JP7465827B2 - Refrigeration Cycle Equipment - Google Patents

Description

This invention relates to refrigeration cycle devices, such as air conditioners.

In the past, this type of device used a discharge temperature sensor to detect the temperature of the refrigerant discharged from a compressor located midway through the refrigerant circuit. When an abnormality occurred and the compressor discharge temperature rose abnormally, the compressor rotation speed was reduced by a predetermined value if it was determined that the discharge temperature was equal to or higher than a predetermined first temperature, and the compressor was stopped if it was determined that the discharge temperature was equal to or higher than a predetermined second temperature that is higher than the first temperature. (For example, see Patent Document 1)

JP 2020-153600 A

However, with this conventional system, when the compressor is operated at a low load in early spring or early autumn, an abnormal increase in discharge temperature occurs. If the discharge temperature is determined to be above a predetermined first temperature and the compressor speed is reduced by a predetermined value, if the amount of refrigerant sealed in the refrigerant circuit has decreased due to a slow refrigerant leak or the like, the discharge temperature will not drop to the normal value. However, since the compressor speed is still relatively low due to the low load, the speed is further reduced and the discharge temperature does not rise to the predetermined second temperature, so operation may continue without being stopped.
Because the compressor is operated at a higher discharge temperature than during normal operation, the operating efficiency remains low for a long period of time, leaving room for improvement.

In order to solve the above problems, the present invention provides a refrigerant circuit in which a compressor, a condenser, an expansion valve, and an evaporator are connected by piping to circulate a refrigerant;
a discharge temperature sensor that detects a discharge temperature of the refrigerant discharged from the compressor;
a control unit which varies a rotation speed of the compressor and an opening degree of the expansion valve, limits the rotation speed of the compressor and increases the opening degree of the expansion valve when it is determined that the discharge temperature detected by the discharge temperature sensor is equal to or higher than a predetermined first temperature, and forcibly stops the compressor when it is determined that the discharge temperature detected by the discharge temperature sensor is equal to or higher than a predetermined second temperature higher than the first temperature,
The control unit counts the time during which the temperature detected by the discharge temperature sensor is equal to or higher than the predetermined first temperature and equal to or higher than a predetermined third temperature which is lower than the predetermined second temperature, and the opening of the expansion valve is equal to or higher than a predetermined opening, and is characterized in that it issues an error alert when it determines that the counted time has reached or exceeded the predetermined time.

In addition, claim 2 is characterized in that the control unit forcibly stops the compressor when it determines that the counted time is equal to or greater than the predetermined time.

In addition, in claim 3, the control unit is characterized in that it resets the counted time if it determines that the temperature detected by the discharge temperature sensor falls below the third predetermined temperature before the counted time reaches the predetermined time.

According to this invention, the discharge temperature sensor detects a temperature equal to or higher than a predetermined third temperature, which is higher than a predetermined first temperature and lower than a predetermined second temperature, and the time during which the opening of the expansion valve is equal to or higher than the predetermined opening is counted. If it is determined that the counted time has reached or exceeded the predetermined time, an error is notified, thereby preventing the unit from continuing to operate for long periods of time with poor operating efficiency.

FIG. 1 is a schematic diagram showing an embodiment of the present invention; FIG. 2 is a control block diagram of the embodiment. A flowchart illustrating the operation when the discharge temperature rises in the embodiment. FIG. 4 is a diagram illustrating the relationship between the discharge temperature and the expansion valve opening degree in the embodiment. Schematic diagram of another embodiment of the present invention.

Next, an embodiment of an air conditioner, which is a type of refrigeration cycle apparatus to which the present invention is applied, will be described with reference to the drawings.
Please refer to Fig. 1. Reference numeral 1 denotes an indoor unit installed indoors, and reference numeral 10 denotes an outdoor unit installed outdoors, and an air conditioner is configured that is capable of normal operation such as cooling operation and heating operation by refrigerant flowing through a refrigerant circuit 20 that connects the indoor unit 1 and the outdoor unit 10 with piping.

Refer to Figure 1. The indoor unit 1 is equipped with an indoor heat exchanger 2 in which a refrigerant flows through multiple pipes, a crossflow fan 3 as an indoor fan that supplies indoor air to the indoor heat exchanger 2, a room temperature sensor 4 for detecting the room temperature, and an indoor lamp 5 composed of an LED located on the outer surface of the housing that constitutes the indoor unit 1.

