JPH07257778A - Image forming device - Google Patents

Abstract

PURPOSE:To provide a high quality color image having no color slip and unevenness of transfer by steadily attracting a recording material onto its carrying body and transferring it without the occurrence of a slippage in a carrying direction between the tip and rear end of the recording material. CONSTITUTION:A means for selectively carrying out the rotation and stoppage of a roller and the separation and contact of a nip is provided in the pair of second register rollers 46 provided in the most downstream part of a recording material carrying route, and a means for selectively carrying out the rotation and stoppage of the roller is provided in the pair of first register rollers 45 provided on a side more upstream than the above register rollers 46. The recording material P can be prevented from traveling obliquely by forming a loop on the recording material P between the pair of first register rollers 45 and the pair of carrying rollers 44 on a side more upstream than the above rollers 45, and fed into the pair of second register rollers 46, and just after starting of the attraction of the tip domain of the recording material P carried by the pair of register rollers 46 onto a transfer drum carrying sheet 5f, even if the nips of the pair of register rollers 46 are separated, the recording material can be fed and attracted to an attraction position without the occurrence of a slippage in a carrying direction between the tip and rear end of the recording material P.

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 such as an electrophotographic copying apparatus or an electrostatic recording apparatus, and more particularly to a visible image such as a toner image formed on an image carrier on a recording material carrying member. The present invention relates to an image forming apparatus that obtains an image by transferring it onto a carried recording material.

[0002]

2. Description of the Related Art FIG. 11 shows an example of a conventional image forming apparatus for forming a full color image. In this example,
In the image forming apparatus, a photosensitive drum 1, which is an image carrier, is rotatably supported in the direction of the arrow, and around the photosensitive drum 1,
A corona charger 2, an optical system 3, a developing device 4, a transfer device 5 and a cleaning device 6 are arranged.

The optical system 3 is provided with a document scanning section and a color separation filter, and irradiates the photosensitive drum 1 with a color-separated optical image or an optical image E corresponding to the color-separated optical image. Has become. An electrostatic latent image of each color is sequentially formed on the photosensitive drum 1 by irradiating the photosensitive drum 1 uniformly primary-charged by the charger 2 with the optical image E by the optical system 3 for each separated color. .

The developing device 4 is a rotary developing machine, and the central shaft 4
Four developing devices, namely, a cyan developing device 4C, a yellow developing device 4Y, a magenta developing device 4M, and a black developing device 4K are provided around b, and a predetermined developing device is provided at a developing position facing the photosensitive drum 1. To move the photosensitive drum 1
The upper latent image is developed, so that a toner image is formed on the photosensitive drum 1 by the toner whose base is resin.

A recording material is supplied from a recording material cassette 7 to a transfer device 5 by a conveying system according to a paper path (conveyance path) shown by a dotted line in the figure, and the toner image formed on the photosensitive drum 1 is transferred. The image is transferred onto the recording material supplied to the apparatus 5 at a transfer position facing the photosensitive drum 1.

The transfer device 5 is, in this example, a transfer drum 5a.
The transfer drum 5a is composed of a cylindrical body in which a recording material carrying sheet (transfer sheet) 5f made of a dielectric material is stretched in a space on the outer peripheral surface. Around the transfer drum 5a, a transfer charger 5b, a suction charger 5c, and a suction roller 5 are provided.
g, inner and outer charge eliminating chargers 5d and 5e, and separate charge eliminating charger 5h.

The recording material supplied from the recording material cassette 7 to the transfer device 5 via the conveying system is composed of an adsorption charging device 5c composed of a corona charging device inside and outside the transfer drum 5a and an adsorption roller 5g serving as an opposite electrode thereof. It is electrostatically adsorbed and carried on the carrying sheet 5f, and is conveyed toward the transfer position by the rotation of the transfer drum 5a.

At the transfer position, the transfer drum 5a
The toner image on the photosensitive drum 1 is transferred by applying an electric field to the recording material by the transfer charger 5b, which is a corona charger inside. The recording material on which the toner image is transferred is
When the transfer drum 5a is rotated, it is conveyed to the transfer position again,
The toner image of the next color formed on the photosensitive drum 1 is transferred.

When the four color toner images are transferred in this manner, the recording material is decharged by the separation charge-eliminating charger 5h outside the transfer drum 5a, separated from the carrying sheet 5f by the separating means 8 and fixed on the heat roller. After being sent to the container 9, the toner images are mixed in color and fixed on the recording material to form a full-color permanent image, and then the paper is ejected to 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.

