JPH06180431A - 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 and to realize the driving device at a low cost by solving the degradation in the rotating accuracy of the device, the accuracy of a sleeve and the dimensional change in the reference outside diameter part of a bracket. CONSTITUTION:This rotary polyhedral mirror driving device is constituted by forming a collar 15 of a resin by outsert molding on a base plate 12, fitting and fixing the sleeve 10 thereto and inserting a rotor shaft into the sleeve 10. The diameter of the fitting inner peripheral surface of the rotary polyhedral mirror of the collar 15 and the sleeve 10 on the opposite side is set partly larger than the diameter of the sleeve 10, by which a space is provided. The distortion, etc., of the reference outside diameter part 14b of the bracket which occurs in the deformation of the sleeve 10 by caulking of a thrust cover 17 are thus prevented.

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).

[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 a conventional bracket such as an aluminum die cast, for example, an aluminum or brass sleeve is 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 FIG. FIG. 2 shows the configuration 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. A sleeve 7 having a thrust bearing 11 fixed to one end surface thereof is fitted and fixed to a bracket 7 having a mounting surface 7a of the rotary polygon mirror driving device and cylindrical portions 7b and 7c, and is opposed to the rotor magnet 3. A stator yoke 6 that is provided to form a magnetic path and a stator substrate 9 to which a stator winding 8 that biases the rotor magnet 3 is fixed are fixed between the stator yoke 6 and the rotor magnet 3.

Further, the thrust bearing 11 is formed with a spiral groove for generating a dynamic pressure, and the sleeve 10 is formed with a herringbone groove for axially supporting the radial direction.

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, dynamic pressure is generated by the action of the grooves provided in the thrust bearing 11 and the sleeve 10, and the rotating shaft 1 floats and the rotor 13 rotates without contact.

[0006]

However, in the above-mentioned conventional configuration, when the sleeve 10 is fitted and fixed to the inner diameter of the bracket 7 or when the sleeve 10 is deformed by the caulking of the thrust bearing 11, the outer diameter portion of the bracket cylindrical portion 7b ( Less than,
There is a problem that the dimensional change of the bracket reference outer diameter portion 7d cannot be suppressed.

The present invention solves the above-mentioned problems of the prior art. A rotary polygon mirror drive that realizes a low cost and a thin shape without deteriorating the accuracy of the sleeve and eliminating the dimensional change of the reference outer diameter portion of the bracket. The purpose is to provide a device.

[0008]

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 magnet, and a rotary polygon mirror fixed to the rotor. A bracket having a base plate and a collar that is a bearing holding portion that is fitted and fixed to the base plate, and a sleeve that is fitted and fixed to support the rotary shaft. The rotor has a thin first cylinder portion and the base plate side has a second cylinder portion coaxial with the rotation axis, and the inner diameter of the second cylindrical portion of the collar is larger than the outer diameter of the sleeve. It has a larger structure.

[0009]

With this configuration, when the sleeve 10 is fitted and fixed to the inner diameter of the bracket 14 or when the sleeve 10 is deformed due to the caulking of the thrust cover 17, the dimensional change of the bracket reference outer diameter portion 14b can be suppressed.

[0010]

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 designates a rotary shaft having an R-shaped tip, a rotary polygon mirror 2, a rotor magnet 3, and a rotor yoke 4.
The rotor boss 5 to which are fixed is fixed by a method such as shrinkage fitting to form the rotor 13.

The bracket 14 having the mounting surface 14a of the rotary polygon mirror driving device includes a base plate 12 made of a magnetic material forming a magnetic path with the rotor magnet 3, and a collar 15 made of resin outsert-molded on the base plate 12. A sleeve 10 having a herringbone groove for rotatably supporting the rotating shaft and generating a dynamic pressure, and a base plate 12.
And a stator substrate 9 to which a stator winding 8 for urging the rotor magnet 3 is fixed.

A thrust plate 16 which is in contact with the R portion of the rotary shaft 1 and a thrust cover 17 for holding the thrust plate 16 are fixed to one end surface of the sleeve 10. In addition, the collar 15 has a thin first wall on the rotor 13 side.
Has a cylindrical portion 15c and a second cylindrical portion 15b coaxial with the rotating shaft 1 on the base plate 12 side, and the inner diameter of the second cylindrical portion 15b of the collar 15 is larger than the outer diameter of the sleeve 10. There is.

