invention solves the above-mentioned conventional problems, and in a refrigeration cycle apparatus having a heat exchanger between an evaporator and a compressor, pressure detection means for directly detecting pressure such as a pressure sensor and a pressure switch is provided. Even if it is not, it aims at providing the refrigerating-cycle apparatus which can recognize the fluctuation | variation of intake temperature correctly and can estimate discharge pressure with high precision in transient states, such as immediately after starting.

In order to achieve the above object, a refrigeration cycle apparatus according to the present invention includes a compressor, a radiator, a decompression mechanism, a refrigerant circuit in which an evaporator is connected in an annular shape and a refrigerant circulates, and the evaporator and the compressor. A heat exchanger provided in between, a compressor current value detecting means for detecting a current supplied to the compressor, an evaporator temperature detecting means for detecting a temperature of a refrigerant circulating in the evaporator, and the compression Suction temperature detection means for detecting the temperature of refrigerant sucked into the machine, discharge temperature detection means for detecting the temperature of refrigerant discharged from the compressor, current value detected by the compressor current value detection means, and Discharge pressure estimation for estimating the discharge pressure of the compressor based on the evaporator temperature detected by the evaporator temperature detection means, the suction temperature detected by the suction temperature detection means, and the discharge temperature detected by the discharge temperature detection means Having means The one in which the features.

  As a result, even if the heat exchange amount in the heat exchanger changes suddenly in a transient state such as immediately after the operation of the refrigeration cycle apparatus, even if the suction superheat degree and density fluctuate accordingly, the suction temperature detection means It becomes possible to correctly recognize temperature fluctuations and estimate the discharge pressure with high accuracy.

  The superheat degree of the refrigerant sucked into the compressor is a difference between the refrigerant temperature sucked into the compressor 1 and the saturation temperature of the refrigerant sucked into the compressor.

  According to the present invention, in a refrigeration cycle apparatus having a heat exchanger between an evaporator and a compressor, without providing pressure detection means for detecting direct pressure such as a pressure sensor or a pressure switch, In the transient state, it is possible to provide a refrigeration cycle apparatus capable of correctly recognizing a change in suction temperature and estimating the discharge pressure with high accuracy.

Schematic configuration diagram of a refrigeration cycle apparatus according to Embodiment 1 of the present invention. Time-dependent change diagram of the evaporator temperature Te and the suction temperature Ts immediately after the start of the refrigeration cycle apparatus Correlation diagram of estimated discharge pressure against current value, evaporator temperature and superheat degree of the compressor Time-dependent change figure of discharge pressure Pd after starting of the refrigeration cycle apparatus The figure which shows the correction value of the discharge pressure Pd after starting the refrigerating-cycle apparatus in Embodiment 3 of this invention. Changes over time in discharge pressure Pd and COP after starting the refrigeration cycle apparatus Schematic configuration diagram of a conventional refrigeration cycle apparatus Sectional view of the internal heat exchanger installed in a conventional refrigeration cycle system Schematic configuration diagram of another conventional refrigeration cycle apparatus

A first invention includes a compressor, a radiator, a decompression mechanism, a refrigerant circuit in which an evaporator is connected in an annular shape and a refrigerant circulates, a heat exchanger provided between the evaporator and the compressor, Compressor current value detecting means for detecting the current supplied to the compressor, evaporator temperature detecting means for detecting the temperature of the refrigerant circulating in the evaporator, and detecting the temperature of the refrigerant sucked into the compressor Suction temperature detecting means, discharge temperature detecting means for detecting the temperature of refrigerant discharged from the compressor, current value detected by the compressor current value detecting means, and evaporator detected by the evaporator temperature detecting means And a discharge pressure estimating means for estimating a discharge pressure of the compressor based on the temperature, the suction temperature detected by the suction temperature detecting means, and the discharge temperature detected by the discharge temperature detecting means. Cycle equipment.

  As a result, in a transient state such as immediately after the start of the refrigeration cycle apparatus, even if the suction superheat degree and the density greatly change due to a sudden change in the heat exchange amount in the heat exchanger, the compressor current value and the evaporator temperature Using the suction temperature detected by the suction temperature detection means, the discharge pressure can be estimated with high accuracy even in a transient state.