[0010]

In the image forming apparatus as described above, usually, the roller can be selectively rotated and stopped immediately before the suction position where the suction charger 5c and the suction roller 5g face each other. A registration roller pair 43, which is one type of transport rollers, is provided. The registration roller pair 43 is configured such that the recording material conveyed from the recording material cassette 7 along the conveyance path is in a stopped state.
After the tip reaches the nip entrance of the recording medium, the recording material is rotated at a predetermined timing to feed the recording material to the suction position.

Before the registration roller pair 43 starts to rotate, the conveyance roller pair 42 on the upstream side of the conveyance path is stopped immediately after the leading end of the recording material reaches the nip entrance of the registration roller pair 43. The recording material is continuously fed toward the registration roller pair 43, and a loop is formed on the recording material between the registration roller pair 43 and the conveyance roller pair 42. As a result, even if the recording material is skewed before reaching the registration roller pair 43, the entire front end portion of the recording material hits the nip entrance of the registration roller pair 43, and the rotation of the registration roller pair 43 starts. At the same time, the leading edge of the recording material is sent out from the registration roller pair 43 so as to coincide with the generatrix direction of the registration roller pair 43.

However, conventionally, the conveying speed of the recording material sent out from the registration roller pair 43 may be significantly different from the peripheral speed of the transfer drum 5a, or the bus bar between the registration roller pair 43 and the transfer drum 5a may be deviated. is there. Therefore, there is a problem in that the conveyance force of the recording material sent from the registration roller pair 43 causes uneven rotation of the transfer drum 5a or distortion of the recording material carrying sheet 5f, resulting in color misregistration or uneven transfer. It was

When the curl of the recording material is controlled in the conveying path on the upstream side of the conveying roller pair 42, the loop formation of the recording material formed between the conveying roller pair 42 and the registration roller pair 43 is performed in the curling direction. When done in the opposite direction,
There is a problem that the curl is reduced and the curl control effect is reduced, and when the curl is removed, the curl is attached due to loop formation.

In order to solve this problem, a method has been proposed in which, after the leading edge of the recording material is sent out, the nip portion of the registration roller pair 43 is separated to reduce the conveying force of the recording material or to open the loop. ing.

However, particularly in the case where the trailing edge of the recording material is located upstream of the conveying roller pair 42, immediately after the leading edge area of the recording material starts to be attracted to the recording material carrying sheet 5f, the registration rollers. When the nip portion of the pair 43 is separated, the leading end portion of the recording material, which is adsorbed by the carrying sheet 5f and is sent out by the registration roller pair 43, and the skew is removed, and the recording material sent by the conveying roller pair 42. When there is a deviation in the conveying direction from the end side, that is, when only the leading edge of the recording material is skewed and the trailing edge is skewed, there is a drawback that causes suction failure or transfer deviation. there were.

The object of the present invention is to convey the recording material in the conveying direction of the leading edge and the trailing edge even if the nip portion of the registration roller pair is separated immediately after the leading edge region of the recording material is adsorbed on the recording material carrier. An image forming apparatus capable of stably adsorbing and transferring a recording material onto a recording material carrier without causing misregistration and capable of obtaining a high-quality image without color misregistration or transfer unevenness. It is to be.

[0017]

The above object can be achieved by the image forming apparatus of the present invention. In summary, the present invention conveys a recording material to a cylindrical recording material carrier by a group of conveyor rollers to carry the recording material, and transfers the carried recording material to the image carrier by rotation of the recording material carrier. In the image forming apparatus that conveys the visible image formed on the image carrier to the recording material, the conveying roller pair located at the most downstream side of the group of conveying roller pairs in the recording material conveying direction. Has means for selectively rotating / stopping rollers and separating / contacting the nip, and at least another pair of conveying rollers has means for selectively rotating / stopping rollers. Image forming apparatus.

According to the present invention, the conveying roller pair having the means for selectively rotating and stopping the rollers can be a curling conveying roller further having means for controlling the curling of the recording material. Preferably, when the leading edge of the recording material after passing through the curl-conveying roller is abutted on the downstream side to remove the skew of the recording material and the timing is adjusted, the loop shape of the abutted recording material is curled. When the loop amount due to the curl of the recording material hitting on the downstream side of the curl-carrying roller pair is 3 mm or less,
The conveyance of the recording material by the conveyance roller pair is started.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic configuration diagram showing an image forming apparatus for forming a color image according to an embodiment of the present invention. The image forming apparatus has a digital color image reader unit in the upper portion and a digital color image printer unit in the lower portion.

