JP2924445B2 - Drive unit of compressor for air conditioner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compressor driving device used in a variable capacity air conditioner or the like, and more particularly to a technique for controlling a high pressure of the compressor so as not to exceed an allowable line.

[0002]

2. Description of the Related Art In a compressor driving device in which the number of revolutions of a compressor is variable, if the discharge pressure of the compressor rises abnormally, an indoor unit is overheated or a load exceeding a permissible value is applied to a drive circuit, which causes trouble. Occurs. Therefore, in order to prevent such a situation, the condensing temperature of the compressor discharge gas in the refrigeration cycle is detected using a thermistor or the like, and when the detected temperature becomes equal to or higher than a certain value, the increase in the compressor rotation speed is suppressed. This is known (for example, refer to JP-A-6-140253). Inverter circuits are often used as drive circuits for variable capacity air conditioner compressors, and switching elements such as power transistors used in the circuits are operated within the allowable current range so as not to fail. Need to be On the other hand, in order to increase the comfort of air conditioning, it is necessary to extend the range of operation to the very end of the current allowable range.

[0003]

However, in the method disclosed in the above publication, which detects the condensing temperature in the refrigeration cycle and obtains the high pressure, the detection has a large time delay. It may be higher than the target pressure. For this reason, there has been a problem that the indoor unit is heated, and that a measure such as increasing the capacity of the power transistor is required, resulting in an increase in cost.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems. Instead of detecting the condensing temperature to detect the high pressure of the compressor, the high pressure is determined from the input current and the number of revolutions of the compressor (motor). By calculating and calculating the rotation speed of the compressor so that it does not exceed the allowable line, the rotation speed can be controlled without causing a time delay.Therefore, the operating range can be reduced to just the allowable current range of the control circuit element. An object of the present invention is to provide a drive device of a compressor for an air conditioner, which can be widened, and can improve comfort and reduce costs.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, an air conditioner compressor driving apparatus according to the present invention comprises input current detecting means for detecting an input current of a compressor driving motor, and rotation of the motor. Number of rotations detecting means for detecting the number, storage means for previously obtaining and storing the relationship between the input current and the high pressure with respect to the number of rotations, and the storage means from the input current and the number of rotations detected by each of the detection means described above. Means for determining the high pressure of the compressor by referring to the control means, and control means for controlling the motor speed so that the determined high pressure value does not exceed a preset allowable line. .

[0006]

According to the above construction, based on the input current and the number of revolutions of the compressor drive motor detected by each detection means,
The high pressure of the compressor is obtained by referring to the relationship between the input current and the high pressure with respect to the number of revolutions which is obtained in advance and stored in the storage means. The control means controls the compressor rotational speed without time delay so that the high pressure value obtained as described above does not exceed a preset allowable line. This prevents the discharge pressure of the compressor from becoming larger than the allowable value.

[0007]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an overall configuration of a drive device using an inverter circuit and a brushless DC motor as an embodiment of a drive device for a compressor having a variable rotation speed. In FIG. 1, an AC power supply 1 is connected to a full-wave rectifier circuit 2, and a DC output terminal of the full-wave rectifier circuit 2 is connected to a smoothing capacitor 3, and further connected to an inverter circuit 4. The inverter circuit 4 is, for example, a three-phase bridge connection of six power transistors serving as switching elements, converts a DC voltage into an AC voltage, and converts the frequency and voltage of the AC fundamental wave into arbitrary values by PWM (pulse width modulation). ) Can be controlled. The AC output voltage of the inverter circuit 4 is supplied to a star-connected three-phase stator winding of the brushless DC motor 5. The brushless DC motor 5 includes a stator winding and a permanent magnet type rotor. The brushless DC motor 5 is built in a compressor 6 provided in the refrigeration cycle and drives a compression element 7. The refrigeration cycle includes a heat exchanger 8, a fan 9, a heat exchanger 10, a fan 11, and a capillary tube 1.
2. It is composed of components such as the accumulator 12.

A microcomputer 21 as a control device of the compressor outputs an inverter switching signal of a predetermined voltage and frequency to drive and control a power transistor of the inverter circuit 4. AC current detector (ACCT) 2
2 is provided between the AC power supply 1 and the full-wave rectifier circuit 2, and its detection output is input to the microcomputer 21 via the input current effective value detection circuit 23. Further, the position detection circuit 2
A microcomputer 4 detects a back electromotive force of the motor from a power supply line from the inverter circuit 4 to the brushless DC motor 5 and outputs the detected signal as a rotor position detection (rotation speed) signal.
Enter 1 The microcomputer 21 has a function of calculating the high pressure of the compressor from the input current and the number of revolutions detected as described above, and has allowable line data of the high pressure determined in advance in actual machine verification, The motor speed is controlled so that the calculated value does not exceed the allowable line.