Refer to Figure 1. The outdoor unit 10 is equipped with a compressor 11 that compresses the refrigerant to a high temperature and high pressure, a four-way valve 12 that changes the flow direction of the refrigerant, an expansion valve 13 that expands the refrigerant to a low temperature and low pressure, an outdoor heat exchanger 14 in which the refrigerant flows through multiple pipes provided inside, a blower fan 15 that serves as an outdoor fan that supplies outside air toward the outdoor heat exchanger 14, an outdoor heat exchange sensor 16 that detects the temperature of the outdoor heat exchanger 14, and a discharge temperature sensor 17 that detects the temperature of the refrigerant discharged from the compressor 11.

Refer to Figure 1. 30 is a remote control that sets the operation mode and set temperature of the indoor unit 1. The remote control 30 is equipped with an operation button 31 that instructs starting and stopping operation, an operation switch button 32 that switches between each operation mode such as heating operation and cooling operation, a temperature setting button 33 that changes the set temperature in each operation mode, and a display 34 that shows the room temperature, set temperature, current time, etc.

See Figures 1 and 2. 40 is a control unit made up of a microcomputer, which issues specific instructions to each functional component according to the detection values of sensors installed in each part of the indoor unit 1 and the outdoor unit 10.

Next, the basic operation of this embodiment will be described.
Please refer to Fig. 1. When heating operation is selected by operation switch button 32 installed on remote control 30, control unit 40 operates four-way valve 12 so that refrigerant flows through refrigerant circuit 20 in the direction of solid lines, and instructs compressor 11 to operate at a predetermined rotation speed. As a result, high-temperature, high-pressure gas refrigerant flows into indoor heat exchanger 2, and indoor heat exchanger 2 functions as a condenser. Indoor air supplied by cross-flow fan 3 is heated by indoor heat exchanger 2 acting as a condenser, and warm air is blown into the room from an air outlet (not shown).

The refrigerant flowing out of the indoor heat exchanger 2 is decompressed by the expansion valve 13, and becomes a low-temperature, low-pressure liquid refrigerant, which flows into the outdoor heat exchanger 14. The liquid refrigerant that flows into the outdoor heat exchanger 14, which functions as an evaporator, is heated by the outdoor air supplied by the blower fan 15, and evaporates, becoming a gas refrigerant, which flows into the compressor 11. In this way, the refrigerant flows through the refrigerant circuit 20, making heating operation possible.

When cooling operation is selected with the operation switch button 32 installed on the remote control 30, the four-way valve 12 is operated so that the refrigerant flows through the refrigerant circuit 20 in the direction of the dashed line, and the compressor 11 is instructed to operate at a specified rotation speed. As a result, the gas refrigerant discharged from the compressor 11 flows in the direction of the dashed arrow and into the outdoor heat exchanger 14, which functions as a condenser. The refrigerant in the outdoor heat exchanger 14 condenses by exchanging heat with the outdoor air supplied by the blower fan 15.

The refrigerant that flows from the outdoor heat exchanger 14 into the expansion valve 13 is reduced in pressure to become a low-temperature, low-pressure liquid refrigerant, which then flows into the indoor heat exchanger 2, which functions as an evaporator. The refrigerant in the indoor heat exchanger 2 is cooled by heat exchange with indoor air supplied by the cross-flow fan 3, and the cold air is blown out from an air outlet (not shown). In this way, the refrigerant flows through the refrigerant circuit 20, making it possible to perform cooling operation or dehumidification operation to reduce indoor humidity.

When performing normal operation such as heating operation or cooling operation, the control unit 40 controls the rotation speed of the compressor 11 and the opening degree of the expansion valve 13 so that the discharge temperature detected by the discharge temperature sensor 17 becomes the target discharge temperature. If the difference between the set room temperature and the room temperature is large, the target discharge temperature is increased to perform operation at a high load, and if the difference between the set room temperature and the room temperature is small, the target discharge temperature is decreased to perform operation at a low load.

In general, when normal operation is performed in the summer when the outdoor temperature is high, or in the winter when the outdoor temperature is low, the difference between the set temperature and the room temperature is large, so the unit is likely to operate at a high load. On the other hand, when normal operation is performed in the early spring or early autumn, the difference between the set temperature and the room temperature is small, so the unit is likely to operate at a low load.

Next, the control performed when the temperature of the refrigerant discharged from the compressor 11 increases abnormally will be described in detail.
3, when normal operation such as heating operation or cooling operation is being performed, the control unit 40 determines whether the discharge temperature detected by the discharge temperature sensor 17 is equal to or higher than the predetermined first temperature of 100° C. (step S101).

