JPH06180433A - Rotary polyhedral mirror driving device - Google Patents

Abstract

(57) [Summary] [Object] To solve the deterioration of the rotational accuracy and the accuracy of the bearing in the rotary polygon mirror driving device used for the LBP, and realize excellent rotational accuracy and thinning at low cost. [Structure] A rotor 13 having a rotary shaft 18 having an R-shaped tip, a rotor magnet 3, and a rotary polygon mirror 2 fixed to the rotor are provided, and a base plate 12 and a base plate provided to face the rotor magnet are provided. A sleeve 10 that is fitted and fixed to a bracket 14 that is a resin collar 15 that is an outsert bearing holding portion, and a thrust plate 16 that is fixed to the sleeve and that abuts the R-shaped tip of the rotation shaft. By providing the resin collar with a rigidity lower than that of the metal sleeve and a linear expansion coefficient closer to that of the sleeve, the inner diameter accuracy of the sleeve is hardly changed.
Can be maintained. Therefore, the whirling of the rotor is stable, an inexpensive pivot bearing can be used, and the cost can be significantly reduced.

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. However, rotation fluctuation (hereinafter referred to as jitter)
It is necessary to maintain high-precision performance with respect to noise, noise, and tilt of the polygon mirror. Under such circumstances, measures such as applying a hydrodynamic bearing to the bearing have been taken.

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 10 having a thrust bearing 11 fixed to one end surface of the cylindrical portion 7c is fitted and fixed to a bracket 7 having a mounting surface 7a of the rotary polygon mirror driving device and a cylindrical portion 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 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. At this time, the inner diameter accuracy of the sleeve 10 is deteriorated when the sleeve 10 is press-fitted and fixed to the bracket 7, and the rotor 1
Although the whirling of No. 3 is aggravated, the dynamic pressure of the thrust bearing 11 exerts a force for keeping the rotary shaft 1 vertical, so that the influence is minimized.

[0006]

However, in the above-mentioned conventional structure, (1) since the bracket 7 is made of metal such as aluminum die-cast, the sleeve is affected by processing accuracy such as roundness of the cylindrical portion 7c of the bracket 7. Since the inner diameter accuracy of 10 deteriorates and the rotation accuracy decreases, an expensive thrust bearing 11 is required to compensate for this. (2) Also, since the linear expansion coefficient of aluminum is as large as 27 × 10 ⁻⁶ , the bearing 10 is tightened at low temperature and the sleeve 10 is
The inner diameter accuracy of the sleeve deteriorates, and the sleeve 10 is loosened at a high temperature, resulting in deterioration of jitter and trouble.

In particular, since the sleeve 10 is usually made of a soft material such as brass, the accuracy of the inner diameter of the bearing is significantly deteriorated, which has a problem that the reliability is greatly adversely affected.

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 having a rounded tip and a magnet, and a rotary polygon mirror fixed to the rotor. A sleeve that is fitted and fixed to a bracket that includes a base plate that is provided to face the rotor magnet and a collar that is a bearing holding portion made of resin and is outserted to the base plate, and that supports the rotating shaft. The thrust plate is fixed to the sleeve and is in contact with the R-shaped tip of the rotary shaft.

[0010]

With this construction, the rigidity of the collar becomes 1/4 to 1/8 of that of metal, for example, aluminum, and the precision of the sleeve press-fitted into the collar is not impaired, and excellent rotation performance can be realized at low cost. At the same time, since the base plate constitutes a magnetic path, it can be made thin.

In particular, since the sleeve press-fitted into the collar is generally made of a copper-based metal, its linear expansion coefficient is about 20 × 10 ⁻⁶ , and the base plate is contained in the resin for the iron plate of 12 × 10 ^−6. By adjusting the glass fiber content, the linear expansion coefficient of the collar can be adjusted to a value between the two depending on the purpose, so the holding power of the collar and base plate from the low temperature to the high temperature and the accuracy change of the collar to the sleeve Can reduce the influence of. Therefore, the radial whirling is stable,
It is possible to use a thrust bearing which is inexpensive and has low loss, and which is a pivot bearing including a rotating shaft having a rounded tip shape and a thrust plate.