In addition, a discharge temperature detecting means for detecting the temperature of the refrigerant discharged from the compressor is provided, and the discharge pressure estimating means estimates the discharge pressure by adding the discharge temperature detected by the discharge temperature detecting means. .

As a result, even if the refrigerant temperature discharged from the compressor does not reach a steady state in a transient state such as immediately after the start of the refrigeration cycle apparatus, the compressor main body and the compressor can be used depending on the discharge temperature detected by the discharge temperature detecting means. It is possible to estimate the amount of energy consumed to increase the temperature of the peripheral piping connected to the compressor, and to estimate the energy supplied to the refrigerant out of the power supplied to the compressor. The discharge pressure can be estimated with accuracy.

  In particular, the third invention is the refrigeration cycle in the first or second invention, by reducing the rotational speed of the compressor when the discharge pressure estimated by the discharge pressure estimating means exceeds a preset threshold value. An abnormal increase in the discharge pressure of the apparatus can be prevented.

  In a fourth aspect of the invention, in particular, in the first or second aspect of the invention, when the discharge pressure estimated by the discharge pressure estimating means exceeds a preset threshold value, the pressure reduction amount of the pressure reduction mechanism is reduced, thereby reducing the refrigeration cycle. An abnormal increase in the discharge pressure of the apparatus can be prevented.

  According to a fifth aspect of the invention, in particular, in the first or second aspect of the invention, the circulation of the refrigerant flowing through the pressure reducing mechanism so that the discharge pressure estimated by the discharge pressure estimating means matches a preset target value of the discharge pressure. By adjusting the amount, the refrigeration cycle apparatus can be operated with high energy efficiency.

  In a sixth aspect of the invention, in particular, in any one of the first to fifth aspects of the invention, when the cold compressor is driven, the discharge pressure is reduced even in a refrigeration cycle apparatus in which the refrigerant on the high pressure side of the refrigerant circuit is in a supercritical state. It can be estimated with high accuracy.

  In the seventh invention, in particular, by using carbon dioxide as the refrigerant described in the sixth invention, there is no danger of combustion even if the refrigerant leaks, and the refrigeration cycle apparatus can be operated with peace of mind.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a configuration diagram of a refrigeration cycle apparatus according to a first embodiment of the present invention. FIG. 1 shows a refrigeration cycle apparatus mounted on, for example, a heat pump water heater, as a compressor 1, a radiator 2, an expansion valve 3 as a decompression mechanism of the present invention, an evaporator 4, and a heat exchanger of the present invention. An internal heat exchanger 5 is provided and connected in an annular shape to constitute a refrigerant circuit 6.

  The radiator 2 includes a water inlet pipe 14 that supplies water to be exchanged with the refrigerant from below a hot water storage tank (not shown) via a circulation pump (not shown), and a hot water outlet pipe that returns the water to the upper side of the hot water storage tank. 15 is provided.

  In the refrigerant circuit 6, carbon dioxide circulates as a refrigerant, and the refrigerant supplied from the radiator 2 to the expansion valve 3 flows through the high-pressure side passage 21 of the internal heat exchanger 5, and from the evaporator 4 to the compressor. The refrigerant supplied to 1 circulates in the low pressure side flow path 22 of the internal heat exchanger 5.

  The evaporator temperature detecting means 8 for detecting the temperature of the refrigerant circulating in the evaporator 4 is on the pipe surface at the refrigerant inlet of the evaporator 4, and the suction temperature detecting means 9 is on the pipe surface for introducing the refrigerant into the compressor 1. The discharge temperature detecting means 10 is provided on the surface of the pipe for introducing the refrigerant from the compressor 1 to the radiator 2.

Further, on the circuit of the control board 23 for controlling the rotational speed of the compressor 1 and the opening degree of the expansion valve 3, the compressor current value detecting means 7 for detecting the current supplied to the compressor 1, and at least the compressor The pressure of the refrigerant discharged from the compressor 1 is estimated using the current value detected by the current value detection means 7, the evaporator temperature detected by the evaporator temperature detection means 8, and the suction temperature detected by the suction temperature detection means 9. Discharge pressure estimating means 11 for performing the operation, compressor control means 12 for adjusting the rotational speed of the compressor 1, and expansion valve control means 13 for adjusting the opening degree of the expansion valve 3.

  About the refrigerating-cycle apparatus comprised as mentioned above, the operation | movement and an effect | action are demonstrated below.

