JP7449465B2 - heat pump water heater - Google Patents

Description

The present invention relates to a heat pump water heater, and more particularly to a heat pump water heater that prevents an excessive load on a compressor due to product variations in expansion valves.

A heat pump water heater has a heat pump circuit in which a compressor, a condensing heat exchanger, an expansion valve, and an evaporative heat exchanger are connected by a refrigerant circuit, a hot water storage tank that stores hot water, and the low-temperature water extracted from the hot water storage tank that is condensed. It is equipped with a heating circulation circuit that heats the water using a heat exchanger and returns it to the storage tank.

Heat pump operation in the heat pump circuit described above starts with the expansion valve open to ensure a smooth start of compressor operation, and then after the compressor has risen to a predetermined frequency, the expansion valve is opened. It is controlled to narrow down to a preset target value.
Therefore, in the past, a target value table for the expansion valve opening degree using the inlet water temperature and outside air temperature as parameters was set in advance, and the detected values of the inlet water temperature and outside air temperature were applied to the above target value table to determine the opening degree of the expansion valve. had set a target value.

Here, Patent Document 1 discloses that in a heat pump circuit, when the current value of the compressor exceeds a limit, the opening degree of the expansion valve is adjusted in the direction of opening.
Patent Document 2 discloses a technique of controlling a heat pump type heating device to open the throttle opening of an expansion valve when the discharge temperature from a compressor becomes high.

Japanese Patent Application Publication No. 2006-78146 Patent No. 4123220

Incidentally, there are product variations in expansion valves, and even slight product variations have a considerable effect on the flow rate, and the flow rate often differs even at the same opening degree.
However, conventionally, the target value for the opening degree of the expansion valve has been set based on a common target value table without considering product variations in the expansion valve.

If a lower limit product expansion valve with flow characteristics lower than the standard product is installed, the opening degree of the expansion valve will be too narrow, and the discharge temperature from the compressor will be lower than the target value. The voltage also rises too much, causing the compressor to overload and become overcurrent. Therefore, the current value of the compressor may momentarily exceed the current value specified by the extension regulations.

An object of the present invention is to provide a heat pump water heater that can suppress overcurrent in a compressor at the start of operation due to product variations in expansion valves.

The heat pump hot water supply device according to claim 1 includes: a heat pump circuit in which a compressor, a condensing heat exchanger, an expansion valve, and an evaporative heat exchanger are connected through a refrigerant circuit; a hot water storage tank for storing hot water; In a heat pump water heater equipped with a heating circulation circuit that heats low-temperature water using a condensing heat exchanger and returns it to a hot water storage tank, the opening degree of the expansion valve is opened to a predetermined initial opening degree when the heat pump operation by the heat pump circuit is started. The temperature is then reduced to a preset target value, and the discharge temperature increase rate at the compressor outlet under predetermined operating conditions at the start of heat pump operation is compared with the preset discharge temperature increase rate, When it is determined that the rate of increase in discharge temperature at the outlet of the compressor is greater than the preset rate of increase in discharge temperature by a certain value or more, the target value of the opening degree of the expansion valve is corrected to the side of increasing the opening degree using a correction value. A discharge temperature increase rate table that is configured to perform heat pump operation and presets the discharge temperature increase rate using inlet water temperature and outside air temperature as parameters; and a correction value that presets the correction value using inlet water temperature and outside air temperature as parameters. The present invention is characterized by comprising a table and a target value table in which a target value of the opening degree of the expansion valve is set in advance using incoming water temperature and outside temperature as parameters .

According to the above configuration, if the difference between the discharge temperature increase rate at the compressor outlet at the start of heat pump operation and the preset discharge temperature increase rate is greater than a certain value due to product variations in the expansion valve, Heat pump operation is performed by correcting the target value of the opening degree of the expansion valve using the correction value.
For example, if the discharge temperature rise rate at the compressor outlet is higher than the set value by more than a certain value, the target value of the expansion valve opening degree is greatly corrected by the correction value, which is caused by product variations in the expansion valve. Compressor overcurrent can be reliably prevented.

