JP3058822B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic system for transferring a visible image formed on an image carrier to a recording material on a recording material carrier to form an image. Related to an image forming apparatus.

[0002]

2. Description of the Related Art FIG. 7 shows an example of a conventional color image forming apparatus. In FIG. 1, the color image forming apparatus has a digital color image reader unit at the upper part and the printer unit at the lower part.

In the image reader section, the original 30 is placed on an original platen glass 31 and is exposed and scanned by an exposure lamp 32, so that a reflected light image from the original 30 is condensed on a full color sensor 34 by a lens 33 to form a color image. Obtain a decomposed image signal. The color-separated image signal is subjected to various processes in a video processing unit (not shown) via an amplification circuit (not shown), and then sent to a digital color image printer unit.

In a digital color image printer section,
The photosensitive drum 1, which is an image carrier, is a photosensitive body such as an organic photoconductor, and is rotatably carried in the direction of the arrow.
Around the photosensitive drum 1, in the order of its rotation, a pre-exposure lamp 11, a primary corona charger 2, a laser exposure optical system 3, a potential sensor 12, four developing devices 4y of different colors,
4c, 4m, 4bk, on-drum light amount detecting means 13, transfer device 5, and cleaning device 6 are arranged.

[0005] Pre-exposure lamp 11 and primary corona charger 2
In this case, a uniform amount of charge is applied to the surface of the photosensitive drum 1. Next, the image signal from the reader unit is converted by the optical system 3 into an optical signal for image scan exposure at the laser output unit (not shown), and the changed laser light is reflected by the polygon mirror 3a, and the lens 3b The light is projected on the surface of the photosensitive drum 1 via the mirror 3c.

At the time of image formation in the printing section, the photosensitive drum 1 is rotated in the direction of the arrow, and the photosensitive drum 1 after having been neutralized by the pre-exposure lamp 11 is uniformly negatively charged by the primary corona charger 2 so as to be disassembled. A light image E is emitted for each color to form a latent image.

Next, a predetermined developing device is operated to reversely develop the latent image on the photosensitive drum 1 to form a visible image, ie, a toner image, on the photosensitive drum 1 using a resin-based negative toner. The developing devices are eccentric cams 24y, 24c, 2
By the operation of 4 m and 24 bk, development is performed by selectively approaching the photosensitive drum 1 according to each separation color.

Further, the toner image on the photosensitive drum 1 is transferred from a recording material cassette 7 to a recording material supplied to a transfer position facing the photosensitive drum 1 via a transfer system and a transfer device 5.

The transfer device 5 includes a transfer drum 5a, a transfer charger 5b, an adsorption charger 5c for electrostatically adsorbing a recording material,
Suction roller 5g facing suction charger 5c, suction guide 5m for guiding the recording material to the suction position, suction guide mylar 5
1 and an inner charger 5d and an outer charger 5e.

The structure of the transfer drum 5a will be described in detail with reference to FIG. The transfer drum 5a includes a pair of disk members 5q.
And a shaft member 5s for completely connecting the centers thereof and a connecting member 5r for mechanically connecting a part of the outer periphery of the disk member 5q.
And a transfer sheet 5f, which is a recording material carrier, stretched in the peripheral opening area, are integrally formed in a cylindrical shape. As the transfer sheet 5f, for example, a polycarbonate film or the like having a thickness of 150 μm is used.

During image formation, a patch image having a constant density is developed on the photosensitive drum 1 at a position facing the connecting member 5r of the transfer drum 5a, and the density of the patch image is determined by a sensor (not shown). The image density is read and calculated by a CPU (not shown), and image density control for keeping the image density constant is performed.

The reason why the patch image is formed on the photosensitive drum 1 at a position corresponding to the connecting member 5r is that the patch image is formed during the image formation on the recording material, so that the patch image is formed on the transfer drum 5a. This is because it is necessary to form a patch image at a position where the recording material to be absolutely not placed.

