JPH02223361A - Polygon scanner motor and its manufacture - Google Patents

Abstract

PURPOSE:To improve the rotating accuracy of a polygon mirror by conducting fitting of the inner ring and outer ring of a ball bearing on the operating side and the inner ring of a ball bearing on the non-operating side through a rest fit and fitting of the outer ring thereof through a loose fit and by bringing an axial pre-load spring and a radial lateral-pressure spring into contact with said outer ring of the ball bearing on the non-operating side. CONSTITUTION:Fitting of the inner ring and outer ring of a ball bearing 3a on the operating side and the inner ring of a ball bearing 3b on the non-operating side is conducted through a rest fit and fitting of the outer ring of the ball bearing 3b on the non-operating side, through a loose fit; and an axial pre-load spring 11 and a radial lateral-pressure spring 33 are brought into contact with the outer ring of the ball bearing 3b on the non-operating side. Because said pre-load spring 11 is added in the direction of a rotating shaft 24 therefore, rolling elements (balls) roll in both bearings 2a, 2b by an appropriate pre-load without any space from rolling surfaces (inner and outer rings). As a result, the rotating shaft 24 is settled in the center of rotation relative to the both bearings 2a, 2b so that its rotating accuracy is improved and its vibration is eliminated. Accordingly, the rotating accuracy of a polygon mirror 8 is improved too.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is used in laser beam printers, digital copying machines, etc., and is particularly suitable for high-capacity printers. The present invention relates to a polygon scanner motor that rotates at a high speed of approximately OOOrpm to 30.00Orpm, and a method for manufacturing the same.

[Conventional technology]

Fig. 2 is a half-sectional view of a conventional polygon scanner motor with a speed of up to about 5.00 Orpm. Fit and rotate shaft 4
is supported. This type of motor is generally used as a heavy wheel. An outer rotor 7 made of a permanent magnet is connected around the stator 5 with a winding attached to the outer periphery of the housing 2a on the driving side via a cork 6 attached to the shaft end on the driving side.
are placed with a gap in between. One end of the yoke 6 serves as a mounting portion 6a for a polygon mirror 8, and the polygon mirror 8 is rotatably fixed with a bolt 10 via a washer 9.

The fit between the inner ring and the outer ring of the ball bearing 3a on the driving side and the fit between the inner ring of the ball bearing 3b on the non-driving side are a stop fit (including an interference fit), and are tightly (fitted) with the rotating shaft 4 or the housing 2a. ball bearing 3b on the non-driving side
The fit between the outer ring and the housing 2b is a loose fit so that they can slide in the axial direction, and a preload spring 11 such as a coil spring is used.
is installed to absorb the internal gap between the ball bearings 3a and 3b.

This is a structure that is often adopted in order to increase the rotation accuracy of the rotating shaft 4, reduce the rotation noise of the bearing, and extend the life of the bearing.
2 is attached to the bracket l, and a printed circuit board 13 provided with a Hall element 13a is attached to the bracket l.

Since the ball bearings 3a and 3b are of a sealed type, and the driving side is surrounded by a yoke 6, the bearing lubricant is prevented from scattering outside and contaminating the mirror surface on the outer periphery of the polygon mirror 8. It will be done. Further, the rotating body can be balanced on the outer periphery of the end face of the yoke 6.

[Problem to be solved by the invention]

When the above-mentioned conventional technology is applied to a motor with a speed of 10.00 Orpm or higher, the following problem occurs.

a) Balance can be achieved only on one side of the yoke 6, so although static balance can be achieved, dynamic balance cannot be achieved, resulting in poor balance at high speed rotation.

b) Ball bearing 3 on the non-driving side to make the preload spring work effectively
The fit between the outer ring b and the housing 2b must be a loose fit, and due to this clearance and the residual unbalance, the radial movement of the non-driving side shaft end is in the μm unit, and the rotating shaft 4, that is, the polygon mirror 8 The rotational accuracy of the printer deteriorates, and the resolution of the printer device decreases.

