JP2013160485A - Heat pump type liquid heating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat pump-type liquid heating device capable of being stably operated even when a discharge temperature of a compressor may reach a maximum allowable temperature.SOLUTION: In a heat pump type water heater as a heat pump type liquid heating device, a target discharge pressure of a compressor is lowered by a prescribed amount when a temperature of a refrigerant discharged from the compressor reaches a prescribed reference temperature or more. The heat pump type water heater controls opening/closing of a pressure reducing valve on the basis of the new target discharge pressure lowered by the prescribed amount.

Description

  The present invention relates to a heat pump type liquid heating apparatus, and more particularly to refrigeration cycle control of a heat pump type liquid heating apparatus.

  When refrigeration cycle control is performed in a heat pump type water heater as a heat pump type liquid heating device, the target discharge pressure of the refrigerant from the compressor, and the discharge pressure (actual discharge pressure) from the compressor actually detected from the refrigeration cycle Is known, and a pressure reducing device (pressure reducing valve) is controlled so that the actual discharge pressure coincides with the target discharge pressure (for example, refer to Patent Document 1 described later).

  In such a control method, control based on the discharge pressure of the compressor is performed, and control based on the discharge temperature of the refrigerant from the compressor is not performed. For this reason, the refrigerant discharge temperature from the compressor may reach a temperature (hereinafter referred to as “maximum allowable temperature”) that affects the durability of the components of the refrigeration cycle including the compressor. . In order to avoid this, conventionally, before the discharge temperature of the compressor reaches the maximum allowable temperature, for example, an emergency measure such as reducing the rotation speed (rotation speed) of the compressor or opening the decompression device is used. Control is being performed.

  When the discharge temperature of the compressor reaches the maximum allowable temperature, for example, when the evaporator performance decreases due to frost on the evaporator, and the difference between the suction pressure and discharge pressure of the compressor increases, This may occur when the liquid to be heated is delivered at a high temperature (for example, 90 ° C.) when the outside air temperature is low (for example, 2 ° C.). More specifically, under such conditions, the target discharge pressure of the compressor is set near the design upper limit of the discharge temperature in order to improve the COP (Coefficient of Performance) of the refrigeration cycle. As a result, the discharge temperature of the refrigerant from the compressor may reach the maximum allowable temperature due to output variations for each product and changes in environmental conditions.

Japanese Patent No. 4465986

  However, if the emergency measures such as reducing the rotation speed (rotational speed) of the compressor or opening the decompression device are performed as in the above-described prior art, the output of the refrigeration cycle is reduced, which is essential. There is a problem that the delivery temperature of the liquid to be heated is temporarily reduced. In the heat pump type hot water heater, control is performed so that the COP is the highest in the refrigeration cycle and the supply temperature of the liquid to be heated is constant. If this is done, the control of the refrigeration cycle is temporarily disrupted, so that there is a problem that an inefficient state in which the liquid to be heated is not stable continues for a certain period of time and it takes time to return to a stable state.

  An object of the present invention is to provide a heat pump type liquid heating apparatus that can be stably operated even when the discharge temperature of the compressor may reach the maximum allowable temperature.

  In order to solve the above-described problems and achieve the object, a heat pump type liquid heating device according to the present invention includes a compressor that compresses and discharges a sucked refrigerant, a refrigerant discharged from the compressor, and a liquid to be heated. A heat pump that includes: a heat exchanger that performs heat exchange; a pressure-reducing valve that depressurizes the refrigerant flowing out from the heat exchanger; and an evaporator that performs heat exchange between the refrigerant flowing out from the pressure-reducing valve and air. A liquid heating apparatus that sets a target discharge pressure of the compressor and controls opening and closing of the pressure reducing valve based on the target discharge pressure; and a temperature of the refrigerant discharged from the compressor, or Temperature detection means for detecting the temperature of the compressor, and the control means is configured to detect the target discharge pressure when the detected temperature detected by the temperature detection means is equal to or higher than a predetermined reference temperature. And wherein the reducing a predetermined amount.