On the other hand, the recording material is transferred from the cassette 7 to the transfer device 5.
Paper. Here, the suction roller 5g is brought into close contact with the transfer sheet 5f by a driving source (not shown), and
Attraction current (charge) is injected from c. Suction roller 5g
Is electrically grounded, the current (charge) in the opposite direction (reverse polarity) to the current (charge) injected by the adsorption charger 5c
Is induced (induced), and as a result, the recording material P is electrostatically attracted to the transfer sheet 5f.

When the recording material is supplied to the transfer position by the transfer sheet 5f, the toner is transferred one by one to the recording material by the transfer charger 5b in synchronization with the above-described color separation toner image.

Since only one color image is formed in one image forming process, the color separation process of the original is performed by the number of toner colors, that is, yellow (Y), magenta (M), and cyan (C). , Black (K) four times, and in the same manner, in synchronism with each color separation, latent image formation, development, and transfer corresponding to each color component are repeated to form a full-color image.

In the case of forming a full-color image, when the transfer of the toner images of four colors is completed in this way, the recording material is separated from the transfer drum 5a by the action of the separating claw 8a, the separating push-up roller 8b and the separating charger 5h. Then, the toner image on the recording material is mixed and colored in this fixing step and discharged to the tray 10 to complete one full-color copy.

On the other hand, after the transfer, the photosensitive drum 1 is subjected to an image forming process again after cleaning the residual toner on the surface with a cleaning device 6.

When images are formed on both sides of a recording material,
Immediately after the recording material exits the fixing device 9, the conveyance path switching guide 19 is driven, and once guided to the reversing path 21a via the conveying vertical path 20, the reversing roller 21b is reversed.
With the trailing end of the recording material sent to the reversing path 21 a as the head, the recording material is retracted in a direction opposite to the direction in which the recording material is sent, and is temporarily stored in the intermediate tray 31. Next, an image is formed again on the other surface of the recording material by the above-described image forming step.

Further, in order to remove the powder adhering on the transfer sheet 5f of the transfer drum 5a and the oil adhering to the recording material, a brush roller 14, a brush type static eliminator 15, an oil removing roller 16, and a transfer sheet 5f are used. The cleaning is performed by the backup brush 17 facing the removing roller 16. Such cleaning is performed before or after image formation,
Further, when a jam, that is, when a paper jam occurs, it is performed as needed.

The gap between the transfer sheet 5f and the photosensitive drum 1 can be arbitrarily set by operating the eccentric cam 25 at a desired timing and operating the cam follower 5i integrated with the transfer drum 5a. I have. For example, the interval between the transfer drum and the photosensitive drum can be increased during standby or when the power is off.

[0021]

However, in the above-mentioned prior art, in order to control the image density, the image density on the image carrier is reduced.
The patch image developed at the position corresponding to the connecting member of the transfer device is electrostatically attracted to the connecting member in the transfer section, and stains the recording material carrier of the transfer device, and as a result, stains the recording material. There was a problem that it would.

Accordingly, an object of the present invention is to provide an image forming apparatus capable of preventing a recording material carrier and a recording material from being stained by a patch image.

[0023]

The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention provides:
It has an image carrier on which a visible image is formed, a pair of disk members, a connecting member connecting the disk members, and a cylindrical member formed in the peripheral opening formed by the disk member and the connecting member. An image forming apparatus that has a transfer device including a recording material carrier that carries and conveys a recording material, and that forms an image on the image carrier at a position facing the connecting member.
An image forming apparatus, wherein at least a part of a portion of the connecting member facing an image formed on the image carrier is separated from the recording material carrier via a dielectric.

Preferably, the dielectric is filled in a concave portion provided in the connecting member.

According to another aspect of the present invention, there is provided an image carrier on which a visible image is formed, a pair of disk members, a connecting member connecting the disk members, the disk member and the disk member. It is stretched cylindrically in the peripheral opening area formed by the connecting member,
An image forming apparatus having a transfer device including a recording material carrier for carrying and transporting a recording material, and forming an image on the image carrier at a position facing the coupling member; An image forming apparatus is provided in which at least a part of a portion facing an image formed on the carrier is separated from the recording material carrier via an air layer.

