JP3072780B2 - 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 image forming apparatus for obtaining an image by transferring a visible image formed on an image carrier by an electrophotographic or electrostatic recording method to a transfer material by a transfer device. Yes, particularly suitable for a multi-color image forming apparatus having a plurality of developing units, developing a latent image formed on an image carrier, and sequentially transferring the toner image onto a transfer material by a transfer device to obtain an image. It can be embodied in

2. Description of the Related Art Conventionally, various multicolor image forming apparatuses have been proposed and are commercially available. FIG. 6 shows an example of a typical color electrophotographic copying machine.

In FIG. 6, a color electrophotographic copying machine is
As will be described in detail later, in this example, a latent image is formed on the image carrier 1 which is an electrophotographic photosensitive drum, and the latent image is formed into a plurality of developing units 132 to yellow, magenta, cyan, and black. The toner image is formed into a color toner image by the rotary developing device 13 provided with 134, and these toner images are superimposedly transferred onto a sheet-like transfer material such as paper attached to a drum-shaped transfer device 5 disposed close to the surface of the photosensitive drum 1. To obtain a color image.

As schematically shown in FIG. 7, a transfer device 5 used in such a color electrophotographic copying machine has a pair of annular members, in this example, cylindrical members 5a and 5b concentrically arranged. Then, both are integrally connected by the connecting member 5c,
Further, a transfer material supporting member usually formed of a dielectric material such as a polyester sheet, that is, a transfer drum formed in a cylindrical shape by covering with a supporting sheet 15 is used over the entire circumference.

Further, a gripper 51 is provided at an appropriate position on the outer surface of the connecting member 5c of the transfer drum 5, and the transfer material supplied in time with the toner image on the photosensitive drum 1 is gripped and transported. The toner image of each color is transferred to a transfer material each time the toner image approaches the photosensitive drum 1 at a transfer position where the transfer charger 24 is disposed, and a color image is formed.
Is released to separate the transfer material from the transfer drum. The separated transfer material is fed to the fixing unit 30 by the conveying unit 29.

Conventionally, in the transfer drum 5, in order to make the carrier sheet 15 uniform and to increase the transfer nip to increase the transfer efficiency, the photosensitive drum 1 is located near the transfer charger 24 from the inside of the transfer drum 5. As shown in FIGS. 8 to 10, a backup member 61 is provided to push up the support sheet 53 in the direction of FIG. The backup member 61 is made of a flexible material such as Mylar (trade name) or applies an appropriate pressure to the support sheet 15 by a rigid body fixed through an elastic body (such as a torsion coil spring).

[0007]

However, in the transfer apparatus having such a structure, the connection member 51 is moved as shown in FIG.
At the moment when the backup member 61 that presses the connection member 51 comes out of the connecting member 51 and becomes a state as shown in FIG. 10, the backup member 61 strikes the support sheet 51 from the inside and gives an impact. The vibration due to the impact shakes the pressed photosensitive drum 1 to cause image blurring.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide an image forming apparatus in which a backup member prevents an impact on a transfer material carrying means. . Another object of the present invention is to provide an image forming apparatus that prevents vibration and prevents image blurring.

[0009] The present invention is a movable transfer material holding means for holding a transfer material, comprising: a pair of annular members; a connecting member connecting the pair of annular members; A transfer material supporting means comprising: a transfer material supporting sheet that covers an opening formed by the member and the connecting member and supports a transfer material; and a transfer material supporting sheet provided inside the transfer material supporting sheet and having the transfer material supporting sheet disposed outside. A pressing member that presses the transfer member on the transfer member supporting sheet in a moving direction of the transfer material supporting unit. A flexible sheet provided at a rear end of the transfer member, the flexible member being capable of contacting the transfer material supporting sheet, and the pressing member is configured to transfer the flexible sheet from the connecting member by the movement of the transfer material supporting means. Material carrying The transfer material carrying sheet is brought into contact with the transfer material carrying sheet via a position where the transfer material carrying sheet is in contact with the sheet.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image forming apparatus according to the present invention will be described with reference to the drawings.

