JP3667986B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus including a plurality of optical writing units.
[0002]
[Prior art]
For example, in a full-color image forming apparatus, as shown in FIG. 7, four image forming cartridges 102 integrally provided with a photosensitive drum 100 and the like are juxtaposed in the vertical direction, and the optical writing means 104 is juxtaposed correspondingly. ing.
Each light writing means 104 scans a light beam on the photosensitive drum 100 of each image forming cartridge 102, thereby forming an electrostatic latent image on the photosensitive drum 100. In the optical writing means 104, a light beam generated by a laser diode (not shown) is scanned by the action of the polygon mirror 106, and the target is transmitted through the first fθ lens 108, the folding mirrors 110 and 111, and the second fθ lens 112. A beam spot is irradiated onto the photosensitive drum 100.
In the image forming cartridge 102, in addition to the photosensitive drum 100, a group of parts necessary for image formation such as a cleaning unit, a charging unit, a developing unit, and toner (not shown) and having a replacement life are provided.
Each image forming cartridge 102 contains toner of different colors Y (yellow), M (magenta), C (cyan), and Bk (black), and is conveyed on the transfer belt 114 at a predetermined timing. Images of each color are sequentially superimposed on the sheet to be finally obtained a full color image. The sheet exiting from the sheet exit path is sent to a fixing device (not shown) where the toner is fixed as a permanent image on the sheet by heat and pressure.
[0003]
In such an image forming apparatus, since the image forming cartridges 102 are arranged at a short juxtaposition distance, the optical writing unit 104 cannot be installed between the image forming cartridges 102, and the optical writing unit 104 is separated from the photosensitive drum 100. It will be arranged at a relatively distant position. For this reason, when vibration occurs in the optical writing means 104, the beam displacement on the photosensitive drum 100 becomes large, and a phenomenon called banding described later tends to occur.
[0004]
As shown in FIGS. 8 and 9, the device structure (device main body) basically includes a top plate 116, a bottom plate 118, a front side plate 120, a rear side plate 122, a left side plate 124, and a right side plate 126. Each structural plate is shown in a simple shape in the drawing, but actually has a number of notches, bends, holes and the like for mounting components, and is a complicated shape.
A plate-like base member 128 is placed between the front side plate 120 and the rear side plate 122, and the optical writing means 104 is installed on the base member 128. The rear end portion of the base member 128 is fixed to the rear side plate 122, and the front end portion is supported by the front side plate 120 via the adjusting means 130. The base member 128 and the adjusting means 130 form a bridge structure.
[0005]
The adjusting means 130 has a mechanism for displacing the front end portion of the base member 128 in the vertical direction so that the scanning inclination of the light beam radiated from the optical writing means 104 can be adjusted. Such adjustment can prevent the four color images from being inclined and superimposed. In order to enable the displacement of the base member 128 by adjustment, a slit-shaped notch 128a is formed at the rear end portion of the base member 128 so that the hinge function can be easily developed. Here, the adjusting means 130 is provided corresponding to all four colors, but the base member 128 of the optical writing means 104 corresponding to one reference color is directly connected to the front side plate 120 and the rear side plate without going through the adjusting means 130. A configuration may be adopted in which one adjustment means 130 is omitted between the adjustment unit 130 and the second adjustment unit 130.
[0006]
In addition to the above configuration, techniques relating to position adjustment of the optical writing means or prevention of positional deviation include those described in JP-A-5-6071, JP-A-7-104545, and JP-A-6-34901. .
The technique described in Japanese Patent Laid-Open No. 5-6071 is an apparatus in which an optical writing means is attached to an apparatus structure through a spring, a screw or the like, and the technique described in Japanese Patent Laid-Open No. 7-104545 is In order to prevent color misregistration due to thermal expansion, the device structure is formed of a material having a small thermal expansion coefficient such as ceramic. The technique described in Japanese Patent Laid-Open No. 6-34901 uses an elastic member between the housing of the optical writing means and the cover to suppress the vibration of the cover and prevent the influence on the optical writing.
[0007]
[Problems to be solved by the invention]
As described above, the configuration in which the image forming cartridge 102 and the optical writing means 104 are juxtaposed in the vertical direction can reduce the size of the apparatus, but the base member 128 and the adjusting means 130 have a bridge structure. As shown in FIG. 10A, the vertical vibration mode shown in FIG. 10A and the torsional vibration mode shown in FIG. 10B exist.