C) The clearance in the outer ring causes creep and spin of the non-driving side ball bearing 3b. As is well known, if the spindle motor is even slightly unbalanced, the higher the speed, the more it becomes a so-called outer ring rotational load, which causes creep. Creep occurs when the outer ring rotates in the opposite direction to the rotation of the shaft, increasing the fitting clearance due to wear and increasing the creep, which worsens the situation in terms of acceleration.As long as there is clearance, increasing the preload will not prevent creep. is not very effective.

Spin is caused by inner ring rotation load or vibration load, and is caused by magnetic imbalance, vibration, bearing internal friction, etc., and may also occur in combination with creep, causing wear on the housing.

d) In order to prevent creep or spin, either 1) manage the fit clearance within a range that ensures axial movement of the outer ring of the non-driving side ball bearing 3b by the preload spring 11, or 2) increase the preload. After adding the outer ring to the housing 2b with adhesive
3) increase the preload force and use the resulting frictional force to stop movement in the circumferential direction.

d-1) Clearance control involves measuring the outer diameter of the outer ring and the inner diameter of the nozzing and selectively fitting them together, which complicates manufacturing process control.

d-2) Bonding the outer ring to the housing requires measuring the preload force during bonding, and during use, the temperature difference between the rotating shaft 4 and the bracket 1 including the housings 2a and 2b made of aluminum alloy. The preload force fluctuates due to the difference in coefficient of thermal expansion.

d-3) Excessive preload force has a negative effect on bearing loss and life.

e) Although it is surrounded by a yoke 6 and is of a sealed type, the higher the speed is, the more a small amount of bearing lubricant leaks and contaminates the polygon mirror. Even if a labyrinth gap is formed between the end face of the housing 2a and the yoke 6, the polygon mirror remains contaminated due to evaporation of the face of the stator 5. Even if the position of the printed circuit board 13 is changed to form a labyrinth between the outer periphery of the yoke 6 and the bracket l, a labyrinth with a large diameter is not effective.

f) If a dynamic pressure bearing is used instead of a rolling bearing, the risk of contamination by lubricant is eliminated, but a pressure source is required and contamination by faces remains.

The purpose of this invention is to (a) make it easy to maintain dynamic balance;
It is an object of the present invention to provide a polygon scanner motor in which the rotational accuracy of a rotating shaft is high, (c) creep or spin is prevented, and (2) contamination of a polygon mirror by grease or festivals is prevented.

[Means to solve the problem]

The means for solving the above problem are as follows.

1) A housing is provided on both end faces of the disc-shaped bracket to which the stator is attached, and a rotating shaft is supported by these housings via ball bearings, and a polygon mirror is mounted on the driving side end of this rotating shaft. In a polygon scanner motor with a fixed pedestal and an outer rotor attached to the shaft end on the non-driving side, the fit between the inner ring and the outer ring of the ball bearing on the driving side and the fit between the inner ring of the ball bearing on the non-driving side are fixed and fitted. A polygon scanner motor, wherein the outer ring of the ball bearing on the non-driving side is loosely fitted, and an axial preload spring and a radial lateral pressure spring are brought into contact with the outer ring of the ball bearing on the non-driving side.

This means relates to the above objectives a), g) and c).

2) A housing is provided on both end faces of the disc-shaped bracket to which the stator is attached, and a rotating shaft is supported by these housings via ball bearings, and a polygon mirror is mounted on the drive-side shaft end of this rotating shaft. In a polygon scanner motor with a fixed pedestal and an outer rotor attached to the shaft end on the non-driving side, the fit between the inner ring and the outer ring of the ball bearing on the driving side and the fit between the inner ring of the ball bearing on the non-driving side are fixed and fitted. The outer ring of the ball bearing on the non-driving side is fitted with a loose fit, and an axial preload spring and a radial lateral pressure spring are brought into contact with the outer ring of the ball bearing on the non-driving side to assemble the motor. later,. A method for manufacturing a polygon scanner motor, in which the motor is operated to finish the mirror mounting portion of the mounting base, and then dynamic balance is achieved.

This means relates to the above objectives a), g) and c).

