JP2006234375A - Heat pump type water heater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a supply water in a water coolant heat exchanger from being boiled up, in a defrosting operation of an evaporator in a heat pump type water heater. <P>SOLUTION: In this heat pump type water heater, a water pump 13 for circulating the supply water in a storage tank 10 to the water coolant heat exchanger 15 is stopped in the defrosting operation of the evaporator 17, and the evaporator 17 is defrosted under the condition where the medium flows in order of a compressor 14, the water coolant heat exchanger 15, a pressure reducing device 16 and the evaporator 17, by opening a passage opening of the pressure reducing device 16 up to a prescribed opening or more. In the heat pump type water heater, at least one of control for increasing the passage opening of the pressure reducing device 16 and control for reducing a rotation speed of the compressor 14 is executed to bring a delivery coolant temperature of the compressor 14 within a prescribed temperature or less capable of preventing the supply water in the water coolant heat exchanger 15 from being boiled up, in the defrosting operation of the evaporator 17. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a defrosting control of an evaporator in a heat pump type water heater.

  Conventionally, in Patent Document 1, heat is absorbed from the atmosphere by an evaporator provided on the low pressure side of the heat pump cycle, while hot water is heated by a water-refrigerant heat exchanger provided on the high pressure side of the heat pump cycle. In the heat pump water heater that circulates the water to the hot water storage tank by the electric water pump, during the defrosting operation of the evaporator, the operation of the electric water pump is stopped to suppress the heat radiation of the high-pressure refrigerant in the water refrigerant heat exchanger, and In addition, it is described that the temperature of the refrigerant flowing into the evaporator is increased to increase the temperature of the refrigerant flowing into the evaporator by increasing the valve opening degree of the decompression device as compared with that during normal operation.

As a result, even during the defrosting operation of the evaporator, the evaporator can be defrosted while the refrigerant flows in the order of compressor → water refrigerant heat exchanger → decompression device → evaporator. There is no need to set a special hot gas bypass passage.
Japanese Patent No. 3297657

  Incidentally, in the heat pump cycle of Patent Document 1, in order to improve the defrosting performance, it is necessary to increase the compressor input power (input power) during the defrosting operation. Here, the compressor input power is represented by the product of the enthalpy difference between the compressor suction refrigerant and the compressor discharge refrigerant and the refrigerant flow rate.

  Since the passage cross-sectional area (diameter) of the decompression means is substantially limited, an increase in compressor input power appears mainly as an increase in refrigerant enthalpy difference rather than an increase in refrigerant flow rate. As a result, when the compressor input power is increased during the defrosting operation, the compression ratio is increased, and the compressor discharge refrigerant temperature is significantly increased. As a result, there arises a problem that hot water staying in the water-refrigerant heat exchanger is boiled during the defrosting operation.

  In addition, in the heat pump cycle of patent document 1, although the example which does not provide the internal heat exchanger which performs heat exchange between the outlet side high pressure refrigerant | coolant of a water refrigerant | coolant heat exchanger and the low pressure refrigerant | coolant of a compressor suction side is disclosed. In the case where the internal heat exchanger is provided to improve the cycle efficiency (COP), similarly, the operation of the electric water pump is stopped during the defrosting operation so that the high-pressure refrigerant is dissipated in the water refrigerant heat exchanger. Suppress.

  For this reason, since the high pressure refrigerant (compressor discharge refrigerant) flows into the internal heat exchanger at a high temperature, the compressor suction refrigerant is excessively heated by the high temperature high pressure refrigerant. As a result, the compressor discharge refrigerant temperature rises to a higher temperature, causing a problem that hot water in the water refrigerant heat exchanger is more likely to boil.

  In view of the above points, an object of the present invention is to prevent hot water in a water-refrigerant heat exchanger from boiling during a defrosting operation of an evaporator in a heat pump hot water heater.

In order to achieve the above object, according to the first aspect of the present invention, the water pump (13) is arranged so that the refrigerant heat dissipation amount in the water refrigerant heat exchanger (15) is reduced during the defrosting operation of the evaporator (17). By controlling and increasing the passage opening of the decompression device (16, 160) to a predetermined opening or more, the compressor (14), the water refrigerant heat exchanger (15), the decompression device (16, 160), and evaporation In the heat pump water heater that performs defrosting of the evaporator (17) while the refrigerant flows in the order of the heater (17),
The depressurization device so that the refrigerant temperature discharged from the compressor (14) is within a predetermined temperature for preventing boiling of hot water in the water-refrigerant heat exchanger (15) during the defrosting operation of the evaporator (17). It is characterized in that at least one of the control for increasing the passage opening degree of (16, 160) and the control for decreasing the rotational speed of the compressor (14) is executed.