  When the compressor 1 is operated, the refrigerant compressed and discharged to a high pressure is sent to the radiator 2 and radiates heat by exchanging heat with the low-temperature water that has passed through the water inlet pipe 14 by the power of the circulation pump. Thereby, the heated low temperature water turns into high temperature water, passes through the hot water supply piping 15, is sent to the hot water storage tank, and is stored as hot hot water.

  The refrigerant flowing out of the radiator 2 is supplied to the expansion valve 3 through the high-pressure channel 21 of the internal heat exchanger 5 and decompressed and expanded, sent to the evaporator 4, and air and heat sent by the blower fan. Exchange and evaporate to gasify. The gasified refrigerant passes through the low-pressure side passage 22 of the internal heat exchanger 5 and is again sucked into the compressor 1 and is compressed again, so that the low-temperature water in the hot water storage tank is gradually heated. .

  The hot water heated and stored in the hot water storage tank is supplied with hot water from a hot water supply terminal (not shown) such as a faucet or a shower, so that the refrigeration cycle apparatus can be used as a hot water heater, for example.

  First, the control operation of the compressor control means 12 and the expansion valve control means 13 when the discharge pressure is equal to or less than a preset threshold value P0 will be described.

  When the refrigeration cycle apparatus is operating, the compressor control means 12 adjusts the rotational speed fc of the compressor 1 so that the heating capacity in the radiator 2 becomes a preset rotational speed so as to be a target value. Adjusted.

  Accordingly, the refrigeration cycle apparatus can be operated by selecting a rotation speed that satisfies the required heating capacity according to the operating conditions.

  The opening degree of the expansion valve 3 is adjusted by the expansion valve control means 13 so that the discharge temperature Td detected by the discharge temperature detection means 10 coincides with a preset target value.

  Accordingly, the refrigeration cycle apparatus can be operated with high energy consumption efficiency by controlling the opening degree of the expansion valve 3 using the discharge temperature at which the energy consumption efficiency is maximized as the target discharge temperature.

  The expansion valve control means 13 sets the target value of the discharge temperature Td in advance so that the degree of superheat of the refrigerant sucked into the compressor 1 is substantially constant, so that the refrigeration cycle apparatus is in a substantially steady state. In this case, the degree of superheat of the refrigerant sucked into the compressor 1 becomes substantially constant by adjusting the expansion valve 3.

  Next, the control operation of the compressor control means 12 when the discharge pressure exceeds a preset threshold value P0 will be described.

  When the discharge pressure exceeds a preset threshold value P0, the compressor control means 12 determines that an abnormal increase in pressure has occurred in the refrigeration cycle apparatus and reduces the rotational speed of the compressor 1 (for example, setting the threshold value P0). After that, it decreases by 2 Hz every 10 seconds until it becomes P0 or less).

  Further, a discharge pressure estimation method performed by the discharge pressure estimation unit 11 will be described.

  The compressor current value detection means 7 detects the value of the current supplied to the compressor 1 via the control board 23 and sends the detected current value Ic as a signal to the discharge pressure estimation means 11.

  The evaporator temperature detecting means 8 detects the temperature of the pipe surface at the refrigerant side inlet of the evaporator 4 and sends the detected evaporator temperature Te as a signal to the discharge pressure estimating means 11.

  The suction temperature detection means 9 detects the temperature of the refrigerant sucked into the compressor 1 and sends the detected suction temperature Ts as a signal to the discharge pressure estimation means 11.

  Since the evaporator temperature detecting means 8 detects the temperature of the refrigerant side inlet of the evaporator 4, when the operation of the refrigeration cycle apparatus is in a substantially steady state, the detected evaporator temperature Te corresponding to the degree of superheat and Although the temperature difference from the suction temperature Ts is substantially constant, when the refrigeration cycle apparatus is in a transient state such as immediately after startup (for example, immediately after startup of the compressor 1), the amount of heat exchange in the internal heat exchanger 5 is abrupt. The degree of superheat changes greatly with the change, and the discharge pressure estimation means 11 cannot estimate the discharge pressure with high accuracy.

  However, by detecting the suction temperature Ts by the suction temperature detection means 9, even if the refrigeration cycle apparatus is in a transient state, the suction temperature Ts can be detected without impairing accuracy as shown in FIG.

