JPH0719575A - Air conditioner - Google Patents

Abstract

PURPOSE:To obtain an air conditioner impairing neither comfortableness of air conditioning nor the reliability of a compressor by a system wherein a control device controls the operational frequency of the compressor in accordance with a temperature difference between the temperature of condensation of a prescribed time before and the current temperature of condensation. CONSTITUTION:At the time of a heating operation, a compressor 2 is controlled so that the operational frequency thereof be lowered by a predetermined lowering range for each temperature difference on the basis of a difference of the temperature of condensation of a refrigerant in an indoor heat exchanger 5 from the one of a prescribed time before. In other words, a control device 8 obtains the temperature difference varying in accordance with a state of change of the temperature of condensation, selects the range of lowering of the operational frequency determined for each temperature difference beforehand, according to the obtained temperature difference, and varies the range of lowering of the operational frequency in accordance with the change of the temperature of condensation. On the occasion when the temperature of condensation is made a required value, therefore, the required temperature of condensation can be attained while the fluctuation of the operational frequency for operation of the compressor 2 is made not to be large.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air conditioner having a compressor operated at a variable operating frequency and capable of heating operation.

[0002]

2. Description of the Related Art Conventionally, there is an air conditioner capable of performing a cooling operation and a heating operation, respectively, by changing the flow direction of refrigerant in a refrigeration cycle. When performing a heating operation in such an air conditioner, the room temperature is controlled by changing the operating frequency of the compressor based on the temperature value detected by the room temperature sensor of the indoor unit normally installed in the air-conditioned room. When the condensation temperature of the refrigerant in the indoor heat exchanger becomes higher than the preset temperature, the operating frequency of the compressor is stepped down by the predetermined frequency set in the range where the condensation temperature decreases in advance. Then, control was performed so that the condensation temperature was lowered by lowering the operating frequency.

That is, as shown in the diagram for explaining the control shown in FIG. 5, in the region A while the condensation temperature Tc of the refrigerant in the indoor heat exchanger rises to the first temperature T ₁ = 55 ° C., for example,
The room temperature is controlled based on the temperature measured by the room temperature sensor in normal times. Further, in the B range where the condensing temperature Tc is 55 ° C. or higher, control is performed in two steps so that the operating frequency f of the compressor is lowered by a predetermined frequency Δf so that the condensing temperature Tc is lowered. The condensing temperature Tc is the first temperature T ₁ = 5.
In the C region while the second temperature T ₂ = 51 ° C. is decreased from 5 ° C., the operating frequency f of the compressor is maintained at the operating frequency as it is. Further, the condensation temperature Tc is the second temperature T ₂ = 5.
In the area A when the temperature becomes lower than 1 ° C., the room temperature is controlled again based on the temperature value detected by the room temperature sensor in the normal state.

The change in the operating frequency f and the condensation temperature Tc in this control is as shown in the characteristic diagram of FIG. According to this, the condensing temperature Tc starts operating and rises after being controlled in the A region, and when the condensing temperature Tc becomes 55 ° C. or higher, the control is performed in the B region and detected by the temperature sensor provided in the indoor heat exchanger. The operating frequency f of the compressor is controlled so as to be reduced by two steps based on the temperature value.

The condensing temperature Tc starts to decrease as the operating frequency f is decreased by the predetermined frequency Δf. The condensing temperature Tc decreases to 51 ° C. by continuing the operation with the operating frequency f lowered into the C range. Here, the normal control of the region A is performed again, the operating frequency f of the compressor is stepped up, and the condensing temperature Tc also rises accordingly. And the condensation temperature Tc is 55 ° C.
As a result of the above, the above control is repeated and continues until the condensation temperature Tc stabilizes at 55 ° C. or lower.

However, in the above prior art,
A predetermined operating temperature f of the compressor is determined by detecting whether the condensation temperature Tc of the refrigerant in the indoor heat exchanger has reached a preset first temperature T ₁ , for example, 55 ° C. or higher. Since the control is performed so as to uniformly step down by the frequency Δf, the operating frequency f fluctuates significantly, the air conditioning capacity decreases, and the room temperature fluctuations in the air-conditioned room also increase greatly. It was a loss of sex.

