JPH0412655A - High-speed motor or scanner motor - Google Patents

Abstract

PURPOSE:To remove the thermal deformation of a rotary polygon mirror or the unbalance by fluid force even in high-speed revolution by constituting a scanner motor in a sealed vessel of a low pressure of tens of Torrs or less, and driving it. CONSTITUTION:In a scanner motor, the rotary polygon mirror 1 is attached to a rotor 3 by a plate spring 16 being an elastic substance, and the shaft 2 supported by a bearing 5 is press-fit in this. The rotor 3 is driven by a rotor 9, consisting of a permanent magnet, and an armature 8, and for the revolution, the magnetic change of a magnet ring 10 is detected with a Hall element and is controlled. And since it is sealed with a motor case 11, a mirror cover 14, and a bearing case 6, and the inside is under a low pressure, the constituent parts gets at uniform temperature by radiation cooling. Accordingly, the thermal deformation of the rotary polygon mirror does not occur, and there is no deterioration of rotation accuracy caused by thermal factors. Furthermore, since fluid force hardly acts upon the rotary polygon mirror, unstable vibration does not occur even at high-speed rotation, and highly accurate rotation can be gotten.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a high-speed motor that is operated at high speed, particularly at a speed exceeding 10,000 rpm+, and is used as a motor for parking a scanner of a laser beam printer, and exhibits remarkable effects. It is something.

[Conventional technology]

For example, a laser beam printer is equipped with a rotating polygon mirror for deflecting a laser beam onto transfer paper. Rotating polygon mirrors are driven by scanner motors, but in response to recent demands for high-speed printing and high definition, there is a need for ultra-high-speed motors that are free from uneven rotation and center runout. In particular, it is known that tilting of the polygon mirror due to center runout or the like significantly reduces printing quality.

However, the rotating polygon mirrors conventionally used for high-speed scanning of laser beams are required to have low rotational accuracy on the order of micrometers or submicrometers, and this objective cannot be achieved only by improving the performance of single-wire bearings. That is, the fourth
As shown in the figure, when the mounting accuracy Δ2 of the rotating polygon mirror 1 having 6 to 12 surfaces is, for example, several micrometers, the amount of variation Δy of the beam scanning position on the photoreceptor surface is expanded to several tens of micrometers, and the printing accuracy is increased. There is a problem with it being damaged. This is related not only to processing accuracy and assembly accuracy, but also to dynamic factors during rotation. Specifically, in order to suppress the amount of variation in the beam scanning position to 10 μm or less, the mounting surface a of the rotating polygon mirror 1 is
The rotating polygon mirror 1 is attached via an elastic body 16 to prevent mechanical deformation so that it will not be tightened with excessive force.

Furthermore, in order to suppress shaft vibration to the order of submicron meters, various measures have been taken to maintain high precision rotation even during operation using the above-mentioned dynamic pressure group bearing.

JP-A-61-157820 also has the above-mentioned dynamic pressure group bearing, but even with this, it is difficult to provide sufficient accuracy.

[Problem to be solved by the invention]

However, conventional scanner motors do not take into account the thermal deformation of the rotating polygon mirror and fluid forces, and the higher the rotation speed, the lower the rotational precision becomes, creating the problem that high-definition printing cannot be achieved. That is, the scanner motor is 200
Since the iron loss of the electric core of the motor that rotates at 00 rpm or more increases significantly, during operation of the scanner motor, the heat generated by the motor is transferred from the mounting surface a to the rotating polygon mirror 1 and heated. However, although the rotating polygon mirror 1 is cooled by the fan effect caused by rotation, the temperature at the mounting surface a is high, so due to the thermal expansion on this surface, the rotating polygon mirror 1 is slightly heated up, as shown in Fig. 5. Curved deformation, 2
When rotating at a high speed of 000 rpm or higher, thermal deformation of the rotating polygon mirror cannot be ignored. In addition, when rotating at such high speed, not only does the resistance to agitating the air increase significantly due to the polyhedron, but also the unbalance caused by the fluid resistance that the rotating polygon mirror 1 receives increases, inducing unstable vibrations and causing rotational vibrations to increase. It may also increase. Furthermore, this unbalance of fluid force is a direct cause of uneven rotation, so there is a drawback that high-precision rotation cannot be expected.

