JP2964236B2 - Rotating polygon mirror motor and optical deflector provided with the motor - 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 motor comprising a rotary polygon mirror and a spindle motor for driving the rotary polygon mirror, and an optical deflecting device provided with the rotary polygon mirror motor.

[0002]

2. Description of the Related Art In a rotary polygon mirror motor used in a laser beam printer, as a holding means for attaching a rotary polygon mirror to a spindle motor, for example, Japanese Patent Laid-Open No. 6-22 / 1994
501 is disclosed. As shown in FIG. 10, this is a substantially circular shape having projections 70a of a number m (m = kn, where k is an integer of 1 or more) which is an integral multiple of the number n of mirrors of the rotating polygon mirror 30 (n is an integer of 4 or more). The rotary polygon mirror 30 is pressed and fixed in the axial direction with respect to the receiving member of the rotor of the spindle motor by the plate-shaped spring member 70. Reference numeral 80 denotes a housing, and 81 denotes a printed circuit board. And n =
5, m = 5, k = 1. When the rotary polygon mirror is attached to the spindle motor in this manner, the mirror surface of the rotary polygon mirror pressed at the m position is m according to the pressed position.
Although the distortion occurs at the location, since there is a relationship of m = kn with the number n of the mirror surfaces, each mirror surface is always distorted at the same phase (position), so that the scanning speed of the laser beam on each surface is geometrically the same. Due to the fluctuation, the scanning speed becomes almost the same and excellent jitter characteristics can be realized even at high speed rotation. As a result,
It enables high-speed and high-definition printing characteristics.

However, with the recent increase in speed and definition of laser beam printers, the distortion of the mirror surface of the rotary polygon mirror caused by the generation of slight radial stress of the holding means of the conventional rotary polygon mirror described above. Became a problem.
As shown in FIG. 11, the cause of this stress generation is that the holding means of the conventional rotary polygon mirror described above uses a substantially disk-shaped spring member 70 having radially extending projections to rotate the rotary polygon mirror 30 to receive the rotor of the spindle motor. Since the pressing portion is pressed and fixed to the member 90 in the axial direction, the holding portion is an upper surface of the rotating polygon mirror and a bottom surface on the receiving side of the rotating polygon mirror, that is, a surface in contact with the receiving member 90 of the rotor. This is because the structure is such that stress strain is generated from both sides with respect to 31. In particular, at the time of high-speed rotation, the stress strain A on the pressing spring side tends to be larger than the stress strain B on the bottom surface side, so that a slight but asymmetrical stress strain is applied to the mirror surface. For this reason, at the time of high-speed rotation, the flatness of the mirror surface 31 of the rotary polygon mirror 30 is reduced due to the slight but asymmetrical stress distortion given to the mirror surface. There is. FIG.
In FIG. 1, reference numeral 20 denotes a rotating shaft of a spindle motor, and 55 denotes an E for fixing the substantially disc-shaped spring member 70 to the rotating shaft 20.
It is a holding member such as a ring.

[0004]

An object of the present invention is to provide a rotary polygon mirror motor or an optical deflector provided with the rotary polygon mirror motor, wherein the rotary polygon mirror is attached to a spindle motor by a holding spring. In this case, the stress strain applied to the mirror surface of the rotary polygon mirror by the pressing force of the holding spring is made substantially uniform not only during low-speed rotation but also during high-speed rotation. Another problem to be solved is to make the stress in the radial direction applied to the mirror surface of the rotary polygon mirror by the holding spring substantially uniform. Still another object to be solved is to reduce the circumferential stress and strain applied to the mirror surface of the rotary polygon mirror by the holding spring member.