For this reason, when the vibration of the driving device or the like is transmitted via the front side plate 120 and the rear side plate 122 and the entire optical writing means 104 is vibrated, a periodic displacement of the light beam position on the photosensitive drum 100 is caused. Further, the scanning pitch unevenness in the sub-scanning direction according to the resonance frequency occurs. This is periodic density unevenness in the sub-scanning direction on the image, and is called banding.
Banding has a feature that it is very easy to visually discriminate near 0.5 mm pitch, but it becomes difficult to visually discriminate when the frequency of vibration becomes higher and the pitch on the image is narrowed. For this reason, when the resonance frequency in the vibration mode is low, it is easy to visually discriminate, and the image quality is remarkably impaired.
Furthermore, in an image forming apparatus provided with a plurality of optical writing means, (1) the driving device tends to be complicated and its vibration generation level tends to be high, and (2) the cross-sectional area of the optical writing means due to the demand for miniaturization of the apparatus. Since it is difficult to construct a structure having sufficient strength for the convenience of space around the optical writing means, it is difficult to construct one structure. The problem of banding is more serious than that of an image forming apparatus compatible with a single color that uses optical writing means.
[0008]
In the prior art disclosed in each of the above publications, there is no banding countermeasure from the viewpoint of anti-vibration of the optical writing means for the device structure, and there is no content to suggest.
[0009]
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus capable of suppressing the vibration of the optical writing unit with respect to the apparatus structure and suppressing the banding.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the present invention improves the structural strength of the device structure and suppresses vibrations generated in the device structure.
Specifically, in the invention described in claim 1, in the image forming apparatus in which the plurality of optical writing units are arranged in the vertical direction of the apparatus, the plurality of optical writing units are respectively provided on the side plates constituting the structure of the apparatus. A base member for fixing, a pressing unit that applies a pressing force to the base member in an upward or downward direction of the apparatus, and a plurality of optical writing units that are adjacent to each other in the horizontal direction of the apparatus. A plurality of image forming cartridges provided , and the pressing means is provided so as to suppress an abdomen of an amplitude of a vibration mode of the optical writing means .
[0011]
According to a second aspect of the present invention, in the image forming apparatus according to the first aspect,
The pressing means has a configuration in which each pressing means is set to a size that applies a pressing force in the vertical direction to the optical writing means.
According to a third aspect of the present invention, the image forming apparatus according to the first aspect further includes an adjusting unit for adjusting a shift of a scanning line from another optical writing unit.
According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect, a bridge structure is formed by the base member and the adjusting means.
According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, the pressing unit generates an elastic pressing force .
According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, the pressing means generates a viscoelastic pressing force.
[0012]
【Example】
Embodiments of the present invention will be described below with reference to the drawings. Note that the same parts as those in the conventional technique are denoted by the same reference numerals, and redundant description in terms of structure or function is omitted unless particularly necessary.
First, an embodiment corresponding to claim 1 will be described.
As shown in FIGS. 1 to 3, the image forming apparatus according to the present embodiment is a full-color image forming apparatus. Like the related art, four image forming cartridges 102 are arranged vertically and correspondingly. Four optical writing means 104 are juxtaposed vertically.
In this embodiment, the image forming cartridge 102 and the optical writing means 104 are juxtaposed at a narrow pitch in order to realize further miniaturization of the apparatus.
Between each optical writing means 104, strictly, between the base member 128 and the optical writing means 104 therebelow, a pressing means 2 for generating an elastic pressing force is provided.
The pressing means 2 is a leaf spring and has a shape as shown in FIG. 3 and is fixed to the lower surface of each base member 128. The pressing means 2 includes a fixed portion 2a fixed to the base member 128 and a curved convex portion 2b that generates an elastic pressing force. The curved protrusions 2b are set to a size that applies a vertical pressing force to the optical writing means 104 when assembled.
In FIG. 1, the base member 128 is omitted.
[0013]
Since the pressing force by the pressing means 2 acts to suppress the abdomen of the amplitude of the vibration mode of the optical writing means 104 located on the bridge structure, a vibration suppressing function is obtained and banding is suppressed.
