JP2002228234A - Air conditioner and its control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high efficiency air conditioner with reduced electric power consumption when a load of the air conditioner is reduced, i.e., when the number of revolutions of a refrigerant compressor is small. SOLUTION: In a freezing cycle wherein a refrigerant compressor with variable number of revolutions, an outdoor heat exchanger including a fresh air temperature detector and an outdoor air fan, an expander, and an indoor heat exchanger are coupled in succession, there is employed an electric motor as an electric motor for driving the foregoing outdoor air fan which electric motor has the variable number of revolutions and in which a permanent magnet is employed for a rotator, and further the number of revolutions of the outdoor fan is controlled in response to the number of revolutions of the refrigerant compressor and fresh air temperature detected by the foregoing fresh air temperature detector.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air conditioner using a refrigeration cycle, and more particularly to a cooling system using a motor having a variable rotation speed as a motor for driving an outdoor fan and using a permanent magnet as a rotor. The present invention relates to an air conditioner suitable for an operation and a heating operation and a control method thereof.

[0002]

2. Description of the Related Art There is a method of improving energy saving and comfort by using an air conditioner using a motor whose rotation speed is variable as a motor for driving a refrigerant compressor and an outdoor fan constituting a refrigeration cycle. Various proposals have been made. For example, as disclosed in Japanese Patent Application Laid-Open No. 10-185284, the number of rotations of an electric motor that drives an outdoor fan is controlled in accordance with the outdoor air temperature, the indoor air temperature, and the rotation number of a refrigerant compressor. Method.

As another example, see, for example,
As disclosed in JP-A-148378, when the difference between the temperature of the outdoor heat exchanger and the temperature of the outside air exceeds a preset value, the outdoor heat exchanger converges to the temperature just before frost formation. And a method of controlling the rotation speed of an electric motor that drives an outdoor fan.

[0004]

If the rotation speed of the refrigerant compressor is variable and the air-conditioning load is small, the rotation speed of the refrigerant compressor is reduced by the above-described control method, whereby the refrigerant in the refrigeration cycle is reduced. The amount of circulation can be reduced and the generation capacity of the air conditioner can be reduced. Therefore, the amount of refrigerant flowing through the heat exchanger is reduced, and the required capacity of the heat exchanger is reduced. Therefore, it is possible to reduce the rotation speed of the electric motor that drives the fan provided in the heat exchanger, reduce the air volume of the heat exchanger, and reduce the capacity of the heat exchanger. As described above, by reducing the rotation speed of the fan provided in the heat exchanger, it is possible to reduce the capacity of the heat exchanger and further reduce the generation capacity of the air conditioner.

However, in an induction motor using a cage winding which has been conventionally used as a motor for driving a fan as a motor rotor, the number of rotations of the motor decreases and the efficiency of the motor decreases remarkably. Although the generation capacity of the air conditioner can be reduced, the reduction in power consumption of the air conditioner is smaller than the reduction in the generation capacity of the air conditioner. And the ratio of the power consumption of the air conditioner is reduced.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and as a motor for driving an outdoor fan used in an air conditioner, the number of rotations is variable and a permanent magnet is provided on a rotor. By using the brushless DC motor used as an electric motor, a high-efficiency air conditioner and a control method for the air conditioner with low load on the air conditioner, that is, low power consumption of the air conditioner when the rotation speed of the refrigerant compressor is low, are used. Is to provide.

[0007]

In order to achieve the above object, an air conditioner and a control method thereof according to the present invention are characterized by what is described in the claims. However, the air conditioner according to claim 1 as an apparatus invention includes at least a refrigerant compressor having a variable rotation speed, an outdoor heat exchanger having an outdoor air temperature detector and an outdoor fan, an expander, and an indoor heat exchanger. In an air conditioner using a refrigeration cycle formed by sequentially connecting these devices, the rotation speed is variable as an electric motor that drives the outdoor fan,
And a motor using a permanent magnet for the rotor, and control for using the motor to control the rotation speed of the outdoor fan according to the rotation speed of the refrigerant compressor and the outside air temperature detected by the outside air temperature detector. And means.

[0008] A method of controlling an air conditioner according to a second aspect of the present invention uses the air conditioner of the first aspect, wherein the rotation speed of the refrigerant compressor is lower than a predetermined rotation speed. And during the cooling operation, when the outside air temperature detected by the outside air temperature detector is lower than a predetermined temperature or during the heating operation, the outside air temperature detected by the outside air temperature detector is higher than a predetermined temperature, The rotation speed of the outdoor fan is set lower than a predetermined rotation speed.

