JPH04122955A - Image forming device - Google Patents

Abstract

PURPOSE:To eliminate the occurrence of twist, loosening and curvature, etc., at the time of assembling works, also to eliminate unevenness caused by an environmental factor and to prevent the occurrence of defective suction and deviation in a sucking position by straining a transfer material holding member in the shaft direction of a transfer device and giving the degree of freedom thereto to some extent while preventing deviation in a rotating direction. CONSTITUTION:A transfer material fed to the transfer device is sucked and held by the transfer material holding member 34, and a toner image on a photosensitive drum is transferred on a transfer material. The member 34 is a film-like dielectric sheet, and elastic members 61a and 61b and rigid members 60a and 60b are made to adhere on the lower side of the end parts 34a and 34b on the one side of the member 34, and screw holes 62a and 62b are provided. Then, slots 63 for positioning are provided on both edge parts. A drum frame 30D is constituted of columnar rings 70a and 70b, and a tie plate-like connecting member 71, and tap holes 71a are provided on the member 71. Furthermore, tension rings 72a and 72b provided with a projection 73 for positioning and a tension spring 74 are provided on the rings 70a and 70b. The holes 62a and 62b and the hole 71a are screwed up so as to wind and mount the member 34 around the drum frame 30D. At this time, the projection 73 is adjusted to the slots 63.

Description

DETAILED DESCRIPTION OF THE INVENTION First aspect of the present invention is to transfer a developed image (toner image) on an image carrier formed by an electrophotographic method or an electrostatic recording method to a transfer material holding member of a transfer device. This invention relates to an image forming apparatus that obtains an image by transferring an image to a transfer material supported on a flexible transfer material holder, and particularly relates to a transfer device of an image forming apparatus, and more specifically, it relates to an image forming apparatus that obtains an image by transferring an image to a transfer material supported on a flexible transfer material holder. This is characterized by a transfer device that performs transfer using the same method.

BACKGROUND ART Conventionally, various transfer devices have been proposed and put into practical use based on electrophotographic techniques and the like for transferring a developed image formed on an image bearing member such as an electrophotographic photoreceptor to a transfer material. In particular, in a transfer device that holds the transfer material on an endlessly moving transfer material holding member and performs transfer by applying transfer corona discharge from the back side of the transfer material holding member, multiple transfers onto the transfer material can be performed effectively. Therefore, it is extremely suitable for color image formation.

When forming a color image, it is particularly necessary that the image carrier and the transfer material are in uniform contact with each other to prevent transfer defects.

For this purpose, the transfer device generally has a cylindrical transfer drum 30D with a cutout opening 30a, as shown in FIG.
is wound to form a transfer material holding member, and the cylindrical transfer drum 30D is configured to rotate in synchronization with an image carrier such as a photosensitive drum.

Further, the sheet-like insulator 34 is attached near the four sides of the opening 30a on the outer peripheral surface of the cylindrical transfer drum 30D using double-sided tape or the like.

However, when pasting the four sides of the sheet-like transfer material holding member 34 to the transfer drum opening 30a, it is necessary to make sure that the sheet-like transfer material holding member 34 is not loose, bent, or tilted. This is extremely difficult and time consuming. In other words, workability is poor.

Further, the transfer drum 30D, as shown in FIG.
A pair of ring-shaped rotating members 30 spaced apart from each other
b, 30b and a band-shaped connecting member 30c,
Since the sheet-like transfer material holding member 34 is bonded to its outer surface, twisting, loosening, bending, etc. may occur in the transfer material holding member 34 during assembly work, and the transfer material holding member 34 attached in a cylindrical shape may This causes unevenness on the surface. These unevenness not only cause poor suction and misalignment of the suction position when the transfer material is carried by the transfer material holding member 34, but also cause misalignment of the transfer position of the toner image on the image carrier onto the transfer material for each color rotation. There were drawbacks such as image color shift and unevenness of the image due to poor transfer, as well as missing images in the transfer.

