JPH07104062B2 - Air conditioner - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an air conditioner, and particularly to an air conditioner suitable for a refrigeration cycle having a motor rotation speed variable control function.

[Prior Art] Conventionally, a motor variable control function including a compressor driven by a DC brushless motor using a permanent magnet for a rotor, a condenser, a pressure reducing means, an evaporator, and a refrigerant piping system connecting the same. The air conditioner with (hereinafter referred to as inverter function)
Generally, it has the structure shown in FIG.

FIG. 2 is a refrigeration cycle system diagram of a conventional air conditioner.

In FIG. 2, 1'is a compressor driven by a DC brushless motor using a permanent magnet as a rotor, 2 is a switching valve,
Reference numeral 3 is a condenser, 4 is an expander related to the pressure reducing means, 5 is an evaporator, and 6'is a control unit for performing inverter control.

In the refrigeration cycle shown in FIG. 2, the refrigerant gas discharged from the compressor 1 ′ returns to the compressor 1 ′ after passing through the switching valve 2, the condenser 3, the expansion valve 4, the evaporator 5, and the switching valve 2. It is like this. An air conditioner with an inverter function controls the compressor motor speed according to the size of the load,
They were trying to reduce defrosting time, improve comfort by avoiding intermittent operation, and improve annual energy efficiency.

In addition, as a prior art close to the present invention, for example, Japanese Utility Model Publication 57
In the refrigeration cycle described in JP-A-73563, a gas injection circuit is provided between the compressor and the gas-liquid separator arranged on the downstream side of the condenser, and a part of the refrigerant under compression is compressed by the compressor. Provide a release circuit that can return to the suction side,
It is known that the supply of the liquid refrigerant to the evaporator side is secured when the release circuit is released to prevent the superheat of the evaporator from occurring.

[Problems to be Solved by the Invention] The design of a motor in an air conditioner having a refrigeration cycle shown in FIG. 2 has a maximum capacity required at the time of defrosting or heating at the maximum voltage given from the inverter. It is determined by the torque and the rotational speed that can be obtained.

However, at relatively low heating and cooling rating points, which are used with relatively high frequency, the voltage is chopped by the inverter and the voltage applied to the motor is lowered to use the motor. I was using it and was forced to use it inefficiently.

FIG. 3 is a diagram showing a change in motor efficiency with respect to the rotation speed in a conventional air conditioner.

As shown in FIG. 3, for example, the motor efficiency η ₁ during defrosting operation, which is a light load high-speed operation, or when the heating is started, is different from the motor efficiency η during cooling rated operation, which is a high-load low-speed operation.
_In No. ₂ , the motor efficiency is reduced by Δη, and the value is around 10%.

On the other hand, the refrigerant injection circuit in the refrigeration cycle described in Japanese Utility Model Laid-Open No. 57-73563 prevents a generation of superheat in the evaporator by returning a part of the refrigerant gas under compression to the suction side of the compressor. However, no consideration was given to controlling the rotation speed of the compressor motor to a low speed by injecting the liquid refrigerant into the compressor from the outlet of the condenser to cool the motor.

The present invention has been made in order to solve the above-mentioned problems of the prior art, and when operating the compressor of the refrigeration cycle, it is possible to always operate at a point of good motor efficiency, and it is possible to reduce power consumption. The purpose is to provide a harmony machine.

[Means for Solving Problems] In order to achieve the above-mentioned object, the air conditioner according to the present invention has a compressor, a condenser, which is driven by a DC brushless motor using a permanent magnet as a rotor, In an air conditioner equipped with a pressure reducing means, an evaporator, and a refrigerant piping system connecting these, a liquid introducing pipe for introducing a liquid refrigerant from a condenser outlet and injecting it into a compressor, and a flow rate provided in this liquid introducing pipe. A control valve, a temperature sensor for detecting the compressor temperature, a difference between an indoor temperature and an indoor set temperature, the compressor temperature, and a flow rate control valve for the liquid introduction pipe according to the operation mode of the air conditioner. And control means for controlling.

In addition, the purpose is to reduce the rate at which the motor mark chops the voltage and to enable operation even at low voltage operation at high voltage in order to guide the liquid refrigerant from the condenser outlet to the compressor (in the rotary compressor, In the cylinder part),
This is achieved by cooling the compressor motor and controlling the injection amount of the liquid refrigerant as needed.

[Operation] The concept of developing the above technical means and its operation will be described.

The applied voltage and the rotation speed of the DC brushless motor have a relationship shown in the following expression (1).

Here, N ... Rotational speed, Φ ... Magnetic flux amount, V ... Voltage, I ... Current, R ... Resistance.

On the other hand, when the temperature of the motor decreases, the magnetic flux increases, which is about 0.2% per ⁰ C.

Therefore, during a relatively low speed heating / cooling rated operation, the voltage V is not reduced by the inverter to adjust the rotation speed N to a low speed, but the motor is cooled by liquid refrigerant injection so as to increase the magnetic flux amount Φ. It was thought of.

As a result, the voltage V can be kept high and the rotation speed N can be controlled to a low speed, and the compressor can be operated at the point of high motor efficiency to perform desired heating and cooling operations.