If the result of the determination in step S101 is that the discharge temperature is less than 100°C (No in step S101), it is determined that there is no abnormal increase in the temperature of the refrigerant discharged from the compressor 11, and the control unit 40 continues normal operation to bring the temperature detected by the discharge temperature sensor 17 closer to the target discharge temperature (step S102).

Furthermore, if the result of the determination in step S101 is that the discharge temperature is 100° C. or higher (Yes in step S101), the control unit 40 starts a control to limit the rotation speed of the compressor 11 to (current value-Xrps) and to increase the opening degree of the expansion valve 13 by a predetermined value at predetermined time intervals (step S102). This makes it possible to suppress an increase in the discharge temperature.
The rotation speed of the compressor 11 may be limited by a method of reducing the rotation speed of the compressor 11 to a predetermined low rotation speed value.

After performing the processing of step S102, the control unit 40 determines whether the discharge temperature detected by the discharge temperature sensor 17 is equal to or higher than the predetermined third temperature of 105°C (step S104). If it determines that the discharge temperature is equal to or higher than 105°C (Yes in step S104), it determines whether the current opening of the expansion valve 13 is fully open or equal to or higher than 500 pps, which is a predetermined opening close to full open (step S105). If it determines that the opening of the expansion valve 13 is equal to or higher than 500 pps (Yes in step S105), it starts counting the time during which the discharge temperature is equal to or higher than 105°C and the opening of the expansion valve 13 is equal to or higher than 500 pps, and stores the time count value (step S106).

If it is determined in step S105 that the current opening of the expansion valve 13 is less than 500 pps (No in step S105) or if the processing of step S106 is performed, the control unit 40 determines whether the discharge temperature detected by the discharge temperature sensor 17 is less than the predetermined second temperature of 115°C (step S107), and if it is determined that the discharge temperature is less than 115°C (Yes in step S107), it determines whether the time count value during which the discharge temperature is equal to or greater than 105°C but less than 115°C and the opening of the expansion valve 13 continues to be equal to or greater than 500 pps is equal to or greater than 20 minutes (step S108).

If it is determined in step S108 that the time count value is 20 minutes or more (Yes in step S108), the control unit 40 stops the compressor 11, blinks the indoor lamp 5, and notifies the user of the error by displaying a symbol indicating an error on the display 34 of the remote control 30 (step S109), and ends the control.

If it is determined in step S107 that the discharge temperature detected by the discharge temperature sensor 17 is 115°C or higher (No in step S107), the control unit 40 immediately stops the compressor 11, blinks the interior lamp 5, and performs a forced stop operation to notify the user of the error by displaying a symbol indicating an error on the display 34 of the remote control 30 (step S110).

If it is determined in step S108 that the time count value during which the discharge temperature is equal to or higher than 105°C and lower than 115°C and the opening degree of the expansion valve 13 is equal to or higher than 500 pps is less than 20 minutes, or that there is no time count value, the control unit 40 performs the determination in step S104.

If it is determined in step S104 that the discharge temperature detected by the discharge temperature sensor 17 is less than 105°C, the control unit 40 determines whether a time count value during which the discharge temperature was equal to or greater than 105°C and less than 115°C and the opening of the expansion valve 13 was equal to or greater than 500 pps has been stored (step S111), and if it is determined that a time count value has been stored (Yes in step S111), it resets the stored time count value (step S112).

If it is determined in step S111 that the time count value during which the discharge temperature is equal to or higher than 105°C and lower than 115°C and the opening degree of the expansion valve 13 is equal to or higher than 500 pps is not stored (No in step S111), or if the stored time count value is reset in step S112, the control unit 40 performs the determination in step S101.

With reference to Fig. 4, if refrigerant leaks from the refrigerant circuit 20 due to a slow leak or the like while normal operation such as heating operation or cooling operation is being performed, the amount of refrigerant circulating in the refrigerant circuit 20 decreases, and the discharge temperature of the refrigerant discharged from the compressor 11 increases.
When the discharge temperature sensor 17 detects a predetermined first temperature of 100°C or higher, the rotation speed of the compressor 11 is reduced and the opening of the expansion valve 13 is opened and increased at predetermined time intervals, thereby controlling the discharge temperature to decrease.

During periods of high-load operation, such as heating operation in winter and cooling operation in summer, the target discharge temperature is high and the compressor 11 is driven at a relatively high rotation speed. In this case, if a large amount of refrigerant sealed in the refrigerant circuit 20 leaks out, the rotation speed of the compressor 11 is reduced and the opening of the expansion valve 13 is increased, but the discharge temperature continues to rise. As shown by the dashed line in Figure 4, the discharge temperature reaches 115°C, which is the predetermined second temperature at which operation is forcibly stopped. Operation is forcibly stopped and an error is issued, making it possible to prevent operation from continuing at a low operating efficiency.

