JP2003150019A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of image blurring or paper jamming in a copying machine having one-path both-sided function. SOLUTION: An image forming unit 10R and an image forming unit 10L, which are arranged at upstream side and downstream side in the direction for feeding a transfer material P have a pair of timing rollers 25R and 25L, photoreceptor drums 12R and 12L, and fixing units 27R and 27L respectively. The transfer material feeding speed at each member is decreased in the direction for feeding the transfer material P. In particular, the transfer material feeding speed at the upstream-side fixing unit 27R is made different from that at the pair of downstream-side timing rollers 25L. Such a structure prevents the transfer material from being pulled when carried over the members.

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 having a plurality of image forming means.

[0002]

2. Description of the Related Art Conventionally, there has been proposed an image forming apparatus having a plurality of image forming sections, particularly an image forming apparatus having a so-called 1-pass double-sided function having an image forming section on each side for forming an image on both sides of a transfer material. ing.

FIG. 5 is a schematic front sectional view of a conventional image forming apparatus.

In FIG. 5, as a conventional image forming apparatus, first and second image forming units 101 and 102 arranged on the upstream side and the downstream side with respect to the conveyance direction of the transfer material P, and a sheet feeding unit 201. , 202, transfer material cassettes 301, 30
2 and the paper discharge unit 401 are configured inside the apparatus main body 100.

The two image forming units 101 and 102 are arranged in the front and rear with respect to the conveying direction of the transfer material P.

The transfer material fed from one of the transfer material cassettes 301 and 302 by the paper feeding means 201 and 202 is first conveyed to the first image forming section 101 to form an image.

The speed of the transfer material is controlled by the upstream timing roller pair 121, and the first image forming means 16 is controlled.
Sent to 1. Then, the first image forming unit 161
After the image is transferred to the first surface of the transfer material P by the fixing roller 131 as the first fixing unit, the image is fixed for the first time.

After that, the transfer material P is transferred to the second image forming section 1
02 to the second surface of the transfer material P while being controlled in speed by the timing roller pair 122 on the downstream side by the same configuration as the second image forming unit 101. After receiving the transfer of the image, the second fixing roller 132 fixes the image for the second time.

By the above steps, images are formed on both sides of the transfer material P, and the transfer material P is discharged to the paper discharge section 401 by the paper discharge roller 182 as a paper discharge means.

Further, in the above-mentioned members that convey the transfer material at the respective positions such as the paper feeding portion, the conveying portion, and the fixing portion, the speed at which the transfer material is conveyed (transfer material conveying speed) is always constant. It aims to be transported without pulling or sagging. Further, in order to carry out image formation in accordance therewith, the rotational speeds of the first image carrier 151 on the upstream side and the second image carrier 152 on the downstream side are set to be the same.

[0011]

However, when maintaining the transport speed of the transfer material P at a constant speed, the following problems may occur.

The transfer material conveyance speed is roughly determined by the product of the rotation speed of the transfer material transfer roller and the feed roller diameter. However, for example, since the fixing rollers 131 and 132 are composed of thick rubber rollers, their roller diameters change significantly due to variations in molding, temperature, pressure applied to the upper and lower rollers, etc. Causes an error in the transfer material transport speed. The rollers included in the other conveying means also have an error in the outer diameter of the roller, although the error range is small.

Further, the driving means for each roller is usually a motor, which generally has a rotation speed error of about ± 0.5%, and this rotation speed error also leads to an error in the transfer material conveying speed.

Here, as shown in FIG. 6, when the transfer material P passes over the fixing roller 131 on the upstream side and the timing roller pair 122 on the downstream side, the timing roller pair 122 is caused by the above-mentioned error in the transfer material conveying speed. When the transfer material conveyance speed of 1 is higher than the transfer material conveyance speed of the fixing roller 131, the transfer material P may be pulled between the two rollers.

Further, when the transfer material P is conveyed from the image carrier 151 to the fixing roller 131 in the first image forming section 101, the conveying speed of the transfer material P depends on the conveying speed of the transfer material P of the fixing roller 131. In this case, since the transfer speed of the transfer material P at the portion in contact with the image carrier 151 is also slowed, the image may be shrunk by the speed ratio and the image may be distorted.

On the other hand, as shown in FIG. 7, at the moment when the rear end of the transfer material P in the conveying direction passes through the fixing roller 131 on the upstream side,
Since the transfer material conveying speed changes remarkably, image blurring or image unevenness due to the shock may occur.

In such a structure, the transfer force of the downstream timing roller pair 122 is made strong so that the transfer material transfer speed is forcibly dependent on the timing roller pair 122, and the fixing roller 131 is pulled by the transfer material P. There is.