Then, the actual discharge temperature increase rate is compared with the discharge temperature increase rate in the discharge temperature increase rate table, and if the difference is greater than a certain value, a correction value is obtained from the correction value table, and the correction value is used to set the target value. Correct the target value of the expansion valve opening read from the table. In this way, the target value of the expansion valve opening degree can be corrected with high accuracy.

In the heat pump water heater according to claim 2 , in the invention according to claim 1 , the compressor is configured to perform frequency control in stages, and the discharge temperature rise rate at the outlet of the compressor is determined by the opening of the expansion valve. The compressor frequency is calculated from the rate of temperature rise during a certain period of time while the compressor frequency is rising to the predetermined frequency.

According to the above configuration, since the rate of temperature rise during a certain period of time when the compressor is started up to a predetermined frequency when the opening degree of the expansion valve is a predetermined initial opening degree is used, the discharge temperature at the compressor outlet is Since the rate of increase can be determined under certain conditions, the target value of the expansion valve opening degree can be corrected with high accuracy.

According to the present invention, various effects as described above can be obtained.

1 is a configuration diagram of a heat pump water heater according to an embodiment of the present invention. It is an operation time chart of the frequency of the compressor and the opening degree of the expansion valve at the time of starting operation of the heat pump water heater. It is a chart of a discharge temperature increase rate table. It is a chart of the correction value table of expansion valve opening degree. It is a chart of the target value table of expansion valve opening degree. It is a flowchart of compressor frequency control. It is a part of a flowchart of opening degree control of an expansion valve. This is the remainder of the flowchart for controlling the opening degree of the expansion valve. It is a flowchart of the setting process of an expansion valve opening degree.

First, the overall configuration of the heat pump water heater 1 will be described.
As shown in FIG. 1, the heat pump water heater 1 includes a heat pump unit 2, a hot water storage tank 3, and a heating circulation passage 4 that circulates hot water between the heat pump unit 2 and the hot water storage tank 3.

The hot water storage tank 3 is covered with a heat insulating material, and the hot water storage tank 3 is connected to a water supply system 5 for supplying clean water and a hot water supply system 6 for supplying heated hot water to a sink, bath, etc.
The heating circulation passage 4 includes a circulation passage 4a that supplies low-temperature water taken out from the hot water storage tank 4 to the condensation heat exchanger 8 of the heat pump unit 2, and a circulation passage 4a that supplies the low-temperature water taken out from the hot water storage tank 4 to the condensation heat exchanger 8 of the heat pump unit 2, and a condensation heat exchange of the hot water heated by the condensation heat exchanger 8 of the heat pump unit 2. It has a circulation return passage 4b that supplies hot water from the container 8 to the hot water storage tank 3.

Next, the heat pump unit 2 will be explained.
The heat pump unit 2 has a heat pump circuit in which a compressor 7, a condensing heat exchanger 8, an expansion valve 9 (expansion means), and an evaporative heat exchanger 10 are connected through a refrigerant passage 11 (refrigerant circuit) in an exterior case 2a. A refrigerant bypass passage 11a (bypass passage) branched from the refrigerant passage 11 between the compressor 7 and the condensing heat exchanger 8 includes a defrosting on-off valve 12 that can open and close the refrigerant bypass passage 11a, and an expansion valve 9 and It is connected to the refrigerant passage 11 between the evaporative heat exchangers 10.

A discharge temperature sensor 13 that detects the temperature of the refrigerant discharged from the compressor 7 is attached to the refrigerant passage 11 between the compressor 7 and the condensing heat exchanger 8 . The heat exchange passage section 8a of the condensing heat exchanger 8 connected to the hot water circulation passage 4 includes an inlet water temperature sensor 14 that detects the temperature of low-temperature water (incoming water temperature) on the inlet side of the condensing heat exchanger 8, and an inlet water temperature sensor 14 on the outlet side. An outlet temperature sensor 15 is attached to detect the temperature of hot water.

