JP2005070246A - Laser scanning unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser scanning unit capable of reducing resonance while keeping cost low for the housing that constitutes the external form. <P>SOLUTION: The housing 1 containing a laser light source, polygon mirror, polygon motor, reflection mirror, etc., is mounted integrally with an image forming device by the first mounting parts 10 which are formed near the middle between the front and the rear of the left and right both side walls 5, 6 and by the second mounting parts 11 which are formed near the rear end wall 4. In the middle between the front and the rear of the left and right both side walls 5, 6 which are near the first mounting parts 10, a plurality of side wall through holes 20 are drilled to be adjacent longitudinally, with side wall ribs 21 defined by the part remaining between each side wall through hole 20. The vibration of the housing 1 caused by the rotation of the polygon motor is attenuated through a kind of damper function exerted by the side wall ribs 21. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a laser scanning unit that is mounted inside an image forming apparatus such as a copying machine or a printer and exposes an image carrier such as a photosensitive drum with a laser beam.

  A conventional general laser scanning unit has an outer shape formed by a box, and this box is formed by injection molding from a resin material. Inside this box, there are roughly a laser light source that emits laser light based on a predetermined image signal, a polygon mirror that reflects the laser light from the laser light source while rotating, and a polygon that rotates the polygon mirror. A motor and a reflecting mirror that reflects the laser beam reflected by the polygon mirror toward the exit port; The laser beam from the emission port is exposed while scanning the image carrier disposed in the image forming apparatus, thereby forming a predetermined electrostatic latent image on the image carrier.

  Specifically, as shown in FIG. 10, the box 1 has a bottom wall 2, a front end wall 3, a rear end wall 4, a right side wall 5, and a left side wall 6, and is a polygon mirror (not shown). A polygon motor (not shown) coupled to the main shaft is fastened to the four screws holes 7 formed on the rear end side of the bottom wall 2 with bolts or the like and fixed on the bottom wall 2. On the front end side of the bottom wall 2, a laser beam exit 8 is formed between the left and right side walls 5, 6. Above the exit 8, a reflection mirror (not shown) is provided in the box. Both ends are supported and fixed to a pair of left and right support portions 9 integrally molded with 1.

  Further, a pair of left and right first mounting portions 10 that protrudes inward and is integrally formed with the box body 1 are formed in the vicinity of the front and rear intermediate portions of the left and right side walls 5 and 6, and in the vicinity of the rear end wall 4. Is formed with a pair of left and right second mounting portions 11 that protrudes rearward and is integrally formed with the box body 1, and the box body 1 is formed with first through holes formed on the bottom surface of each first mounting portion 10. 12 and a second through-hole 13 formed on the bottom surface of each second attachment portion 11 and are integrally attached to an image forming apparatus main body (not shown) with a bolt or the like. As described above, the reason why the mounting position (first mounting portion 10) of the box 1 with respect to the image forming apparatus main body is in the vicinity of the front and rear intermediate portions of the left and right side walls 5 and 6 is that the space for installing the developing device is limited. Is what comes.

  It should be noted that an fθ lens (not shown) is supported at both ends of the front surface of each first mounting portion 10 and fixed between them. The fθ lens functions to convert the laser beam from the polygon mirror to a constant speed in the scanning direction and to correct the tilt of the reflecting surface caused by the rotation of the polygon mirror, that is, the tilt of the laser beam. Further, a laser light source (not shown), a cylindrical lens for condensing laser light from the laser light source and guiding it to a polygon mirror, etc. are fixed on the rear end side of the bottom wall 2 and in the vicinity of the right side wall 5. The

  By the way, in such a laser scanning unit, the box body 1 is vibrated with the rotation of the polygon motor, and the overhang portion A on the front end side from the first mounting portion 10 resonates inadvertently in the vertical direction. End up. This is because stress concentration occurs in the vicinity of the first mounting portion 10 that becomes the base of the overhang portion A during the rotational driving of the polygon motor. Then, as the overhanging portion A resonates, the fixed reflecting mirror vibrates more than expected in the vicinity of the front end wall 3, so that the laser beam is blurred, and as a result, image degradation such as image jitter is induced. .