  According to this, since the refrigerant temperature discharged from the compressor (14) can be constantly monitored and controlled within a predetermined temperature during the defrosting operation of the evaporator (17), the boiling of hot water in the water-refrigerant heat exchanger (15) can be controlled. The phenomenon can be reliably prevented.

  Thus, since the boiling phenomenon of hot water supply can be reliably prevented, the compressor (14) can be operated by setting the discharge refrigerant temperature to the highest temperature that achieves both prevention of boiling. Thereby, the input power of the compressor (14) can be maximized from the start of the defrosting operation to shorten the defrosting time. This is because the defrosting performance is equal to the input power (compression work) of the compressor (14).

  As in the invention described in claim 2, in the heat pump type water heater according to claim 1, control for increasing the passage opening of the decompression device (16, 160) during the defrosting operation of the evaporator (17) and You may make it perform both the control which reduces the rotation speed of a compressor (14).

  As in the invention described in claim 3, in the heat pump type water heater according to claim 2, during the defrosting operation of the evaporator (17), the passage opening degree of the decompression device (16, 160) is set to the maximum opening degree. You may make it perform control which reduces the rotation speed of a compressor (14), after increasing.

In the invention according to claim 4, the compressor (14), the water refrigerant heat exchanger (15) for heating hot water stored in the hot water storage tank (10) with the refrigerant discharged from the compressor (14), The high-pressure refrigerant that has passed through the water-refrigerant heat exchanger (15) is decompressed, and the decompression device (16, 160) capable of electrically adjusting the passage opening, and the low-pressure refrigerant that has passed through the decompression device (16, 160) An evaporator (17) for evaporating water, and a water pump (13) for circulating hot water in the hot water storage tank (10) to the water refrigerant heat exchanger (15),
During the defrosting operation of the evaporator (17), the water pump (13) is controlled so that the refrigerant heat dissipation amount in the water refrigerant heat exchanger (15) is reduced, and the decompression device (16, 160) By increasing the passage opening to a predetermined opening or more, the refrigerant flows in the order of the compressor (14), the water-refrigerant heat exchanger (15), the pressure reducing device (16, 160), and the evaporator (17). In the heat pump water heater that performs defrosting of the evaporator (17) while flowing,
During the defrosting operation of the evaporator (17), the discharge refrigerant temperature of the compressor (14) is within a predetermined temperature for preventing boiling of hot water in the water refrigerant heat exchanger (15). The passage opening degree of the pressure reducing device (16, 160) and the rotational speed of the compressor (14) are set to predetermined values at the start of the defrosting operation.

  Thereby, the defrosting operation of the evaporator (17) can be reliably executed while preventing boiling of hot water.

According to a fifth aspect of the present invention, in the heat pump water heater according to any one of the first to fourth aspects, the pressure reducing device is a nozzle portion that depressurizes the high-pressure refrigerant that has passed through the water-refrigerant heat exchanger (15). (161), a refrigerant suction port (162) through which the refrigerant is sucked into the interior by the high-speed refrigerant flow ejected from the nozzle portion (161), and a high-speed refrigerant flow and the suction refrigerant from the refrigerant suction port (162) And an ejector (160) having a booster (164) for converting the velocity energy of the refrigerant flow mixed with pressure energy into pressure energy,
The ejector (160) is provided with a mechanism (165, 166) capable of electrically adjusting the passage opening degree of the nozzle portion (161).
The evaporator (17) is arranged in the passage (30) through which the refrigerant flows toward the refrigerant suction port (162).

  Thus, the present invention can be suitably implemented also in a so-called ejector cycle having a pressure reducing device constituted by the ejector (160).

  As in the sixth aspect of the invention, in the heat pump type hot water heater according to any one of the first to fifth aspects, the high-pressure refrigerant and the compressor (14) sucked after passing through the water refrigerant heat exchanger (15). An internal heat exchanger (19) for exchanging heat with the low-pressure refrigerant on the side may be provided.

  As described above, even with the internal heat exchanger (19), it is possible to reliably prevent boiling of hot water in the water-refrigerant heat exchanger (15) during the defrosting operation.

  In addition, the code | symbol in the bracket | parenthesis of each said means shows the correspondence with the specific means as described in embodiment mentioned later.

(First embodiment)
FIG. 1 is an overall configuration diagram of a heat pump water heater (hereinafter abbreviated as a water heater) according to a first embodiment. The water heater according to the present embodiment includes a hot water storage tank 10 that stores hot water, a heat pump cycle 11 for heating the hot water, and a water circulation passage 12 that can circulate hot water in the hot water tank 10. The water circulation passage 12 is provided with an electric water pump 13 for circulating hot water.

  And the heat pump cycle 11 is comprised by the closed circuit which connected the compressor 14, the water refrigerant | coolant heat exchanger 15, the expansion valve 16, the evaporator 17, the accumulator 18, and the internal heat exchanger 19 in order. In the present embodiment, CO2 having a high pressure equal to or higher than the critical pressure (supercritical state) is used as the refrigerant.

