JP6851842B2 - Air conditioner - Google Patents

Description

The present invention relates to an air conditioner that secures a high and low differential pressure of a compressor.

Conventionally, in an air conditioner, it is difficult to secure the difference between high and low pressure of the compressor in the cooling operation at low outside temperature because the discharge pressure of the compressor does not rise, and the refrigerating machine oil in the refrigeration cycle is returned to the compressor. There is a possibility that the compressor will fail due to poor lubrication. Therefore, when it is judged that the high / low pressure difference is not sufficient, the protection control for forcibly increasing the operating capacity to secure the high / low pressure difference is installed. However, when this protection control is activated, the required cooling capacity becomes unrealizable.

In the air conditioner disclosed in Japanese Patent Application Laid-Open No. 2002-39598 (Patent Document 1), the excess liquid refrigerant is stored in the air side heat exchanger or the fan of the air side heat exchanger during the low outside temperature cooling operation. By lowering the number of revolutions, the heat exchange capacity of the heat source side heat exchanger is lowered, and by raising the discharge pressure of the compressor, high and low differential pressures are secured.

JP-A-2002-39598

However, when the high and low differential pressures are secured by increasing the discharge pressure of the compressor, if the high pressure rises too much and the compressor bursts, a serious accident may occur.

Therefore, an object of the present invention is to provide an air conditioner capable of safely ensuring a high-low pressure difference of a compressor at a low outside air temperature.

In order to solve the above problems, the air conditioner according to one embodiment of the present invention includes a compressor that compresses the refrigerant, a heat source side heat exchanger that condenses the refrigerant discharged from the compressor, and the heat source side heat. When a low outside temperature is detected by a decompression device that decompresses the refrigerant condensed by the exchanger, a utilization side heat exchanger that evaporates the refrigerant from the decompression device, and an outside air temperature sensor , the decompression device decompresses the refrigerant. A control device for reducing the pressure on the suction side of the compressor is provided , and the control device sets a value of overheating of the refrigerant on the suction side of the compressor when a low outside temperature is detected by the outside air temperature sensor. The pressure is reduced by the depressurizing device, the pressure on the suction side of the compressor is reduced, and the control device determines the degree of overheating based on the degree of decrease in the outside air temperature detected by the outside air temperature sensor. When the set value is raised and the temperature drops by a predetermined temperature or more from the outside air temperature previously detected by the outside air temperature sensor, the control device raises the set value of the degree of superheat by a predetermined temperature and the previously detected value by the outside air temperature sensor. when increased from ambient temperature above a predetermined temperature, Ru by a predetermined temperature drop the superheat setting.

According to this description, it is possible to provide an air conditioner capable of safely ensuring the difference between high and low pressure of the compressor at low outside air temperature.

The refrigerating cycle system diagram of the air conditioner which concerns on 1st Embodiment of this invention is shown. A flowchart of low outside air temperature processing at low outside air temperature in an air conditioner is shown. The refrigerating cycle system diagram of the air conditioner which concerns on 2nd Embodiment of this invention is shown. The refrigerating cycle system diagram of the air conditioner which concerns on 3rd Embodiment of this invention is shown.

The air conditioner 11 according to the first embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a refrigeration cycle system diagram of the air conditioner 11 showing the first embodiment of the present invention.

The air conditioner 11 includes a compressor 1, a heat source side heat exchanger 2, a decompression device 3, a user side heat exchanger 4, a blower 5, an outside air temperature sensor 9A, a temperature sensor 9B, a pressure sensor 9C, and a control device 10. .. The compressor 1, the heat source side heat exchanger 2, the decompression device 3, and the user side heat exchanger 4 are connected by a refrigerant pipe 14 to form a refrigeration cycle.

