EP2980497B1

EP2980497B1 - Heat pump and air conditioner or water heater having the same

Info

Publication number: EP2980497B1
Application number: EP15180055.4A
Authority: EP
Inventors: Mamoru Hamada; Kouji Yamashita
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2008-01-21
Filing date: 2008-01-21
Publication date: 2022-09-14
Anticipated expiration: 2028-01-21
Also published as: JP5528119B2; EP2980498A1; EP2157380A4; JPWO2009093297A1; EP2157380B1; EP2157380A1; EP2980498B1; WO2009093297A1; EP2980497A1

Description

Technical Field

The present invention relates to a heat pump and an air conditioner or a water heater having the same, and more particularly to a heat pump which detects capacity deterioration caused by frost formation on an evaporator accurately and starts a defrosting operation at an appropriate timing and an air conditioner or a water heater having the same.

Background Art

As for an air conditioner, which is one of prior-art heat pumps, a device is proposed "that decides at step S16 whether or not a liquid injection circuit constituted by 20, 21, 22, 23a, 23b, 24, 25a, 25b is in use, and a calculation equation for deciding defrosting start is changed in accordance with the result. Step S17 is a decision of starting a defrosting operation if the liquid injection circuit is used. When an evaporation temperature Te falls lower than a defrosting start decision temperature C1 × To + D1 (3 × To + 10, for example) calculated from an outside temperature To, the defrosting operation is started. On the other hand, Step S18 is the decision of starting the defrosting operation if the liquid injection circuit is not used. When the evaporation temperature Te falls lower than a defrosting start decision temperature C2 × To + D2 (2.5 × To + 8, for example) calculated from the outside temperature To, the defrosting operation is started." (See Patent Document 1, for example).
Also, a device is proposed in which "during a heating operation, a calculation circuit 21 monitors the time elapsed from the start of an operation by using an output of a timer circuit 22 initiated at the same time as the operation start. If a given time (15 minutes, for example) elapsed, a temperature of an outdoor heat exchanger 3, that is, an evaporator temperature Te is detected by a signal from an evaporator temperature detection circuit 9 at that time, and it is stored in a temperature storage portion 23 as Te₀. In this case, the given time T₁ is the time till the evaporator temperature Te becomes stable. Moreover, the calculation circuit 21 sequentially detects the evaporator temperature Te and calculates the following equation. B = (Te + A) / (Te₀ + A). A is a specific numeral value, and "20", for example. That is, a ratio is set to be calculated between a value obtained by adding the numeral value A to the evaporator temperature Te₀ after the given time T₁ elapsed and a value obtained by adding the numeral value A to the sequentially detected evaporator temperature Te. The calculation circuit 21 compares a calculated value B and a set value C (0.5, for example), and if B is larger than C, the heating operation is continued as it is and the above calculation is repeated (at a rate of several times per second). However, if B is equal to or smaller than C, it is considered that a frost amount is at a certain level or more and defrosting is required, and a four-way valve return command is issued to a four-way valve driving circuit 24." (See Patent Document 2, for example).

[Patent Document 1] Japanese Unexamined Patent Application Publication No.2001-99529 (paragraph number 0031, Fig. 4)
[Patent Document 2] Japanese Unexamined Patent Application Publication No. 62-19656 (page 3, Fig. 1)

EP1855064A1 discloses that based on a result of detection taken by the high-low pressure difference detection means for detecting a difference between a high and a low pressure of a refrigeration cycle, an estimate of whether there is leakage of refrigerant in an expansion valve is made. Based on the result detected by the high-low pressure difference detection means, a control means sets a reference temperature to a value corresponding to the degree of refrigerant leakage in the expansion valve, and determines the termination of an ice melting operation, regardless of whether or not there is refrigerant leakage in an expansion valve.

Disclosure of Invention

Problems to be Solved by the Invention

As for detecting means for directly detecting a frost formation state of an evaporator, the frost formation state of the evaporator might not be able to be detected due to snow covering the detecting means, for example. But the prior-art frost formation detecting means (See Patent Documents 1 and 2, for example) shown in the above detects the frost formation state of the evaporator indirectly using an evaporation temperature of the evaporator. Therefore, when compared with detecting means for directly detecting the frost formation state, the frost formation state on the evaporator can be accurately detected. Also, in the configuration of Patent Document 1, an outdoor temperature is used as a parameter for detecting the frost formation state on the evaporator, and a false decision of a change in the evaporation temperature of the evaporator with the change in the outdoor temperature as frost formation on the evaporator can be also prevented. Also, in the configuration of Patent Document 2, for example, since the outdoor temperature is not used as a parameter for detecting the frost formation state on the evaporator, even if the outdoor temperature cannot be detected due to snow covering the outdoor temperature detecting means, for example, the frost formation state on the evaporator can be accurately detected.
However, in either of the prior-art frost formation state detecting shown in the above, though misdetection of the frost formation state on the evaporator caused by the outdoor environment is given consideration, misdetection of the frost formation on the evaporator caused by a change in an indoor environment (change of a set temperature or the like) or a change in a compressor frequency which occur during a heating operation is not considered, which is a problem. That is, if the evaporation temperature of the evaporator is lowered due to a change in the indoor environment and a change in the compressor frequency, for example, there is a problem that the drop of the evaporation temperature is erroneously decided as frost formation on the evaporator.
The present invention was made in order to solve the above problems and has an object to obtain a heat pump that can detect a frost formation state on an evaporator accurately without being affected by a change in an indoor environment or a change in a compressor frequency and an air conditioner or a water heater having this heat pump.

Means for Solving the Problems

The heat pump according to the present invention is defined in claim 1. It is provided with, in a heat pump having a refrigerant circuit in which a compressor, a condenser, an expansion valve, and an evaporator are connected sequentially, evaporator refrigerant saturation temperature detecting means for detecting an evaporation temperature of the evaporator, evaporator sucked air temperature detecting means for detecting an evaporator sucked air temperature of the evaporator, compressor frequency detecting means for detecting a compressor frequency of the compressor, and first frost formation state detecting means for detecting a frost formation state of the evaporator, and the first frost formation state detecting means sets a calculation value obtained by dividing a difference between the evaporator sucked air temperature and the evaporation temperature by the compressor frequency to a characteristic amount and detects a drop in heat exchange performance caused by the frost formation on the evaporator on the basis of the characteristic amount, the time change amount is a difference in said characteristic amount before and after a given time elapsed, and when the characteristic amount is defined as T, a compressor operation time is defined as t, and a change-amount detection time is defined as D, the time change amount is calculated by subtracting the. characteristic amount T(t) at the compressor operation time t from the characteristic amount T(t - D) at the compressor operation time (t - D), that is, T(t - D) - T(t).

Effects of the Invention

In an example which is not part of the present invention, a calculation value obtained by dividing a difference between the evaporator sucked air temperature and the evaporation temperature by the compressor frequency is used as a characteristic amount, and drop in the heat exchange performance caused by the frost formation on the evaporator is detected on the basis of the characteristic amount, therefore, a frost formation state on the evaporator can be detected accurately without being affected by a change in the compressor frequency in addition to a change in the outdoor environment.
Also, in an example which is not part of the present invention, a calculation value obtained by dividing a difference between the evaporator sucked air temperature and the evaporation temperature calculated from the evaporation pressure by the compressor frequency is used as a characteristic amount, and drop in the heat exchange performance caused by the frost formation on the evaporator is detected on the basis of the characteristic amount, therefore, a frost formation state on the evaporator can be detected accurately without being affected by a change in the compressor frequency in addition to a change in the outdoor environment.
Also, in an example which is not part of the present invention, a calculation value obtained by dividing a difference between the evaporator sucked air temperature and the evaporation temperature by the compressor frequency is used as a characteristic amount, and drop in the heat exchange performance caused by the frost formation on the evaporator is detected on the basis of a time change amount of the characteristic amount, therefore, frost formation state on the evaporator can be detected accurately without being affected by a change in the compressor frequency in addition to a change in the outdoor environment even if detected values of the evaporator refrigerant saturation temperature detecting means, the evaporator sucked air temperature detecting means, and the compressor frequency detecting means deviate by a secular change.
Also, in an example which is not part of the present invention, a calculation value obtained by dividing a difference between the evaporator sucked air temperature and the evaporation temperature calculated from the evaporation pressure by the compressor frequency is used as a characteristic amount, and drop in the heat exchange performance caused by the frost formation on the evaporator is detected on the basis of a time change amount of the characteristic amount, therefore, a frost formation state on the evaporator can be detected accurately without being affected by a change in the compressor frequency in addition to a change in the outdoor environment even if detected values of the evaporator refrigerant pressure detecting means, the evaporator sucked air temperature detecting means, and the compressor frequency detecting means deviate by a secular change.
In the present invention, the evaporation temperature is used as a characteristic amount, and drop in the heat exchange performance caused by the frost formation on the evaporator is detected on the basis of a time change amount of the characteristic amount, therefore, even in an environment where the evaporator sucked air temperature cannot be detected due to snow coverage or the like (an environment where the evaporator sucked air temperature might be misdetected), a frost formation state on the evaporator can be accurately detected without being affected by a change in the compressor frequency in addition to a change in the outdoor environment.
Also, in an example which is not part of the present invention, the evaporation pressure is used as a characteristic amount, and drop in the heat exchange performance caused by a frost formation on the evaporator is detected on the basis of a time change amount of the characteristic amount, therefore, even in an environment where the evaporator sucked air temperature cannot be detected due to snow coverage or the like (an environment where the evaporator sucked air temperature might be misdetected), a frost formation state on the evaporator can be accurately detected without being affected by a change in the compressor frequency in addition to a change in the outdoor environment.