[0005]

In order to solve the above-mentioned problems, the present invention provides a rotor including a rotor magnet and having a cylindrical end for mounting a rotating polygon mirror, a stator including a stator coil, and rotating the rotor to a stator. A spindle motor consisting of a freely supporting bearing and a rotary polygon mirror attached to the spindle motor by fitting a cylindrical fitting hole formed along the central axis to a cylindrical end of the rotor. A retainer that constitutes a polygon mirror motor and is inserted over an entire circumference into an annular gap formed between an inner peripheral surface of a cylindrical fitting hole of the rotary polygon mirror and an outer peripheral surface of a cylindrical end of the rotor. The rotating polygon mirror was held and fixed to the rotor of the spindle motor by a holding spring having a spring portion. In order to prevent the spring member from coming off during high-speed rotation, the holding spring is constituted by a spring portion and a fixing disk portion covering the end surface of the cylindrical end of the rotor.

Further, the holding spring portion of the holding spring has an annular U-shaped spring structure having substantially the same shape as the inner peripheral surface of the cylindrical fitting hole of the rotary polygon mirror. Furthermore, the holding spring portion of the holding spring has an annular U-shaped spring structure having substantially the same shape as the inner peripheral surface of the cylindrical fitting hole of the rotary polygon mirror,
Making a first plurality of cuts from the free end of the holding spring portion,
During the first cut, a plurality of second cuts were formed, each of which did not reach the free end of the pressing spring portion and exceeded the U-shaped end.

[0007]

1 is a longitudinal sectional view of a part of an embodiment of the present invention in which a rotary polygon mirror is attached to a rotor of a spindle motor by an annular U-shaped leaf spring as a holding spring. 2 is a plan view, and FIG. 3 is a perspective view of a part of the annular U-shaped spring. In these drawings,
Although not shown, the spindle motor includes a cylindrical stator member forming a part of the stator and a cylindrical rotor member 20 forming a part of the rotor. Reference numeral 30 denotes a rotary polygon mirror, and reference numeral 40 denotes a holding spring for holding and fixing the rotary polygon mirror 30 to a rotor of a spindle motor, more specifically, to the rotor member 20.

The stator includes a stator coil (not shown) in addition to the stator member 10. The rotor includes a rotor magnet (not shown) in addition to the rotor member 20. The rotor is rotatably supported by the stator by a bearing (not shown). In the apparatus shown in FIG. 1, when the bearing is a dynamic pressure bearing, a flat inner peripheral surface of the cylindrical stator member 10 and a corresponding dynamic pressure generating groove of the cylindrical bearing portion 23 of the cylindrical rotor member 20 are formed. Radial dynamic pressure bearing with the outer peripheral surface
Further, a thrust dynamic pressure bearing portion can be constituted by the end surface of the cylindrical stator member 10 where the dynamic pressure generating groove is formed and the flat lower surface of the flange portion 22 of the cylindrical rotor member 20 facing the end surface.

The cylindrical rotor member 20 has a cylindrical end portion 21, a flange portion 22 having a larger diameter than the cylindrical end portion 21, and a cylindrical bearing portion 23 having a smaller diameter than the flange portion 22 in order from the upper end to the lower end. Is formed. The cylindrical end 21 fits into a fitting hole of the rotary polygon mirror 30, and the flange portion 22 also functions as a receiving portion of the rotary polygon mirror 30. The rotating polygon mirror 30 is a regular polygon, for example, a regular hexagonal polygon mirror having a plurality of mirror surfaces 31 formed on an outer peripheral surface, and a central portion thereof is fitted with the cylindrical end 21 of the cylindrical rotor member 20. A cylindrical fitting hole 33 is provided.

In order to attach the rotary polygon mirror 30 to the rotor of the spindle motor, a cylindrical fitting hole 33 is formed in the rotor member 2.
0, the cylindrical fitting hole 33 is inserted.
An annular gap is formed between the inner peripheral surface of the cylindrical end portion and the outer peripheral surface of the cylindrical end portion 21. An annular U-shaped holding spring portion 41 of the holding spring 40 is inserted into the annular gap, whereby the rotary polygon mirror 30 is connected to the rotor member 20 of the spindle motor.
To be fixed. That is, the annular U-shaped pressing spring portion 41 inserted into the annular gap formed between the inner peripheral surface of the cylindrical fitting hole 33 and the outer peripheral surface of the cylindrical end portion 21 and held by scissors has its The rotating polygon mirror 30 is uniformly pressed radially outward by the elastic force, and at the same time, the cylindrical end 21 is uniformly pressed radially inward, thereby rotating the rotating polygon mirror 30 to the rotor member 20 of the spindle motor. Hold firmly.