Conventionally, the resonance of the overhang portion A has been reduced by mixing a substance having a damping function with respect to vibrations or mixing bubbles in the box 1 itself to solve such a problem ( For example, see Patent Document 1).
JP 2001-353743 A

  However, in the above-described conventional method, when molding the box 1, a special molding device is usually required, which is not enough for a general molding device, and management of special molding conditions is necessary for mixing of a function-damping substance and generation of bubbles. Is required. As a result, the manufacturing cost of the box 1 is significantly increased, which is extremely disadvantageous from the viewpoint of cost reduction.

  Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide a laser scanning unit capable of reducing resonance while suppressing the cost of a box constituting the outer shape.

  To achieve the above object, the present invention provides a laser light source, a polygon mirror that reflects the laser light from the laser light source while rotating, and a polygon motor that rotationally drives the polygon mirror. And a reflecting mirror that reflects the laser beam reflected by the polygon mirror toward the exit, and the polygon motor is mounted on the bottom wall on the rear end side of the box. The reflection mirror is fixed between both side walls on the front end side of the box body, and on both side walls of the box body, the stress concentration portion during the rotational drive of the polygon motor is Side wall ribs formed with a plurality of side wall through holes are provided.

  As a result, the vibration of the box body caused by the rotation of the polygon motor is attenuated by the side wall ribs exhibiting a kind of damper function, and as a result, the resonance of the box body is reduced. Moreover, in forming the side wall ribs, it is sufficient to simply form the side wall through holes, so that a normal molding apparatus is usually sufficient. As a result, the manufacturing cost of the box can be suppressed.

  Here, the box body is integrally attached to the image forming apparatus with a first attachment portion formed in the vicinity of the front and rear intermediate portions of the side walls and a second attachment portion formed in the vicinity of the rear end wall. The side wall rib is provided in the vicinity of the first mounting portion. As a result, the vibration of the box body caused by the rotation of the polygon motor is attenuated by the side wall ribs, and the vertical resonance in the overhang portion on the front end side from the first attachment portion is reduced.

  Furthermore, it is preferable that the said side wall rib inclines with respect to the bottom wall of the said box from a viewpoint of attenuating a vibration effectively. From the same viewpoint, it is preferable that an attenuation material having a higher attenuation rate than the material of the box is loaded in the side wall through hole. Further, from the same viewpoint, it is preferable that a plurality of bottom wall ribs are provided on the bottom wall of the box.

  According to the laser scanning unit of the present invention, the vibration of the box that occurs with the rotation of the polygon motor is attenuated by the side wall ribs exhibiting a kind of damper function, and as a result, the resonance of the box can be reduced. Therefore, the fixed reflecting mirror does not vibrate more than expected on the front end side of the box, and image deterioration such as image jitter can be suppressed. Moreover, in forming the side wall ribs, it is sufficient to simply form the side wall through-holes. Therefore, a general molding apparatus is usually sufficient, and as a result, an increase in the manufacturing cost of the box can be suppressed.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. First, the laser scanning unit which is 1st Embodiment of this invention is demonstrated. FIG. 1 is a perspective view of a box constituting the outer shape of the laser scanning unit of the first embodiment, and FIG. 2 is a side view showing the main part of the box. In the figure, parts having the same names and performing the same functions as those in FIG. 10 are denoted by the same reference numerals, and redundant description will be omitted as appropriate. The same applies to the second and third embodiments described later.

  As shown in FIGS. 1 and 2, the laser scanning unit of the present embodiment has an outer shape of a box 1, which is made of PC (polycarbonate) or ABS (acrylonitrile / butadiene / styrene copolymer). ) And other resin materials. A first attachment portion 10 for attaching the box body 1 to the image forming apparatus main body is mainly formed in the vicinity of the front and rear intermediate portions of the left and right side walls 5 and 6 in the box body 1. A plurality of side wall through holes 20 that are adjacent in the front-rear direction are formed in the front-rear intermediate part of the right side wall 5 that is in the vicinity of the attachment part 10. In the present embodiment, these side wall through holes 20 are triangles having short sides along the front-rear direction of the right side wall 5 and are alternately arranged.

