JPH11101513A - Air conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air conditioner enabling adequate control of operating frequency of a compressor according to a load applied on the compressor avoiding an abnormal stop of the compressor. SOLUTION: A compressor is controlled through an inverter variably with compressing capacity. Arranging an outdoor heat exchanger sensor to an outdoor heat exchanger, condensing temperature DC in cooling run is detected. When the condensing temperature DC is rising, the minimum operating frequency of the compressor is set to F0 if the condensing temperature DC is temperature rising side reference temperature DCTR1 or lower and if the condensing temperature DC exceeds the temperature rising side reference temperature DCTR1, the minimum operating frequency is set to FTR that is higher than F0. When the condensing temperature DC is falling, the minimum operating frequency is set to FTR that is higher than F0 if the condensing temperature DC is higher than temperature falling side reference temperature DCTR4 and if the condensing temperature DC is the temperature falling side reference temperature DCTR4 or below, the minimum operating frequency is set to F0.

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 whose compression capacity is variably controlled.

[0002]

2. Description of the Related Art Conventionally, an air conditioner having an inverter and variably controlling an operation frequency of a compressor according to a user's remote control operation or the like has been used. In such an air conditioner, the operation of the compressor is plotted on a graph as shown in FIG. 6 in which the condensing pressure and the operation frequency are two axes in relation to the operating frequency of the compressor and the torque of the compressor drive motor. A possible area is formed. The dashed line in the figure indicates this operable area.

Here, under operating conditions of high condensing pressure, for example, during a cooling operation when the outdoor temperature is high, the operating frequency of the compressor is changed to f1 'shown in FIG. Is changed to f2 '. When the operating frequency is f1, the condensing pressure is high, and the operating point of the refrigerant circuit at that time is located at A1 '. However, the operation frequency of the compressor is quickly changed to f1 ′ by control of a microcomputer or the like via the inverter.
From f1 'to p2', while the condensing pressure changes from p1 'to p2' with a delay in the change of the operating frequency, as shown by the broken line in FIG. Therefore, the operating point of the refrigerant circuit is A
Before reaching 2 ′, when the operating frequency becomes Fstop, the operating point exceeds the operable area indicated by the dashed line. If the operation is continued beyond the operable area, an excessive load is applied to the compressor, so that the compressor may not be able to operate, resulting in an abnormal stop. Therefore, in the conventional air conditioner, the outdoor temperature is detected by an outdoor temperature sensor provided in the outdoor unit, and the operating frequency of the compressor is controlled based on the outdoor temperature.

FIG. 5 is a flowchart showing control of the compressor in the conventional air conditioner performed based on the outdoor temperature. First, in step S11, the outdoor temperature DOA is measured by the outdoor temperature sensor. Next, in step S12, the measured outdoor temperature DOA and
A comparison is made with a predetermined reference temperature DOAMN. When the outdoor temperature DOA is higher than the reference temperature DOAMN, the process proceeds to step S13, and the lower limit operation frequency is set to the above-mentioned Fst.
If the outdoor temperature DOA is equal to or lower than the reference temperature DOAMN, the process proceeds from step S12 to step S14, and the lower limit operation frequency is set to F0 (see FIG. 6). Set. By limiting the lowering of the operating frequency of the compressor by the lower limit operating frequency, the operating point of the refrigerant circuit is prevented from deviating from the operable area of the compressor, and the reduction of the condensing pressure is reduced by the compressor. Even if it occurs after the operation frequency, the compressor is not stopped abnormally.

[0005]

The above-mentioned condensing pressure is certainly influenced greatly by the outdoor temperature. Therefore, as in the above-described conventional air conditioner, by controlling the operating frequency by indirectly considering the outdoor temperature as the load on the compressor,
Abnormal stop of the compressor can be avoided by simple control. However, the condensing pressure fluctuates depending not only on the outdoor temperature but also on the indoor temperature, a set temperature by a remote controller or the like, a set air volume, and the like. Therefore, for example, when the indoor temperature set by the user is relatively high, the load on the compressor may not be very heavy even if the outdoor temperature is high. Therefore, in such a case, even if the outdoor temperature DOA
Is higher than the reference temperature DOAMN, the operating frequency of the compressor can be made lower than the lower limit operating frequency F1 without causing an abnormal stop.

However, in the above-mentioned conventional air conditioner, the lower limit operating frequency of the compressor is determined based on the outdoor temperature. Sometimes operated the compressor at a high operating frequency. By operating the compressor at an unnecessarily high operating frequency, the supply of the air conditioning capacity to the indoor unit becomes excessive, and the start / stop of the compressor is repeated, whereby the vertical movement of the room temperature becomes severe. There is a problem that air conditioning comfort is impaired. In addition, there is also a problem that power is wasted due to excessive supply of the air-conditioning capacity to the indoor units as described above, and this is a factor that increases running costs. Further, since the compressor is operated at an operation frequency higher than necessary, there is a problem that the operation noise is increased and air conditioning comfort is impaired.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional drawbacks, and an object of the present invention is to reliably avoid abnormal stoppage of a compressor and to operate the compressor at an operating frequency corresponding to the load of the compressor. An object of the present invention is to provide an air conditioner capable of performing appropriate control of the air conditioner.

