JPH0980930A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a transfer drum from being damaged to prevent faulty transfer by making the position of the leading edge of recording material attracted on the transfer drum and a deformation starting position of the transfer drum by a separation pushing-up roller different by every size of standard recording materials. SOLUTION: An HP(home position) sensor 303 provided on the transfer drum detects the specified spot of the transfer drum, and a signal from the sensor 303 is transmitted to a CPU 400 through an I/O 304. The CPU 400 is equipped with an attracting position specifying table 402 so as to store information what position on the transfer drum the paper is attracted to by every size of each paper. When paper size is designated by a paper size designating switch 401, the attracting position of the recording material attracted to the transfer drum is made different by the CPU 400 according to the information on the paper size and the information from the table 402 by every size of the standard recording materials, and also the deformation starting position of the transfer drum by the separation pushing-up roller 8b is made different by the CPU 400 in the same manner.

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 forming an image on a recording material carried on a recording material carrier and then separating the recording material from the recording material carrier, and particularly to an image carrier. The toner images of a plurality of colors are superposed on the same recording material and transferred, and can be suitably embodied in a color image forming apparatus of a type that obtains a color image.

[0002]

2. Description of the Related Art In a conventional image forming apparatus, a suction position of a recording material such as a paper sucked on a transfer drum is always constant regardless of the paper size, and as shown in FIG. Adsorption was carried out along the reference position S as shown in FIG.

To further explain, two sheets of A4 size or B5 size paper P at the same time are the transfer drum 5 which is a recording material carrier.
In the case of carrying and transferring by suction onto 0, the end of the first paper in the longitudinal direction is sucked along the reference position S. Also, A
When only one sheet of paper P of each size of 4R, B5R, B4, A3 is suction-carried and transferred on the transfer drum 50, the end in the width direction is adsorbed along the reference position S.

After the transfer onto the paper adsorbed and carried on the transfer drum is completed, the paper is separated from the transfer drum. At this time, the recording material carrying sheet of the transfer drum is brought into contact with and deformed by the push-up roller which is the recording material carrying body deforming means.
The deformation start point is approximately the position of the leading edge of the paper.

[0005]

However, in the above-mentioned conventional example, the recording material carrying sheet is deformed by the push-up roller from the leading edge to the trailing edge of the paper, but the leading edge of the paper is in a non-contact state. Since it is pushed up and deformed by a certain amount of pressure, it is particularly stressed. Then, with the use of the apparatus, the recording material-carrying sheet may be deteriorated at a specific portion and may be damaged or permanently deformed in a short period of time.

As a result, a transfer failure occurs at a portion where damage or permanent deformation occurs, and the quality of the obtained copy image is remarkably deteriorated.

Therefore, a main object of the present invention is to provide an image forming apparatus capable of preventing damage and permanent deformation of a recording material carrier.

Another object of the present invention is to provide an image forming apparatus capable of preventing the occurrence of transfer failure due to the recording material carrier and obtaining a high quality image.

[0009]

The above object can be achieved by an image forming apparatus according to the present invention. In summary, the present invention provides:
A recording material carrier that carries and rotates a recording material to a transfer position facing the image carrier, and an adsorption charging unit that electrostatically adsorbs and carries the recording material on the recording material carrier. Transfer charging means for transferring the toner image formed on the image carrier onto the recording material conveyed to the transfer position, and the recording material electrostatically adsorbed on the recording material carrier In an image forming apparatus provided with a recording material carrier deforming means that operates when further separated, the adsorption position of the recording material tip end adsorbed on the recording material carrier is different for each standard recording material size, and In the image forming apparatus, the deformation starting position of the recording material carrier by the recording material carrier deforming means is different for each standard recording material size.

In the standard recording material size, it is preferable that all the deformation starting positions of the recording material carrier by the recording material carrier deforming means are different. It is preferable to include a paper size designation switch and a suction position designation table.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An image forming apparatus according to the present invention will be described below in more detail with reference to the drawings.

Embodiment 1 FIG. 1 is an overall configuration diagram showing an embodiment of an image forming apparatus of the present invention. This image forming apparatus represents a full-color copying machine, and has a digital color image reader section in the upper part and a digital color printer section in the lower part.

In the reader unit, the reflected light image from the original 30 obtained by placing the original 30 on the original table glass 31 and exposing and scanning with the exposure lamp 32 is condensed by the lens 33 on the full-color sensor 34, and the Obtain a color separated image signal. This color-separated image signal is amplified by an amplifier circuit (not shown), processed by a video processing unit (not shown), and sent to a printer unit.

