JPH067283B2 - Color image forming apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application range] The present invention relates to a transfer type color image forming apparatus such as a copying machine or a recording apparatus for transferring an image of an image carrier onto a transfer material supported by a transfer material support. It is a thing.

[Conventional technology]

As a transfer type color image forming apparatus, a drum-shaped image carrier and a transfer material support are brought close to or in contact with each other and synchronously rotated, and a color toner image formed on the image carrier is transferred to a transfer material on the support a required number of times. However, there are those that obtain a color image.

[Problems to be solved by the invention]

In such a situation, compared to driving the image carrier and the transfer material support by a common motor, the image carrier does not undergo fluctuation in the rotational load of the transfer material support, and even if it receives it, it is small. In order to achieve this, each of them is driven by a separate motor, and the synchronization is performed by using a common crystal oscillator.
LL) can be used.

However, when the rotational load of the transfer material support changes, the speed of the support changes. The position change due to the speed variation causes a color shift due to the position shift unless it is corrected before the front end of the transfer material reaches the transfer position.

[Purpose of the present invention]

It is an object of the present invention to solve the above problems and provide a color image forming apparatus capable of obtaining an image without color misregistration.

[Means / actions for solving problems]

In the present invention, the operation for changing the rotation of the transfer material support, for example, the gripping of the transfer material is completed before the latent image formation on the image carrier is started. That is, the present invention provides a movable transfer material support that supports a transfer material for sequentially transferring a color toner image to a transfer material after developing a latent image formed on the image support with color toner. A color image forming apparatus having a transfer material support provided with a holding means for holding the transfer material, and having a detection means for detecting the transfer material on the transfer material support after the transfer material is held by the holding means, The latent image formation on the image carrier is started at the same time as or after the detection means detects the transfer material.

FIG. 5 is a sectional view of a full-color recording apparatus to which the present invention can be applied. In the figure, a primary charger 2, a developing device 3, a transfer drum 4, and a photosensitive drum 1 which rotate clockwise are arranged around the photosensitive drum 1. The cleaning device 5 is arranged close to or in contact with the cleaning device 5. Between the primary charging device 2 and the developing device 3, there is a portion where the laser light from the laser scanner 6 is scanned on the photosensitive drum 1, that is, an exposure portion 7. The developing device 3 is a rotating body,
The yellow, magenta, cyan, and black developing devices are supported in a circumferentially divided manner. Then, corresponding to each electrostatic latent image, it is indexed to the developing position and the latent image is visualized with toner.

Next, the toner on the photosensitive drum 1 is transferred to the transfer material supported on the transfer drum 4 in the transfer portion 8 by corona discharge of the charger 9. The untransferred toner on the photosensitive drum 1 is cleaned by the cleaning device 5.

On the other hand, the transfer material is sent out from the cassette 10 and the roller pair 1
It is abutted against the nip portion of the register roller pair 12 via 1. The transfer material is the gripper 1 on the transfer drum 4.
Corresponding to No. 3, it is sent out by the register roller pair 12, and when the gripper 13 passes through the cam 14 and closes, its tip is pinched. After the required number of times of transfer, the transfer material is separated from the gripper opened by the separation cam 15 by the separation claw 16 and discharged to the external tray via the transport unit 17 and the fixing unit 18.

Next, the method of supporting and driving the photosensitive drum 1 and the transfer drum 4 will be described. As shown in FIGS. 2 and 3, the photosensitive drum 1 is supported by a front plate (not shown) and a rear plate 20 of the main body and transferred. The drum 4 is supported by a support body 21 fixed to this side plate via a shaft 22. The support body 21 is movable with respect to the front and rear side plates, and the photosensitive drum 1 and the transfer drum 4
After adjusting the interval to a predetermined value, it is fixed to the front and rear side plates with screws 23.

The drive motor 24 for the photosensitive drum is fixed to the rear side plate 20, and the output shaft 25 thereof is provided with a gear 26. The gear 26 meshes with a photosensitive drum gear 27 that is integrally attached to the rotary shaft of the photosensitive drum 1. The transfer drum drive motor 28 is fixed to the support 21, and the output shaft 29 thereof is provided with a gear 30. The gear 30 is integrally attached to the transfer drum, and meshes with a transfer drum gear 31 rotatable around the support shaft 22.

As shown in FIG. 3, the photosensitive drum 1 and the transfer drum 4 are not in contact with each other, and the transfer drum 4 is opened by leaving a cylindrical drum body at both ends and a connecting portion thereof, and a screen-shaped open portion is provided. The transfer material support member 41 is stretched, and the above-mentioned interval is the distance between the surface of the photosensitive drum 1 and the surface of the support member 41. This distance is equal to or less than the thickness of the transfer material, so that the transfer is efficiently performed. In this way, by separating the drive motors of the photosensitive drum and the transfer drum so that the photosensitive drum gear and the transfer drum gear are not engaged, the drive motors of the photosensitive drum and the transfer drum are commonly used to engage the photosensitive drum gear and the transfer drum gear. Compared with the case described above, load fluctuations of the transfer drum and other vibrations are not directly transmitted to the photosensitive drum, which is preferable.