The air layer may be present in a recess provided in the connecting member. The image formed on the image carrier at a position facing the connecting member is a patch image formed for adjusting the density of the output image.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image forming apparatus according to the present invention will be described in more detail with reference to the drawings. In the embodiment described below, the present invention is embodied in the color image forming apparatus shown in FIG. Therefore, the description of the overall configuration and functions of the color image forming apparatus will be omitted, and the features of the present invention will be described.

Embodiment 1 A transfer device which is a feature of the present invention will be described with reference to FIGS. The transfer device 5 disposed opposite to the photosensitive drum 1 serving as an image carrier has a transfer drum 5a which is rotatably supported and rotatably driven.
And a transfer charger 5b is disposed opposite to the transfer charger 5b.

The transfer drum 5a includes a pair of disk members 5q,
5q, a shaft member 5s penetrating and connecting the centers thereof,
A connecting member 5r for mechanically connecting a part of the outer peripheral portion of the disk member 5q and a transfer sheet 5f as a recording material carrier stretched over the peripheral opening area are integrally formed in a cylindrical shape. Have been. The transfer sheet 5f has a thickness of 150 μm in this embodiment.
m of polycarbonate film is used. Note that the transfer sheet 5f may be a dielectric such as PET or polyvinylidene fluoride, and the thickness is not particularly limited.

The region of the connecting member 5r opposite to the position where the density control patch is formed on the photosensitive drum, that is, the portion shown by hatching in FIG. 5a is formed as a concave portion 50 depressed in the center direction,
The depth is set to d = 300 μm. The recess 50 is filled with polycarbonate 51, which is the same member as the transfer sheet 5f, as a dielectric.

With the above arrangement, the transfer of the patch image on the photosensitive drum to the transfer sheet 5f can be prevented, and the contamination of the recording material, which has been a conventional problem, can be prevented.

The reason why the recording material can be prevented from being stained by separating the connecting member and the transfer sheet via the dielectric material as described above is considered as follows.

FIG. 2 shows a conventional transfer section, and FIG. 3 shows a transfer section of the present embodiment in a sectional view (a) and a model circuit diagram (b) corresponding to the same.

[0034] In both figures, C ₁ represents the gap between the transfer sheet 5f and the photosensitive drum 1, C ₂ represents the transfer sheet 5f, C ₃ represents the gap between the coupling member 5r and the transfer sheet 5f.

When the toner on the photosensitive drum is transferred onto the transfer sheet, the force acting on the toner is represented by the potential difference V at both ends of C _1.
It is proportional to ₁ . 2 (b) and 3 (b) have the same potential difference V as a whole. Further when the toner has a Q charge given to C _1, the charge Q is also constant.

In the model circuit diagrams of FIGS. 2B and 3B, V ₂ = Q / C ₂ ... (1) V ₂ ′ = Q / C ₂ + Q / C _3. According to the above equations (1) and (2), V ₂ ′> V ₂ . Furthermore, a _{V = V 1 + V 2 =} V 1 '+ V 2' ··· (3), V is because it is constant, the V _1> V ₁ '.

As described above, by providing the concave portion 50 in the connecting member 5r, the potential difference V ₁ ′ between the photosensitive drum 1 and the transfer sheet 5f in the present embodiment is smaller than the potential difference V ₁ in the conventional example.
_{1, the} force acting when the toner on the photosensitive drum is transferred onto the transfer sheet is reduced, and therefore,
It is considered that the transfer sheet can be prevented from being stained by the toner.

In this embodiment, polycarbonate is used as the filler for the concave portions. However, the same effect can be obtained by using other dielectric materials such as PET and polystyrene.

Second Embodiment Next, a description will be given of a transfer apparatus according to a second embodiment of the present invention with reference to FIG.

In the first embodiment, a concave portion is formed in a region of the connecting member corresponding to a position on the photosensitive drum where a density control patch is to be formed, and the concave portion is filled with a dielectric polycarbonate. In this embodiment,
The feature of the first embodiment is that the recess in the first embodiment is simply an air layer.

