JPH04368983A - Color image forming device - Google Patents

Abstract

PURPOSE:To provide the color image forming device where appearance of 'color slippage' on the image is suppressed by not deviating the parallelism between each photosensitive body in spite of a temperature change in the device. CONSTITUTION:Shafts 24Bk, 24C, 24M, and 24Y of the photosensitive bodies 14Bk, 14C, 14M, and 14Y are supported freely rotatable by a main body side plate 25. Furthermore, the shafts 24 Bk, 24C, 24M, and 24 Y are supported by shafts supporting member 33 at a part of each shaft on the side of the shaft driving part. The plate 25 and the member 33 are in parallel to each other and both are made of material with the same coefficient of linear expansion so that amount of deformation by heat of both are equalized.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming apparatus.

0002

2. Description of the Related Art Color image forming apparatuses equipped with a plurality of photoreceptors are known. FIG. 3 shows a color image forming apparatus of this type. Before explaining the prior art, the operation of this image forming apparatus will first be clarified.

This color image forming apparatus includes a scanner section 1 for reading a document, an image processing section 2 for electrically processing image signals output from the scanner section 1 as digital signals, and a It has a printer section 3 that forms an image on copy paper based on image recording information of each color. The scanner section 1 has a lamp 5, such as a fluorescent lamp, that scans and illuminates the document on the document table 4. The reflected light from the document when illuminated by the fluorescent lamp 5 is reflected by the mirror 6,
It is reflected by 7 and 8 and enters an imaging lens 9. The image light passing through the imaging lens 9 passes through the dichroic prism 1
0, and here the light is separated into three types of wavelengths, for example, red R, green G, and blue B, and a light receiver for each wavelength, for example, CCD 11R for red and CCD 11 for green, is used.
The light is incident on the CCD 11B for G and blue. Each CCD11
The outputs from R, 11G, and 11B are converted into digital signals, which are subjected to necessary processing in the image processing section 2, and recorded color information for each color, such as black (hereinafter abbreviated as Bk), yellow (abbreviated as Y), magenta (abbreviated as M), cyan (
The signal is converted into a signal for recording of each color (abbreviated as C).

Although FIG. 1 shows an example of forming four colors, Bk, C, M, and Y, it is also possible to form a color image using only three colors. In that case, the number of recording devices can be reduced by one compared to the example of FIG.

The signal from the image processing section 2 is sent to the printer section 3.
and each color laser beam emitting device 12Bk
, 12C, 12M, and 12Y.

In the illustrated example, four sets of recording devices 13Bk, 13C, 13M, and 13Y are arranged side by side in the printer section. Since each recording device 13 is made of the same constituent members, in order to simplify the explanation, the recording device for C will be explained, and the explanations for other colors will be omitted. For each color, the same parts are given the same reference numerals, and in order to distinguish the configuration of each color, the subscripts indicated by the codes are given for each color.

The recording device 13C is a laser beam emitting device 12C.
In addition to the photoreceptor 14C, for example, a drum-shaped photoreceptor as shown in the drawing is provided.

A charger 15C is attached to the photoreceptor 14C.
, an exposure device using a laser beam emitting device 12C, and a developing device 1
6C, a transfer charger 17C, etc. are attached in the same manner as in a known copying apparatus.

A cyan latent image is formed on the photoreceptor 14C uniformly charged by the charger 15C by exposure by the laser beam emitting device 12C, and this latent image is developed by the developing device 16C and becomes a visible image. is formed. A transfer paper, which is an example of a transfer material, is supplied from a paper supply unit 19 by a paper supply roller 18 . For example, a transfer sheet supplied from one of two paper feed cassettes is sent to a transfer belt 21 with its leading edge aligned by registration rollers 20 and at the same timing. The transfer paper conveyed by the transfer belt 21 is transferred to photoreceptors 14Bk, 1 on which developed images of different colors are formed.
Transferred to 4C, 14M, 14Y sequentially, transferred to transfer charger 1
7, the developed images of each color are superimposed and transferred to the same position. The transferred transfer paper is fixed by a fixing roller 22 and discharged to the outside of the machine by a paper discharge roller 23.

