JP2014115030A - Heat pump water heater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat pump water heater capable of stabilizing a coefficient of performance without impairing the temperature of heated liquid discharged from a liquid refrigerant heat exchanger.SOLUTION: In the heat pump water heater, a control part calculates a target discharge temperature of a compressor (S2), and controls opening of a pressure reducer on the basis of the difference between a discharge temperature of the compressor detected by a temperature sensor and the target discharge temperature (S3). In addition, the control part calculates a target discharge pressure of the compressor (S2), and corrects the target discharge temperature on the basis of the difference between a discharge pressure of the compressor detected by a pressure sensor and the target discharge pressure (S5,S7,S8,S10,S2).

Description

  The present invention relates to a heat pump water heater.

When performing refrigeration cycle control in a heat pump water heater equipped with a pressure reducing device (pressure reducing valve), there is a method described in Japanese Patent Application Laid-Open No. 2007-139393 (Patent Document 1) as a method for controlling the pressure reducing device. This Patent Document 1 states that “one of a target high pressure value (P _{H 2} O) and a target discharge temperature (T _d O) is set as a target value, and the pressure reducer (230) is set to the target value. Is controlled ”(see claim 1).

JP 2007-139393 A

  In the technique described in Patent Document 1, when control is performed by setting a target temperature value, it is necessary to secure the temperature of the liquid to be heated (tapping temperature) supplied from the liquid refrigerant heat exchanger of the heat pump water heater. It becomes easy. However, because the pressure is not controlled, the pressure difference between the compressor inlet and outlet cannot be managed and the compressor efficiency varies, resulting in large variations in the coefficient of performance (COP) of the heat pump water heater. Become. On the other hand, when control is performed by setting a target pressure value, the performance of the liquid refrigerant heat exchanger that performs heat exchange between the refrigerant and the liquid to be heated can be stably controlled. However, since the discharge temperature of the compressor is not controlled, it is difficult to secure the hot water temperature.

  This invention is made in view of such a situation, and provides the heat pump water heater which can stabilize a coefficient of performance, without impairing the temperature of the to-be-heated liquid which comes out of a liquid refrigerant heat exchanger. Let it be an issue.

  In order to solve the above-described problems, a heat pump water heater according to the present invention includes a compressor that compresses and discharges the sucked refrigerant, and heat exchange between the high-temperature and high-pressure refrigerant discharged from the compressor and the liquid to be heated. A liquid refrigerant heat exchanger that performs pressure reduction, a pressure reducing valve that depressurizes the refrigerant flowing out from the liquid refrigerant heat exchanger, an evaporator that performs heat exchange between the refrigerant flowing out from the pressure reducing valve and air, and the compressor Temperature detecting means for detecting the temperature of the refrigerant discharged from the compressor, pressure detecting means for detecting the pressure of the refrigerant discharged from the compressor, calculating a target discharge temperature of the compressor, and the temperature detecting means A control unit that performs opening degree control of the pressure reducing valve based on a difference between the discharge temperature detected by the target discharge temperature and the target discharge temperature, the control unit calculates a target discharge pressure of the compressor, Detected by pressure detection means Characterized in that to correct the target discharge temperature, based on the difference between the delivery pressure and the target discharge pressure.

  ADVANTAGE OF THE INVENTION According to this invention, the heat pump water heater which can stabilize a coefficient of performance can be provided, without impairing the temperature of the to-be-heated liquid which comes out of a liquid refrigerant heat exchanger.

It is composition explanatory drawing of the heat pump water heater based on one Embodiment of this invention. It is a flowchart which shows the procedure of the correction process of the target discharge temperature by a control part. It is an example of the time chart for demonstrating the timing which corrects target discharge temperature in the heat pump water heater based on this embodiment.