The holding spring 40 has a fixing disk portion 42. The fixing disk portion 42 is large enough to cover the end surface of the cylindrical end portion 21 of the rotor member 20, and has a mounting hole 43 formed in the center thereof. The holding spring 40 is fixed to the rotor member 20 by attaching means penetrating the attaching hole. A screw part 52 formed at the upper end of the fixed support 51, and a nut 5 screwed with the screw part 52
3 and the washer 54 constitute a mounting means for the fixing disk portion 42. Note that a retaining ring such as an E-ring may be used instead of screwing with the screw portion 52 and the nut 53.

As described above, the holding spring 40 includes the pressing spring portion 41 and the fixing disk portion 42. The holding spring portion 41 is basically an annular U-shaped leaf spring as described above. The annular U-shaped pressing spring portion 41 has a shape obtained by cutting a hollow donut body such as a round floating ring into two in the radial direction, and has a U-shaped cross section. 41
a, 41b and 41c are annular U-shaped pressing spring portions 4
1 are a free end, a fixed end and a U-shaped end, respectively.
The fixed end portion 41b of the holding spring portion 41 is a fixing disk portion 42.
Is actually fixed to the outer peripheral surface of the pressing spring portion 4.
The reference numeral 1 and the fixing disk portion 42 are formed by pressing a single spring material integrally.

A first cut 41 d and a second cut 41 are formed in the annular U-shaped pressing spring 41 of the holding spring 40.
e are formed at equal intervals over the entire circumference. That is, the first notch 41 d extends from the fixed end 41 b of the annular U-shaped holding spring 41 to the U-shaped end 41.
This is an elongated cut that passes through c and reaches the free end 41a. The annular U-shaped pressing spring portion 41 in which N first cuts 41d are formed has a structure in which N U-shaped leaf spring pieces are annularly arranged at equal intervals. The pressing spring portion 41 formed by providing the first notch 41d, that is, the pressing spring portion 41 having a structure in which N U-shaped leaf spring pieces are arranged in an annular shape, has a cylindrical fitting hole. 3
3 is a spring having extremely good adhesion to an annular gap formed between the inner peripheral surface of the cylindrical end portion 3 and the outer peripheral surface of the cylindrical end portion 21. It is also extremely effective in simultaneously reducing the rotational stress generated during high-speed rotation and the rotational distortion caused by thermal expansion.In other words, the rotation is performed to disperse and absorb the circumferential distortion caused by rotation. Circumferential stress strain applied to the polygon mirror can be reduced.

It is desirable that the number N of the first cuts 41d be sufficiently larger than the number M of faces of the rotating polygon mirror 30, or a number associated with the number M of faces of the rotating polygon mirror 30. In the latter case, the number N of the first cuts 41d may be larger or smaller than the number M of surfaces of the rotary polygon mirror 30 in some cases. If it is larger, that is, if N ≧ M, N is an integer multiple of M, and at least one of the first cuts 41 d is substantially coincident with the inter-mirror edge 32 of the rotating polygon mirror 30.
0 is attached to the rotor member 20 of the spindle motor. When N is smaller, that is, when N <M, N is a fractional multiple of M (、, ３, 等, etc.), and at least one of the first cuts 41 d is between the mirror surfaces of the rotary polygon mirror 30. The rotating polygon mirror 30 is attached to the rotor member 20 of the spindle motor so as to substantially coincide with the edge 32. With such a numerical relationship and an arrangement relationship, the distortion of the rotating polygon mirror 30 during high-speed rotation can be suppressed to a minimum.

