JPS61269693A - Controller of motor-driven compressor - Google Patents

Abstract

PURPOSE:To raise the substantial efficiency as a compressor by detecting the load torque of a motor-driven compressor, and controlling the voltage applied to the motor in response to the detected torque, thereby always enabling the high efficiency operation of the motor in response to the load. CONSTITUTION:The position of a piston 9 with respect to a cylinder 4 is detected by a position detector 15, a controller 16 feeds a voltage control signal in response to the detected position to a voltage controller 14, which applies a voltage in response to the position of the piston 9 to a motor 2. Accordingly, the substantial efficiency can be raised by suitably and optimally controlling the voltage supplied to the motor in response to the pulsating torque per one revolution of a crankshaft.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device for controlling a compressor whose piston is driven by a crankshaft coupled to an electric motor.

[Conventional technology]

Figures 6 and 1 are 1, for example, Mitsubishi Electric Technical Report Vol. 51, No. 5,
(Showa 58-5-25) rRotary compressor for low temperature P L
(Z) type J P, 9 (343), a diagram showing the conventional electric compressor control device shown in Figure 2, Figure 6 is the overall configuration diagram, and Figure 1 is the compression diagram of the rotary compressor. FIG. 2 is a schematic configuration diagram of elements.

In the figure, (1) is a power source, (2) is an electric motor connected to the power source (1), (3) is a compression element driven by the electric motor (2),
(4) is the cylinder, (5) is the suction hole that opens into the cylinder (4) and sucks in the refrigerant gas, (6) is the discharge hole that also discharges the refrigerant gas, (7) is the shaft of the electric motor (2), ( 8) is a crankshaft that is eccentrically fixed to the motor shaft (7), (9) is a piston that is loosely fitted to the crankshaft (8) and rolls on the inner surface of the cylinder (4), and a fled is attached to the outer peripheral surface of the piston (9). A conventional electric compressor control device is configured as described above,
When the electric motor (2) is driven and the crankshaft (8) rotates eccentrically in the direction of arrow A, the piston (9) and cylinder (4)
According to the movement of the point of contact with the inner surface, suction of refrigerant gas from the suction hole (5) into the cylinder (4), compression of the refrigerant gas, and discharge to the discharge hole (6) are simultaneously performed.

High-pressure refrigerant gas discharged from the discharge hole (6) is guided to a refrigeration cycle (not shown).

In a rotary compressor that operates like this.

The compression torque per rotation of the crankshaft (8) becomes a pulsating torque as shown in FIG. Figure 8 shows the crankshaft (
8) and the cylinder (4) is a characteristic diagram showing the change in torque with respect to the rotation angle in the direction of the arrow, with zero being zero when the contact point between the vane CIQ and the cylinder (4) is at the position of the vane CIQ.

[Problem that the invention seeks to solve]

In the conventional electric compressor control device as described above.

As shown in FIG. 8, it has a pulsating torque that changes every rotation of the rank shaft (8). On the other hand, an induction motor is generally used as the electric motor (2) that is the drive source.

Its slip vs. torque characteristic is shown by curve a2 in FIG.

The slip vs. efficiency characteristic is also shown by curve α3. If the pulsating torque in Fig. 8 corresponds to the slip vs. torque characteristic curve Qa in Fig. 9, it will be operated in the torque range from point aI to point b1, and the motor efficiency will also be 0 on the slip vs. efficiency characteristic curve. It will fluctuate from the 82 points above to the b2 points. Generally, for a pulsating load as shown in Figure 8, the electric motor is designed to have maximum efficiency at the average torque T1, so the actual efficiency decreases as the torque pulsates, reducing the performance of the compressor. There is a problem of lowering the

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a control device for an electric compressor that enables highly efficient operation even under pulsating load torque.

[Means for solving problems]

A control device for an electric compressor according to the present invention is provided with a torque detection means for detecting the torque of a crankshaft, and a control circuit for controlling a voltage control element connected to an electric motor according to the output of this detection means. It is.

[Effect]

In this invention, the voltage supplied to the electric motor is controlled according to the pulsating torque per rotation of the crankshaft, and the electric motor is driven at an optimal voltage according to the load.

〔Example〕

FIG. 1 is an overall configuration diagram showing an embodiment of the present invention.
) to (31 are similar to those of the conventional device described above).

Note that FIG. 1 can be used as is.

