JPS6199170A - Transfer drum of copying machine - Google Patents

Abstract

PURPOSE:To execute satisfactory transfer by making use of the elasticity of a flexible dielectric film by tapering partly the ends of a drum for winding the flexible dielectric film so that a gap is made with said film. CONSTITUTION:The transfer drum 38 is a cylindrical wall consisting of the light transmittable/flexible dielectric film 3 wound around an offset cylinder consisting of the end parts 1 and connecting part 2 and made by aluminum molding. Electric charge is electrostatically charged to the surface so that recording paper 4 is kept attracted to the surface. The ends 1 of the offset cylinder on which the film 3 is wound are internally and partly tapered to width (a). The contact pressure between the recording paper 4 and a photosensitive surface 28 is obtd. by the elasticity of the film 3 and the width of the surface 28 is thoroughly assured by the width in the flexible part of the film 3. The strength of the offset cylinder is obtd. from the width over the entire part of the ends 1 including the tapered part.

Description

[Detailed description of the invention] ■Field of invention The present invention relates to a transfer drum in a color copying machine.

■Conventional technology In color copying machines, full-color coloring is achieved through additive color mixing, in which the original image is exposed to the three primary colors of paint, namely yellow, magenta, and cyan, and each color is developed and superimposed. ing. This is for example.

First, an original image is exposed to light on a photosensitive surface through a blue filter, which is a complementary color to yellow, to form an electrostatic latent image corresponding to the strength of the yellow component. Next, the original image is exposed to light on the photosensitive surface through a green filter, which is a complementary color to magenta, to form an electrostatic latent image corresponding to the strength of the magenta component, which is developed with magenta toner and visualized. After that,
Transfer the yellow toner image onto the same recording paper.

Furthermore, a cyan toner image is similarly transferred onto the same two recording sheets from above the yellow and magenta toner images through a red filter.

Therefore, in order to obtain one full-color copy, three exposure-visual-image-transfer steps are required, but the additive color mixture of these three color toner images was originally the same. Since the original image is separated into each component, they must be transferred to exactly the same position. Therefore, this type of color copying machine uses a transfer drum around which recording paper is wound. This is a drum on which recording paper is wound and fixed around a cylindrical wall whose circumference is equal to the circumference of the photoreceptor of the photoreceptor drum. The photosensitive surface of the photosensitive drum and the recording paper of the transfer drum are in light contact with each other at the transfer position, so that the transfer onto the recording paper can be performed while rotating synchronously in opposite directions. A perspective view of the photosensitive drum and the transfer drum is shown in FIG. 2a.

Generally, this type of transfer drum has means for fixing the ends of the recording paper, and also uses a dielectric material on the cylindrical wall to electrostatically attract the recording paper.

By the way, at the transfer position, if the contact pressure is insufficient and the recording paper floats off the photosensitive surface, the transfer will be defective, and if the contact pressure is too strong, it will come into pressure contact with the photoconductor, causing it to wrap around the photoconductor drum body. Problems such as peeling of the photoreceptor may occur. Furthermore, if the transfer drum is a rigid body (hereinafter used in the sense that the required elasticity cannot be obtained), the photosensitive surface will be damaged by the carrier mixed in during development, which will accelerate the deterioration of the photosensitive member.

As a solution to the above-mentioned inconvenience, JP-A-54-1975
There are 2 publications. In this method, a flexible dielectric film is wrapped around a cylinder cut out so that the annular ends are connected to both ends of a rod-shaped connecting part (hereinafter, such a cylinder is referred to as an offset cylinder) as a supporting frame. A transfer drum is disclosed. In this transfer drum, as shown in FIG. 2a, 1 is annular end portions at both ends, 2 is a connecting portion connecting these ends, and a flexible dielectric film 3 is wound around a support frame consisting of these. There is. When using an offset cylinder as a support frame for the transfer drum, the recording paper wrapper can be made of a flexible dielectric film, so its elasticity allows the photosensitive surface and the recording paper to come into contact with an appropriate contact pressure. can. Furthermore, even if carrier is mixed in during development, the force of the convex portion is absorbed by the elasticity of the dielectric film, and the photosensitive surface will not be damaged.

An ideal embodiment for fully exploiting the transfer drum advantages of such an offset cylinder would be one in which the width of the recording paper is wide, the photosensitive surface is wide, and the flexible portion of the transfer drum is wide.