  Next, embodiments of the present invention will be described in detail with reference to the drawings as appropriate. In the present embodiment, a heat pump water heater using water as the liquid to be heated will be described as an example. In the heat pump water heater according to the present embodiment, when the control unit controls the temperature of the refrigerant discharged to the high pressure side of the compressor (the discharge temperature of the compressor) to be the target value (target discharge temperature), the compression is performed. Correct the target value (target discharge temperature) of the compressor discharge temperature so that the pressure of the refrigerant discharged to the high pressure side of the compressor (discharge pressure of the compressor) becomes the target value (target discharge pressure). It is configured as follows. Below, after demonstrated the whole structure of the heat pump water heater which concerns on this embodiment, and the basic operation | movement of a control part, the operation | movement of the control part concerning this invention is demonstrated more concretely.

  FIG. 1 is a configuration explanatory diagram of a heat pump water heater S according to an embodiment of the present invention. As shown in FIG. 1, the heat pump water heater S includes a heat pump unit 1 and a tank unit 2. The heat pump unit 1 and the tank unit 2 may be separated from each other, or may be integrally disposed in one housing.

  The heat pump unit 1 is mainly configured by a compressor 3, a liquid refrigerant heat exchanger 4, a pressure reducing valve 5, an evaporator 6, and a control unit 50. The compressor 3, the liquid refrigerant heat exchanger 4, the pressure reducing valve 5, and the evaporator 6 are connected in a ring shape with piping so that the refrigerant circulates in this order. In the present embodiment, carbon dioxide, which is a refrigerant friendly to the natural environment, is used as the refrigerant. And in the heat pump part 1, since the discharge pressure of the refrigerant | coolant (carbon dioxide) by the compressor 3 uses the supercritical vapor compression refrigeration cycle which becomes more than the critical pressure of the said refrigerant | coolant, and a refrigerant | coolant can be made into high temperature / high pressure, for example, Hot water as high as 90 ° C. can be obtained.

  The compressor 3 compresses the refrigerant returned from the annular circuit, and sends the compressed high-temperature gas refrigerant (hereinafter sometimes referred to as hot gas) to the annular circuit again. More specifically, the compressor 3 sucks and compresses the refrigerant returned from the evaporator 6 and discharges the refrigerant toward the liquid refrigerant heat exchanger 4.

  The capacity of the compressor 3 can be controlled, and when high-temperature hot water storage (for example, 90 ° C.) is performed, the compressor 3 is operated at a higher rotational speed (for example, 3000 to 4000 rotations / minute) than usual. Moreover, when driving | running by normal hot water storage temperature (for example, 65 degreeC), it drive | operates by a comparatively slow rotational speed (for example, 1000-2000 rotation / min). Further, the compressor 3 can control the rotation speed from a low speed (for example, 1000 rotations / minute) to a high speed (for example, 6000 rotations / minute) by PWM control, voltage control (for example, PAM control) and combination control thereof. It has become.

  The piping connecting the compressor 3 and the liquid refrigerant heat exchanger 4 to be described next is close to the compressor 3, the high-pressure side refrigerant temperature, that is, the temperature of the refrigerant discharged from the compressor 3 (of the compressor 3 A temperature sensor (temperature detection means) 9 for detecting the discharge temperature) is provided, and a pressure sensor (pressure) for detecting the high-pressure side refrigerant pressure, that is, the pressure of the refrigerant discharged from the compressor 3 (discharge pressure of the compressor 3). Detection means) 8 is provided.

  The liquid refrigerant heat exchanger 4 functions as a condenser, and a refrigerant heat transfer tube 2a that distributes hot gas (refrigerant) discharged from the compressor 3 and a liquid heat transfer tube that distributes water that is the liquid to be heated. 2b. These refrigerant heat transfer tubes 2a and liquid heat transfer tubes 2b are provided in close contact so that the refrigerant and the liquid to be heated exchange heat with each other. Moreover, the flow of each heat exchanger tube 2a, 2b is comprised so that it may oppose. In the liquid refrigerant heat exchanger 4, heat exchange between the refrigerant discharged from the compressor 3 and the liquid to be heated is performed.