Conventional scanner motors do not take into account problems such as thermal deformation of the rotating polygon mirror and reduction in rotational accuracy due to unbalanced fluid force, and improvements in machining accuracy and assembly accuracy and improvements in bearings are required. etc. solved the problem.

SUMMARY OF THE INVENTION An object of the present invention was made in view of the drawbacks of the prior art, and it is an object of the present invention to provide a high-speed motor, particularly a scanner motor for a laser beam printer, which can be used with high precision even at high speeds.

Specifically, it is an object of the present invention to provide a scanner motor that rotates with high precision without thermal deformation of a rotating polygon mirror or unbalance due to fluid force during operation.

[Means to solve the problem]

According to the present invention, the above object is achieved by driving the rotating portion of the scanner motor in a reduced pressure environment. In other words, the scanner motor is configured in a sealed container, and the pressure inside this sealed container is reduced to several tens of Torr or less to keep it airtight.By driving, the thermal deformation of the rotating polygon mirror and the unbalance of fluid force can be avoided. This solves problems such as the occurrence of unstable vibrations.

Effect C] When a rotating polygon mirror is driven in a reduced pressure environment, the fan effect due to rotation as in a conventional scanner motor cannot be expected, so the rotating polygon mirror is heated to a -like temperature. Therefore, there is no possibility of partial thermal expansion on the mounting surface of the rotating polygon mirror, and therefore, thermal deformation of the rotating polygon mirror as in conventional scanner motors does not occur. In addition, although a rotating polygon mirror is a polyhedron with 6 to 12 sides, air resistance is negligibly small in a reduced pressure environment, that is, in a thin fluid, so there is no unbalanced force caused by air agitation as in the past, and it can be used at low speeds. High rotational accuracy can be obtained from to high speed rotation.

〔Example〕

Hereinafter, one embodiment of the configuration of the present invention will be described based on the drawings. FIG. 1 shows an embodiment of a scanner motor for a laser beam printer to which the present invention is applied.

The rotating polygon mirror 1 is attached to the rotor 3 through an elastic body 16 by being lightly pressed with a stopper 16.

Further, a shaft 2 is press-fitted into the center of the rotor 3, and is rotatably supported by a bearing 5 incorporated in a bearing box 6. 4 is a magnetic fluid seal that prevents the lubricating oil of the bearing 5 from scattering. The rotor 3 is driven by a motor rotor 9 made of permanent magnets fixed to the rotor 3 and an armature 8 for generating a magnetic field placed opposite to its outer periphery.The rotation speed is controlled by multi-pole magnetization. The magnetic flux of the magnet ring 10 is changed using a Hall element (not shown). The scanner motor configured in this manner has a chamber sealed by the motor case 11, mirror cover 14, and bearing case 6, and internal air is evacuated from the sealed tube 12 by a vacuum pump (not shown). , reduce the pressure to an appropriate level and seal.

During operation, the laser beam is incident through the glass window 22, and the shape of the glass window 22 is a flat glass plate so that the laser beam travels straight through and is reflected. Further, the rotating polygon mirror 1 is attached using an elastic body 16 so as not to be deformed, and a plate spring is used as the elastic body 16.

In such a configuration of the scanner motor, the temperature of the rotor 3 rises due to heat generated by the motor rotating at high speed, and the heat is transferred from the mounting surface a to the rotating polygon mirror 1 and heated. Furthermore, since the interior is depressurized and in a thin state, the rotating polygon mirror 1 cannot self-cool by rotation like a conventional scanner motor, resulting in an almost negative temperature distribution. This is because radiation cooling is dominant in heat dissipation in a reduced pressure environment, and the cooling effect is less than in atmospheric conditions, so the components are -
The temperature will vary. Therefore, since the rotating polygon mirror 1 has a negative temperature distribution, thermal deformation as in the conventional case does not occur. In addition, since the internal pressure is reduced and the motor rotates, there is no windage loss caused by rotating parts, and the power consumption of the motor is reduced. is not that expensive either. moreover,
Since the fluid resistance experienced by the rotating polygon mirror is negligible in a reduced pressure environment, unstable vibrations based on fluid force do not occur. Therefore, in the bearing 5 that supports the shaft 2,
Stable rotation can be maintained without using very high rigidity bearings.