  The compressor 14 is an electric compressor driven by a built-in electric motor 14a, and compresses and discharges the suction refrigerant to a critical pressure or higher. The water refrigerant heat exchanger 15 heats hot water by exchanging heat between the refrigerant discharged from the compressor 14 (high-temperature and high-pressure refrigerant) and hot water in the water circulation passage 12.

  The water-refrigerant heat exchanger 15 has a water passage 15a through which hot water flows, and a refrigerant passage 15b through which compressor discharge refrigerant flows. The flow direction of hot water flowing through the water passage 15a and the flow direction of refrigerant flowing through the refrigerant passage 15b. Are configured to face each other.

  As shown by arrows in FIG. 1, the flowing direction of the hot water flows from the outlet 10 a at the lower part of the hot water storage tank 10 → the electric water pump 13 → the water passage 15 a of the water / refrigerant heat exchanger 15 → the inlet 10 b at the upper part of the hot water storage tank 10. .

  The refrigerant (CO2) flowing through the water-refrigerant heat exchanger 15 is not condensed because it is dissipated to the hot water in the supercritical state by being compressed to a critical pressure or higher by the compressor 14.

  The outlet of the refrigerant passage 15 b of the water refrigerant heat exchanger 15 is connected to the inlet side of the expansion valve 16 via the high-pressure side passage 19 a of the internal heat exchanger 19. The expansion valve 16 is a pressure reducing device that depressurizes the high-pressure refrigerant on the outlet side of the internal heat exchanger 19, and in this embodiment, an electric expansion valve that can electrically control the throttle opening (valve opening) of the refrigerant passage. Used. Specifically, the expansion valve 16 includes a valve body 16a that adjusts the throttle opening, and an electric actuator 16b such as a servo motor that variably controls the position of the valve body 16a.

  The evaporator 17 is an outdoor heat exchanger, which absorbs and evaporates the low-pressure refrigerant (gas-liquid two-phase refrigerant) decompressed by the expansion valve 16 from the outside air (outdoor air). Outside air is blown to the evaporator 17 by an electric outdoor fan 17a.

  The accumulator 18 is a gas-liquid separator that gas-liquid separates the refrigerant flowing out from the evaporator 17. The accumulator 18 sucks only the gas-phase refrigerant into the compressor 14 through the low-pressure side passage 19 b of the internal heat exchanger 19. Surplus refrigerant is stored as a liquid phase refrigerant.

  The internal heat exchanger 19 performs heat exchange between the high-pressure refrigerant flowing through the high-pressure side passage 19a and the low-pressure refrigerant flowing through the low-pressure side passage 19b, and raises the intake refrigerant temperature of the compressor 14. Thereby, the refrigerant discharge temperature of the compressor 14 is raised, the refrigerant enthalpy difference (heat radiation amount) between the inlet and outlet of the water refrigerant heat exchanger 15 is increased, and the cycle efficiency (COP) is improved.

  FIG. 2 is a block diagram of the electric control of the present embodiment, and the control device 20 is constituted by a microcomputer and its peripheral circuits and the like, and is an electric device of a hot water heater, that is, an electric water pump 13 and an electric motor 14a of the compressor 14. The operation of the actuator 16b of the electric expansion valve 16 and the electric outdoor fan 17a is controlled.

  On the input side of the control device 20, there are a temperature sensor 21 that detects the refrigerant temperature discharged from the compressor 14, a pressure sensor 22 that detects the outlet refrigerant pressure (high pressure) of the water refrigerant heat exchanger 15, and an outlet refrigerant of the evaporator 17. Of the temperature sensor 23 for detecting the temperature, the temperature sensor 24 for detecting the temperature of the hot water at the inlet side of the water passage 15a of the water refrigerant heat exchanger 15, and the temperature sensor 25 for detecting the outside air temperature. A detection signal is input.

In addition, from the operation panel 26 of the water heater, an operation signal for operating and stopping the water heater, a hot water supply temperature setting signal for the water heater, and the like are input to the control device 20. Next, the operation of this embodiment will be described. FIG. 3 shows a control routine executed by the microcomputer of the control device 20, which starts with an operation signal of the water heater input from the operation panel 26. First, it is determined whether or not a defrosting operation is necessary. Specifically, it is determined whether the outlet refrigerant temperature of the evaporator 17 detected by the temperature sensor 23 is lower than a predetermined temperature T1 (S10). Here, the predetermined temperature T1 is, for example, −14 ° C., and when the outlet refrigerant temperature of the evaporator 17 is higher than the predetermined temperature T1, it can be determined that the defrosting operation is not necessary, and thus the normal operation is controlled (S20). ).