As shown in FIG. 5, a concave portion 50 is formed in a region of the connecting member 5r corresponding to a position where a density control patch is formed on the photosensitive drum, and the concave portion 50 is used as an air layer.
The distance between the transfer sheet and the bottom surface of the concave portion 50 is d = 300 μ
m.

In such a configuration, as described in the first embodiment, the potential difference between the photosensitive drum 1 and the transfer sheet 5f in this embodiment can be made smaller than the potential difference in the conventional example. In addition, the recording material can be prevented from being stained.

Third Embodiment Next, a description will be given of a transfer apparatus according to a third embodiment of the present invention with reference to FIG.

In this embodiment, as shown in FIG.
A concave portion 50 is formed in a region of the connecting member 5 r corresponding to a position where a density control patch is formed on the photosensitive drum, and the concave portion 50 is completely covered with an insulating sheet 52.

The depth of the recess 50 was d = 300 μm, the insulating sheet 52 was a carbonate film, and the thickness was t = 100 μm. The same effect can be obtained with another material and thickness as long as the insulating sheet 52 has sufficient rigidity.

In this embodiment, similarly to the first and second embodiments, the transfer sheet and the recording material can be prevented from being stained by the toner, and the size of the gap between the transfer sheet and the connecting member due to distortion of the transfer sheet or the like can be reduced. Changes can be prevented.

In the first to third embodiments, the depth of the concave portion provided in the connecting member is set to 300 μm, but is set to 50 μm.
If it is above, the effect is recognized, and preferably, 150
μm or more.

[0048]

As is apparent from the above description, in the image forming apparatus according to the present invention, at least a part of the portion of the connecting member facing the image formed on the image carrier has the recording material carrier and the dielectric material. , The recording material carrier and the recording material can be prevented from being stained by the patch image, and a high-quality recording material can be provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a connecting member according to a first embodiment.

FIG. 2 is an explanatory view illustrating a concave portion of a transfer device and a connecting member according to the first exemplary embodiment.

3A and 3B are a cross-sectional view and a model circuit diagram of a transfer unit according to a conventional example.

FIGS. 4A and 4B are a cross-sectional view and a model circuit diagram of a transfer unit according to the first embodiment. FIGS.

FIG. 5 is a perspective view illustrating a connecting member according to a second embodiment.

FIG. 6 is a perspective view illustrating a connecting member according to a third embodiment.

FIG. 7 is a schematic configuration diagram illustrating an example of a conventional color image forming apparatus.

FIG. 8 is an explanatory diagram illustrating the transfer drum of FIG. 7;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photosensitive drum (image carrier) 5 transfer device 5a transfer drum 5f transfer sheet (recording material carrier) 5q disc member 5r connecting member 50 recess 52 insulating sheet

Continuation of the front page (56) References JP-A-9-90773 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/16

Claims (5)

(57) [Claims] An image carrier on which a visible image is formed,
A pair of disk members, a connecting member that connects the disk members, and a recording material that is cylindrically stretched over a peripheral opening formed by the disk member and the connecting member and carries and conveys the recording material An image forming apparatus, comprising: a transfer device having a carrier; and forming an image on the image carrier at a position facing the connecting member, wherein the image of the connecting member is formed on the image carrier. An image forming apparatus, wherein at least a part of an opposing portion is separated from the recording material carrier via a dielectric. 2. The image forming apparatus according to claim 1, wherein the dielectric is filled in a concave portion provided in the connecting member. 3. An image carrier on which a visible image is formed,
A pair of disk members, a connecting member that connects the disk members, and a recording material that is cylindrically stretched over a peripheral opening formed by the disk member and the connecting member and carries and conveys the recording material An image forming apparatus, comprising: a transfer device having a carrier; and forming an image on the image carrier at a position facing the connecting member, wherein the image of the connecting member is formed on the image carrier. An image forming apparatus, wherein at least a part of a facing portion is separated from the recording material carrier via an air layer. 4. The image forming apparatus according to claim 3, wherein the air layer exists in a concave portion provided in the connecting member. 5. An image formed on the image carrier at a position facing the connecting member is a patch image formed to adjust the density of an output image. An image forming apparatus according to any one of 1 to 4.