Brief Description of Drawings

[Fig. 1] Fig. 1 is an outline configuration diagram of a refrigerant circuit of an air conditioner using a heat pump in Embodiment 1.
[Fig. 2] Fig. 2 is a configuration block diagram for detecting performance drop caused by a frost formation of an outdoor heat exchanger 6 using the heat pump in Embodiment 2.
[Fig. 3] Fig. 3 is a flowchart of defrosting start decision control of the air conditioner using the heat pump in Embodiment 1.
[Fig. 4] Fig. 4 is a characteristic diagram illustrating a relation between a characteristic amount T1 and an operation time of a compressor 3 in Embodiment 1.
[Fig. 5] Fig. 5 is an outline configuration diagram of a refrigerant circuit of an air conditioner using a heat pump in Embodiment 2.
[Fig. 6] Fig. 6 is a configuration block diagram for detecting performance drop caused by a frost formation of the outdoor heat exchanger 6 using the heat pump in Embodiment 2.
[Fig. 7] Fig. 7 is a flowchart of defrosting start decision control of the air conditioner using the heat pump in Embodiment 2.
[Fig. 8] Fig. 8 is a characteristic diagram illustrating a relation between a characteristic amount T2 and an operation time of the compressor 3 in Embodiment 2.
[Fig. 9] Fig. 9 is an outline configuration diagram of a refrigerant circuit of an air conditioner using a heat pump in Embodiment 3.
[Fig. 10] Fig. 10 is a configuration block diagram for detecting performance drop caused by a frost formation of the outdoor heat exchanger 6 using the heat pump in Embodiment 3.
[Fig. 11] Fig. 11 is a flowchart of defrosting start decision control of the air conditioner using the heat pump in Embodiment 3.
[Fig. 12] Fig. 12 is a characteristic diagram illustrating a relation between a time change amount of the characteristic amount T1 and an operation time of the compressor 3 in Embodiment 3.
[Fig. 13] Fig. 13 is an outline configuration diagram of a refrigerant circuit of an air conditioner using a heat pump in Embodiment 4.
[Fig. 14] Fig. 14 is a configuration block diagram for detecting performance drop caused by a frost formation of the outdoor heat exchanger 6 using the heat pump in Embodiment 4.
[Fig. 15] Fig. 15 is a flowchart of a defrosting start decision control of the air conditioner using the heat pump in Embodiment 4.
[Fig. 16] Fig. 16 is a characteristic diagram illustrating a relation between a time change amount of the characteristic amount T2 and an operation time of the compressor 3 in Embodiment 4.
[Fig. 17] Fig. 17 is an outline configuration diagram of a refrigerant circuit of an air conditioner using a heat pump in Embodiment 5.
[Fig. 18] Fig. 18 is a configuration block diagram for detecting performance drop caused by a frost formation of the outdoor heat exchanger 6 using the heat pump in Embodiment 5.
[Fig. 19] Fig. 19 is a flowchart of defrosting start decision control of the air conditioner using the heat pump in Embodiment 5.
[Fig. 20] Fig. 20 is a characteristic diagram illustrating a relation between a time change amount of the characteristic amount T3 and an operation time of the compressor 3 in Embodiment 5.
[Fig. 21] Fig. 21 is an outline configuration diagram of a refrigerant circuit of an air conditioner using a heat pump in Embodiment 6.
[Fig. 22] Fig. 22 is a configuration block diagram for detecting performance drop caused by a frost formation of the outdoor heat exchanger 6 using the heat pump in Embodiment 6.
[Fig. 23] Fig. 23 is a flowchart of defrosting start decision control of the air conditioner using the heat pump in Embodiment 6.
[Fig. 24] Fig. 24 is a characteristic diagram illustrating a relation between a time change amount of the characteristic amount T4 and an operation time of the compressor 3 in Embodiment 6.
[Fig. 25] Fig. 25 is a flowchart of defrosting start decision control of the air conditioner using the heat pump in Embodiment 7.
[Fig. 26] Fig. 26 is a characteristic diagram illustrating a relation between a time change amount of the characteristic amount T1 and an operation time of the compressor 3 when the air conditioner in Embodiment 7 is in a pull-down operation.
[Fig. 27] Fig. 27 is a flowchart for determining a next defrosting non-operation time th_next in Embodiment 7.
[Fig. 28] Fig. 28 is a configuration block diagram for detecting performance drop caused by a frost formation of the outdoor heat exchanger 6 using the heat pump in Embodiment 8.
[Fig. 29] Fig. 29 is a flowchart of defrosting start decision control of the air conditioner using the heat pump in Embodiment 8.
[Fig. 30] Fig. 30 is an outline configuration diagram illustrating an example of a second frost formation state detecting means in Embodiment 9.
[Fig. 31] Fig. 31 is a characteristic diagram illustrating a relationship between an output voltage [V] of a light emitting portion 21a and an operation time of the compressor 3 in Embodiment 9 of the present invention.
[Fig. 32] Fig. 32 is a characteristic diagram illustrating a relationship between capacitance [F] between a fin and an electrode of the outdoor heat exchanger 6 and an operation time of the compressor 3 in Embodiment 9.
[Fig. 33] Fig. 33 is a characteristic diagram illustrating a relationship between a radiation temperature [°C] on the surface of the outdoor heat exchanger 6 and an operation time of the compressor 3 in Embodiment 9.

Reference Numerals

1: outdoor unit
2: indoor unit
3: compressor
4: four-way valve
5: expansion valve
6: outdoor heat exchanger
6a: fin
7: fan for outdoor heat exchanger
8: indoor heat exchanger
9: fan for indoor heat exchanger
10: evaporator refrigerant saturation temperature detecting means
11: evaporator sucked air temperature detecting means
12: compressor frequency detecting means
13: evaporator refrigerant pressure detecting means
14: compressor operation time measuring means
21: optical frost formation sensor
21a: light emitting portion
21b: light receiving portion
22: light amount decision control portion
100: control portion
101: timer
102: memory
103: frost formation state detecting means
104: defrosting allowing means