  According to the heat pump type liquid heating device according to the present invention, even when there is a possibility that the discharge temperature of the compressor may reach the maximum allowable temperature, the operation can be stably performed.

It is composition explanatory drawing of the heat pump type hot water supply machine concerning one Embodiment of this invention. It is a flowchart which shows the procedure of the control processing of the compressor discharge pressure by a control part. It is a time chart which shows the timing which reduces target discharge pressure in a heat pump type hot water heater.

  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 type water heater that is a heat pump type liquid heating apparatus using water as a liquid to be heated will be described as an example. In the heat pump type hot water supply apparatus according to the present embodiment, when the control unit (control unit) controls the refrigerant discharge pressure (compressor discharge pressure) to the high pressure side of the compressor to be the target value (target discharge pressure). Protect the compressor when the refrigerant discharge temperature (compressor discharge temperature) to the high pressure side of the compressor approaches the temperature (maximum allowable temperature) that impairs the durability of the components of the refrigeration cycle, including the compressor Therefore, before the pressure reducing valve is opened or the rotation speed of the compressor is decreased, control is performed to decrease the target discharge pressure. Below, after demonstrated the whole structure of the heat pump type water heater concerning this embodiment, and basic operation of a control part, operation of a control part concerning the present invention is explained still more concretely.

  FIG. 1 is a configuration explanatory diagram of a heat pump type water heater 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 discharged 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 rotational speed (for example, 3000 to 4000 rotations / minute) faster 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.

  A temperature sensor for detecting the temperature of the refrigerant discharged from the compressor 3 (compressor discharge temperature) on the compressor 3 side in a pipe connecting the compressor 3 and the liquid refrigerant heat exchanger 4 described below. 9 and a pressure sensor 8 for detecting the pressure of the refrigerant discharged from the compressor 3 (compressor discharge pressure). Instead of the temperature sensor 9 or together with the temperature sensor 9, a temperature sensor for detecting the temperature of the components of the compressor 3 may be provided. The component of the compressor 3 is a coil in the compressor 3, for example.

  The liquid refrigerant heat exchanger 4 (heat exchanger) functions as a condenser, and a refrigerant heat transfer tube 2a through which hot gas discharged from the compressor 3 circulates and a liquid through which water to be heated is circulated. And a heat transfer tube 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 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 pressure (compressor discharge pressure) of the compressor 3 by changing the throttle 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 rotation of the blower 7 and pumps heat from outside air by exchanging heat between the refrigerant circulating in the evaporator 6 and 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 fully opens the pressure reducing valve 5 when performing defrosting. 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 upper part of the tank 16. Near the liquid refrigerant heat exchanger 4 of the delivery pipe 36, a temperature sensor 12 is provided that detects the temperature of the liquid to be heated that exits from the liquid refrigerant heat exchanger 4 (the water discharge temperature in the present embodiment).

  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. On the liquid refrigerant heat exchanger 4 side 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. As will be described later, the control unit 50 determines the target value of the compressor discharge pressure using the detected value of the temperature sensor 11 as one of the reference elements.

  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). (Omission) 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. Further, 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, it may be water direct pressure hot water provided with a heat exchanger that heats tap water using the heat of the hot water in the tank 16.

  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 type water heater S according to the present embodiment in accordance with a program stored therein. To do. 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). In addition, 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, and 14, the pressure detected by the pressure sensor 8, and the like. The target discharge temperature is calculated, and the rotational speed of the compressor 3 and the opening of the pressure reducing valve 5 are controlled based on the detected value (actually measured value) and the target value.

  Next, the operation of the heat pump type water heater S will be described. In the heat pump water heater S, when the boiling operation is performed at midnight power, the hot water in the tank 16 is almost used up, and 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 type hot water heater S performs a hot water storage operation process. The heat pump type water heater S sends hot gas discharged from the started compressor 3 into 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. The refrigerant flowing into the evaporator 6 pumps up heat from the outside air via the liquid refrigerant heat exchanger 4 when evaporating with the wind sent from the blower 7. 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 hot water heater S secures a predetermined amount of hot water in the tank 16 at a predetermined temperature.

