JPS5961488A - Speed controlling method of dc motor - Google Patents

Abstract

PURPOSE:To effectively prevent the variation of the rotating speed of a brushless DC motor by excluding the first rotation detection signal obtained immediately after switching the energization and deenergization from the object of discriminating the conditions of the energization and deenergization. CONSTITUTION:A rotating speed and the phase of a motor M are detected and fed back by a Hall sensor 4 to the speed detector 5. The output signal of the speed detector 5 which receives the reference clock from a reference signal generator 7 is inputted to a drive circuit 6, the phase of the motor M is switched by selecting the drive transistor, the speed signal A from the speed detector 5 is inputted to a pulse inhibit circuit 9, and the timing clock B is inputted to the reference signal generator 7. The ON or OFF signal E of the exciting current is outputted from a comparator 8 which receives the signal D produced by removing the first signal immediately after switching the energization and the deenergization for affecting adverse influence to the speed control of the speed signal A by a pulse inhibit circuit 9 and the reference signal C from a reference signal generator 7 to the drive circuit 6.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to a method for controlling a motor by detecting rotation of a rotor using magnetic means such as a Hall sensor.

(b) Background of the Technology In order to downsize magnetic disk drives, more and more methods are being used to incorporate a motor into the spindle of a magnetic disk drive. Brushless DC motors are suitable for achieving such miniaturization, but as the recording density of magnetic disk drives increases, it is required to control the speed of the spindle motor at a constant level.

Brush type DC motors have high efficiency, but because the brushes are used to commutate the current, they have the disadvantage that, in addition to wear, the noise generated by sparks does not adversely affect peripheral circuits. On the other hand, a DC motor that detects the rotation of the rotor using a Hall sensor to perform phase switching and speed control of the stator can solve the above-mentioned problems of the brush type motor. However, since it is detected magnetically,
There is a possibility that detection errors may occur due to the influence of magnetism generated from the motor coil.

(C1 Prior Art and Its Problems Figure 1 shows a DC motor equipped with a normal Hall sensor. Permanent magnets 2 constituting the rotor are disposed outside the excitation coil 1 of the stator example, and the rotating shaft 3 is the center of the motor.) A Hall sensor 4 is arranged near the permanent magnet 2 so that the magnetism of the permanent magnet 2 can be detected.

Figure 2 is a time chart showing the control method of a DC motor equipped with such a Hall sensor.
Hall output generated every rotation, (b) C 111% clock, (c) drive current supplied to the motor coil,
(d) indicates the rotational speed of the motor.

When the rotation speed of the motor is slow and the reference clock is generated before the output of the Hall sensor, the drive current is turned on by the reference clock, and the rotation speed of the motor gradually increases as shown in (d). When the motor is gradually accelerated and the Hall output of the motor occurs earlier than the reference clock, the drive current is turned off by the Hall output, and the motor is gradually decelerated as shown in (d).

In this way, conventionally, the speed of the motor is controlled and the motor is started and stopped by turning on and off the drive current.

When the ball morph is viewed from the front, it has a configuration as shown in FIG. 3, so if the excitation coil 1 is continuously de-energized, the ball sensor 4 will not receive magnetic noise from the excitation coil 1. Magnetic noise is received from the excitation coil only when the device is switched to the energized state after being in the non-energized state.

Due to the error caused by the noise, it is determined that the rotation has not reached the predetermined speed even though the rotation has actually increased to the predetermined speed, and energization is continued. When the speed is higher than the error component, it is determined that the valve has rotated up to a predetermined speed and is switched to de-energization. Conversely, even after switching from the energized state to the de-energized state, due to the error received from the excitation coil at the end, depending on the direction of the error, the speed may decrease to the specified speed even though it is actually decelerating to the specified speed. It is determined that the
The de-energized state continues. Then, only when the speed has decelerated beyond the error component, it is determined that the speed has been decelerated to a predetermined speed, and the state is switched to the energized state.

In this way, due to the magnetic error received from the excitation coil when switching between energization and de-energization, the switching timing between energization and de-energization is out of order, and rotational fluctuations become large.

(d1 Purpose of the Invention) Therefore, the purpose of the present invention is to solve such problems in DC motors using Hall sensors, and to avoid being affected by detection errors that occur when switching between energization and de-energization. shall be.

(e1 Structure of the invention In order to achieve this object, the present invention detects the rotational position of the rotor once or several times per revolution, and determines energization/de-energization for the next rotation by comparing it with a reference oscillation output. In the method of determining and controlling the rotation speed, there is a method for preventing the first rotation detection signal obtained immediately after switching between energization and de-energization from being input to the energization/de-energization condition discriminator. I'm picking it up.

(f) Embodiments of the Invention Next, how the method for controlling the speed of a DC motor according to the present invention is actually implemented will be explained by way of embodiments. FIG. 4 is a diagram showing a control circuit for a DC motor. M is a DC motor, and a Hall sensor 4 is installed near its rotor.
The phase of the motor is detected magnetically, the rotational speed is detected, and the detected speed is fed back to the speed detection circuit 5. Then, the output signal of the speed detection circuit 5 is inputted to the drive circuit 6 to select a drive transistor, thereby switching the phase of the motor M.

Further, a speed signal A outputted from the speed detection circuit 5 into which the detection signal of the Hall sensor 4 is inputted, and a reference signal C outputted from the reference signal generator 7 are inputted to the comparator 8. However, only the speed signal A that does not include a detection error is input to the comparator 8 via the pulse inhibit circuit 9.