The transfer paper is electrostatically attracted to the transfer belt 21 and is conveyed with high precision at the speed of the transfer belt.

By the way, the following structure for supporting the photoreceptor shaft of conventional image forming apparatuses has generally been adopted.

As shown in FIG. 4, a drum-shaped photoreceptor 44
is supported by a photoreceptor shaft 64 located at the center, and this shaft 64 is connected to a main body side plate 65 of the image forming apparatus and a support member 36 fixed thereto by screws 47 via bearings 50 and 51. The photoreceptor 44 is rotatably supported by the shaft 64, and the photoreceptor 44 and the flange 37 rotate together with the shaft 64.

A pulley 38 is fixedly mounted on the end of the shaft 64, and the photoreceptor 44 is rotationally driven via a timing belt 39 connected to a motor pulley (not shown).

FIG. 5 shows an example in which such a configuration is adopted in a color image forming apparatus equipped with a plurality of photoreceptors. Note that FIG. 5 is a sectional view of the photoreceptor shaft support component when the image forming apparatus of FIG. 3 is viewed from above on the back side.

[0015] Drum-shaped photoreceptors 14Bk, 14C, 14
M, 14Y is the flange 27Bk, 27C, 27M, 2
These photoreceptors are fixed to the respective shafts 24Bk, 24C, 24M, and 24Y via 7Y, and these photoreceptors are arranged in a row in one direction. In addition, each of these axes 24Bk to 24Y is connected to the main body side plate 2.
5 and each support member 26Bk to Y, bearings 50, 5 are provided.
1 and is rotatably supported. Each photoreceptor 14B
k to Y are motor pulleys 5 due to the driving force of the motor 52.
3 and each pulley 54Bk-Y via belts 55Bk-Y, which are respectively stretched around the pulleys 54Bk-Y.

According to such a configuration, one motor 5
2, each photoreceptor can be rotationally driven. However, with such a configuration, when the motor 52 is started, a force F is applied to each shaft due to the load on each photoreceptor shaft 24Bk to Y, and each shaft is bent and deformed. Deflection occurs in the side plate 25. In this case, the mutual parallelism of the photoreceptors deteriorates, which causes color shift, and there is a risk that image quality will deteriorate.

An example shown in FIG. 6 solves this problem.

This example uses a worm and a worm wheel to drive each photoreceptor, and the rotation of the motor 31 drives each photoreceptor 14Bk to Y in a predetermined direction. That is, the shaft of the motor 31 is connected to one end of a worm shaft 30 via a timing belt drive section 32, and the worm shaft 30 has worms 29Bk, 29C, 29M, and 29Y for driving each of the photoreceptors 14Bk to 14Y.
are provided, and a worm wheel 28Bk on each photoreceptor side,
It meshes with 28C, 28M, and 28Y. Since the relationship between each worm wheel and the photoreceptor is the same,
One of them will be described (in this case, the subscripts for each color attached to each symbol will be omitted). The photoreceptor 14 is integrally fixed with a photoreceptor shaft 24 via a flange 27, and the photoreceptor shaft 24 is rotatably supported by a shaft support member 26 attached to a side plate 25 of the main body, and a worm is attached to one end of the photoreceptor shaft 24. A worm wheel 28 that meshes with 29 is attached. Further, the shaft support member 26 rotatably supports the worm shaft 30.

Each worm drive portion in which the worm wheel 28 and the worm 29 engage is provided with a sealed oil box 35 containing lubricating oil.

According to such a configuration example, the photoreceptor shaft 24
Although bending deformation and the like are less likely to occur, the following problems occur.

The color image forming apparatus includes heat generating sources such as the fixing roller 22 (FIG. 3) and a heater for preventing dew condensation (not shown), so that the temperature inside the apparatus tends to change. Furthermore, the temperature inside the device also changes due to changes in the ambient temperature.