  The control unit 50 of the heat pump type hot water heater S controls the compressor 3, the pump 13, and the pressure reducing valve 5 as follows. The control unit 50 controls the rotational speed of the compressor 3 based on the outlet temperature 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 target value of the preset water discharge 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 tube 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, a heating capability can be adjusted to target value (for example, 4.5 kW).

  The target rotational speed of the compressor 3 described above includes the target value of the water temperature of the liquid refrigerant heat exchanger 4, 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.

  Further, the control unit 50 controls the opening and closing of the pressure reducing valve 5 so that the compressor discharge pressure becomes a target value calculated in advance by the control unit 50. Specifically, when the pressure detected by the pressure sensor 8 is higher than the target discharge pressure, the pressure reducing valve is opened, and when it is low, the pressure reducing valve is closed. In addition to the target value of the outlet temperature of the liquid refrigerant heat exchanger 4, the target discharge pressure is determined by the control unit 50, the target heating capacity (output) of the heat pump unit 1, the detection 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 pressure is set so that the COP of the heat pump unit 1 is maximized, but is not limited thereto.

  Next, the operation of the control unit 50 according to the present invention will be described. The controller 50 controls the target discharge pressure according to the procedure shown in FIG. In particular, as shown in steps S3 and S4 in FIG. 2, when the compressor discharge temperature reaches the reference temperature, the control unit 50 changes (reduces) the target discharge pressure, and the compressor discharge temperature reaches the maximum allowable temperature. Do not. Here, the reference temperature is a temperature higher than the target temperature of the liquid to be heated after heat exchange in the liquid refrigerant heat exchanger 4, and is, for example, a maximum allowable temperature (eg, 130 ° C.) for maintaining the product life of the compressor 3. 3) to 15 ° C. (for example, 120 ° C.), but is not limited thereto.

  FIG. 2 is a flowchart showing a procedure of control processing of the compressor discharge pressure by the control unit. In the flowchart of FIG. 2, first, when the heat pump unit 1 is activated, the control unit 50 calculates a target discharge pressure by a normal method (step S1). The target discharge pressure calculated in step S1 is hereinafter referred to as “normal target discharge pressure”. The control unit 50 controls opening and closing of the pressure reducing valve 5 so that the detected pressure of the pressure sensor 8 becomes the normal target discharge pressure (control based on the normal target discharge pressure) (step S2). That is, steps S1 and S2 are normal discharge pressure control processing. Next, the control unit 50 determines whether or not the output value (compressor discharge temperature) of the temperature sensor 9 is equal to or higher than the reference temperature (step S3). When the compressor discharge temperature is lower than the reference temperature (step S3: No), the control unit 50 returns to step S2 and continues the control based on the normal target discharge pressure.

  On the other hand, when the detected value (compressor discharge temperature) of the temperature sensor 9 is equal to or higher than the reference temperature (step S3: Yes), the control unit 50 calculates a new target discharge pressure (new target discharge pressure) and generates a new target discharge. While starting the control based on the pressure, the command rotational speed (rotational speed) of the blower 7 and the detected value (incoming water temperature) of the temperature sensor 11 at that time are stored (step S4). The new target discharge pressure is, for example, a value obtained by subtracting the predetermined value a from the normal target discharge pressure calculated in step S1. That is, the new target discharge pressure is lower than the normal target discharge pressure. The predetermined value a can be set to a predetermined constant value, for example. The predetermined value a is selected from the target heating capacity of the heat pump unit 1 (target temperature of hot water after heat exchange), the detected value of the temperature sensor 14 (outside air temperature), and the detected value of the temperature sensor 11 (incoming water temperature). The control unit 50 may calculate and set a value based on at least one.

  Further, the command rotational speed of the blower 7 and the detected value (incoming water temperature) of the temperature sensor 11 stored in step S4 are the command rotational speed of the blower 7 and the temperature sensor 11 when control based on the new target discharge pressure is started. , That is, the command rotational speed at the time when the reduction of the target discharge pressure is started, and the detected value (incoming water temperature) of the temperature sensor 11.