If the pressing force of each pressing means 2 is made the same, the pressing force (elastic force) at the top and bottom of the optical writing means 104 is canceled out, and it is preferable that the optical writing means 104 is not bent.
In this embodiment, the pressing means 2 is also attached to the base member 128 on which the lowermost optical writing means 104 without the adjacent optical writing means 104 is installed, but similarly there is no adjacent optical writing means 104. The pressing means 2 may be provided so as to act on the uppermost optical writing means 104. In this case, the vibration suppressing function can be further enhanced.
[0014]
Next, another embodiment will be described with reference to FIGS.
In this embodiment, a vibration isolating means 4 that generates a viscoelastic force is provided between the base member 128 and the optical writing means 104. As shown in FIG. 6, the vibration isolating means 4 in this embodiment is a rectangular parallelepiped vibration isolating rubber having viscoelastic characteristics, and is fixed to the lower surface of the base member 128. The vibration isolating unit 4 may be fixed to the upper end of the optical writing unit 104.
In FIG. 4, the base member 128 is omitted.
According to the present embodiment, the above-described vibration mode is effectively suppressed by the vibration proofing action by the vibration energy conversion by the vibration proof means 4.
[0015]
Compared to the elastic suppression by the pressing means 2 in the above embodiment, it is possible to obtain a vibration-proof effect due to viscosity even if the elastic force is set low, so that the force acting on the optical writing means 104 can be reduced. Since the deformation due to the vibration proof support can be suppressed to a small level, it is also effective in maintaining accuracy.
From the viewpoint of enhancing the overall vibration suppressing function, the pressing unit 2 may be fixed to the upper end surface of the uppermost optical writing unit 104 where the adjacent optical writing unit 104 does not exist and the lowermost base member 128.
Further, if the vibration isolating means 4 is brought into contact with the base member 128 or the optical writing means 104 via an elastic member such as a leaf spring, the adjusting means 130 is allowed to function without requiring large deformation of the vibration isolating rubber. Can be preferred.
[0016]
【The invention's effect】
According to the present invention , vibration of the optical writing means can be suppressed, and banding can be suppressed.
[Brief description of the drawings]
FIG. 1 is a schematic front view of a main part of an image forming apparatus according to an embodiment of the present invention.
FIG. 2 is a side view of the same outline.
FIG. 3 is a perspective view of a pressing unit.
FIG. 4 is a schematic front view of a main part of an image forming apparatus according to another embodiment.
FIG. 5 is a side view of the same outline.
FIG. 6 is a perspective view of a vibration isolating means.
FIG. 7 is a schematic front view of a main part of a conventional image forming apparatus.
FIG. 8 is a schematic plan view of the same.
FIG. 9 is a side view of the same outline.
10A and 10B are diagrams showing vibration modes, where FIG. 10A is a vertical vibration mode, and FIG. 10B is a torsional vibration mode.
[Explanation of symbols]
2 Pressing means 4 Vibration isolating means 104 Optical writing means 128 Base member 130 Adjusting means

Claims (6)

In an image forming apparatus in which a plurality of optical writing units are arranged in the vertical direction of the apparatus,
Each of the plurality of optical writing means has a base member to be fixed to a side plate constituting the structure of the device,
Pressing means for applying a pressing force to the base member in the upward or downward direction of the apparatus;
A plurality of image forming cartridges provided adjacent to the plurality of optical writing means in the horizontal direction of the apparatus, respectively , and the pressing means is provided so as to suppress an abdominal portion of the vibration mode amplitude of the optical writing means. an image forming apparatus characterized by being. The image forming apparatus according to claim 1.
The image forming apparatus according to claim 1, wherein each of the pressing means is set to a size that applies a pressing force in the vertical direction to the optical writing means when assembled. The image forming apparatus according to claim 1.
An image forming apparatus comprising: an adjusting unit for adjusting a shift of a scanning line from another optical writing unit. The image forming apparatus according to claim 3.
An image forming apparatus, wherein a bridge structure is formed by the base member and the adjusting means. The image forming apparatus according to any one of claims 1 to 4, wherein:
The image forming apparatus , wherein the pressing means generates an elastic pressing force . The image forming apparatus according to any one of claims 1 to 4 , wherein:
The image forming apparatus, wherein the pressing means generates a viscoelastic pressing force.

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