JPH05240493A - Air conditioner - Google Patents

Abstract

PURPOSE:To enable avoiding hunting in the heating operation by a method wherein, during heating, the operation of an outdoor fan is controlled according to the temperature of a condenser (indoor heat exchanger) on the one hand and on the other hand an expansion valve is controlled in valve opening in such a manner as to bring the degree of superheat of refrigerant at an evaporator (outdoor heat exchanger) to a constant value. CONSTITUTION:When the heating operation mode is set by a remote control 23, the compressor 1 is started; the refrigerant discharged from the compressor 1 flows through a four-way valve 2 to an indoor heat exchanger 5; here the refrigerant liquefies releasing heat to the indoor air; subsequently the refrigerant vaporizes as it flows through a motor-operated expansion valve 4 and an outdoor heat exchanger 3 and then flows back to the compressor 1. During this heating operation, the difference between the temperature in the room and a set point therefor is obtained as an air-conditioning load at a control part 22 and in accordance with the air-conditioning load the operating frequency of the compressor 1 is controlled through an inverter circuit 25. The degree of superheat of refrigerant is also obtained, which is the difference between the temperature of the refrigerant being sucked into the compressor 1 and the temperature of the outdoor heat exchanger 3, and a motor-operated expansion valve 4 is controlled in valve opening in such a manner as to bring the degree of superheat to a constant value.

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 heat pump type refrigeration cycle and capable of cooling and heating operations.

[0002]

2. Description of the Related Art An air conditioner capable of cooling and heating operations has a heat pump type refrigeration cycle shown in FIG.

That is, the outdoor heat exchanger 3 is connected to the discharge port of the compressor 1 via the four-way valve 2, and the outdoor heat exchanger 3 is connected to the outdoor heat exchanger 3.
An indoor heat exchanger 5 is connected to the motor through an electric expansion valve 4, which is a pressure reducer. The indoor heat exchanger 5 is connected to the suction port of the compressor 1 via the four-way valve 2. An outdoor fan 6 for sending outdoor air to the outdoor heat exchanger 3 is provided in the vicinity of the outdoor heat exchanger 3, and an indoor fan 7 for circulating indoor air to the indoor heat exchanger 5 has its indoor heat exchange. It is provided near the container 5.

In this refrigeration cycle, when the four-way valve 2 does not operate, the refrigerant discharged from the compressor 1 is the four-way valve 2, the outdoor heat exchanger 3, the electric expansion valve 4, the indoor heat exchanger 5, and the four-way valve 2 in this order. It flows back to the compressor 1 and a cooling cycle is formed.
As a result, the outdoor heat exchanger 3 becomes the condenser and the indoor heat exchanger 5
Acts as an evaporator.

When the four-way valve 2 operates, the refrigerant discharged from the compressor 1 flows to the compressor 1 in the order of the four-way valve 2, the indoor heat exchanger 5, the electric expansion valve 4, the outdoor heat exchanger 3 and the four-way valve 2. Return, heating cycle is formed. As a result, the indoor heat exchanger 5
Serves as a condenser, and the outdoor heat exchanger 3 serves as an evaporator.

A heat exchanger temperature sensor 11 is attached to the outdoor heat exchanger 3, a heat exchanger temperature sensor 12 is attached to the indoor heat exchanger 5, and a refrigerant temperature sensor 13 is attached to a suction side pipe of the compressor 1. ..

These temperature sensors are for detecting the degree of superheat of the refrigerant in the evaporator. During cooling, the temperature detected by the temperature sensor 13 (evaporator temperature Te) is subtracted from the temperature detected by the temperature sensor 13, and The degree of superheat of the refrigerant in the heat exchanger 5 is detected. During heating, the temperature detected by the temperature sensor 11 (condenser temperature Tc) is subtracted from the temperature detected by the temperature sensor 13, and the degree of superheat of the refrigerant in the outdoor heat exchanger 3 is detected.

Then, the opening degree of the electric expansion valve 4 is controlled so that the detected degree of superheat becomes a constant value. By this constant superheat degree value control, the capacity of the evaporator is brought out to the optimum state regardless of the change in the refrigerant flow rate based on the change in the capacity of the compressor 1.

Further, during heating, the operation of the outdoor fan 6 is on / off controlled according to the condenser temperature Tc detected by the temperature sensor 11 and the fan control condition shown in FIG.
This on / off control is for preventing an abnormal rise in the high-pressure side pressure.

For example, when the load is large, the condenser temperature Tc greatly rises. When this condenser temperature Tc enters the region B of 60 ° C. or higher, the operation of the outdoor fan 6 is turned off. By this operation OFF, the rise of the condenser temperature Tc is suppressed, and the abnormal increase of the high pressure side pressure is prevented. When the condenser temperature Tc falls below 55 ° C. and enters the area A, the operation of the outdoor fan 6 is turned on and the normal operation is restored.