Next, a control procedure by the microcomputer 21 will be described with reference to a flowchart of FIG. The high pressure of the compressor is calculated from the input current and the rotation speed detected as described above (# 1). This calculation may be performed by referring to a table of the high pressure obtained from the input current and the rotation speed as shown in FIG. This table may be obtained in advance by actual device verification and stored in the memory.
Next, it is checked whether or not the high pressure obtained above has exceeded a predetermined drooping line (# 2).
It is reduced at the rate of RPS / sec (# 4). If not, it is checked whether the high pressure has exceeded a predetermined invariable line (# 3). If this is exceeded, a rotation speed increase command by another control is not accepted (# 5), and if not, the rotation speed command is determined by another control (# 6).

As a setting example 1 of the drooping line and the non-changing line, when an operation range equivalent to the conventional one is realized by a small power transistor, each is 23 kgf / cm.
² , 22.5 kgf / cm ² . Further, as a setting example 2, when a large operation range is realized by using a power transistor equivalent to the conventional one, 25 kgf / cm ² ,
It is set to 24.5 kgf / cm ² .

Here, a conventional control procedure will be described with reference to FIG. 4 in order to clarify the characteristics of the control of this embodiment. The condensing temperature is detected by the sensor, and the high pressure is calculated from the detected temperature (# 11). This calculation is performed by referring to a list of high pressures corresponding to the condensation temperature as shown in FIG. This list can be obtained in advance.
Next, it is checked whether or not the high pressure determined above has exceeded a predetermined stop line (# 12). If it has exceeded, the process proceeds to a forced stop abnormality processing routine (# 18). If not, it is checked whether the high pressure has exceeded a predetermined drooping line (# 13).
It is reduced at the rate of sec (# 15). If not, it is checked whether the high pressure has exceeded a predetermined invariable line (# 14). If this is exceeded, a rotational speed increase command by another control is not accepted (# 16), and if not, the rotational speed command is determined by another control (# 17).

Examples of the pressure setting in the conventional processing include a stop line, a drooping line, and a non-change line, which are 25 kgf / cm ² , 23 kgf / cm ² , and 21 kgf, respectively.
/ Cm ² . In the conventional procedure, since the high pressure is determined by detecting the condensation temperature, there is a time delay in the detection,
In some cases, the power transistor is used in a location larger than the steady-state maximum load, and the power transistor receives a large stress.

On the other hand, in the present embodiment, as shown in FIG. 3 of the above embodiment, the relationship between the input current and the number of revolutions and the high pressure is verified in advance on an actual machine, and is provided as a table. Know the high pressure accurately and quickly. For this reason, a drooping line as a boundary for limiting an increase in the compressor rotation speed can be set as a limit. Even in this case, since there is no time delay in the detection of the high pressure, the current does not transiently exceed the allowable current range of the power transistor. Furthermore, in general, the load of the compressor changes according to the refrigerant circulation amount, that is, the compressor rotation speed, and since the allowable high pressure is not uniform over the entire rotation range, control is performed according to the rotation speed. Although it is desirable to perform control by detecting the magnitude of the load from the input current and the number of rotations of the compressor as in the present invention, it is in line with this requirement, Control with a high degree of freedom can be performed accordingly.

[0014]

As described above, according to the present invention, the relationship between the input current and the number of revolutions and the relationship between the high pressure and the previously determined input current and the number of revolutions from the input current and the number of revolutions of the compressor (motor) are accurately and without delay. Estimating the high-pressure and controlling the rotation speed so that the high-pressure does not exceed the predetermined limit, it is possible to extend the operating range to the very limit of the allowable current range of the power transistor, and to provide comfort as an air conditioner. Can be raised. In addition, assuming an operation range equivalent to that of the related art, the capacity of the power transistor can be reduced, and cost can be reduced. Furthermore,
In general, the load of the compressor varies with the amount of circulating refrigerant, that is, the number of rotations of the compressor, and the allowable high pressure is not uniform over the entire rotation range. By controlling the load by detecting the magnitude of the load from the rotation speed, control with a high degree of freedom according to the rotation speed becomes possible.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a driving device of a compressor with variable rotation speed according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a control procedure in the device.

FIG. 3 is a diagram showing a table of a high pressure corresponding to an input current and a rotation speed.

FIG. 4 is a flowchart showing a control procedure in a conventional device.

FIG. 5 is a diagram showing a list of condensation temperature and high pressure in a conventional apparatus.

[Explanation of symbols]

 Reference Signs List 4 inverter circuit 5 brushless DC motor 21 microcomputer (control means) 23 input current effective value detection circuit 24 position detection circuit

Claims (1)

(57) [Claims] 1. An input current detecting means for detecting an input current of a compressor drive motor, a rotational speed detecting means for detecting a rotational speed of the motor, and a relation between the input current and the high pressure with respect to the rotational speed is obtained in advance.
Means for obtaining a high-pressure pressure of the compressor by referring to the storage means from the input current and the number of revolutions detected by each of the above-described detection means; Control means for controlling the motor speed so as not to exceed the allowable line set forth above.