JP3218753B2 - Rotating polygon mirror drive - Google Patents

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 with a laser beam printer (hereinafter abbreviated as LBP) or the like.

[0002]

2. Description of the Related Art In recent years, with the spread of LBP, there has been a demand for a rotary polygon mirror driving device to be smaller, thinner and lower in cost. Under these circumstances, instead of the conventional bracket such as aluminum die casting, for example, an aluminum or brass sleeve is fixed to an iron substrate or the like, so that the thickness and the cost are reduced, but the rotation fluctuation (hereinafter, referred to as jitter). It is indispensable to maintain high-precision performance for noise, noise, and tilting of the rotating polygon mirror.

[0003] A conventional rotary polygon mirror driving device will be described below with reference to Figs.

(First Conventional Example) FIG. 2 shows a configuration of a first conventional rotary polygon mirror driving device. In FIG. 2, reference numeral 1 denotes a rotary shaft, and a rotary polygon mirror 2
The rotor boss 5 to which the rotor magnet 3 and the rotor yoke 4 are fixed is fixed to the rotating shaft 1 by shrink fitting or the like to form the rotor 13. The bracket 7 having the mounting surface 7a of the rotary polygon mirror driving device includes a bearing 10 for rotatably supporting the rotary shaft 1, a stator yoke 6 provided to face the rotor magnet 3, and forming a magnetic path. A stator substrate 9 to which a stator winding 8 for urging the rotor magnet 3 is fixed is fixed between the stator yoke 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, a bracket 14 is made of a magnetic material having a mounting surface 11a for a rotary polygon mirror driving device. It is composed of a base plate 11 and a collar 12 which is caulked to the base plate 11 and to which the bearing 10 is fixed. The base plate 11 faces the rotor magnet 3 to form a magnetic path.

The operation of the first and second rotary polygon mirror driving devices configured as described above will be described below. 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 rotation accuracy of the rotor 13 and the mechanical accuracy of the rotating shaft 1 with respect to the mounting surfaces 7a and 11a of the rotary polygon mirror driving device (hereinafter referred to as absolute tilting) are determined by the bearing 10 fixed to the bracket 7 or the collar 12. It is determined by the accuracy and the accuracy of machining the bracket 7 or fixing the collar 12 to the base plate 11, 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 has been made by cutting aluminum die casting or the like.

[0007]

However, in the above-mentioned conventional structure, (1) the thickness of the aluminum die-casting of the bracket 7 is small, and it is distorted by the influence of the chuck at the time of processing, so that the perpendicularity of the bearing 10 cannot be maintained. When caulking the collar 12 on the base plate 11, it is difficult to fix the collar 12 to the base plate at right angles due to distortion of the base plate 11. (2) The accuracy of the bearing 10 deteriorates due to the roundness of the bracket 7 or the portion of the collar 12 to which the bearing 10 is fixed. Further, since the linear expansion coefficient of aluminum is as large as 27 × 10 ⁻⁶ , the bearing 10 is tightened at a low temperature and the bearing 10
The inner diameter accuracy is deteriorated, and at a high temperature, the bearing 10 is loosely fixed. As a result, jitter and tilting are deteriorated. Similarly, play will occur at the caulked portion between the base plate 11 and the collar 12. (3) In particular, when the bearing 10 is a sleeve of a fluid bearing, since the bearing 10 is usually made of a soft material such as brass, the precision of the bearing inner diameter deteriorates remarkably, and in this case, the reliability is greatly affected. There was a problem that.

An object of the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide a low-cost, low-profile rotary polygon mirror driving device without deteriorating the accuracy of the bearing.

[0009]

To achieve this object, a rotary polygon mirror driving device according to the present invention comprises a rotor having a rotary shaft and a rotor magnet, and a rotary polygon mirror fixed to the rotor. A bracket comprising a base plate provided facing the rotor magnet and a collar which is a bearing holding portion made of a resin outsert on the base plate, wherein the collar has a thin wall on the rotor side. The first cylindrical portion and a second cylindrical portion having a thickness greater than that of the first cylindrical portion on the base plate side, and a bearing for supporting a rotary shaft is fitted and fixed to the first cylindrical portion of the collar. It has a configuration.

[0010]

With this configuration, the rigidity of the collar is 1/4 to 1/8 that of a metal such as aluminum because the collar is made of resin, and excellent rotational performance is achieved without impairing the accuracy of the bearing inserted into the collar. Can do it,
Since the base plate forms a magnetic path, the thickness can be reduced. In particular, by fitting and fixing the bearing to the first cylindrical portion (thin portion) of the collar, the outer diameter of the first cylindrical portion of the collar is considered in advance in consideration of the dimensional change in the outer diameter of the collar due to the fixed fitting of the bearing. By setting the dimensions, it is possible to minimize the influence of the bearing fitting and fixing on the bearing inner diameter.

When the bearing is a sleeve of a copper-based fluid bearing, its linear expansion coefficient is about 20 × 10 ⁻⁶ ,
Since the base plate can adjust the linear expansion coefficient of the color to a value between the two depending on the purpose by adjusting the content of glass fiber contained in the resin with respect to the iron plate of 12 × 10 ^-6 ,
From low to high temperatures, the effect of changing the precision of the collar on the sleeve and the holding force of the collar and the base plate can be reduced.