  In this way, the discharge pressure Pd is estimated from the correlation diagram of the estimated discharge pressure shown in FIG. 3 using the detected suction temperature Ts.

  In this way, even if the superheat degree changes greatly with the change of the heat exchange amount in the internal heat exchanger 5 immediately after the start of the refrigeration cycle apparatus, the suction temperature detection means 9 detects the suction temperature Ts. Accordingly, as shown in FIG. 4, the discharge pressure Pd can be estimated with higher accuracy than when the suction temperature Ts is detected and not used.

  When the discharge pressure Pd estimated by the discharge pressure estimation means 11 as described above exceeds a preset threshold value P0, the compressor control means 12 determines that an abnormal increase in pressure has occurred in the refrigeration cycle apparatus and rotates. Reduce the discharge pressure by reducing the speed.

  When the suction temperature Ts is not detected and used, as shown in FIG. 4, the discharge pressure Pd is estimated to be high, and it is determined that the true discharge pressure has not reached the threshold value P0. Although the rotational speed of the machine 1 has been reduced, by doing so, even if the degree of superheat changes with the change in the heat exchange amount in the internal heat exchanger 5 immediately after the start of the refrigeration cycle apparatus, The rotational speed of the compressor 1 can be reduced by correctly determining the occurrence of an abnormal increase in the pressure of the refrigeration cycle apparatus.

  As described above, in the present embodiment, the discharge pressure estimating means 11 uses the current value Ic detected by the compressor current value detecting means 7, the evaporator temperature Te detected by the evaporator temperature detecting means 8, and the suction temperature detecting means. By estimating the discharge pressure Pd using the suction temperature Ts detected by 9, in a transient state such as immediately after the start of the refrigeration cycle apparatus, the degree of superheat increases with a rapid change in the amount of heat exchange in the internal heat exchanger. Even if it changes greatly, it acts so that the intake temperature can be detected without impairing accuracy.

As a result, even when the refrigeration cycle device is in a transient state such as immediately after startup, it is possible to correctly recognize the occurrence of an abnormal increase in discharge pressure, and to reduce the discharge pressure by reducing the rotation speed of the compressor, thereby reducing the design pressure. It is possible to prevent operation at an abnormal pressure exceeding.

  The compressor control means 12 stops the operation of the compressor 1 instead of reducing the rotational speed of the compressor 1 when the discharge pressure estimated by the discharge pressure estimation means 11 exceeds a preset threshold value P0. It may be allowed.

(Embodiment 2)
Since the configuration and basic operation of the refrigeration cycle apparatus in the second embodiment of the present invention are the same as those in the first embodiment, description thereof will be omitted.

  Further, a method for determining the compressor rotation speed when the discharge pressure is less than or equal to a preset threshold value P0, the compressor current value detection means 7, the evaporator temperature detection means 8, the suction temperature detection means 9, and the discharge temperature detection means 10 Since the operation is the same as that of the first embodiment, the description is omitted.

  Below, the control method of the expansion valve 3 of the expansion valve control means 13 which differs in Embodiment 1 and this Embodiment is demonstrated.

  When the discharge pressure estimated by the discharge pressure estimation unit 11 exceeds a preset threshold value P0, the expansion valve control unit 13 of the present embodiment reduces the rotational speed of the compressor 1 as in the first embodiment. Instead, the opening degree of the expansion valve 3 is increased.

  Thereby, the circulation amount of the refrigerant | coolant which flows through the expansion valve 3 increases, and the discharge pressure Pd falls. By doing so, in a transient state such as immediately after the start of the refrigeration cycle apparatus, even if the accuracy of the discharge pressure Pd estimated by the discharge pressure estimation means 11 is somewhat worse, the opening of the expansion valve 3 is increased and the discharge is performed. The operation of the compressor 1 can be safely continued by once reducing the pressure Pd. Then, by continuing the operation of the compressor 1, it is possible to correctly determine the occurrence of an abnormal increase in the pressure of the refrigeration cycle apparatus, and to suppress the abnormal increase in the discharge pressure exceeding the design pressure.

(Embodiment 3)
Since the configuration of the refrigeration cycle apparatus in the third embodiment of the present invention is the same as that in the first embodiment, the description thereof is omitted.