  Next, the control unit 50 compares the detected value (incoming water temperature) of the current temperature sensor 11 with the detected value of the temperature sensor 11 stored in step S4, and determines whether or not there is a change over a predetermined temperature. Judgment is made (step S5). That is, in step S5, it is determined whether or not the detected value (incoming water temperature) of the temperature sensor 11 has changed by a predetermined temperature or more since the start of control based on the new target discharge pressure. At this time, as the amount of change in the detection value (predetermined temperature), for example, a value set in advance such as ± 5 ° C. or more from the value stored in step S4 may be used. Further, the amount of change in the detected value of the temperature sensor 11 may be different between the rising side and the descending side, such as “+ 7 ° C. or higher or −5 ° C. or higher”. If the detected value has changed by a predetermined temperature or more (step S5: Yes), the control unit 50 proceeds to step S11 to restore the decrease in the target discharge pressure to the normal target discharge pressure (step S11). ), Returning to step S2, the opening / closing control of the pressure reducing valve 5 is performed based on the normal target discharge pressure.

  On the other hand, if the detected value of the temperature sensor 11 does not change more than the predetermined temperature in step S5 (step S5: No), the controller 50 has the command rotational speed of the blower 7 changed from the value stored in step S4? It is determined whether or not (step S6), the operation stop of the heat pump unit 1 is instructed (step S7), and whether or not the defrost operation is performed in the heat pump unit 1 (step S8). When the command rotational speed of the blower 7 changes from the value stored in step S4 (step S6: Yes), or when the operation stop of the heat pump unit 1 is instructed (step S7: Yes), or the heat pump unit 1 performs the defrost operation. (Step S8: Yes), the control unit 50 proceeds to step S11, returns the reduced amount of the target discharge pressure to the normal target discharge pressure (step S11), returns to step S2, and returns to normal. The pressure reducing valve 5 is controlled to open and close based on the target discharge pressure.

  Here, steps S <b> 5 to S <b> 8 are for determining whether or not there has been a change in the operating conditions of the refrigeration cycle of the heat pump unit 1. If the operating conditions of the refrigeration cycle change, the compressor discharge temperature may decrease without lowering the target discharge pressure, but the current decrease in target discharge pressure causes extreme changes in the refrigeration cycle COP. There is a possibility of lowering. For this reason, the control unit 50 cancels the decrease in the target discharge pressure when the operating condition of the refrigeration cycle of the heat pump unit 1 is changed, and reduces the pressure based on the normal target discharge pressure (original target discharge pressure). The valve 5 is controlled to open and close.

  On the other hand, the command rotational speed of the blower 7 is not changed from the value stored in step S4 (step S6: No), the operation stop of the heat pump unit 1 is not instructed (step S7: No), and the heat pump unit 1 is defrosted. When the operation is not performed (step S8: No), the control unit 50 continues the control based on the new target discharge pressure and determines whether the output value (compressor discharge temperature) of the temperature sensor 9 is equal to or higher than the reference temperature. Is determined (step S9). This reference temperature is the same as the temperature used for the determination in step S3.

  When the detected value (compressor discharge temperature) of the temperature sensor 9 is equal to or higher than the reference temperature (step S9: Yes), the control unit 50 has passed a predetermined time, for example, 180 seconds from the calculation of the new target discharge pressure (step S4). Whether or not (step S10). The control unit 50 returns to step S5 and continues the subsequent processes until a predetermined time has elapsed from the calculation of the new target discharge pressure (step S10: No).

  When a predetermined time has elapsed from the calculation of the new target discharge pressure (step S10: Yes), the control unit 50 returns to step S4 and calculates a new target discharge pressure. That is, if the compressor discharge temperature is equal to or higher than the reference temperature even after a predetermined time has elapsed from the calculation of the new target discharge pressure, the control unit 50 assumes that the target discharge pressure has been insufficiently reduced. Reduce pressure further.

  In addition, the predetermined time in step S10, that is, the increase period of the amount of decrease in the target discharge pressure can be set to a predetermined value (for example, 180 seconds), for example. The predetermined time in step S10 is, for example, the target heating capacity of the heat pump unit 1 (target temperature of hot water after heat exchange), the detected value of the temperature sensor 14 (outside air temperature), and the detected value of the temperature sensor 11 (incoming water temperature). ) May be calculated and set by the control unit 50 based on at least one of them.