[0012]

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 1 denotes a rotating shaft, and a rotor boss 5 to which a rotating polygon mirror 2, a rotor magnet 3, and a rotor yoke 4 are fixed is fixed to the rotating shaft 1 by shrink fitting or the like, thereby forming a rotor 13. ing. The bracket 16 having the mounting surface 16a of the rotary polygon mirror driving device is composed of the rotor magnet 3 and a base plate 11 of a magnetic material constituting a magnetic path, and a collar 1 made of resin outsert molded on the base plate 11.
And a bearing 10 rotatably supporting the rotary shaft 1.
And a stator substrate 9 to which a stator winding 8 for urging the rotor magnet 3 is fixed between the base plate 11 and the rotor magnet 3. A herringbone groove for generating dynamic pressure is formed on either the rotating shaft 1 or the sleeve in the inner diameter of the bearing 10 to constitute a fluid bearing, and the rotating shaft 1 is rotatably supported.

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 absolute tilt of the rotary polygon mirror are determined by the accuracy of the bearing 10.

On the other hand, the collar 15 comprises a first cylindrical portion 15a formed thin on the rotor side and a second cylindrical portion 15b formed thicker on the base plate side than the first cylindrical portion 15a. 10 is the first cylindrical portion 15a (thin portion)
Press-fit and fixed. Here, if the rigidity of the collar 15 is, for example, PPS or the like, it is almost 1/4 to 1/8 that of aluminum.
Therefore, since the rigidity of the bearing 10 is lost by press-fitting into the thin first cylindrical portion 15a, a change in the inner diameter of the bearing 10 is suppressed to about 1/20 to 1/40 of the press-fitting allowance (press-fitting allowance). 20 μm, only 0.5
μm).

The base plate 11 is generally made by stamping a rolled steel plate with a press, and it is difficult to obtain accuracy because of the warpage in the material stage. Absorb the distortion,
The perpendicularity of the collar 15 to the base plate 11 can be maintained.

The bearing 10 is generally made by processing a copper-based material.
The accuracy can be maintained over a wide temperature range by setting the distance between the base and the base plate 11, and the accuracy is maintained by controlling the amount of glass fibers contained in the collar 15 since the collar 15 is a resin containing glass fibers. It is possible.

As described above, according to the present embodiment, the rotating shaft 1
A rotor 13 having a rotating polygon mirror 2 and a rotor magnet 3, a base plate 11 provided to face the rotor magnet 3, and a collar 15 of a bearing holding portion made of a resin outsert on the base plate. Bracket 16
In the above, the first cylindrical portion 15a formed of a thin wall on the rotor side of the collar 15 and the first cylindrical portion 15a on the base plate side.
a second cylindrical portion 15b, which is thicker than a, and has a configuration in which the bearing 10 that supports the rotating shaft 1 is fitted and fixed to the first cylindrical portion 15a of the collar 15, thereby achieving excellent rotation. It is possible to provide a rotary polygon mirror driving device having high precision and mechanical precision.

In this embodiment, the bearing 10 is a fluid bearing. However, even if the bearing 10 is made of metal, the effect is the same. In the case of a ball bearing, it is possible to further provide a vibration absorbing effect. Needless to say.

[0020]

As described above, the present invention comprises a rotor having a rotating shaft and a rotor magnet, and a rotating polygon mirror fixed to the rotor, and a base of a magnetic body which forms a magnetic path facing the rotor magnet. In a bracket comprising a plate and a bearing holding portion made of a resin outsert on the base plate, a first cylindrical portion made thin on the rotor side of the bearing holding portion and a first cylindrical portion on the base plate side. By providing a structure in which a second cylindrical portion made of a thick wall is provided, and a bearing for supporting a rotating shaft is fitted and fixed to the first cylindrical portion of the bearing holding portion, (1) the warp is formed on the base plate. Even if there is, the squareness of the rotating shaft can be maintained because the collar is formed on the basis thereof, and as a result, an absolute surface inclination with respect to the reference surface to which the rotary polygon mirror driving device is fixed can be secured. (2) The collar is made of resin, the rigidity of which is lower than that of the metal sleeve, and the coefficient of linear expansion thereof is made closer to that of the sleeve.
In addition, by fitting and fixing the sleeve to the thin portion of the collar, it is possible to assemble and maintain the sleeve with almost no change in the inner diameter accuracy. In particular, when the sleeve has a large change in the inner diameter of a fluid bearing or the like, which greatly affects the loss or rigidity, the effect is remarkable. (3) Rotor magnet and base plate and shaft constituting magnetic path
The joining of the collars, which is the receiving and holding portion, can be configured without using man-hours such as caulking, and cost can be reduced. Thus, an excellent rotary polygon mirror driving device can be realized.

[Brief description of the 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]

 REFERENCE SIGNS LIST 1 rotating shaft 2 rotating polygon mirror 3 rotor magnet 10 bearing 11 base plate 12, 15 collar 15a color thin portion (first cylindrical portion) 15b color thick portion (second cylindrical portion) 7, 14, 16 bracket 7a, 14a, 16a Mounting surface of rotary polygon mirror drive unit

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-188821 (JP, A) JP-A-3-107913 (JP, A) JP-A-62-27713 (JP, A) 78816 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) G02B 26/10

Claims (2)

(57) [Claims] A rotor having a rotating shaft and a rotor magnet; a rotating polygon mirror fixed to the rotor;
A base plate provided opposite to the rotor magnet and a bracket formed of a collar which is a bearing holding portion made of a resin outsert on the base plate, and the collar has a thin-walled structure on the rotor side. A first cylindrical portion and a second cylindrical portion that is thicker than the first cylindrical portion on the base plate side, and a bearing that supports the rotary shaft is fitted and fixed to the first cylindrical portion of the collar; The coefficient of linear expansion of the resin constituting the collar is equal to the coefficient of linear expansion of the sleeve of the bearing.
A rotary polygon mirror driving device between the linear expansion coefficient of the base plate and the base plate . 2. A laser beam printer equipped with the rotary polygon mirror driving device according to claim 1.