JPH06180435A - Rotary polyhedral mirror driving device - Google Patents

Abstract

PURPOSE:To obtain the excellent rotating accuracy and smaller thickness of the rotary polyhedral mirror driving device to be used for an LBP at a low cost by solving the degradation in the rotating accuracy of the device and the accuracy of a bearings. CONSTITUTION:A rotor boss 5 to be fixed with a rotary polyhedral mirror 2, a rotor magnet 3 and a rotor yoke 4 is fixed to a revolving shaft 1 by a method, such as shrinkage fitting, by which a rotor 13 is constituted. A bracket 16 is constituted of a liquid crystal display material base 11 which constitutes a magnetic path with the rotor magnet 3 and a resin collar 15 outsert molded to this base plate 11. The revolving shaft 1 is supported rotatably by the bearing 10, by which the absolute plane tilt is assured in spite of the presence of warpage in the base plate 11 as the collar 15 is molded on the basis of such warpage. The rigidity of the resin collar 15 is made lower than the rigidity of the metallic sleeve and the coefft. of linear expansion is approximated to the coefft. of linear expansion of the sleeve, by which the driving device is assembled and maintained with substantially no change in the bore accuracy of the sleeve. The effect thereof is particularly high if the change in the bore of the fluid bearing, etc., significantly affects the loss and rigidity of the sleeve.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary polygon mirror driving device used for laser scanning in a laser beam printer (hereinafter abbreviated as LBP) and the like.

[0002]

2. Description of the Related Art In recent years, with the spread of LBP, a rotary polygon mirror driving device is required to be smaller and thinner and to have a lower cost. Under such circumstances, instead of conventional brackets such as aluminum die castings, for example, aluminum or brass sleeves are fixed to an iron substrate or the like to achieve a thinner and lower cost.
However, it is necessary to maintain high-precision performance with respect to rotation fluctuation (hereinafter referred to as jitter), noise, or surface tilt of the rotating polygon mirror.

A conventional rotary polygon mirror driving device will be described below with reference to FIGS. (First Conventional Example) FIG. 2 shows a structure of a conventional rotary polygon mirror driving device. In FIG. 2, reference numeral 1 denotes a rotary shaft, and a rotor boss 5 to which a rotary polygon mirror 2, a rotor magnet 3 and a rotor yoke 4 are fixed is fixed by a method such as shrink fitting to constitute a rotor 13. The bracket 7 having the mounting surface 7a of the rotary polygon mirror driving device has a bearing 10a that rotatably supports a rotation shaft, a stator yoke 6 that faces the rotor magnet 3 and forms a magnetic path, and the stator yoke. A stator substrate 9 to which a stator winding 8 for biasing the rotor magnet 3 is fixed is fixed between 6 and the rotor magnet 3. (Second Conventional Example) FIG. 3 shows a second conventional example. In order to reduce the thickness and improve the strength, the bracket 14 is a base plate 11 which is a magnetic body having a mounting surface 11a for a rotary polygon mirror driving device. And a collar 12 to which the bearing 10a is fixed by being caulked to the base plate 11, and the base plate 11 faces the rotor magnet 3 to form a magnetic path.

The operation of the rotary polygon mirror driving device configured as described above will be described below. First, when current is supplied to the stator winding 8, the rotor magnet 3
An electromagnetic force is generated between the rotor and the rotor 13 to rotate. At this time, the rotational accuracy of the rotor 13 and the mechanical accuracy of the rotary shaft 1 with respect to the mounting surface of the rotary polygon mirror driving device (hereinafter referred to as absolute tilt) are the accuracy of the bracket 7 or the bearing 10 a fixed to the collar 12 and the bracket 7. Is determined or the accuracy of fixing the collar 12 to the base plate 11 is determined, which determines the accuracy of the dynamic characteristics of the rotary polygon mirror 2. In order to maintain their accuracy, the bracket 7 or the collar 12 was made by cutting aluminum die casting or the like.