Conventionally, the main body side plate 25 was made of, for example, a steel plate, and the shaft support member 26 was made of, for example, aluminum die-casting, and because of their different coefficients of linear expansion, the device When the internal temperature changes, the amount of expansion and contraction of the two will be different, and there is a risk that the shaft end drive component will be warped as shown by arrow A in the figure.

In other words, if the coefficient of linear expansion of the shaft support member 26 is greater than that of the main body side plate 25, when the temperature inside the device increases, the shaft support member 26 will move in the X direction toward the main body side plate. 25, and the above-mentioned "
There was a risk of warping. On the other hand,
When the temperature drops, "warping" tends to occur in the opposite direction.

Conventionally, "warping" is likely to occur due to such temperature changes, and the axes of each photoreceptor 24 are elastically inclined, resulting in poor mutual parallelism of the photoreceptors 14. This may cause "color shift" on the image.

[0025]

[Problem to be Solved by the Invention] An object of the present invention is to provide sufficient rigidity to the holding portion of the photoreceptor shaft so that the mutual parallelism of each photoreceptor will not be disturbed even if the temperature inside the apparatus changes. The objective is to suppress the occurrence of "color shift" on images and to obtain images of good quality.

[0026]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a method for unidirectionally moving a plurality of photoreceptors, each of which forms a developed image of a different color, for overlapping transfer at the same position on a transfer material. In a color image forming apparatus arranged in a row, the image forming apparatus main body side plate rotatably supports the shafts of a plurality of photoreceptors collectively on the photoreceptor side, and a shaft that rotationally drives each photoreceptor shaft on its shaft end side. a drive section; and a shaft support member that is disposed opposite to and parallel to the main body side plate at a distance from the main body side plate, and rotatably supports each of the photoreceptor shaft parts on the shaft drive section side. A color image forming apparatus is proposed in which the shaft support member and the main body side plate are made of materials having substantially the same coefficient of linear expansion.

Note that the shaft drive section consists of a worm provided on the same worm shaft and a worm wheel provided at the end of each photoreceptor shaft and engaged with each worm, and the shaft support member supports each worm shaft. It is effective to have an extension support part that is supported rotatably, and to integrally mold the extension support part with the shaft support member.

[0028] Furthermore, the shaft driving section consists of a worm provided on the same worm shaft and a worm wheel provided at the end of each photoreceptor shaft and meshing with each worm, and the shaft support member supports the photoreceptor shaft. A shaft support plate portion that supports the worm shaft substantially rotatably; a support portion that connects the shaft support plate portion and the main body side plate for each photoreceptor shaft; and an extension support that rotatably supports each worm shaft. It is effective if the three parts are integrally molded.

[0029]

[Example] In FIG. 1, the main body side plate indicated by the reference numeral 25 is
Along with each of the support members 26Bk-Y to be described next, the four photoreceptor shafts 24Bk-Y are rotatably supported together via a bearing 50 on the photoreceptor side. Hereinafter, the subscripts for each color attached to each symbol will be omitted for convenience.

Each photoreceptor 14 is fixedly supported on a shaft 24 via a flange 27.

A shaft driving section for rotationally driving the photoreceptor shaft 24 is provided at the end of each of the photoreceptor shafts 24. In this example, such a shaft drive unit includes a worm 29 provided on the same worm shaft 30 and a worm wheel 2 fixedly attached to the shaft end of each photoreceptor shaft 24 and meshing with each worm 29.
It consists of 8. Each worm 29 is connected to a motor 31 via a timing belt drive unit 32 and a worm shaft 30.
The photoreceptor 14 is rotated by the photoreceptor 14, thereby causing each photoreceptor 14 to rotate. 35 is a sealed oil box.