In the printer section, the photosensitive drum 1, which is an image carrier, is rotatably carried in the direction of the arrow in the figure. Around the photosensitive drum 1, a pre-exposure lamp 11 for initializing the surface of the photosensitive drum 1, a charger 2 (corona charger in this example) for uniformly charging the surface of the photosensitive drum 1, A laser exposure optical system 3 that forms an electrostatic latent image according to image information on the body drum 1, a potential sensor 12 that detects a potential on the surface of the photosensitive drum 1, an electrostatic latent image formed on the photosensitive drum 1. To develop a visible image, four developing devices 4Y, 4M, 4C, which store developers (toners) of different colors,
4K fixedly arranged developing device, light amount detecting means 13 for detecting the amount of toner on the photoconductor drum 1, transfer device 5 including a transfer drum 5a as a recording material carrier, and developer remaining on the photoconductor drum 1. Cleaners 6 and the like for removing are respectively provided.

In this embodiment, the laser exposure optical system 3 is composed of a polygon mirror 3a, a lens 3b, a mirror 3c, etc., and a laser output section modulated by the color image signals for each color separated from the reader section. The laser light E from is reflected by the polygon mirror 3a and projected onto the surface of the photosensitive drum 1 through the lens 3b and the mirror 3c to form an electrostatic latent image corresponding to a color image signal of each color.

At the time of image formation in the printer section, the photosensitive drum 1 is rotated in the direction of the arrow shown in the figure, first, the surface of the photosensitive drum 1 is neutralized and initialized by the pre-exposure lamp 11, and then, the photosensitive drum 1 is charged by the charger 2. 1 surface is uniformly charged, and an optical image E corresponding to the image signal of each color separated by the laser exposure optical system 3 is sequentially irradiated onto the surface of the photosensitive drum 1 to form an electrostatic latent image in a predetermined color order. To form.

Next, the latent image on the photosensitive drum 1 is operated by operating a prescribed developing device in the prescribed order of development of cyan (C), magenta (M), yellow (Y) and black (K). Are developed to sequentially form toner images based on resin on the photosensitive drum 1. Here, each developing device 4 of the developing device
Y, 4M, 4C, 4K are eccentric cams 24Y, 24M, 2
By the operations of 4C and 24K, a required developing device is alternatively brought close to the photoconductor drum 1 in accordance with the color of the formed latent image to perform the developing operation.

The transfer device 5 includes a transfer drum 5a on which a recording material carrying sheet 5f made of a dielectric sheet is stretched, and the toner image on the photosensitive drum 1 is transferred to the recording material around the transfer drum 5a. Transfer charging brush 5b, a suction charging brush 5c which is a suction charging means for suctioning the recording material to the transfer drum 5a, a suction roller 5g, and an inner static eliminator 5
d and the outer static eliminator 5e.

The toner image formed on the photosensitive drum is fed from the recording material cassette 7a, 7b, or 7c (may be manually fed) by a conveying system including a pickup roller, a paper feed guide, a paper feed roller and the like. When a toner image of four colors is transferred onto the recording material such as the transferred transfer paper at the transfer portion facing the photosensitive drum 1, the separation claw 8
a, the separation push-up roller 8b and the separation charger 5h separate the recording material carrying sheet 5f from the recording material carrying sheet 5f, and the sheet is sent to the heat roller fixing device 9 by the conveying means, and is fixed there to form a full-color permanent image. The paper is discharged onto the tray 10. On the other hand, after the residual toner on the surface of the photosensitive drum 1 is cleaned and removed by the cleaning device 6, the photosensitive drum 1 is subjected to the image forming process again.

When images are formed on both sides of the recording material,
Immediately after the recording material is discharged from the fixing device 9, the conveyance path switching guide 19 is driven, and the recording material is once guided to the reversing path 21a via the conveyance vertical path 20. Then, the reversing roller 2
By reverse rotation of 1b, the recording material is retracted in a direction opposite to the direction in which the recording material is fed, with the trailing end of the fed recording material at the head, and stored in the intermediate tray 22. Thereafter, the recording material is again conveyed from the intermediate tray 22 to the transfer device 5, and an image is formed on the other surface by the above-described image forming process.

