JPH04149467A - Color image forming device - Google Patents

Abstract

PURPOSE:To improve the assembly and the maintenance of a gear to be driven by setting the gear to be driven which meshes with a worm gear as a helical gear. CONSTITUTION:The worm gears 18-20 are engraved on a driving shaft 29 connected to a driving motor and mesh with the helical gears 21-23 bound to the ends of the drum shafts 101-103 of photosensitive drums. Thus, the helical gears 21-23 can be assembled after attaching the worm gears 18-20 or the helical gears 21-23 can be attached without detaching the worm gears 18-20, thus the assembly and the maintenance of the helical gears 21-23 are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a color image forming apparatus such as an electrophotographic color copying apparatus or a color printer.

(Prior art) Such a color image forming apparatus arranges a plurality of G1 carriers such as photoreceptors in parallel, performs an electrophotographic process on each image carrier to obtain a developed image of each color, and transfers the developed image to a transfer material. A desired color image is obtained by transferring the image onto a transfer material conveyed by a means.

The #I diagram of a laser beam printer, which is one of this type of color image forming apparatus, is shown in FIG.
are arranged in parallel, and each image forming unit Pa, Pb, P
c has a dedicated photosensitive drum 1.2.3. Around each photosensitive drum 1.2.3, laser beam exposure means 7.8, 9. Necessary image forming process means including a charging section, an exposure section, a developing section, a transfer section, a cleaning section, etc. (not shown) are arranged respectively.

On the other hand, a transfer material conveying means 13 having an endless belt 16 is arranged below the photosensitive drum 1.2.3, and the transfer material P supplied from a paper feeder (not shown) is transferred to the transfer material conveying means 13. The image is conveyed in the direction of the arrow shown in the figure through the transfer section j125°26.27 of each image forming unit Pa, Pb, and Pc.

In the laser beam printer having the above configuration,
First, a visible image (yellow image) of yellow toner is formed in the first image forming unit Pa, and the visible image is transferred at the transfer position 25 onto the transfer material P conveyed by the transfer material conveying means 13.

Meanwhile, while the visible image (yellow image) is being transferred to the transfer material P, a visible image (magenta image) of magenta toner is formed in the second image forming unit Pb, and the visible image (magenta image) of magenta toner is When the transfer material P whose transfer has been completed in the forming unit Pa is carried into the transfer position 26 of the second image forming unit pb, the magenta image is transferred to a predetermined position on the transfer material P.

Thereafter, a visible image (cyan image, black image) of cyan toner and, if desired, black toner is formed in the same manner, and when the visible image is transferred onto the transfer material P, the transfer material P
A visible image of three or four colors is superimposed on the transfer material P, and the transferred image is fixed in a fixing section (not shown), and a desired color image is formed on the transfer material P. Ru. still.

Residual toner is removed from each of the photosensitive drums 1, 2.3 after the transfer in a cleaning section (not shown), and the drums are prepared for subsequent latent image formation.

(Problem to be Solved by the Invention) By the way, the color image forming apparatus such as the laser beam printer described above has an image forming unit for each color, which is advantageous for speeding up, and the transfer path is configured in a straight line. Although it has advantages such as being adaptable to transfer materials such as cardboard and transparent film, it is difficult to properly register each color formed by different image forming units. We have a problem to solve.

To solve the above problem, a proposal has been made to drive the photosensitive drums with a single drive source via a worm wheel (see Japanese Patent Laid-Open No. 11967/1983).
In this proposal, the distance between each photosensitive drum is set so that the time interval during which the transfer material passes between each photosensitive drum is equal to an integral multiple of the drive unevenness cycle of the drive source (drive motor), and Color misregistration is prevented by matching the phase of positional misalignment at each station caused by drive unevenness.

There has also been a proposal to prevent one color shift by adjusting the meshing position of the worm wheel that meshes with the worm gear of each image station to match the phase of the positional shift due to the cumulative pitch error of each ohm wheel.

However, in the example of the laser beam printer shown in FIG. 5, the tooth profile of the ohm wheel 21 shown in FIG. It is difficult to assemble the two while keeping their meshing positions appropriate.

Furthermore, during maintenance of the device, it is impossible to remove the worm wheel 21 alone, and assembly errors are likely to occur when the worm wheel 21 is reinstalled.

The present invention has been made in view of the above problems, and its purpose is to improve the ease of assembly and maintenance of the driven gear that meshes with the worm gear, and to solve the problem of color misalignment caused by assembly errors.

It is an object of the present invention to provide a color image forming apparatus capable of preventing image defects such as pitch unevenness.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a color image forming apparatus in which a plurality of image carriers are arranged side by side and each image carrier is driven from a common drive source via a worm gear. It is characterized in that the driven gear that meshes with the worm gear is a helical gear.