  And the side wall rib 21 is defined in the part which remained between each side wall through-hole 20 mutually. In the present embodiment, these side wall ribs 21 are alternately inclined forward and upward with respect to the front-rear direction of the right side wall 5, that is, the bottom wall 2, and those inclined forward and downward. Will be placed. On the other hand, a side wall through hole 20 is similarly formed in the middle portion of the left side wall 6, which is also in the vicinity of the first mounting portion 10, and a side wall rib 21 is defined.

  According to the laser scanning unit having the box 1 configured as described above, the front and rear middles of the left and right side walls 5 and 6, which are in the vicinity of the first mounting portion 10 that is the base of the overhang portion A, during the rotational driving of the polygon motor. It appears that stress concentration occurs in the parts, but the vibrations of the box 1 caused by the rotation of the polygon motor are damped by the side wall ribs 21 provided in the front and rear intermediate parts exhibiting a kind of damper function. Is done. As a result, the vertical resonance in the overhang portion A on the front end side from the first mounting portion 10 can be reduced. Accordingly, the reflecting mirror fixed to the front end side of the box 1, that is, the overhang portion A does not vibrate more than expected, and image degradation such as image jitter can be suppressed.

  Further, in forming the side wall rib 21, it is sufficient to simply form the side wall through-hole 20, so that a general molding apparatus is usually sufficient without using a special molding apparatus. Increase in cost can be suppressed.

  In addition, the shape of the side wall through hole 20 is a triangle in this embodiment. This is because the side wall ribs 1 are formed obliquely with respect to the direction in which the vibration generated with the rotation of the polygon motor is transmitted, that is, the direction from the rear end wall 4 toward the front end wall 3. On the other hand, if the side wall rib 21 is perpendicular to the direction in which the vibration is transmitted, the damping effect of the vibration is inferior as a result of examination (vibration analysis) of the present inventor. However, it may be a parallelogram or a right triangle as will be described later.

  Next, FIG. 3 shows the vibration analysis result of such a laser scanning unit. FIG. 3 is a graph showing the vibration state of the box 1 during the rotational driving of the polygon motor. The horizontal axis is time (unit: second), and the vertical axis is displacement of the front end wall 3 of the box 1 (unit: mm). ). In addition, a thick line shows the vibration state of this embodiment, and a thin line shows the conventional vibration state for comparison. Conventionally, the maximum peak of vibration, that is, the maximum value of displacement is 0.0051 mm, whereas in this embodiment, the maximum value of displacement is about 0.0044 mm, and the vibration in the box 1 is clearly damped. Yes.

  Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 4 is a side view showing the main part of the box constituting the outer shape of the laser scanning unit of the second embodiment. The feature of the second embodiment is that the vibration is more effectively attenuated than the first embodiment.

  In the present embodiment, as shown in FIG. 4, in addition to the configuration of the first embodiment described above, the side wall through hole 20 that defines the side wall rib 21 has an attenuation that is higher than the material of the box 1. The material 22 is loaded. For example, rubber is applied as the damping material 22.

  According to such a configuration, the vibration of the box 1 generated with the rotation of the polygon motor is more effectively damped by the damping material 2 exhibiting a kind of damper function in addition to the side wall rib 21. .

  Next, FIG. 5 shows the vibration analysis result of such a laser scanning unit. FIG. 5 is a graph showing the vibration state of the box 1 during the rotational driving of the polygon motor, as in FIG. In the present embodiment (see the thick line in FIG. 5), the vibration in the box 1 is more effectively attenuated because the vibration has shifted to a lower frequency than in the past (see the thin line in FIG. 5). It will be.

  Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 6 is a perspective view of a box constituting the outer shape of the laser scanning unit of the third embodiment. The feature of the third embodiment is that vibration is more effectively attenuated than the second embodiment.

  In the present embodiment, as shown in FIG. 6, in addition to the configuration of the second embodiment described above, on the bottom wall 2, diagonal lattice-shaped bottom wall ribs 31 are formed in the front and rear intermediate portions. These diagonal grid-like bottom wall ribs 31 efficiently reduce the vibration of the polygon motor transmitted in the direction from the rear end wall 4 to the front end wall 3 in the bottom wall 2. Here, the shape of the bottom wall rib 31 is the same as the side wall rib 21 in the first and second embodiments, in the direction in which vibration generated with the rotation of the polygon motor is transmitted, that is, the direction from the rear end wall 4 toward the front end wall 3. On the other hand, since the inventors have clarified that the vibration is efficiently attenuated by the formation of the slant, the slanted lattice is used.