  FIG. 4 is a flowchart showing an outline of this normal operation control. First, the electric water pump 13 in the water circulation passage 12 is operated, and the compressor 14 is operated at a predetermined rotational speed determined by control characteristics during normal operation ( S210). Next, the target high pressure of the heat pump cycle 11 is calculated based on the outside air temperature detected by the temperature sensor 25, the inlet side hot water temperature of the water-refrigerant heat exchanger 15 detected by the temperature sensor 24, and the target boiling temperature. (S220). Here, the target boiling temperature is a temperature calculated based on the hot water setting temperature set by the user, the hot water temperature in the hot water storage tank 10, or the like.

  Next, it is determined whether the actual high pressure detected by the pressure sensor 22 is higher than the calculated target high pressure (S230). When the actual high pressure is high, the opening degree of the electric expansion valve 16 is increased by a predetermined amount (S240). Thereby, a high pressure falls.

  On the other hand, when the actual high pressure is lower than the calculated target high pressure, the opening degree of the electric expansion valve 16 is decreased by a predetermined amount (S250). As a result, the high pressure increases. In this way, the actual high pressure can be maintained near the target high pressure by performing control to increase or decrease the opening of the electric expansion valve 16 in accordance with the change in the actual high pressure.

  In FIG. 4, the specific rotation speed control of the compressor 14 is not shown, but the compressor 14 is used to avoid abnormal operation of the heat pump cycle 11 (for example, abnormally high pressure rise, abnormal discharge temperature rise, etc.). The rotation speed is automatically controlled.

  During normal operation, hot water is circulated through the water circulation passage 12 by the operation of the electric water pump 13, and the low temperature hot water in the lower part of the hot water storage tank 10 is circulated to the water refrigerant heat exchanger 15 to be heated. During normal operation, the actual high pressure can be maintained near the target high pressure by increasing or decreasing the opening of the electric expansion valve 16, and the high-pressure refrigerant temperature can be controlled to a temperature required to obtain hot water at a predetermined temperature.

  The solid line in FIG. 5 is a Mollier diagram during normal operation, where point A is the discharge portion of the compressor 14, point B is the outlet of the water-refrigerant heat exchanger 15, and point C is the high-pressure side passage of the internal heat exchanger 19. The outlet part (inlet part of the electric expansion valve 16), the point D is the outlet part of the electric expansion valve 16, and the point E is the position on the saturated gas line formed inside the accumulator 18. Point F is a low-pressure side passage outlet of the internal heat exchanger 19 (suction part of the compressor 14).

  On the other hand, when the outlet refrigerant temperature of the evaporator 17 is lower than the predetermined temperature T1 (−14 ° C.), that is, when the defrosting operation is necessary, the determination in step S20 is YES, and the defrosting operation is started in step S30. . Specifically, the operation of the electric water pump 13 is stopped, the opening degree of the electric expansion valve 16 is set to a predetermined opening degree during the defrosting operation, and the compressor 14 is set at a predetermined rotation speed during the defrosting operation. Operate.

  Here, the predetermined opening during the defrosting operation of the electric expansion valve 16 is a value larger than the opening during the normal operation under the same conditions (same high pressure value). Moreover, the predetermined rotation speed at the time of defrosting operation of the compressor 14 is also a value larger than the predetermined rotation speed at the time of normal operation in step S210 of FIG.

  Thus, by operating the heat pump cycle 11 with the operation of the electric water pump 13 stopped, the high-temperature discharged refrigerant of the compressor 14 can be hardly suppressed from radiating heat to the hot water supply side in the water-refrigerant heat exchanger 15. . And the fall of the refrigerant temperature by the pressure reduction in the electric expansion valve 16 can be suppressed by the opening degree increase of the electric expansion valve 16.

  As a result, it is possible to suppress the temperature drop of the refrigerant discharged from the compressor 14 and allow the high-temperature refrigerant to flow into the evaporator 17, so that the evaporator 17 can be defrosted. Here, the broken line in FIG. 5 is a Mollier diagram during the defrosting operation, and the A ′ point is the state of the refrigerant from the discharge part of the compressor 14 to the inlet part of the electric expansion valve 16. Point D ′ is the outlet of the electric expansion valve 16, and point E is the position on the saturated gas line formed inside the accumulator 18.

  The defrosting performance can be improved by increasing the compression work of the compressor 14 by increasing the predetermined number of rotations during the defrosting operation of the compressor 14 than during the normal operation.

  By the way, as described above, an increase in the rotational speed of the compressor 14, that is, an increase in the compressor input power, increases the compression ratio and causes a significant increase in the compressor discharge refrigerant temperature. Thereby, the malfunction that the hot-water supply water staying in the water-refrigerant heat exchanger 15 boils off at the time of a defrost operation arises.

