JPH0847282A - Brushless motor - Google Patents

Abstract

PURPOSE:To reduce the acceleration/deceleration time of a brushless motor. CONSTITUTION:The title motor consists of a conduction means 7 for achieving conduction between the middle point of an armature coil 5 and a drive power supply 6, a speed detection means 9 for detecting the rotary speed of a rotor, an armature voltage detection means 10 for detecting each terminal voltage of the armature coil 5 and outputting the detection voltage, and a conduction control means 8 for controlling the conduction means 7 according to the output of the armature voltage detection means 10 and the speed detection means 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless motor, and more particularly to a brushless motor that reduces power consumption while reducing acceleration / deceleration time of rotation speed.

[0002]

2. Description of the Related Art In recent years, there has been a strong demand for a reduction in the time required for reading discontinuous and arbitrary data recorded on a disk-shaped recording medium in response to the speeding up of information. The challenge is to shorten the acceleration / deceleration of the rotational speed of the driving motor.

FIG. 6 shows a conventional brushless motor drive controller for driving a disk-shaped recording medium. When the drive power source 6 is turned on, the brushless motor 11 is driven.
Detects the magnetic pole position of the rotor 2 provided with a permanent magnet by the rotor position detecting means 3 such as a Hall element, and switches the current flowing through the armature coil 5 which is the stator by the electronic commutator means 4 according to the detection signal. Is configured as
The rotor 2 generates a rotational driving force according to the known rotation principle of a brushless motor.

FIG. 7 shows torque rotation speed and current characteristics when such a brushless motor is used as a spindle motor for rotating a CD-ROM disk in the specified rotation speed range (1200 to 2400 rpm). Since the DC motor generates a back electromotive force in the armature in proportion to its rotation speed, the upper limit of the armature current decreases as the rotation speed increases, and the torque generated by the motor also decreases. The no-load rotation speed of the motor is the upper limit rotation speed 2400
Must be set high for rpm.

Further, the torque constant of the motor has a relationship that it is small when the unloaded rotation speed is high and is large when the unloaded rotation speed is low. Since the consumption current increases when the unload rotation speed is increased, this limits the upper limit of the torque. I will end up. Since the CD-ROM disc needs to have a constant linear velocity (CLV), it is necessary to control the rotational velocity so as to be inversely proportional to the distance from the rotational center of the track for reading data on the disc.

For example, when reading the data on the inner circumference of the disk, it is necessary to rotate at a speed of about 2400 rpm, and when reading the data on the outer circumference, it is necessary to rotate at about 1200 rpm. This is because when reading continuous data, it is sufficient to gradually change the position of the read track, and the change in rotation speed may be slow, but the pickup accesses the disc to search for any data that is discontinuous. In such a case, since the position of the read track becomes random, the rotational speed of the motor needs to be actively accelerated and decelerated. Therefore, in consideration of such a usage state, conventionally, the no-load rotation speed has been set to about 3600 rpm, which has a margin from the usage rotation range.

[0007]

FIG. 8 shows a spindle motor as the brushless motor, a CD-ROM is read in accordance with a predetermined program, and a change in track position is performed while changing a rotational speed and a current. In the drawing, the data read position changes to the inner and outer circumferences, centering on a speed of about 1800 rpm. on the other hand,
It can be confirmed that the current flows little when the motor speed is constant and flows a lot when the speed changes. There are small changes and large changes in the data read position, but there are many small changes or constant speed ratios as a time ratio, and the average current consumption is almost equal to the current during this small change. Become. However, the armature current does not flow sufficiently due to the back electromotive force in the high rotation speed range, and the generated torque of the motor is not large, so that there is a disadvantage that it takes time when the read track position changes significantly.