Best Modes for Carrying Out the Invention

Embodiment

1

Fig. 1 is an outline configuration diagram of a refrigerant circuit of an air conditioner using a heat pump in Embodiment 1 of the present invention. The air conditioner includes an outdoor unit 1 and an indoor unit 2, which are connected by piping. In the outdoor unit 1, a compressor 3 that can vary a frequency, a four-way valve 4 for switching a flow passage between cooling and heating, an expansion valve 5, an outdoor heat exchanger 6 that will become an evaporator in a heating operation, and an outdoor heat exchanger fan 7 are provided as components of a refrigerant circuit.
In the outdoor heat exchanger 6, evaporator refrigerant saturation temperature detecting means 10 is provided for detecting a refrigerant saturation temperature (evaporation temperature in a heating operation) of the outdoor heat exchanger 6 (evaporator), and evaporator sucked air temperature detecting means 11 for detecting an air temperature (outdoor temperature) of air flowing into the outdoor heat exchanger is provided in the vicinity of the outdoor heat exchanger 6. Also, compressor frequency detecting means 12 for detecting a compressor frequency f is provided in the compressor 3. Moreover, a control portion 100 is provided in the outdoor unit 1.
The evaporator refrigerant saturation temperature detecting means 10 may be provided between the expansion valve 5 and the outdoor heat exchanger 6. Also, though the control portion 100 is provided in the outdoor unit 1, it may be provided in the indoor unit 2 or may be provided outside.
Also, in the indoor unit 2, an indoor heat exchanger 8 that will become a condenser in a heating operation and an indoor heat exchanger fan 9 are provided as components of the refrigerant circuit.
Fig. 2 is a block diagram of a configuration for detecting performance drop caused by a frost formation of the outdoor heat exchanger 6 using the heat pump in Embodiment 1 of the present invention. The control portion 100 is provided with a timer 101, a memory 102, frost formation state detecting means 103 corresponding to first frost formation state detecting means of the present invention and the like. The timer 101 measures an operation time or the like. The memory 102 stores an evaporation temperature Te, an evaporator sucked air temperature Ta, a compressor frequency f and the like detected by the evaporator refrigerant saturation temperature detecting means 10, the evaporator sucked air temperature detecting means 11, and the compressor frequency detecting means 12, respectively. The frost formation state detecting means 103 calculates a characteristic amount T1, which will be described later, using the evaporation temperature Te, the evaporator sucked air temperature Ta, and the compressor frequency f to detect a frost formation state on the outdoor heat exchanger 6. The control portion 100 sends a control signal to each driving portion of the compressor 3, the four-way valve 4, the outdoor heat exchanger fan 7, and the indoor heat exchanger fan 9 on the basis of information of the timer 101, the memory 102, the frost formation state detecting means 103 and the like.
An operation in the air conditioner using the heat pump in Embodiment 1 will be described using Fig. 1.
First, the operation in the heating operation will be described. In the heating operation, a flow passage of the four-way valve 4 is set in the direction of a solid line in Fig. 1. A high temperature and high pressure gas refrigerant discharged from the compressor 3 flows into the indoor heat exchanger 8 provided in the indoor unit 2 through the four-way valve 4. After that, it is condensed and liquefied while radiating heat to the indoor air in the indoor heat exchanger 8 to become a high-pressure liquid refrigerant. At this time, the indoor air blown to the indoor heat exchanger 8 by the indoor heat exchanger fan 9 is heated by the indoor heat exchanger 8 to perform heating operation. The high-pressure liquid refrigerant exited from the indoor heat exchanger 8 returns to the outdoor unit 1.
The high-pressure liquid refrigerant returned to the outdoor unit 1 is decompressed by the expansion valve 5 to turn into a low-pressure two-phase state and flows into the outdoor heat exchanger 6. In the outdoor heat exchanger 6, the liquid refrigerant absorbs heat from the outdoor air blown from the outdoor heat exchanger fan 7 to evaporate and become a low-pressure gas refrigerant. After that, the refrigerant flows into the compressor 3 through the four-way valve 4. The compressor 3 raises the pressure of the low-pressure gas refrigerant and discharges it.
Next, a defrosting operation will be described. In the defrosting operation, the flow passage of the four-way valve 4 is set in the direction of a broken line in Fig. 1. A high-temperature and high-pressure gas refrigerant discharged from the compressor 3 flows into the outdoor heat exchanger 6 through the four-way valve 4. After that, the refrigerant is condensed and liquefied in the outdoor heat exchanger 6 to become a high-pressure liquid refrigerant. At this time, frost adhering to the outdoor heat exchanger 6 is melted and removed by a heat of the high-temperature and high-pressure gas refrigerant flowed into the outdoor heat exchanger 6.
The defrosting operation is not limited to that shown in Embodiment 1. For example, by providing a bypass pipe through which a high-temperature gas refrigerant discharged from the compressor 3 flows into the outdoor heat exchanger 6, the defrosting operation can be realized without switching the four-way valve 4 or providing the four-way valve 4 in the outdoor unit 1.
Fig. 3 is a flowchart of defrosting start decision control of the air conditioner using the heat pump in Embodiment 1 of the present invention.
If the heating operation is started at step S-1, the frost formation state detecting means 103 calculates a characteristic amount T1 shown in the following equation from the evaporator sucked air temperature Ta detected by the evaporator sucked air temperature detecting means 11, the evaporation temperature Te detected by the evaporator refrigerant saturation temperature detecting means 10, and the compressor frequency f detected by the compressor frequency detecting means 12 at step S-2: $T 1 = (Ta - Te) / f$
A command value sent from the control portion 100 to the compressor 3 may be used as the compressor frequency f.
After that, at step S-3, the frost formation state detecting means 103 decides whether the characteristic amount T1 exceeds a threshold value S1 set in advance. If the characteristic amount T1 exceeds the threshold value S1, the processing proceeds to step S-4, where the defrosting operation is started. If the characteristic amount T1 does not exceed the threshold value S1, the processing returns back to step S-2, where the process is repeated.
During a heating operation, the evaporation temperature Te of the outdoor heat exchanger 6 might be lowered due to a factor other than drop in the evaporation temperature Te caused by a frost formation on the outdoor heat exchanger 6.
For example, if a user raises a indoor set temperature or if a temperature difference between the indoor temperature and the set temperature becomes large, the control portion 100 increases the compressor frequency f of the compressor 3 in order to raise a condensation temperature of the indoor heat exchanger 8. At this time, since a refrigerant speed in the refrigerant circuit is increased, the evaporation temperature Te of the outdoor heat exchanger 6 is lowered.
As mentioned above, in Embodiment 1, the frost formation state on the outdoor heat exchanger 6 is detected using the characteristic amount T1 shown in the equation (1). Thus, if the evaporation temperature Te is lowered, that is, a value of (Ta - Te), which is a numerator of the characteristic amount T1, is raised, the compressor frequency f, which is a denominator of the characteristic amount T1, is also raised. Therefore, if the evaporation temperature Te is lowered by the increase of the compressor frequency f, a rise (fluctuation) in the characteristic amount T1 can be suppressed.
Fig. 4 is a characteristic diagram illustrating a relationship between the characteristic amount T1 and an operation time of the compressor 3 in Embodiment 1 of the present invention. In Fig. 4, the vertical axis indicates the characteristic amount T1 and the horizontal axis indicates the operation time of the compressor 3, and a change with time of the characteristic amount T1 with respect to the operation time of the compressor 3 is illustrated.
If the evaporation temperature Te is lowered by the increase of the compressor frequency f during the heating operation, the characteristic amount T1 is not changed much, and as frost formation on the outdoor heat exchanger 6 increases with time, the characteristic amount T1 is raised gradually.
In the heat pump configured as above, since the characteristic amount T1 is used for detecting the frost formation state on the outdoor heat exchanger 6, that is, since the difference (Ta - Te) between the evaporator sucked air temperature Ta and the evaporation temperature Te is divided by the compressor frequency f, the frost formation state on the outdoor heat exchanger 6 can be accurately detected without being affected by a change in the compressor frequency in addition to a change in the outdoor environment.