  Further, in the heat pump cycle 11 of the present embodiment, since the internal heat exchanger 19 is provided, the high-pressure refrigerant (compressor discharge refrigerant) flows into the internal heat exchanger 19 at a high temperature, and the compressor suction refrigerant is excessive. Since it is heated, the compressor discharge refrigerant temperature rises to a higher temperature, and hot water in the water-refrigerant heat exchanger is more likely to boil.

  Thus, in the present embodiment, cycle control is used to reliably suppress the compressor discharge refrigerant temperature during the defrosting operation to a temperature range in which boiling of the hot water supply can be prevented.

  That is, after the defrosting operation is started in step S30 of FIG. 3, the compressor discharge refrigerant temperature (detected temperature of the temperature sensor 21) is a predetermined temperature T2 for preventing boiling of hot water (specifically, in step S40). Is lower than 90 ° C.). When this determination is NO, control is performed to increase the opening of the electric expansion valve 16 in step S50. .

  The opening degree increase control of the electric expansion valve 16 will be described based on the control characteristic diagram during the defrosting operation shown in FIG. 6A. The vertical axis in FIG. The arrows on the vertical axis indicate the direction in which the electric expansion valve 16 increases. “Full open” is the fully open position of the electric expansion valve 16, and “minimum opening” is a minute opening position in the vicinity of the fully closed of the electric expansion valve 16. 6A is a temperature difference between the actual compressor discharge refrigerant temperature (detected temperature of the temperature sensor 21) and the predetermined temperature T2.

  6A, the region on the right side of the vertical axis is a region where the actual compressor discharge refrigerant temperature is higher than the predetermined temperature T2, and the opening degree of the electric expansion valve 16 is increased according to the increase of ΔT. Increased characteristics. On the other hand, in the horizontal axis of FIG. 6A, the region on the left side of the vertical axis is a region where the actual compressor discharge refrigerant temperature is lower than the predetermined temperature T2 (a minus region of ΔT), and a minus amount of ΔT. The opening degree of the electric expansion valve 16 is reduced in accordance with the increase of.

  In addition, the predetermined opening degree at the time of the start of defrosting of the electric expansion valve 16 in step S30 is intermediate opening degree (theta) 1 of Fig.6 (a). Accordingly, in step S50, the opening degree of the electric expansion valve 16 is increased from the intermediate opening degree θ1 by a predetermined amount according to the increasing rate of the temperature difference ΔT.

  Here, the opening degree of the electric expansion valve 16 is kept constant for a predetermined time of about several seconds, the temperature difference ΔT is determined every predetermined time, and the opening degree of the electric expansion valve 16 is adjusted to the opening degree corresponding to the temperature difference ΔT. Control the opening.

  In step S60, it is determined whether the opening degree of the electric expansion valve 16 is the maximum opening degree. Since the determination in step S60 is NO until the opening degree of the electric expansion valve 16 reaches the maximum opening degree, the electric expansion valve 16 is determined. The above opening degree control is continued.

  Then, when the opening degree of the electric expansion valve 16 reaches the maximum opening degree, the process proceeds to step S <b> 70, and control is performed to reduce the rotational speed of the compressor 14. That is, FIG. 6B is a rotational speed control characteristic diagram of the compressor 14 during the defrosting operation, the vertical axis of FIG. 6B is the rotational speed of the compressor 14, and the vertical axis arrow indicates compression. The speed increasing direction of the machine 14 is shown.

  6B, the region on the right side of the vertical axis is a region where the actual compressor discharge refrigerant temperature is higher than the predetermined temperature T2, and the rotational speed of the compressor 14 is reduced as ΔT increases. It is a characteristic to make it. On the other hand, in the horizontal axis of FIG. 6B, the region on the left side of the vertical axis is a region where the actual compressor discharge refrigerant temperature is lower than the predetermined temperature T2 (a minus region of ΔT), and a minus amount of ΔT. The number of revolutions of the compressor 14 is increased in accordance with the increase in the value.

  In addition, the predetermined rotation speed at the time of the start of defrosting of the compressor 14 in step S30 is the intermediate rotation speed N1 of FIG.6 (b). Therefore, in step S70, the rotational speed of the compressor 14 is decreased from the intermediate rotational speed N1 by a predetermined amount in accordance with the increase in ΔT.

  Also in step S70, the rotational speed of the compressor 14 is kept constant for a predetermined time of about several seconds, the temperature difference ΔT is determined every predetermined time, and the opening of the compressor 14 is set to an opening degree corresponding to the temperature difference ΔT. Control the number of revolutions.