  The pressure reducing valve 5 is provided in the middle of a pipe disposed between the liquid refrigerant heat exchanger 4 and the evaporator 6, and here, an electric expansion valve is used. The pressure reducing valve 5 depressurizes the medium temperature and high pressure refrigerant flowing out from the liquid refrigerant heat exchanger 4, and sends it to the evaporator 6 as a low pressure refrigerant that easily evaporates. The pressure reducing valve 5 can adjust the throttle opening (opening / closing degree), and the control unit 50 changes the throttle opening to adjust the refrigerant circulation amount in the heat pump unit 1. And the control part 50 will adjust the discharge temperature of the compressor 3 by changing the aperture opening degree of the pressure-reduction valve 5, so that it may mention later. In addition, when the control part 50 forms frost on the evaporator 6, in order to melt the frost attached to the evaporator 6, the decompression valve 5 is opened (throttle opening is fully opened) and the defrost operation is performed.

  The evaporator 6 takes in outside air by the rotation of the blower 7 and pumps heat from outside air by causing heat exchange between the refrigerant circulating in the evaporator 6 and the outside air (air blowing). That is, the evaporator 6 performs heat exchange between the refrigerant flowing out of the pressure reducing valve 5 and the air. The refrigerant that has passed through the evaporator 6 is returned to the compressor 3 again. The blower 7 is controlled to rotate at a predetermined rotational speed (rotational speed) command value.

  The temperature sensor 10 detects the temperature of the refrigerant on the downstream side of the evaporator 6. The controller 50 determines whether or not to perform defrosting in the evaporator 6 based on the temperature detected by the temperature sensor 10, and when performing defrosting, fully opens the pressure reducing valve 5. Reference numeral 14 denotes a temperature sensor that detects the outside air temperature. In the present embodiment, the temperature sensor 14 is provided in the vicinity of the blower 7.

  Reference numeral 36 is a delivery pipe, and one end of the delivery pipe 36 is connected to the outlet of the liquid heat transfer tube 2 b of the liquid refrigerant heat exchanger 4. The delivery pipe 36 feeds the liquid to be heated heated by the refrigerant from the liquid refrigerant heat exchanger 4 to the tank unit 2. More specifically, the delivery pipe 36 extends toward the tank 16 side of the tank unit 2 described later, and is connected to the top of the tank 16. Near the liquid refrigerant heat exchanger 4 of the delivery pipe 36, a temperature sensor 12 that detects the temperature of the liquid to be heated that exits from the liquid refrigerant heat exchanger 4 (the temperature of the hot water in the present embodiment) is provided.

  Reference numeral 35 denotes a supply pipe. The supply pipe 35 supplies the liquid to be heated heated by the refrigerant to the liquid refrigerant heat exchanger 4. One end of the supply pipe 35 is connected to the inlet of the liquid heat transfer tube 2 b of the liquid refrigerant heat exchanger 4. The supply pipe 35 extends toward the tank 16 described later, and is connected to the bottom of the tank 16. Near the liquid refrigerant heat exchanger 4 of the supply pipe 35, a temperature sensor 11 for detecting the temperature of the heated liquid entering the liquid refrigerant heat exchanger 4 (incoming water temperature in the present embodiment) is provided.

  Further, the pump 13 is disposed in the supply pipe 35 on the upstream side of the liquid refrigerant heat exchanger 4. The pump 13 is driven so as to send the liquid to be heated from the tank 16 described later to the inlet side of the liquid heat transfer tube 2b. The pump 13 is configured so that the flow rate (mass flow rate), flow rate, and pressure of circulating water can be freely selected.

  The tank unit 2 includes a tank 16 that stores a liquid to be heated (water in this embodiment). The tank 16 is connected to one end of a delivery pipe 36 and a supply pipe 35 extending from the heat pump unit 1 side. The tank 16 is also connected to one end of the hot water supply pipe 38b and the water supply pipe 38a. A hot water supply port (not shown) is provided at the other end of the hot water supply pipe 38b. A water supply port (not shown) is provided at the other end of the water supply pipe 38a.

  The water supply pipe 38a is connected to a branch pipe 38c that branches from the water supply pipe 38a on the upstream side of the tank 16 and that joins the hot water supply pipe 38b at the tip thereof. The branch pipe 38 c is connected to the hot water supply pipe 38 b through the hot water / mixing valve 17. The hot water mixing valve 17 adjusts the amount of water flowing into the hot water supply pipe 38b via the water supply pipe 38a and the branch pipe 38c according to the degree of opening thereof, thereby providing a hot water supply port provided at the other end of the hot water supply pipe 38b (illustrated). (Omitted) Adjust the temperature of the hot water coming out.