In the reader unit, the original 30 is placed on the original table glass 31 and exposed and scanned by the exposure lamp 32, so that the reflected light image from the original 30 is condensed by the lens 33 on the full-color sensor 34, and color separation is performed. Get the image signal. The color-separated image signal is processed by a video processing unit (both not shown) via an amplifier circuit and sent to a printer section.

In the printer section, the photosensitive drum 1 is rotatably supported in the arrow direction. Around the photosensitive drum 1, a pre-exposure lamp 11, a corona charger 2, a laser exposure optical system 3, a potential sensor 12, and four developing devices 4 of different colors.
Y, 4C, 4M, and 4K, the on-drum light amount detection means 13, the transfer device 5, and the cleaning device 6 are arranged.

In the laser optical system 3, the image signal from the reader section is converted into an optical signal by a laser output section (not shown), and the converted laser light E is reflected by the polygon mirror 3a, and the lens 3b and the mirror. It is projected onto the surface of the photosensitive drum 1 through 3c.

When forming an image on the printer unit, the photosensitive drum 1 is rotated in the direction of the arrow, and the photosensitive drum 1 is uniformly charged by the charger 2 after the charge is removed by the pre-exposure lamp 11, and the optical image E is obtained for each separated color. To form a latent image on the photosensitive drum 1.

Next, a predetermined developing device is operated to develop the latent image on the photosensitive drum 1 to form a toner image on the photosensitive drum 1. The developing devices 4Y, 4C, 4M, and 4K are operated by the eccentric cams 24Y, 24C, 24M, and 24K, respectively.
The photosensitive drum 1 is alternatively approached according to each separated color.

The transfer device 5 is provided with a transfer drum 5a on which a recording material carrying sheet (transfer sheet) 5f made of a dielectric sheet such as a polycarbonate film is stretched. A transfer charger 5b and a suction device are provided around the transfer drum 5a. It has a charger 5c, a suction roller 5g, inner and outer chargers 5d and 5e, and a separation charger 5h.

The toner image formed on the photosensitive drum 1 is
When the toner image of four colors is transferred onto the recording material supplied from the recording material cassette 7 to the transfer device 5 via the conveying system at the transfer portion facing the photosensitive drum 1, the separating claw is separated. 8a, push-up roller 8b, and separation charger 5h separate the carrier sheet 5f to send it to the heat roller fixing device 9, where it is fixed to form a full-color permanent image, and then discharged to the tray 10, and the other. 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 to once feed the recording material to the reversing path 21a via the conveyance vertical path 20 and then to reversing the reversing roller 21b. With the rear end as the leading end, it is retracted in the direction opposite to the feeding direction, and is stored in the intermediate tray 22.
After that, the recording material is supplied to the transfer device 5 to attract the image to the transfer drum 5a side, and the image is formed on the other surface of the recording material by the above-described image forming process.

Now, the recording material conveying system of the image forming apparatus will be described in more detail. The recording material sent from the recording material cassette 7 is sent to the suction position where the suction charger 5c and the suction roller 5g face each other through a transport path constituted by a group of transport rollers arranged in series.
By the action of the attraction charger 5c and the attraction roller 5g, it is electrostatically attracted onto the recording material carrying sheet 5f of the transfer drum 5a.

At the most downstream side of this conveying path, immediately before the suction position, there is provided a means capable of selectively rotating / stopping the roller and performing contact / separation of the roller (separation / contact of the nip) at a desired timing. A registration roller pair 46 is provided, and a first registration roller pair 45 capable of selectively rotating and stopping the rollers is provided upstream of the registration roller pair 46. Further, a conveyance roller pair 44 is provided upstream of the first registration roller pair 45. The interval between adjacent roller pairs of the pair of transport rollers including the registration rollers 46 and the like in the transport path is set shorter than the minimum length of the recording material that can be used.

Next, the operation of the conveying roller pair 44, the first registration roller pair 45 and the second registration roller pair 46 will be described.

The conveying roller pair 44 is always rotating or starts to rotate before the recording material arrives. As shown in FIG. 2, the recording which reaches the nip portion of the conveying roller pair 44 is performed. The material P is sent as it is toward the first registration roller pair 45. The recording material P is further fed by the conveying roller 44 while the leading end of the recording material P hits the nip entrance of the stopped first registration roller pair 45, and as a result, as shown in FIG. A loop of the recording material P is formed between 44 and the first registration roller pair 45.