Embodiment 2

In Embodiment 1, a frost formation state on the outdoor heat exchanger 6 is detected by the evaporation temperature Te of the outdoor heat exchanger 6, but since the evaporation temperature Te and the evaporation pressure of the outdoor heat exchanger 6 show similar changes, a frost formation state on the outdoor heat exchanger 6 can be detected by using the evaporation pressure of the outdoor heat exchanger 6. In Embodiment 2, those not particularly described are supposed to be the same as in Embodiment 1, and the same functions will be described using the same reference numerals.
Fig. 5 is an outline configuration diagram of a refrigerant circuit of an air conditioner using the heat pump in Embodiment 2 of the present invention. In Embodiment 2, instead of the evaporator refrigerant saturation temperature detecting means 10 in Embodiment 1, evaporator refrigerant pressure detecting means 13 for detecting a refrigerant pressure (evaporation pressure in a heating operation) of the outdoor heat exchanger 6 is provided in the refrigerant circuit.
Fig. 6 is a configuration block diagram for detecting performance drop caused by a frost formation of the outdoor heat exchanger 6 using the heat pump in Embodiment 2 of the present invention. The control portion 100 is provided with the timer 101, the memory 102, the frost formation state detecting means 103 and the like. The timer 101 measures an operation time or the like. The memory 102 stores an evaporation pressure Pe, the evaporator sucked air temperature Ta, the compressor frequency f and the like detected by the evaporator refrigerant pressure detecting means 13, the evaporator sucked air temperature detecting means 11, and the compressor frequency detecting means 12, respectively. The frost formation state detecting means 103 calculates a characteristic amount T2, which will be described later, using an evaporation temperature Tep calculated from the evaporation pressure Pe, the evaporator sucked air temperature Ta, and the compressor frequency f to detect a frost formation state on the outdoor heat exchanger 6. On the basis of information from the timer 101, the memory 102, the frost formation state detecting means 103 and the like, the control portion 100 sends a control signal to each driving portion of the compressor 3, the four-way valve 4, the outdoor heat exchanger fan 7, and the indoor heat exchanger fan 9.
Fig. 7 is a flowchart of defrosting start decision control of the air conditioner using the heat pump in Embodiment 2 of the present invention.
When the heating operation is started at step S-11, the frost formation state detecting means 103 performs calculation of the characteristic amount T2 as shown in the following equation at step S-12 from the evaporator sucked air temperature Ta detected by the evaporator sucked air temperature detecting means 11, the evaporation temperature Tep calculated from the evaporation pressure Pe detected by the evaporator refrigerant pressure detecting means 13, and the compressor frequency f detected by the compressor frequency detecting means 12: $T 2 = (Ta - Tep) / f$
A command value to be sent to the compressor 3 from the control portion 100 may be used as the compressor frequency f.
After that, at step S-13, the frost formation state detecting means 103 decides if the characteristic amount T2 exceeds a preset threshold value S2 or not. If the characteristic amount T2 exceeds the threshold value S2, the processing proceeds to step S-14, where the defrosting operation is started. If the characteristic amount T2 does not exceed the threshold value S2, the processing returns back to step S-12, where the above process is repeated.
As mentioned above, in Embodiment 2, the frost formation state on the outdoor heat exchanger 6 is detected using the characteristic amount T2 shown in the equation (2). Therefore, similarly to Embodiment 1, if the evaporation temperature Tep (evaporation pressure Pe) is lowered by the increase of the compressor frequency f, a rise (fluctuation) in the characteristic amount T2 can be suppressed.
Fig. 8 is a characteristic diagram illustrating a relation between a characteristic amount T2 and an operation time of the compressor 3 in Embodiment 2 of the present invention. In Fig. 8, the vertical axis indicates the characteristic amount T2 and the horizontal axis indicates the operation time of the compressor 3, and a change with time of the characteristic amount T2 with respect to the operation time of the compressor 3 is illustrated.
If the evaporation temperature Tep (evaporation pressure Pe) is lowered by the increase of the compressor frequency f during the heating operation, the characteristic amount T2 is not changed much, and as a frost formation on the outdoor heat exchanger 6 increases with time, the characteristic amount T2 is raised gradually.
In the heat pump configured as above, since the characteristic amount T2 is used for detecting the frost formation state on the outdoor heat exchanger 6, that is, since the difference (Ta - Tep) between the evaporator sucked air temperature Ta and the evaporation pressure Pe is divided by the compressor frequency f, a frost formation state on the outdoor heat exchanger 6 can be accurately detected without being affected by a change in the compressor frequency in addition to a change in the outdoor environment.

Embodiment 3

In Embodiment 1, a frost formation state on the outdoor heat exchanger 6 is detected using the characteristic amount T1, but the frost formation state on the outdoor heat exchanger 6 can be detected more accurately by using a time change amount of the characteristic amount T1. In Embodiment 3, those not particularly described are supposed to be the same as in the above embodiments, and the same functions will be described using the same reference numerals.
Fig. 9 is an outline configuration diagram of a refrigerant circuit of an air conditioner using the heat pump in Embodiment 3 of the present invention. In Embodiment 3, compressor operation time measuring means 14 for measuring a compressor operation time t of the compressor 3 is provided in addition to the refrigerant circuit of Embodiment 1.
Fig. 10 is a configuration block diagram for detecting performance drop caused by a frost formation of the outdoor heat exchanger 6 using the heat pump in Embodiment 3 of the present invention. The control portion 100 is provided with the timer 101, the memory 102, the frost formation state detecting means 103 and the like. The timer 101 measures an operation time or the like. The memory 102 stores an evaporation temperature Te, an evaporator sucked air temperature Ta, a compressor frequency f, and a compressor operation time t and the like detected by the evaporator refrigerant saturation temperature detecting means 10, the evaporator sucked air temperature detecting means 11, the compressor frequency detecting means 12, and the compressor operation time measuring means 14, respectively. The frost formation state detecting means 103 calculates the characteristic amount T1 at the compressor operation time t using the evaporation temperature Te, the evaporator sucked air temperature Ta, and the compressor frequency f to detect a frost formation state on the outdoor heat exchanger 6. On the basis of information from the timer 101, the memory 102, the frost formation state detecting means 103 and the like, the control portion 100 sends a control signal to each driving portion of the compressor 3, the four-way valve 4, the outdoor heat exchanger fan 7, and the indoor heat exchanger fan 9.
Fig. 11 is a flowchart of defrosting start decision control of the air conditioner using the heat pump in Embodiment 3 of the present invention.
When the heating operation is started at step S-21, the compressor operation time t is measured by the compressor operation time measuring device 14 at step S-22. At step S-23, the frost formation state detecting means 103 calculates the characteristic amount T1 shown by the equation (1) from the evaporator sucked air temperature Ta at the compressor operation time t detected by the evaporator sucked air temperature detecting means 11, the evaporation temperature Te detected by the evaporator refrigerant saturation temperature detecting means 10, and the compressor frequency f detected by the compressor frequency detecting means 12 and stores it in the memory 102. After that, at step S-24, it is decided if a change amount detection time D minutes (5 minutes, for example) set in advance elapsed or not. If the change amount detection time D minutes (5 minutes, for example) elapsed, the processing proceeds to step S-25, while if the time did not elapse, the processing returns back to step S-22, where the above process is repeated.
At step S-25, the frost formation state detecting means 103 calculates a value obtained by subtracting the characteristic amount T1(t - D) at a compressor operation time (t - D) from the characteristic amount T1(t) at the compressor operation time t, that is, T1(t) - T1(t - D), as the time change amount of the characteristic amount T1. If the time change amount of the characteristic amount T1 is larger than a threshold value S3, it is decided that the heating operation capacity is lowered by the frost formation on the outdoor heat exchanger 6, and the processing proceeds to step S-26, where the defrosting operation is started. If the time change amount of the characteristic amount T1 is smaller than the threshold value S3, it is decided that the heating operation capacity is not lowered by the frost formation on the outdoor heat exchanger 6, and the processing returns back to step S-22, where the heating operation is continued.
In Embodiment 3, the compressor operation time t is measured by the compressor operation time measuring means 14 but it may be measured by the timer 101. Also, the compressor frequency f is detected by the compressor frequency detecting means 12, but a command value sent from the control portion 100 to the compressor 3 may be used.
Fig. 12 is a characteristic diagram illustrating a relation between a time change amount of the characteristic amount T1 and an operation time of the compressor 3 in Embodiment 3 of the present invention. In Fig. 12, the vertical axis indicates the time change amount of the characteristic amount T1 and the horizontal axis indicates the operation time of the compressor 3, and a change with time of the time change amount of the characteristic amount T1 with respect to the operation time of the compressor 3 is illustrated.
As described in Embodiment 1, even if the evaporation temperature Te is lowered by the increase of the compressor frequency f, the characteristic amount T1 is not changed much. Thus, the time change amount of the characteristic amount T1 is not changed much, as well, if the evaporation temperature Te is lowered by the increase of the compressor frequency f, and as the frost formation on the outdoor heat exchanger 6 is increased as time elapses, the time change amount of the characteristic amount T1 is raised gradually.
In the heat pump configured as above, similarly to Embodiment 1, since the characteristic amount T1 is used for detecting a frost formation state on the outdoor heat exchanger 6, the frost formation state on the outdoor heat exchanger 6 can be detected accurately without being affected by the change in the compressor frequency in addition to that of the outdoor environment.
Also, since the time change amount of the characteristic amount T1 is used for detecting the frost formation state on the outdoor heat exchanger 6, even if detected values of the evaporator refrigerant saturation temperature detecting means 10, the evaporator sucked air temperature detecting means 11, and the compressor frequency detecting means 12 deviate by a secular change, the frost formation state on the outdoor heat exchanger 6 can be detected accurately.

