JPH02211264A - Rotary machine - Google Patents

Abstract

PURPOSE:To slow down and stabilize braking characteristics at low speed by providing, as driving sources, a DC brushless motor, a rotation detecting sensor, and a pulse generation sensor. CONSTITUTION:A motor 8 is driven by a power transistor 7. Alternating current from an AC power source 1 is smoothed by means of a diode bridge 2 and a capacitor 5 to provide a DC power source. CPU receives waveform-shaped signals of rotation from a motor IC 16 and delivers instructions for the direction of rotation, normal or reverse, to the motor IC 16. By means of triangular-wave generating circuit 19 and PWM generating circuit 20, signals from CPU 12 in a drive circuit 17 are chopped and electric current flowing to a motor 8 through the power transistor 7 is chopped. Chopping amplitude is delivered from a duty detecting circuit 13 so as to be determined by CPU 12 from the electric current flowing to the motor 8 and acceleration/deceleration of speed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to rotating equipment such as a centrifuge, and more particularly to a speed control device for rotating equipment.

[Conventional technology]

Motors with carbon brushes have the disadvantage of contaminating the clean room with carbon powder and increasing maintenance man-hours due to wear of the carbon brushes.

On the other hand, a DC brushless motor is a so-called brushless motor that does not have a carbon brush.

[Problem to be solved by the invention]

However, when braking a DC brushless motor, if a braking current continues to flow through the motor, there is a problem that the motor reverses after it has stopped, and in order to prevent this, it is necessary to remove the motor excitation immediately before the motor stops. Furthermore, in order to free the excitation, it is desirable to control the speed by gradually slowing it down in a low speed range. In other words, if the speed of the motor is suddenly reduced, when the motor is de-energized, the inertia of the rotor may exceed the stopping point and reverse the rotation. In the case of a separator, the sample will be disturbed.

The present invention has been made in consideration of one or more points,
The purpose of this is to create an improved system that gently stabilizes the braking characteristics of low-speed rotation when the motor decelerates, and eliminates problems caused by the motor reversing when the motor suddenly decelerates and is de-energized. [Means for solving the problem] The purpose is to provide a rotating device which is equipped with a DC brushless motor as a drive source of a rotating body, and which is arranged at an angle of 120 degrees.
This is achieved by providing a rotation detection sensor of 1,000 and a sensor that generates 120 pulses per rotation.

[Effect]

According to the present invention having the above configuration, when braking the motor, from high speed to medium speed, reverse braking is continued to be applied to the motor to rapidly decelerate it, and from medium speed to just before stopping, direct current braking is applied to the motor. In addition, the motor can be stopped by slightly slowing down the deceleration speed using the signal from the sensor that generates 120 pulses and canceling the excitation just before stopping. In this way, the braking characteristics of low-speed rotation when the motor is decelerating can be It can be stabilized.

〔Example〕

Hereinafter, the present invention will be explained based on one embodiment of the drawings. Fig. 1 is a block diagram of a DC brushless motor drive, Fig. 2 is a braking speed characteristic diagram of the motor, and Fig. 3 is a reference numeral in Fig. 2. It is a braking time chart between B and C.

In Fig. 1 showing the drive system of a DC brushless motor,
1 is an AC power supply, 2 is a current transformer, 3 is a diode bridge, 4 is a resistor, 5 is a capacitor, 6 is a resistor, 7 is a power transistor, 8 is a motor, 9 is a sensor (A), 1
0 is the sensor (B).

11 is a current detection circuit, 12 is a CPU, 13 is a duty detection circuit, 14 is a 120 pulse detection circuit, 15 is a magnetic pole detection circuit, 16 is a motor IC, 17 is a drive circuit, 1
8 is a low rotation detection circuit, 19 is a triangular wave generation circuit, and 20 is P
This is a WM generation circuit.

That is, in FIG. 1, motor 8 is driven by power transistor 7. In FIG. The AC power source 1 is smoothed by a diode bridge 2 and a capacitor 5 to create a DC power source. The sensors (A) 9 are position sensors for creating a rotating magnetic field for the motor 8, and three sensors (A) are provided at an angle of 120°. Sensor (B) 10 is mounted on the motor shaft and generates a 120 pulse/REV signal. CPU
The signal from the CPU 12 in the drive circuit 17 is processed by the triangular wave generation circuit 19 and the PWM generation circuit 20, which receive and receive the waveform-shaped rotation signal from the motor IC 16 and issue instructions for forward/reverse rotation to the motor IC 16. The current flowing through the power transistor 7 to the motor 8 is chopped. The chopping width is output from the duty detection circuit 13, and this value is determined by the CPU 1 from the current flowing through the motor 8 and the acceleration/deceleration speed.
2 is decided.

In FIG. 2, which shows the braking speed characteristics of the motor in the rotating equipment of the present invention, in the interval A-8 when the reverse braking starts, reverse braking is continued to be applied with the maximum torque of the motor to rapidly decelerate the rotating equipment connected to the motor. If a centrifuge is used, the time required for sample separation will be shortened. Then, between B and 0, the deceleration speed is made a little slower than between A and 8, and the motor is de-energized at the 0 point and stopped at the 0 point.

In FIG. 3, which shows the braking time between B and C in FIG. The motor is controlled using the
When the sensor B signal rises, it outputs a signal with a pulse width of t time and applies reverse braking to the motor. Even with the next sensor B signal,
A signal with a time pulse width of , the excitation can be canceled at the 0 point and the motor can be stopped slowly and stably.

〔Effect of the invention〕

The present invention is as described above, and as is clear from the explanation of the illustrated embodiments, according to the present invention, the braking characteristics of low-speed rotation during motor deceleration are gradually stabilized, and the motor is rapidly decelerated. When the motor is de-energized, problems caused by the motor reversing, for example, when the rotating device connected to the motor is a centrifugal separator, can be prevented from disturbing the sample.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, in which FIG. 1 is a block diagram of DC brushless motor drive, FIG. 2 is a braking speed characteristic diagram of the motor, and FIG. This is a braking time chart. 1...AC power supply, 8...motor, 9...sensor (
A). 10...Sensor (B), 14...120 pulse detection circuit. Patent applicant name Hitachi Koki Co., Ltd. Me 2 diagram

Claims (1)

[Claims] 1. A rotating device comprising a DC brushless motor as a drive source for a rotating body, three rotation detection sensors arranged at an angle of 120 degrees, and a sensor that generates 120 pulses per revolution.