However, during heating operation in early spring or cooling operation in early autumn, the difference between the outdoor air temperature and the indoor set temperature is small, and it is possible to maintain the indoor temperature close to the set temperature with a relatively small load. The target discharge temperature is low and the compressor 11 is operated at a relatively low rotation speed. In this case, if a small amount of refrigerant sealed in the refrigerant circuit 20 leaks out due to a slow leak or the like, even if the rotation speed of the compressor 11 is reduced and the opening of the expansion valve 13 is increased, the temperature detected by the discharge temperature sensor 17 will remain between the specified first temperature of 100°C and the specified second temperature of 115°C, as shown by the solid line in Figure 4, and normal operation will continue.

Compared to normal operation, continuing operation with the compressor 11 rotation speed reduced and the expansion valve 13 widely open is not desirable because it will result in poor operating efficiency continuing for a long period of time.

Therefore, if it is determined that the discharge temperature detected by the discharge temperature sensor 17 is higher than the first predetermined temperature of 100°C and is equal to or higher than the third predetermined temperature of 105°C, which is lower than the second predetermined temperature of 115°C, and the opening degree of the expansion valve 13 is equal to or higher than the predetermined opening degree of 500 pps for a predetermined period of time of 20 minutes or more, the compressor 11 is stopped and an error is notified, thereby preventing a state of inefficient operation from continuing for a long period of time.

Next, we will explain the effects of the present invention.

When the discharge temperature sensor 17 detects a third temperature of 105°C or higher, which is higher than the first temperature of 100°C and lower than the second temperature of 115°C, and the opening of the expansion valve 13 is at or above the predetermined opening of 500 pps, the time is counted. If it is determined that the counted time has reached or exceeded the predetermined time of 20 minutes, an error is notified by flashing the interior lamp 5 and displaying a predetermined symbol on the display 34 of the remote control 30, thereby preventing the unit from continuing to operate for long periods with poor operating efficiency.

In addition, if the discharge temperature sensor 17 detects that the temperature is between 105°C and 115°C, and the opening of the expansion valve 13 is 500 pps or more and the counted time exceeds the specified time of 20 minutes, the compressor 11 is forcibly stopped, thereby preventing a state in which poor operating efficiency and a heavy load are continuously applied to the compressor 11.

In addition, if the temperature detected by the discharge temperature sensor 17 is greater than 105°C but less than 115°C and the opening of the expansion valve 13 is greater than 500 pps, and it is determined that the temperature detected by the discharge temperature sensor 17 has fallen below the predetermined third temperature of 105°C before the counted time reaches the predetermined time of 20 minutes, the counted time is reset. This prevents frequent error notifications and forced shutdowns of the compressor 11 when the operating efficiency is not too poor, which can lead to a decrease in usability for the user.

In this embodiment, an error is reported and a decision is made to stop the compressor 11 depending on whether the temperature detected by the discharge temperature sensor 17 is equal to or higher than 105°C and lower than 115°C and the opening degree of the expansion valve 13 is equal to or higher than 500 pps for 20 minutes or more. However, control may also be performed by counting the time accumulated over the intermittent state.
In other words, even if the temperature detected by the discharge temperature sensor 17 temporarily escapes from a state in which it is equal to or higher than 105°C and lower than 115°C, and the opening degree of the expansion valve 13 is equal to or higher than 500 pps, if the same state is again reached, time counting may be started, and an error may be issued and a decision may be made to stop the compressor 11 if the accumulated time count value reaches or exceeds the specified time of 20 minutes.

The predetermined first temperature to the third temperature and the opening degree of the expansion valve 13 described in this embodiment are merely examples and may be changed as appropriate without departing from the spirit of the present invention, and the predetermined first temperature and the predetermined third temperature may be the same value.

In the present embodiment, the refrigeration cycle device has been described as an air conditioner in which the refrigerant in the refrigerant circuit 20 circulates directly through the indoor heat exchanger 2 in the indoor unit 1, but the present invention is not limited to this.
As another embodiment, a refrigeration cycle apparatus having a water circuit 50 in the outdoor unit 10 will be described.

With reference to Fig. 5, the outdoor unit 10 includes a water circuit 50 through which water circulates, in addition to the refrigerant circuit 20 through which the refrigerant circulates.
The water circuit 50 is equipped with a water-refrigerant heat exchanger 51 capable of exchanging heat between water and a refrigerant, an auxiliary heater 52 that heats the water after heat exchange in the water-refrigerant heat exchanger 51, a water tank 53 that stores a predetermined amount of water, a circulation pump 54 that circulates the water in the water circuit 50 in the direction of the arrow, and a water temperature sensor 55 that detects the temperature of the water after passing through the water-refrigerant heat exchanger 51.
The other symbols are the same as those in the embodiment already described, and therefore the description thereof will be omitted.