Embodiment 4

In Embodiment 3, while a frost formation state of the outdoor heat exchanger 6 is detected using the time change amount of the characteristic amount T1, the frost formation state of the outdoor heat exchanger 6 can be also detected using the time change amount of the characteristic amount T2. In Embodiment 4, items not particularly described are supposed to be the same as those in the above embodiments, and the same functions will be described using the same reference numerals.
Fig. 13 is an outline configuration diagram of a refrigerant circuit of an air conditioner using a heat pump in Embodiment 4 of the present invention. In Embodiment 4, the compressor operation time measuring means 14 for measuring the compressor operation time t of the compressor 3 is provided in addition to the refrigerant circuit of Embodiment 2.
Fig. 14 is a configuration block diagram for detecting performance drop caused by a frost formation of the outdoor heat exchanger 6 using the heat pump in Embodiment 4 of the present invention. The control portion 100 is provided with the timer 101, the memory 102, the frost formation state detecting means 103 and the like. The timer 101 measures an operation time or the like. The memory 102 stores the evaporation pressure Pe, the evaporator sucked air temperature Ta, the compressor frequency f, the compressor operation time t and the like detected by the evaporator refrigerant pressure detecting means 13, the evaporator sucked air temperature detecting means 11, the compressor frequency detecting means 12, and the compressor operation time measuring means 14, respectively. The frost formation state detecting means 103 calculates the characteristic amount T2 at the compressor operation time t using the evaporation temperature Tep calculated from the evaporation pressure Pe, the evaporator sucked air temperature Ta, and the compressor frequency f to detect a frost formation state on the outdoor heat exchanger 6. On the basis of information from the timer 101, the memory 102, the frost formation state detecting means 103 and the like, the control portion 100 sends a control signal to each driving portion of the compressor 3, the four-way valve 4, the outdoor heat exchanger fan 7, and the indoor heat exchanger fan 9.
Fig. 15 is a flowchart of a defrosting start decision control of the air conditioner using the heat pump in Embodiment 4 of the present invention.
When the heating operation is started at step S-31, the compressor operation time t is measured by the compressor operation time measuring device 14 at step S-32. At step S-33, the frost formation state detecting means 103 calculates the characteristic amount T2 shown by the equation (2) from the evaporator sucked air temperature Ta at the compressor operation time t detected by the evaporator sucked air temperature detecting means 11, the evaporation temperature Tep calculated by the evaporation pressure Pe detected by the evaporator refrigerant pressure detecting means 13, and the compressor frequency f detected by the compressor frequency detecting means 12 and stores it in the memory 102. After that, at step S-34, it is decided if a change-amount detection time D minutes (5 minutes, for example) set in advance elapsed or not. If the change-amount detection time D minutes (5 minutes, for example) elapsed, the processing goes on to step S-35. If the time did not elapse, the processing returns back to step S-32, where the above process is repeated.
At step S-35, the frost formation state detecting means 103 calculates a value obtained by subtracting the characteristic amount T2(t - D) at a compressor operation time (t - D) from the characteristic amount T2(t) at the compressor operation time t, that is, T2(t) - T2(t - D), as the time change amount of the characteristic amount T2. If the time change amount of the characteristic amount T2 is larger than a threshold value S4, it is decided that the heating operation capacity is lowered by the frost formation on the outdoor heat exchanger 6, and the processing goes on to step S-36, where the defrosting operation is started. If the time change amount of the characteristic amount T2 is smaller than the threshold value S4, it is decided that the heating operation capacity is not lowered by the frost formation on the outdoor heat exchanger 6, and the processing returns back to step S-32, where the heating operation is continued.
In Embodiment 4, the compressor operation time t is measured by the compressor operation time measuring means 14 but it may be measured by the timer 101. Also, the compressor frequency f is detected by the compressor frequency detecting means 12, but a command value sent from the control portion 100 to the compressor 3 may be used.
Fig. 16 is a characteristic diagram illustrating a relation between a time change amount of the characteristic amount T2 and an operation time of the compressor 3 in Embodiment 4 of the present invention. In Fig. 16, the vertical axis indicates the time change amount of the characteristic amount T2 and the horizontal axis indicates the operation time of the compressor 3, and a change with time of the time change amount of the characteristic amount T2 with respect to the operation time of the compressor 3 is illustrated.
As described in Embodiment 2, even if the evaporation temperature Te is lowered by the increase of the compressor frequency f, the characteristic amount T2 is not changed much. Thus, the time change amount of the characteristic amount T2 is not changed much, as well, if the evaporation temperature Te is lowered by the increase of the compressor frequency f, and as the frost formation on the outdoor heat exchanger 6 is increased as time elapses, the time change amount of the characteristic amount T2 is raised gradually.
In the heat pump configured as above, similarly to Embodiment 2, since the characteristic amount T2 is used for detecting a frost formation state on the outdoor heat exchanger 6, the frost formation state on the outdoor heat exchanger 6 can be detected accurately without being affected by the change in the compressor frequency in addition to a change in the outdoor environment.
Also, since the time change amount of the characteristic amount T2 is used for detecting the frost formation state on the outdoor heat exchanger 6, similarly to Embodiment 3, even if detected values on the evaporator refrigerant pressure detecting means 13, the evaporator sucked air temperature detecting means 11, and the compressor frequency detecting means 12 deviate by a secular change, the frost formation state on the outdoor heat exchanger 6 can be detected accurately.

Embodiment 5

In an environment in which the evaporator sucked air temperature detecting means 11 is covered with snow, for example, and cannot detect the evaporator sucked air temperature Ta (environment in which the evaporator sucked air temperature Ta is falsely detected), a frost formation state on the outdoor heat exchanger 6 can be detected accurately by the means shown in Embodiment 5. In Embodiment 5, items not particularly described are supposed to be the same as those in the above embodiments, and the same functions will be described using the same reference numerals.
Fig. 17 is an outline configuration diagram of a refrigerant circuit of an air conditioner using a heat pump in Embodiment 5 of the present invention. In Embodiment 5, the evaporator sucked air temperature detecting means 11 for detecting the evaporator sucked air temperature Ta and the compressor frequency detecting means 12 for detecting the compressor frequency f are removed from the refrigerant circuit of Embodiment 3.
Fig. 18 is a configuration block diagram for detecting performance drop caused by a frost formation of the outdoor heat exchanger 6 using the heat pump in Embodiment 5 of the present invention. The control portion 100 is provided with the timer 101, the memory 102, the frost formation state detecting means 103 and the like. The timer 101 measures an operation time or the like. The memory 102 stores the evaporation temperature Te, the compressor operation time t and the like detected by the evaporator refrigerant saturation temperature detecting means 10 and the compressor operation time measuring means 14, respectively. The frost formation state detecting means 103 calculates a time change amount of a characteristic amount T3, which will be described later, or the like to detect a frost formation state on the outdoor heat exchanger 6. On the basis of information from the timer 101, the memory 102, the frost formation state detecting means 103 and the like, the control portion 100 sends a control signal to each driving portion of the compressor 3, the four-way valve 4, the outdoor heat exchanger fan 7, and the indoor heat exchanger fan 9.
Fig. 19 is a flowchart of defrosting start decision control of the air conditioner using the heat pump in Embodiment 5 of the present invention.
When the heating operation is started at step S-41, the compressor operation time t is measured by the compressor operation time measuring device 14 at step S-42. At step S-43, the frost formation state detecting means 103 sets the evaporation temperature Te at the compressor operation time t detected by the evaporator refrigerant saturation temperature detecting means 10 to be a characteristic amount T3, T3 = Te, and stores it in the memory 102. After that, at step S-44, it is decided if a change-amount detection time D minutes (5 minutes, for example) set in advance elapsed or not. If the change-amount detection time D minutes (5 minutes, for example) elapsed, the processing goes on to step S-45. If the time did not elapse, the processing returns back to step S-42, where the above process is repeated.
At step S-45, the frost formation state detecting means 103 calculates a value obtained by subtracting the characteristic amount T3(t) at a compressor operation time t from the characteristic amount T3(t - D) at the compressor operation time (t - D), that is, T3(t - D) - T3(t), as the time change amount of the characteristic amount T3. If the time change amount of the characteristic amount T3 is larger than a threshold value S5, it is decided that the heating operation capacity is lowered by the frost formation on the outdoor heat exchanger 6, and the processing goes on to step S-46, where the defrosting operation is started. If the time change amount of the characteristic amount T3 is smaller than the threshold value S5, it is decided that the heating operation capacity is not lowered by the frost formation on the outdoor heat exchanger 6, and the processing returns back to step S-42, where the heating operation is continued.
In Embodiment 5, the compressor operation time t is measured by the compressor operation time measuring means 14 but it may be measured by the timer 101.
Fig. 20 is a characteristic diagram illustrating a relation between a time change amount of the characteristic amount T3 and an operation time of the compressor 3 in Embodiment 5 of the present invention. In Fig. 20, the vertical axis indicates the time change amount of the characteristic amount T3 and the horizontal axis indicates the operation time of the compressor 3, and a change with time of the time change amount of the characteristic amount T3 with respect to the operation time of the compressor 3 is illustrated.
As frost formation on the outdoor heat exchanger 6 is increased as time elapses, the time change amount of the characteristic amount T3 is raised gradually.
In the heat pump configured as above, since the evaporator sucked air temperature Ta is not included in the calculation of the characteristic amount T3 used for detecting a frost formation state on the outdoor heat exchanger 6, the frost formation state on the outdoor heat exchanger 6 can be accurately detected under an environment in which the evaporator sucked air temperature Ta cannot be detected due to snow coverage or the like (environment in which the evaporator sucked air temperature Ta is falsely detected).
Also, since the time change amount of the characteristic amount T3 is used for detecting the frost formation state on the outdoor heat exchanger 6, even if a detected value of the evaporator refrigerant saturation temperature detecting means 10 deviates by a secular change, the frost formation state on the outdoor heat exchanger 6 can be detected accurately.