The heat pump unit 2 controls heating operation and the like by an auxiliary control unit 17 electrically connected to a control unit 16. In the heating operation, the defrosting on-off valve 12 is closed, the blower 18 that blows air to the compressor 7 and the evaporative heat exchanger 10 is driven, and the opening degree of the expansion valve 9 is adjusted to cool the refrigerant sealed in the refrigerant passage 11. circulate the refrigerant. An outside air temperature sensor 19 is attached to the case of the blower 18 to detect the outside air temperature, and a compressor inlet temperature sensor 20 is attached to the case to detect the refrigerant temperature at the outlet of the evaporative heat exchanger 10. Detection signals from the sensors 13, 14, 15, 19, 20 are supplied to a control unit 16 and an auxiliary control unit 17.

The high-temperature refrigerant that has been compressed and heated in the compressor 7 during the heating operation is introduced into the condensing heat exchanger 8 . In the condensing heat exchanger 8, heat exchange is performed between the high-temperature refrigerant and the hot water flowing through the heat exchange passage section 8a connected to the heating circulation passage 4, and the hot water is heated. The refrigerant, whose temperature has been lowered and partially liquefied through heat exchange, expands in the expansion valve 9 to further lower its temperature, and is introduced into the evaporative heat exchanger 10. In the evaporative heat exchanger 10, the refrigerant absorbs heat from the outside air, evaporates, and is introduced into the compressor 7 again.

In this heat pump water heater 1, due to product variations in the expansion valve 9, variations occur in the discharge pressure of the refrigerant at the outlet of the compressor, the compressor 7 becomes overloaded, an overcurrent flows, and power is supplied to the heat pump unit 2. To prevent this, the heat pump should be operated as follows:
When the heat pump operation by the heat pump circuit is started, the opening degree of the expansion valve 9 opens from the standby opening degree (for example, 70 steps) to the initial opening degree (for example, 500 steps), and after holding this opening degree for a while, the opening degree is changed to the preset opening degree. The discharge temperature increase rate at the compressor outlet under predetermined operating conditions at the start of heat pump operation is compared with a preset discharge temperature increase rate, and the discharge temperature increase rate at the compressor outlet is determined to be When it is determined that the rate of increase in the discharge temperature is higher than the set discharge temperature increase rate by a certain value or more, the target value of the opening degree of the expansion valve 9 is corrected to the side of increasing the opening degree using the correction value, and the heat pump operation is performed.

FIG. 2 shows an operation time chart of the frequency of the compressor 7 and the opening degree of the expansion valve 9 when the heat pump water heater 1 starts operating.
After the start of operation, the frequency of the compressor 7 is increased to a predetermined frequency (for example, 50 Hz) at a rate of increase of 0.1 Hz/sec, then maintained at the predetermined frequency for 240 seconds, and then increased at a rate of increase of 0.1 Hz/sec. Increase the frequency to the target frequency (e.g., 70 Hz), and after 90 seconds at the target frequency, increase the frequency to the set frequency (e.g., 100 Hz) at a rate of increase of 0.1 Hz/sec, and then perform steady operation at that frequency. conduct.

After the start of operation, the expansion valve 9 increases the opening degree from the standby position at a rate of increase of 50 pulses/sec (pps) to the initial opening degree (for example, 500 steps), and maintains this large initial opening degree for a certain period of time. to smooth the frequency rise of the compressor 7 and to maintain the compressor 7 in a non-overloaded state, detect the rate of increase in refrigerant temperature on the compressor discharge side between timings t1 and t2, and then, After 90 seconds have passed since the compressor 7 has risen to a predetermined frequency, the opening degree of the expansion valve 9 is decreased at a rate of 50 pps, and after decreasing to the initial target opening degree (for example, 300 steps), the opening degree is reduced to the initial target opening degree. is maintained for a while, and after 90 seconds have elapsed since the frequency of the compressor 7 reached the set frequency, the opening degree of the expansion valve 9 is decreased to the opening degree set value at a reduction rate of 0.1 pps.