One end of the four-way valve 12 installed in the refrigerant circuit 20 and one end of the expansion valve 13 are connected to a water-refrigerant heat exchanger 51, and heat is exchanged within the water-refrigerant heat exchanger 51. By controlling the rotation speed of the compressor 11 and the opening of the expansion valve 13 so that the temperature of the water exchanged in the water-refrigerant heat exchanger 51 and detected by the water temperature sensor 55 becomes the target temperature, water at the target temperature flows into the indoor heat exchanger 2 in the indoor unit 1, and normal operation such as cooling operation or heating operation can be performed.

When heating operation is in progress, if the outside air temperature is low and the water in the water circuit 50 cannot be sufficiently heated by heat exchange in the water-refrigerant heat exchanger 51 alone, the auxiliary heater 52 is driven. By using the auxiliary heater 52 to reheat the water after heat exchange in the water-refrigerant heat exchanger 51, it is possible to prevent a lack of heating sensation.

When the auxiliary heater 52 is driven, the temperature of the water that has exchanged heat in the indoor heat exchanger 2 and is returning to the water-refrigerant heat exchanger 51 increases. Therefore, the target hot water temperature can be reached without increasing the temperature of the refrigerant flowing into the water-refrigerant heat exchanger 51, so the load on the refrigerant circuit 20 side is reduced and the target discharge temperature of the compressor 11 becomes relatively low.
At this time, if a refrigerant leak occurs in the refrigerant circuit 20, the discharge temperature of the refrigerant discharged from the compressor 11 will increase, and control will be implemented to limit the rotation speed of the compressor 11 and to increase the opening of the expansion valve 13. However, there is a risk that the temperature detected by the discharge temperature sensor 17 will not reach the specified second temperature of 115°C, and operation with inefficient operation will continue.

The discharge temperature sensor 17 detects a third temperature of 105°C or higher, which is higher than the first temperature of 100°C and lower than the second temperature of 115°C, and the time when the opening of the expansion valve 13 is at or above the predetermined opening of 500 pps is counted. If it is determined that the counted time is at or above the predetermined time of 20 minutes, the compressor 11 is stopped, the interior lamp 5 is turned on and off, and a predetermined symbol or the like is displayed on the display 34 of the remote control 30 to notify of an error. Therefore, in a device that uses a heat source such as an auxiliary heater 52 on the water circuit 50 side, it is possible to prevent long periods of operation with poor operating efficiency.

In this way, in a refrigeration cycle device configured to maintain the indoor temperature at a predetermined value by heat exchange with the refrigerant in the refrigerant circuit 20 using a water-refrigerant heat exchanger 51 or the like, it is possible to prevent a state of inefficient operation from continuing by implementing the control of the present invention.

2 Indoor heat exchanger 11 Compressor 13 Expansion valve 14 Outdoor heat exchanger 17 Discharge temperature sensor 20 Refrigerant circuit 40 Control unit

Claims (3)

A refrigerant circuit in which a compressor, a condenser, an expansion valve, and an evaporator are connected by piping and a refrigerant circulates;
a discharge temperature sensor that detects a discharge temperature of the refrigerant discharged from the compressor;
a control unit which varies a rotation speed of the compressor and an opening degree of the expansion valve, limits the rotation speed of the compressor and increases the opening degree of the expansion valve when it is determined that the discharge temperature detected by the discharge temperature sensor is equal to or higher than a predetermined first temperature, and forcibly stops the compressor when it is determined that the discharge temperature detected by the discharge temperature sensor is equal to or higher than a predetermined second temperature higher than the first temperature,
The control unit counts the time during which the temperature detected by the discharge temperature sensor is equal to or higher than the predetermined first temperature and equal to or higher than a predetermined third temperature which is lower than the predetermined second temperature, and the opening of the expansion valve is equal to or higher than a predetermined opening, and when it determines that the counted time has reached or exceeded the predetermined time, it issues an error alert. The refrigeration cycle device according to claim 1, characterized in that the control unit forcibly stops the compressor when it determines that the counted time is equal to or greater than the predetermined time. The refrigeration cycle device according to claim 1 or 2, characterized in that the control unit resets the counted time if it determines that the temperature detected by the discharge temperature sensor falls below the third predetermined temperature before the counted time reaches the predetermined time.

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