A shaft supporting member 33 is arranged parallel to and at a predetermined distance from the main body side plate 25. Between this shaft support member 33 and the main body side plate 25,
A support member 26 provided for each photoreceptor is fixedly connected, and the shaft supporting member 33 is connected to each shaft portion of the photoreceptor shaft 24 on the shaft driving portion side through a bearing 51 together with the support member 26. are supported in a rotatable manner. In this way, the common shaft support member 33 connects each support member 26.

The feature of this embodiment is that the main body side plate 25 and the shaft supporting member 33 are made of materials having substantially the same coefficient of linear expansion. For example, both can be made of steel plates. On the other hand, the support member 26 may be made of aluminum, such as aluminum die-casting, in addition to being made of steel.

By making the main body side plate 25 and the shaft support member 33 of materials with the same coefficient of linear expansion, even if the temperature inside the image forming apparatus changes, the amount of expansion and contraction is the same, and the photoreceptor The shaft 24 is less likely to be bent or deformed, and the parallelism of each photoreceptor 14 can be prevented from deteriorating. Note that the main body side plate 25 and the shaft support member 33 may be made of, for example, an aluminum plate instead of a steel plate, or may be made of a rigid plastic plate.

Here, worm shaft support members 34a, 34b, 34c, 34d, and 34e are screwed to the shaft support member 33 at the positions shown in the drawings, and these members rotatably support the worm shaft 30. There is.

In the embodiment shown in FIG. 2, such a worm shaft support member is integrally formed with the shaft support member 33. That is, the symbols 33a, 33b, 33c, 33d,
As shown at 33e, this is integrally molded with the shaft supporting member 33 as an extension support portion.

With this configuration, if the stretching support portion is formed with high precision, the perpendicularity precision between the photoreceptor shaft 24 and the worm shaft 30 can be improved, and the worm 29 and the worm shaft can be formed with high accuracy. The engagement with the wheel 28 becomes smooth, making it possible to prevent or reduce rotational wobbling of the photoreceptor 14. This makes it possible to further improve color image quality.

In this embodiment as well, for example, while the main body side plate 25 is made of steel plate, the shaft support member 33 is made of cast metal, thereby making it easier to manufacture the shaft support member 33. In this case, both materials are made of materials with substantially the same coefficient of linear expansion, and the amount of expansion and contraction of both materials due to temperature changes will be substantially the same. Even in this embodiment, deterioration of the parallelism of each photoreceptor 14 can be prevented.

In the embodiment shown in FIG. 2, the support member 26B
k, 26C, 26M, and 26Y are not integrally molded with the shaft support member 33, but have a separate structure, but these support members may be integrally molded with the shaft support member. .

Now, borrowing the conventional example of FIG.
As shown in the figure, the shaft support member 26 is divided into a shaft support plate portion 66 that substantially rotatably supports the photoreceptor shaft 24, and a shaft support plate portion 66 and a main body side plate 25 for each photoreceptor shaft. Support parts 67a, 67b, 67c, 67d connecting between the support parts 134a, 134b, 134c, 134d,
4e, and these three are integrally molded.

The main body side plate 25 and the shaft support member 26 are made of materials having substantially the same coefficient of linear expansion. With this configuration, the support member 26 as shown in FIG. 2 becomes unnecessary as a component, and the assembly of such components becomes easy. Furthermore, if the support portions 67a, 67b, 67c, and 67d are formed in advance with high accuracy, the parallel accuracy of the photoreceptor axis can be further improved, and the parallel accuracy of the photoreceptor can be further improved.

In this example as well, if the main body side plate 25 is made of, for example, a steel plate, the shaft supporting member 26 is made of, for example, cast iron. In addition, when the main body side plate 25 is made of a rolled aluminum plate or the like, the shaft support member 26 can be made of die-cast aluminum to facilitate its manufacture. Similarly, in the embodiment shown in FIG. 2, if the main body side plate 25 is made of, for example, a rolled aluminum plate, the shaft support member 33 can be made of die-cast aluminum, for example, to facilitate its manufacture. The same is true when it is made of plastic. In this way, a combination of materials having substantially the same coefficient of linear expansion can be appropriately employed.