  In the present embodiment, the liquid to be heated is once taken into the tank 16 and then supplied to the heat pump unit 1 via the supply pipe 35. However, the present invention is not limited to this. For example, the heat pump is directly supplied from a water supply port (water supply pipe). The heated liquid may be supplied to the unit 1. In the present embodiment, the liquid to be heated heated by the heat pump unit 1 is once taken into the tank 16 and then supplied from the hot water supply port via the hot water supply pipe 38b. You may make it supply the to-be-heated liquid heated with the heat pump part 1 directly from the hot water supply port. Furthermore, instead of supplying hot water in the tank 16, a direct water supply hot water supply system including a heat exchanger that heats tap water using the heat of the hot water in the tank 16 may be used.

  The control unit 50 includes a CPU, a ROM, a RAM, various interfaces, an electronic circuit, and the like, and comprehensively controls the heat pump water heater S according to the present embodiment according to a program stored therein. For example, as described above, the control unit 50 defrosts the evaporator 6 based on the temperature detected by the temperature sensor 10 (the outlet refrigerant temperature of the evaporator 6). Further, the control unit 50 determines the target discharge pressure of the compressor 3 and the compressor 3 according to the procedure described later, based on the temperature detected by the temperature sensors 9, 11, 12, 14, the pressure detected by the pressure sensor 8, and the like. The target discharge temperature is calculated.

  Next, the operation of the heat pump water heater S will be described. In the heat pump water heater S, when the boiling operation is performed with midnight power, the hot water in the tank 16 is almost used up. In this case, the tank 16 is filled with cold water (normal temperature water). Alternatively, hot water may remain at the top of the tank 16.

  Normally, the tank 16 is always full of water, and in this state, the heat pump water heater S performs a hot water storage operation process. The heat pump water heater S sends hot gas discharged from the started compressor 3 to the refrigerant heat transfer tube 2 a of the liquid refrigerant heat exchanger 4. The hot gas sent into the refrigerant heat transfer tube 2a is condensed by releasing heat into the water in the liquid heat transfer tube 2b. And the water in the liquid heat exchanger tube 2b is heated with hot gas. Next, the refrigerant sent out from the refrigerant heat transfer tube 2 a of the liquid refrigerant heat exchanger 4 is depressurized by the pressure reducing valve 5 (expansion valve) and then flows into the evaporator 6. When the refrigerant flowing into the evaporator 6 evaporates by the wind sent from the blower 7, it draws heat from the outside air. Thereafter, the refrigerant returns to the compressor 3 and is compressed again.

  On the other hand, the water filled in the tank 16 is sent into the liquid heat transfer pipe 2 b of the liquid refrigerant heat exchanger 4 from the bottom of the tank 16 through the supply pipe 35 when the pump 13 is activated. As described above, the water sent into the liquid heat transfer tube 2b is heated by heat exchange with the refrigerant to become hot water and flows into the delivery pipe 36. The hot water that has flowed into the delivery pipe 36 returns to the top of the tank 16 and is stored. Since the hot water returned to the top of the tank 16 has a low density, it does not mix with the cold water at the bottom of the tank 16 and accumulates in order from the top. Thus, while water circulates between the tank 16 and the liquid refrigerant heat exchanger 4, the heat pump water heater S secures a predetermined amount of hot water at a predetermined temperature in the tank 16.

  The control unit 50 of the heat pump water heater S controls the compressor 3, the pump 13, and the pressure reducing valve 5 as follows. The control unit 50 controls the rotation speed of the compressor 3 based on the temperature of the hot water at the outlet of the liquid refrigerant heat exchanger 4 detected by the temperature sensor 12. Specifically, the control unit 50 controls the rotation speed of the compressor 3 so that the temperature detected by the temperature sensor 12 becomes a preset target value of the tapping temperature. That is, when the detected value of the temperature sensor 12 is lower than the target value, the rotational speed of the compressor 3 is increased. Conversely, when the detected value is high, the rotational speed of the compressor 3 is decreased.

