JPH0519201A - Rotary device - Google Patents

Abstract

PURPOSE:To shorten the time required for reaching a prescribed speed of revolution of a driving motor by controlling an actuating current to the driving motor in accordance with an output signal from a temperature detector. CONSTITUTION:In the rotary device for utilizing a dynamic pressure fluid bearing for a rotation driving device, a dynamic pressure generating part is provided by carving and providing a shallow groove on the outside peripheral surface of a shaft 1 driven to rotate or a sleeve 2 for holding the shaft, and in the vicinity of the dynamic pressure generating part, a temperature detector 18 is placed. That is, in a recessed part 2a of the outside of the sleeve 2 fitted so as to be freely rotatable to the rotary shaft 1, the temperature detector 18 such as a thermistor, etc., is attached, and in the case an output signal from this temperature detector 18 is a prescribed value or below immediately after the actuation, an actuating current of a driving motor is set in accordance with the output signal of the temperature detector 18. Accordingly, even if viscosity of oil and grease of the dynamic pressure fluid bearing part becomes high in the winter season and in a cold district, the motor reaches quickly a prescribed speed of revolution by allowing many actuating currents to flow, and the actuation time of the main body device using this rotary device until print is started, etc., is shortened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary device using a hydrodynamic bearing as a rotary drive device.

[0002]

2. Description of the Related Art Conventionally, in a deflection scanning device installed in a laser beam printer or the like, a non-contact rotatable hydrodynamic bearing has been used in order to obtain high speed and high precision rotation. FIG. 3 is a sectional view of a deflection scanning device of a laser beam printer using a hydrodynamic bearing. The rotary shaft 1 and the sleeve 2 are rotatably fitted together, the rotary shaft 1 is supported by a fixed plate 4 via a thrust plate 3, and the fixed plate 4 is fixed to an outer cylinder 5. A flange 6 is fixed to the rotary shaft 1, a rotary polygon mirror 7 is placed on the upper part of the flange 6, and a yoke 9 to which a driving magnet 8 is fixed is installed below the flange 6. Further, an electromagnetic coil 10 fixed to the outer cylinder 5 is arranged at a position facing the drive magnet 8 to form a drive motor.

Here, a shallow groove 11 is formed on the surface of the thrust plate 3 facing the lower end of the rotary shaft 1 to form a dynamic thrust bearing, and the outer peripheral surface of the rotary shaft 1 has a herringbone shape. The shallow groove 14 is engraved to form a dynamic pressure radial bearing,
Further, a spiral shallow groove 15 is engraved so that the lubricating fluid can flow to the hydrodynamic bearing. The sleeve 2 has a herringbone-shaped shallow groove 14 and a spiral-shaped shallow groove 15.
The concave portion 16 and the small diameter hole 17 are provided at the intermediate position of the above, and the stability of the dynamic pressure fluid bearing that uses a liquid such as oil or grease as the lubricating fluid is secured.

[0004]

However, when oil or grease is used as the lubricating fluid, the viscosity of the oil or grease changes with temperature, and the loss torque of the hydrodynamic bearing also changes greatly. . Therefore, it is difficult to reach the predetermined number of rotations, or it takes a long time to reach the predetermined number of rotations, and it takes a long time to start printing by a laser beam printer or the like. There is a problem.

The object of the present invention is to solve the above problems,
It is an object of the present invention to provide a rotating device that shortens the time required for the drive motor to reach a predetermined rotation speed.

[0006]

A rotating device according to the present invention for achieving the above object has a shaft for rotationally driving and a sleeve for holding the shaft, and the outer peripheral surface of the shaft or the sleeve. A shallow groove is engraved on the inner peripheral surface of the
A temperature detector is arranged in the vicinity of the dynamic pressure generation unit, and means for controlling a starting current of a drive motor for driving the rotary mirror according to a signal from the temperature detector is provided. is there.

[0007]

The rotating device having the above-described structure controls the starting current to the drive motor in accordance with the output signal from the temperature detector to adjust the time required to reach the predetermined rotation speed.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the embodiments shown in FIGS. The same reference numerals as those in FIG. 3 indicate the same members. FIG. 1 is a cross-sectional view, and since the configuration from the rotary shaft 1 to the small diameter hole 17 is the same as that of the conventional example, the description will be omitted. A temperature detector 18, such as a thermistor, is mounted in the recess 2a on the outer side of the sleeve 2 which is rotatably fitted to the rotary shaft 1. An output signal from the temperature detector 18 is supplied to a lead wire (not shown). It is connected to the detection circuit and the control circuit via.