The compressor 1, for example, a screw compressor, sucks and compresses the refrigerant. The heat source side heat exchanger 2 condenses and liquefies the gas refrigerant discharged from the compressor 1. The blower 5 adjusts the condensing capacity of the heat source side heat exchanger 2 by blowing air by rotation. The decompression device 3 is, for example, an expansion valve, and decompresses and cools the refrigerant liquefied by the heat source side heat exchanger 2. The user-side heat exchanger 4 exchanges heat with the refrigerant to cool the cold water circulated and supplied from the indoor unit or the like. The outside air temperature sensor 9A detects the outside air temperature. The temperature sensor 9B detects the temperature of the refrigerant sucked in the compressor 1. The pressure sensor 9C detects the pressure of the refrigerant sucked in the compressor 1. The control device 10 controls the compressor 1, the decompression device 3, the blower 5, and the like based on the operating state of the air conditioner 11.

Next, the basic operation of the air conditioner 11 forming the refrigeration cycle will be described.

The refrigerant sucked into the compressor 1 is compressed, and the compressed gas refrigerant is condensed by heat exchange with the atmosphere blown by the blower 5 at the heat source side heat exchanger 2. The condensed liquid refrigerant is decompressed and cooled by the decompression device 3. The decompressed refrigerant is heat-exchanged with water in the user-side heat exchanger 4 and evaporated. The evaporated refrigerant is returned to the compressor 1.

Next, the pressure lowering process at low outside air temperature executed by the control device 10 of the air conditioner 11 of the present embodiment will be described with reference to FIG.

FIG. 2 shows a flowchart of low outside air temperature processing at low outside air temperature in the air conditioner 11 of the present embodiment. The control program related to the flowchart shown in FIG. 2 is implemented in the control device 10. The control program is performed at all times or at predetermined time intervals while the air conditioner 11 is operating.

The control device 10 determines whether or not the outside air temperature is a low outside air temperature based on the temperature detected by the outside air temperature sensor 9A (S1). The control device 10 determines, for example, whether or not the outside air temperature is −10 ° C. or lower. When the outside air temperature is −10 ° C. or lower (S1: YES), the control device 10 determines whether or not the temperature has dropped by X ° C. (for example, 1 ° C.) or more from the outside air temperature detected in step S1 (S2). When the outside air temperature is not −10 ° C. or lower (S1: NO), the control device 10 performs normal operation (S11) and makes a determination in step S1.

When the temperature is lower than the outside air temperature detected in step S1 by X ° C. (for example, 1 ° C.) or more (S2: YES), the control device 10 is on the suction side of the compressor 1 based on the pressure detected by the pressure sensor 9C. It is determined whether or not the pressure of is equal to or higher than a predetermined lower limit pressure value (S3). When the pressure on the suction side of the compressor 1 is equal to or higher than the predetermined lower limit value (S3: YES), the control device 10 determines whether or not the degree of superheat on the suction side of the compressor 1 is smaller than the predetermined upper limit value. (S4). The control device 10 calculates the saturated gas temperature from the detected value of the pressure sensor 9C, and calculates the degree of superheat on the suction side of the compressor 1 from the difference from the detected value of the temperature sensor 9B.

When the calculated superheat degree on the suction side of the compressor 1 is smaller than a predetermined upper limit value (S4: YES), the control device 10 raises the set value of the superheat degree on the suction side of the compressor 1 by Y ° C. (S5). .. By increasing the set value of the degree of superheat on the suction side of the compressor 1 by Y ° C., the opening degree of the decompression device 3 is narrowed, the circulation amount of the refrigerant is reduced, and the pressure on the suction side of the compressor 1 is reduced. Then, the control device 10 continues the operation for a certain period of time in a state where the set value of the superheat degree on the suction side of the compressor 1 is increased (S6). The Y ° C. can be appropriately set according to the model and the like.

On the other hand, when the pressure on the suction side of the compressor 1 is smaller than the predetermined lower limit value (S3: NO), or when the degree of superheat on the suction side of the compressor 1 is equal to or higher than the predetermined upper limit value (S4: NO). The control device 10 forcibly increases the operating capacity and executes protection control for ensuring a high / low pressure difference (S7).

Further, when the control device 10 is not lowered by X ° C. (for example, 1 ° C.) or more from the outside air temperature previously detected by the outside air temperature sensor 9A (S2: NO), the control device 10 is Z ° C. (for example, 1) from the previously detected outside air temperature. It is determined whether or not the temperature has risen by more than (° C.) (S8). It should be noted that X ° C. and Z ° C. may be the same temperature or may be different, and can be appropriately set according to the model and the like.

