JP2000270588A - Dynamic pressure bearing motor controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce rotation period, while the rotary shaft of a dynamic pressure motor is brought into contact with a bearing and reduce the wear of the shaft and bearing. SOLUTION: A velocity command signal and a velocity detection signal related to a dynamic pressure bearing motor are compared with each other by a comparison unit 1 and a deviation (e) is outputted. A driver unit 3 controls a drive current applied to the dynamic pressure bearing motor M so as to reduce the deviation (e). The revolution detection unit FG detects the number of revolution of the motor M. A 1st velocity detection unit 7 outputs the velocity detection signal corresponding to the revolution in accordance with the detection signal of the revolution detection unit FG to the comparison unit 1. A 2nd velocity detection unit 9 compares its detected velocity with a reference velocity, corresponding to the revolution of 1/2-1/4 of the rated revolution of the motor M, and if the detected velocity is reduced below the reference velocity, outputs a brake signal S to the driver unit 3. The driver unit 3 controls the brake of the dynamic pressure bearing motor M based on with the brake signal S.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dynamic pressure bearing motor control device, and more particularly, to a control device for controlling braking during deceleration of a dynamic pressure bearing motor having a dynamic pressure floating bearing.

[0002]

2. Description of the Related Art Conventionally, as a control device for controlling a hydrodynamic bearing motor, as shown in FIG. 3, for example, a comparing unit 1 compares a speed command signal externally commanded and a speed detection signal of the hydrodynamic bearing motor M. And outputs a deviation e. Based on the deviation e, the driver unit 3 drives the plurality of drive coils L of the dynamic pressure bearing motor M by switching the drive current and energizing the drive coils.
The frequency generator FG disposed in the hydrodynamic bearing motor M generates and outputs a frequency signal corresponding to the number of rotations, and the speed detector 5 detects the number of rotations by converting the frequency signal into a voltage signal having a level corresponding to the frequency signal. At the same time, it has a configuration in which this is output to the comparison unit 1 as a speed detection signal.

Although not shown in detail, the hydrodynamic bearing motor M is a polygon mirror motor used for a laser printer, a digital copying machine, or the like, or a motor used for a VCR or a hard disk drive. A fluid medium such as air or oil is interposed between the bearing and the bearing (neither is shown), and the rotating shaft is supported by the fluid medium without direct contact with the bearing during steady high-speed rotation. To ensure stable high-speed rotation.

Although FIG. 3 shows the drive coil L and the frequency generator FG taken out of the hydrodynamic bearing motor M, they are actually built in. same as below.

[0005] As shown in FIG.
When the power is turned on (ON) to start up, the rotating shaft and the bearing are in a contact rotating state until the rotating speed reaches a predetermined rotating speed D, and when the rotating speed increases beyond this, the rotating shaft and the bearing increase.
A fluid medium is interposed between the bearing and the bearing over the entire outer periphery of the rotating shaft, whereby the rotating shaft floats, and a high-speed rated rotation is secured.

However, the predetermined number of rotations at which the rotating shaft shifts from a state of partial contact with the bearing to a floating state greatly differs depending on the configuration of the hydrodynamic bearing motor as described later. Thereafter, when the power is turned off (OFF), the drive current from the driver unit 3 is cut off. However, when the rotation shaft is decelerated while rotating due to inertia and decelerated to a predetermined rotation speed D,
Again, the rotation shaft stops after passing through a contact rotation state in which the rotation shaft partially contacts the bearing.

[0007]

However, when the rotation of the dynamic bearing motor M is controlled by the dynamic bearing motor control device having the above-described configuration, when the power is turned on (ON) as shown in FIG. As shown in FIG. B, although the rotating shaft and the bearing are immediately brought into a non-contact state immediately after the high-speed rotation as shown in FIG. B, when the power is turned off (OFF), the rotating shaft decelerates to a predetermined speed. After the rotation shaft is decelerated to the rotation speed D and the rotation shaft partially contacts the bearing again, the sliding period from this contact rotation state to the complete stop is relatively long, and the wear of the rotation shaft and the bearing tends to progress. is there.

For example, when the rated speed is 30,000 rpm
With the hydrodynamic bearing motor M, it takes about one minute from when the power is turned off to the contact rotation state until the rotary shaft completely stops, and it is desired to improve the durability of the rotary shaft and the bearing. I was

In addition, the rotational speed D at which the rotating shaft partially comes into contact with the bearing and comes into a contact rotation state is not constant, but generally varies easily from 5,000 rpm to 1,000 rpm, and completely stops. There is also a drawback that the period of time to do so is not fixed.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and a motor having a dynamic pressure bearing is provided with a dynamic pressure reduction by shortening a contact rotation period between the rotating shaft and the bearing in the braking process. An object of the present invention is to provide a dynamic pressure bearing motor control device capable of improving the durability of a bearing motor.