When the power switch of the laser printer is turned on and the output signal from the temperature detector 18 is below a predetermined value, the starting current of the drive motor is set according to the output signal of the temperature detector 18. Therefore, when using the laser printer in winter or cold regions, even if the viscosity of the oil or grease in the hydrodynamic bearing is high immediately after the power switch is turned on, a large amount of starting current is used to prevent Reaching the number of rotations of, and shortening the time to start printing.

Further, when the temperature is extremely low, the starting current of the drive motor is too large and the motor drive circuit may be damaged. Therefore, the signal from the temperature detector 18 causes the device temperature to reach a predetermined value. Operates so that the drive motor is de-energized. Further, when the temperature is equal to or higher than a certain predetermined temperature, the drive motor starting current may be kept constant.

As described above, the temperature detector 18 is installed in the vicinity of the dynamic pressure fluid bearing portion, and the starting current flowing through the drive motor is controlled according to the signal from the temperature detector 18, so that the deflection scanning device can be operated. The print start time of the installed laser beam printer can be kept within a predetermined time, and the device can be prevented from being damaged when the temperature is extremely low.

FIG. 2 is a sectional view showing a second embodiment.
The sleeve 2 is provided with recesses 2b at positions opposed to the two herringbone-shaped shallow grooves 14 of the rotary shaft 1 for generating radial dynamic pressure, and a temperature detector 18 is installed in the recess 2b. . The lead wire from the recess 2b of the temperature detector 18 is sealed by a seal member (not shown),
The lubricating fluid inside does not leak out.

This embodiment also has the same operation and effect as the previous embodiment, but in this case, the temperature detector 18 is in direct contact with the lubricating fluid, so that the response is good and a more reliable operation is guaranteed. To be done.

In these two embodiments, the rotary shaft 1
Although the case where the shaft rotates is described, the same effect can be obtained by installing the temperature detector 18 on the fixed shaft even when the shaft is fixed and the sleeve 2 rotates. Further, the shallow groove for generating dynamic pressure may be formed on either the outer peripheral surface of the shaft or the inner peripheral surface of the sleeve.

Although the deflection scanning device attached to a laser beam printer or the like has been described in the embodiment, it can be applied to a highly accurate rotating device such as a rotating head assembly of a magnetic recording and reproducing device (VTR).

[0016]

As described above, in the rotating device according to the present invention, the temperature detector is installed near the dynamic pressure generating portion of the hydrodynamic bearing, and the drive motor is started in response to the output signal from the temperature detector. By controlling the current, it is possible to shorten the time required for the drive motor to reach a predetermined rotation speed at low temperatures, and prevent circuit damage due to excess current to the drive motor.

[Brief description of drawings]

FIG. 1 is a sectional view of a first embodiment.

FIG. 2 is a sectional view of a second embodiment.

FIG. 3 is a sectional view of a conventional deflection scanning device.

[Explanation of symbols]

1 rotation axis 2 sleeve 7 rotating polygon mirror 2a, 2b recess 11, 14, 15 shallow groove 18 Temperature detector

Claims (4)

[Claims] 1. A shaft for rotating and a sleeve for holding the shaft, wherein a shallow groove is formed on the outer peripheral surface of the shaft or the inner peripheral surface of the sleeve to provide a dynamic pressure generating portion. A rotating device comprising a temperature detector arranged in the vicinity of the dynamic pressure generating portion, and means for controlling a starting current of a drive motor for driving the rotating mirror according to a signal from the temperature detector. 2. The rotating device according to claim 1, wherein when the signal from the temperature detector deviates from a predetermined temperature, power supply to the drive motor is cut off. 3. The rotating device according to claim 1, wherein the temperature detector is in direct contact with a fluid interposed in the dynamic pressure generating portion. 4. The rotating shaft is attached to the axis for deflecting and scanning the light beam emitted from the light beam generating means.
The rotating device according to.