  Further, the control unit 50 controls the amount of water that the pump 13 sends to the liquid heat transfer pipe 2b of the liquid refrigerant heat exchanger 4 based on the target rotational speed of the compressor 3 that has been obtained in advance in order to control the heating capacity. To do. Specifically, when the actual rotational speed is slower than the target rotational speed of the compressor 3, the pump 13 is controlled so that the amount of water fed into the liquid heat transfer tube 2b is increased, and compression is performed in reverse. When the actual rotational speed of the machine 3 is fast, the pump 13 is controlled so that the amount of water fed into the liquid heat transfer tube 2b is reduced. Thereby, it is possible to adjust the heating capacity to a target value (for example, 4.5 kW).

  The target rotational speed of the compressor 3 described above is not only the target value of the tapping temperature of the liquid refrigerant heat exchanger 4 but also the target heating capacity (output) of the heat pump unit 1 and the detected value of the temperature sensor 14 (outside air temperature). ) And the detection value (incoming water temperature) of the temperature sensor 11 can also be set. Specifically, for example, as described above, the target rotational speed of the compressor 3 is set in a range of 3000 to 4000 revolutions / minute when performing high-temperature hot water storage (for example, 90 ° C.). In the case of operating at a temperature (for example, 65 ° C.), the speed is set in a range of 1000 to 2000 revolutions / minute, but is not limited thereto.

  The control unit 50 calculates the target discharge temperature of the compressor 3 and controls the opening of the pressure reducing valve 5 based on the difference between the discharge temperature of the compressor 3 detected by the temperature sensor 9 and the target discharge temperature. . That is, the control unit 50 controls the opening of the pressure reducing valve 5 so that the discharge temperature of the compressor 3 becomes a target value (target discharge temperature) calculated in advance by the control unit 50. Specifically, when the temperature detected by the temperature sensor 9 is higher than the target discharge temperature, the pressure reducing valve 5 is opened, and when the temperature is low, the pressure reducing valve 5 is adjusted to be closed. The target discharge temperature is determined by the control unit 50 in addition to the target value of the hot water temperature of the liquid refrigerant heat exchanger 4 described above, the target heating capacity (output) of the heat pump unit 1, the detected value (outside temperature) of the temperature sensor 14, It is also possible to calculate and set based on the detected value (incoming water temperature) of the temperature sensor 11. The target discharge temperature is set so that the heat pump unit 1 has the maximum coefficient of performance (COP), but is not limited thereto.

Next, the operation of the control unit 50 according to the present invention will be described.
FIG. 2 is a flowchart showing the procedure of the target discharge temperature correction process by the control unit 50. The control unit 50 corrects the target discharge temperature as shown in FIG. 2 so that the detection value of the pressure sensor 8 (discharge pressure of the compressor 3) becomes the target value (target discharge pressure).

  In the flowchart of FIG. 2, first, when the heat pump unit 1 is activated, the control unit 50 sets a correction value stored in a predetermined area of a memory such as a RAM to “0” (initial value) (step S <b> 1).

  Next, the control unit 50 calculates the target discharge temperature and the target discharge pressure by the normal method described above. Then, the control unit 50 adds the correction value to the calculated target discharge temperature and sets this as a new target discharge temperature (step S2). Here, when the heat pump unit 1 is activated, the initial correction value is “0” (see step S1).

  Subsequently, the control unit 50 controls the opening of the pressure reducing valve 5 (opening adjustment) so that the detection value of the temperature sensor 9 (discharge temperature of the compressor 3) becomes the target discharge temperature calculated in step S2. (Step S3). That is, the opening degree control of the pressure reducing valve 5 is performed based on the difference between the discharge temperature detected by the temperature sensor 9 and the target discharge temperature.