Next, a transfer device having a transfer drum will be described in detail. In FIG. 2, a recording material carrying sheet 5f that electrostatically attracts a recording material and conveys it in the C direction is wound around the outer peripheral surface of the transfer drum 5a.
The front and rear end portions of are attached to the connecting member 5j of the transfer drum 5a. In the case of this embodiment, the recording material carrying sheet 5f is flexible and has a thickness of 150 μm and a volume resistivity of 10 ¹⁵ Ωc.
A PC (polycarbonate) film of m or more is used.

The recording material is fed from the direction of arrow B by a feeding / conveying means (not shown). Here, the attraction roller 5g is brought into close contact with the recording material carrying sheet 5f by a drive source (not shown), and an attraction current (charge) is injected from the attraction charging brush 5c. Since the attraction roller 5g is electrically grounded, a current (charge) in the opposite direction (reverse pole) to the current (charge) injected by the attraction charging brush 5c is induced (induced), and as a result, the recording material P Is electrostatically adsorbed on the recording material carrying sheet 5f.

Next, a current (charge) is injected into the transfer charging brush 5b from a positive high voltage power source (not shown), and the negatively charged toner image formed on the photosensitive drum 1 is transferred onto the recording material as described above. When performing multiple transfer, this transfer operation is repeated a desired number of times.

When the recording material is rotated toward the separation push-up roller 8b after the transfer of a predetermined number of times is completed, the separation push-up roller 8b is moved.
3b is driven by a driving means (not shown), and the recording material carrying sheet 5f is detached as shown in FIG.
Push it up to the side. Almost in synchronism with this timing, the separating claw 8a is also operated by the driving means (not shown) and descends in the direction of the recording material carrying sheet 5f as shown in FIG. At this time, the separation claw roller 8c attached to the rear surface of the tip of the separation claw 8a contacts the recording material carrying sheet 5f, thereby preventing the tip of the separation claw 8a from damaging the recording material carrying sheet 5f.

On the other hand, the separation charge eliminator 5h discharges during this separation operation to assist the separation and neutralizes the ions generated by the separation discharge from the recording material carrying sheet 5f,
Prevents uneven discharge.

When a series of transfer / separation operations are completed, the carrying sheet cleaner 16 is rotated by a rotation driving motor (not shown), abutted against the recording material carrying sheet 5f by a driving means (not shown), and carried through the recording material carrying sheet 5f. By the action of the backup brush 17 facing the sheet cleaner 16, the residual toner on the recording material carrying sheet 5f is cleaned.

The inner static eliminator 5d and the outer static eliminator 5e operate before and after the series of adsorption, transfer and separation operations described above to electrically initialize the recording material carrying sheet 5f.

Next, specific examples of the auxiliary equipment of the transfer device in this embodiment will be shown below. The diameter of the transfer drum 5a is 180
mm, and the moving speed is 130 mm / sec. Further, the current of the adsorption brush I _Q = 15 μA, the current of the transfer brush I _T = 10 μA, the output of the separation static eliminator AC V = 12 kVpp DC I _S = 300 μA (if necessary), the output of the inner static eliminator AC V = 12 kVpp ... (A) DC I _i = 200 μA Output of outer static eliminator AC V = 12 kVpp (b) DC I ₀ = 200 μA However, both (a) and (b) are sine waves and have opposite phases.

The separating claw 8a is formed of a semiconductive resin having a resistance value of about 10 ⁷ Ω, in which carbon is dispersed in polyester resin.

FIG. 4 shows a block diagram relating to the above-mentioned paper suction position and separation operation control.

In the image forming apparatus shown in this embodiment, the photosensitive drum 1 and the transfer drum 5 are meshed with each other by a gear, and the transfer drum 5 is driven and rotated by the drum motor of the photosensitive drum 1. 1,200 per rotation from the drum motor 301 which is the pulse motor of the photosensitive drum 1.
A pulse signal is sent to the CPU 400 via the I / O 302. The operation of the entire device is based on this pulse (drum clock).

On the other hand, a H. P. A (home position) sensor 303 is provided, and it is possible to detect a predetermined one portion of the transfer drum, and the signal thereof is sent to the CPU 400 via the I / O 304. The drum clock is always initialized by a signal from the home position sensor 303 of the transfer drum, and the counting of 1200 pulses is started each time. This is because the drum clock also has an error, and if the reset is not performed every time, the error accumulates, which causes a problem that accurate image formation cannot be performed.

On the other hand, when the user presses the paper size designation switch 401, A4, A4R (longitudinal feed), A3,
When the paper size of ... Is designated, the information is stored in the CPU 40.
It is sent to 0. Further, the CPU 400 is provided with a suction position designation table 402, and a memory for which position on the transfer drum the paper is to be sucked is stored for each paper size. The contents are shown in Table 1 below. L in Table 1 indicates the distance from the connecting member to the leading edge of the paper.