A method of controlling an air conditioner according to a third aspect of the present invention uses the air conditioner according to the first aspect of the present invention, wherein the number of rotations of the refrigerant compressor is set to a minimum settable number of rotations. At certain times, and during the cooling operation, the outside air temperature detected by the outside air temperature detector is lower than a predetermined temperature, or during the heating operation, the outside air temperature detected by the outside air temperature detector is higher than the predetermined temperature. In some cases, the rotation speed of the outdoor fan is set lower than a predetermined rotation speed.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An air conditioner and an air conditioner control method according to an embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 shows an embodiment of an air conditioner using a refrigeration cycle capable of controlling the outdoor fan rotation speed in accordance with the outside air temperature and the rotation speed of the refrigerant compressor.

An outdoor heat exchanger 3 equipped with a refrigerant compressor 1 having a built-in refrigerant compressor motor 10 whose rotation speed is variable, a four-way valve 2, an outdoor air temperature detector 12 and an outdoor fan 4 driven by an outdoor fan motor 11. The outdoor expander 5, the liquid receiver 6, the indoor expander 7, and the indoor heat exchanger 8 including the indoor blower 9 are sequentially connected to form a refrigeration cycle. The refrigerant compressor 1, the four-way valve 2, the outdoor heat exchanger 3, the outdoor fan 4, the outdoor expander 5, and the liquid receiver 6 are collectively stored as an outdoor unit 20 in a housing. On the other hand, the indoor heat exchanger 8 and the indoor expander 7 are collectively referred to as an indoor unit 21 and housed in a housing.

Further, the control device for the air conditioner of the present invention comprises:
A refrigerant compressor motor control device 30 incorporating refrigerant compressor motor control means for controlling the refrigerant compressor motor 10 according to the refrigerant compressor rotation speed determined by the indoor air conditioning load;
An outdoor fan motor control device 31 including an outdoor fan motor control means for controlling the outdoor fan motor 11 according to the refrigerant compressor rotation speed and the outdoor air temperature detected by the outdoor air temperature detector 12 is particularly provided. Further, a brushless DC motor using a permanent magnet for a rotor is adopted as the outdoor fan motor 11 for driving the outdoor fan 4.

FIG. 2 shows the motor efficiency of the induction motor and the brushless DC motor with respect to the motor speed, and FIG. 3 shows the motor power consumption with respect to the motor speed of both motors. The motor efficiency of the brushless DC motor employed in the present invention is generally higher over the entire motor speed than the conventional induction motor, and the difference between the two is large especially in a region where the motor speed is small.

The motor power consumption of the brushless DC motor with respect to the motor speed is lower than that of the induction motor.
And the reduction rate is larger than that of the induction motor. That is, when the brushless DC motor is used, the power consumption of the outdoor fan motor 11 can be significantly reduced by reducing the rotation speed of the outdoor fan motor 11. Therefore, when the rotation speed of the outdoor fan motor 11 can be controlled, the power consumption of the outdoor fan motor 11 can be suppressed, and a highly efficient air conditioner can be provided.

In particular, during the cooling operation, the outdoor heat exchanger 3 acts as a condenser. Therefore, when the rotation speed of the outdoor fan 4 is reduced, the capacity as the condenser is reduced, and as a result, the discharge of the refrigerant compressor 1 is performed. Since the side pressure increases and the power consumption of the refrigerant compressor 1 increases, the power consumption of the refrigerant compressor 1 is increased by using a brushless DC motor having high motor efficiency in a region where the rotation speed of the outdoor fan motor 11 is low. Thus, it is possible to provide a highly efficient air conditioner in which the reduction in power consumption of the outdoor fan motor 11 is greater than the increase in power consumption.

Further, since the outdoor heat exchanger 3 is installed outdoors, the ventilation resistance of the heat exchanger increases due to the attachment of dust and the like. At this time, when an induction motor is used as the outdoor fan motor 11 for driving the outdoor fan 4,
Conventionally, since the rotation speed is not detected and the rotation speed control is not performed, the load on the outdoor fan motor 11 increases due to the increase in the ventilation resistance of the heat exchanger, and the rotation speed of the outdoor fan motor 11 decreases. The rotation speed of the fan 4 also decreases.