In order to perform the heat pump operation described above, a discharge temperature increase rate table (see Figure 3) in which the discharge temperature increase rate is preset using the inlet water temperature and outside temperature as parameters, and correction of the expansion valve opening degree using the inlet water temperature and outside temperature as parameters. It has a correction value table (see FIG. 4) in which values are set in advance, and a target value table (see FIG. 5) in which target values for the expansion valve opening degree are set in advance using inlet water temperature and outside air temperature as parameters.

The compressor 7 is configured to perform frequency control in stages, and the rate of increase in the discharge temperature at the outlet of the compressor 7 described above is the same as that of the compressor 7 when the opening degree of the expansion valve 9 is at a predetermined initial opening degree. It is calculated from the rate of temperature rise during a certain period of time (60 seconds) at timings t1 and t2 when the frequency is rising to a predetermined frequency.

Hereinafter, the compressor frequency control and the opening degree control of the expansion valve 9 executed by the auxiliary control unit 17 will be explained based on the flowcharts of FIGS. 6 to 9. Note that the opening degree control of the expansion valve 9 is executed at interval interruptions (for example, at 100 ms intervals) to the compressor frequency control.
Note that these control flowcharts and the above-mentioned tables are stored in the microcomputer of the auxiliary control unit 17 in advance. Note that the symbols Si (i=1, 2, . . . ) in the flowchart indicate each step.

First, compressor frequency control will be explained based on FIG. 6.
When the operation of the heat pump unit 2 (this operation also includes a test run) is started, initial settings are made, and then the compressor starts operating (S1), and the compressor speed increases at an increase rate of 0.1 Hz/sec. 7 frequency N is increased (S2). Next, it is determined whether the frequency N=30Hz or not, and if the determination is No, S2 and S3 are repeated, and when the determination in S3 is Yes, the detected temperature Th1 of the discharge temperature sensor 13 is read and stored in the memory, At the same time, timer TM1 is started (S4). Note that the above-mentioned 30 Hz is an example, and the frequency is not limited to this.

In S5, it is determined whether or not the measured time TM1 of the timer TM1 has become 60 seconds or more, and if the determination is No, S5 is repeated, and if the determination in S5 is Yes, the detected temperature Th2 of the discharge temperature sensor 13 is read. and stored in memory. In this way, the discharge temperatures Th1 and Th2 at the timing t1 when the frequency N of the compressor 7 becomes 30Hz while rising to a predetermined frequency (for example, 50Hz) and at the timing t2 60 seconds after that are detected and stored in the memory. be done.

Thereafter, when the frequency of the compressor 7 reaches a predetermined frequency (for example, 50 Hz), the predetermined frequency is maintained for 240 seconds (S7, S8), and then the frequency is increased to 70 Hz at a rate of 0.1 Hz/sec (S9, S10). After that, the frequency N is held at 70 Hz for 90 seconds (S11), and then the frequency N is increased to the set frequency (for example, 100 Hz) at an increase rate of 0.1 Hz/sec (S12, S13), and then the frequency N is held at the set frequency. (S14), the heat pump operation continues.

Next, the opening degree control of the expansion valve 9 will be explained based on FIGS. 7 and 8.
After the heat pump unit 2 starts operating, the opening degree K of the expansion valve 9 is set to the standby opening degree (standby position) (for example, 70 steps) (S20), and then the expansion valve opening degree K is increased by 50 pps until it reaches 500 steps. When the expansion valve opening degree K reaches 500 steps, it is held at 500 steps for a while.