  On the other hand, when the detected value (compressor discharge temperature) of the temperature sensor 9 is lower than the reference temperature in step S9 (step S9: No), the control unit 50 returns to step S5 and continues the subsequent processing. This is because the compressor discharge temperature falls below the reference temperature by lowering the target discharge pressure, but if the target discharge pressure is immediately returned to the normal target discharge pressure, the compressor discharge temperature may exceed the reference temperature again. Because there is. In this case, the control unit 50 proceeds to step S11 when at least one of the conditions in steps S5 to S8 is satisfied, that is, when the operating condition of the refrigeration cycle has changed, and based on the decrease in the target discharge pressure. Return to the control based on the normal target discharge pressure.

  As described above, in the heat pump type hot water heater S according to the present embodiment, by repeating the operation as shown in FIG. 2, the sudden decrease in the hot water temperature of the heat pump unit 1 and the cycle operation become unstable. To prevent. If it is predicted that the operating condition of the refrigeration cycle will change and that the target discharge pressure will decrease, the CO of the refrigeration cycle will decrease. Based on this, the pressure reducing valve 5 is controlled.

  In addition, in the heat pump type hot water heater S according to the present embodiment, when the increase in the compressor discharge temperature cannot be suppressed even if the above-described operation is performed, the pressure reducing valve 5 is forcibly opened as in the related art. Alternatively, an operation such as reducing the rotational speed (rotational speed) of the compressor 3 is performed.

  FIG. 3 is a time chart showing the timing for lowering the target discharge pressure in the heat pump hot water heater S. FIG. 3 shows the target discharge pressure of the compressor 3, the detected value of the temperature sensor 9 (compressor discharge temperature), and the detected value of the temperature sensor 11 (incoming water temperature). In FIG. 3, the horizontal axis represents the elapsed time t from the start of the heat pump type hot water heater S from the left side to the right side of the page, the left vertical axis represents the target discharge pressure, and the right vertical axis represents the compressor discharge temperature and the incoming water temperature. ing.

  Moreover, time t1 has shown the time when the compressor discharge temperature rose and reached | attained predetermined predetermined reference temperature (S3: Yes of FIG. 2). t2 indicates the time when the compressor discharge temperature falls below the reference temperature (S9: No in FIG. 2). t3 indicates the time when the incoming water temperature rises by ΔTw compared to the stored value (detected value at time t2) (S5: Yes in FIG. 2). In other words, ΔTw represents the temperature difference between the detected value of the temperature sensor 11 at time t2 when the latest target discharge pressure is calculated and the detected value of the temperature sensor 11 at time t3.

  3 will be described in more detail. At time 0, the control unit 50 calculates the target discharge pressure Pa (normal target discharge pressure) (S1 in FIG. 2), and the detected pressure of the pressure sensor 8 is the target discharge pressure. Then, opening / closing control of the pressure reducing valve 5 is started (S2 in FIG. 2). Thereby, the detection value (compressor discharge pressure) of the pressure sensor 8 and the detection value (compressor discharge temperature) of the temperature sensor 9 rise with time (time 0 to t1). Next, at time t1, the detection value (compressor discharge temperature) of the temperature sensor 9 becomes a predetermined reference temperature due to a decrease in the detection value (outside temperature) of the temperature sensor 14 or frosting of the evaporator 6 or the like. To reach.