However, the fixing roller 131 has a remarkably larger diameter than the timing roller pair 122 and its pressing force is also large. Therefore, when the fixing roller 131 is pulled by the transfer material P, slippage or the like is caused due to the magnitude of the load. And in the worst case, the transfer material P is damaged,
It may cause a paper jam or damage the device.

Also in such a structure, as in the above example, as shown in FIG. 7, when the trailing end of the transfer material P in the transport direction passes through the fixing roller 131, the transport load is instantly reduced. Therefore, the conveyance speed may change significantly, and this shock may cause image blurring or image unevenness.

An object of the present invention is to provide an excellent image forming apparatus which prevents the transfer material from being pulled by the transfer material conveying means, thereby preventing the transfer material from being damaged, paper jamming, image blurring, and device damage. It is to be.

[0021]

The above-mentioned problems can be solved by the following constitutions.

The first configuration of the image forming apparatus according to the present invention is the first image formation in which the toner image on the first image carrier on which the image is formed is transferred onto the transfer material by the first transfer means. A first image forming portion having at least a means, and a second image forming means having at least a second image forming means for transferring the toner image on the second image carrier on which the image is formed onto the transfer material by the second transfer means. Two image forming portions are arranged in front and rear with respect to the transfer material conveying direction, the toner image is transferred onto the first surface of the transfer material by the first image forming means, and then by the second image forming means. In the image forming apparatus capable of transferring the toner image onto the second surface of the transfer material, the first speed of the transfer material passing through the first image forming means is the transfer material passing through the second image forming means. Is faster than the second speed of the The transfer material is sent to the second image forming section at a third speed lower than the first speed, and the second image forming section transfers the transfer material at a fourth speed lower than the third speed and higher than the second speed. To receive.

A second configuration of the image forming apparatus according to the present invention is the same as the first configuration, wherein the first image forming section is
The first image forming unit has a first fixing unit for fixing the toner image transferred onto the first surface of the transfer material, and the second image forming unit is provided by the second image forming unit. A second fixing unit that fixes the toner image transferred onto the second surface of the transfer material that has passed through the first fixing unit is provided, and the conveyance speed of the transfer material that passes through the first fixing unit is set to the above-mentioned. The transfer speed of the transfer material passing through the second fixing unit is set to be higher.

A third structure of the image forming apparatus according to the present invention is the first or second structure, wherein the transfer material supply speed for supplying the transfer material toward the first image carrier is the first. Faster than speed.

According to a fourth structure of the image forming apparatus of the present invention, in any one of the first to third structures, the transfer material is fed to the image forming means with respect to the predetermined image forming means. And a paper discharging means for discharging the transfer material from the image forming means.

According to the above construction, the transfer material transporting speeds of the respective transporting means for transporting the transfer material provided in the first and second image forming portions may vary, but the speeds are reversed. It is possible to prevent the downstream conveying means from becoming faster, and it is possible to prevent the transfer materials from being pulled together. Further, since the transfer material transport speed of the upstream transport means is higher than that of the downstream transport means, it can be absorbed by forming a loop on the front side of the downstream transport means. It is possible to prevent adverse effects.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to the examples in the embodiments.

(Embodiment 1) Embodiment 1 will be described below with reference to FIGS. 1 to 3. In addition, the same code | symbol is described in the member common to each figure.

FIG. 1 is a schematic front sectional view showing the structure of a double-sided image forming image forming apparatus as the image forming apparatus according to the first embodiment.

In FIG. 1, as the image forming apparatus dedicated to double-sided image formation, the image forming units 10R and 10L as first and second image forming means are arranged on the upstream side and the downstream side with respect to the conveyance direction of the transfer material P. Arrange and connect 5 between them
It is configured to connect at 0.

Since the internal structure of each of the image forming units 10R and 10L is substantially vertically symmetrical, the first image forming unit 10R will be described below and the second image forming unit 10 will be described.
The description of R is omitted.

As the exposure means 11, for example, a light-emitting element (not shown) such as an LED is used as a photosensitive drum 12 as an image carrier.
A large number of light emitting elements are arranged in the longitudinal direction of R, and light emission is controlled according to image data by a light emitting element drive circuit (not shown). A line of light emitted from the exposure unit 11 is the photosensitive drum 12.
An image is formed on R to form an electrostatic latent image.

13 is a pre-exposure lamp, 14 is a primary charger,
Reference numeral 15 is a developing device, 16 is a transfer charger as a transfer means, and 1 is a transfer charger.
Reference numeral 7 is a separation charge-eliminating needle, and 18 is a cleaner, which are arranged around the photoconductor drum 12R and constitute a well-known electrophotographic process.

The transfer material P such as paper fed from the paper feeding cassette 20 is conveyed by the timing roller pair 25R and visualized by the developing device 15 to the photosensitive drum 12R.
The toner image is sent onto the transfer charger 16 at the same timing as the toner image.