[0008]

Accordingly, an air conditioner according to a first aspect of the present invention includes a compressor 1 controlled to have a variable compression capacity, a predetermined lower limit operation frequency, and the lower limit operation frequency. In the air conditioner which limits the decrease in the operating frequency of the condensing temperature detector 13
And the lower limit operation frequency is determined by the condensation temperature detector 1
It is characterized in that it is set based on the condensation temperature detected in 3.

In the air conditioner of the first aspect, the lower limit operation frequency is set based on the condensation temperature. Since there is a direct correlation between the condensing temperature and the load of the compressor 1, the air conditioner operates according to the load of the compressor 1 while reliably avoiding abnormal stop of the compressor 1 in the air conditioner. Appropriate control of the frequency can be performed.

[0010] The air conditioner according to claim 2 is characterized in that the lower limit operation frequency is set higher as the condensing temperature is higher.

In the air conditioner of the second aspect, when the load is light, the lower limit operation frequency is set low,
It is possible to avoid operating the compressor at an operation frequency higher than necessary while reliably avoiding abnormal stop of the compressor 1.

In the air conditioner according to a third aspect of the present invention, the lower limit operating frequency is set to a predetermined first reference frequency F0 when the condensing temperature is equal to or lower than a predetermined reference temperature, while the condensing temperature is lower than the reference temperature. Is higher than the first reference frequency F0, the second reference frequency FTR is set higher than the first reference frequency F0.

In the air conditioner of the third aspect, the compressor 1
Can be simplified by using two reference frequencies, and the implementation can be facilitated.

The air conditioner according to a fourth aspect is characterized in that the reference temperature is set to be higher when the condensing temperature rises than when it falls.

According to the air conditioner of the fourth aspect, hunting can be prevented and air conditioning comfort can be further improved.

[0016]

Next, specific embodiments of the air conditioner of the present invention will be described in detail with reference to the drawings.

FIG. 4 is a diagram showing a refrigerant circuit of the air conditioner. As shown in the figure, in this air conditioner, a discharge pipe 1a and a suction pipe 1b of a compressor 1 are connected to a four-way switching valve 10, and the four-way switching valve 10 has an outdoor heat exchanger 2, a capillary The tube 3 and the indoor heat exchanger 4 are sequentially
They are annularly connected by a gas pipe 19a, a first liquid pipe 19b, a second liquid pipe 19c, and a second gas pipe 19d. Then, a part of the second liquid pipe 19c becomes the liquid pipe 17 of the communication pipe,
In addition, a part of the second gas pipe 19d is connected to the gas pipe 16 of the connecting pipe.
It has become. The compressor 1 is variably controlled in compression capacity by a control unit 12 via an inverter 11. The control unit 12 is configured using a microcomputer or the like. Further, the outdoor heat exchanger 2 is provided with an outdoor heat exchange thermistor 13. The outdoor heat exchange thermistor 13 functions as a condensation temperature detector during the cooling operation, and the detected condensation temperature is input to the control unit 12.

The air conditioner can perform a cooling operation or a heating operation based on a command from a remote controller or the like. When performing the cooling operation, the four-way switching valve 10 is switched in the solid line direction shown in the figure, and the refrigerant is discharged from the compressor 1 in order from the outdoor heat exchanger 2, the capillary tube 3 (or the electric valve), the indoor heat exchanger. 4 to allow the outdoor heat exchanger 2 to function as a condenser and the indoor unit 4 to function as an evaporator.
Then, the amount of heat absorbed in the room is released to the outside of the room via the refrigerant, thereby lowering the temperature in the room and performing cooling. on the other hand,
When performing the heating operation, the four-way switching valve 10 is switched in the direction of the broken line shown in the figure to circulate the refrigerant in a direction opposite to that in the cooling operation, and the outdoor heat exchanger 2 functions as an evaporator. The indoor heat exchanger 4 functions as a condenser, and the amount of heat absorbed by the outdoor heat exchanger 2 is released into the room via the refrigerant, thereby increasing the temperature of the room and performing heating.