When the temperature has not risen by Z ° C. (for example, 1 ° C.) or more from the previously detected outside air temperature (S8: NO), the control device 10 continues the current operating state for a certain period of time (S6). When the temperature rises by Z ° C. (for example, 1 ° C.) or more from the previously detected outside air temperature (S8: YES), the control device 10 lowers the set value of the degree of superheat on the suction side of the compressor 1 by Y ° C. (S9). ). By lowering the set value of the degree of superheat on the suction side of the compressor 1 by Y ° C., the circulation amount of the refrigerant is increased by the decompression device 3, and the pressure on the suction side of the compressor 1 is increased.

The control device 10 determines whether or not the outside air temperature is no longer a low outside air temperature based on the temperature detected by the outside air temperature sensor 9A (S10). For example, it is determined whether or not the outside air temperature is higher than −10 ° C. When the outside air temperature is −10 ° C. or lower (S10: NO), the control device 10 continues the current operating state for a certain period of time (S6). When the outside air temperature is higher than −10 ° C. (S10: YES), the control device 10 performs normal operation (S11) and makes a determination in step S1.

As described above, in the air conditioner 11 according to the present embodiment, when the control device 10 detects a low outside temperature, the control device 10 raises the set value of the degree of superheat of the refrigerant on the suction side of the compressor 1 and uses the depressurizing device 3. The refrigerant is depressurized to reduce the pressure on the suction side of the compressor 1. As a result, the difference between high and low pressure of the compressor 1 can be safely secured at low outside air temperature. Further, since the high / low pressure difference of the compressor 1 is secured only by the control by the control device 10, it is not necessary to change the refrigeration cycle or add parts, and the high / low pressure difference of the compressor 1 can be easily secured.

Further, since the control device 10 raises the set value of the degree of superheat based on the degree of decrease in the outside air temperature, stepwise control becomes possible.

Next, the air conditioner 12 according to the second embodiment of the present invention will be described with reference to FIG. The same members as those of the air conditioner 11 of the first embodiment are designated by the same reference numbers, the description thereof will be omitted, and only the different parts will be described.

FIG. 3 shows a refrigeration cycle system diagram of the air conditioner 12 according to the second embodiment.

As shown in FIG. 3, the air conditioner 12 includes a decompression device 6 on the downstream side of the decompression device 3. In the present embodiment, the decompression device 3 corresponds to the decompression device during normal operation. During normal operation, only the opening degree of the decompression device 3 is controlled, and the opening degree of the decompression device 6 is in the fully open state and is not controlled. When the low outside air temperature is detected, the opening degree of the decompression device 6 is controlled according to the set value of the degree of superheat (steps S5 and S9 in FIG. 2), and the pressure on the suction side of the compressor 1 is increased or decreased.

The opening degree of the decompression device 6 is controlled only when it senses a low outside air temperature. In this way, since the decompression device 6 is provided to increase or decrease the pressure on the suction side of the compressor 1 in response to the change in the set value of the superheat degree, the followability to the change in the set value of the superheat degree is met. High control is possible.

Next, the air conditioner 13 according to the third embodiment of the present invention will be described with reference to FIG. The same members as those of the air conditioner 11 of the first embodiment are designated by the same reference numbers, the description thereof will be omitted, and only the different parts will be described.

FIG. 4 shows a refrigeration cycle system diagram of the air conditioner 13 according to the third embodiment.

As shown in FIG. 4, the air conditioner 13 includes a switching valve 7 and a resistance portion (throttle) 8 which is a pressure reducing device. The resistance portion 8 is, for example, a capillary, and has a larger distribution resistance than the refrigerant pipe 14. In the present embodiment, the decompression device 3 corresponds to the decompression device during normal operation. By switching the switching valve 7, the first circuit 15 in which the refrigerant flows from the pressure reducing device 3 to the user side heat exchanger 4 via the resistance unit 8, or the resistance unit 8 from the pressure reducing device 3 to the user side heat exchanger 4 It is switched to the second circuit 16 in which the refrigerant detours and flows.