In particular, the width of the flexible portion of the transfer drum must be sufficiently wide compared to the width of the photosensitive surface.In Figure 2a, Ql is the width of the recording paper and Ql is the width of the photosensitive surface. tQ3 is the width of the flexible portion of the transfer drum. FIG. 3 shows a sectional view taken along the line I C--I C of FIG. 2a when the above conditions are followed. As shown in FIG. 3, the recording paper 4 is brought into contact with the photosensitive surface 28 with an appropriate contact pressure due to the elasticity of the dielectric film. Further, since there is no unnecessary contact on the photosensitive surface 28, there is no cause for hastening the deterioration of the photosensitive member. However, in such an offset cylinder, the support frame elements that make up the drum shape are only two ends and a connecting part, which creates a strength problem, and the ends have a certain width in the cylindrical direction. will be required. Furthermore, if the width Ω3 of the flexible portion of the transfer drum cannot be made sufficiently wide, the bending force will be concentrated at point A, making it easy to break, so the thickness of the flexible dielectric film must be increased. Therefore, if this transfer drum is implemented in the ideal mode as shown in FIG. 3, the copying machine itself becomes too large, which is a major hindrance to miniaturization, cost reduction, etc.

Also, it is possible to downsize the cylinder by making the width of the notch close to the width of the recording paper, but the cross-sectional view in this case is shown in Figure 4.
As shown in the figure, as you can see, the width of the photosensitive surface Ω2〉
Since the width of the flexible portion of the transfer drum is Q3, the photoreceptor is pressed against the rigid portion of the transfer drum, resulting in peeling of the photosensitive layer.

This causes leakage during development. Also, the contact pressure.

The thickness of the recording paper is determined by the pressure-contacting portion, so the thickness of the recording paper is not completely absorbed by the bending of the flexible dielectric film. For this reason, the contact pressure increases near the edges, causing the edges of the recording paper to dig into the photoreceptor, while the contact pressure becomes insufficient near the center, resulting in transfer failure due to non-uniform contact pressure.

Due to these problems, it has been difficult to downsize the transfer drum using an offset cylinder.

(2) Purpose of the Invention The object of the present invention is to provide a transfer drum that can perform transfer by fully utilizing the elasticity of a flexible dielectric film and can be made into a four-type drum.

■Structure of the invention In order to achieve the above object, the present invention.

The width of the end of the offset cylinder is set to a width that provides sufficient strength, and a portion of the end around which the flexible dielectric film is wrapped is tapered to create a gap between the end and the flexible dielectric film. It can be so. 'According to this, the flexible dielectric film is wrapped around the cylindrical part at the end, but the flexible part is not at the convergence of the cutout part of the cylinder, but between the starting positions of the taper at the two ends. Therefore, a wider width can be obtained, and the ideal transfer drum under the above conditions can be miniaturized. Also, the strength of an offset cylinder can be obtained as the overall rigidity of the end, so
The transfer drum can be downsized.

In a preferred embodiment of the present invention, the offset
The taper of the cylinder is curved.

(1) Embodiment of the Invention FIG. 1 shows an outline of the mechanism of a color copying machine that embodies one embodiment of the present invention. A color copying machine separates the color image of a document into yellow, magenta, and cyan components and develops each color separately, so each copy is produced through approximately three times as many copying steps as a normal monochrome (black) copying machine. Complete the copy. For this reason,
The developing section is composed of approximately three times as many elements as a monochrome copying machine.

This will be explained below with reference to the drawings.

In FIG. 1, reference numeral 12 denotes a contact glass on which an original is placed, and the original is tightly pressed from above by a presser plate 10.

The document on the contact glass 10 is exposed to an exposure lamp 14 on the same carriage. The scanner 15, which includes the first mirror 16, etc., sequentially scans in the horizontal direction of the figure, and the reflected light is transmitted to the first mirror 16. Second mirror 18. Lens 20.
Third mirror 22. An image is formed on the photosensitive surface 28 of the photosensitive drum 27 via the fourth mirror 24 and the filter plate (26B in the figure) of the filter unit 26. During scanning by the scanner 15, the second
The mirror is driven in the scanning direction at 1/2 the speed of the scanner 15, and is driven back after scanning. These optical systems are driven by an optical system drive motor 58.

The filter unit 26 has a blue filter plate 26B.
, green filter plate 26G, red filter plate 2
6R2 and end plates supporting their filter plates, shafts,
Consists of drive solenoid, filter position sensor, etc., and filters vi26B, 26G, 26R (
7) l-) is selectively positioned in the exposure optical path.

Around the photoreceptor drum 27, a static elimination corona generator (static elimination charger) 30. Charged corona generator (charger) 32. Erase lamp 34. Yellow developer 36Y,
Magenta developer 36M, cyan developer 36C1, transfer drum 38. cleaning.

Unit 39 etc. are arranged.