Next, it is determined whether the frequency of the compressor 7 has become 50 Hz (S24), and if the determination is Yes, a process for setting the expansion valve opening K is executed in S25.
Here, the above-mentioned process for setting the expansion valve opening degree K will be explained based on FIG. 9.
First, the inlet water temperature is read from the inlet water temperature sensor 14, the outside temperature is read from the outside air temperature sensor 19, and stored in the memory (S50), and then the above-mentioned inlet water temperature and outside air temperature are combined with the discharge temperature increase rate table shown in FIG. The discharge temperature increase rate ΔTo is calculated from (S51).

Next, the actual discharge temperature increase rate ΔT is calculated using the formula ΔT=(Th2−Th1) and stored (S52). Next, determine whether the difference (ΔT - ΔTo) between the actual discharge temperature increase rate ΔT and the discharge temperature increase rate ΔTo set in the discharge temperature increase rate table is greater than or equal to a predetermined value C (for example, C=1°C/min). (S53), and when the determination is Yes, S54 to S56 are executed, and when the determination is No, S57 and S58 are executed. Note that the values in the discharge temperature increase rate table indicate the temperature increase rate for 60 seconds.

If the determination in S53 is Yes, an opening correction value ΔK is calculated in S54 from the inlet water temperature, the outside air temperature, and the expansion valve opening correction value table shown in FIG. Next, in S55, a target opening value Ko is calculated from the inlet water temperature, the outside air temperature, and the expansion valve opening target value table shown in FIG.
Next, in S56, the opening set value Ks is calculated from the opening correction value ΔK and the opening target value Ko using the formula Ks=(opening target value Ko+opening correction value ΔK), and then the process returns.
If the determination in S53 is No, a target opening value Ko is calculated in S57 from the inlet water temperature, the outside air temperature, and the expansion valve opening target value table.
Next, in S58, the opening degree setting value Kso is calculated using the formula: opening degree setting value Kso=opening degree target value Ko, and then the process returns.

Next, returning to the flowcharts of FIGS. 7 and 8, in S26, the timer TM2 is started, and when the timer TM2 has elapsed for 90 seconds (S27), the expansion valve opening K is reduced at a rate of 50 pps. In the next S29, it is determined whether the difference in the discharge temperature increase rate (ΔT - ΔTo) is equal to or greater than the predetermined value C, and if the determination is Yes, in S30, the expansion valve opening degree K is Valve opening degree K=(initial target opening degree Ko1 + opening degree correction value ΔK) (initial target opening degree Ko1 is calculated in 300 steps, for example).

Thereafter, while maintaining the expansion valve opening degree K at the above value, it is determined whether 90 seconds have passed since the compressor 7 reaches the set frequency (S31), and if the determination is Yes, the expansion valve opening degree K is decreased at a rate of 0.1 pps (S32), and then in S33 it is determined whether the expansion valve opening K has reached the corrected opening set value Ks, and if the determination is Yes, the opening is The heat pump operation continues while maintaining the set value Ks.

If the determination in S29 is No, the expansion valve opening degree K is set to the initial target opening degree Ko1 in S35, and then in S36, 90 seconds have elapsed since the compressor 7 reached the set frequency. It is determined whether or not (S36), and when the determination is Yes, the expansion valve opening degree K is decreased at a decreasing rate of 0.1 pps (S37), and then in S38, the expansion valve opening degree K is set to the opening degree setting value Kso. If the determination is YES, the heat pump operation is continued while maintaining the opening degree setting value Kso (S39).

The functions and effects of the heat pump water heater 1 explained above will be explained.
Due to product variations in the expansion valve 9, the difference between the actual discharge temperature increase rate at the compressor outlet at the start of heat pump operation and the discharge temperature increase rate set in advance in the discharge temperature increase rate table shown in FIG. 3 exceeds a certain value. If the correction value for the expansion valve opening is read from the correction value table in FIG. 4, and the target value for the opening of the expansion valve 9 set in the target value table in FIG. 5 is corrected by the correction value, the heat pump is Drive. In this way, the target value of the expansion valve opening degree can be corrected with high accuracy.