Accordingly, especially during the heating operation, the outdoor heat exchanger 3 acts as an evaporator. Therefore, if no dust adheres to the outdoor heat exchanger 3, the rotation speed of the outdoor fan 4 does not frost. However, when the dust is attached and the number of rotations of the outdoor fan 4 is reduced, the evaporation ability is also reduced, and the outdoor heat exchanger 3 is frosted due to the reduced evaporation temperature.
Therefore, it is necessary for the air conditioner to perform a defrosting operation, resulting in a decrease in operating efficiency and a significant decrease in comfort.

On the other hand, in the brushless DC motor, a sensor for detecting the position of the magnetic pole of the permanent magnet of the rotor is used or the current waveform is detected to detect the position of the magnetic pole. Generally, the sensor signal is fed back to control the rotation speed to be constant. Therefore, even if dust adheres to the outdoor heat exchanger 3, the rotation speed of the outdoor fan 4 does not decrease.
If the operating condition does not cause frost in a state where dust is not attached, frost does not occur even if dust is attached.

The capacity of the heat exchanger is determined by the area of the heat exchanger and the wind speed passing through the fins constituting the heat exchanger, that is, the air volume of the heat exchanger. In other words, the greater the area of the heat exchanger and the greater the air flow of the heat exchanger, the greater the capacity of the heat exchanger. When determining the capacity of the heat exchanger, first, the rated capacity of the air conditioner is secured, and then, under overload conditions, for example, when the outside air temperature is extremely high during cooling operation, the outdoor heat exchanger of the air conditioner The capacity of the heat exchanger is set so that the condensing pressure at 3 does not increase and does not exceed the design pressure of each device constituting the air conditioner and significantly lower the reliability of the air conditioner.

Further, the area and the air volume of the outdoor heat exchanger 3 are generally set to be as small as possible in order to reduce the size of the housing of the outdoor unit 20. Under the load condition, the outdoor fan motor 11 for driving the outdoor fan 4 is set to have the maximum rotation speed of the outdoor fan motor 11, that is, the outdoor heat exchanger 3
Is set so that the air volume of the air becomes maximum.

Therefore, when the indoor air-conditioning load is small, that is, when the generation capacity of the air conditioner may be small,
This is addressed by setting the rotational speed of the refrigerant compressor 1 low and reducing the amount of circulating refrigerant. At this time, since the capacity of the heat exchanger may be small, the air volume of the heat exchanger can be reduced. However, the air volume of the indoor heat exchanger 8 is determined by the person using the air conditioner, and therefore cannot be controlled by the air conditioner. Control of the air volume of the outdoor heat exchanger 3 is possible.

The capacity of the outdoor heat exchanger 3 changes depending on the outside air temperature. During the cooling operation, the outdoor heat exchanger 3 acts as a condenser.
Since the temperature difference with the refrigerant flowing through the inside increases, the capacity of the condenser is improved. On the other hand, during the heating operation, the outdoor heat exchanger 3
Acts as an evaporator, so that the higher the outside air temperature, the greater the temperature difference between the refrigerant and the refrigerant flowing in the outdoor heat exchanger 3, so that the capacity of the evaporator is improved. Therefore, the rotational speed of the outdoor fan motor 11 is determined by the outdoor fan motor control device 31 from the rotational speed of the refrigerant compressor 1 determined by the indoor air-conditioning load and the outdoor air temperature detected by the outdoor air temperature detector 12. By determining the number of revolutions of 4, an air conditioner that consumes less power and can operate with high efficiency can be provided.

Next, a first embodiment of the control method for an air conditioner as described above will be described.

If the rotation speed of the outdoor fan motor 11 is frequently changed according to the change in the rotation speed of the refrigerant compressor 1 and the outside air temperature, the fastening portion between the rotation shaft of the outdoor fan motor 11 and the outdoor fan 4 is controlled. In addition, the life of the bearing of the outdoor fan motor 11 is reduced.

Therefore, the rotation speed of the refrigerant compressor 1 is lower than a predetermined rotation speed, and the outside air temperature detector 12
When the outside air temperature detected by is lower than a predetermined temperature,
During the heating operation, when the outside air temperature detected by the outside air temperature detector 12 is higher than the predetermined temperature, the rotation speed of the outdoor fan 4 is set to be lower than the predetermined rotation speed by a certain amount, thereby increasing the reliability. Thus, it becomes possible to carry out the operation of the air conditioner with high efficiency.