Note that even in the case of the photoconductor driving method shown in FIG. 5, each shaft end side of each photoconductor shaft 24 is
If the side plate is collectively supported by a side plate similar to 5, and the side plate is made of a material having the same coefficient of linear expansion as the main body side plate 25, the same function can be achieved.

[0044]

According to the color image forming apparatus according to the first aspect, the main body side plate for supporting the shafts of the plurality of photoreceptors, and the shaft support member for supporting the shaft driving section side of the shafts, Even if the surrounding temperature changes, the photoconductor expands and contracts at the same rate of expansion and contraction, which prevents bending and deformation of the photoconductor axis, and prevents the mutual parallelism of the photoconductors from being disrupted.
The occurrence of "color shift" on images is suppressed, and color image quality can be further improved.

According to the second aspect of the present invention, it is possible to improve the perpendicularity accuracy between the photoreceptor axis and the worm axis, and the meshing between the worm and the worm wheel becomes smooth, thereby reducing rotational vibration of the photoreceptor. The occurrence of such problems can be suppressed, and color image quality can be further improved.

According to the structure described in claim 3, it becomes easy to assemble the main body side plates, the shaft support member, etc. to each other, and
The parallel accuracy of the photoreceptor axis is further improved, resulting in even better color image quality.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a photoreceptor shaft support component of a color image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of another example of a photoreceptor shaft support structure.

FIG. 3 is an overall configuration diagram of the image forming apparatus.

FIG. 4 is a cross-sectional view of a typical support arrangement for a photoreceptor shaft.

FIG. 5 is a cross-sectional view of a conventional photoreceptor shaft support structure.

FIG. 6 is a cross-sectional view of yet another conventional photoreceptor shaft support structure.

[Explanation of symbols]

14Bk Photoreceptor 14C Photoreceptor 14M photoreceptor 14Y Photoreceptor 24Bk Photoreceptor axis 24C Photoreceptor axis 24M photoreceptor shaft 24Y Photoconductor axis 25 Main body side plate 28Bk Worm wheel 28C Worm wheel 28M worm wheel 28Y Worm wheel 29Bk Warm 29C Warm 29M Worm 29Y Warm 30 Worm shaft 33 Axial support material 33a Stretch support part 33b Stretching support part 33c Stretch support part 33d Stretching support part 33e Stretch support part 66 Shaft support plate part 67a Support part 67b Support part 67c Support Department 67d Support part 134a Stretch support part 134b Stretching support part 134c Stretch support part 134d Stretching support part 134e Stretch support part

Claims (3)

[Claims] Claim 1. A color image forming apparatus in which a plurality of photoreceptors are arranged in one direction, forming developed images of different colors for overlapping transfer at the same position on a transfer material. An image forming apparatus main body side plate that rotatably supports the shafts all together on the photoreceptor side, a shaft drive unit that rotationally drives each photoreceptor shaft on its shaft end side, and a main body that is spaced apart from the main body side plate. a shaft supporting member arranged to face and parallel to the side plate and rotatably supports each of the photoreceptor shafts on the shaft driving unit side; the shaft supporting member and the main body side plate; A color image forming apparatus characterized in that it is constructed of materials having substantially the same coefficient of linear expansion. [Claim 2] The shaft drive section includes a worm provided on the same worm shaft and a worm wheel provided at the end of each photoreceptor shaft and meshing with each worm. 2. The color image forming apparatus according to claim 1, further comprising a rotatably supported stretching support part, and the stretching support part is integrally molded with the shaft supporting member. 3. The shaft drive section is composed of a worm provided on the same worm shaft and a worm wheel provided at the end of each photoreceptor shaft and engaged with each worm, and the shaft support member is configured to drive the photoreceptor shaft. A shaft support plate portion that supports the worm shaft substantially rotatably; a support portion that connects the shaft support plate portion and the main body side plate for each photoreceptor shaft; and an extension support that rotatably supports each worm shaft. Claim 1 consisting of a
The color image forming apparatus described in .