Further, there is a response delay in the temperature detection by the temperature sensor, and there is a difference between the detected temperature and the actual condensation temperature Tc when the control is performed based on this, so that a predetermined frequency Δf is set in advance. The step-down value of 1 must also be set so that the operating frequency f actually drops below the required value. Therefore, the operating frequency f decreases in the C region between the first temperature T ₁ = 55 ° C. and the second temperature T ₂ = 51 ° C. when the condensing temperature Tc decreases without continuing the holding state. Condensing temperature Tc is 51 ℃
Under the following conditions, the room temperature was further changed.

Furthermore, the compressor is repeatedly operated at an operating frequency f that decreases and rises every time the condensing temperature Tc of the refrigerant becomes equal to or higher than the preset first temperature T _1. And overheating will be repeated. Then, the reliability of the compressor is impaired by continuing such operation.

[0009]

SUMMARY OF THE INVENTION As described above, conventionally,
If the condensing temperature of the refrigerant may exceed the set temperature during heating operation, the operating frequency is uniformly stepped down to operate the compressor to lower the condensing temperature, and the operating frequency fluctuates significantly. The room temperature fluctuates greatly and the comfort is impaired, and the reliability of the compressor is impaired. The present invention has been made in view of such a situation, and an object of the present invention is to reduce the fluctuation of the operating frequency of the compressor and to reduce the room temperature fluctuation without impairing the comfort. It is to provide an air conditioner that does not impair the reliability of the air conditioner.

[0010]

The air conditioner of the present invention comprises:
A refrigeration cycle in which a compressor, a four-way valve, an indoor heat exchanger, an expansion mechanism and an outdoor heat exchanger are sequentially connected by a refrigerant pipe, and the operating frequency of the compressor is determined based on the condensation temperature of the refrigerant in the indoor heat exchanger. In the air conditioner having a control device for controlling, the control device is characterized by controlling the operating frequency of the compressor according to the temperature difference between the condensation temperature before a predetermined time and the current condensation temperature. , And the controller is
When the condensation temperature of the refrigerant in the indoor heat exchanger becomes equal to or higher than a preset temperature, the operation frequency of the compressor is controlled to be lowered according to the temperature difference between the condensation temperature before a predetermined time and the current condensation temperature. It is also characterized by a compressor,
A refrigeration cycle in which a four-way valve, an indoor heat exchanger, an expansion mechanism, and an outdoor heat exchanger are sequentially connected by a refrigerant pipe, and control that controls the operating frequency of the compressor based on the condensation temperature of the refrigerant in the indoor heat exchanger In the air conditioner equipped with the device, the control device controls the operating frequency of the compressor according to the temperature difference between the condensation temperature before the predetermined time and the current condensation temperature, and obtains the temperature difference between the condensation temperatures. Second time interval
The feature is that the first interval is set to be longer than each interval after the first time.

[0011]

In the air conditioner configured as described above, the operation of the compressor during the heating operation is such that the operation frequency at which the compressor is operated is set to a temperature that is a predetermined time before the condensation temperature of the refrigerant in the indoor heat exchanger. It is performed by controlling to decrease by a predetermined reduction amount for each temperature difference according to the difference, so that a temperature difference that changes according to the state in which the condensation temperature changes is obtained, and the temperature difference is used for each temperature difference in advance. The reduction range of the operating frequency defined in 1. is selected, and the reduction range of the operating frequency can be changed according to the change of the condensation temperature. Therefore, when the condensing temperature is set to a required value, the required condensing temperature can be smoothly set while the fluctuation of the operating frequency for operating the compressor is not increased. as a result,
There is little fluctuation in room temperature in the air-conditioned room, comfort is not impaired, and reliability of the compressor is not impaired.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 is a refrigeration cycle diagram, FIG. 2 is a diagram for explaining control, FIG. 2 (a) is a diagram for explaining the overall control, and FIG. 2 (b) is a difference in condensation temperature in the B region. 4 is a characteristic diagram of a first control example, and FIG. 4 is a characteristic diagram of a second control example.