  The method of determining the compressor rotational speed when the refrigeration cycle apparatus is operating, the operation of the compressor current value detecting means 7, the evaporator temperature detecting means 8, the suction temperature detecting means 9 and the discharge temperature detecting means 10 are as follows. Since it is the same as that of Embodiment 1, description is abbreviate | omitted.

  Two points of the control method of the expansion valve 3 of the expansion valve control means 13 and the estimation method of the discharge pressure estimation means 11 which are different between the first and second embodiments and the present embodiment will be described below.

  The discharge temperature detection means 10 detects the temperature of the pipe surface through which the refrigerant discharged from the compressor 1 circulates, and sends the discharge temperature Td as a signal to the discharge pressure estimation means 11.

  Since the discharge temperature detecting means 10 detects the pipe surface temperature, when the operation of the refrigeration cycle apparatus is in a substantially steady state, the detected discharge temperature Td and the refrigerant temperature inside the pipe are substantially the same. When the cycle device is in a transient state such as immediately after startup, the refrigerant temperature discharged from the compressor 1 changes abruptly, so the detected discharge temperature Td has a time delay and does not match the refrigerant temperature inside the pipe. The discharge temperature Td detected by the discharge temperature detection means 10 gradually approaches the refrigerant temperature discharged from the compressor 1 as time elapses after the refrigeration cycle apparatus is started.

In addition to the current value Ic detected by the compressor current value detecting means 7, the evaporator temperature Te detected by the evaporator temperature detecting means 8, and the suction temperature Ts detected by the suction temperature detecting means 9, the discharge pressure estimating means 11 The discharge pressure Pd is estimated based on the discharge temperature Td detected by the discharge temperature detecting means 10.

  When the operation of the refrigeration cycle apparatus is in a substantially steady state and the discharge temperature Td detected by the discharge temperature detecting means 10 is sufficiently close to the refrigerant temperature inside the pipe, the estimated discharge pressure prepared in advance shown in FIG. , The current value Ic and the evaporator temperature Te are used to estimate the discharge pressure Pd.

  On the other hand, when the refrigeration cycle apparatus is in a transient state such as immediately after startup, the temperature of the compressor 1 and the piping connected to the periphery thereof is not sufficiently increased, and a part of the power supplied to the compressor 1 Since only the refrigerant is supplied with energy, the correlation between the discharge temperature Td detected by the discharge temperature detecting means 10 and the energy supplied to the refrigerant is grasped in advance, and the discharge pressure as shown in FIG. 5 created based on this correlation is obtained. The true discharge pressure Pd is estimated by adding a correction value. FIG. 5 shows the correction value of the discharge pressure Pd for each discharge temperature Td.

  By doing in this way, even if the temperature of the piping connected to the compressor 1 or its circumference | surroundings is not fully rising in transient states, such as immediately after starting of a refrigerating cycle apparatus, the discharge temperature detection means 10 detects A more accurate discharge pressure Pd can be estimated based on the temperature Td.

  FIG. 6 shows changes over time in the discharge pressures Pd and COP after the start of the refrigeration cycle apparatus. The solid line in FIG. 6 is the actual discharge pressure, the long broken line is an estimated value when correction is not performed using the discharge temperature Td, and the short broken line is an estimated value when correction is performed using the discharge temperature Td. It is.

  As shown in FIG. 6, when correction is not performed using the discharge temperature Td, the discharge pressure Pd that has been estimated to be higher is corrected using the discharge temperature Td, so that it is close to the actual discharge pressure. The value can be estimated with high accuracy.

  The opening degree of the expansion valve 3 is controlled by the expansion valve control means 13 so that the discharge pressure Pd estimated by the discharge pressure estimation means 11 becomes a predetermined target value. In this way, as shown in FIG. 6, the expansion valve 3 can be controlled and operated so that the energy consumption efficiency of the refrigeration cycle apparatus is maximized in a transient state such as immediately after the start of the refrigeration cycle apparatus. .

  As described above, in the present embodiment, the discharge pressure estimating means 11 has the current value Ic detected by the compressor current value detecting means 7, the evaporator temperature Te detected by the evaporator temperature detecting means 8, and the suction temperature detecting means. 9 is used to estimate the discharge pressure Pd using the suction temperature Ts detected by the discharge temperature detection means 10 and the discharge temperature Td detected by the discharge temperature detection means 10, so that the compressor 1 and its surroundings are in a transient state such as immediately after the start of the refrigeration cycle apparatus Even if the temperature of the pipe connected to is not sufficiently increased, a more accurate discharge pressure Pd can be correctly estimated using the discharge temperature Td detected by the discharge temperature detecting means 10.