[0011]

By the way, at the start of heating, since the room temperature is still low and is in an overload state, the condenser temperature Tc immediately rises and the operation of the outdoor fan 6 is turned off. At this time, the state of the refrigeration cycle fluctuates greatly, and it becomes impossible for the opening control of the electric expansion valve 4 to follow the fluctuation of the superheat degree.

In this case, as shown in FIG. 7, the superheat cannot be maintained at a constant value, the condenser temperature Tc fluctuates greatly, and the operation of the outdoor fan 6 is frequently turned on and off, so-called hunting. A phenomenon occurs and comfortable heating becomes difficult.

The present invention takes the above circumstances into consideration,
It is an object of the invention to provide an air conditioner that enables comfortable heating while avoiding a hunting phenomenon during heating.

[0014]

An air conditioner of the present invention is a heat pump type refrigeration cycle in which a compressor, a four-way valve, an outdoor heat exchanger, an electric expansion valve and an indoor heat exchanger are sequentially connected, and the outdoor heat exchange. An outdoor fan for sending the outside air to the compressor, a means for returning the refrigerant discharged from the compressor to the compressor through a four-way valve, an indoor heat exchanger, an electric expansion valve, an outdoor heat exchanger, a four-way valve, and performing heating operation, and A means for detecting the temperature of the indoor heat exchanger during heating operation and controlling the operation of the outdoor fan in accordance with the detected temperature, and a superheat of the refrigerant in the outdoor heat exchanger detected during heating operation And a means for controlling the opening degree of the electric expansion valve so that the degree becomes a constant value, and when the outdoor fan operation is stopped during heating operation, the refrigerant discharge temperature of the compressor or the refrigerant discharge temperature of the compressor is given priority over the constant value control of the superheat degree. Set the opening degree of the electric expansion valve And means for maintaining the value.

[0015]

In the air conditioner of the present invention, during the heating operation, the operation of the outdoor fan is controlled according to the temperature of the indoor heat exchanger that works as a condenser, and the overheat of the refrigerant in the outdoor heat exchanger that works as an evaporator is controlled. Is detected, and the opening degree of the electric expansion valve is controlled so that the degree of superheat becomes a constant value. However,
When the outdoor fan operation is stopped, the discharge refrigerant temperature of the compressor or the opening degree of the electric expansion valve is maintained at a constant value in preference to the constant value control of the superheat degree.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In the drawings, the same parts as those in FIG. 5 are designated by the same reference numerals, and detailed description thereof will be omitted.

As shown in FIG. 1, a refrigerant temperature sensor 14 is attached to the discharge side pipe between the discharge port of the compressor 1 and the four-way valve 2. The indoor temperature sensor 1 is provided near the indoor fan 27.
5 are provided.

Reference numeral 20 is a commercial AC power source, and a control unit 22 is connected to the power source 20 via a step-down transformer 21.
The control unit 22 includes a microcomputer and its peripheral circuits, and controls the overall air conditioner.

The control unit 22 is connected with the four-way valve 2, the electric expansion valve 4, the motor for the outdoor fan 6, the motor for the indoor fan 7, and the temperature sensors 11, 12, 13, 14, 15 and remote control. An operation device (hereinafter abbreviated as a remote controller) 23, a timer 24, and an inverter circuit 25 are connected.

The inverter circuit 25 temporarily rectifies the voltage of the power source 20, converts it into an alternating current of a frequency (and voltage) according to a command from the control unit 22, and outputs it.
This output becomes the drive power of the compressor 1. Control unit 22
Has the following functional means. (1) Functional means for controlling the start / stop of the operation and the setting of the operation mode (cooling / heating) according to the operation of the remote controller 23.

(2) During operation, the difference between the indoor temperature set by the remote controller 23 and the temperature detected by the indoor temperature sensor 15 is obtained as an air conditioning load, and the output frequency F of the inverter circuit 25 is controlled according to the air conditioning load. Functional means.

(3) During cooling operation, the difference ΔT between the temperature Ts detected by the temperature sensor 13 and the temperature Te detected by the temperature sensor 12.
(= Ts−Te) is obtained as the degree of superheat of the refrigerant in the indoor heat exchanger 5, and a functional means for controlling the opening degree of the electric expansion valve 4 so that the degree of superheat becomes a predetermined constant value. As the electric expansion valve 4, a pulse motor valve (PMV) whose opening continuously changes according to the number of pulse voltages supplied is used.