The control device 10 uses the second circuit 16 during normal operation, and when it senses a low outside air temperature (outside air temperature is -10 ° C or less), it switches from the second circuit 16 to the first circuit 15 by the switching valve 7 and resists. The refrigerant is depressurized by the part 8 to reduce the pressure on the suction side of the compressor 1. In the present embodiment, the control program shown in FIG. 2 is not executed, and only ON / OFF of the switching valve 7 is performed when the low outside air temperature is detected or when the low outside air temperature is restored. Therefore, the control by the control device 10 at the time of low outside air temperature can be simplified.

Optimal by adopting the air conditioners 11 to 13 according to the first to third embodiments as described above in consideration of the pressure lowering effect on the suction side of the compressor 1, the ease of application, the cost, and the like. You can select an air conditioner with excellent performance.

The present invention is not limited to the above-described examples. A person skilled in the art can make various additions and changes within the scope of the present invention.

For example, in low outside air temperature processing, when the low outside air temperature is detected and the outside air temperature drops by a predetermined temperature or more, the superheat degree setting value is increased, but when the low outside air temperature is detected, the superheat degree setting value is set. You may raise it. Further, in steps S5 and S9 of FIG. 2, the temperature at which the set value of the degree of superheat increases or decreases is the same at Y ° C., but may be different.

1: Compressor 2: Heat source side heat exchanger 3: Decompression device 4: User side heat exchanger 5: Blower, 6: Decompression device, 7: Switching valve, 8: Resistance part, 10: Control device, 11, 12, 13: Air conditioner, 14: Refrigerant piping, 15: 1st circuit, 16: 2nd circuit

Claims (3)

A compressor that compresses the refrigerant and
A heat exchanger on the heat source side that condenses the refrigerant discharged from the compressor,
A decompression device that decompresses the refrigerant condensed by the heat source side heat exchanger, and
A heat exchanger on the utilization side that evaporates the refrigerant from the decompression device,
When a low outside air temperature is detected by the outside air temperature sensor , the decompression device is provided with a control device for depressurizing the refrigerant and reducing the pressure on the suction side of the compressor .
When the control device detects a low outside air temperature by the outside air temperature sensor, the control device raises the set value of the degree of superheat of the refrigerant on the suction side of the compressor, depressurizes the refrigerant by the depressurizing device, and sucks the compressor. Reduce the pressure on the side,
The control device raises the set value of the degree of superheat based on the degree of decrease in the outside air temperature detected by the outside air temperature sensor.
When the temperature drops by a predetermined temperature or more from the outside air temperature previously detected by the outside air temperature sensor, the control device raises the set value of the degree of superheat by a predetermined temperature, and the temperature is determined from the outside air temperature previously detected by the outside air temperature sensor. when elevated above, the air conditioner Ru by a predetermined temperature drop the superheat setting. It is located between the heat source side heat exchanger and the decompression device, and is provided with a decompression device during normal operation that narrows the opening and reduces the pressure of the refrigerant during normal operation.
Wherein the control device, when detecting a low outside air temperature by the outside air temperature sensor, raising the degree of superheat of the set value of the refrigerant on the suction side of the compressor, and the refrigerant pressure is reduced throttle opening degree of the decompression device, The air conditioner according to claim 1, wherein the pressure on the suction side of the compressor is reduced. The decompression device is a resistance portion having a larger flow resistance than the flow path piping.
A decompression device located between the heat source side heat exchanger and the resistance portion, which reduces the opening degree during normal operation and reduces the pressure of the refrigerant during normal operation.
The first circuit in which the refrigerant flows from the decompressor during normal operation to the heat exchanger on the utilization side through the resistance portion, or the resistance portion is bypassed from the decompression device during normal operation to the heat exchanger on the utilization side. The control device includes a switching valve for switching to the second circuit through which the refrigerant flows, and when the control device detects a low outside temperature by the outside air temperature sensor , the switching valve switches from the second circuit to the first circuit and the resistance. The air conditioner according to claim 1, wherein the refrigerant is depressurized by the unit to reduce the pressure on the suction side of the compressor.

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