JPS61203886A - Motor control circuit - Google Patents

Abstract

PURPOSE:To suppress the rise of a motor rotating speed by generatively breaking when the motor rotating speed abnormally rises. CONSTITUTION:When a start switch 6 is closed, flip-flops FF1, FF2 are set in a controller 5. Thus, relays Ry1, Ry2 are energized, and a motor 1 starts rotating with full power. When the motor rotating speed R rises to become R>=R2, the FF2 is reset to deenergize the relay Ry2. Accordingly, the motor 1 is energized through a power down resistor 2. When the speed R further rises to become R>=R3, the FF1, FF2 are both reset to deenergize the relays Ry1, Ry2. Accordingly, the motor 1 is generatively braked through the power down resistor.

Description

[Detailed Description of the Invention] [Summary of the Invention] The present invention provides a speed control circuit that maintains the rotational speed of a DC motor at a desired value by switching the magnitude of current flowing through the motor. For the purpose of responsive control, dynamic braking is used as a deceleration means in addition to switching the applied current.

[Industrial application field]

The present invention relates to a motor control circuit that controls the current flowing through a DC motor to control its rotational speed to a predetermined value.

[Conventional technology]

As a device of this kind, one is known in which a current limiting resistor is selectively interposed in a motor current supply circuit to adjust the motor output.

[Problem that the invention seeks to solve]

However, the conventional device has a problem in that when the motor load is considerably reduced for some reason, the motor rotational speed becomes abnormally high or takes a long time to decrease even if the applied current is restricted.

An object of the present invention is to solve this problem and control the motor rotational speed within a predetermined range with a simple configuration while suppressing abnormal increases in the rotational speed.

[Means for solving problems]

Therefore, the present invention, as described in the claims,
A first relay is provided in the energizing circuit of the DC motor to enable selective power generation operation, a second relay switches the magnitude of the energizing current, and the first relay is configured to switch between the magnitudes of the energizing current and the second relay. The second relay was configured to be controlled according to the detected value of the motor rotation speed.

[Effect]

With this configuration, when the motor rotational speed abnormally increases, the first relay works to perform dynamic braking, effectively suppressing the increase in motor rotational speed, and switching the energizing current and the dynamic braking action. In combination with this action, the motor rotational speed can be maintained within a predetermined speed range.

〔Example〕

FIG. 1 shows an embodiment of the present invention, in which relay RY1 switches between energizing and stopping the motor (dynamic braking). Relay Ry2 short-circuits power down resistor 2 to increase the motor output when the motor rotation speed becomes low. The motor rotation speed is detected by a motor rotation detection device 3 (composed of a magnet directly connected to the motor shaft and a reed switch), and feedback control is performed using relays Ryl and Ry2 via a rotation detection circuit 4 and a control circuit 5. be done. With the above configuration, when the start switch 6 is turned on, the rotational speed of the motor 1 can be controlled to a constant range (R1<R3).

FIG. 2 is a time chart showing the operation of this device, and FIG. 3 is an example of the rotation comparator circuit 4 shown in FIG. It is composed of comparators 7 to 10, and outputs are prepared that are classified into four layers depending on the magnitude of the input frequency R (rotational speed).

Now, by turning on the start switch 6, the flip-flops FF1. The reset of FF2 is released. At this point, motor l has stopped (
Since motor rotation speed R=0), R≦R2,8 of comparator circuit 4
Both outputs of 521 become "1" and FFI and FF2 are set. Therefore, relays R71 and Ry2 are energized and motor 1 starts rotating at full power. Motor rotation speed R
increases and enters the region R≧R2 (region ■ in Figure 2), the R≧R2 output of the rotation detection circuit becomes °1゛, and F
Since F2 is reset and deenergizes relay Ry2, motor 1 is powered through power down resistor 2 and the motor power is reduced.

Region (2) shows a case where the motor load is light, and shows a case where the motor rotational speed R further increases to a state where R≧R3. In this state, R≧R3 of the comparator circuit,
Since both R≧R2 outputs become “lo,” both FFI and FF2 are reset, relays Ryl and Ry2 are deenergized, and motor 1 enters the dynamic braking state via the power-down resistor. Therefore, the motor rotation speed R decreases. When the state of R≦R2 begins, the R≦R2 output of the rotation detection circuit becomes “1”, FFI is set, and Ryl is energized, so that the motor is again supplied with power via the power-down resistor.

Region (2) indicates a case where the motor load is heavy, and the motor rotation speed R is reduced at a motor output such that the motor is supplied with power through a power-down resistor.

Since the motor rotational speed R decreases and R≦R1, both outputs of the comparator circuit, R≦R2 and R≦R1, become “1” and FFI,
Since both FF2 are turned on, relay Ry2 is also energized, and the motor outputs full power to short-circuit the power-down resistor. The motor rotation speed R increases,
When R≧R2, the output of R≧R2 of the comparison circuit becomes 1, so FF2 is reset and Ry2 is deactivated.

As mentioned above, by reducing the influence of light and heavy motor loads,
The motor rotation speed can be controlled to a constant range (R1≦R≦R2).

Note that the present invention may be used as a motor rotation detection device to detect motor rotation by an indirect method, such as by detecting the air volume of a blower motor when applied to an air conditioner, instead of directly detecting motor rotation. .

[Brief explanation of the drawing]

Fig. 1 is an electrical wiring diagram showing one embodiment of the present invention, Fig. 2 is a time chart for explaining the operation of the device shown in Fig. 1, and Fig. 3 is an electrical wiring diagram showing an example of the configuration of the comparison circuit shown in Fig. 1. It is. 1...Motor, 2...Power down resistor, 3...
Rotation speed detection device, 4... Comparison circuit, 5... Control circuit, Ryl, Ry2... Relay. Representative Patent Attorney Takashi Okabe 1 Figure 2 Figure 3

Claims (1)

[Scope of Claims] A first relay provided in the energization circuit of the DC motor to switch between energization drive and power generation control; a second relay provided in the energization circuit of the DC motor to switch the magnitude of the energization current; Signal generating means for generating a speed signal according to the rotational speed of the DC motor; Comparison means for comparing the speed signal with both reference values corresponding to a preset first speed and a second speed greater than the first speed;
and according to the comparison result, when the speed signal does not meet the reference value corresponding to the first speed, the first relay is energized and driven and the second relay is energized with a large current; When the speed signal exceeds a reference value corresponding to the second speed, the first relay is activated for dynamic braking, and when the speed signal is between the reference values corresponding to the first and second speeds, the first relay is energized. A motor control circuit comprising: control means for driving the first and second relays so that the second relay is in a low current state.