[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 18 is a rotary shaft having an R-shaped tip, 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. There is. The bracket 14 is composed of a base plate 12 made of a magnetic material that forms a magnetic path with the rotor magnet 3 and a collar 15 made of resin that is outsert-molded on the base plate 12, and rotatably supports a rotating shaft 18. A sleeve 10 having a herringbone groove for generating pressure and a stator substrate 9 to which a stator winding 8 for biasing the rotor magnet 3 is fixed are fixed between a base plate 12 and the rotor magnet 3.

A rotary shaft 18 is provided on one end surface of the sleeve 10.
The thrust plate 16 and the thrust plate 16 that are in contact with the tip R portion of the
The thrust cover 17 for holding is fixed.

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, a 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 18.

On the other hand, the rigidity of the collar 15 into which the sleeve 10 is press-fitted and fixed is, for example, 1/4 to 1/8 of that of aluminum in the case of PPS or the like, which is inferior to the rigidity of the sleeve 10. The change in inner diameter can be suppressed to about 1/20 to 1/40 of the press-fitting allowance (press-fitting allowance is 20
If it is μm, the diameter change is only about 0.5 μm).

Since the sleeve 10 is generally made of a copper-based material, the coefficient of linear expansion of the collar 15 is set between the sleeve 10 and the base plate 12 to maintain the accuracy in a wide temperature range. However, since the collar 15 is a resin, it is possible by controlling the amount of glass fiber contained therein. Therefore, the mechanical accuracy of the sleeve 10 is stabilized, the whirling of the rotor is improved, and the troubles and jitters are improved. Therefore, there is no problem even if an inexpensive and low loss pivot bearing is configured as the thrust bearing.

As described above, according to this embodiment, the tip is rounded.
A rotor 13 having a rotating shaft 18 and a magnet 3 and having a rotating polygonal mirror fixed thereto, a base plate 12 facing the rotor magnet 3, and a bearing made of resin outserted to the base plate 12. Color 15 which is a holding part
Is fixed to the bracket 14 composed of
And a thrust plate 16 that is fixed to the sleeve 10 and that abuts the R-shaped tip of the rotary shaft 18.
By providing the above, it is possible to provide an inexpensive and low-loss rotary polygon mirror driving device having excellent rotation accuracy and reliability.

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

[0020]

As described above, according to the present invention, a rotor having a rotary shaft having an R-shaped tip and a magnet to which a rotary polygon mirror is fixed, a base plate provided so as to face the rotor magnet, and this base. A sleeve, which is outserted to the plate, is made of a resin, which is a bearing holding portion made of resin, and is fixed to the bracket. The sleeve supports the rotary shaft, and the sleeve is fixed to the sleeve and abuts on the R-shaped tip of the rotary shaft. By providing the thrust plate, (1) 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, so that the inner diameter accuracy of the sleeve is hardly changed. Can be maintained. Therefore, since the whirling of the rotor is stable, an expensive dynamic pressure thrust bearing is not required for the thrust bearing, an inexpensive pivot bearing can be used, and a significant cost reduction can be achieved. Further, since the thrust bearing is in point contact, the loss can be reduced. (2) The collar can be molded without spending man-hours such as caulking, and it is possible to reduce the thickness and cost. 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]

 1,18 rotating shaft 2 rotating polygon mirror 3 rotor magnet 7,14 bracket 10 sleeve 11 thrust bearing 12 base plate 15 collar 16 thrust plate 17 thrust cover

Claims (5)

[Claims] 1. A rotor having an R-shaped rotating shaft having an R-shaped tip and a rotor magnet, to which a rotating polygon mirror is fixed, a base plate provided opposite to the rotor magnet, and outserted to the base plate. A sleeve that is fitted and fixed to a bracket that is a collar that is a bearing holding portion that is made of resin, and includes a sleeve that axially supports the rotating shaft, and a thrust plate that is fixed to the sleeve and that contacts the R-shaped tip of the rotating shaft. Rotating polygon mirror drive. 2. A rotary polygon mirror driving device according to claim 1, wherein a herringbone groove for generating a dynamic pressure is provided on either one of the rotary shaft or the sleeve to constitute a dynamic pressure fluid bearing. 3. The sleeve is an oil-impregnated metal.
The rotating polygon mirror driving device described. 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.