(4) During heating operation, the difference ΔT between the temperature Ts detected by the temperature sensor 13 and the temperature Te detected by the temperature sensor 11.
(= Ts-Te) is obtained as the degree of superheat of the refrigerant in the outdoor heat exchanger 3, and the functional means for controlling the opening degree of the electric expansion valve 4 so that the degree of superheat becomes a predetermined constant value.

(5) Functional means for performing on / off control of the operation of the outdoor fan 6 according to the temperature Tc detected by the temperature sensor 11 and the predetermined fan control condition of FIG. 6 during the heating operation.

(6) During heating operation, when the operation of the outdoor fan is stopped, the temperature sensor is given priority over the constant value control of the superheat degree.
Functional means for controlling the opening degree of the electric expansion valve 4 so that the detected temperature Td (discharged refrigerant temperature) of 14 becomes a predetermined constant value. Next, the operation of the above configuration will be described. It is assumed that the cooling operation mode and the desired room temperature are set by the remote controller 23 and the operation start operation is performed. Then,
The compressor 1 is started, and the outdoor fan 6 and the indoor fan 7 are also started. The refrigerant discharged from the compressor 1 flows to the outdoor heat exchanger 3 through the four-way valve 2. In the outdoor heat exchanger 3, the refrigerant takes heat from the outside air and is liquefied.
The refrigerant having passed through the outdoor heat exchanger 3 passes through the electric expansion valve 4 and enters the indoor heat exchanger 5. In this indoor heat exchanger 5, the refrigerant takes heat from the indoor air and vaporizes it. The refrigerant passing through the indoor heat exchanger 5 passes through the four-way valve 2 and is sucked into the compressor 1. In this way, the indoor heat exchanger 5 functions as an evaporator to cool the room.

During this cooling operation, the difference between the indoor temperature detected by the indoor temperature sensor 15 and the indoor temperature set by the remote controller 23 is obtained as an air conditioning load, and the operating frequency of the compressor 1 (that is, the inverter) is determined according to the air conditioning load. The output frequency F of the circuit 25 is controlled. As a result, the optimum cooling capacity corresponding to the air conditioning load can be obtained. In addition, the remote controller 23
It is assumed that the heating operation mode and the desired room temperature are set and the operation start operation is performed.

Then, the compressor 1 is started and at the same time,
The four-way valve 2 is switched, and the outdoor fan 6 is further activated. The indoor fan 7 is started some time after the start of operation. The refrigerant discharged from the compressor 1 flows to the indoor heat exchanger 5 through the four-way valve 2. In this indoor heat exchanger 5, the refrigerant releases heat to indoor air and liquefies. The refrigerant that has passed through the indoor heat exchanger 5 passes through the electric expansion valve 4 and enters the outdoor heat exchanger 3. In this outdoor heat exchanger 3, the refrigerant draws heat from the outside air and vaporizes it. The refrigerant that has passed through the outdoor heat exchanger 3 passes through the four-way valve 2 and is sucked into the compressor 1. In this way, the indoor heat exchanger 5 functions as a condenser to heat the room.

During this heating operation, the difference between the room temperature detected by the room temperature sensor 15 and the room temperature set by the remote controller 23 is obtained as an air conditioning load, and the operating frequency of the compressor 1 (that is, the inverter) is determined according to the air conditioning load. The output frequency F of the circuit 25 is controlled. As a result, the optimum heating capacity corresponding to the air conditioning load can be obtained. Further, during heating operation, the control shown in FIGS. 2 and 3 is executed.

The temperature Ts of the refrigerant sucked into the compressor 1 is detected by the temperature sensor 13, and the temperature Te of the outdoor heat exchanger 3 acting as an evaporator is detected by the temperature sensor 11 to detect both the detected temperatures Ts and Tc. The difference ΔT (= Ts−Te) is obtained. The temperature difference ΔT corresponds to the degree of superheat of the refrigerant in the outdoor heat exchanger 3. The opening degree of the electric expansion valve 4 is controlled so that the degree of superheat becomes a predetermined constant value.

At the same time, the indoor heat exchanger 5 acting as a condenser
The temperature Tc is detected by the temperature sensor 12, and the operation of the outdoor fan 6 is controlled to be turned on and off according to the detected temperature Tc and the fan control condition of FIG. When the heating operation is continuously performed, the condenser temperature Tc gradually rises depending on the load state, and when the set temperature is reached, the operation of the outdoor fan 6 is turned off. When the operation of the outdoor fan 6 is turned off, the discharge temperature constant value control is executed prior to the superheat constant value control.