  As a result, even when the refrigeration cycle apparatus is in a transient state such as immediately after startup, the discharge pressure Pd is correctly estimated, and the opening degree of the expansion valve 3, that is, the refrigerant flowing through the expansion valve 3 using the estimated discharge pressure Pd. The amount of circulation of the refrigeration cycle apparatus can be adjusted so that the energy consumption efficiency of the refrigeration cycle apparatus is maximized.

Note that the compressor control means 12 may reduce the rotational speed of the compressor 1 when the discharge pressure estimated by the discharge pressure estimation means 11 exceeds a preset threshold value P0. The expansion valve control means 13 may increase the opening of the expansion valve 3 when the discharge pressure estimated by the discharge pressure estimation means 11 exceeds a preset threshold value P0.

  By doing so, in a transient state such as immediately after the start of the refrigeration cycle apparatus, even if the accuracy of the discharge pressure Pd estimated by the discharge pressure estimating means 11 is somewhat poor, the compressor is temporarily reduced by reducing the discharge pressure Pd. The operation of 1 can be safely continued.

  Then, by continuing the operation of the compressor 1, it is possible to correctly determine the occurrence of an abnormal increase in the pressure of the refrigeration cycle apparatus, and to suppress the abnormal increase in the discharge pressure exceeding the design pressure.

  As described above, the refrigeration cycle apparatus according to the present invention can estimate the discharge pressure from the compressor without providing a pressure sensor, a pressure switch, or the like that directly detects the pressure. In the refrigeration cycle apparatus used in the apparatus or the like, it can be applied to the improvement of energy efficiency and the use of a protection apparatus.

DESCRIPTION OF SYMBOLS 1 Compressor 2 Radiator 3 Expansion valve 4 Evaporator 5 Internal heat exchanger 6 Refrigerant circuit 7 Compressor current value detection means 8 Evaporator temperature detection means 9 Suction temperature detection means 10 Discharge temperature detection means 11 Discharge pressure estimation means 12 Compression Machine control means 13 Expansion valve control means 14 Inlet piping 15 Outlet piping 21 High pressure side passage 22 Low pressure side passage 23 Control board 51 Pressure switch 52 Switch means 53 Compressor rotational speed detection means 54 Radiator outlet temperature detection means 55 Branch piping

Claims (6)

A refrigerant circuit in which a compressor, a radiator, a decompression mechanism, an evaporator are connected in an annular shape and a refrigerant circulates;
A heat exchanger provided between the evaporator and the compressor;
Compressor current value detecting means for detecting current supplied to the compressor;
Evaporator temperature detecting means for detecting the temperature of the refrigerant circulating in the evaporator;
Suction temperature detection means for detecting the temperature of refrigerant sucked into the compressor;
Discharge temperature detecting means for detecting the temperature of the refrigerant discharged from the compressor;
Based on the current value detected by the compressor current value detection means, the evaporator temperature detected by the evaporator temperature detection means, the suction temperature detected by the suction temperature detection means, and the discharge temperature detected by the discharge temperature detection means. And a discharge pressure estimating means for estimating the discharge pressure of the compressor. 2. The refrigeration cycle apparatus according to claim 1 , wherein when the discharge pressure estimated by the discharge pressure estimation unit exceeds a preset threshold value, the rotation speed of the compressor is decreased. 2. The refrigeration cycle apparatus according to claim 1 , wherein when the discharge pressure estimated by the discharge pressure estimation unit exceeds a preset threshold value, the pressure reduction amount of the pressure reduction mechanism is reduced. Frozen according to claim 1, characterized in that the discharge pressure estimated by said discharge pressure estimation means to match a predetermined target value of the discharge pressure to adjust the circulation amount of the refrigerant flowing through the pressure reducing mechanism Cycle equipment. Wherein at the time of driving the compressor, the high pressure side of the refrigerant of the refrigerant circuit is a refrigeration cycle apparatus according to any one of claims 1 to 4, characterized in that a supercritical state. The refrigeration cycle apparatus according to claim 5 , wherein carbon dioxide is used as the refrigerant.