Embodiment 6

In Embodiment 5, the evaporation temperature Te of the outdoor heat exchanger 6 is used for detecting a frost formation state on the outdoor heat exchanger 6, but since the evaporation temperature Te of the outdoor heat exchanger 6 and the evaporation pressure show the same change, the frost formation state on the outdoor heat exchanger 6 can be also detected using the evaporation pressure of the outdoor heat exchanger 6. In Embodiment 5, items not particularly described are supposed to be the same as those in the above embodiments, and the same functions will be described using the same reference numerals.
Fig. 21 is an outline configuration diagram of a refrigerant circuit of an air conditioner using the heat pump in Embodiment 6 of the present invention. In Embodiment 6, instead of the evaporator refrigerant saturation temperature detecting means 10 in Embodiment 5, the evaporator refrigerant pressure detecting means 13 for detecting a refrigerant pressure (evaporation pressure in a heating operation) of the outdoor heat exchanger 6 is provided in the refrigerant circuit.
Fig. 22 is a configuration block diagram for detecting performance drop caused by a frost formation of the outdoor heat exchanger 6 using the heat pump in Embodiment 6 of the present invention. The control portion 100 is provided with the timer 101, the memory 102, the frost formation state detecting means 103 and the like. The timer 101 measures an operation time or the like. The memory 102 stores an evaporation pressure Pe, the compressor operation time t and the like detected by the evaporator refrigerant pressure detecting means 13 and the compressor operation time measuring means 14, respectively. The frost formation state detecting means 103 calculates a time change amount of a characteristic amount T4, which will be described later, or the like to detect a frost formation state on the outdoor heat exchanger 6. On the basis of information from the timer 101, the memory 102, the frost formation state detecting means 103 and the like, the control portion 100 sends a control signal to each driving portion of the compressor 3, the four-way valve 4, the outdoor heat exchanger fan 7, and the indoor heat exchanger fan 9.
Fig. 23 is a flowchart of defrosting start decision control of the air conditioner using the heat pump in Embodiment 6 of the present invention.
When the heating operation is started at step S-51, the compressor operation time t is measured by the compressor operation time measuring device 14 at step S-52. At step S-53, the frost formation state detecting means 103 sets the evaporation pressure Pe detected by the evaporator refrigerant pressure detecting means 13 at the compressor operation time t to a characteristic amount T4 = Pe and stores it in the memory 102. After that, at step S-54, it is decided if a change-amount detection time D minutes (5 minutes, for example) set in advance elapsed or not. If the change-amount detection time D minutes (5 minutes, for example) elapsed, the processing goes on to step S-55. If the time did not elapse, the processing returns back to step S-52, where the above process is repeated.
At step S-55, the frost formation state detecting means 103 calculates a value obtained by subtracting the characteristic amount T4(t) at a compressor operation time t from the characteristic amount T4(t - D) at the compressor operation time (t - D), that is, T4(t - D) - T4(t) as the time change amount of the characteristic amount T4. If the time change amount of the characteristic amount T4 is larger than a threshold value S6, it is decided that the heating operation capacity is lowered by the frost formation on the outdoor heat exchanger 6, and the processing goes on to step S-56, where the defrosting operation is started. If the time change amount of the characteristic amount T4 is smaller than the threshold value S6, it is decided that the heating operation capacity is not lowered by the frost formation on the outdoor heat exchanger 6, and the processing returns back to step S-52, where the heating operation is continued.
In Embodiment 6, the compressor operation time t is measured by the compressor operation time measuring means 14 but it may be measured by the timer 101.
Fig. 24 is a characteristic diagram illustrating a relation between a time change amount of the characteristic amount T4 and an operation time of the compressor 3 in Embodiment 6 of the present invention. In Fig. 24, the vertical axis indicates the time change amount of the characteristic amount T4 and the horizontal axis indicates the operation time of the compressor 3, and a change with time of the time change amount of the characteristic amount T4 with respect to the operation time of the compressor 3 is illustrated.
As frost formation on the outdoor heat exchanger 6 is increased as time elapses, the time change amount of the characteristic amount T4 is raised gradually.
In the heat pump configured as above, since the evaporator sucked air temperature Ta is not included in the calculation of the characteristic amount T4 used for detecting a frost formation state on the outdoor heat exchanger 6, the frost formation state on the outdoor heat exchanger 6 can be accurately detected under an environment in which the evaporator sucked air temperature Ta cannot be detected due to snow coverage or the like (environment in which the evaporator sucked air temperature Ta is falsely detected).
Also, since the time change amount of the characteristic amount T4 is used for detecting the frost formation state on the outdoor heat exchanger 6, even if a detected value of the evaporator refrigerant pressure detecting means 13 deviates by a secular change, the frost formation state on the outdoor heat exchanger 6 can be detected accurately.
In Embodiments 3 to 6, the time change amount of the characteristic amount T(1 to 4) is set as a difference between a current characteristic amount T(t) and a characteristic amount T(t - D) before a change-amount detection time D minutes (5 minutes, for example). This is because malfunctions can be prevented caused by a temperature change in an outside-air in the case of a frost formation over a long time, but if a frost formation state can be detected accurately, D is not particularly limited but it may be 4 minutes or 10 minutes, for example.
Also, the time change amount of the characteristic amount T may be a difference between a characteristic amount T(t - D) before a certain reference time (20 minutes after start of the compressor 3, for example) and a current characteristic amount T(t). As a result, even in the case of a frost formation in a short time, a difference in the change amount values between no frost-formation and frost formation can be made large, which enables an accurate decision. The reference time of 20 minutes, for example, is set since it is confirmed that a refrigerating cycle is sufficiently stable and detection of a frost formation state is possible, but if the refrigerating cycle is sufficiently stable and detection of the frost formation state is possible, the reference time may be 10 minutes or 30 minutes, for example.