After that, the first registration roller pair 45 starts to rotate at a predetermined timing as shown in FIG.
The recording material P is sent toward the second registration roller pair 46. At this time, even when the recording material P sent from the conveying roller pair 44 is skewed,
By forming a loop between the registration roller pair 45, the entire front end portion of the recording material P is covered with the first registration roller pair 45.
Can be abutted against the entrance of the nip portion, and therefore the leading end portion of the recording material P can be sent out while being aligned with the generatrix direction of the first registration roller pair 45.

The recording material P sent toward the second registration roller pair 46 is the second registration roller pair 46 which is stopped.
5, the second pair of registration rollers 46 starts rotating at a predetermined timing, and the recording material P is sent to the suction position on the transfer drum 5a, as shown in FIG. The leading end of the recording material P is the transfer drum 5.
After the electrostatic attraction to the recording material carrying sheet 5f of a is started, as shown in FIG. 6, the second registration roller pair 46 is separated at a predetermined timing, whereby the recording material P is transferred to the second registration roller pair 46. Is released from the carrying force of the carrier sheet 5f
It is carried and conveyed by the transfer drum 5a while being electrostatically attracted to the top.

As described above, in the present embodiment, the second registration roller pair 46, which is the conveyance roller pair provided on the most downstream side of the conveyance path of the recording material P, selectively rotates / stops the rollers and separates the nip. A first registration roller pair 45, which is a conveyance roller pair provided upstream of the contacting means.
Since a means for selectively rotating and stopping the rollers is provided in the recording medium P, a loop is formed on the recording material P between the first registration roller pair 45 and the conveyance roller pair 44 provided on the upstream side. By doing so, the recording material P can be fed to the second registration roller pair 46 while being prevented from skewing. Therefore, immediately after the front end region of the recording material P conveyed by the second registration roller pair 46 is started to be adsorbed on the recording material carrying sheet 5f of the transfer drum 5a, the nip of the second registration roller pair 46 is separated. Also, the recording material P can be sent to the suction position at a predetermined timing without causing a deviation in the transport direction between the leading end portion and the trailing end portion of the recording material P. Therefore, it is possible to prevent the rotation unevenness of the transfer drum 5a and the distortion of the carrying sheet 5f due to the influence of the conveying force of the recording material P, and it is possible to obtain a high-quality color image without color misregistration or transfer unevenness.

Another embodiment of the present invention will be described.

In this embodiment, in the image forming apparatus of the previous embodiment shown in FIGS. 1 to 6, the registration roller pair 5 is arranged in order from the most downstream side of the recording material conveying path as shown in FIG.
No. 0, a pair of constantly rotating transport rollers 49 and a curl transport roller 48 are provided.

Like the second registration roller pair 46 of FIG. 1, the registration roller pair 50 has means capable of selectively rotating / stopping the rollers and enabling contact / separation of the nip. The curling / conveying roller 48 includes two curling rollers 48a, 4a and 4c made of an elastic member such as a metal roller 48c and sponge.
And 8b for curling rollers 48a and 4
8b is pressed against the metal roller 48c and is driven to rotate. The metal roller 48c has a means capable of selectively rotating and stopping, and the curl-carrying and conveying roller 48 has a form in which a register and a control function similar to those of the registration roller pair 50 are added.

First, as shown in FIG. 7, the recording material P fed from the recording material cassette 7 in FIG. 1 is abutted at the tips of the nip entrance portions of the metal roller 48c and the curling roller 48a in the stopped state. , Forming a loop on the upstream side. By this operation, the leading end portion of the recording material P and the generatrix direction of the metal roller 48c and the curling roller 48a are aligned. After that, the metal roller 48c starts to rotate, and the recording material P is sent to the conveying roller pair 49 through the nip portion between the metal roller 48c and the curling rollers 48a and 48b. The recording material P is curled upward so as to easily follow the circumferential surface of the carrying sheet 5f when passing through the curling and conveying roller.