  According to such a configuration, the vibration of the box 1 generated with the rotation of the polygon motor causes the damping material 2 and further the bottom wall rib 31 to exhibit a kind of damper function in addition to the side wall rib 21. It is attenuated more effectively.

  Subsequently, FIG. 7 shows the vibration analysis result of such a laser scanning unit. FIG. 7 is also a graph showing the vibration state of the box 1 during the rotational drive of the polygon motor, as in FIGS. 3 and 5. In this embodiment (see the thick line in FIG. 7), the vibration is shifted to a lower frequency and the maximum value of the displacement is clearly reduced as compared with the conventional case (see the thin line in FIG. 7). The vibration in the box body 1 is more effectively attenuated.

  In addition, you may add the bottom wall through-hole 30 and the bottom wall rib 31 which are the feature points of this embodiment to 1st Embodiment.

  In addition, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, all of the side wall ribs 21 may be inclined forward and upward with respect to the bottom wall 2, and as illustrated in FIG. 8, all may be inclined rearward and upward with respect to the bottom wall 2. It may be inclined. In these cases, it is sufficient to make the side wall through hole 20 into a parallelogram. Moreover, as shown in FIG. 9, the shape of the side wall rib 21 may be a right triangle. Moreover, the part in which the side wall through-hole 20 and the side wall rib 21 are formed is not limited as long as it is the left and right side walls 5 and 6 of the box 1 and is a part of stress concentration during the rotational driving of the polygon motor.

  INDUSTRIAL APPLICABILITY The present invention is useful for a laser scanning unit that is mounted inside an image forming apparatus and exposes an image carrier with laser light.

It is a perspective view of the box in the laser scanning unit which is a 1st embodiment of the present invention. It is a side view which shows the principal part of the box in 1st Embodiment. It is a figure which shows the vibration analysis result of the laser scanning unit of 1st Embodiment. It is a side view which shows the principal part of the box in the laser scanning unit which is 2nd Embodiment of this invention. It is a figure which shows the vibration analysis result of the laser scanning unit of 2nd Embodiment. It is a perspective view of the box in the laser scanning unit which is a 3rd embodiment of the present invention. It is a figure which shows the vibration analysis result of the laser scanning unit of 3rd Embodiment. It is a figure which shows the modification of the side wall rib in the laser scanning unit of this invention. It is a figure which shows the modification of the side wall rib in the laser scanning unit of this invention. It is a perspective view of the box in the conventional laser scanning unit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Box body 2 Bottom wall 3 Front end wall 4 Rear end wall 5 Right side wall 6 Left side wall 10 1st attachment part 11 2nd attachment part 12 1st through-hole 13 2nd through-hole 20 Side wall through-hole 21 Side wall rib 22 Damping material 31 Bottom wall rib A Overhang part

Claims (5)

A laser light source, a polygon mirror that rotates and reflects the laser light from the laser light source, a polygon motor that drives the polygon mirror to rotate, and the laser light reflected by the polygon mirror. In a laser scanning unit consisting of a box with a reflection mirror that reflects the light toward the exit,
The polygon motor is fixed on the bottom wall on the rear end side of the box, and the reflection mirror is fixed between both side walls on the front end side of the box,
A laser scanning unit, characterized in that side wall ribs formed with a plurality of side wall through holes are provided on both side walls of the box body and in a portion where stress is concentrated during rotational driving of the polygon motor.   The box is integrally attached to the image forming apparatus with a first attachment portion formed in the vicinity of the front and rear intermediate portions of both side walls and a second attachment portion formed in the vicinity of the rear end wall, and the side walls The laser scanning unit according to claim 1, wherein a rib is provided in the vicinity of the first attachment portion.   The laser scanning unit according to claim 1, wherein the side wall rib is inclined with respect to a bottom wall of the box.   4. The laser scanning unit according to claim 1, wherein an attenuation material having a higher attenuation rate than a material of the box is loaded in the side wall through hole. 5.   The laser scanning unit according to claim 1, wherein a plurality of bottom wall ribs are provided on the bottom wall of the box.

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