Embodiment 7

In Embodiments 1 to 6, detection of a frost formation state on the outdoor heat exchanger 6 is started immediately after the start of the compressor 3 (start of the heating operation), but by starting the detection of a frost formation state on the outdoor heat exchanger 6 after a certain time elapsed (th) from the start of the compressor 3, a frost-formation state decision in a state in which the refrigerating cycle is unstable due to pull-down can be avoided, and malfunction of the defrosting operation can be prevented. Though any of the configurations of Embodiments 1 to 6 can be used, the configuration of Embodiment 3 will be used in the following explanation of Embodiment 7. Items not particularly described are supposed to be the same as those in the above embodiments, and the same functions will be described using the same reference numerals.
Fig. 25 is a flowchart of the defrosting start decision control of an air conditioner using a heat pump in Embodiment 7 of the present invention.
When the heating operation is started at step S-21, the compressor operation time t is measured by the compressor operation time measuring means 14 at step S-22. At step S-22-1, it is decided whether the compressor operation time t exceeds a defrosting non-operation time th set in advance. If t exceeds th, the processing goes to step S-23. If not, the processing returns back to step S-22, where the above process is repeated.
At step S-23, the frost formation state detecting means 103 calculates the characteristic amount T1 shown by the equation (1) from the evaporator sucked air temperature Ta detected by the evaporator sucked air temperature detecting means 11 at the compressor operation time t, the evaporation temperature Te detected by the evaporator refrigerant saturation temperature detecting means 10, and the compressor frequency f detected by the compressor frequency detecting means 12 and stores it in the memory 102. After that, at step S-24, it is determined if the change-amount detection time D minutes (5 minutes, for example) set in advance elapsed or not. If the change-amount detection time D minutes (5 minutes, for example) elapsed, the processing goes on to step S-25. If the time did not elapse, the processing returns back to step S-23, where the above process is repeated.
At step S-25, the frost formation state detecting means 103 calculates a value obtained by subtracting the characteristic amount T1(t - D) at a compressor operation time (t - D) from the characteristic amount T1(t) at the compressor operation time t, that is, T1(t) - T1(t - D), as the time change amount of the characteristic amount T1. If the time change amount of the characteristic amount T1 is larger than a threshold value S3, it is decided that the heating operation capacity is lowered by the frost formation on the outdoor heat exchanger 6, and the processing goes on to step S-26, where the defrosting operation is started. If the time change amount of the characteristic amount T1 is smaller than the threshold value S3, it is decided that the heating operation capacity is not lowered by the frost formation on the outdoor heat exchanger 6, and the processing returns back to step S-22, where the heating operation is continued.
Fig. 26 is a characteristic diagram illustrating a relation between a time change amount of the characteristic amount T1 and an operation time of the compressor 3 when the air conditioner in Embodiment 7 of the present invention is in a pull-down operation. In Fig. 26, the vertical axis indicates the time change amount of the characteristic amount T1 and the horizontal axis indicates the operation time of the compressor 3, and a change with time of the time change amount of the characteristic amount T1 with respect to the operation time of the compressor 3 is illustrated. For example, if a temperature difference between an indoor temperature and a set temperature at start of the heating operation is equal to or greater than a certain temperature, that is, if the indoor temperature is lower than the set temperature by a certain temperature or more, the air conditioner performs the pull-down operation in which the frequency of the compressor 3 is temporarily raised and indoor heating is quickly conducted. At this time, the evaporation temperature Te is rapidly lowered (the characteristic amount T1 is rapidly raised), that is, the time change amount of the characteristic amount T1 is rapidly raised, and the time change amount of the characteristic amount T1 temporarily shows an overshoot as shown in Fig. 26. However, in Embodiment 7, since the time change amount of the characteristic amount T1 is detected after the defrosting non-operation time th elapsed, false detection can be prevented of a frost formation state on the outdoor heat exchanger 6 by the temporary overshoot of the time change amount of the characteristic amount T1 in the pull-down operation.
Also, the defrosting non-operation time th is not made to be a predetermined certain time, but a next defrosting non-operation time th_next may be determined on the basis of a defrosting operation time(t_def) before a heating operation.
Fig. 27 is a flowchart for determining the next defrosting non-operation time th_next. When a defrosting operation is started at step S-61, it is decided if the defrosting operation is to be finished or not at step S-62. If it is decided that the defrosting operation is to be finished, the processing goes on to step S-63. If it is determined that the defrosting operation is not to be finished, the processing returns back to step S-62, where the above process is repeated.
When the defrosting operation is finished at step S-63, the defrosting operation time t_def is measured by the timer 101 at step S-64. At step S-65, the next defrosting non-operation time th_next is calculated on the basis of the defrosting operation time t_def. After that, the processing goes onto step S-66, where the heating operation is started.
As mentioned above, by calculating the next defrosting non-operation time th_next, detection accuracy of the frost formation state can be improved without performing an unnecessary defrosting operation. Moreover, since the defrosting non-operation time th according to an installation environment of the outdoor unit 1 can be calculated, drop of the heat exchange performance of the outdoor heat exchanger 6 caused by too long defrosting non-operation time th can be prevented.

Embodiment 8

In Embodiments 1 to 7, the defrosting operation is started when the characteristic amount T or the time change amount of the characteristic amount T exceeds a certain threshold value S, but the defrosting operation may be started if a state in which the threshold value S is exceeded lasts for a predetermined time (X minutes). Though any of the configurations of Embodiments 1 to 7 is applicable, the configuration of Embodiment 3 will be used in the following explanation of Embodiment 8. Items not particularly described are supposed to be the same as those in the above embodiments, and the same functions will be described using the same reference numerals.
Fig. 28 is a configuration block diagram illustrating detection of performance drop of the outdoor heat exchanger 6 caused by frost formation using the heat pump in Embodiment 8 of the present invention. The control portion 100 is provided with the timer 101, the memory 102, the frost formation state detecting means 103, defrosting allowing means 104 and the like. The timer 101 measures an operation time or the like. The memory 102 stores the evaporation temperature Te, the evaporator sucked air temperature Ta, the compressor frequency f, the compressor operation time t and the like detected by the evaporator refrigerant saturation temperature detecting means 10, the evaporator sucked air temperature detecting means 11, the compressor frequency detecting means 12, and the compressor operation time measuring means 14, respectively. The frost formation state detecting means 103 calculates the characteristic amount T1 at the compressor operation time t using the evaporation temperature Te, the evaporator sucked air temperature Ta, and the compressor frequency f to detect a frost formation state of the outdoor heat exchanger 6. Defrosting allowing means 104 allows a defrosting operation on the basis of detection results of the frost formation state detecting means. On the basis of information from the timer 101, the memory 102, the frost formation state detecting means 103, the defrosting allowing means 104 and the like, the control portion 100 sends a control signal to each driving portion of the compressor 3, the four-way valve 4, the outdoor heat exchanger fan 7, and the indoor heat exchanger fan 9.
Fig. 29 is a flowchart of defrosting start decision control of the air conditioner using the heat pump in Embodiment 8 of the present invention.
When the heating operation is started at step S-21, the compressor operation time t is measured by the compressor operation time measuring device 14 at step S-22. At step S-23, the frost formation state detecting means 103 calculates the characteristic amount T1 shown by the equation (1) from the evaporator sucked air temperature Ta at the compressor operation time t detected by the evaporator sucked air temperature detecting means 11, the evaporation temperature Te detected by the evaporator refrigerant saturation temperature detecting means 10, and the compressor frequency f detected by the compressor frequency detecting means 12 and stores it in the memory 102. After that, at step S-24, it is decided if a change-amount detection time D minutes (5 minutes, for example) set in advance elapsed or not. If the change-amount detection time D minutes (5 minutes, for example) elapsed, the processing goes on to step S-25. If not, the processing returns back to step S-22, where the above process is repeated.
At step S-25, the frost formation state detecting means 103 calculates a value obtained by subtracting the characteristic amount T1(t - D) at a compressor operation time (t - D) from the characteristic amount T1(t) at the compressor operation time t, that is, T1(t) - T1(t - D), as a time change amount of the characteristic amount T1 and decides if the time change amount of the characteristic amount T1 is larger than a threshold value S3 or not. Also, the defrosting allowing means 104 decision whether a state in which the time change amount of the characteristic amount T1 is larger than the threshold value S3 continues for equal to or larger than a frost formation decision time (X minutes) set in advance. If the state in which the time change amount of the characteristic amount T1 is larger than the threshold value S3 continues for equal to or larger than the frost formation decision time (X minutes), it is decided that the heating capacity is lowered by frost formation on the outdoor heat exchanger 6, and the processing goes on to step S-26, where the defrosting operation is started. If the state in which the time change amount of the characteristic amount T1 is larger than the threshold value S3 does not continue for equal to or larger than the frost formation decision time (X minutes), it is decided that the heating capacity is not lowered by frost formation on the outdoor heat exchanger 6, and the processing returns to step S-22, where the heating operation is continued.
In Embodiment 8, the compressor operation time t is measured by the compressor operation time measuring means 14 but it may be measured by the timer 101. Also, the compressor frequency f is detected by the compressor frequency detecting means 12, but a command value sent from the control portion 100 to the compressor 3 may be used.
For example, when a blast mode of the indoor unit is made to be a strong mode and an indoor temperature and a set temperature are far from each other, the control potion 100 raises the frequency of the indoor heat exchanger fan 9. By the increase of the frequency of the indoor heat exchanger fan 9, a heat exchange between the indoor heat exchanger 8 and air sent from the indoor heat exchanger fan 9 to the indoor heat exchanger 8 is promoted, a condensation temperature of the indoor heat exchanger 8 is lowered, and with the drop of the condensation temperature, the evaporation temperature Te of the outdoor heat exchanger 6 is also temporarily lowered.
Also, a detected value of the evaporation temperature Te of the outdoor heat exchanger 6 might also be temporarily lowered due to a noise or the like.
As mentioned above, in Embodiment 8, if the state in which the time change amount of the characteristic amount T1 is larger than the threshold value S3 continues for equal to or larger than the frost formation determination time (X minutes) set in advance, it is decided that the heating capacity is lowered by a frost formation on the outdoor heat exchanger 6. Thus, even if the evaporation temperature Te is temporarily lowered, false detection that the heating capacity is lowered by the frost formation on the outdoor heat exchanger 6 can be prevented.
In the heat pump configured as above, since it is determined that heating capacity drops due to a frost formation on the outdoor heat exchanger 6 when the state in which the time change amount of the characteristic amount T1 is larger than the threshold value S3 continues for equal to or larger than the frost formation determination time (X minutes) set in advance, even if the evaporation temperature Te is temporarily lowered by changes in the operation state, noise or the like, false judgment that the heating capacity is lowered by the frost formation on the outdoor heat exchanger 6 is not made and a frost formation state can be detected accurately.