3) A housing is provided on both end faces of the disc-shaped bracket to which the stator is attached, and a rotating shaft is supported by these housings via ball bearings. A polygon scanner motor in which a mounting pedestal is fixed and an outer rotor is attached to a non-driving side shaft end, wherein a shaft sealing device is formed between the driving side housing and the mounting pedestal.

4) In means 3, a magnetic fluid shaft sealing device is formed between the driving side housing and the rotating shaft instead of the shaft sealing device between the driving side housing and the mounting base.
Polygon scanner motor.

Said means 3 and 4 relate to the above objects a) and 2).

[Effect]

In method 1), the mounting base with large inertia and the outer rotor are distributed to both ends of the rotating shaft, ensuring dynamic balance.The outer ring of the ball bearing on the non-driving side is a loose fit, and the preload spring Since the force is applied in the direction, rolling elements (balls) are
Rolls against the raceway surfaces (inner ring, outer ring) with proper preload without any gaps. As a result, the center of rotation of the rotating shaft is determined for both bearings, improving rotation precision, eliminating vibration, and extending the life of the bearings. In particular, improving the rotation precision of the polygon mirror contributes to improving the resolution of the printer device.

Even though the outer ring of the ball bearing on the non-driving side is a loose fit, the lateral pressure spring presses the ball bearing in the radial direction and the position is fixed, so creep does not occur and rotation accuracy is further improved.

This action is related to the purposes of a), a), and c).

In method 2), in addition to the above-mentioned method 1), after completing the motor with improved rotational accuracy, the motor is driven by its own rotational force to finish the mirror mounting part of the mounting base, so that no external force can be used. There is no external force applied to the rotating body as in the case of driving, and finishing is performed under the same conditions as the operating state. Through this finishing process, slight deformation of the rotating shaft, etc. due to press fitting between the rotating shaft, rotor, and mounting seat, and accuracy errors of each component are completely corrected based on accurate rotational accuracy. After that, dynamic balance can be achieved on two fronts, and the balance becomes extremely good.

This action is related to the purposes of a), a), and c).

In means 3) or 4), the bearing lubricant is prevented from scattering by the shaft sealing device which also serves as the mounting base (in the case of means 4, especially by the magnetic fluid shaft sealing device), and the bearing lubricant is prevented from scattering from the face of the stator winding. The small amount of gas that evaporates is completely isolated on the anti-polygon mirror side. Therefore, the polygon mirror is not contaminated by lubricant or festival material, and the resolution of the printer device is ensured.

〔Example〕

FIG. 1 is a half-sectional view of the embodiment, and the same reference numerals as in FIG. 2 have approximately the same functions.

Note that this motor is basically a brushless DC motor.

Housings 22a and 22b in which bushings of ferrous metal are fitted are provided on both end faces of a bracket 21 made of a disc-shaped aluminum alloy to minimize the difference in thermal expansion. A rotating shaft 24 is supported.

Unlike the conventional example, the winding stator 5 is attached to the outer periphery of the housing 22b on the non-operating side, and is an outer rotor made of a permanent magnet supported by a yoke 26 attached to the shaft end on the non-operating side. 7 surrounds the stator 5 with a gap in between. On the other hand, a mounting pedestal 31 as an independent member for the polygon mirror 8 is attached directly to the rotating shaft 24 at the driving side shaft end.

A polygon mirror 8 having a regular octagonal mirror surface on its outer periphery is fixed to this mounting base 31 with washers 9 and bolts 10.

A shaft seal 232 such as a labyrinth is formed between the mounting base 31 and the driving side housing 22a.

For example, a magnetic fluid sealing device may be used as the shaft sealing device 32 instead of a labyrinth. The main points of the magnetic fluid sealing device are:
For example, this can be known from Utility Model Application No. 62-60217.

The surrounding structure of the ball bearings 3a and 3b will be explained.