That is, the temperature Td of the refrigerant discharged from the compressor 1 is detected by the temperature sensor 15, and the opening degree of the electric expansion valve 4 is controlled so that the discharged refrigerant temperature Td becomes a predetermined constant value. It

By executing the discharge temperature constant value control,
The condenser temperature Tc gradually decreases, the outdoor fan 6 is again turned on, and at the same time, the timer 24 counts the time t.
Is started.

Timer 2 with outdoor fan 6 running
When the time count t of 4 reaches a fixed time, for example, 10 minutes, the discharge temperature constant value control based on the discharge refrigerant temperature Td is released there, and the normal superheat degree constant value control is restored.

In this way, the outdoor fan 6 is controlled to be turned on and off in accordance with the load state during the heating operation, and the refrigeration cycle state is greatly changed in response to this, and the operation of the outdoor fan 6 is stabilized. Until then, the discharge temperature constant value control is executed, and as a result, the degree of superheat can be stabilized.

Therefore, it is possible to avoid a hunting phenomenon in which the condenser temperature Tc fluctuates greatly, and the operation of the outdoor fan 6 is repeatedly turned on and off, and comfortable heating can be performed. Instead of the discharge temperature constant value control, control for maintaining the opening Q of the electric expansion valve 4 at a constant value may be adopted. The control in this case is shown in FIG.

That is, when the outdoor fan 6 is turned off, the opening Q of the electric expansion valve 4 is maintained at a constant value. This constant value is a value obtained by multiplying the opening Qa of the electric expansion valve 4 when the outdoor fan 6 is turned off by a numerical value "1.5".

As described above, in the overload state at the time of starting the operation, the state of the refrigeration cycle greatly fluctuates due to the ON / OFF operation control of the outdoor fan 6, and the outdoor fan 6 is dealt with.
By maintaining the opening degree Q of the electric expansion valve 4 at a constant value until the operation of is stabilized, the superheat degree can be stabilized as a result.

Therefore, it is possible to avoid the hunting phenomenon in which the condenser temperature Tc fluctuates greatly, and the operation of the outdoor fan 6 is repeatedly turned on and off frequently, and comfortable heating can be performed. Moreover, in this case, there is no need to provide the refrigerant temperature sensor 14, and the cost can be reduced accordingly.

[0039]

As described above, according to the present invention, when the operation of the outdoor fan is stopped during the heating operation, the discharge refrigerant temperature of the compressor or the opening degree of the electric expansion valve is given priority over the constant value control of the superheat degree. Since the air conditioner is maintained at a constant value, it is possible to provide an air conditioner that avoids the hunting phenomenon during heating and enables comfortable heating.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a refrigeration cycle and a control circuit according to an embodiment of the present invention.

FIG. 2 is a flowchart for explaining the operation of the embodiment.

FIG. 3 is a diagram showing an example of a temperature change, an outdoor fan operating state, and a degree of superheat change in the embodiment.

FIG. 4 is a flowchart for explaining an operation of a modified example of the same embodiment.

FIG. 5 is a configuration diagram of a refrigeration cycle of a conventional air conditioner.

FIG. 6 is a diagram showing fan control conditions in the embodiment and a conventional air conditioner.

FIG. 7 is a diagram showing an example of a temperature change, an outdoor fan operating state, and a superheat degree change in a conventional air conditioner.

[Explanation of symbols]

1 ... Compressor, 2 ... Four-way valve, 3 ... Outdoor heat exchanger, 4 ... Electric expansion valve, 5 ... Indoor heat exchanger, 6 ... Outdoor fan, 7 ... Indoor fan, 11, 12 ... Heat exchanger temperature sensor, 13, 14
... Refrigerant temperature sensor, 15 ... Indoor temperature sensor, 22 ... Control unit.

Claims (1)

[Claims] 1. A heat pump refrigeration cycle in which a compressor, a four-way valve, an outdoor heat exchanger, an electric expansion valve, and an indoor heat exchanger are sequentially connected, an outdoor fan that sends outside air to the outdoor heat exchanger, and the compressor. The discharge refrigerant of is returned to the compressor through the four-way valve, the indoor heat exchanger, the electric expansion valve, the outdoor heat exchanger, and the four-way valve, and means for executing the heating operation, and the temperature of the indoor heat exchanger during the heating operation. A means for detecting and controlling the operation of the outdoor fan in accordance with the detected temperature; and, during heating operation, detecting the degree of superheat of the refrigerant in the outdoor heat exchanger and keeping the degree of superheat of the electric expansion valve constant. A means for controlling the opening degree, and when the outdoor fan operation is stopped during the heating operation, the refrigerant discharge temperature of the compressor or the opening degree of the electric expansion valve is maintained at a constant value in preference to the constant value control of the superheat degree. And means for Air conditioner to do.