The second cut 41e is formed between the first cuts 41d. The second cut 41e extends from the position not reaching the free end 41a of the U-shaped leaf spring piece to the U-shaped end 41c.
And an elongated notch extending to the fixed end 41b. By providing the second cuts 41e, radial asymmetry in circumferential distortion due to rotation is removed, almost eliminating circumferential stress distortion of the rotating polygon mirror, and more precise stress relaxation is performed. be able to. Second cut 41
If e is provided on all of the U-shaped leaf spring pieces, the number e becomes N, which is the same as the number of the first cuts 41d, but may be smaller than this. For example, second cuts 41e may be provided every other U-shaped leaf spring piece.

As a material for forming the holding spring 40, a general metal spring material or a polymer material having a large elastic constant is used. General metal spring materials include spring steel sheets, carbon steel sheets, low alloy steel sheets such as CrV steel, stainless steel sheets,
Examples include beryllium steel sheets, phosphor bronze sheets, nickel silver sheets, and brass sheets.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A vertical sectional view of a part of a second to fourth embodiment of the present invention in which a rotary polygon mirror is attached to a rotor of a spindle motor by a holding spring 40 which is an annular U-shaped leaf spring. 4 to 6 respectively. In these embodiment devices, the annular U-shaped holding spring portion 4 of the holding spring 40 is provided.
The spring receiver of the first free end 41a is devised. That is, what is shown in FIG. 4 is that a free end portion 41a of an annular U-shaped holding spring portion 41 is attached to a spring support 34 which is a small notch provided at an upper end edge of a cylindrical fitting hole 33 of the rotary polygon mirror 30. The bent portion 44 provided in the above is engaged. FIG. 5 shows a small annular V-shaped spring retaining groove 35 instead of a notch.
The one shown in FIG. 4 has the effect of improving the positioning accuracy of the free end 41a of the holding spring 41, which is an annular U-shaped spring. The one shown in FIG. 5 has an effect of preventing the spring from falling off during high-speed rotation, in addition to the above-described effect.

FIG. 6 shows the annular U shown in FIG.
The extension portion 45 of the free end portion 41a of the V-shaped holding spring portion 41 is strongly bent outward by 90 degrees so as to be in contact with the upper surface of the rotary polygon mirror 30, thereby preventing the spring from being pulled upward during high-speed rotation. This is an effect.

FIG. 3 shows the first embodiment of the holding spring 40 comprising the annular U-shaped pressing spring portion 41 and the fixing disk portion 42. The second embodiment and the third embodiment are shown in FIG. These are shown in FIGS. 7 and 8, respectively. In the second embodiment shown in FIG. 7, only the first cut 41d is provided. The third embodiment shown in FIG. 8 has a shape in which a hollow donut body such as a round floating ring is cut into two in the radial direction, and its cross-sectional shape is a U-shaped holding member. The spring 40 has a cylindrical side surface having the same diameter as the cylindrical fitting hole 33 on the surface where the outside of the holding spring portion contacts the inner surface of the rotary polygon mirror 30, that is, the inner surface of the cylindrical fitting hole 33. . Therefore, in the rotary polygon mirror motor in which the rotary polygon mirror 30 is attached to the spindle motor using the holding spring 40 of the third embodiment shown in FIG. 8 or the optical deflector provided with this motor, the rotary polygon mirror 3 is used.
Since the zero and the pressing spring 41 are in uniform contact, the distortion of the rotating polygon mirror can be reduced even during high-speed rotation.
Therefore, a laser printer using the above-described light deflecting device can print a higher definition image at high speed.