[0034]

[Table 1]

When the paper size and the paper suction position are determined, the information is sent to the registration roller 308, the separation push-up roller 8b and the separation claw 8a via the I / Os 305, 306 and 307, and according to the timing, The paper is fed from the registration roller to the transfer drum, and the paper is electrostatically adsorbed on the recording material carrying sheet 5f by the adsorption charging brush or the like, and the image forming operation described above is performed. It is determined by the operation timing of the roller.

Further, the operation timing of the separation push-up roller 8b also differs depending on the suction position of the paper, and as shown in FIG. 5, the action start point of the separation push-up roller indicated by ▼ is which paper size 2 The recording material carrying sheet 5f
You can see that they are not in the same position above.

As described above, since the suction position of the leading end of the recording material sucked on the transfer drum is different for each standard recording material size, and the action start position by the separating push-up roller is different for each standard recording material size. , The deformed portion due to the separation push-up roller can be dispersed as compared with the conventional one, the damage and permanent deformation of the transfer drum can be prevented, and the durable life of the transfer drum can be greatly extended, and the transfer drum It is possible to prevent transfer defects due to damage and permanent deformation, and obtain a high-quality image.

Embodiment 2 In Embodiment 1, as shown in the schematic view of FIG. 5, the position of the leading edge of the paper and the operating position of the separation push-up roller are different for each size, but the position of the trailing edge of the paper is different. Are set to be the same.

The present embodiment is characterized in that the front end and the rear end of the paper are set to have different positions for each size. As a result, the trailing edge of the paper comes into contact with the photosensitive drum every time, and the degree of mechanical or electrical damage to the photosensitive drum is weaker than in the previous embodiment, and there is an advantage that the durable life of the photosensitive drum can be extended.

[0040]

As is apparent from the above description, the suction position of the tip of the recording material to be adsorbed on the recording material carrier differs for each standard recording material size, and the recording material is deformed by the recording material carrier deforming means. Since the deformation start position of the carrier differs for each standard recording material size, the deformed portion by the recording material carrier deforming means can be dispersed as compared with the conventional one, causing damage and permanent deformation of the recording material carrier. Can be prevented, the durable life of the recording material carrier can be greatly extended, and the occurrence of transfer defects due to damage and permanent deformation of the recording material carrier can be prevented, and high-quality images can be obtained. .

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of an image forming apparatus in which the present invention is embodied.

FIG. 2 is a schematic configuration diagram showing a transfer drum of the image forming apparatus of FIG.

3 is a schematic configuration diagram showing the vicinity of a separation portion of a transfer drum of the image forming apparatus of FIG.

FIG. 4 is a block diagram for explaining the first embodiment.

FIG. 5 is a schematic diagram showing the suction position of paper and the operation timing of the separation push-up roller for each size that best represents the characteristics of the first embodiment.

FIG. 6 is an explanatory view schematically showing suction positions of paper of each size on a transfer drum in a conventional image forming apparatus.

[Explanation of symbols]

 1a Photosensitive drum (image carrier) 5a Transfer drum (recording material carrier) 5b Transfer conductive brush (transfer charging means) 5c Adsorption charging brush (adsorption charging means) 8a Separation claw 8b Separation push-up roller (recording material carrier deforming means) 400 CPU 401 Paper size specification switch 402 Adsorption position specification table

Claims (3)

[Claims] 1. A recording material carrier for carrying a recording material and rotating the recording material to convey it to a transfer position facing the image carrier.
Adsorption charging means for electrostatically attracting and carrying a recording material on the recording material carrier, and transfer charging means for transferring the toner image formed on the image carrier to the recording material conveyed to the transfer position. And an image forming apparatus including a recording material carrier deforming unit that operates when the recording material electrostatically adsorbed on the recording material carrier is separated from the recording material carrier. The suction position of the leading end of the recording material to be adsorbed on the recording material carrier differs depending on the standard recording material size, and the deformation start position of the recording material carrier by the recording material carrier deforming means varies according to the standard recording material size. Image forming apparatus. 2. The image forming apparatus according to claim 1, wherein, in the standard recording material size, the deformation start positions of the recording material carrier by the recording material carrier deforming means are all different. 3. The image forming apparatus according to claim 1, further comprising a paper size designation switch and a suction position designation table.