In the above-described air conditioner, the air conditioning capacity can be appropriately exhibited according to the user's remote control setting and the like.
The compressor 1 is controlled to have a variable compression capacity. This control is performed by the control unit 12 changing the operating frequency of the compressor 1 via the inverter 11. However, also in the above air conditioner, similarly to the conventional air conditioner, a graph in which the condensing pressure and the operating frequency are two axes in relation to the operating frequency of the compressor 1 and the torque of the motor driving the compressor 1. Beyond the operable area formed above, the compressor 1
Can not drive. If such an operation is continued, an excessive load is applied to the compressor 1, and the compressor 1 may not be able to operate, resulting in an abnormal stop. Such a situation can occur under an overload condition in which the compressor 1 is driven at a low operation frequency to perform a cooling operation when the outdoor temperature is high. Therefore, in the air conditioner, the outdoor unit is provided with the outdoor heat exchange thermistor 13, and the cooling temperature detected by the outdoor heat exchange thermistor 13 during the cooling operation is used to limit the decrease in the operating frequency of the compressor 1. Next, this will be described.

FIG. 2 is a flowchart showing the control performed by the control unit 12 to limit the decrease in the operating frequency of the compressor 1. When performing this control, first, in step S1 of the flowchart of FIG. 7, the condensing temperature DC is measured by the indoor heat exchange thermistor 13. Then, in step S2, the measured condensation temperature DC is compared with predetermined reference temperatures DCTR1 and DCTR4. At this time, if the condensing temperature DC is increasing, the condensing temperature DC is compared with the heating-side reference temperature DCTR1, and if the condensing temperature DC is decreasing, the condensing temperature is set as a temperature lower than the heating-side reference temperature DCTR1. Is compared with the reduced temperature-side reference temperature DCTR4. Then, the condensing temperature DC becomes equal to each reference temperature DCTR1, DTR
If it is higher than CTR4, the process proceeds to step S3, where the lower limit operating frequency of the compressor 1 is set to the second reference frequency higher than the first reference frequency F0 (see FIG. 3) which is the lowest frequency of the operable area. It is set as FTR (see the figure). On the other hand, when the condensation temperature DC is equal to the respective reference temperatures DCTR1, DCTR
If it is equal to or lower than TR4, the process proceeds to step S4, and the lower limit operation frequency of the compressor 1 is set to the first reference frequency F0. That is, as shown in FIG. 1, considering that the condensation temperature DC once exceeds the reference temperature DCTR1 from a point lower than the reference temperature DCTR1 and falls again below the reference temperature DCTR4, until the condensation temperature DC exceeds the heating-side reference temperature DCTR1. The lower limit operation frequency is set to F0, and the lower limit operation frequency is set to FTR if the condensing temperature DC exceeds the heating-side reference temperature DCTR1. If the condensing temperature DC falls below the cooling-side reference frequency DCTR4, the lower limit operation frequency is returned to F0.

FIG. 3 is a diagram showing the lower operating frequency side of the operable area formed on a graph having the condensing pressure and the operating frequency of the compressor 1 as two axes. Here, it is considered that the operating frequency of the compressor 1 is reduced from f1 to f2 in FIG. First, when the operating frequency is f1, the operating point of the refrigerant circuit is at A1 and the condensing pressure is high. At this time, the condensation temperature DC having a direct correlation with the condensation pressure is higher than any of DCTR1 and DCTR4. Therefore, regardless of whether the condensing temperature DC is increasing or decreasing, the lower limit operation frequency is set to the second reference frequency FTR. Since the decrease in the condensing pressure is delayed from the decrease in the operating frequency of the compressor 1, the decrease in the operating frequency of the compressor 1 is limited by the second reference frequency FTR. Become. However, since the operating frequency of the compressor 1 has decreased from f1 to FTR, the condensing pressure generally decreases gradually thereafter. Also, the condensing pressure decreases when the indoor set temperature is raised by a user's remote control operation or the like. When the condensing pressure decreases for these reasons, the condensing pressure and the condensing temperature D
Since there is a direct correlation with C, the condensation temperature DC
Will also decrease. When the condensing temperature DC becomes lower than the cooling-side reference temperature DCTR4 in this way, the lower limit operating frequency is set to the first reference frequency F0, so that the operating frequency of the compressor 1 can be reduced to f2. . The operating point of the refrigerant circuit reached in this way is indicated by A2 in FIG.

On the other hand, even when the operating frequency of the compressor 1 is similarly decreased from f1 to f2, the condensing pressure is sufficiently low and the condensing temperature DC is not changed to any reference temperature DCTR.
1. In the case where the frequency is lower than DCTR4, the lower limit operation frequency is set to the first reference frequency F0. Therefore, the operating frequency of the compressor 1 can be reduced from f1 to f2 as it is. In FIG. 3, this is shown as a change from the operating point B1 to B2.