[0005]

[Problems to be Solved by the Invention]
(1) The thickness of the aluminum die casting of the bracket 7 is thin.
Bearing 10a
Cannot maintain the squareness with respect to the mounting surface 7a. Also,
When crimping the collar 12 onto the base plate 11, the base plate 11
Fix the collar 12 at a right angle to the base plate 11 due to the distortion of
It is difficult to (2) The bearing 10a of the bracket 7 or the collar 12
The accuracy of the bearing 10a is poor due to the roundness of the fixed part.
Turn into. The coefficient of linear expansion of aluminum is 27 × 10. ^-6And large
Therefore, the bearing 10a is tightened at low temperature, and the bearing 10a
The inner diameter accuracy of a deteriorates, and at high temperatures, the bearing 10a cannot be fixed securely.
Resulting in jitter and annoying troubles.
Turn into.

Similarly, the caulking portion between the base plate 11 and the collar 12 also causes play.

Particularly, when the bearing 10a is a sleeve for a fluid bearing, it is usually made of a soft material such as brass, so that the accuracy of the inner diameter of the bearing is significantly deteriorated, and in this case, the reliability is greatly adversely affected. Had the problem.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a rotary polygon mirror driving device which realizes a thin structure at a low cost without deteriorating the accuracy of the bearing.

[0009]

In order to achieve this object, a rotary polygon mirror driving device of the present invention comprises a rotor having a rotary shaft and a rotor magnet, to which the rotary polygon mirror is fixed, and a rotor magnet facing the rotor magnet. A base plate provided on the base plate and a bracket made of a resin made outsert on the base plate to be fitted and fixed to the bracket, and the bearing supports the rotary shaft.

[0010]

With this structure, even if there is a warp on the base plate, by outserting the collar on the base plate, the perpendicularity of the collar can be maintained, and as a result, the absolute inclination can be secured. Further, since the collar is made of resin and its rigidity is 1/4 to 1/8 that of metal, for example, aluminum, the accuracy of the bearing inserted in the collar is not impaired, and excellent rotation performance can be realized and the base plate can be realized. Since it constitutes a magnetic path, it can be made thin.

Particularly when the bearing inserted in the collar is a sleeve of a copper-based fluid bearing, the linear expansion coefficient thereof is 20 × 1.
It is about 0 ^-6 , and the linear expansion coefficient of the color is a value between the two depending on the purpose by adjusting the content of the glass fiber contained in the resin with respect to the iron plate with the base plate of 12 × 10 ^-6. Since it can be adjusted to a low temperature, the holding force of the collar and the base plate and the influence of the accuracy change of the collar on the sleeve can be reduced from low temperature to high temperature.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 1 is a rotary shaft, and a rotary polygon mirror 2 is provided.
The rotor boss 5 to which the rotor magnet 3 and the rotor yoke 4 are fixed is fixed by a method such as shrink fitting, and the rotor 1
Make up three. Mounting surface 11a of rotary polygon mirror driving device
The bracket 16 having a base plate 11 made of a magnetic material that forms a magnetic path with the rotor magnet 3 and the base plate 1
1, a bearing 15b made of resin outsert-molded, which rotatably supports the rotating shaft,
Between the base plate 11 and the rotor magnet 3, a stator substrate 9 to which a stator winding 8 that biases the rotor magnet 3 is fixed is fixed. A herringbone groove is formed in the inner diameter of the bearing 10b to form a fluid bearing and rotatably support the rotating shaft 1.

The operation of the rotary polygon mirror driving device configured as described above will be described. First, when a current is supplied to the stator winding 8, an electromagnetic force is generated between the stator winding 8 and the rotor magnet 3, and the rotor 13 rotates. At this time, the jitter and the absolute tilt of the rotary polygon mirror are determined by the accuracy of the bearing 10b.

On the other hand, the rigidity of the collar 15 into which the bearing 10b is press-fitted and fixed is, for example, PPS or the like, about 1/4 to 1/8 that of aluminum. Change of inner diameter is 1/2 of press-fitting allowance
It is suppressed to about 0 to 1/40 (if the press-fitting margin is 20 μm, the diameter change is only about 0.5 μm). Also,
The base plate 11 is generally made by punching out a rolled steel plate with a press, and it is difficult to obtain accuracy because of the warpage at the material stage, but by outserting the collar 15 on this, it is possible to absorb those warps and distortions. The perpendicularity of the collar 15 with respect to the base plate 11 can be maintained.