[0011]

SUMMARY OF THE INVENTION In order to solve such a problem, a dynamic pressure bearing motor control device according to the present invention comprises a speed command signal corresponding to a target rotational speed and a speed detection signal relating to the dynamic pressure bearing motor. And a comparing unit that outputs a deviation by comparing the driving current to the hydrodynamic bearing motor so as to reduce the deviation, and a driver unit that controls the rotational driving of the driving current.
A rotation speed detection unit for detecting the rotation speed of the hydrodynamic bearing motor, a first speed detection unit for outputting a speed detection signal corresponding to the rotation speed based on the detection signal from the rotation speed detection unit, A second speed detecting section for outputting a braking signal when a detection signal from the detecting section falls below a predetermined reference speed, wherein the driver section controls the dynamic pressure bearing motor by the braking signal. Have been.

In the present invention, the driver section can be formed so as to apply a short-circuit control to the drive coil for rotating the rotor in the dynamic pressure bearing motor to apply the braking. Further, in the present invention, it is preferable that the reference speed in the second speed detector is selected in a range of 1/2 to 1/4 of the rated rotation speed of the hydrodynamic bearing motor.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. Note that the same reference numerals are given to portions common to the conventional example.

FIG. 1 is a block diagram showing an embodiment of a dynamic bearing motor control device according to the present invention. In FIG. 1, a comparison unit 1 compares a variable or fixed speed command signal output from a speed command signal forming unit (not shown) with a speed detection signal from a first speed detection unit 7, which will be described later, and calculates a deviation e. And is connected to the driver unit 3.

The driver section 3 switches the drive current and supplies the current, and is connected to, for example, a plurality of drive coils L of the hydrodynamic bearing motor M. Based on the deviation e, the drive section 3 reduces the drive current to reduce the drive current. The current is switched to L and the dynamic pressure bearing motor M is driven to rotate. The driver unit 3 has other functions, but details will be described later.

Although not shown in detail, the hydrodynamic bearing motor M has, for example, a bearing and a plurality of drive coils L arranged on the stator side, and a fluid medium such as air or oil is provided between the bearing and the inner wall in the bearing. A conventionally known brushless configuration in which a rotating shaft is inserted with the intervening state, and a rotor magnet, a polygon mirror, and the like are arranged on the rotating shaft, without directly contacting the bearing at the time of rotation at a predetermined rotation speed or more The rotating shaft is supported by a floating shaft with a fluid medium interposed therebetween to ensure stable high-speed rotation.

The hydrodynamic bearing motor M has a conventionally known frequency power generation unit FG as a rotation speed detection unit for generating and outputting a frequency signal having a frequency corresponding to the rotation speed. It is connected to the first speed detector 7 and the second speed detector 9.

The first speed detecting section 7 includes a frequency power generating section FG
The rotational speed is detected by converting the voltage signal into a voltage signal having a level corresponding to the frequency signal from the controller, and this voltage signal is output to the above-described comparison unit 1 as a speed detection signal. In addition, this first
Is substantially the same as the speed detecting unit 5 in FIG. 4 described above, but the reference numerals are changed for convenience.

The second speed detecting section 9 includes a frequency power generating section FG.
Is converted into a voltage signal of a level corresponding to this frequency to detect the rotation speed, and the detected voltage and a reference braking start rotation speed (reference speed: reference rotation speed)
It compares a reference voltage corresponding to F and outputs a braking signal S when the detected voltage falls below the reference voltage, and is connected to the driver unit 3 described above.

The braking signal S is, as shown in FIG. 2B, a pulse-like transient signal or a continuous signal (not shown) which continues to be output until the detected voltage falls below the reference voltage and is reset. The second speed detector 9 may be formed accordingly.

The driver section 3 cuts off the drive current flowing through the drive coil L based on the input braking signal S, and also drives the drive coil L with, for example, a resistor (not shown).
For example, the dynamic pressure bearing motor M is forcibly braked by short-circuiting or the like, and the brake is applied until the rotary shaft is completely stopped and reset.

Next, the operation of the above-described hydrodynamic bearing motor control device of the present invention will be briefly described. As shown in FIG. 2A,
When the power is turned on (ON) and a start operation is performed, a speed command signal is applied to the comparison unit 1. However, since a speed detection signal is not input or extremely small, a large deviation e is applied to the driver unit 3, and the driver unit 3 A large drive current is switched and energized to the drive coil L of the hydrodynamic bearing motor M, and the rotating shaft starts to start as shown in FIG.