Since the acceleration / deceleration time of the rotation speed of the motor is inversely proportional to the torque, it is effective to increase the torque. However, if the torque constant is increased, the no-load rotation speed decreases and the required rotation speed is rather insufficient. The opposite effect,
It is necessary to increase the armature current while increasing the torque while lowering the torque constant. However, if the armature current is increased, the efficiency is deteriorated and the heat generation of the motor is increased, and in the worst case, the disk is heated and permanently deformed.

[0009]

The present invention has been made in view of the above problems, and is a multi-phase star which is energized and driven via a rotor having a permanent magnet and an electronic commutator means connected to a driving power source. In a brushless motor including a stator having a connected armature coil, an energizing unit that enables energization between the driving point and the midpoint of the star-connected armature coil, and the rotation speed of the rotor is detected. Speed detecting means, and armature voltage detecting means for detecting each terminal voltage of the armature coil and outputting the detected voltage,
A brushless motor comprising: an energization control unit that controls the energization unit according to an output of the armature voltage detection unit and an output of the speed detection unit.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the brushless motor according to the present invention will be described in detail below with reference to FIGS. still,
For convenience of explanation, the same components as those shown above are designated by the same reference numerals.

FIG. 1 is a block diagram of a brushless motor according to the present invention, and FIG. 2 is a circuit diagram of the present invention. The midpoint of an armature coil 5 which is a stator in a polyphase star connection is as shown in FIG. It is connected to one end of the power source 6 of Vcc12V via the energizing means 7 composed of the transistor Q31 and the resistor R33, and energized by the energization control signal output by the energization control means 8 composed of the resistor R38 and the transistor Q38. De-energization is controlled. Therefore, in the non-energized state, the middle point of the armature coil 5 is electrically floated, and the full-wave drive operation of the brushless motor is performed. Further, in the energized state, the middle point of the armature coil 5 is electrically driven by the driving power source 6
Is connected to one end of the brushless motor to perform half-wave drive operation of the brushless motor. The rotor position detecting means 3 in FIG. 2 includes three Hall elements H for detecting the magnetic pole position of the rotor 2.
The electronic commutator means 4 is composed of G1, HG2 and HG3.
Is connected to the driving power source 6 via.

That is, the outputs of the Hall elements HG1, HG2 and HG3 biased by the resistors R1 and R2 are Q1 to Q6.
The differential amplifier configured as described above appropriately amplifies and outputs appear at the collectors of the respective transistors. These are Q7 to Q9
In the three-input differential amplifier configured as described above, the current supplied from the transistor Q20 is distributed to the collector of the transistor in accordance with the base potential of each and output. Qualitatively, the transistor Q is connected to the collector of the transistor with the highest base potential.
Since a current of 20 is output and no current is output to the collectors of the other transistors, the height of the voltage changes sequentially with the rotation of the rotor 2, and accordingly, the transistors in which the collector current appears also switch sequentially.

For example, when the base potential of the transistor Q7 is higher than that of the transistors Q8 and Q9, most of the collector current of the transistor Q20 is the transistor Q7.
Is output to the collector of the power transistor Q21 and is inverted by the current mirror circuit composed of the transistors Q21 and Q22, and a current flows into the base of the power transistor Q16 to make it conductive. When the power transistor Q16 becomes conductive, the armature coil 5 connected to it is driven. Similarly, when the base potential of the transistor Q8 is high, the power transistor Q17 becomes conductive, and when the base potential of the transistor Q9 is high, the power transistor Q18 becomes conductive and the armature coils 5 connected to them are driven. It

Further, the transistors Q10 to Q12 are also different from each other.
It constitutes an input differential amplifier. When the base voltage of the transistor Q10 is high, the power transistor Q13 is conductive, and when the base potential of the transistor Q11 is high, the power transistor Q14 is conductive, and the base potential of the transistor Q12 is high. In this case, the power transistor Q15 becomes conductive and the armature coils 5 connected to each are driven. By arranging the Hall elements so that these are sequentially switched at an electrical angle of 120 degrees, the armature coil 5 generates a rotating magnetic field as the rotor 2 rotates, and the rotor 2 is continuously driven to rotate. For example, when the transistors Q13 and Q11 are simultaneously turned on, two of the armature coils 5 are connected in series to form a current path, and a current flows from the collector of the transistor Q13 to the first armature coil via the midpoint. Then, a current flows through the second armature coil and flows into the collector of the transistor Q17. Similarly, six current paths are sequentially formed, but the two coils always flow current in series via the midpoint.