As shown in FIG. 1, in the image forming apparatus, a charger 31 and a laser exposure device 32 are arranged around an image carrier 1 such as a cylindrical electrophotographic photosensitive member. An electrostatic latent image corresponding to the color of the developer is formed on the image carrier 1 by a normal electrophotographic process using the exposure device 31 and the exposure device 32. Each electrostatic latent image is
Developing unit 3 having different color toners as developer
Each of the toner images is developed by a developing device 33 including 3Y, 33M, 33C, and 33B, and is visualized on the image carrier 1 as a toner image of each color.

On the other hand, a transfer material P such as transfer paper is supplied from a cassette (not shown) to a transfer drum 5 as a transfer device by supply means 34.

As shown in FIG. 7, the transfer drum 5 includes at least a pair of front and rear annular members 5a and 5b concentrically arranged, and these flange members 5a and 5b.
b, a rigid supporting frame including a connecting member 5c which is a connecting member for connecting b, and a supporting frame covering the cut-out cylindrical opening surface except for the flange members 5a, 5b and the connecting member 5c. And a transfer material carrying sheet 15 which is a flexible transfer carrying member made of a dielectric film supporting and supporting the transfer material P. Further, the transfer drum 5 of the present embodiment may or may not be provided with the gripper 51 for gripping the transfer material P.

The transfer material P is conveyed to the transfer material suction position of the transfer drum 5 by the registration roller pair 35 of the transfer material supply means 34 in synchronization with the image forming timing on the image carrier 1. An adsorption charger 36 is arranged in the transfer drum 5 and electrostatically adsorbs the transfer material P onto the transfer material carrying sheet 15. A grounded conductive conductive roller 37 serving as a counter electrode is disposed at a position opposite to the adsorption charging device 36 with the transfer material carrying sheet 15 interposed therebetween, thereby increasing the effect of increasing the adhesion of the transfer material P during adsorption. I have.

The transfer material P adsorbed and carried on the transfer material carrying sheet 15 comes into contact with the image carrier 1 as the transfer drum 5 rotates. Then, a charge having a polarity opposite to that of the toner is applied to the back surface of the transfer material carrying sheet 15 by a transfer charger 24 which is a transfer means disposed in the transfer drum 5, so that the toner image on the image carrier 1 is transferred. Transcribed on P. A backup member 61 is disposed upstream of the transfer charger 24, and functions so that the transfer material carrying sheet 15 is uniformly pressed against the image carrier 30. The backup member 61 is made of a flexible dielectric sheet such as Mylar, and is located in the discharge area of the transfer charger 24 in order to regulate the transfer charge by the transfer charger 24 before the transfer, and the moving direction of the transfer drum 5. In the forward direction (the angle α formed between the backup member 61 and the line upstream of the contact portion among the tangent lines of the support sheet 15 at the contact portion of the backup member 61 with the support sheet 15).
Is an acute angle).

By performing the above-described development and transfer processes on toner images of a plurality of colors, respectively,
The toner images for each color are sequentially multiplex-transferred, and a color image is reproduced on the transfer material P.

The transfer material P on which the toner images of a plurality of colors have been superimposedly transferred as described above is used as a pair of static eliminators disposed opposite to each other with the sheet 15 interposed therebetween in order to reduce the attraction force to the transfer material carrying sheet 15. The AC is removed by the charger 39, and the separation claw 4 is removed.
0 is inserted between the transfer material P and the transfer material carrying sheet 15 to be separated from the sheet 15. The separated transfer material P is sent to the heat fixing device 41, where the toner image is melt-mixed and color-fixed, and then discharged to a tray (not shown).

After the transfer, the image carrier 30 is cleaned by a cleaning device 42 to remove residual toner on the surface, and then subjected to the color image forming process again.