  By the way, if the opening degree of the electric expansion valve 16 is increased, the difference between the high and low pressures of the heat pump cycle 11 is reduced and the compression ratio is lowered, so that the compressor discharge refrigerant temperature can be lowered. Even when the electric expansion valve 16 is fully opened, when the compressor discharge refrigerant temperature is higher than the predetermined temperature T2, the rotation speed of the compressor 14 is decreased to reduce the compression ratio, thereby reducing the compressor discharge refrigerant temperature. Can be reduced.

  By executing the opening degree control of the electric expansion valve 16 and the rotation speed control of the compressor 14, the upper limit of the compressor discharge refrigerant temperature can be surely suppressed in the vicinity of the predetermined temperature T2 (90 ° C.). As a result, boiling of hot water remaining in the water / refrigerant heat exchanger 15 during the defrosting operation can be reliably prevented.

  On the other hand, when the determination in step S40 is YES, it is a time when there is no fear of boiling of the hot water supply, and thus the process proceeds to step S80 to determine whether the outlet refrigerant temperature of the evaporator 17 is higher than the defrosting end temperature T3. The defrosting end temperature T3 is a temperature (T1 + α) higher than the predetermined temperature T1 at which defrosting is started by a constant temperature α, and is 5 ° C., for example.

  While the determination in step S80 is NO, the defrosting operation in step S30 is continued. And if the exit refrigerant | coolant temperature of the evaporator 17 becomes higher than defrost end temperature T3, it will progress to step S90, will complete | finish defrost operation, and will transfer to normal operation control. This normal operation control is the same as the normal operation control in step S20.

  In the first embodiment, the start and end of the defrosting operation are performed based on the outlet refrigerant temperature of the evaporator 17, but the control of the start and end of the defrosting operation can be variously modified. For example, a temperature difference between the outside air temperature and the outlet refrigerant temperature of the evaporator 17 is calculated, and the defrosting operation is started when the temperature difference becomes larger than a first predetermined value (for example, 10 ° C.). The defrosting operation may be terminated when becomes less than or equal to a second predetermined value smaller than the first predetermined value.

  Here, instead of the evaporator outlet refrigerant temperature, the evaporator inlet refrigerant temperature may be used to start and end the defrosting operation based on the temperature difference between the outside air temperature and the evaporator inlet refrigerant temperature.

  Further, in each of the above control examples, the defrosting operation may be terminated by a timer signal instead of various temperature signals. That is, when the elapsed time of the defrosting operation reaches a predetermined set time, the defrosting operation may be terminated.

  Further, the defrosting operation is started when the elapsed time of the normal operation when the outside air temperature is 0 ° C. or less becomes longer than a predetermined time (for example, 2 hours), and the elapsed time of the defrosting operation reaches a predetermined set time. Then, the defrosting operation may be terminated.

(Second Embodiment)
In the first embodiment, the decompression device for the heat pump cycle is configured by the electric expansion valve 16, but in the second embodiment, the decompression device for the heat pump cycle is configured by the ejector 160 as shown in FIG. The ejector cycle. Since this ejector cycle is known from Japanese Patent No. 3322263, the outline thereof will be described below.

  The ejector 160 is a decompression unit that decompresses the refrigerant, and also serves as a pump unit that sucks the refrigerant by the entrainment action of the refrigerant flow ejected at high speed. As shown in FIG. 8, the ejector 160 is provided with a nozzle portion 161 that isentropically decompressed and expanded with the high-pressure refrigerant that has passed through the high-pressure side passage 19 a of the internal heat exchanger 19. The refrigerant in the refrigerant suction port 162 is sucked into the ejector 160 by the refrigerant flow.

  A mixing unit 163 that mixes the high-speed jet refrigerant flow and the suction refrigerant from the refrigerant suction port 162 is formed on the downstream side of the nozzle unit 161, and a diffuser unit 164 that forms a boosting unit on the downstream side of the mixing unit 163. Is formed. The diffuser portion 164 is formed in a shape that gradually expands the passage area of the refrigerant, and functions to decelerate the refrigerant flow to increase the refrigerant pressure, that is, to convert the velocity energy of the refrigerant into pressure energy.

  Further, a variable needle 166 whose position is controlled by an electric actuator 165 is disposed in the nozzle portion 161, and the opening degree of the nozzle portion 161 can be electrically controlled by the position control of the variable needle 166.

  The refrigerant that has flowed out of the diffuser portion 164 of the ejector 160 flows into the accumulator 18, where the gas-liquid of the refrigerant is separated. Then, the gas-phase refrigerant in the upper part of the accumulator 18 passes through the low-pressure side passage 19 b of the internal heat exchanger 19 and is sucked into the compressor 14.

  On the other hand, the liquid refrigerant in the lower part of the accumulator 18 is led out to the branch passage 30. This branch passage 30 has an auxiliary pressure reducer 31 composed of a fixed throttle. The evaporator 17 is connected to the downstream side of the auxiliary pressure reducer 31, and the outlet side of the evaporator 17 is connected to the refrigerant suction port 162 of the ejector 160. ing.