The drive motors for the photosensitive drum 1 and the transfer drum 4 are controlled by a phase locked loop circuit using a common crystal oscillator as shown in FIG. 4, and the peripheral speeds of the respective drums are the same.

In the case of color multiple transfer, the speeds of the photosensitive drum 1 and the transfer drum 4 during transfer are of course the same, and the toner image on the photosensitive drum 1 is aligned with the leading edge of the transfer material, and the leading edge alignment between the toner images is performed. Need to It does the following:

In FIG. 1, the distance from the exposure position 7 on the surface of the photosensitive drum 1 to the transfer position 8 in the rotation direction is L, and the transfer drum 4 is
L ≦ when the distance from the position where the front end of the transfer material P on the surface is detected to the transfer position 8 in the rotation direction is l
When L = 1, the detection element 32 is turned on and exposure is started at the same time. On the other hand, when L <l, the detection element 32 is turned on and exposure is delayed by l−L. A hall element or a photo interrupter is used as the detection element 32, and is installed on the side plate of the main body or the support 21. On the other hand, the end face of the gear 31 is located at a position corresponding to the leading edge of the transfer paper, and the magnet 33 for the hall element or the photo element, respectively. A light shield for the interrupter is provided.

However, even with the above configuration, the drum speed may change due to load fluctuations of the photosensitive drum 1 and the transfer drum 4. Particularly in the case of the transfer drum 4, when the gripper 13 is opened, the gripper itself or its acting member rides on the cam 14. As a result, the rotation of the drive motor 28 may be temporarily reduced, the transfer drum 4 may be delayed with respect to the photosensitive drum 1, and a positional deviation may occur.

Therefore, in the present invention, as shown in FIG. 1, the holding position 34 is located upstream in the rotational direction with respect to the position of the tip detecting element 32 of the transfer material P, so that the transfer drum 4 after the tip detection (= exposure start) is detected. Temporary fluctuations in speed can be avoided. Although the above description is for L = 1, when L <l, the position from the transfer position on the transfer material supporting surface of the transfer drum 4 to the position L,
That is, the clamping is completed before the start of exposure.

On the other hand, a similar speed fluctuation may occur when the gripper 13 is mounted on the cam 15 when the transfer material P is separated from the transfer drum 4, but at that time, the rotation of the transfer drum is increased once and finally It is only necessary to set the positional relationship in which the toner of the color is separated after the transfer. Of course, even when the transfer material P is nipped,
The rotation surface may be rotation for sandwiching, and the exposure may be started from the subsequent two rotation surfaces. However, extra rotation before and after the rotation ultimately slows down the image forming speed.

In the above description, the image carrier and the transfer material support are drum-shaped, and each is one, but there are a plurality of image carriers for each color, and the transfer material support is each image carrier. The same applies to a belt-shaped object passing through.

[Effect]

As described above, the nipping of the transfer material on the transfer material support is completed before the latent image formation on the image carrier, and the speed fluctuation due to the transfer material support side is eliminated after the latent image formation is started. Accurate image registration has become possible, and it has become possible to obtain high-quality color images without color misregistration.

As the developer for developing the image bearing member, a one-component system using only a magnetic toner is also effective in addition to a two-component system having a toner and a carrier.

[Brief description of drawings]

FIG. 1 is a sectional view of a photosensitive drum and a transfer drum to which the present invention is applied, FIG. 2 is a perspective view of the photosensitive drum, the transfer drum and a driving unit, and FIG. 3 is an axial sectional view of the photosensitive drum and the transfer drum. FIG. 4 is a block diagram of drive control of the photosensitive drum and the transfer drum, and FIG. 5 is a sectional view of a transfer type color electrophotographic image forming apparatus having the photosensitive drum and the transfer drum. In the figure, 1 is a photosensitive drum, 4 is a transfer drum, 8 is a transfer portion, 9 is a transfer charger, 13 is a gripper, and 24/28.
Is a motor, and P is a transfer material.

Claims (1)

[Claims] 1. A movable transfer material support for supporting a transfer material for sequentially transferring a color toner image onto a transfer material after developing a latent image formed on the image support with color toner, A transfer material support provided with a gripping means for gripping the transfer material,
A color image forming apparatus having a detection means for detecting the transfer material on the transfer material support after the transfer material is gripped by the gripping means, and at the same time as the detection means detects the transfer material, or After that, the latent image formation of the image carrier is started, and the color image forming apparatus is characterized.