(Function) According to the present invention, since the helical gear is used as the driven gear that meshes with the worm gear, the helical gear can be installed after the worm gear is installed, or the helical gear can be installed without removing the worm gear, and the helical gear can be installed without removing the worm gear. Assembling performance and maintenance performance are improved, and since one assembly error is kept small, image defects such as color shift and pitch unevenness caused by one assembly error can be prevented.

(Example) An example of the present invention will be described below based on the accompanying drawings.

FIG. 1 is a configuration diagram of a photosensitive drum drive system of a laser beam printer according to the present invention, and FIG. 2 is a sectional view taken along the line ■-■ in FIG. 1.
FIG. 3 is a perspective view of the main parts of the laser beam printer.

To outline the basic configuration of a laser beam printer based on FIG. 3, the laser beam printer has three image forming units Pa, Pb, and Pc arranged in parallel, and each image unit Pa, Pb, and Pc has an image forming unit. Dedicated photosensitive drums 1, 2.3, which are carriers, are provided. Dedicated image forming process means are arranged around each photosensitive tram 1, 2.3, and these image forming process means include laser beam exposure means 7, 8, 9, a charging section (not shown), and an exposure unit. It is configured to include means, a developing section, a transfer section, a cleaning section, etc.

On the other hand, a transfer material conveying means 13 equipped with an endless belt 16 is arranged below the photosensitive drums 1, 2.3 marked #, and the transfer material P supplied from a paper feeding device (not shown) is transferred to 13, it is conveyed in the direction of the arrow in the figure through the transfer positions 25°26.27 of each image forming unit Pa, Pb, and Pc.

Therefore, in this embodiment, each image forming unit Pa, Pb
, Pc's photosensitive drums 1, 2.3 are rotationally driven by a drive motor 17, which is a common drive source. That is, as shown in FIG. 1, worm gears 18, 19, 20 are carved on the drive shaft 29 connected to the drive motor F, and the worm gears 18, 19, 20 are connected to the photosensitive drums 1, 2, 3.
The worm gears 18, 19, 20 are integrally geared to the drive shaft 29. Therefore, these worm gears 18, 19
．． Eccentricity is less likely to occur between the drive shaft 20 and the drive shaft 29.

Therefore, when the drive shaft 29 is rotationally driven by the drive motor 17, the rotation of the drive shaft 29 is controlled by the worm gears 18, 1.
It is transmitted to the drum shafts 101, 102° 103 through the helical gears 9.20 and 21°22.23, and the drum shaft 101
, 102 and 103 are rotated at a predetermined speed.

Incidentally, the photosensitive drums 1, 2, and 3 are arranged at a predetermined distance from each other, and the distance between them is determined by the distance between the transfer material conveying means 13 and the transfer material P. The times T I and T x for passing between positions 25 and 26 and between positions 26 and 27 are set to be equal to an integral multiple of the driving unevenness cycle of the driving means consisting of the driving motor 17 and the driving shaft 29. Therefore, the drive means 17.2
The phases of the drive unevenness of the photosensitive drums 1, 2.3 caused by the drive unevenness of 9 coincide with each other.

Here, the details of the drive system of the photosensitive drums 1, 2, and 3 are #! 1
This will be explained based on the diagram and FIG.

In this embodiment, when the worm gears 1B, 19.20 and the helical gears 21, 22.23 mesh, the worm gear 1
In order to prevent the drive shaft 29 from being bent or deformed due to the force applied to the worm gears 18, 19.
Both ends of 20 are supported by bearings 31, 32, 33, 34.

Note that the bearings 31, 32, 33, and 34 are attached to the bearing support member 35.
36, 37, 38, and the bearing support members 35, 36, 37, 38 are fixed to the main body side plate 40 (see Fig. 2).

The bearing support members 35, 36, 37, 38 may be configured to be adjustable in position with respect to the main body, and the positions of the bearings 31, 32, 33, 34 may be adjusted. Worm gear 18,
The thrust force generated in the axial direction of the drive shaft 29 by the engagement with the drive shaft 29 is received by a thrust receiver such as a circlip connected to the end of the drive shaft 29 by the member 39.

Therefore, in this embodiment, the diameter of each photosensitive drum l, 2゜3 is φ60, the number of revolutions is 30 rpm, and the reduction ratio is 1/
20. The rotation speed of the drive motor 17 is set to 600 rpm. Also, if the number of threads of the worm gear 18°19.20 is 4 and the number of modules is 1, each helical gear 21, 2
2.23 is a helical gear having a helix angle equal to the sort angle of an 80-tooth worm gear.

For example, if the pitch circle diameter of each worm gear 18, 19°20 is φ20 layer, the worm gear 18,
The lead angle α of 19.20 is α=5rn-' (
4/20) = 11.54', the helix angle of Hasha Gya 21.22.23 is 11.54''', and the pitch circle diameter d is d = 80.1/cos α = 81.65 m.
m.

Therefore, when the cumulative pitch error of Hashagya 21, 22.23 is 50p, m, this cumulative pitch error is 50pm.
The image position shift caused by this is converted into a pitch error on the surface of the photosensitive drums 1, 2.3, SOpmx60/81.6
5=36.7gm.