Since the bearing 10b is generally made of a copper-based material, the coefficient of linear expansion of the collar 15 is set to the bearing 10.
The accuracy can be maintained in a wide temperature range by setting it between b and the base plate 11, but since the collar 15 is a resin, it is possible by controlling the amount of glass fiber contained therein.

As described above, according to this embodiment, the rotary shaft 1
A rotor 13 having a rotor magnet 3 to which the rotary polygon mirror 2 is fixed, a base plate 11 provided to face the rotor magnet 3, and a bearing holder made of resin outsert to the base plate 11. By providing the bearing 10b fitted and fixed to the bracket 14 including the collar 15 and pivotally supporting the rotary shaft 1, it is possible to provide a rotary polygon mirror driving device having excellent rotation accuracy and mechanical accuracy.

In the above embodiment, the bearing 10b is a hydrodynamic bearing, but the effect is the same even when the bearing 10b is a metal, and in the case of a ball bearing, a vibration absorbing effect can be further provided. Needless to say.

[0019]

As described above, according to the present invention, a rotor having a rotary shaft and a rotor magnet, to which a rotary polygon mirror is fixed, and a base plate which is a magnetic body facing the rotor magnet and forming a magnetic path. By providing a sleeve, which is fitted and fixed to a bracket including a bearing holding portion made of resin outserted on the base plate and supports the rotating shaft, (1) even if the base plate has a warp Since the collar is formed on the basis of, the perpendicularity of the rotary shaft can be maintained, and as a result, the absolute tilt of the rotary polygon mirror with respect to the reference plane to which this device is fixed can be secured. (2) Since the collar is made of resin and its rigidity is lower than that of a metal sleeve, and its linear expansion coefficient is brought close to that of the sleeve, the inner diameter accuracy of the sleeve can be assembled and maintained with almost no change. In particular, the effect is remarkable when the sleeve has a large change in the inner diameter such as a fluid bearing and affects the loss and the rigidity. (3) The collar can be molded without spending man-hours such as crimping, and the cost can be reduced. It is possible to realize an excellent rotary polygon mirror driving device.

[Brief description of drawings]

FIG. 1 is a sectional view of a rotary polygon mirror driving device according to an embodiment of the present invention.

FIG. 2 is a sectional view of a first conventional rotary polygon mirror driving device.

FIG. 3 is a sectional view of a second conventional rotary polygon mirror driving device.

[Explanation of symbols]

 1 rotating shaft 2 rotating polygon mirror 3 rotor magnet 7,14,16 bracket 7a, 11a mounting surface of rotating polygon mirror drive device 10a, 10b bearing 11 base plate 12,15 color

Claims (5)

[Claims] 1. A rotor having a rotating shaft and a rotor magnet, to which a rotating polygon mirror is fixed, a base plate provided to face the rotor magnet, and a bearing holder made of resin outsert to the base plate. A rotary polygon mirror driving device, comprising: a bearing that is fitted and fixed to a bracket that is formed of a collar that is a part and that supports the rotating shaft. 2. The rotary polygon mirror driving device according to claim 1, wherein the bearing is a hydrodynamic bearing having a herringbone groove for generating a dynamic pressure on either the rotary shaft or the sleeve. 3. The rotary polygon mirror driving device according to claim 1, wherein the bearing is an oil-impregnated metal. 4. The rotary polygon mirror driving device according to claim 1, wherein the base plate is made of a magnetic material and constitutes a rotor magnet and a magnetic path. 5. The linear expansion coefficient of the resin is 10 × 10 ^−6.
The rotary polygon mirror driving device according to claim 2, wherein the rotary polygon mirror driving device has a linear expansion coefficient of ˜25 × 10 ⁻⁶ and is between the linear expansion coefficient of the sleeve and the linear expansion coefficient of the base plate.