In the above air conditioner, the lower limit operation frequency is set based on the condensation temperature DC. Since there is a direct correlation between the condensing pressure and the condensing temperature DC, by performing control based on the condensing temperature DC, it is possible to perform control for directly grasping the load on the compressor 1. In a conventional air conditioner, since the load of the compressor 1 is indirectly grasped based on the outdoor temperature, the compressor may be operated at an operation frequency higher than necessary. However, in the above, since the load on the compressor 1 is directly grasped and the control based on the load is performed, an abnormal stop occurs in the compressor 1 as in the change from the operating point A3 to A2 in FIG. When there is no risk of light load, the operating frequency of the compressor 1 can be reliably reduced. Therefore, it is possible to prevent the compressor 1 from operating at an operation frequency higher than necessary while avoiding abnormal stop of the compressor 1. Therefore, it is possible to avoid a situation where the start and stop of the compressor 1 are repeated due to an excessive supply of the air conditioning capacity to the indoor units, and suppress a vertical movement of the room temperature caused by the start and stop of the compressor 1 to improve air conditioning comfort. be able to. In addition, by suppressing excessive supply of the air conditioning capacity to the indoor units, power consumption can be reduced and running costs can be reduced. Further, when the load on the compressor 1 is light, the lower limit operation frequency is surely lowered, so that the operation sound can be suppressed and the air conditioning comfort can be further improved. In addition, the lowering-side reference temperature DCTR4 to be compared when the condensing temperature DC is decreasing is set lower than the rising-side reference temperature DCTR1 to be compared when the condensing temperature DC is increasing. Therefore, it is possible to avoid a hunting phenomenon that occurs when the setting change of the lower limit operation frequency is repeated, thereby further improving the air-conditioning comfort. The control using the two lower limit operation frequencies F0 and FTR enables simple control.

Although the specific embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and can be implemented with various modifications within the scope of the present invention. Although the control of the compressor 1 during the cooling operation has been described above, the present invention can also be applied during the heating operation.
In this case, the indoor heat exchanger 4 may be provided with an indoor heat exchange thermistor, and the temperature may be compared with a predetermined reference temperature using the condensing temperature detected by the indoor heat exchange thermistor. In the above description, an example in which the lower limit operation frequency is divided into two stages of F0 and FTR has been described.
, The lower limit operating frequency is increased over three or more stages, and it is possible to set the finer lower limit operating frequency for the load.

[0025]

According to the first aspect of the present invention, the lower limit operation frequency of the compressor is set based on the condensation temperature at which there is a direct correlation between the condensation temperature and the load on the compressor. . Therefore, it is possible to appropriately control the operating frequency of the compressor in accordance with the load on the compressor while reliably preventing abnormal stop of the compressor.

In the air conditioner of the second aspect, when the load is light, the lower limit operation frequency is set low,
It is possible to avoid operating the compressor at an unnecessarily high operating frequency while reliably avoiding abnormal stop of the compressor.

Further, in the air conditioner according to the third aspect, the control of the compressor can be simplified by using two reference frequencies, so that the operation can be easily performed.

According to the air conditioner of the fourth aspect, hunting can be prevented and air conditioning comfort can be further improved.

[Brief description of the drawings]

FIG. 1 is a graph for explaining setting of a lower limit operation frequency of a compressor performed in an air conditioner of the present invention.

FIG. 2 is a flowchart for explaining setting of the lower limit operation frequency.

FIG. 3 is a diagram illustrating operation control of a compressor performed using the lower limit operation frequency.

FIG. 4 is a refrigerant circuit diagram of the air conditioner.

FIG. 5 is a flowchart for explaining setting of a lower limit operation frequency of a compressor performed in a conventional air conditioner.

FIG. 6 is a diagram illustrating operation control of a compressor performed in a conventional air conditioner.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Compressor 13 Outdoor heat exchange thermistor DC Condensation temperature F0 1st reference frequency (lower limit operation frequency) FTR 2nd reference frequency (lower limit operation frequency)

Claims (4)

[Claims] A compressor (1) controlled to have a variable compression capacity.
A condensing temperature detector (13) is provided in an air conditioner provided with a predetermined lower limit operating frequency and restricting a decrease in the operating frequency of the compressor (1) by the lower limit operating frequency. The lower limit operation frequency is the condensing temperature (DC) detected by the condensing temperature detector (13).
An air conditioner characterized in that the air conditioner is set based on the condition. 2. The air conditioner according to claim 1, wherein the lower limit operation frequency is set higher as the condensing temperature (DC) is higher. 3. The lower limit operating frequency is a predetermined first reference frequency (F0) when the condensing temperature (DC) is equal to or lower than a predetermined reference temperature, while the condensing temperature (DC) is lower than the reference temperature. Is higher than the first reference frequency (F
The air conditioner according to claim 2, wherein the second reference frequency (FTR) is higher than 0). 4. The air conditioner according to claim 3, wherein the reference temperature is set to be higher when the condensation temperature rises than when the condensation temperature falls.