Without the fixing disk portion 42, an annular U
Holding spring 4 composed only of a V-shaped pressing spring portion 41
0 is a rotation speed that is not so high, for example, 30,00
The present invention can be used for a rotary polygon mirror motor having a rotation speed that does not reach about 0 rpm. The holding spring 40 composed of only the annular U-shaped pressing spring portion 41 is, for example, such that the fixing disk portion 42 is removed from the holding spring 40 shown in FIG. 3, FIG. 7, or FIG. Therefore, both the end contacting the inner peripheral surface of the cylindrical fitting hole 33 and the end contacting the outer peripheral surface of the cylindrical end 21 are free ends. An annular gap formed between the inner peripheral surface of the cylindrical fitting hole 33 and the outer peripheral surface of the cylindrical end portion 21 by holding the retaining spring 40 having only the annular U-shaped pressing spring having no fixing disk portion. When it is inserted over the entire circumference, both the free end in contact with the inner peripheral surface of the cylindrical fitting hole 33 and the free end in contact with the outer peripheral surface of the cylindrical end 21 have an annular V shape as shown in FIG. It engages with a U-shaped spring retaining groove, thereby positioning and stopping the free end of the spring. The holding spring 40 having only the annular U-shaped pressing spring having no fixing disk portion can be easily manufactured by pressing a plate material of a general spring material.

Both the holding spring 40 consisting of the annular U-shaped holding spring portion 41 and the fixing disk portion 42 and the holding spring 40 consisting of only the annular U-shaped holding spring portion 41 are axially and circularly shaped. It is desirable to perform positioning in the circumferential direction. As a means for performing this, as shown in FIGS. 6 to 8, for example, a small recess 24 is formed on the outer peripheral surface of the cylindrical end portion 21 and a small projection 46 engaging with the recess is formed on the holding spring 40.

FIG. 9 shows an example of a light deflecting device including a rotary polygon mirror motor and an optical system according to the present invention. In FIG. 9, the rotary polygon mirror motor is composed of a spindle motor SM and a rotary polygon mirror 30, and the optical system is a laser light source 61,
It is composed of imaging lenses 62 and 63 and a reflection mirror 64. DM is a photosensitive drum.

[0022]

According to the present invention, there is provided a rotary polygon mirror motor or an optical deflecting device provided with the rotary polygon mirror motor, wherein an inner peripheral surface of a cylindrical fitting hole of the rotary polygon mirror and a cylindrical shape provided on a rotor of the spindle motor. The rotary polygon mirror was held and fixed to the rotor of the spindle motor by a holding spring having a holding spring portion of an annular U-shaped leaf spring inserted over the entire circumference into an annular gap formed between the outer peripheral surfaces of the ends. Therefore, the radial stress generated on the mirror surface of the rotary polygon mirror can be made uniform to reduce the circumferential stress. Therefore, a laser beam printer using an optical deflector equipped with this rotary polygon mirror motor can realize higher-speed and higher-definition printing than ever before. Further, it has become possible to provide not only a laser beam printer but also various measuring devices, drawing devices, display devices, and the like to which a precision laser scanning system is applied. The holding spring 40 can be made in a large amount from a plate material of a general spring material such as a spring steel plate or a carbon plate by a simple method such as pressing. Also, the assembly when the rotary polygon mirror is held and fixed to the rotor of the spindle motor is easy. For this reason, a low-cost rotary polygon mirror motor or optical deflection device could be realized.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a part of an apparatus according to an embodiment of the present invention in which a rotary polygon mirror is attached to a rotor of a spindle motor by an annular U-shaped spring.

FIG. 2 is a plan view of a part of the apparatus according to the embodiment of the present invention shown in FIG.

FIG. 3 is a perspective view of a part of the annular U-shaped spring shown in FIGS. 1 and 2;

FIG. 4 is a longitudinal sectional view of a part of a device according to a second embodiment of the present invention in which a rotary polygon mirror is attached to a rotor of a spindle motor by an annular U-shaped spring.

FIG. 5 is a longitudinal sectional view of a part of a device according to a third embodiment of the present invention in which a rotary polygon mirror is attached to a rotor of a spindle motor by an annular U-shaped spring.

FIG. 6 is a longitudinal sectional view of a part of a device according to a fourth embodiment of the present invention in which a rotary polygon mirror is attached to a rotor of a spindle motor by an annular U-shaped spring.