The rotating shaft, which is in a contact rotation state in which the bearing is partially in contact with the bearing, immediately reaches a predetermined number of revolutions and becomes a floating state, so that stable high-speed rotation is secured.

In the steady rotation state, the driver unit 3 controls the dynamic pressure bearing motor M so that the deviation e from the speed detection signal from the first speed detecting unit 7 corresponding to the rotational speed of the dynamic pressure bearing motor M becomes small. Control the steady rotation. In this state, since the voltage signal level corresponding to the frequency signal from the frequency generator FG is higher than the reference voltage, the braking signal S is not output from the second speed detector 9 to the driver 3.

Then, as shown in FIG. 2A, the power is turned off (OF).
F), when the stop operation is performed, the drive current from the driver unit 3 is cut off, and the rotating shaft of the hydrodynamic bearing motor M continues to rotate due to inertia, but the rotation speed decreases.

When the frequency of the frequency signal from the frequency generator FG also decreases, and the detection signal level accompanying the frequency signal drops below the reference speed level, as shown in FIG. S is applied to the driver unit 3,
In the driver section 3, the drive coil L is short-circuited.

[0027] Therefore, when the drive coil L is short-circuited, the hydrodynamic bearing motor M that continues to rotate functions as a generator, and the current induced in the drive coil L by the rotation is consumed by the above-described resistance and used as a brake. As a result, as shown in FIG. 2C, the dynamic pressure bearing motor M is forcibly braked and the rotation stops immediately.

In the delay t in FIG. 2B, the power is off (OFF).
This is a delay time from when the braking signal S is output until the braking signal S is output.

As described above, the dynamic bearing motor control device of the present invention compares and subtracts the speed command signal and the speed detection signal of the dynamic bearing motor M to output the deviation e, and the deviation e. A driver unit 3 for supplying a drive current to the dynamic pressure bearing motor M so as to reduce the rotational speed and controlling the rotation of the driver unit, a frequency power generation unit FG for detecting the rotation speed of the dynamic pressure bearing motor M, and a frequency power generation unit A first speed detector 7 for outputting a speed detection signal corresponding to the number of revolutions based on a detection signal from the FG, and a braking signal S when the detection signal from the frequency generator FG falls below a predetermined reference speed. And a second speed detection unit 9 for outputting the
Is configured to control the braking of the hydrodynamic bearing motor M by the braking signal S, so that when the hydrodynamic bearing motor M is stopped, the rotating shaft that continues to rotate due to inertia has its reference speed F
, The rotation axis is braked,
The rotating shaft stops immediately.

Therefore, if the reference speed F in the second speed control section 9 is appropriately selected, the rotation of the hydrodynamic bearing motor M can be stopped immediately after the stop operation and the contact rotation state. Therefore, the contact rotation period, that is, the sliding rotation period, between the rotating shaft and the bearing is shortened, and the durability of the dynamic pressure bearing motor M, particularly, the durability of the rotating shaft and the bearing can be significantly improved.

In addition, since the driver section 3 controls the driving coil L of the hydrodynamic bearing motor M in a short-circuit manner, it is possible to apply a reliable and efficient braking by the power generating action accompanying the rotation of the hydrodynamic bearing motor M by inertia. In addition, the configuration of the braking circuit is simplified.

In particular, the reference speed F selected by the second speed detection unit 9 is set to １ ／ of the rated rotation speed of the hydrodynamic bearing motor M.
If １ ／ is selected, if the rotation is restarted before decreasing to the reference speed F, the floating (non-contact) state of the rotating shaft will not be shortened unnecessarily, as compared with restarting from the contact rotation state. Quick restart is possible.

In general, a recent electronic device equipped with a motor, such as a printer, has a function of turning off a motor or the like when the use of the motor is stopped for a certain period of time. If the rotation of the motor is stopped, not only does it take time to restart, but if this operation is repeated, the calorific value increases both during acceleration and braking of the hydrodynamic bearing motor, and the hydrodynamic bearing motor heats up abnormally. Can be considered.

In this regard, if the reference speed F is selected to be ２〜 to の of the rated rotation speed of the dynamic bearing motor M, after controlling the dynamic bearing motor to OFF, the reference speed F is reduced to ２〜 to 1１ of the rated rotation speed.
If the motor is restarted within the period of / 4, such a motor abnormality can be avoided, and a preferable restart period can be secured relatively long.

The range of 1/2 to 1/4 of the rated rotation speed of the hydrodynamic bearing motor M is a rotation speed or rotation speed slightly higher than the rotation speed (rotation speed) at which the contact rotation of the rotary shaft starts. When the speed is preferable and the configuration of each hydrodynamic bearing motor is determined, its specific rotation speed is also determined.