In FIG. 1, reference numeral 1 denotes a refrigeration cycle of an air conditioner, which comprises a compressor 2 and a four-way valve 3 connected between a discharge port of the compressor 2 and an inflow port provided with an accumulator. Further, it has an outdoor heat exchanger 4 and an indoor heat exchanger 5 each having one end connected to the four-way valve 3, and an expansion valve 6 is provided between the other ends of the outdoor heat exchanger 4 and the indoor heat exchanger 5. Are connected.

Then, the four-way valve 3 is switched to change the flow direction of the refrigerant in the refrigeration cycle 1, thereby enabling the cooling operation and the heating operation, respectively. Further, a temperature sensor 7 is attached to the indoor heat exchanger 5, and the condensation temperature Tc of the refrigerant in the indoor exchanger 5 during the heating operation is set.
It is designed to detect ₀ .

On the other hand, 8 is a control device equipped with a microcomputer, which has a room temperature sensor for measuring the setting input of conditions associated with the air conditioning operation, the condensation temperature Tc ₀ from the temperature sensor 7, or the room temperature in the air-conditioned room. Each temperature data from 9 etc. is inputted. Further, in the control device 8, among the condensation temperature Tc ₀ of the refrigerant detected by the temperature sensor 7, the condensation temperature Tc ₀₁ one minute before and the condensation temperature Tc ₀₂ 30 seconds before are stored so that they can be extracted with a delay. Continues to be.

The start-up and stop of the refrigeration cycle 1 and control during each operation by the control device 8 are based on preset operating conditions, temperature data from the temperature sensors 7, 9, etc. This is performed while the flow of the refrigerant is interrupted or the flow rate of the refrigerant is controlled. Such control is performed by the control unit 10 of the indoor unit provided in the control device 8 to control the indoor heat exchanger 5 in the indoor unit 11 installed in the air-conditioned room, an indoor blower (not shown), and the like. This is executed by the control unit 12 of the unit controlling the outdoor heat exchanger 4 in the outdoor unit 13 installed outdoors, an outdoor blower (not shown), the compressor 2, and the like. In addition, the compressor 2 is provided with an inverter circuit 14,
The operation is performed at the operation frequency f ₀ set here.

Then, when the refrigeration cycle 1 performs the heating operation, the following control is performed. That is, in FIG. 2, in the area A during which the condensation temperature Tc ₀ of the refrigerant in the indoor heat exchanger 5 detected by the temperature sensor 7 rises to the first temperature T ₁ = 55 ° C. The control of the room temperature based on the measured temperature of the indoor unit is based on the room temperature control command from the control unit 10 of the indoor unit.
Then, the compressor 2 is operated at the operating frequency f ₀ set by the inverter circuit 14 to raise the room temperature.

In the region B where the condensing temperature Tc ₀ is 55 ° C. or higher, the condensing temperature Tc rises and the first temperature T ₁ = 55 ° C.
When or when it exceeds, the first stepping down of the operating frequency f ₀ is performed. This is performed by issuing a request command based on the condensing temperature Tc detected from the control unit 10 of the indoor unit to the control unit 12 of the outdoor unit, and the detected condensing temperature Tc ₀ is first stored in the control device 8. Based on the temperature difference ΔTc ₀₁ from the condensation temperature Tc ₀₁ one minute before, the operating frequency set in advance for the temperature difference ΔTc ₀ shown in FIG. The number of steps n that lowers f ₀ is selected.

The operating frequency f set for the temperature difference ΔTc ₀ stored in the controller 8 in advance is set.
The descent step number n of ₀ is the temperature difference ΔTc from the time before the predetermined time.
It is set so that the smaller ₀ is, the smaller it is, and the larger ₀ is, the larger it is.

Subsequently, the inverter circuit 14 steps down the operating frequency f ₀ by the frequency n × Δf ₀ corresponding to the selected step number n. The condensing temperature Tc ₀ is lowered by operating the compressor 2 with the lowered operating frequency f ₀ .