Therefore, an object of the present invention is to tension the transfer material holding member provided in the transfer device in the axial direction of the transfer device, and to provide a certain degree of freedom in the rotational direction while preventing the transfer material holding member from shifting. This prevents twisting, loosening, bending, etc. of the transfer material holding member during assembly work (and also eliminates unevenness of the transfer material holding member caused by environmental factors, thereby preventing poor suction and misalignment of the suction position). It is an object of the present invention to provide an image forming apparatus which can always obtain a good image by eliminating image color shift due to transfer position shift and image unevenness/image transfer missing due to transfer failure.

in order to The above object is achieved by an image forming apparatus according to the present invention.

To summarize, the present invention provides an image forming apparatus that forms a developed image on an image carrier and obtains an image by transferring the developed image to a transfer material supported on a transfer material holding member of a transfer device. a ring-shaped rotating member disposed on both sides at a distance from each other to support the transfer material holding member; The present invention includes means for tensioning the material holding member in the axial direction of the transfer device, and means for preventing and regulating the transfer material holding member from shifting in the rotational direction of the transfer device while giving a slight degree of freedom. This is an image forming apparatus with features.

Support 13 Next, the image forming apparatus according to the present invention will be described in more detail with reference to the drawings.

FIG. 8 shows an embodiment in which the image forming apparatus according to the present invention is implemented in a color electrophotographic apparatus.

In this embodiment, an image bearing member, that is, an electrophotographic photosensitive drum 1 which is rotatably supported and rotates in the direction of the arrow, is provided with a - wide charger 2;
The electrostatic latent image is formed on the photosensitive drum 1 by uniformly charging the photosensitive drum 1 and irradiating the photosensitive drum 1 with a light image 3 according to image information using an exposure means such as a laser beam exposure device. The electrostatic latent image is visualized as a developed image, that is, a toner image, on the photosensitive drum 1 by, for example, the mobile developing device 4.

The mobile developing device 4 includes four developing devices 4M and 4C14Y each housing four color developers: magenta developer, cyan developer, yellow developer, and black developer.
, 4B, and a guide (not shown) that holds these four developing devices and is movable in the horizontal direction. The mobile developing device 4 transports a desired developing device to a developing position facing the outer peripheral surface of the photosensitive drum 1, and develops the electrostatic latent image on the photosensitive drum.

The visible image, that is, the toner image, on the photosensitive drum 1 is carried by a transfer device 30, which will be described in detail later, and is conveyed by the transfer device 30 in the direction of the arrow in the figure.Then, a transfer material is brought into contact with the photosensitive drum 1. Transferred to P. The transfer material P is transferred to the transfer device 30 in synchronization with the image by the registration rollers 6a.
supplied to.

After the residual toner on the surface of the photosensitive drum 1 is cleaned by a cleaning device 20, the photosensitive drum 1 is subjected to a color image process again.

Furthermore, to explain the transfer device 30, the transfer device 30
has a transfer material adsorption means 50 for adsorbing and holding the transfer material P fed to the transfer device 30 on the sheet-like transfer material holding member 34. The transfer material adsorption means 50 is provided inside the transfer drum 30D, as shown in FIG. It has an adsorption corona charger 51 and a conductive roller 52 provided outside the transfer drum 30D. This conductive roller 52 is grounded,
It serves as a counter electrode of the adsorption corona charger 51, and functions to inject charges into the transfer material P and cause the transfer material P to be electrostatically attracted to the transfer material holding member 34.

The transfer material P attracted by the transfer device 30 is transferred to the transfer charger 1
In order to transfer the first color developer, for example magenta toner, on the photosensitive drum 1 to the first transfer material P, the toner is transferred to the back surface of the transfer material holding member 34. Corona charger 15 for transferring charges of opposite polarity to
Give using. By the time the first transfer material comes to the position of the conductive roller 52 for the second time, the conductive roller 52 is released,
A position that does not disturb the toner image transferred onto the transfer material P, for example, is spaced outward from the transfer material holding member 34 by 2 mm or more.

Next, a second color toner image formed on the photosensitive drum l in synchronization with the first transfer material to which the first color toner image has been transferred is transferred to a second color toner image using a transfer corona charger 15. The toner image of the second color is transferred onto the second transfer material P, and the toner image of the second color is also transferred to the second transfer material to which the toner image of the first color has been transferred. Thereafter, toner images of four colors are transferred to the transfer material P in the same manner.

The transfer material P onto which the four-color toner images have been transferred is separated from the transfer device 30 by the static eliminating/separating charger 16.54 and the separating claw means 40, and is conveyed to the fixing device 18.