FIG. 2 shows an embodiment of a bearing device, in which a bearing case 6 includes a magnetic fluid seal 4 composed of a permanent magnet 17 and a magnetic pole piece 18, a radial bearing 19, and a thrust bearing fitted into a bearing retainer 7. 2o is incorporated to rotatably support the shaft 2. Reference numeral 21 denotes a lubricating magnetic fluid, and the magnetic fluid 21 is used as a lubricating fluid for the bearing 19 so that even if the magnetic fluid scatters due to the rotation of the shaft 2, it is captured by the magnetic fluid seal 4 and does not contaminate the outside. Furthermore, the air bearings used in conventional scanner motors are dynamic pressure group bearings with a shaft diameter of φ15m + dimensions of around 15m, but in a reduced pressure environment, unbalanced forces due to fluid agitation do not act on the rotating polygon mirror. A cylindrical bearing with a shaft diameter of around φ4 can be used, and has advantages such as being inexpensive as a bearing device and making the scanner motor compact.

This scanner motor may be depressurized and sealed one by one, but since it is a mass-produced product, a large number of motors assembled as shown in Figure 1 are placed in an airtight container for exhaust, the pressure is depressurized with a vacuum pump, and then sealed. The end of the stop tube 12 is closed to keep the inside of the motor airtight. A sealing device for the sealing tube 12 is attached to an airtight container for exhaust, and after reducing the pressure to an appropriate level, the sealing device is operated to seal the tube.

FIG. 3 shows another embodiment of the present invention, in which the faster the motor rotates, the more the iron loss in the armature core 8 increases and the temperature rises. Therefore, in the configuration shown in FIG. 3, the armature 8 is arranged around the outer periphery of the motor case 11, and
heat is radiated directly into the atmosphere. In this configuration, the gap between the motor's armature 8 and the rotor 9 becomes wider and the driving force of the motor decreases, but at rated rotation, rotation is maintained with a driving force equivalent to the friction loss (several watts) of the bearing 5. Therefore, the scanner motor exhibits the same effect as the scanner motor shown in FIG. 1, except that the startup time is longer.

Furthermore, as described above, the scanner motor according to the present invention does not suffer from deterioration in rotation accuracy due to thermal factors, and furthermore, since almost no fluid force acts on the rotating polygon mirror, highly accurate rotation can be obtained. Laser beam printers using scanner motors can produce high-speed printing and high-definition images.

〔Effect of the invention〕

According to the present invention, since the rotating polygon mirror is driven in a reduced pressure environment as described above, vibrations during rotation are reduced. Particularly when applied to a scanner motor, thermal deformation of the rotating polygon mirror does not occur, and there is no deterioration in rotation accuracy due to thermal factors. Furthermore, since almost no fluid force acts on the rotating polygon mirror, unstable vibrations do not occur even during high-speed rotation, and highly accurate rotation can be achieved. Further, the scanner motor according to the present invention consumes less power than conventional scanner motors, and can provide a compact motor, which is effective in downsizing laser beam printers. Furthermore, a laser beam printer using this motor with low vibration and high precision rotation has advantages such as high speed printing and high definition image quality.

[Brief Description of the Drawings] Fig. 1 is a vertical sectional view of a scanner motor according to the present invention;
3 is a longitudinal sectional view showing another embodiment of the scanner motor according to the present invention, FIG. 4 is a partial sectional view of a conventional scanner motor, and FIG. 5 is a longitudinal sectional view of a conventional scanner motor. FIG. 2 is an explanatory diagram showing thermal deformation of a rotating polygon mirror. 1... Rotating polygon mirror, 3... Rotor, 5... Bearing,
8...Mo Figure 1 Figure 3

Claims (1)

[Scope of Claims] 1. A high-speed vehicle that includes a rotor, a bearing device that rotatably supports the rotor, a stator disposed opposite to the rotor, and a space containing the rotor and the bearing device in a sealed state. A high-speed motor in which the space is in a reduced pressure state. 2. The motor consists of a motor rotor equipped with a rotating polygon mirror, a bearing device that rotatably supports this rotor, an armature placed opposite to the motor rotor, a motor case to which the armature is fixed, and a mirror cover. A scanner motor whose one end is closed with a Miracover and the other end is closed with a bearing case, and the internal pressure is reduced. 3. The scanner motor according to item 2 above, wherein the armature is attached to the outer periphery of the motor case, and the rotating components and bearing device are placed in a depressurized chamber. 4. The scanner motor according to item 2, wherein a sealing tube is provided in a part of the case, and the sealing tube prevents outside air from flowing in.