[Embodiment] An embodiment of the present invention will be described below with reference to FIGS. 1, 4 to 6.

FIG. 1 is a refrigeration cycle system diagram of an air conditioner according to an embodiment of the present invention, FIG. 4 is a diagram showing changes in motor efficiency with respect to rotation speed in the air conditioner of FIG. 1, and FIG. FIG. 6 is a flow chart diagram showing the basics of the control system for the air conditioner of FIG. 1, and FIG. 6 is a flow chart diagram showing an example of its control means.

In FIG. 1, the same reference numerals as those in FIG. 2 denote the same parts, and thus the description thereof will be omitted.

1 is a hermetic compressor driven by a DC brushless motor using a permanent magnet for the rotor, 6 is inverter control,
And a control unit relating to a control means for controlling the amount of injected refrigerant according to the control information, which includes, for example, a microcomputer.

7 is a temperature sensor for detecting the casing surface temperature of the hermetic compressor 6, 8 is a liquid introducing thin tube connected to the compressor 1 branched from the pipe on the outlet side of the condenser 3, and 9 is this liquid introducing thin tube. 8 is a flow control valve equipped with the flow control valve 9
Is a solenoid valve with adjustable opening. 10 indicated by a chain line
Is a signal line for controlling the control unit 7, the motor unit of the compressor 1, and the flow control valve 9 to be connected.

As the compressor 1, although not shown here, a general rotary hermetic compressor is adopted.

The rotary hermetic compressor includes a DC brushless motor and a rotary compression mechanism driven by the motor in a hermetic chamber of a casing.

As is generally well known, the rotary compression mechanism portion includes a roller fitted to an eccentric crank portion of a rotary shaft directly connected to a rotor of a motor, a cylinder for housing the roller and the eccentric crank portion, and a cylinder for this cylinder. A vane inserted into a vane groove formed in the above, and upper and lower bearings that close both ends of the cylinder and support the crankshaft, and the vane follows the rotation of the roller and moves inside the cylinder. It is configured to reciprocate to partition the inside of the cylinder into a compression chamber and a suction chamber.

The liquid introducing thin tube 8 is connected to the upper bearing of this compression mechanism section. Although not shown in the drawings, the upper bearing is provided with an opening communicating with the liquid introducing thin tube on the surface facing the cylinder, and the opening and closing are opened and closed as the roller rotates, and the condenser becomes the high pressure side. The liquid refrigerant from the outlet side of 3 is injected into the cylinder by the differential pressure.

Now, in the flow of the refrigerant in the refrigeration cycle in FIG. 1, the refrigerant gas discharged from the compressor 1 passes through the switching valve 2, the condenser 3, the expansion valve 4, the evaporator 5, and the switching valve 2 to cause the compressor to flow. 1
Then, the same cycle is repeated.

The liquid introduction thin tube 8 that guides the liquid refrigerant from the outlet of the condenser 3 allows the refrigerant liquid to be injected into the cylinder portion of the compressor 1 via the flow rate control valve 9 as described above.

Next, control of such an air conditioner will be described.

The control unit 6 using a microcomputer or the like stores a basic control system shown in FIG. 5 and a control procedure as an example shown in FIG. That is, as shown in FIG. 5, the difference between the set indoor temperature and the current indoor temperature detected by a temperature sensor (not shown), and the casing surface temperature of the compressor 1 related to the compressor temperature detected by the temperature sensor 7. A command for opening the flow rate control valve 9 of the liquid introducing thin tube 8 is issued according to information such as the operation mode of the air conditioner and the rotation speed of the compressor motor. The temperature of the compressor motor is lowered by injecting the refrigerant liquid into the cylinder of the compressor 1.

When the operation mode of the air conditioner is the defrosting operation or the heating start-up, it is necessary to complete the defrosting in the shortest possible time or to reach the set temperature quickly. Therefore, in order to operate the compressor motor as fast as possible, the flow rate control valve 9 of the liquid introducing thin tube 8 is closed and the temperature of the motor is raised without injecting the refrigerant liquid into the cylinder of the compressor 1. This is because the permanent magnet of the DC brushless motor has a negative correlation with the magnetic flux amount Φ with respect to the temperature rise, and increases the motor temperature to decrease the magnetic flux amount Φ and increase the rotation speed N.

On the other hand, when the operation mode of the air conditioner is a sufficiently high load at a relatively low speed operation such as a heating operation or a cooling operation, the flow rate control valve 9 of the liquid introducing thin tube 8 is opened to reduce the temperature of the motor, and the compression is performed. The refrigerant liquid is injected into the cylinder of the machine 1. At this time, in order to control the amount of refrigerant liquid injection, the opening degree of the flow rate control valve 9 is controlled by integrating information such as the compressor casing surface temperature by the temperature sensor 7 and the difference between the set temperature and the current temperature.

FIG. 6 shows an example of the control procedure.