  When the detected value (compressor discharge temperature) of the temperature sensor 9 reaches a predetermined reference temperature (S3: Yes in FIG. 2), the control unit 50 subtracts a certain value from the target discharge pressure to obtain a new target discharge. The pressure Pb (Pb <Pa) is calculated, and based on this, the pressure reducing valve 5 is controlled to open and close. If the detected value (compressor discharge temperature) of the temperature sensor 9 is higher than the reference temperature even after the operation with a new target discharge pressure Pb for a predetermined time or longer (for example, 180 seconds or longer) (S9, S10 in FIG. 2: Yes) The part 50 calculates a new target discharge pressure Pc obtained by further subtracting a constant value from the target discharge pressure Pb, and based on this, opens and closes the pressure reducing valve 5 (S4 in FIG. 2). This operation is continued until the compressor discharge temperature becomes lower than the reference temperature (S9: No in FIG. 2) (time t1 to t2). The constant value is a value set in advance so as not to greatly affect the refrigeration cycle, and is specifically a value of about 0.03 to 0.1 MPa. Further, every time a new target discharge pressure is calculated, the control unit 50 stores the value (incoming water temperature) of the temperature sensor 11 at that time (S4 in FIG. 2).

  When the detected value (compressor discharge temperature) of the temperature sensor 9 becomes lower than a predetermined reference temperature (time t2, S9 in FIG. 2), the control unit 50 sets the new target discharge pressure. The calculation is stopped, and the opening and closing of the pressure reducing valve 5 is controlled using the latest target discharge pressure Pd calculated last. Thereafter, when the tank unit 2 is filled with hot water, the temperature of water supplied to the heat pump unit 1 (incoming water temperature) increases.

  The control unit 50 constantly compares the detected value (stored value) of the temperature sensor 11 at the time of calculating the newest target discharge pressure with the current detected value of the temperature sensor 11. That is, after time t2, the detected value (stored value) of temperature sensor 11 at time t2 is compared with the detected value of temperature sensor 11 at that time (S5 in FIG. 2). When the detected value of the current temperature sensor 11 increases by ΔTw with respect to the stored value (time t3, S5 in FIG. 2: Yes), the control unit 50 cancels the decrease in the target discharge pressure (S11 in FIG. 2), and initially The pressure reducing valve 5 is controlled to open and close using the normal target discharge pressure Pa (S2 in FIG. 2). ΔTw is a preset value, and is the amount of change in the incoming water temperature at which the COP of the refrigeration cycle is expected to decrease due to a decrease in the target discharge pressure. In the present embodiment, ΔTw is set to 5 ° C., for example.

  The reason why the target discharge pressure is increasing immediately before time t3 is that, apart from the processing shown in FIG. 2, the target discharge pressure is set so as to have a positive correlation with the incoming water temperature. This is because the target discharge pressure is controlled so as to increase with the increase.

  As described above, according to the heat pump type hot water heater S according to the present embodiment, when there is a possibility that the discharge temperature of the compressor may reach the maximum allowable temperature, the rotation speed (rotation speed) of the compressor 3 is set. The target discharge pressure of the compressor 3 is reduced by a predetermined amount instead of performing emergency measure control such as reducing or reducing the pressure reducing valve 5 rapidly. Thereby, it is possible to operate stably without giving a sudden state change to the refrigeration cycle.

  Further, according to the heat pump type hot water heater S according to the present embodiment, the amount of decrease in the target discharge pressure is increased at every predetermined period, and the amount of decrease in the target discharge pressure while the compressor discharge temperature is equal to or higher than the reference temperature. Therefore, even when the target discharge pressure decrease rate is insufficient, the target discharge pressure can be further reduced to prevent the compressor discharge temperature from reaching the maximum allowable temperature.

  Moreover, according to the heat pump type hot water heater S according to the present embodiment, when the operating condition of the refrigeration cycle in the own apparatus has changed, the decrease in the target discharge pressure is cancelled. This is because if there is a change in the operating conditions of the refrigeration cycle, the compressor discharge temperature may decrease without reducing the target discharge pressure. This is because COP may be extremely reduced. In the heat pump hot water heater S, when the operating condition of the refrigeration cycle is changed, the decrease in the target discharge pressure is canceled, so that the cop of the refrigeration cycle can be prevented from extremely decreasing.

  In the present embodiment, the target discharge pressure is controlled using the refrigerant discharge temperature (detected value of the temperature sensor 9) from the compressor 3, but instead of the temperature sensor 9 or together with the temperature sensor 9, When a temperature sensor that detects the temperature of the component parts of the compressor 3 is provided, the target discharge pressure may be controlled using the temperature of the component parts of the compressor 3 (compressor temperature). In this case, “compressor discharge temperature” in the above description may be read as “compressor temperature”.