FIG. 7 is a partial perspective view of another embodiment of an annular U-shaped spring.

FIG. 8 is a perspective view of a part of still another embodiment of the annular U-shaped spring.

FIG. 9 is a schematic diagram of an optical deflector provided with a rotary polygon mirror motor.

FIG. 10 is a plan view of a conventional rotary polygon mirror motor.

FIG. 11 is a view for explaining distortion generated when a rotary polygon mirror is attached to a rotor of a spindle motor in a conventional rotary polygon mirror motor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Stator member 20 Rotor member 21 Cylindrical end part 22 Flange part 23 Cylindrical bearing part 24 Small dent 30 Rotating polygon mirror 31 Mirror surface 32 Inter-mirror edge 33 Cylindrical fitting hole 40 Holding spring 41 Holding spring part of holding spring 41a Free end portion of the pressing spring portion 41b Fixed end portion of the pressing spring portion 41c U-shaped end portion of the pressing spring portion 41d First cut provided in the pressing spring portion 41e Second cut provided in the pressing spring portion 42 Fixing disk portion of holding spring 43 Mounting hole 44 Bending portion of holding spring 45 Extension portion of holding spring 46 Small projection 51 Fixed support 52 Screw 53 Nut 54 Washer

Continued on the front page (72) Inventor Katsuhiko Yahagi 4-3-1, Yashiki, Narashino-shi, Chiba Inside Seiko Instruments Inc. (72) Inventor Kimio Omata 4-3-1, Yashiki, Narashino-shi, Chiba Seiko Instruments Inc. In-company (72) Inventor Takashi Ishida 4-3-1 Yashiki, Narashino-shi, Chiba Seiko Instruments Inc. (56) References JP-A-8-234130 (JP, A) JP-A-9-197326 (JP) , A) (58) Field surveyed (Int. Cl. ⁶ , DB name) G02B 26/10 102 B41J 2/44 H02K 7/14

Claims (6)

(57) [Claims] A spindle motor comprising: a stator; a rotor having a cylindrical end for mounting a rotating polygon mirror; and a bearing rotatably supporting the motor on the stator.
A rotary polygon mirror motor comprising: a rotary polygon mirror attached to a spindle motor by fitting a cylindrical fitting hole formed along a central axis to a cylindrical end of the rotor; Rotation by a holding spring having an annular U-shaped pressing spring portion inserted over the entire circumference into an annular gap formed between the inner peripheral surface of the cylindrical fitting hole and the cylindrical end of the rotor. A rotary polygon mirror motor, wherein a polygon mirror is held and fixed to a rotor of a spindle motor. 2. The holding spring according to claim 1, wherein said holding spring comprises an annular U-shaped pressing spring portion and a fixing disk portion which covers an end surface of a cylindrical end portion of said rotor. 1 rotating polygon mirror motor. 3. The holding spring is an annular U-shaped spring whose annular U-shaped pressing spring portion has substantially the same shape as the inner peripheral surface of a cylindrical fitting hole of the rotary polygon mirror. The rotary polygon mirror motor according to claim 1. 4. The holding spring is an annular U-shaped spring whose annular U-shaped pressing spring portion has substantially the same shape as the inner peripheral surface of a cylindrical fitting hole of the rotary polygon mirror. The rotary polygon mirror motor according to claim 1, wherein a plurality of cuts are formed from a free end of the U-shaped pressing spring portion. 5. The holding spring is an annular U-shaped spring whose annular U-shaped pressing spring portion has substantially the same shape as the inner peripheral surface of a cylindrical fitting hole of the rotary polygon mirror. A plurality of first cuts are formed from the free end of the U-shaped presser spring portion, and the U-shaped press-down spring portion does not reach the free end of the annular U-shaped presser spring portion during the first cut. The rotary polygon mirror motor according to claim 1, wherein a plurality of second cuts extending beyond the end are formed. 6. An optical deflecting device comprising the rotary polygon mirror motor according to claim 1.