Next, FIG. 2 shows an example of the vicinity of the transfer portion of the image forming apparatus of the present invention, which will be described. Connecting member 5
c at the downstream end in the moving direction of the transfer drum 5
_A cushioning flexible sheet 5d made of Mylar (trade name) is affixed to the inner surface thereof. Since the leading end of the flexible sheet 5 d is attached so as to contact the sheet 15, the backup member 61 passes through the connecting member 5 c by the movement of the transfer drum 5, and
Since the step at the time of collision with the sheet is slightly equal to the thickness of the flexible sheet 5d (about 0.1 mm), the image blur described above does not occur at all. Further, in order to prevent the impact on the carrying sheet 15 of the flexible sheet 5d by providing a flexible sheet 5d, it is not necessary to raise the positional accuracy and processing accuracy of the tapered portion 5c ₁ tip edge of the connecting member 5c Therefore, processing costs can be reduced.

FIG. 3 shows another example of the vicinity of the transfer portion of the image forming apparatus of the present invention.

A tapered portion 5 is provided at the downstream end of the connecting member 5c.
c ₁ is provided, and the buffering flexible sheet 5 ′ d is disposed on the inner surface thereof as in the embodiment of FIG. 2, but without attaching the flexible sheet to the tapered portion. Is attached to the flat surface 5e inside the connecting member 5c. Also,
Flexible inner corner portion 5c ₂ and the angle of the seat 5'd tapered portion is attached to bent to match the angle of the angle θ in a state where the flexible sheet 5'd is not given an external force Initially set to When the flexible sheet 5'd is attached to the flat surface 5e described above, the state shown by the two-dot chain line shown in FIG. At this time,
Compared to the angle of the tapered portion 5c ₁ of the connecting member 5c theta ₁ <
θ is set in advance. The flexible sheet 5'd by creating as its free length part 5'd ₁ is pressed against the holding of an elastic deformation amount of the force of the flexible sheet 5'd on _one side tapered portion 5c. Further, at this time, its free length part 5'd ₁ transfer drum 5
If the length is set so as to protrude by l _{[mm] from the} outer diameter (when there is no supporting sheet 15), the supporting sheet 15 is stretched by the transfer drum 5, and then the flexible sheet 5'd The angle becomes smaller (θ ₂ ) when the flexible sheet 5′d is pressed against the supporting sheet 15.

With such a configuration, the step when the flexible sheet 5'd passes through the connecting member 5c is more reliably than the embodiment of FIG. 2 (ie, even if the assembly precision and the component precision are not good). This is equivalent to the thickness of the flexible sheet 5'd. At this time, if the length l is sufficiently long, the flexible sheet 5 '
d makes the inclined surface gentle and the flexible sheet 5'd more reliably comes into contact with the supporting sheet 15, so that it is not necessary to increase the positional accuracy of the connecting member 5c with respect to the outer diameter of the transfer drum 5, and the processing cost is reduced. Can also be cheaper.

FIG. 4 shows a further example near the transfer section of the image forming apparatus of the present invention. The cushioning flexible sheet 5''d is attached to the flat surface 5e of the connecting portion 5c as in the embodiment of FIG. 3, but has no bent portion (the two-dot chain line is the initial state). Even with such a configuration, the same effect as the embodiment of FIG. 3 can be obtained. However, at this time, it is necessary to select the material or thickness of the buffering flexible sheet 5 ″ d that is easily deformed by the backup member 61.

In the embodiment shown in FIG. 3, a connecting member having a tapered portion is used. However, according to the embodiment shown in FIG. 4, a plate-like sheet metal can be used, so that the processing cost can be further reduced.

Also, as shown in FIG.
d '''' may be arranged in a short fence with a short width. Even with such a configuration, the same effect as when the connecting member 5c is provided extending in the longitudinal direction as shown in FIGS. 2 to 4 can be expected.

In this embodiment, the connecting member 5c is divided into four portions in the longitudinal direction, but the flexible sheet 5d "" is provided.
May be located at the center or two places at both ends.

According to experiments performed by the inventors of the present invention, the thickness of the flexible sheet shown in the above embodiments is 50 μm to 250 μm.
m was good.

Next, as a comparative example of the present invention, an example in which the above-mentioned flexible sheet is not provided will be described.