If the condensing temperature Tc ₀ is still 55 ° C. or higher and is in the region B after 30 seconds or more, the second step-down of the operating frequency f ₀ is performed. This is based on the temperature difference ΔTc ₀₂ between the detected condensing temperature Tc ₀ and the condensing temperature Tc ₀₂ 30 seconds before, which is stored in the control device 8. Δ
The step number n for lowering the operating frequency f ₀ with respect to Tc ₀ is selected, and the operating frequency f ₀ is stepped down by the frequency n × Δf ₀ corresponding to the selected step number n. The compressor 2 is operated by the lowered operating frequency f ₀ , and the condensing temperature Tc ₀ becomes low.

Thereafter, if the condensing temperature Tc ₀ is still 55 ° C. or higher and is in the region B even after a lapse of 30 seconds or more, the step-down of the operating frequency f ₀ of the third time, the fourth time, ... The number n of steps for lowering the operating frequency f ₀ is selected based on the temperature difference ΔTc ₀₂ from the condensing temperature Tc ₀₂ 30 seconds before, and is continuously performed.

Further, the condensing temperature Tc ₀ is the first temperature T ₁ =
In the C region while the second temperature T ₂ = 51 ° C. is decreased from 55 ° C., the operating frequency f ₀ of the compressor 2 is maintained at the operating frequency as it is, and this operating state is continued.

Further, the condensation temperature Tc ₀ is the second temperature T ₂
In the region A when the temperature becomes lower than = 51 ° C, the operating frequency ₀ of the compressor 2 is controlled again based on the temperature measured by the room temperature sensor 9 in the normal state so as to raise the room temperature.

Since the operating frequency f ₀ of the compressor 2 is controlled in this way, when the condensing temperature Tc ₀ is in the B region, it is said that one minute before the first stepping down of the operating frequency f _0. Since the temperature difference ΔTc ₀₁ from the condensation temperature Tc ₀₁ at a relatively long time interval is used,
When the temperature rise gradient is large, the temperature difference ΔTc ₀₁ takes a relatively large value, and the number n of steps of decreasing the operating frequency f ₀ with respect to the temperature difference ΔTc ₀₁ also becomes large, resulting in a rapid decrease in the condensation temperature Tc ₀ . realizable. Further, when the temperature rise gradient is small, the temperature difference ΔTc ₀₁ takes a small value, and the number n of steps of decreasing the operating frequency f ₀ with respect to this temperature difference ΔTc ₀₁ is also small, so that the condensing temperature T is gentle.
A reduction of c ₀ can be realized.

[0026] Further, the second time in the B area continues,
Alternatively, in performing the step-down of the operating frequency f ₀ after the third time, the temperature difference Δ with the condensing temperature Tc ₀₁ at a time interval of 30 seconds before, which is shorter than the first time, is set.
Since Tc ₀₁ is used, the number n of steps of lowering the operating frequency f ₀ with respect to the temperature difference ΔTc ₀₁ is also small, the operating frequency f ₀ is less likely to drop, and a gradual lowering of the condensation temperature Tc ₀ can be realized. In the first time, the condensation temperature Tc ₀ is rapidly increased.
Even if the temperature is decreased, the second and subsequent gradual decrease of the condensation temperature Tc ₀ is executed after the early time interval, and the condensation temperature Tc ₀ is stabilized without being greatly changed. Then, the compressor 2 can continue to operate at a stable and stable operating frequency f ₀ .

Therefore, the fluctuation of the operating frequency f ₀ is gradual, the air conditioning capacity is not deteriorated, and the condensation temperature Tc ₀ is also gradually changed. Therefore, the temperature sensor 7
Even if there is a response delay in the temperature detection at, the operation will be performed at an operating frequency f ₀ that does not deviate significantly from the required value, the room temperature fluctuation in the air-conditioned room will be small, and comfort will not be impaired. Good air conditioning can be achieved.

Further, since the compressor 2 is operated at the operating frequency f ₀ which does not cause large fluctuations, liquid backing and overheating are not repeated. Then, the compressor 2 can maintain a predetermined performance for a long period of time and becomes highly reliable.