The photosensitive surface 28 of the photosensitive drum 27 is connected to a static elimination charger 30.
After the charger 32 uniformly applies an IF charge, the erase lamp 34 removes the charge in the area outside the width of the recording paper, and when the exposure process is completed, the original passes through the filter plate (26B). Exposure is started by the reflected light. The photosensitive drum 27 rotates in synchronization with the scanner 15 (counterclockwise in the figure), and when the photosensitive surface 28 is irradiated with reflected light from the original, the surface potential changes depending on the intensity of the light, so that electrostatic A latent image is formed. This electrostatic latent image is produced by the yellow developer 36Y, the magenta developer 36M,
The image is visualized (hereinafter referred to as a toner image) using each toner in any one of the cyan developing devices 36C. In FIG. 1, since the filter plate 26B is inserted in the exposure optical path, the yellow developer 36Y is selected and yellow toner is deposited and visualized.

This toner image is transferred onto the recording paper 5 wound around the transfer drum 38 directly below the transfer corona generator (transfer charger) 40 . Details of the transfer drum 38 are shown in FIG. 2a. The transfer drum 38 is a cylindrical wall made of mylar (light-transmitting/flexible dielectric film) 3 wrapped around an offset cylinder made of aluminum molded with a 1° end portion and a connecting portion 2, and has an electric charge on the surface. Use i-electronic power to adsorb the recording paper 4.

The connecting portion 2 is equipped with a clamper 5 that presses one end of the recording paper 4, and the clamper 5 is equipped with a cam 5 via a cam shaft 5b.
a is engaged and can be driven to open and close in a fan shape around the camshaft 5b.

The operation of winding the recording paper 4 around the transfer drum 38 will be explained.

At a predetermined timing, the recording paper 4 is fed out from the paper feed cassette 44 by the paper feed roller 42, and is sent out to the registration roller 46 at a constant speed.

Paper sensor for 46 registration rollers (not shown)
When detecting the arrival of the recording paper 4, the registration roller 46 is driven by the pulse motor 48.

The recording paper 4 is accelerated to twice the speed, collides with the open clamper 5, and is clamped. The clamper 5 is opened and closed mechanically by a push-up pin (not shown) provided around the transfer drum 38 and a cam 5a, but the acceleration by the registration roller 46 makes this clamp highly reliable. There is.

At this time, if two or more sheets of recording paper are fed overlappingly (double feeding), it may cause scratches or mechanical distortion on the Mylar 3 or photosensitive surface 28, or cause paper jams due to tearing of the recording paper. Become. For this reason, a sensor (not shown) for detecting double feeding is arranged on the conveyance path of the recording paper leading to the transfer drum 38, and when double feeding is detected, paper feeding is stopped.

This copying device is equipped with a mode for monochrome copying, which includes yellow and magenta.

This can be done by specifying cyan. For example, when monochrome copying using cyan is specified, the filter plate 26R of red, which is a complementary color, is set in the exposure optical path, and development is performed using cyan toner that energizes the cyan developer 36G. That is, the photosensitive surface 28 is exposed to light reflected from the original that has passed through the red filter plate 26°R, and an electrostatic latent image is formed.
The image is developed with toner and transferred onto recording paper 4 wound around a transfer drum. The recording paper 4 on which the cyan toner image has been transferred is separated from the transfer drum by a static eliminating corona generator 66 that also serves as a separation charger and a separation claw (not shown), and is sent to the fixing device 50 by a conveyance roller (not shown). . In the fixing device 50, a fixing roller 6 with a built-in heater
2, the cyan toner image on the recording paper 4 is fixed and ejected to the copy tray 52 via a paper ejection roller (not shown). After the toner (cyan) image has been transferred, the photosensitive drum rotates one more rotation, is cleaned by a cleaner 39, and then returns to its home position so that the next copying process can be performed.

When a mode for color copying is designated, the photosensitive drum 27 rotates until the photosensitive surface 38 is connected to the charger 30.
to eliminate static electricity, charge it uniformly with charger 32, and erase/
The lamp 34 performs exposure charge removal on the outer portion. First, in the first exposure-curse image transfer process, the filter plate drive solenoid selects the blue filter plate 26B, and the light reflected from the original through this filter plate causes an electrostatic latent image of yellow, the complementary color of blue, to be formed on the photosensitive surface. is formed. This electrostatic latent image is 3
At 6Y, the image is visualized with yellow toner and transferred onto the recording paper 4.

After the yellow toner image is transferred, the photosensitive surface 28 is cleaned, neutralized, charged, and erased in the cleaner 39. Then, in the second exposure-development-transfer process, the filter plate drive solenoid selects the green filter plate 26G. Then, an electrostatic latent image of magenta, the complementary color of green, formed on the photosensitive surface by the reflected light of the original that passes through this is visualized with magenta toner at 36M, and is transferred onto the recording paper 4 on which the yellow toner image has been transferred. be done.