  Subsequently, the control unit 50 monitors whether or not a predetermined time has elapsed (step S4). In the present embodiment, the predetermined time is, for example, 60 seconds, but is not limited to this, and can be changed as appropriate. The predetermined time indicates a cycle for correcting the target discharge temperature. When it is determined that the predetermined time has not elapsed (step S4: No), the control unit 50 returns the process to step S3, and when it is determined that the predetermined time has elapsed (step S4: Yes), the process proceeds to step S5. Proceed to

  In step S5, the control unit 50 monitors the difference between the detection value of the pressure sensor 8 (discharge pressure of the compressor 3) and the target discharge pressure, and the value obtained by subtracting the detection value of the pressure sensor 8 from the target discharge pressure is determined in advance. It is determined whether or not the set deviation is larger than the set deviation. When the control unit 50 determines that the value obtained by subtracting the detected value of the pressure sensor 8 from the target discharge pressure is larger than the set deviation (step S5: Yes), the process proceeds to step S6, and the pressure sensor 8 is calculated from the target discharge pressure. If it is determined that the value obtained by subtracting the detected value is equal to or less than the set deviation (step S5: No), the process proceeds to step S8.

  In step S6, the control unit 50 determines whether the target discharge temperature is higher than a preset upper limit value of the target discharge temperature. When the control unit 50 determines that the target discharge temperature is higher than the preset upper limit value of the target discharge temperature (step S6: Yes), the control unit 50 returns the process to step S2 and sets the target discharge temperature at the preset target discharge temperature. When it is determined that the temperature is equal to or lower than the upper limit value of the temperature (step S6: No), the process proceeds to step S7.

  In step S7, the control unit 50 adds the amount of change α to the correction value stored in the predetermined area of the memory to obtain a new correction value, and returns the process to step S2.

  In step S8, the control unit 50 monitors the difference between the detection value of the pressure sensor 8 (discharge pressure of the compressor 3) and the target discharge pressure, and a value obtained by subtracting the target discharge pressure from the detection value of the pressure sensor 8 in advance. It is determined whether or not the set deviation is larger than the set deviation. When it is determined that the value obtained by subtracting the target discharge pressure from the detection value of the pressure sensor 8 is larger than the set deviation (step S8: Yes), the control unit 50 advances the process to step S9, and from the detection value of the pressure sensor 8 If it is determined that the value obtained by subtracting the target discharge pressure is equal to or less than the set deviation (step S8: No), the process returns to step S2.

  In step S9, the control unit 50 determines whether or not the target discharge temperature is lower than a preset lower limit value of the target discharge temperature. When the control unit 50 determines that the target discharge temperature is lower than the preset lower limit value of the target discharge temperature (step S9: Yes), the control unit 50 returns the process to step S2 and sets the target discharge temperature at which the target discharge temperature is set in advance. When it is determined that the temperature is equal to or higher than the lower limit value of the temperature (step S9: No), the process proceeds to step S10.

  In step S10, the control unit 50 subtracts the change amount α from the correction value stored in the predetermined area of the memory to obtain a new correction value, and returns the process to step S2.

  As described above, the control unit 50 calculates the target discharge pressure of the compressor 3 and corrects the target discharge temperature based on the difference between the discharge pressure of the compressor 3 detected by the pressure sensor 8 and the target discharge pressure. . That is, the control unit 50 corrects the target discharge temperature so that the discharge pressure of the compressor 3 becomes a target value (target discharge pressure) calculated in advance by the control unit 50. Specifically, when the value obtained by subtracting the detection value of the pressure sensor 8 from the target discharge pressure is larger than the set deviation, the target discharge temperature is corrected upward (steps S7 and S2), and the target discharge is detected from the detection value of the pressure sensor 8. When the value obtained by subtracting the pressure is larger than the set deviation, the target discharge temperature is corrected downward (steps S10 and S2).

  Here, if the difference between the detected value of the pressure sensor 8 and the target discharge pressure is within the set deviation (step S5: No and S8: No), the process of changing the correction value (steps S7, S10) is performed. Absent. This set deviation is determined according to the resolution of the pressure sensor 8 and may be a constant value such as 0.03 MPa. For example, the set deviation is determined (changed) using the outside air temperature, the incoming water temperature, the heating capacity, and the like. You can also

  Further, in the present embodiment, when the target discharge temperature is higher than the preset upper limit value or lower than the lower limit value (step S6: Yes or S9: Yes), a process of changing the correction value (step S7, S10) is not performed. The change amount α is a positive value, and is a constant value such as 0.5 ° C. here. However, the change amount α can be set, for example, between 0.1 ° C. and 1 ° C. according to the resolution of the temperature sensor, but is not limited thereto. Further, the amount of change α may be a constant value such as 0.5 ° C., but for example, the outside air temperature, the temperature of the heated liquid entering the liquid refrigerant heat exchanger 4 (incoming water temperature), and the rotation of the compressor 3 It may be determined (changed) using the speed.