The transfer material P on which the toner image is transferred is separated from the photosensitive drum 12R by the action of the separation charge-eliminating needle 17,
It is conveyed by the conveyor belt 26R and sent to the fixing device 27R as a fixing unit.

The transfer material P, on which the toner image is fixed by the fixing device 27R by heat and pressure, passes through the connecting path 50,
The sheet is conveyed as it is to the second image forming unit 10L.
Then, in the second image forming unit 10L, the same steps as those of the first image forming unit 10R described above are repeated, and after the image is formed on the lower surface side of the transfer material P, the transfer material P is ejected from the discharge roller pair. It is discharged to the outside of the apparatus by 28.

However, in the second image forming unit 10L, since the image is formed on the lower surface of the transfer material P, the transfer material P is adsorbed to the upper side of the transfer belt 26L in front of the fixing device 27L so as to be transferred. A suction device 19 is attached to.

According to the above construction, the two image forming units 10R and 10L can be operated at the same time, so that the productivity which is twice as high as the image forming speed peculiar to the image forming unit is ensured and the single-sided image formation is performed. It is possible to form a double-sided image with the same productivity.

FIG. 2 is a time chart showing the transfer material conveying speed of each conveying means in the first embodiment.

As the conveying means, in the first and second image forming units 10R and 10L, the timing roller pairs 25R and 25L and the photosensitive drums 12R and 12L are used.
And fixing devices 27R and 27L.

As shown in FIG. 2, the transport speed of each transport means gradually decreases along the transport direction of the transfer material P, and the transport speed of the transfer material on the upstream side photosensitive drum 12R is 200 mm / s. On the other hand, the transfer material transport speed on the downstream side photosensitive drum 12L is 190 mm / s, which is about 5 mm.
% Late.

More specifically, the transfer material P sent from the paper feed cassette 20 to the first image forming unit 10R.
Is 202 mm / s due to the timing roller pair 25R
The transfer material is fed to the photosensitive drum 12R.
The photosensitive drum 12R is rotating at a peripheral speed of 200 mm / s, and the transfer material P after the portion passing through the photosensitive drum 12R is conveyed at 200 mm / s by its suction force. Here, since the timing roller pair 25R and the photosensitive drum 12R have a peripheral speed difference of about 1%, the transfer material conveying speeds may vary, but the speeds reverse and the photosensitive drum 12R becomes faster. Absent. Further, the transfer material transport speed of the timing roller pair 25R is set to the photosensitive drum 12R.
As shown in FIG. 3, since the transfer material P is absorbed by forming a loop between the timing roller pair 25R and the photosensitive drum 12R, the deviation of a speed faster than the above does not adversely affect the image formation.

In the first image forming unit 10R, between the photosensitive drum 12R and the fixing device 27R, the first image forming unit 10R to the second image forming unit 10L.
Between the fixing device 27R and the timing roller pair 25L, between the timing roller pair 25L and the photosensitive drum 12L in the second image forming unit 10L, and between the photosensitive drum 12L and the fixing device 27L in the second image forming unit 10L. The same applies to the above configuration.

That is, by making the transfer material transport speed of the transport means located upstream in the transport direction of the transfer material P slightly higher than that of the downstream transport means, the transfer material transport speed of each transport means varies. Even in such a case, the speed difference can be absorbed by the loop of the transfer material P formed between the transporting means.

However, as described above, the fixing devices 27R, 2
7L has a greater variation in the transfer material transport speed than the other transport means, and therefore the speed difference between the transport means located upstream and downstream thereof is also set to a large value of 5 mm / s.

By setting the transfer material transfer speed of each transfer means as described above, the transfer material transfer speed of the downstream photosensitive drum 12L is about 5% slower than that of the upstream photosensitive drum 12R.

According to the configuration of the first embodiment described above,
Tension of the transfer material P, resulting image defects,
It is possible to provide an image forming apparatus capable of preventing the transfer material P from being damaged.

(Embodiment 2) In the above-mentioned Embodiment 1, the double-sided image dedicated image forming apparatus has been described, but the present invention is not limited to this embodiment.

The second embodiment will be described below with reference to the schematic front sectional view of the single-sided / double-sided switching image forming apparatus as the image forming apparatus shown in FIG. The same members as those in the above-mentioned drawings are designated by the same reference numerals.

In FIG. 4, the single-sided / double-sided switching image forming apparatus is compared with FIG. 1 shown in the first embodiment, and a single-sided sheet discharge tray 41 as a sheet discharging unit, a single-sided sheet discharge path 65, and a switching unit. A flapper 67 is added. In addition, parts that are not particularly described have the same configuration as in the first embodiment.