FIG. 11 is a cross-sectional view showing the vicinity of the transfer portion. The cross-sectional shape of the end face on the downstream side of the connecting member is tapered so that the backup member 61 gradually passes through the connecting member as the transfer drum moves. Is what you do. As shown in FIG. 11, it is difficult to reduce the radius R of the corner portion to 0 at the tip of the tapered edge, whether it is cut or formed, and if the connecting member has burrs, scratches, etc. A high-pressure leak current is generated from the transfer charging wire. Therefore,
As a practical limit, when the corner at the tip of the tapered edge portion is set to about R = 0.5 mm, a step as shown in FIG. 11 occurs. Further, if the edge portion of the connecting member is not sufficiently close to the supporting sheet, a step is further generated. Design) 0.
A relief of about 5 mm is required. That is, the impact of the backup member jumping from the step of about 1 mm between the connecting member and the carrying sheet (FIG. 11D) and colliding with the carrying sheet could not be completely removed, and the image blur was insufficient.

FIG. 12 also shows a cross-sectional view of the vicinity of the transfer section similarly to FIG. 11, but in the example of FIG. 12, the back side of the carrier sheet 15 where the backup member passes through the connecting member and collides with the movement of the transfer drum. , An elastic member made of rubber is arranged.

However, even in the example shown in FIG. 12, the step d in the rubber thickness portion remains inevitably, and conversely, as the thickness is reduced, the effect of reducing the impact is lost. Therefore, a step (d in FIG. 12) of about 1 mm is still necessary, and image blurring due to impact when the backup member passes through the rubber has occurred.

[0032]

As described above, according to the present invention,
Since it is possible to prevent shock and vibration generated when the pressing member passes through the connecting member, it is possible to prevent uneven movement and image blur of the transfer material carrying unit.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing one embodiment of an image forming apparatus of the present invention.

FIG. 2 is an enlarged cross-sectional view illustrating an example of the vicinity of a transfer unit of the image forming apparatus of the present invention.

FIG. 3 is an enlarged cross-sectional view illustrating an example of the vicinity of a transfer unit of the image forming apparatus of the present invention.

FIG. 4 is an enlarged cross-sectional view illustrating an example of the vicinity of a transfer unit of the image forming apparatus of the present invention.

FIG. 5 is a perspective view of the vicinity of a connecting portion of a transfer material carrying unit of the image forming apparatus of the present invention.

FIG. 6 is a sectional view of a conventional image forming apparatus.

FIG. 7 is a perspective view of a transfer drum.

FIG. 8 is a cross-sectional view near a conventional transfer unit.

FIG. 9 is a cross-sectional view near a conventional transfer unit.

FIG. 10 is a cross-sectional view near a conventional transfer portion.

FIG. 11 is an enlarged cross-sectional view illustrating a comparative example near a transfer portion of the image forming apparatus.

FIG. 12 is an enlarged cross-sectional view illustrating a comparative example near a transfer portion of the image forming apparatus.

[Explanation of symbols]

 Reference Signs List 1 photosensitive drum 5 transfer drum 5c connecting member 5d, 5d ', 5d ", 5d" "flexible sheet 15 support sheet 24 transfer charger 61 backup member

Claims (4)

(57) [Claims] 1. A movable transfer material holding means for holding a transfer material, comprising: a pair of annular members; a connecting member connecting the pair of annular members; and a pair of annular members and the connecting member. A transfer material supporting means for covering the opening to be formed and supporting the transfer material, and a pressing member provided inside the transfer material supporting sheet and pressing the transfer material supporting sheet outward. An image forming apparatus for transferring an image on an image carrier to a transfer material carried on the transfer material carrying sheet, provided at a rear end of the connecting member in a moving direction of the transfer material carrying means. A flexible sheet capable of contacting the transfer material carrying sheet, wherein the pressing member is located at a position where the flexible sheet comes into contact with the transfer material carrying sheet from the connecting member by movement of the transfer material carrying means; To An image forming apparatus characterized in that it is contact with the transfer material carrying sheet Te. 2. The flexible sheet presses the transfer material-carrying sheet outward so that the outside of the rear end of the connecting member does not contact the transfer material-carrying sheet. Image forming apparatus. 3. The flexible sheet has a thickness of 50 to 250.
The image forming apparatus according to claim 1, wherein the thickness of the image forming apparatus is μm. 4. An image forming apparatus according to claim 1, wherein a rear end of said connecting member has a tapered shape.