The fit between the inner ring and the outer ring of the ball bearing 3a on the driving side and the fit between the inner ring of the ball bearing 3b on the non-driving side are a stop fit (including an interference fit) and are firmly fitted to the rotating shaft 24 or the housing 22a. However, the ball bearing 3b on the non-driving side and the housing 22b are fitted with a loose fit so that they can slide in the axial direction, and a preload spring 11 is installed to absorb the internal gap between the ball bearings 3a and 3b. There is. The fit of such a bearing and the structure and operation of the preload spring are approximately the same as those of the prior art example.

By the way, 22a was made into a housing by fitting the bushing.
As shown in the figure, axial grooves are provided on the inner and outer peripheries of the housing 22b on the non-operating side of the housing 22b, and a clip-shaped lateral pressure spring 33 is attached thereto. This lateral pressure spring 3
3 has a force that pushes the ball bearing 3b on the non-driving side in the radial direction. Therefore, despite the above-mentioned outer ring clearance spring, the outer ring is pressed against the radially opposite side of the housing 22b, and its radial position is fixed. That is, the rotating shaft 24
Improves rotational accuracy.

Since the fitting clearance is inherently minute, the portion where the outer ring and the housing 22b come into contact actually has some length in the circumferential direction. Therefore, even if the lateral pressure spring 33 pushes the outer ring at one point, the ball bearing 3b Although the position is stable, two or more side pressure springs may be arranged on the circumference if necessary. The force of the lateral pressure spring 33 must be within a range that does not deleteriously deform the roundness of the outer ring, and must be large enough to overcome the radial force due to unbalance or vibration of the rotating body. However, in this embodiment, even though it is used at high speed rotation, it is easy to balance the lateral pressure spring 3 as described separately.
There is no great difficulty in choosing the magnitude of the force of 3.

A soundproof cover 34 is attached to the non-driving side of the bracket 21 for contact protection against rotation of the yoke 26 and soundproofing, and a printed circuit board 13 provided with a hall element 13a is attached to the driving side.
is installed.

The characteristic points of this brushless DC motor manufacturing method will be explained. Bearings 3a, 3b and housings 22a, 2
2b is fitted without selective fitting or gluing, and the outer ring outer diameter and the housing inner diameter are assembled with a predetermined accuracy in any desired combination. The assembly of the lateral pressure spring 33 and the like is completed as a motor, and the motor is rotated by its own rotational force without the polygon mirror 8.

In this self-rotating state, the mirror mounting surface of the mounting base 31, that is, the cylindrical surface and the flange surface, is finished. This finishing process is performed on each component with sufficient precision, so the grinding allowance is extremely small. Rotating shaft 24
, minute errors in the ball bearings 3a, 3b, housings 22a, 22b, etc., and bends in the rotating shaft, etc. due to press fitting of the ball bearings and mounting pedestal 31, etc., are completely corrected by the finishing process.

Thereafter, dynamic balance is achieved between the two surfaces of the yoke 26 and the end surface of the mounting base 31.

If the finishing process is performed after the dynamic balance, the dynamic balance will be disrupted even if the grinding allowance due to the finishing process is small. The balance at such high speeds is so delicate. If this balance is poor, even if the rotational accuracy is ensured by the lateral pressure spring 33, the radial force due to balance and vibration will exceed the force of the lateral pressure spring 33, worsening the rotational accuracy, and amplifying the situation for the worse. Not only is this affected by the life of the bearing, but the rotational precision of the mirror surface of the polygon mirror 8 is poor after it is used up, and the resolution of the printer device is reduced. Note that the inner diameter of the washer 8 is also fitted to the rotating shaft 24 to maintain balance.

FIG. 3 is a half sectional view of a different embodiment, and those having the same reference numerals as the embodiment of FIG. 1 have approximately the same functions, except for the shaft sealing device on the driving side.

That is, while a labyrinth 32b is provided between the mounting base 31 and the driving side housing 22a, the driving side bearing 3
The above-described magnetic fluid sealing device 32a is also installed between the housing 22a and the rotating shaft 24 at a position outside a. It is preferable to attach it by gluing it to the hanging 22a.