The curled recording material P is shown in FIG.
As shown in FIG. 5, the sheet is conveyed to the registration roller pair 50 after passing through the constantly rotating conveyance roller pair 49. As shown in FIG. 9, the recording material P conveyed to the registration roller pair 50 hits the nip entrance portion of the registration roller pair 50 which is stopped, and in the case of the present embodiment, the recording material P is conveyed in the arrow direction, that is, curled and conveyed. A loop is formed and grows in the direction opposite to the curl direction given by the roller 48. Immediately thereafter, the registration roller pair 50 starts to rotate at a timing when the loop amount where the loop of the recording material P does not substantially grow is about 3 mm or less, and sends the recording material to the suction position. And the recording material P
After the tip of the sheet has passed the suction position, as shown in FIG.
The nip portion of the registration roller pair 50 is separated at a predetermined timing.

As described above, in the present embodiment, since the curling and carrying roller 48 can be selectively rotated and stopped,
Forming a loop on the upstream side of the curling and conveying roller 48,
When a loop is formed in the direction opposite to the curling direction as in this embodiment, the loop is not formed on the downstream side of the curling direction to prevent skewing of the recording material P and to improve the curling effect. The recording material P can be conveyed to the recording material carrying sheet 5f without damage.

In the above, if a space is formed on the downstream side of the curl-conveying roller 48 and on the upstream side of the conveying roller pair 49 so that a loop in the same direction as the curling direction of the recording material P is formed, It is also possible to achieve a further skewing prevention effect without impairing the curling effect by providing the conveying roller pair 49 with means capable of selectively rotating and stopping.

[0042]

As described above, according to the present invention, the rotation / stop of the rollers and the contact / separation of the nip are selectively performed with respect to the registration roller pair which is the transportation roller pair provided at the most downstream side of the recording material transportation path. Since a means for selectively rotating and stopping the rollers is provided for at least a pair of conveying rollers on the upstream side of the means, during the adsorption of the leading end of the recording material onto the recording material carrier. Further, even if the nip portion of the registration roller pair is separated, it is possible to prevent the front end portion and the rear end portion of the recording material from being displaced in the conveying direction, and the recording material is stably adsorbed on the recording material carrier. Can be transferred. Therefore, it is possible to obtain a high-quality color image without color deviation or transfer unevenness.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is an explanatory view showing a part of recording material conveyance in the apparatus of FIG.

FIG. 3 is an explanatory diagram showing another part of the recording material conveyance.

FIG. 4 is an explanatory diagram showing still another part of the recording material conveyance.

FIG. 5 is an explanatory diagram showing still another part of the recording material conveyance.

FIG. 6 is an explanatory diagram showing still another part of the recording material conveyance.

FIG. 7 is an explanatory diagram showing a part of recording material conveyance in another embodiment of the present invention.

FIG. 8 is an explanatory diagram showing another part of the recording material conveyance.

FIG. 9 is an explanatory diagram showing still another part of recording material conveyance.

FIG. 10 is an explanatory diagram showing still another part of the recording material conveyance.

FIG. 11 is a schematic configuration diagram showing a conventional image forming apparatus.

[Explanation of symbols]

 1 Photosensitive Drum 5a Transfer Drum 5f Recording Material Bearing Sheet 5g Adsorption Roller 44 Conveyor Roller Pair 45 First Registration Roller Pair 46 Second Registration Roller Pair 48 Curling Conveyance Rollers 48a, 48b Curling Roller 48c Metal Roller 50 Registration Roller

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location G03G 21/14

Claims (4)

[Claims] 1. A recording material is conveyed to and carried by a cylindrical recording material carrier by a group of conveyor rollers, and the carried recording material is transferred to a transfer position facing the image carrier by rotation of the recording material carrier. In an image forming apparatus that conveys and transfers a visible image formed on an image carrier onto a recording material, a conveying roller pair located at the most downstream side in the recording material conveying direction of the group of conveying roller pairs, An image characterized in that it has means for selectively rotating / stopping rollers and for separating / contacting a nip, and at least another pair of conveying rollers has means for selectively rotating / stopping rollers. Forming equipment. 2. A curl-carrying conveyance roller having a means for controlling curling of a recording material, wherein the conveyance roller pair having means for selectively rotating and stopping the rollers is a conveyance roller for curling.
Image forming device. 3. A loop shape of the abutting recording material is removed when the leading edge of the recording material after passing through the curl-conveying roller is abutted on the downstream side to remove the skew of the recording material and the timing is adjusted. The image forming apparatus according to claim 2, wherein the curl direction is applied by the curl conveying roller. 4. The image forming apparatus according to claim 3, wherein the conveyance of the recording material by the pair of conveyance rollers is started when the loop amount due to the curl of the recording material that abuts on the downstream side of the pair of conveyance rollers with curl is 3 mm or less. .