Embodiment 9

In Embodiments 1 to 8, a frost formation state on the outdoor heat exchanger 6 is indirectly detected on the basis of the evaporation temperature or the like, but by using second frost formation state detecting means for directly detecting a frost formation state of the outdoor heat exchanger 6 at the same time, the frost formation state on the outdoor heat exchanger 6 can be detected more accurately.
Fig. 30 is an outline configuration diagram illustrating an example of the second frost formation state detecting means in Embodiment 9.
An optical frost formation sensor 21 is constituted by a light emitting portion 21a of an optical sensor such as an LED and a light receiving portion 21b. The light emitting portion 21a emits light toward a fin 6a of the outdoor heat exchanger 6, and the light reflected by the fin 6a is received by the light receiving portion 21b. In Embodiment 9, a light emission amount from the light emitting portion 21a, that is, an output voltage of the light emitting portion 21a is controlled by a light-amount decision control portion 22 so that a light receiving amount by the light receiving portion 21b is made constant.
Fig. 31 is a characteristic diagram illustrating a relation between an output voltage [V] of a light emitting portion 21a and an operation time. In Fig. 31, the vertical axis indicates the output voltage [V] of the light emitting portion 21a and the horizontal axis indicates an operation time of the compressor 3 to illustrate a change over time of the output voltage [V] of the light emitting portion 21a.
When the compressor 3 starts operation, frost begins to form on the fin 6a of the outdoor heat exchanger 6. The light emitted by the light emitting portion 21a toward the fin 6a is diffused by the frost and the light receiving amount of the light receiving portion 21b is decreased. Thus, the output voltage of the light emitting portion 21a is increased so that the light receiving amount of the light receiving portion 21b becomes constant. By the increase of the output voltage of the light emitting portion 21a, the frost formation state on the outdoor heat exchanger 6 can be directly directed. It may be so configured that the output voltage of the light emitting portion 21a is made constant, and the frost formation state on the outdoor heat exchanger 6 is detected by a decrease in the light receiving amount of the light receiving portion 21b.
Also, it may be so configured that an electrode is installed at a position in contact with frost adhering to the outdoor heat exchanger 6 to make it second frost formation state detecting means.
Fig. 32 is a characteristic diagram illustrating a relation between capacitance [F] between a fin and an electrode of the outdoor heat exchanger 6 and an operation time of the compressor 3 in Embodiment 9. In Fig. 32, the horizontal axis indicates the capacitance [F] and the lateral axis indicates an operation time of the compressor 3 to show a change with time in the capacitance [F] with respect to the operation time of the compressor 3. In Embodiment 9, another electrode of the electrode is made as a fin of the outdoor heat exchanger 6, and the capacitance between the both electrodes is measured.
As shown in Fig. 32, when the compressor 3 starts operation, frost begins to form on the fin of the outdoor heat exchanger 6. As a thickness of the frost adhering to the fin of the outdoor heat exchanger 6, the capacitance [F] between the fin and the electrode of the outdoor heat exchanger 6 is decreased. By the decrease in the capacitance [F], the frost formation state on the outdoor heat exchanger 6 can be directly detected.
Also, radiation temperature detecting means may be installed for measuring a radiation temperature (frost layer surface temperature) on the surface of the outdoor heat exchanger 6 as second frost formation state detecting means.
Fig. 33 is a characteristic diagram illustrating a relation between a radiation temperature (frost layer surface temperature) [°C] on the surface of the outdoor heat exchanger 6 and an operation time of the compressor 3 in Embodiment 9 of the present invention. In Fig. 33, an evaporation temperature of the outdoor heat exchanger 6 is also shown.
As shown in Fig. 33, when the compressor 3 starts operation, frost begins to form on the fin of the outdoor heat exchanger 6. As a frost formation range in a measurement range of the radiation temperature (frost layer surface temperature) increases, the radiation temperature (frost layer surface temperature) rises. By the increase of the radiation temperature (frost layer surface temperature), the frost formation state of the outdoor heat exchanger 6 can be directly detected.
In Embodiment 1 to 9, the air conditioner using the heat pump of the present invention is shown, but it is needless to say that the heat pump of the present invention can be used for a water heater.
Also, various sensors can be used for detecting means for pressure and temperature.
Also, the control portion 100 in each embodiment is constituted by a CPU, a microcomputer and the like in which each of the frost formation state detecting means 103 is programmed.

Claims

A heat pump having a refrigerant circuit in which a compressor (3), a condenser (8), an expansion valve (5), and an evaporator (6) are connected sequentially, comprising:
evaporator refrigerant saturation temperature detecting means (10) for detecting an evaporation temperature of said evaporator (6); and

first frost formation state detecting means (103) for detecting a frost formation state of said evaporator (6), wherein

said first frost formation state detecting means (103) sets said evaporation temperature to a characteristic amount and

detects a drop in heat exchange performance caused by frost formation on said evaporator (6) on the basis of a time change amount of the characteristic amount, wherein the time change amount is a difference in said characteristic amount before and after a given time elapsed, and when the characteristic amount is defined as T, a compressor operation time is defined as t, and a change-amount detection time is defined as D, the time change amount is calculated by subtracting the characteristic amount T(t) at the compressor operation time t from the characteristic amount T(t - D) at the compressor operation time (t - D), that is, T(t - D) - T(t).
The heat pump of claim 1, wherein said first frost formation state detecting means (103) detects a frost formation state on said evaporator (6) after an operation time of said compressor (3) elapsed for a predetermined time.
The heat pump of claim 2, wherein, in an operation after a defrosting operation started and finished, said first frost formation state detecting means (103) is configured to determine
said predetermined time on the basis of said defrosting operation time; and to detect the frost formation state on said evaporator (6) again

after said predetermined time has elapsed.
The heat pump of any one of claims 1 to 3, comprising defrosting allowing means(104) for allowing a defrosting operation on the basis of detection results of said first frost formation state detecting means (103).
The heat pump of claim 4, wherein said defrosting allowing means (104) allows defrosting when a state in which said characteristic amount exceeds a predetermined threshold value continues for equal to or larger than a frost formation determination time.
The heat pump of any one of claims 1 to 5, comprising second frost formation state detecting means for detecting a frost formation state of said evaporator (6) by a light emitting portion (21a) for emitting light toward said evaporator (6) and a light receiving portion (21b) for receiving light reflected by said evaporator (6), wherein the heat pump is configured such that
the drop in heat exchange performance caused by frost formation on said evaporator (6) is detected on the basis of an output of at least either one of said first frost formation state detecting means (103) or said second frost formation state detecting means.
The heat pump of any one of claims 1 to 5, comprising second frost formation state detecting means for detecting a thickness of frost by measuring changes in capacitance by an electrode, said electrode being provided at a position in contact when frost formed on said evaporator (6) reaches a predetermined thickness, wherein the heat pump is configured such that
the drop in heat exchange performance caused by frost formation on said evaporator (6) is detected on the basis of an output of at least either one of said first frost formation state detecting means (103) or said second frost formation state detecting means.
The heat pump of any one of claims 1 to 5, comprising:
radiation temperature detecting means for measuring a radiation temperature of said evaporator (6); and

second frost formation state detecting means for detecting a frost formation state on said evaporator (6) by said radiation temperature, wherein the heat pump is configured such that

the drop in heat exchange performance caused by frost formation on said evaporator (6) is detected on the basis of an output of at least either one of said first frost formation state detecting means (103) and said second frost formation state detecting means.
An air conditioner comprising the heat pump of any one of claims 1 to 8.
A water heater comprising the heat pump of any one of claims 1 to 8.