In the figure, (I4 is a voltage control element such as a thyristor inserted between the power supply tl) and the electric motor (2), and αS is a position detection means for detecting the position of the piston (9) relative to the cylinder (4) as a load torque detection means. , tte is position detector α9
This is a control circuit that issues a voltage control signal to the voltage control element a4 in accordance with the output signal of the voltage control element a4.

In the electric compressor control device configured as described above, the position of the piston (9) with respect to the cylinder (41) is detected by the two-position detector Q5, and the control circuit r1e outputs a voltage control signal in accordance with this. The voltage control element α4 applies a voltage to the electric motor (2) according to the position of the piston (9).

As is well known, the torque vs. efficiency characteristic of the electric motor (2) is as shown in FIG. 2 when the power supply voltages v1 to v3 are used as parameters. Here, 71)I2)73. Further, the relationship between the load torque and the voltage showing the maximum efficiency for each load torque is uniquely determined as shown in FIG. Therefore, with respect to pulsating torque as shown in FIG. 8, an increase in the actual efficiency can be expected by appropriately controlling the voltage appropriately according to the load.

FIG. 4 is an overall configuration diagram showing another embodiment of the present invention, in which a bidirectional thyristor αη is used as the voltage control element, a trigger generation circuit is used as the control circuit, and the output from the two-position detector α is used. Depending on the signal, a trigger signal is generated from the trigger generation circuit αS, the bidirectional thyristor aD is controlled, and the voltage applied to the electric motor (2) is controlled.

FIG. 5 is also an overall configuration diagram showing another embodiment of the present invention, in which a pressure detector cL flaw for detecting the discharge pressure of the compressor is used as the load torque detecting means.

In other words, the change in load per revolution of the crankshaft (8) is captured as a change in discharge pressure, and the discharge pressure is detected by a pressure detector (19), and a voltage control signal is sent from the control circuit (2) according to its output. is applied to the voltage control element I, and has the same effect as the previously described embodiment.

Although each of the above embodiments describes a rotary electric compressor having a 9-rotation piston, even a reciprocating electric compressor in which the piston reciprocates has a torque load that pulsates in accordance with the rotation of the crankshaft. 0 [Effects of the Invention] As explained above, in this invention, the load torque applied to the crankshaft connected to the piston of the electric compressor is detected, and the electric motor is adjusted accordingly. Since the applied voltage is controlled, it is possible to always operate the electric motor with high efficiency according to the load, and there is an effect that the actual efficiency of the compressor can be increased.

[Brief explanation of drawings]

Fig. 1 is an overall configuration diagram showing an embodiment of an electric compressor control device according to the present invention, Fig. 2 is a torque versus efficiency characteristic curve of an induction motor, and Fig. 3 is a voltage characteristic showing torque versus maximum efficiency. The curve diagram, FIGS. 4 and 5 are overall configuration diagrams showing other embodiments of the present invention, FIG. 6 is an overall configuration diagram showing a conventional electric compressor control device, and FIG. A schematic configuration diagram of the compression element, FIG. 8 is a piston rotation angle vs. torque characteristic curve, and FIG. 9 is an induction motor slip vs. torque/efficiency characteristic curve. In the figure, (2) is the electric motor, (3) is the compression element, (8) is the crankshaft, (9) is the piston, (I4 is the voltage control element,
I5 is a torque detection means (position detector), aS is a control circuit, α is a voltage control element (bidirectional thyristor), α・
is the control circuit (trigger generation circuit), and the cod is the torque detection means (
(pressure detector), - is a control circuit 〇The same symbols in the two figures indicate the same parts. 1st m 2nd lightning Figure 4 lcf

Claims (5)

[Claims] (1) An electric motor that drives a crankshaft coupled to a piston, a voltage control element that is connected to this electric motor and controls the voltage applied to the electric motor, a torque detection means that detects a load torque applied to the crankshaft, and this torque detection A control device for an electric compressor, comprising a control circuit that controls the voltage control element according to the output of the means. (2) The electric compressor control device according to claim 1, wherein the torque detection means is a position detector that detects the position of the piston. (3) The control device for an electric compressor according to claim 1, wherein the torque detection means is a pressure detector that detects discharge pressure. (4) A control device for an electric compressor according to any one of claims 1, 2, and 3, wherein the piston is a rotary piston. (5) A control device for an electric compressor according to any one of claims 1, 2, and 3, wherein the piston is a reciprocating piston.