  If No in step S8, after step S7 or after step S10, the process returns to step S2, the control unit 50 determines the target discharge temperature, proceeds to step S3, and discharges the compressor 3 at the discharge temperature. However, the opening degree of the pressure reducing valve 5 is controlled so as to be the target discharge temperature determined in step S2.

  In the heat pump water heater S according to the present embodiment, it is possible to perform an operation for stabilizing and maximizing the coefficient of performance (COP) without impairing the hot water temperature by repeating the operation as shown in FIG. It becomes.

  FIG. 3 is an example of a time chart for explaining the timing for correcting the target discharge temperature in the heat pump water heater S according to the present embodiment. In FIG. 3, the initial target discharge temperature of the compressor 3, the corrected target discharge temperature of the compressor 3, the discharge temperature of the compressor 3 (detected value of the temperature sensor 9), the target discharge pressure of the compressor 3, the compression The discharge pressure of the machine 3 (detected value of the pressure sensor 8) is shown. In FIG. 3, the horizontal axis represents the elapsed time from the start of the heat pump water heater S from the left side to the right side of the drawing, and the left vertical axis represents the pressure (discharge pressure) of the refrigerant discharged from the compressor 3. The right vertical axis indicates the temperature of the refrigerant discharged from the compressor 3 (discharge temperature).

  As shown in FIG. 3, when the heat pump water heater S is started, the compressor 3 is driven to increase the discharge pressure of the compressor 3 with time, and the discharge temperature of the compressor 3 also increases with time. At this time, the control unit 50 controls the opening of the pressure reducing valve 5 so that the discharge temperature of the compressor 3 (detected value of the temperature sensor 9) approaches the target value (target discharge temperature).

  At the time of starting the heat pump water heater S, the discharge pressure of the compressor 3 is lower than the set deviation with respect to the target discharge pressure calculated by the control unit 50 (step S5 in FIG. 2: Yes), so that control is performed. The unit 50 corrects the target discharge temperature upward (step S7 in FIG. 2, times t0 to t1 in FIG. 3).

  Next, when the discharge pressure of the compressor 3 rises and becomes higher than the set deviation with respect to the target discharge pressure (Step S8 in FIG. 2: Yes), the control unit 50 lowers the target discharge temperature. Correction is made (step S10 in FIG. 2, times t1 to t2 in FIG. 3).

  And the discharge pressure of the compressor 3 is maintained so that it may become a target discharge pressure by correction of the target discharge temperature by the control part 50 (after the time t2 of FIG. 3). FIG. 3 shows a case where the target discharge temperature is between a preset upper limit value and lower limit value.

As described above, in the heat pump water heater S according to this embodiment, the control unit 50 calculates the target discharge temperature of the compressor 3 and detects the discharge temperature and the target discharge temperature of the compressor 3 detected by the temperature sensor 9. And the opening degree of the pressure reducing valve 5 is controlled based on the difference between the discharge pressure of the compressor 3, the target discharge pressure of the compressor 3 is calculated and the difference between the discharge pressure of the compressor 3 detected by the pressure sensor 8 and the target discharge pressure is calculated. Correct the target discharge temperature.
Thus, in this embodiment, the opening degree control of the pressure reducing valve 5 is performed so that the discharge temperature of the compressor 3 becomes the target discharge temperature, and at the same time, the target is set so that the discharge pressure of the compressor 3 becomes the target discharge pressure. The discharge temperature is corrected.
Therefore, according to the present embodiment, it is possible to provide the heat pump water heater S that can stabilize the coefficient of performance without impairing the hot water temperature.