Here, the former state in which the middle point of the armature coil 5 floats is called the high efficiency mode, and the latter state in which the middle point of the armature coil 5 is connected to the drive power source 6 is called the high torque mode. This point will be specifically described below.

In the high efficiency mode, since the two phases of the armature coil 5 are always connected in series and the armature current flows, the torque generated by the same current is two coils and relatively large, but the armature resistance increases. And the back electromotive force also becomes two coils, and the no-load rotation speed becomes low as described above. In this embodiment, by selecting the wire diameter and the number of windings of the armature coil 5 so as to be about 2800 rpm, which is slightly higher than the rotation range used. It is set, and the power consumption is kept low.

In the high torque mode, since the armature current flows through the armature coil 5 in only one phase, the torque generated by the same current is one coil, and therefore the torque is relatively small. It becomes 1/2. But,
The armature resistance and the back electromotive force are also equivalent to one coil, the unloaded rotation speed is roughly doubled to about 5000 rpm, and the torque in the rotation range used becomes large as shown in FIG.

The motor speed detecting means 9 is 2000
When the rotation speed is equal to or higher than rpm, a high rotation mode signal is output to the energization control means 8. As shown in FIG. 2, the speed detecting means 9 is a frequency generator that outputs an FG signal having a frequency proportional to the rotation speed of the motor, a frequency voltage converting means that converts the voltage into a voltage proportional to the frequency, and a frequency voltage converting means. It is composed of a voltage comparator that compares the output voltage with a set voltage, and the set voltage is approximately 2000 rp.
It is selected to be approximately equal to the output voltage of the frequency-voltage converting means corresponding to the rotation speed of m.

As shown in FIG. 2, the armature voltage detecting means 10 is composed of, for example, diodes Q32, Q33, Q34, transistors Q35, Q36, Q37 and resistors R31, R32, R34 to R37. The lowest voltage having the smallest voltage difference between each coil terminal and the ground wire is detected and output to the energization control means 8. That is, if the minimum voltage is higher than the voltage set by R32, R34, the transistors Q35, Q36, Q
37 conducts and acts to lower the base voltage of the transistor Q38 of the energization control means 8 regardless of the output of the speed detection means 9, so that the transistor Q38 is turned off and the base of the transistor Q31 of the energization means 7 is naturally used. No voltage is applied to the device and the device is turned off to maintain the high efficiency mode.

In such a state where the speed is controlled, this minimum voltage is proportional to the margin of the drive current, and when the minimum voltage is approximately 1 V or less, the drive current is at its limit. If Q35, Q36 and Q37 are non-conductive and the output of the speed detecting means 9 is at a high potential in the high rotation mode, the transistor Q38 of the energizing control means 8 is turned on and naturally the base of the transistor Q31 of the energizing means 7 is obtained. When the voltage is applied, the middle point of the armature coil 5 is electrically connected to one end of the driving power supply 6 as described above, and the motor torque is switched to the high torque mode.

Once in the high torque mode, the transistor Q36 is turned off and the base voltage of the transistor Q35 acts so as to be high, and the mode is kept high until the armature voltage becomes sufficiently high, for example, higher than 1/2 of the power supply voltage. It does not switch. In this way, when the acceleration / deceleration ends and the speed becomes constant, the required torque becomes smaller and the minimum voltage rises, and when it becomes higher than the above voltage, the high efficiency mode is restored.