  Moreover, although the tap water supplied via the water supply pipe from the water supply source was described as an example of the “heated liquid” of the present invention, 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.

DESCRIPTION OF SYMBOLS 1 Heat pump part 2 Tank part 3 Compressor 4 Liquid refrigerant heat exchanger (heat exchanger)
5 Pressure reducing valve 6 Evaporator 7 Blower 8 Pressure sensor 9 Temperature sensor (temperature detection means)
10, 11, 12, 14 Temperature sensor 50 Control unit (control means)
S Heat pump type water heater (heat pump type liquid heating device)

Claims (11)

A compressor that compresses and discharges the sucked refrigerant, a heat exchanger that performs heat exchange between the refrigerant discharged from the compressor and the liquid to be heated, and a pressure reducing valve that depressurizes the refrigerant flowing out of the heat exchanger And an evaporator that performs heat exchange between the refrigerant flowing out of the pressure reducing valve and air, and a heat pump type liquid heating device comprising:
Control means for setting a target discharge pressure of the compressor and performing opening / closing control of the pressure reducing valve based on the target discharge pressure;
Temperature detecting means for detecting the temperature of the refrigerant discharged from the compressor or the temperature of the compressor, and
The heat pump type liquid heating apparatus, wherein the control means reduces the target discharge pressure by a predetermined amount when the detected temperature detected by the temperature detection means is equal to or higher than a predetermined reference temperature.   The control unit increases the decrease amount of the target discharge pressure every predetermined period and continues increasing the decrease amount while the detected temperature is equal to or higher than the reference temperature. The heat pump type liquid heating apparatus described in 1.   The control means determines at least one of the decrease amount or the increase period of the decrease amount of the target discharge pressure, the outside air temperature around the heat pump type liquid heating device, the temperature of the heated liquid flowing into the heat exchanger The heat pump type liquid heating apparatus according to claim 2, wherein the heat pump type liquid heating apparatus is determined based on at least one of the target temperatures of the heated liquid after heat exchange in the heat exchanger.   3. The heat pump type liquid heating apparatus according to claim 2, wherein the control unit sets at least one of the decrease amount of the target discharge pressure or an increase cycle of the decrease amount to a predetermined constant value. 4. .   The control means reduces the target discharge pressure when there is a change in operating conditions of a refrigeration cycle constituted by the compressor, the heat exchanger, the pressure reducing valve, and the evaporator. The heat pump type liquid heating device according to any one of claims 1 to 4, wherein the heat pump type liquid heating device is released.   The control means obtains temperature information of the heated liquid flowing into the heat exchanger, and when the temperature of the heated liquid changes more than a predetermined temperature from the time when the target discharge pressure starts to decrease, 6. The heat pump type liquid heating apparatus according to claim 5, wherein a decrease in the target discharge pressure is released.   The said control means cancels the fall of the said target discharge pressure, when performing the defrost operation which opens the said pressure reducing valve in order to melt the frost attached to the said evaporator. The heat pump type liquid heating apparatus described.   The heat pump according to any one of claims 5 to 7, wherein when the operation stop of the heat pump liquid heating device is instructed, the control means cancels a decrease in the target discharge pressure of the compressor. Liquid heating device. The evaporator is provided with a blower,
The control unit acquires rotation speed command value information of the blower, and cancels the decrease in the target discharge pressure when the rotation speed command value changes from the time when the decrease in the target discharge pressure is started. The heat pump type liquid heating apparatus according to any one of claims 5 to 8. A target temperature is set for the heated liquid after the heat exchange in the heat exchanger,
The heat pump type liquid heating apparatus according to claim 1, wherein the reference temperature is higher than the target temperature.   The supercritical vapor compression refrigeration cycle in which carbon dioxide is used as the refrigerant and the discharge pressure of the refrigerant by the compressor is equal to or higher than the critical pressure of the refrigerant is used. The heat pump type liquid heating apparatus according to one.

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