After cleaning the photosensitive surface 28, eliminating static electricity, *charging, and erasing,
Furthermore, in the third exposure-development-transfer process, the red filter plate 26R is selected.

An electrostatic latent image of cyan, the complementary color of red, is formed on the photosensitive surface by the light reflected from the original document. The toner image visualized by the cyan toner in the cyan developing device 36G is transferred onto the recording paper 4 on which the yellow and magenta toner images have been transferred, and a full color image is created by additively mixing these yellow, magenta and cyan toner images. Therefore, separate charger 6
6 and a separation claw, it is peeled off from the transfer drum, fixed in the fixing device 50, and then transferred to the copying machine via the paper ejection roller.
The paper is discharged onto the tray 52. Finally, in order to eliminate static electricity, the photosensitive drum rotates one more rotation, and after being cleaned by a cleaner 39, it returns to the home position in preparation for the next copying process.

In addition, in FIG. 1, 54 is a main motor.

56 is a developing motor, 60 is a fixing motor, 66 is a precharge roller generator, and 68 is a fan motor.

By the way, it should be noted that in FIG. 2a, a part of the inner side C (direction toward the pair of frame parts) of the end 1 of the offset cylinder around which the Mylar 3 is wound is tapered with a width a.

In this case, the width of the flexible portion of mylar wrapped around the offset cylinder is the width at the beginning of the taper in a circular manner that continues at the 2' ends. That is, compared to a conventional transfer drum in which the width of the flexible portion is between the cutout portions of the cylinder, the width can be increased by 2a.

Ql is the width of the recording paper, rQ2 is the width of the photosensitive surface, and the width of the Mylar flexible part is Q3, so the above-mentioned ideal conditions,
It becomes possible to obtain ms<Ql<23.

FIG. 2b shows a sectional view taken along the line ICIC in FIG. 2a.

As can be seen from FIG. 2b, the contact pressure between the recording paper 4 and the photosensitive surface 28 can be obtained by the elasticity of Mylar, and the width of the photosensitive surface 28 can be ensured sufficiently within the width of the flexible portion of the Mylar 3. Since the strength of the offset cylinder can be obtained by the entire width of the end portion 1 including the tapered portion, it can withstand practical use. This results in a small-sized transfer drum with sufficient strength to obtain the desired results.

Furthermore, in a preferred embodiment of the present invention, the taper is a rotating curved surface that rotates around the axis of the cylinder, so that the end portion changes smoothly from the cylindrical circumferential surface. As a result, the above-mentioned bending force of the Mylar is dispersed, so that the application of unreasonable force is reduced, and the life of the Mylar can be extended.

■Effects of the Invention As described above, according to the present invention, the transfer drum is made of a flexible dielectric film, and the ends of the offset shear ring, which is a support supporting the transfer drum in a cylindrical shape, are continuously tapered. Since a gap is provided between the transfer drum and the dielectric film, the elasticity of the dielectric film can be fully utilized, and a compact transfer drum that does not apply unnecessary pressure to the photoreceptor can be obtained.

[Brief explanation of drawings]

FIG. 1 is a front view showing a schematic configuration of a color copying machine embodying one embodiment of the present invention. FIG. 2a is a perspective view showing the photosensitive drum and transfer drum of FIG. 1, and FIG. 2b is a sectional view taken along line I C-I C in FIG. 2a. FIG. 3 is a sectional view showing an example of the prior art. FIG. 4 is a cross-sectional view showing the drawbacks of the prior art. 1: End portion 2: Connecting portion 3: Mylar (flexible dielectric material) 4: Recording paper 5: Clamper 10: Holding plate
12: Contact glass 14: Exposure lamp
15: Scanner 20: Lens 16. tg, 22, 24: mirror 26:
Filter unit 27: Photosensitive drum 28: Photosensitive surface 30: Static elimination outer charger 32: Charger 34: Erase lamps 36Y, 36M, 36C: Developing device 38: Transfer drum 40: Transfer charger 42; Paper feed roller 44: M Paper cassette 46: Registration roller

Claims (1)

[Scope of Claims] In a transfer drum in which a cylindrical flexible dielectric material is attached to the annular ends of a support body in which annular ends are connected to both ends of a rod-shaped connecting part; The part has a ring-shaped circumferential surface that supports a flexible dielectric, and a linear or curved tapered circumferential surface that is continuous with the ring-shaped circumferential surface and separates from the flexible dielectric. Characteristic copying machine transfer drum.