Next, a first control example in this embodiment will be described with reference to the characteristic diagram of FIG. In FIG. 3, the vertical axis indicates the condensation temperature Tc.
The condensing temperature Tc ₁ and the operating frequency f ₁ in the first control example are shown by taking ₀ and the operating frequency f ₀ and taking the elapsed time t on the horizontal axis.

When the heating operation of the air conditioner is started and the condensing temperature Tc _{1 of the} refrigerant rises as the operating frequency f ₁ rises, reaching the first temperature T ₁ = 55 ° C. and entering the region B, the control is performed. The control of the operating frequency f ₁ in the device 8 is started. First, as the first time, the temperature difference ΔTc ₁₁ = 3 degrees between the condensing temperature Tc ₁ reaching 55 ° C. and the condensing temperature Tc ₁₁ = 52 ° C. one minute ago is calculated. Based on the calculation result, the number of steps n for decreasing the operating frequency f ₀ set in the temperature difference ΔTc ₀ shown in FIG.
From among the above, the number of steps n = 1 for decreasing the operating frequency f ₀ corresponding to the temperature difference ΔTc ₁₁ = 3 degrees is selected.

Next, the operation frequency f ₁ is stepped down by the selected step number n = 1, and the step number n
Inverter circuit 1 at frequency 1 × Δf ₀ corresponding to = 1
The operating frequency f ₁ is decreased by 4 and the compressor 2 is operated by the decreased operating frequency f ₁ so that the condensing temperature Tc ₁ gradually decreases.

When 30 seconds have passed, the condensation temperature Tc
_{Since 1} is in the C range, the operating frequency f of the compressor 2
₁ is the frequency 1 × Δf ₀ corresponding to the step number n = 1
It is maintained as it was lowered and continues. Then, the condensing temperature Tc ₁ is stable and the operating frequency f ₁ is also stable.

As described above, in the present control example, the operating frequency f ₁ is stable without being greatly changed, so that the room temperature fluctuation in the air-conditioned room is small, the comfort is not impaired, and the air conditioning is good. In addition, the compressor 2 is also highly reliable because liquid backing and overheating are not repeated.

Next, a second control example in this embodiment will be described with reference to the characteristic diagram of FIG. In FIG. 4, the vertical axis indicates the condensation temperature Tc.
The condensing temperature Tc ₂ and the operating frequency f ₂ in the second control example are shown by taking ₀ and the operating frequency f ₀ and taking the elapsed time t on the horizontal axis.

When the heating operation of the air conditioner is started and the operating temperature f ₂ rises, the condensing temperature Tc _{2 of the} refrigerant rises, reaches the first temperature T ₁ = 55 ° C., and enters the region B. The control of the operating frequency f ₂ in the device 8 is started. First, as the first time, the temperature difference ΔTc ₂₁ = 8 degrees between the condensing temperature Tc ₂ that reached 55 ° C. and the condensing temperature Tc ₂₁ = 47 ° C. one minute ago is calculated. Based on the calculation result, the number of steps n for decreasing the operating frequency f ₀ set in the temperature difference ΔTc ₀ shown in FIG.
From among these, the number of steps n = 3 for decreasing the operating frequency f ₀ corresponding to the temperature difference ΔTc ₂₁ = 8 degrees is selected.

Next, the operation frequency f ₂ is stepped down by the selected step number n = 3, and the step number n
Inverter circuit 1 at frequency 3 × Δf ₀ corresponding to = 3
The operating frequency f ₂ is decreased by 4 and the compressor 2 is operated by the decreased operating frequency f ₂ so that the condensing temperature Tc ₂ rises slowly.

Next, when 30 seconds have passed, the condensing temperature Tc ₂ is still in the range B, so the second time is 57.
Condensation temperature Tc ₂ reached ℃ and condensation temperature Tc 30 seconds before
A temperature difference ΔTc ₂₂ = 2 degrees from ₂₂ = 55 ° C. is calculated. Based on the calculation result, the operating frequency f ₀ corresponding to the temperature difference ΔTc ₂₂ = 2 degrees is selected from the number n of steps of decreasing the operating frequency f ₀ set to the temperature difference ΔTc ₀ stored in the control device 8. The number of descent steps n = 1 is selected.