  Further, in this embodiment, the target discharge temperature is corrected at a predetermined cycle, and the change amount α of the target discharge temperature in the correction is set to a constant value, so that the coefficient of performance can be obtained without impairing the tapping temperature by simple control. Can be stabilized.

  In the heat pump water heater S, the change amount α of the target discharge temperature in the correction uses the outside air temperature, the temperature of the liquid to be heated entering the liquid refrigerant heat exchanger 4 (incoming water temperature), and the rotational speed of the compressor 3. It may be configured to be determined. If comprised in this way, the more efficient driving | operation which stabilizes a coefficient of performance can be performed, without impairing the tapping temperature.

  In this embodiment, when the target discharge temperature is lower than a preset lower limit value of the target discharge temperature, the control unit 50 does not perform downward correction of the target discharge temperature. If comprised in this way, target discharge temperature will not become low too much, and hot water temperature can be ensured more.

  In the present embodiment, when the target discharge temperature is higher than the preset upper limit value of the target discharge temperature, the control unit 50 does not correct the target discharge temperature upward. If comprised in this way, target discharge temperature will not become high too much, refrigeration cycle components, such as the compressor 3, can be protected from high temperature, and durability can be aimed at.

  As mentioned above, although this invention was demonstrated based on embodiment, this invention is not limited to above-described embodiment, Various modifications are included. For example, the above-described embodiment has been described in detail for easy understanding of the present invention, and is not necessarily limited to one having all the configurations described. Further, it is possible to add, delete, and replace other configurations for a part of the configuration of the embodiment.

  As the “heated liquid” of the present invention, tap water supplied from a water supply source via a water supply pipe has been described as an example, but the present invention is not limited to this example. As the “heated liquid” of the present invention, for example, well water may be employed. In addition to water, a liquid containing a latent heat storage material, brine, antifreeze liquid, or the like may be employed as the “heated liquid” in the present invention. That is, the term heat pump water heater is used in the present invention as a concept including the case where a liquid other than water is used as the liquid to be heated.

DESCRIPTION OF SYMBOLS 1 Heat pump part 2 Tank part 3 Compressor 4 Liquid refrigerant heat exchanger 5 Pressure reducing valve 6 Evaporator 7 Blower 8 Pressure sensor (pressure detection means)
9 Temperature sensor (temperature detection means)
50 Control part S Heat pump water heater α Change amount

Claims (5)

A compressor for compressing and discharging the sucked refrigerant;
A liquid refrigerant heat exchanger that performs heat exchange between the high-temperature and high-pressure refrigerant discharged from the compressor and the liquid to be heated;
A pressure reducing valve for depressurizing the refrigerant flowing out of the liquid refrigerant heat exchanger;
An evaporator for exchanging heat between the refrigerant flowing out of the pressure reducing valve and air;
Temperature detecting means for detecting the temperature of the refrigerant discharged from the compressor;
Pressure detecting means for detecting the pressure of the refrigerant discharged from the compressor;
A control unit that calculates a target discharge temperature of the compressor and performs opening degree control of the pressure reducing valve based on a difference between the discharge temperature detected by the temperature detection unit and the target discharge temperature;
With
The control unit calculates a target discharge pressure of the compressor and corrects the target discharge temperature based on a difference between the discharge pressure detected by the pressure detection unit and the target discharge pressure. Heat pump water heater.   The heat pump water heater according to claim 1, wherein the target discharge temperature is corrected at a predetermined cycle, and the amount of change in the target discharge temperature in the correction is a constant value.   The target discharge temperature is corrected in a predetermined cycle, and the amount of change in the target discharge temperature in the correction is the outside air temperature, the temperature of the heated liquid entering the liquid refrigerant heat exchanger, and the rotation speed of the compressor The heat pump water heater according to claim 1, wherein the heat pump water heater is determined using   The control unit does not perform downward correction of the target discharge temperature when the target discharge temperature is lower than a preset lower limit value of the target discharge temperature. The heat pump water heater according to one item.   The control unit does not perform upward correction of the target discharge temperature when the target discharge temperature is higher than a preset upper limit value of the target discharge temperature. The heat pump water heater according to one item.

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