FIG. 4 shows the states of the minimum voltage and the armature current at the time of returning from the high-efficiency mode to the high-torque mode and then returning to the high-efficiency mode by the above configuration.
With this configuration, it is normally driven to rotate in the high-efficiency mode, and only when there is a large change in tracking, for example, when the device moves closer to the outermost circumference than the high rotation range where the innermost circumference of the disc is read. It will switch to torque mode.

Here, the CD-ROM according to the present invention is constructed.
The point of reducing the power consumption while shortening the acceleration / deceleration time of the rotation speed as the spindle motor will be described. FIG. 5 is a diagram showing changes in the number of revolutions and changes in current over time when the CD-ROM is read according to a predetermined program and changed at the track position using the brushless motor of the present invention as a spindle motor. Similarly to the above, the data read position is changed to the inner and outer circumferences around the speed of about 1800 rpm. As described above, the mode is a high efficiency mode with a small change or a constant speed, and the average current consumption is reduced by 25% because the torque constant is 25% higher than in the conventional example. However, since the mode is switched to the high torque mode when the position of the read track changes significantly, the armature current flows sufficiently and the torque generated by the motor is large, so the acceleration / deceleration time is shortened.

In the structure of the present embodiment, the rotor position detecting means 3 has been described as having a hall element.
For example, a method of detecting the position of the rotor according to the induced voltage of the armature coil or a method of detecting the position of the rotor according to the output signal of a separately provided frequency generator for speed detection is unique to the present invention. The effect of is not impaired. Further, various modes can be added as long as the present embodiment is not deviated, for example, a mode switching prohibition unit is appropriately added at an appropriate time, for example, when starting only in the high efficiency mode at the time of starting.

[0025]

According to the brushless motor according to the present invention described in detail above, a high torque mode for shortening the speed acceleration / deceleration time and a high efficiency mode with low power consumption are provided for each of the rotation speed and the armature coil. Since it is configured to automatically switch according to the terminal voltage, for example, when reproducing a CD-ROM disc, acceleration / deceleration in a narrow range that does not require a large torque can reduce power consumption in the high efficiency mode, and When it is necessary to perform large acceleration / deceleration by performing large tracking from the inner circumference to the outer circumference of the disk, a large torque can be obtained, the acceleration / deceleration time can be shortened, and the power consumption can be reduced.

Further, when the rotation speed of the motor is low so that the required torque can be obtained even in the high efficiency mode state, the high efficiency mode is set. Therefore, for example, power consumption at the time of starting acceleration may increase. It has features such as none.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a brushless motor of the present invention.

FIG. 2 is a specific circuit diagram of the present invention.

FIG. 3 is a torque rotation speed / current characteristic diagram according to an embodiment of the present invention.

FIG. 4 is a minimum voltage transition diagram at the time of mode switching.

FIG. 5 is a current-carrying timing chart of an embodiment of the present invention.

FIG. 6 is a block diagram of a conventional brushless motor.

FIG. 7 is a conventional torque rotation speed / current characteristic diagram.

FIG. 8 is a conventional current conduction timing chart.

[Explanation of symbols]

1 ... Brushless motor, 2 ... Rotor, 3 ... Rotor position detecting means, 4 ... Electronic commutator means, 5 ... Armature coil, 6 ...
Drive power source, 7 ... energizing means, 8 ... energizing control means, 9 ... speed detecting means, 10 ... armature voltage detecting means.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H02P 6/02 341 L

Claims (1)

[Claims] 1. A brushless motor comprising: a rotor having a permanent magnet; and a stator having a multi-phase star-connected armature coil, which is energized and driven through an electronic commutator means connected to a driving power source. An energizing unit that enables energization between the star-connected armature coil midpoint and the drive power source, a speed detecting unit that detects the rotation speed of the rotor, and detects each terminal voltage of the armature coil, A brushless motor comprising: armature voltage detection means for outputting the detection voltage; and energization control means for controlling the energization means according to the output of the armature voltage detection means and the output of the speed detection means. .