In this way, when the discharge temperature increase rate at the compressor outlet is higher than the set value by a certain value or more, the target value of the opening degree of the expansion valve 9 is greatly corrected by the correction value. Overcurrent in the compressor 7 due to variations can be reliably prevented.

Since the rate of temperature rise during a certain period of time when the compressor 7 is started up to a predetermined frequency when the opening degree of the expansion valve 9 is a predetermined initial opening degree is used, the discharge temperature rise rate at the compressor outlet is set to a constant rate. Since the target value of the expansion valve opening can be determined with high accuracy, it is possible to correct the target value of the expansion valve opening degree with high accuracy.

An example of modifying the embodiment will be described.
1) In the embodiment, one correction value table is provided as shown in FIG. 4, and the difference between the actual discharge temperature increase rate ΔT and the discharge temperature increase rate ΔTo set in the discharge temperature increase rate table (ΔT−ΔTo ) is greater than or equal to the predetermined value C.However, instead of the predetermined value C, predetermined values C1 and C2 (however, C1>C2) are set, and instead of one correction value table, the predetermined value A correction value table corresponding to C1 and a correction value table corresponding to predetermined value C2 are provided, and the correction value table is configured to be used differently depending on the magnitude of the difference (ΔT - ΔTo) in the discharge temperature increase rate ΔTo. It's okay.

2) In the embodiment, if the difference in discharge temperature increase rate (ΔT - ΔTo) is equal to or greater than the predetermined value C, the initial target opening Ko1 is also corrected by the opening correction value ΔK, as shown in S30 in FIG. However, since there is a low possibility that the compressor will be overloaded at the initial target opening Ko1, the initial target opening Ko1 may be configured not to be corrected by the opening correction value ΔK.

3) The pattern shown in FIG. 2 in which the frequency of the compressor is increased stepwise is an example and is not limited to this. In addition, those skilled in the art can implement the embodiments with various modifications without departing from the spirit of the present invention.

1 Heat pump water heater 2 Heat pump unit 3 Hot water storage tank 4 Heating circulation passage 7 Compressor 8 Condensing heat exchanger 9 Expansion valve 10 Evaporative heat exchanger 11 Refrigerant passage

Claims (2)

A heat pump circuit in which a compressor, a condensing heat exchanger, an expansion valve, and an evaporative heat exchanger are connected by a refrigerant circuit, a hot water storage tank that stores hot water, and the low temperature water taken out from this hot water storage tank is heated by the condensing heat exchanger. In a heat pump water heater equipped with a heating circulation circuit that heats hot water and returns it to a storage tank,
When the heat pump operation by the heat pump circuit starts, the opening degree of the expansion valve is opened to a predetermined initial opening degree, and is then narrowed down to a preset target value, so that the opening degree of the expansion valve is opened to a predetermined initial opening degree, and is then narrowed down to a preset target value. Comparing the discharge temperature increase rate at the compressor outlet under the conditions with a preset discharge temperature increase rate, and determining that the discharge temperature increase rate at the compressor outlet is greater than the preset discharge temperature increase rate by a certain value or more. When the expansion valve is opened, the target value of the opening of the expansion valve is corrected to increase the opening by the correction value , and the heat pump is operated.
A discharge temperature increase rate table in which the discharge temperature increase rate is preset using inlet water temperature and outside air temperature as parameters, a correction value table in which the correction value is preset in advance using inlet water temperature and outside air temperature as parameters, and inlet water temperature and outside air temperature. A heat pump water heater characterized by having a target value table in which target values for the opening degree of the expansion valve are set in advance as parameters . The compressor is configured to perform frequency control in stages, and the discharge temperature rise rate at the outlet of the compressor is determined when the opening degree of the expansion valve is a predetermined initial opening degree and the frequency of the compressor is a predetermined opening degree. The heat pump water heater according to claim 1, wherein the temperature is calculated from the rate of temperature increase during a certain period of time while the frequency is increasing .