With this structure, the amount of grease, which is a bearing lubricant, flowing out to the polygon mirror side is reduced to less than 500 particles per cubic foot (approximately 0.028nf) in terms of 0.5μm particles.
The number of labyrinths was significantly reduced compared to the 100,000 labyrinths alone, and it was demonstrated that the reflectance could be prevented from decreasing due to fogging of the polygon mirror.

〔Effect of the invention〕

This invention 1) is superior in that the mounting pedestal and the outer rotor are located on both sides of the rotating shaft to maintain dynamic balance, and that the center of rotation is fixed by the preload spring and the side pressure spring.

Since the rotational accuracy is perfectly fixed, the rotational accuracy of the polygon mirror is excellent even at high speed rotation, and the resolution of the printer device is significantly improved.

Invention 2), in addition to 1), is that the motor is rotated by its own rotational force rather than an external drive, the rotation accuracy of the motor is maintained even during finishing, and the polygon mirror of the mounting base is mounted with respect to this rotation center. Since the seat is finished, the rotation accuracy of the mounting seat, and thus the polygon mirror, is further improved, and the resolution is further improved.

Invention 3) or 4) is in the shaft sealing device (invention 4),
In particular, the magnetic fluid shaft sealing device) prevents the lubricant of the ball bearing from scattering without particularly increasing the axial length of the motor, and in particular prevents isolated stator face steam from contaminating the polygon mirror. There is an effect that there is no.

[Brief explanation of the drawing]

FIG. 1 is a half sectional view of an embodiment, FIG. 2 is a half sectional view of a conventional example, and FIG. 3 is a half sectional view of a different embodiment. 1.21...Bracket, 2a, 2b,
22a. 22b...Housing, 3a, 3b...Ball bearing, 6
゜26... Yoke, 6a... Mounting part, 13... Printed circuit board, 32... Shaft sealing device, 32a... Magnetic fluid sealing device, 32b... Labyrinth, 33... Lateral pressure spring .

Claims (1)

[Claims] 1) Housings are provided on both end faces of a disc-shaped bracket to which the stator is attached, and a rotating shaft is supported by these housings via ball bearings, and the driving side shaft end of the rotating shaft is supported by these housings via ball bearings. In a polygon scanner motor in which a mounting pedestal for a polygon mirror is fixed to the mount and an outer rotor is attached to the shaft end on the non-driving side, the fit between the inner ring and the outer ring of the ball bearing on the driving side, and the inner ring of the ball bearing on the non-driving side. The fit is a stop fit, the fit of the outer ring of the ball bearing on the non-driving side is a loose fit, and an axial preload spring and a radial lateral pressure spring are brought into contact with the outer ring of the ball bearing on the non-driving side. A polygon scanner motor characterized by: 2) A housing is provided on both end faces of the disc-shaped bracket to which the stator is attached, and a rotating shaft is supported by these housings via ball bearings, and a polygon mirror is mounted on the drive-side shaft end of this rotating shaft. In a polygon scanner motor with a fixed pedestal and an outer rotor attached to the shaft end on the non-driving side, the fit between the inner ring and the outer ring of the ball bearing on the driving side and the fit between the inner ring of the ball bearing on the non-driving side are fixed and fitted. The outer ring of the ball bearing on the non-driving side is fitted with a loose fit, and an axial preload spring and a radial lateral pressure spring are brought into contact with the outer ring of the ball bearing on the non-driving side to assemble the motor. A method for manufacturing a polygon scanner motor, characterized in that the motor is then operated to finish the mirror mounting portion of the mounting base, and then dynamic balance is achieved. 3) A housing is provided on both end faces of the disc-shaped bracket to which the stator is attached, and a rotating shaft is supported by these housings via ball bearings, and a polygon mirror is mounted on the driving side shaft end of this rotating shaft. A polygon scanner motor in which a base is fixed and an outer rotor is attached to a shaft end on a non-driving side, characterized in that a shaft sealing device is formed between the housing on the driving side and the mounting base. 4) In the polygon scanner motor according to claim 3, instead of the shaft sealing device between the driving side housing and the mounting base, a magnetic fluid shaft sealing device is provided between the driving side housing and the rotating shaft. A polygon scanner motor characterized by forming.