An embodiment of a transfer device 30 constructed according to the present invention will be described with reference to FIGS. 1 to 4.

FIG. 1 shows a transfer material holding member 3 used in a transfer device 30.
An example of No. 4 is shown below. In this embodiment, the transfer material holding member 3
4 is usually a film-like dielectric sheet such as polyethylene terephthalate or polyvinylidene fluoride resin film, and has an elastic member 61a formed of foamed urethane or rubber on the lower side of one end 34a; A rigid member 60a, such as a metal plate, is adhered to each other with double-sided tape or the like, and a hole for screwing and a counterbored hole for hiding the screw head are provided through the elastic member 61a and the rigid member 60a. is processed. Further, a similar elastic member 61b and a rigid member 60b are also provided at the opposite end 34b.
are glued in the same order.

Furthermore, the transfer material holding member 34 is provided with screw escape holes 62a and 62b at both ends thereof, coinciding with the screw holes, and positioning elongated holes 63 at both end edges.

On the other hand, as shown in FIG. 2, the transfer device 30 includes ring-shaped rotating members, that is, cylindrical rings 70a and 70b, which are provided on both sides at a distance from each other, and the rings 70a and 70.
The connecting member 71 is provided with a tapped hole 71a for fixing the transfer material holding member 34, and constitutes the drum frame 30D. Furthermore, according to the present invention, the rings 70a and 70b have tensioners having protrusions 73 for positioning the transfer material holding member 34.
') 'j 72a, 72b and a tension spring 74 are provided.

In order to wind the transfer material holding member 34 around the drum frame 3dD, the screw holes formed at both ends of the transfer material holding member 34 and the taps of the connecting member 71 are used. Fix 71a with screws. At that time, the protrusions 7 of the tension rings 72a, 72b
3 and the positioning elongated hole 63 of the transfer material holding member 34 to form a cylindrical shape as shown in Sections 3 to 4.

According to this embodiment, the transfer material holding member 34 has a ring 70.
(70a, 70b), but can be wound in a tensioned state by the tension ring 72 and tension spring 74 without causing any slack, bending, or inclination during winding. The transfer material holding member 34 can always be replaced with a predetermined tension state regardless of the skill level of the operator, and workability can be improved.

Further, when the transfer material holding member 34 is cleaned by a cleaning roller 55 after separating the transfer material P from the transfer device 3o as shown in FIG.
6, it is necessary to be pushed outward by the tension ring 72, and it is necessary to be slightly lifted from the tension ring 72, and it is also necessary to be pressed toward the photosensitive drum 1 in the transfer section, so that it is locally pushed. must have degrees of freedom. In order to provide the transfer device 3o with flexibility in the circumferential direction and tension in the axial direction, according to the present invention, the positioning hole 63 of the transfer material holding member 34 is elongated in the winding direction. It is round and large in shape.

With such a configuration, distortion of the transfer material holding member 34 due to temperature and humidity factors can also be absorbed.

As described above, according to the transfer device of this embodiment, the unevenness and expansion/contraction of the transfer material holding member 34 will not occur in the axial direction of the transfer device 30. Furthermore, in the circumferential direction of the transfer device 3o, the elastic member 61 of the transfer material holding member 34 expands and contracts, and the elongated circular hole of the positioning hole 63 of the transfer material holding member 34 corresponds to the positioning protrusion of the tension ring 72. By being able to move in the circumferential direction with respect to 73, there is an effect similar to that in the axial direction.

Alternatively, in the above configuration, the ends 34a, 34b (1') of the transfer material holding member 34 are rigid bodies tYt460a
, 60b are formed into elongated round holes extending in the axial direction of the transfer device 3o, and the ends of the transfer material holding member 34 are fastened with step screws. If the tension ring 72 and the tension spring 74 are allowed to move in the axial direction, the same effect as described above can be obtained using only one side of the tension ring 72 and the tension spring 74.

5 to 7 show other modified embodiments of the invention.

FIG. 5 shows another modified embodiment of the transfer material holding member 34. In FIG.

The structure of the end portions 34a and 34b of the transfer material holding member 34 is the same as that of the previous embodiment, but instead of the long holes 63 formed at both end edges of the transfer material, in this embodiment, the transfer material holding member 340 is different in that side elastic members 64 made of urethane foam or rubber are adhered to both end edges with double-sided tape or the like.