  According to the ejector cycle of the second embodiment, the lowest pressure immediately after the pressure reduction by the nozzle part 161 can be applied to the evaporator 17 from the refrigerant suction port 162, while the diffuser part 164 is provided on the suction side of the compressor 14. The pressure after the pressure increase can be applied. That is, the suction pressure of the compressor 14 can be made higher than the evaporation pressure of the evaporator 17, and the driving power of the compressor 14 can be saved by that amount.

(Third embodiment)
In the first embodiment, as shown in S40 to S70 of FIG. 3, during the defrosting operation of the evaporator 17, the opening degree of the electric expansion valve 16 and the rotation speed of the compressor 14 are feedback-controlled according to the compressor discharge refrigerant temperature. However, in the third embodiment, without performing such feedback control, the opening degree of the electric expansion valve 16 and the rotation speed of the compressor 14 are set to predetermined values at the start of the defrosting operation.

  The third embodiment will be described more specifically based on FIG. FIG. 9 is a control routine executed by the microcomputer of the control device 20 in the same manner as in FIG. 3 described above, and the same parts as those in FIG.

  First, in step S10, it is determined whether the outlet refrigerant temperature of the evaporator 17 detected by the temperature sensor 23 is lower than a predetermined temperature T1 (for example, −14 ° C.). If the outlet refrigerant temperature is lower than the predetermined temperature T1, it is excluded. It is determined that the frost operation is necessary, and the defrost operation is started in the next step S30. Specifically, the operation of the electric water pump 13 is stopped, the opening degree of the electric expansion valve 16 is set to a predetermined opening degree during the defrosting operation, and the compressor 14 is set at a predetermined rotation speed during the defrosting operation. Operate.

  Here, the predetermined opening during the defrosting operation of the electric expansion valve 16 is a value larger than the opening during the normal operation under the same conditions (same high pressure value).

  However, the predetermined opening degree of the electric expansion valve 16 and the predetermined rotation speed of the compressor 14 are used to prevent boiling of hot water in the water-refrigerant heat exchanger 15 during the defrosting operation. It is a predetermined value that is set to be within a predetermined temperature (for example, 90 ° C.). More specifically, the predetermined value of the electric expansion valve opening and the predetermined value of the compressor rotational speed are the hot water heater operating conditions at the start of defrosting (for example, hot water temperature detected by the temperature sensor 24, temperature sensor It may be determined on the basis of the outside air temperature detected by 25).

  Proceeding from step S30 to step S80, it is determined whether the outlet refrigerant temperature of the evaporator 17 is higher than the defrosting end temperature T3. As described above, the defrosting end temperature T3 is a temperature (T1 + α) that is higher than the predetermined temperature T1 at which the defrosting is started by a constant temperature α, and is 5 ° C., for example.

  While the determination in step S80 is NO, the defrosting operation in step S30 is continued. And if the exit refrigerant | coolant temperature of the evaporator 17 becomes higher than defrost end temperature T3, it will progress to step S90, will complete | finish defrost operation, and will transfer to normal operation control. This normal operation control is the same as the normal operation control in step S20.

  Note that the determination of the start and end of the defrosting operation is not limited to the determination based on the outlet refrigerant temperature of the evaporator 17, but can be variously modified as described above.

(Other embodiments)
In the first embodiment, during the defrosting operation, both the opening degree control of the pressure reducing device (expansion valve 16) and the rotation speed control of the compressor 14 are executed to control the compressor discharge refrigerant temperature. Only one of the opening degree control of the decompression device (expansion valve 16) and the rotation speed control of the compressor 14 may be executed to perform the compressor discharge refrigerant temperature control during the defrosting operation.

  In the first and third embodiments, the water pump 13 is stopped during the defrosting operation to reduce the refrigerant heat release amount in the water refrigerant heat exchanger 15, but the water pump 13 is not stopped completely, The pump 13 may be operated at a low speed by low rotation to reduce the refrigerant heat release amount in the water-refrigerant heat exchanger 15.

  In both the first and second embodiments, the internal heat exchanger 19 is provided in the heat pump cycle, but the present invention may be applied to a heat pump cycle that does not include the internal heat exchanger 19. Of course, the control of the third embodiment can be applied to a heat pump cycle that does not include the internal heat exchanger 19.