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, dynamic pressure is generated by the action of the groove provided in the sleeve 10, and the rotor 13 rotates in a radial direction without contact with the rotary shaft 1.

On the other hand, the rigidity of the collar 15 into which the sleeve 10 is press-fitted and fixed is, for example, PPS or the like, about 1/4 to 1/8 that of aluminum, so that the rigidity of the sleeve 10 is lost, so that the inner diameter of the sleeve 10 is reduced. Change the press-fitting fee 1
/ 20 to 1/40 can be suppressed (press-fitting margin is 20μ
If it is m, the change in diameter will be only about 0.5 μm).

Since the sleeve 10 is generally made of a copper-based material, the accuracy can be maintained in a wide temperature range by setting the coefficient of linear expansion of the collar 10 between the sleeve 10 and the base plate 11. However, since the collar 15 is a resin, it is possible to control 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 and a rotary polygon mirror 2 fixed to the rotor 13, and a base plate 12 facing the rotor magnet 3 and a resin outserted to the base plate 12. By providing the sleeve 10 which is fitted and fixed to the bracket 14 including the collar 15 which is the bearing holding portion to support the rotating shaft 1, the sleeve 10 has excellent rotation accuracy and mechanical accuracy, and the sleeve 10 is provided in the inner diameter of the collar 15. The thrust plate 16
It is possible to provide the rotary polygon mirror driving device in which the dimensional change of the bracket reference outer diameter portion 14b is suppressed by the deformation of the sleeve 10 due to the caulking of the thrust cover 17 for holding.

Although the sleeve 10 is a fluid bearing in the embodiment, it is needless to say that the same effect is obtained even when the sleeve 10 is an oil-impregnated metal.

[0019]

As described above, the present invention is provided with a rotor having an R-shaped rotating shaft having a tip and a magnet, and a rotary polygon mirror fixed to the rotor, and a base provided to face the rotor magnet. A sleeve that is fitted and fixed to a bracket that includes a plate and a collar that is a bearing holding portion made of resin that is outserted to the base plate and that supports the rotation shaft, and an R-shaped tip of the rotation shaft that is fixed to the sleeve. By providing the thrust plate that comes into contact with the portion, (1) even if there is a warp on the base plate, the collar is formed with reference to it, so it is possible to ensure absolute surface inclination. (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 sleeve 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. (4) When the sleeve is fitted and fixed to the inner diameter of the bracket or the sleeve is deformed due to the caulking of the thrust cover, the dimensional change of the reference outer diameter portion of the bracket can be suppressed. 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 conventional rotary polygon mirror driving device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 rotating shaft 2 rotating polygon mirror 3 rotor magnet 10 sleeve 11 thrust bearing 12 base plate 7,14 bracket 7d, 14b reference outer diameter part of bracket 15 color 15b color second cylinder part 15c color first cylinder part 16 thrust plate 17 Thrust cover

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Go Kano 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (4)

[Claims] 1. A base plate provided with a rotor having a rotary shaft and a magnet, and a rotary polygon mirror fixed to the rotor, the base plate facing the rotor magnet, and a bearing holder fitted and fixed to the base plate. And a sleeve for fitting and fixing the rotary shaft to a bracket made of a collar, which is a part of the collar, and the collar having a first cylindrical portion thin on the rotor side and a rotary shaft on the base plate side. A rotary polygon mirror driving device having a coaxial second cylindrical portion, wherein the inner diameter of the second cylindrical portion of the collar is larger than the outer diameter of the sleeve. 2. A rotary polygon mirror driving apparatus according to claim 1, wherein the sleeve is a dynamic pressure fluid sleeve having a herringbone groove for generating dynamic pressure on either the rotary shaft or the sleeve. 3. The sleeve is an oil-impregnated metal.
The rotating polygon mirror driving device described. 4. The rotary polygon mirror driving apparatus according to claim 1, wherein the base plate is made of a magnetic material and constitutes a magnetic path with a rotor magnet, and the collar is outsert-molded on the base plate.