On the other hand, the structure of the frame 30D of the transfer device 30 is also manufactured in substantially the same manner as in the above embodiment described in connection with FIG.
a, 72b, and a tension spring 74, but in this embodiment, a tension ring? 2a,? The surface of 2b in contact with the transfer material holding member 34 is recessed in the radial direction by the thickness of the side elastic member 64, and the tension ring 72a,
The protrusion 73 in the previous embodiment is not formed on the surface of 72b.

In order to wrap the transfer material holding member 34 of this embodiment around the drum frame 30D, as shown in FIG.
, 34b are fixed to the connecting member 7 with screws to form a cylindrical shape.

Also in this embodiment, the transfer material holding member 34 is the ring 7.
0 (70a, 70b) is not directly bonded,
It is held on the drum frame 30D by a tension ring 72 and a tension spring 74, and the tension ring 72
By using the tension spring 74 and the tension spring 74, winding can be carried out in a tensioned state without causing slack, bending, or inclination during winding. Therefore, regardless of the skill level of the assembler, it is possible to replace the transfer material holding member 34 while maintaining a predetermined tension, thereby improving workability.

Furthermore, the degree of freedom of the transfer device 30 in the circumferential direction is obtained locally by the side elastic members 64, and no transfer position shift occurs. This eliminates the occurrence of unevenness and expansion/contraction of the transfer material holding member 34 due to temperature and humidity factors, and the same effects as in the above-mentioned embodiments can be obtained.

In the above configuration, similarly to the above embodiment, the screw holes in the rigid members 60a and 60b of the transfer material holding member 34 are made into elongated holes in the axial direction of the transfer device 30, and are fastened with stepped screws.
By providing a degree of freedom, the tension ring 72 and the tension spring 74 can achieve the same effect with only one side.

As described above, in the image forming apparatus according to the present invention, the transfer material holding member provided in the transfer device is tensioned in the axial direction of the transfer device, and the transfer material holding member provided in the transfer device is tensioned in the rotational direction. In order to have a structure that provides a certain degree of freedom while preventing misalignment, it is necessary to eliminate twisting, slack, bending, etc. of the transfer material holding member during assembly work, and to prevent unevenness of the transfer material holding member due to environmental factors. By doing so, it is possible to prevent poor suction and misalignment of the suction position, eliminate image color shift due to misalignment of transfer position, and eliminate image unevenness and missing image transfer due to poor transfer, so that good images can always be obtained.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of one embodiment of a transfer material holding member of a transfer device constructed according to the present invention. FIG. 2 is a perspective view of an embodiment of a transfer drum for a transfer device constructed according to the present invention. FIG. 3 is a perspective view of one embodiment of a transfer device constructed in accordance with the present invention. FIG. 4 is a sectional view of the transfer device of FIG. 3. FIG. 5 is a perspective view of another embodiment of the transfer material holding member of the transfer device constructed according to the present invention. FIG. 6 is a perspective view of another embodiment of a transfer device constructed in accordance with the present invention. FIG. 7 is a sectional view of the transfer device of FIG. 6. FIG. 8 is a schematic diagram of an embodiment of the image forming apparatus of the present invention. FIG. 9 is a perspective view of a conventional transfer drum for a transfer device. 34: Transfer material holding members 61a, 61b: Rigid members 60a, 60b: Elastic members 64: Side elastic members 70a, 70b: Ring-shaped rotating member 72: Tension ring 74: Tension spring Kukoji/Fig. 3, Fig. 4 Figure 5 Figure 7 Figure 8

Claims (1)

[Claims] 1) In an image forming apparatus that forms a developed image on an image carrier and obtains an image by transferring the developed image to a transfer material supported on a transfer material holding member of a transfer device, the transfer device a ring-shaped rotating member disposed on both sides separated from each other to support a holding member; and a ring-shaped rotating member disposed on at least one of the ring-shaped rotating members and engaged with the transfer material holding member to transfer the transfer material holding member. An image forming apparatus characterized by having means for tensioning the apparatus in the axial direction, and means for preventing displacement of the transfer material holding member in the rotational direction of the transfer apparatus and regulating it with a slight degree of freedom. Device.