1 is an overall configuration diagram of a heat pump type water heater according to a first embodiment of the present invention. It is an electric control block diagram of a 1st embodiment. It is a flowchart which shows the action | operation of 1st Embodiment. It is a flowchart which shows the outline | summary of the control at the time of normal driving | operation in FIG. It is a Mollier diagram of the heat pump cycle of the first embodiment. (A) is a characteristic view of expansion valve opening degree control in FIG. 3, (b) is a characteristic view of compressor rotation speed control in FIG. It is a whole block diagram of the heat pump type water heater by 2nd Embodiment. It is a schematic sectional drawing of the ejector of FIG. It is a flowchart which shows the action | operation of 3rd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Hot water storage tank, 13 ... Water pump, 14 ... Compressor, 16 ... Electric expansion valve (pressure reduction device), 17 ... Evaporator, 20 ... Control apparatus.

Claims (6)

A compressor (14), a water refrigerant heat exchanger (15) for heating hot water stored in a hot water storage tank (10) by a refrigerant discharged from the compressor (14), and the water refrigerant heat exchanger (15) A pressure reducing device (16, 160) capable of electrically adjusting a passage opening degree, and an evaporator (17) for evaporating the low pressure refrigerant that has passed through the pressure reducing device (16, 160), while reducing the pressure of the high pressure refrigerant that has passed. A water pump (13) for circulating hot water in the hot water storage tank (10) to the water refrigerant heat exchanger (15),
During the defrosting operation of the evaporator (17), the water pump (13) is controlled so that the refrigerant heat dissipation amount in the water refrigerant heat exchanger (15) is reduced, and the decompression device (16, 160) By increasing the passage opening to a predetermined opening or more, the refrigerant flows in the order of the compressor (14), the water-refrigerant heat exchanger (15), the pressure reducing device (16, 160), and the evaporator (17). In the heat pump water heater that performs defrosting of the evaporator (17) while flowing,
During the defrosting operation of the evaporator (17), the discharge refrigerant temperature of the compressor (14) is within a predetermined temperature for preventing boiling of hot water in the water refrigerant heat exchanger (15). The heat pump type hot water heater is characterized in that at least one of control for increasing the passage opening of the pressure reducing device (16, 160) and control for decreasing the rotational speed of the compressor (14) is executed. During the defrosting operation of the evaporator (17), both the control for increasing the passage opening degree of the pressure reducing device (16, 160) and the control for decreasing the rotational speed of the compressor (14) are executed. The heat pump type water heater according to claim 1. During the defrosting operation of the evaporator (17), after the passage opening degree of the decompression device (16, 160) has increased to the maximum opening degree, control is performed to reduce the rotational speed of the compressor (14). The heat pump type water heater according to claim 2, wherein A compressor (14), a water refrigerant heat exchanger (15) for heating hot water stored in a hot water storage tank (10) by a refrigerant discharged from the compressor (14), and the water refrigerant heat exchanger (15) A pressure reducing device (16, 160) capable of electrically adjusting a passage opening degree, and an evaporator (17) for evaporating the low pressure refrigerant that has passed through the pressure reducing device (16, 160), while reducing the pressure of the high pressure refrigerant that has passed. A water pump (13) for circulating hot water in the hot water storage tank (10) to the water refrigerant heat exchanger (15),
During the defrosting operation of the evaporator (17), the water pump (13) is controlled so that the refrigerant heat dissipation amount in the water refrigerant heat exchanger (15) is reduced, and the decompression device (16, 160) By increasing the passage opening to a predetermined opening or more, the refrigerant flows in the order of the compressor (14), the water-refrigerant heat exchanger (15), the pressure reducing device (16, 160), and the evaporator (17). In the heat pump water heater that performs defrosting of the evaporator (17) while flowing,
During the defrosting operation of the evaporator (17), the discharge refrigerant temperature of the compressor (14) is within a predetermined temperature for preventing boiling of hot water in the water refrigerant heat exchanger (15). The heat pump hot water heater is characterized in that the passage opening of the decompression device (16, 160) and the rotational speed of the compressor (14) are set to predetermined values at the start of the defrosting operation. In the decompression device, the refrigerant is sucked into the nozzle portion (161) for decompressing the high-pressure refrigerant that has passed through the water-refrigerant heat exchanger (15), and the high-speed refrigerant flow ejected from the nozzle portion (161). Ejector having a refrigerant suction port (162) and a boosting unit (164) for converting the velocity energy of the refrigerant flow obtained by mixing the high-speed refrigerant flow and the refrigerant sucked from the refrigerant suction port (162) into pressure energy ( 160),
The ejector (160) includes a mechanism (165, 166) capable of electrically adjusting a passage opening degree of the nozzle portion (161).
The heat pump type hot water heater according to any one of claims 1 to 4, wherein the evaporator (17) is arranged in a passage (30) through which the refrigerant flows toward the refrigerant suction port (162). The internal heat exchanger (19) for exchanging heat between the high-pressure refrigerant after passing through the water-refrigerant heat exchanger (15) and the low-pressure refrigerant on the suction side of the compressor (14) is provided. The heat pump type water heater as described in any one of thru | or 5.

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