In the second embodiment of the air conditioner control method as described above, the number of revolutions of the refrigerant compressor 1 which does not require the capacity of the heat exchanger is the lowest settable number of revolutions. When the outside air temperature detected by the outside air temperature detector 12 is lower than a predetermined temperature during the cooling operation, and when the outside air temperature detected by the outside air temperature detector 12 is higher than the predetermined temperature during the heating operation. By setting the rotation speed of the outdoor fan 4 lower than the predetermined rotation speed by a certain amount, the rotation speed control of the outdoor fan 4 can be simplified as compared with the first embodiment, and the development period can be shortened. It becomes possible.

[0028]

As described above, in the present invention according to the first aspect, as the electric motor for driving the outdoor fan, the electric motor having a variable rotation speed and using a permanent magnet for the rotor is used. By controlling the rotation speed of the outdoor fan according to the rotation speed of the refrigerant compressor and the outside air temperature detected by the outside air temperature detector, when the load on the air conditioner is small, that is, when the rotation speed of the refrigerant compressor is low, the air The power consumption of the harmony device can be reduced and the efficiency can be increased.

In the method according to the second aspect of the present invention, since it is not necessary to frequently control the number of revolutions of the outdoor fan motor, it is possible to improve the reliability and efficiency of the air conditioner. it can.

According to the third aspect of the present invention, the control of the number of revolutions of the outdoor fan can be further simplified, and the development period can be shortened.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a refrigeration cycle of an air conditioner of the present invention.

FIG. 2 is a diagram showing motor efficiency characteristics with respect to the number of rotations of a brushless DC motor and an induction motor.

FIG. 3 is a graph showing motor power consumption characteristics with respect to the number of rotations of a brushless DC motor and an induction motor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Refrigerant compressor 2 ... Four-way valve 3 ... Outdoor heat exchanger 4 ... Outdoor fan 5 ... Outdoor expander 6 ... Liquid receiver 7 ... Indoor expander 8 ... Indoor heat exchanger 9 ... Indoor air blower 10 ... Refrigerant compressor Motor 11 ... Outdoor fan motor 12 ... Outdoor temperature detector 20 ... Outdoor unit 21 ... Indoor unit 30 ... Refrigerator compressor motor controller 31 ... Outdoor fan motor controller

 ──────────────────────────────────────────────────の Continuing from the front page (72) Inventor Kazuki Urata 390 Muramatsu, Shimizu-shi, Shizuoka Pref.Hitachi Air Conditioning Systems Co., Ltd. Shimizu Production Headquarters (72) Inventor Hiroshi Takenaka 390 Muramatsu, Shimizu-shi, Shizuoka Prefecture Hitachi Air Conditioning Systems Co., Ltd. Shimizu Production Headquarters F-term (reference) 3L054 BA03 3L060 AA03 CC03 CC19 DD05 EE06

Claims (3)

[Claims] 1. A refrigerant compressor having at least a variable number of revolutions,
An outdoor heat exchanger having an outdoor air temperature detector and an outdoor fan,
An air conditioner using a refrigeration cycle including an expander and an indoor heat exchanger, and sequentially connecting these devices, wherein the number of rotations is variable as an electric motor for driving the outdoor fan, and a permanent magnet is provided on the rotor. And a control unit that controls the number of revolutions of the outdoor fan according to the number of revolutions of the refrigerant compressor and the outside air temperature detected by the outside air temperature detector using the motor. An air conditioner characterized by that: 2. An air conditioner according to claim 1, wherein:
The rotation speed of the refrigerant compressor is lower than a predetermined rotation speed, and the outside air temperature detected by the outside air temperature detector is lower than a predetermined temperature during the cooling operation or the outside air temperature detector during the heating operation. And controlling the rotation speed of the outdoor fan to be lower than a predetermined rotation speed when the outside air temperature detected by the control is higher than a predetermined temperature. 3. An air conditioner according to claim 1, wherein:
When the rotation speed of the refrigerant compressor is a settable minimum rotation speed, and during the cooling operation, the outside air temperature detected by the outside air temperature detector is lower than a predetermined temperature, or during the heating operation, the outside air temperature is reduced. When the outside air temperature detected by the temperature detector is higher than a predetermined temperature, the rotation speed of the outdoor fan is set lower than the predetermined rotation speed.