The difference (absolute value) ΔT between the indoor set temperature and the indoor current temperature is more than a certain temperature C ₀ (step), and the temperature T ₀ of the casing surface of the compressor 1 detected by the temperature sensor 7 is a temperature C ₁
If it is smaller (step), the control unit 6 commands the signal line 10 to decrease the opening degree of the flow control valve 9, and accordingly the opening degree of the flow control valve decreases, and the result shown in (step) A is The temperature of the magnet rises and the motor speed N
Rises, the air conditioning capacity of the air conditioner increases, and the indoor temperature tries to approach the set temperature.

When the difference (absolute value) ΔT between the indoor set temperature and the indoor current temperature is lower than a certain temperature C and the temperature T ₀ of the casing surface of the compressor 1 detected by the temperature sensor 7 is higher than a certain temperature C ₂ (step), The control unit 6 commands the signal line 10 to increase the opening degree of the flow control valve 9, and accordingly the opening degree of the flow control valve 9 increases (step). As a result shown in B, the temperature of the permanent magnet decreases. , The motor speed N goes down,
The compressor is operated at the point of high motor efficiency.

FIG. 4 shows a change in the motor efficiency curve when the motor temperature T is changed in the present embodiment, and shows its effect in comparison with the diagram of FIG. 3 in the prior art.

During the defrosting operation or the start-up of heating, the refrigerant liquid is not injected into the cylinder of the compressor 1 and the motor temperature is set to a high temperature T ₁ . When the heating is rated, the refrigerant is injected into the cylinder of the compressor 1 to lower the motor temperature to T ₂ . Also, when cooling is rated, the amount of refrigerant liquid injection is increased to lower the motor temperature to T ₃ . As a result, for example, in the case of the cooling rating, the improvement of the motor efficiency due to the injection of the refrigerant liquid is Δη.
_1, there is an effect of reducing correspondingly the power consumption.

According to the present embodiment, in order to inject the liquid refrigerant from the hermetic compressor 1 driven by the DC brushless motor using the permanent magnet as the rotor and the condenser 3 outlet into the cylinder portion of the compressor 1 in the previous period. The liquid introduction thin tube 8 and the flow rate control valve 9 provided in the liquid introduction thin tube 8 are provided, and information such as the casing surface temperature of the compressor 1, the difference between the indoor temperature and the indoor set temperature, the operation mode, etc. is integrated. Since it has a control unit using a microcomputer or the like for controlling the opening degree and opening / closing of the flow control valve 9,
By controlling the refrigerant liquid injection amount, the motor temperature can be lowered, and the motor efficiency can be improved during heating and cooling rated operation, which is relatively slow and frequently used, and has the effect of reducing power consumption.

In addition, during defrosting operation, when heating is started, refrigerant liquid is not injected, and during cooling operation, during heating other than startup, refrigerant liquid is injected. Higher control is performed, and when relatively low speed is sufficient, control is performed to lower the motor temperature, and there is an effect of improving power consumption by improving motor efficiency.

In the above-described embodiment, the compressor is an example of a hermetic rotary compressor, but the present invention is not limited to this, and other types of compressors can be used as long as similar effects are expected. You can use a machine.

[Advantages of the Invention] As described above, according to the present invention, an air conditioner is provided that enables constant operation of a compressor in a refrigeration cycle at a point of good motor efficiency and enables reduction of power consumption. Can be provided.

[Brief description of drawings]

FIG. 1 is a refrigeration cycle system diagram of an air conditioner according to an embodiment of the present invention, FIG. 2 is a refrigeration cycle system diagram of a conventional air conditioner, and FIG. 3 is a rotation in a conventional air conditioner. 4 is a diagram showing a change in motor efficiency with respect to the number of revolutions, FIG. 4 is a diagram showing a change in motor efficiency with respect to the rotational speed in the air conditioner in FIG. 1, and FIG. 5 is a control of the air conditioner in FIG. FIG. 6 is a flowchart showing the basics of the system, and FIG. 6 is a flowchart showing an example of the control procedure. 1 ... Compressor, 3 ... Condenser, 4 ... Expansion valve, 5 ... Evaporator, 6 ... Control unit, 7 ... Temperature sensor, 8 ... Liquid introduction tube, 9 ... Flow control valve, 10 ... signal line.

Claims (2)

[Claims] 1. An air conditioner comprising a compressor driven by a DC brushless motor using a permanent magnet as a rotor, a condenser, a pressure reducing means, an evaporator, and a refrigerant piping system connecting these to each other. A liquid introducing pipe for guiding the liquid refrigerant from the outlet and injecting it into the compressor, a flow control valve provided in the liquid introducing pipe, a temperature sensor for detecting the compressor temperature, and a difference between the indoor temperature and the indoor set temperature. An air conditioner comprising: a control unit configured to control a flow rate control valve of the liquid introduction pipe in accordance with the compressor temperature and an operation mode of the air conditioner. 2. The device according to claim 1, wherein the control means closes the flow rate control valve for introducing the liquid during the defrosting operation and the heating start-up operation, and during the cooling operation and the heating operation other than the start-up. An air conditioner characterized in that a control procedure is stored so that a flow control valve of an introduction pipe is opened and its opening is controlled.