FIG. 6 is a time chart explaining the operation of the control circuit shown in FIG. 4, in which φ is the reference clock output from the reference signal generator 7, A is the speed signal output from the speed detection circuit 5, and B is the reference clock output from the reference signal generator 7.
is the timing clock output from the speed detection circuit 5,
C is a reference signal output from the reference signal ordering device 7, D is a speed signal that does not include detection errors among the speed signals A, and E is an on/off signal of the excitation current input to the drive circuit 6.

Conventionally, the speed signal A is directly input to the comparator 8, and by comparing it with the reference signal C, if the speed signal A is input earlier than the reference signal C, it is determined that the motor speed is too fast, and the next revolution is stopped. The excitation coil is de-energized, and conversely, if the speed signal A is input slower than the reference signal C, it is determined that the motor speed is slow, and the excitation coil is energized for the next rotation. .

In the case of the present invention, instead of directly inputting the speed signal A to the comparator 8, the speed signal is removed by the pulse inhibit circuit 9 without adversely affecting speed control, as shown by D. Only the speed signal that does not contain any error is input to the comparator 8, and is used for determining whether the excitation current is on or off.

FIG. 7 is a circuit diagram showing the configuration of the fifth UIJ hahalus inhibit circuit 9, and FIG. 7 is a time chart 1 showing its inhibit operation. io and it are mono multi circuits, and the on/off signal E output from the comparator 8 is directly input to the upper mono multi circuit 10, but the inverter 12 is input to the lower mono multi circuit 11. A signal obtained by inverting the on/off signal E is inputted through the inverter. Then, the on/off signal E and the inverted signal of the on/off signal E generate an inhibit signal F with a set length in the monomulti circuits 10 and 11, respectively, and pass through the OR circuit 13 and are in an inverted state. Then, it is input to the AND circuit 4 for gate control. The speed signal A is input to the other input terminal of this AND circuit 14, and the mono multi-circuit 10, 1
1 is inhibited by the gate control signal input from 1, as shown in the sixth diagram.

That is, as shown in FIG. 7, when the on/off signal E1 is generated and input to the monomulti circuit 10, an inhibit signal F is generated for a set time t, which is inverted and input to the AND circuit 1.
4 is turned off, the speed signal A cannot pass through the AND circuit 14. The monomulti circuits 10 and 11 are set to be longer than one cycle of timing clock B and shorter than two cycles.

Therefore, the monomulti circuit 1o is triggered.
! First (7) Only the first speed signal A is inhibited. When the inhibit signal is turned off, the AND circuit 14 is turned on with its inverted signal, and the second speed signal A can pass through the AND circuit 14.

After the excitation current is turned off continuously based on the determination that the motor speed is high, when the motor speed is decelerated to the specified speed and the excitation current is turned on, the first speed signal A is inhibited. Excluded from the target of energized/de-energized condition determination. Therefore, a speed signal that includes a noise component that causes a speed error is excluded, and even if it contains an error component, the energization/de-energization condition is determined from the second speed signal in which the error component is regularly generated. Therefore, variations in motor speed due to errors received from the excitation coil are prevented.

In addition, when the on/off signal E turns off after the energization continues, the lower mono multi-circuit 11 is triggered by the signal inverted by the inverter I2 and an inhibit signal F is generated, and the inverted signal l: The circuit 14 is turned off. Therefore, as in the above case, only while the inhibit signal is being generated, the speed signal A cannot pass through the AND circuit 14, and is excluded from the determination of energization/de-energization conditions, and the second and subsequent speeds from the signal to the comparator 8,
It is used to determine whether the power is energized or not. Even if the second and subsequent coils are influenced by magnetism from the excitation coil, the period of the influence is constant and regular, so there is virtually no error in detecting the position of the rotor.

In this way, circuit 1 can be uninhibited without being inhibited.
The second and subsequent speed signals that have passed through the reference signal generator 7 are input to the comparator 8, and compared with the reference signal C input from the reference signal generator 7, and the next energization/de-energization determination is made. Therefore,
Speed fluctuations caused by speed signals containing errors when switching between energization and de-energization are prevented, and the drawbacks of speed control methods using Hall sensors are eliminated.

(Effects of the Invention As described above, according to the present invention, the first rotation detection signal obtained immediately after the switching between energization and de-energization is performed is excluded from the object of determining the energization/de-energization condition. Therefore, when detecting rotation thereafter, the magnetic flux received from the rotor and the magnetic flux received from the excitation coil appear regularly at a certain period, so the Hall sensor is affected by the magnetic flux generated from the excitation coil. This does not cause a change in the switching timing between energization and de-energization of the motor, and fluctuations in the rotational speed of the motor are reliably prevented.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a motor equipped with a Hall sensor, Figure 2 is a time chart showing a conventional DC motor rotation control system, Figure 3 is a front view of a motor equipped with a Hall sensor, and Figures 4 and below are 4 shows a control circuit for a DC motor, FIG. 5 shows an inhibit circuit, and FIG. 6 shows a timing diagram showing the operation of the control circuit. FIG. 7 is a time chart showing the inhibit operation. In the figure, M is a DC motor, 1 is an excitation coil, 2 is a permanent magnet of the rotor, 4 is a Hall sensor, 5 is a speed detection circuit, 6 is a drive circuit, 8 is a comparator, 9 is an inhibit circuit,
10 and 11 are monomulti circuits, and 14 is an AND circuit, respectively.

Claims (1)

[Claims] In the method of controlling the rotation speed by detecting the rotational position of the rotor once or several times per revolution and comparing it with the reference oscillation output to determine whether the next revolution is energized or not, A method for controlling the speed of a DC motor, characterized in that a first rotation detection signal obtained immediately after switching is not input to a energization/de-energization condition determining section.