Next, the operation frequency f ₂ is stepped down by the selected step number n = 1, and the step number n
Inverter circuit 1 at frequency 1 × Δf ₀ corresponding to = 1
The operating frequency f ₂ is decreased by 4 and the compressor 2 is operated by the decreased operating frequency f ₂ , whereby the condensing temperature Tc ₂ is gradually lowered.

Since the condensing temperature Tc ₂ is in the C range after 30 seconds have passed, the operating frequency f ₂ of the compressor ₂ is the frequency 1 corresponding to the step number n = 1.
The state where it has been lowered by × Δf ₀ is maintained and continued. Then, the condensing temperature Tc ₁ becomes stable, and the operating frequency f ₂
Will also be stable.

As described above, in this control example as well, as in the first control example, the operating frequency f ₂ is stable without being greatly changed, so that the room temperature change in the air-conditioned room is small, the comfort is not impaired, and air conditioning is performed. It will be good. Also compressor 2
Also, liquid backing and overheating are not repeated, resulting in high reliability.

It should be noted that the present invention is not limited to the above-described embodiments, but can be implemented with various modifications without departing from the scope of the invention.

[0042]

As is apparent from the above description, according to the present invention, when the compressor is operated during the heating operation, the operating frequency for operating the compressor is set to be a predetermined time before the condensation temperature of the refrigerant in the indoor heat exchanger. The temperature difference in the air-conditioning room reduces the room temperature fluctuations in the air-conditioning room, and the comfort is maintained. An effect such as reliability is not impaired.

[Brief description of drawings]

FIG. 1 is a refrigeration cycle diagram showing an embodiment of the present invention.

FIG. 2 is a diagram for explaining the control of one embodiment of the present invention, and FIG. 2 (a) is a diagram for explaining the overall control.
(B) is a diagram showing a step-down of the operating frequency with respect to the difference in condensation temperature in the B region.

FIG. 3 is a characteristic diagram of a first control example in the control according to the embodiment of the present invention.

FIG. 4 is a characteristic diagram of a second control example in the control according to the embodiment of the present invention.

FIG. 5 is a diagram for explaining conventional control.

FIG. 6 is a characteristic diagram in conventional control.

[Explanation of symbols]

1 ... refrigeration cycle 2 ... compressor 5 ... indoor heat exchanger Tc ₀ ... condensing temperature Tc ₀₁ ... 1 min prior to the condensation temperature Tc ₀₂ ... 30 seconds before the condensation temperature f ₀ ... operating frequency n ... number of steps

Claims (3)

[Claims] 1. A refrigeration cycle in which a compressor, a four-way valve, an indoor heat exchanger, an expansion mechanism, and an outdoor heat exchanger are sequentially connected by a refrigerant pipe, and based on a condensation temperature of the refrigerant in the indoor heat exchanger. In an air conditioner provided with a controller for controlling the operating frequency of the compressor, the controller controls the operating frequency of the compressor according to the temperature difference between the condensation temperature before a predetermined time and the current condensation temperature. An air conditioner characterized by. 2. When the condensation temperature of the refrigerant in the indoor heat exchanger is equal to or higher than a preset temperature, the control device compresses the refrigerant in accordance with a temperature difference between the condensation temperature before a predetermined time and the current condensation temperature. The air conditioner according to claim 1, wherein the air conditioner is controlled so as to lower the operating frequency of the machine. 3. A refrigeration cycle in which a compressor, a four-way valve, an indoor heat exchanger, an expansion mechanism and an outdoor heat exchanger are sequentially connected by a refrigerant pipe, and based on the condensation temperature of the refrigerant in the indoor heat exchanger. In an air conditioner provided with a control device for controlling the operating frequency of the compressor, the control device controls the operating frequency of the compressor according to the temperature difference between the condensation temperature before a predetermined time and the current condensation temperature. The air conditioner is characterized in that the time interval for obtaining the temperature difference of the condensation temperature is set longer in the first interval than in the second and subsequent intervals.