JPS63171185A - Drive circuit for brushless motor - Google Patents

Abstract

PURPOSE:To stop a motor quickly, by adding a signal system braking circuit to the drive circuit of the brushless motor. CONSTITUTION:The position of the rotor of a motor is detected by position detection elements (Hall elements) 2 with bias current applied by a resistor 1, and by a change-over circuit 3, a power circuit 4 is turned ON/OFF, and current is permitted to flow to a motor coil 5, and the motor is rotated. So far as a current limiting circuit 9 is concerned, the current of the coil 5 is detected by a current detection resistance 10, and the current flowing to the coil 5 and the power circuit 4 at the time of starting or the like is limited. Then, by a control circuit 7, the power circuit 4 is turned ON/OFF so that the rotational frequency of the motor may coincide with previously set rotational frequency. Besides, a braking circuit 8 is set, and when the input of working signal to the circuit 8 is provided, then the rotational frequency is limited to a previously set limit value, and the output of motor reverse-rotation signal is directed to the change-over circuit 3, and the motor is quickly decelerated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a drive circuit for a brushless motor, and particularly to a brake circuit for a brushless motor suitable for a paper feeding system of a copying machine or the like.

[Conventional technology]

Conventionally, brushless motors are braked using a mechanical braking method in which the rotor of the motor or part of the drive system is held down with a friction piece, or a dynamic braking method in which a switch element and a resistor are connected to the armature coil of the motor. It was being done.

[Problem that the invention seeks to solve]

In the case of mechanical braking, there is a problem that the friction pieces wear out, and this wear causes the braking force to change over time.Structurally, it requires a brake and a device that turns on and off the brake in addition to the motor. This meant that it was necessary, complicated and expensive.

In addition, in the case of dynamic braking, an external power switching element is used to short-circuit the armature coil.

Current limiting resistors, etc. are required, making the circuit complex and expensive.

An object of the present invention is to provide a brushless motor drive circuit that starts operation in response to an operation signal, stops operation in response to an operation stop signal, and switches rotation direction in response to a reverse rotation signal. The purpose of this invention is to realize a brake circuit with a simple configuration by adding a signal brake circuit to the drive circuit.

[Means for solving problems]

The above problem is solved by providing a brake circuit that controls the drive circuit in response to the motor operation stop signal, and the brake circuit transmits the operation stop signal to the drive circuit in response to input of the motor operation stop signal. simultaneously outputs a motor reverse rotation signal, and following the output, outputs a signal for releasing the suspension of the operation stop signal in response to input of a deceleration rotation signal indicating that the motor rotation speed has been decelerated to a predetermined value. Solved by outputting.

[Effect]

When an operation stop signal is input, the brake circuit suspends the operation stop signal, keeps the drive circuit in the operating state, and outputs a reverse rotation signal to the drive circuit, which applies torque in the opposite direction to the rotation direction of the motor rotor. The rotor of the added motor is rapidly decelerated, and when the speed of the rotor is reduced to a certain value, the operation of the motor drive circuit is stopped and the rotation of the motor is rapidly stopped.

〔Example〕

An embodiment of the present invention will be described with reference to FIGS. 1 and 2.

In FIG. 1, the position of the rotor of the motor is determined by a position sensing element to which a bias current is applied by a resistor 1, e.g.
The rotational position is detected by the Hall element 2. In response to the rotational position detection signal, the switching circuit 3 turns the power circuit 4 on and off so that the rotation of the motor coil 5 continues smoothly, causing current to flow and rotating the motor. This is the configuration of a common brushless motor, and detailed explanation will be omitted.

The current limiting circuit 9 detects the current flowing through the motor coil using the current detection resistor 10, and limits the current flowing through the motor coil and the power circuit 4 when starting the motor. The control circuit 7 detects the rotational speed of the motor and turns the power circuit 4 off so that the motor rotational speed matches a predetermined rotational speed. The control circuit 7 operates the power circuit 4 normally when the operation signal is input, and turns off the power circuit 4 in response to the operation stop signal to stop the motor. With this configuration, the power i circuit 4 is simply turned off when the operation stop signal is received, and the motor naturally decelerates. Switching circuit 3. Power circuit 4 , control circuit 7 , and current limiting circuit 9 constitute drive circuit 11 .

Next, the operation of the brake circuit 8 of the present invention will be explained in detail with reference to FIG.

When the actuation signal is input to the brake circuit 8, the actuation signal is output from the brake circuit 8 to the control circuit 7, and the motor starts rotating. At this time, the starting current is limited to a predetermined limit value Ts by the current limiting circuit 9. Next, when the operation stop signal is input to the brake circuit 8, the brake circuit 8 suspends this operation stop signal and does not output it, allowing the drive circuit 11 to continue operating and transmitting the motor reverse rotation signal to the switching circuit 3. Since the reverse rotation signal is output, a voltage opposite to that before the output of the reverse rotation signal is applied to the motor, and the motor suddenly decelerates.

At this time, a voltage that is the sum of the voltage of the power supply 6 and the back electromotive force of the motor itself is applied to the motor coil 5.
If the current is not limited by the current limiting circuit 9, the current will be larger than the current at startup. In this case, the deceleration torque of the motor is the sum of the torque produced by the motor itself and the torque of the load, so the torque that the motor itself should produce changes depending on the magnitude of the load torque. Therefore, the motor current limit value In during deceleration is set in advance so that the motor coil current flows in accordance with the required deceleration torque. During this period, the current limit value is switched to IB. Then, when the motor rotation decelerates and reaches the preset rotation speed Nn, the suspension of the operation stop signal is released and an operation stop signal is output, and at the same time, a release signal of the reverse rotation signal is output and the state is ready for restart. do. Here, the values of Nn and In are set depending on the required deceleration time, that is, the torque that the motor should output and the magnitude of the load 1 - luke.

In the present invention, the only part added to the brushless motor circuit is the brake circuit 8.

The present invention can be used, for example, in a paper feeding system of a copying machine, and when a paper jam occurs, it can suddenly stop, reduce paper jamming, etc., and quickly remove paper.

〔Effect of the invention〕

According to the present invention, by adding a brake circuit to the drive circuit of a brushless motor, reverse-phase braking is performed at the time of stopping, and the motor can be stopped quickly. Furthermore, it has the advantage of being simpler in structure, smaller, and cheaper than mechanical brakes or dynamic braking.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention in which a brake circuit is added to a brushless motor drive circuit.
The figure is a sequence diagram of FIG. Next figure 7

Claims (1)

[Claims] 1. Driving a brushless motor that starts operation in response to a motor operation signal, stops operation in response to a motor operation stop signal, and switches rotation direction in response to a motor reverse rotation signal. The circuit includes a brake circuit that controls the drive circuit in response to the motor operation stop signal, and the brake circuit suspends the operation stop signal in response to input of the motor operation stop signal to the drive circuit. At the same time, it outputs a motor reverse rotation signal, and following this output, in response to the input of a rotation speed signal indicating that the motor rotation speed has decelerated to a predetermined value, outputs a signal that releases the suspension of the operation stop signal. A brushless motor drive circuit characterized by: 2. The drive circuit according to claim 1, wherein the drive circuit outputs a signal to release the motor reverse rotation signal at the same time as outputting a signal to release the suspension of the operation stop signal. 3. Provided in the drive circuit of the brushless motor,
The current limiting value of the current limiting circuit that limits the transient current of the drive circuit and the motor armature coil is set to a different value when the motor starts operating and when the brake circuit is operating. The drive circuit according to item 1 or 2.