In this way, by increasing the pitch circle diameter d of the helical gears 21, 22.23, the helical gears 21, 22.2
The amount of positional deviation of the image can be reduced by the cumulative pitch error of 3.

In addition, the cumulative pitch error of each helical gear 21, 22.23 is measured in advance and Σ is calculated, and the phase of the image position shift caused by the cumulative pitch error of the helical gear 21, 22.23 at each image station is adjusted, and the color shift is corrected. It is also possible to minimize the

FIG. 4 is a graph showing the cumulative pitch error of the helical gears 21, 22, and 23. In this embodiment, each of the helical gears 21, 22, and
Since the number of teeth in 22.23 is 80 teeth, the horizontal axis in Figure 4 shows the number of teeth from the standard tooth to 80 teeth, and the vertical axis shows the cumulative pitch error measured from the standard tooth. 6 Normally, the cumulative pitch error is expressed numerically by the value between the peaks shown in Fig. 4, but in reality, the cumulative pitch error
It appears as a sine wave with one rotation period.

Therefore, the amount of image positional deviation Δ when using a Hasbag gear with a cumulative pitch error of 50Bm is Δ=50/2)z
m x 60/81.65'sinθ= 18.35s
inθ gm Here, θ is the angle that an arbitrary tooth makes with the reference tooth.

It can be expressed as

For example, No. Est. and #! When the position of the image at two stations or the phase of a sine wave with an amplitude of 18.35 am is shifted by 180° (π), ]8.
:is x 2 =36.7 gm of color shift occurs. In order to minimize the color shift due to the station difference, it is sufficient to match the phases of the image position shift curves of each station.

Here, the method of matching the above-mentioned phases will be described.

First, the Hasbagya 21.2 used at each station
2. Measure the cumulative pitch error of 23, find a reference tooth that can be approximated by a sine wave as shown in Figure 4, and use Hasbagya 2.
Let the reference teeth found for No. 1, 22, and 23 be n+ * nt + nx, respectively.

If the distance between the photosensitive drums 1 and 2゜3 at each station is 150wn, then it becomes 150/60π x 80 teeth - 63.7 teeth, 64 teeth, so there is a delay time between stations for 64 teeth. .

Therefore, with respect to the rotational direction of the photosensitive drums 1, 2.3, 64
Hasbagya of each station for tooth division 21.22.23
It is better to shift it to the direction of delay and incorporate it.

FIG. 1 shows the relationship between the fittings 21 and 22 of the first station and the second station. When the reference tooth n of the second helical gear of the first station is set to the position where it meshes with the worm gear 18, the reference tooth n of the second waslving gear of the W42 station is set to the first position as shown in the figure.
The position is 64 teeth behind the reference tooth n1 of the station gear 21. 3rd station helical gear 23
Similarly, the helical gears 21 to 12 of the first station are
It is sufficient to install it so that n is at a position 64 teeth behind the 8-tooth helical gear 22 of the second station.

Therefore, in this embodiment, the worm gears 18, 19.2 are used as driven gears that mesh with the worm gears 18, 19.20.
Since the helical gears 21, 22, and 23 having the same helix angle as the lead angle are used, the worm gear 1
After installing 8, 19.20, Hasbagya 21, 22.
23, or helical gears 21°, 22. without removing the worm gears 18°, 19.20.
23 can be installed, Hasbagya 21.22.2
The assemblability and maintainability of the parts 3 and 3 are improved, and axial position adjustment of these parts is not required.

(Effects of the Invention) As is clear from the above description, according to the present invention, in a color image forming apparatus in which a plurality of image carriers are arranged side by side and each image carrier is driven from a common drive source via a worm gear,
Since the driven gear that meshes with the worm gear is a helical gear, it is possible to improve the ease of assembly and maintenance of the driven gear, and it is also possible to prevent image defects such as color misalignment and pitch unevenness caused by assembly errors. You can get the effect of being able to do it.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a photosensitive drum drive system of a laser beam printer according to the present invention, and No. 2r5! i is a sectional view taken along the line ■-■ in Fig. 1, Fig. 3 is a perspective view of the main parts of the laser beam printer, Fig. 4 is a graph showing the cumulative pitch error of the ohm wheel, and Fig. 5 is a conventional laser beam printer. Perspective view of main parts,
FIG. 6 is a diagram similar to FIG. 82 of FIG. 8 of a conventional laser beam printer. 1.2.3-...Photosensitive drum (image carrier), 17...
Drive motor (drive source), 18, 19.20--worm gear, 21, 22.23-- helical gear. Patent applicant Canon Co., Ltd. Agent Patent attorney Ryo Yamashita Figure 2

Claims (1)

[Claims] A color image forming apparatus in which a plurality of image carriers are arranged side by side and each image carrier is driven from a common drive source via a worm gear, characterized in that the driven gear that meshes with the worm gear is a helical gear. Device.