The configuration for braking the rotation of the dynamic pressure bearing motor M in the present invention is arbitrary, and is not limited to the configuration in which the drive coil of the dynamic pressure bearing motor M is short-circuited via a resistor as described above. The period in which braking is applied to the pressure bearing motor M is also arbitrary, and the driver section 3 may be appropriately formed in accordance with the braking period.

As for the configuration for applying the braking, for example, in addition to the configuration in which a drive current for generating a reverse rotation torque on the rotating shaft is supplied from the driver unit 3 to the driving coil L, the braking signal from the second speed detecting unit 9 is also provided. A mechanical configuration or the like that applies a load such as mechanically tightening the rotating shaft of the hydrodynamic bearing motor M by S may be considered. The object of the present invention can also be achieved if the frequency power generation unit FG that detects the rotation speed of the dynamic pressure bearing motor M is a rotation speed detection unit that detects the rotation speed of a conventionally known motor.

The hydrodynamic bearing motor M controlled by the hydrodynamic bearing motor control device of the present invention can be implemented in a conventionally known general configuration, and the configuration is not limited.

[0039]

As described above, according to the present invention, the deviation is output by comparing the speed command signal corresponding to the target rotational speed with the speed detection signal relating to the hydrodynamic bearing motor by the comparison section, and this deviation is output. A drive current is supplied from the driver section to the hydrodynamic bearing motor so that the rotational speed of the hydrodynamic bearing motor is reduced, and the rotational speed of the hydrodynamic bearing motor is detected by the rotational speed detecting section. A speed detection signal corresponding to the rotation speed is output from the first speed detection unit to the comparison unit based on the above, and the detection signal from the rotation speed detection unit is similarly compared with the reference speed by the second speed detection unit, and is compared with the reference speed. A braking signal is output to the driver unit when the voltage exceeds the threshold, and the driver unit is configured to control the braking of the hydrodynamic bearing motor by the braking signal. Contact rotation period of the motor rotating shaft and the bearing is shortened, it becomes possible to greatly improve the durability of the dynamic bearing motor. Further, according to the present invention, in the dynamic pressure bearing motor, in the configuration in which the driver section is formed so as to apply the short-circuit control to the drive coil for rotating the rotor to apply the braking, efficient braking can be applied with a simple configuration.
Further, according to the present invention, in the configuration in which the reference speed is selected to be 1/2 to 1/4 of the rated rotation speed of the hydrodynamic bearing motor in the second speed detection unit, it is possible to reliably stop the motor in a short period. In addition, since the floating state can be maintained for a relatively long time, when it is necessary to restart the vehicle immediately, it is possible to quickly restart from the floating state, and it is easy to realize conflicting demands.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an embodiment of a dynamic bearing motor control device of the present invention.

FIG. 2 is a diagram illustrating the operation of the dynamic bearing motor control device of FIG. 1;

FIG. 3 is a block diagram showing a conventional hydrodynamic bearing motor control device.

FIG. 4 is a diagram for explaining the operation of the dynamic bearing motor control device of FIG. 3;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 comparison unit 3 driver unit 5 speed detection unit 7 first speed detection unit (speed detection unit) 9 second speed detection unit FG frequency power generation unit (rotation speed detection unit) L drive coil M dynamic pressure bearing motor

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H530 AA01 AA07 BB10 BB14 CC08 CC24 CD22 CE15 CF02 DD03 DD12 EE01 5H560 AA04 AA10 BB04 BB07 BB12 DB07 EB01 HB05 JJ01 TT06 TT07 UA02 XA04

Claims (3)

[Claims] A comparison section for comparing a speed command signal corresponding to a target rotational speed with a speed detection signal related to a hydrodynamic bearing motor to output a deviation, and the dynamic pressure bearing so as to reduce the deviation. A driver section for supplying a drive current to the motor to rotate the motor, a rotation number detection section for detecting the rotation number of the hydrodynamic bearing motor, and a rotation number corresponding to the rotation number based on a detection signal from the rotation number detection section. A first speed detection unit that outputs the speed detection signal; and a second speed detection unit that outputs a braking signal when the detection signal from the rotation speed detection unit falls below a predetermined reference speed. The driver unit is configured to control the braking of the dynamic bearing motor by the braking signal. 2. The dynamic pressure bearing motor control device according to claim 1, wherein the driver section applies short-circuit control to a drive coil that rotates the rotor in the dynamic pressure bearing motor to apply braking. 3. The dynamic pressure bearing according to claim 1, wherein the second speed detector selects the reference speed to be 1/2 to 1/4 of a rated rotation speed of the dynamic pressure bearing motor. Motor control device.