In the second embodiment, the first transfer material P
In the case of image formation on only one side, the operation of the second image forming unit 10L is configured to be stopped except for the one-sided sheet discharge path 65. Therefore, as compared with the first embodiment, the operation amount of about half is used for the one-sided dedicated image. It can be used as a forming device. In such a case, by switching the switching flapper 67, the transfer material P that has exited from the fixing device 27R on the upstream side enters the single-sided paper discharge path 65, and is discharged to the single-sided paper discharge tray 41 through it. It

When performing double-sided image formation in which images are formed on the front and back surfaces of the transfer material P, the entire apparatus, that is, the first and second image forming units 10R and 10L are operated to form a double-sided image. It has a structure that can be formed. In such a case, the switching flapper 6
By the action of 7, the transfer material P exiting the fixing device 27R on the upstream side.
Is conveyed to the timing roller 25L on the downstream side, and thereafter, a double-sided image is formed as in the first embodiment described above.

In such a single-sided / double-sided switching image forming apparatus, when the double-sided image is formed, the transfer material conveying speed of each conveying means is the same as that in the first embodiment.
That is, the transfer material conveying speed of the conveying means in the first image forming unit 10R is set to the second image forming unit 10L.
The transfer material conveying speed of the transfer means is set higher than the transfer material conveying speed of the transfer means, and the conveying material conveying speed of each conveying means is gradually decreased along the transfer material P conveying direction.

As described above, according to the second embodiment, the same effect as that of the first embodiment can be obtained, and the single-sided image forming apparatus can be comfortably used.

[0055]

As described above, according to the present invention,
In each of the transporting means for transporting the transfer material provided in the first and second image forming units, the transport speed of the transfer material passing through the upstream transport means is lower than the transport speed of the transfer material passing through the downstream transport means. By making the speed faster, it is possible to avoid the pulling of the transfer material that occurs while the transfer material is conveyed over each member when the both image forming units are operated. As a result, it is possible to provide an excellent image forming apparatus which does not cause image blurring or transfer material clogging.

[Brief description of drawings]

FIG. 1 is a schematic front sectional view of a double-sided image dedicated image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram showing transfer material transport speed of each transport means in the double-sided image dedicated image forming apparatus according to the first embodiment of the present invention.

FIG. 3 is a schematic front sectional view of a double-sided image dedicated image forming apparatus according to Embodiment 1 of the present invention.

FIG. 4 is a schematic front sectional view of a single-sided / double-sided switching image forming apparatus according to a second embodiment of the present invention.

FIG. 5 is a schematic front sectional view showing a conventional image forming apparatus.

FIG. 6 is a schematic front sectional view showing a conventional image forming apparatus.

FIG. 7 is a schematic front view showing a conventional image forming apparatus.

[Explanation of symbols]

1 device body 10R First image forming unit 10L second image forming unit 11 exposure means 12R, 12L photosensitive drum 13 Pre-exposure lamp 14 Primary charger 15 Developer 16 Transfer charger 17 Separate static elimination needle 18 cleaner 19 Suction device 20 paper cassettes 25R, 25L Timing roller pair 26R, 26L Conveyor belt 27R, 27L fixing device 28 Paper ejection roller pair 40 paper output section 41 Single-sided output tray 50 connection paths 65 Single-sided paper ejection path 67 Switching flapper 100 device body 101, 102 image forming unit 121, 122 Timing roller pair 131, 132 fixing roller 151, 152 image carrier 161, 162 image forming means 182 Paper ejection roller 201, 202 paper feeding means 301, 302 transfer material cassette 401 paper output unit P transfer material

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G03G 21/00 370 G03G 21/00 372 F term (reference) 2H027 DA20 DC04 DC05 DC11 ED16 ED17 ED19 ED24 ED25 EE03 FA13 2H028 BA06 BA16 BB04 BC01 2H033 AA46 BA01 BA02 BA08 BA10 BA11 BA12 BA25 BA59 BB01 BB28 CA22 CA36 2H072 AA32 AB14 AB15 BB09 3F049 DA12 EA10 EA12 LA03 LB01

Claims (4)

[Claims] 1. A first transfer means for transferring a toner image on a first image carrier on which an image is formed onto a transfer material by a first transfer means.
And a second image forming means for transferring the toner image on the second image carrier on which the image is formed onto the transfer material by the second transfer means. A second image forming unit having at least the second image forming unit is arranged in front of and behind in the conveying direction of the transfer material, and after the toner image is transferred to the first surface of the transfer material by the first image forming unit, the second image is formed. In an image forming apparatus capable of transferring a toner image to the second surface of the transfer material by the forming means, the first speed of the transfer material passing through the first image forming means passes through the second image forming means. The transfer material is fed at a third speed lower than the first speed from the first image forming section to the second image forming section at a speed higher than the second speed of the transfer material to be transferred to the second image forming section. Is a fourth speed lower than the third speed and higher than the second speed Image forming apparatus characterized by receiving a transfer material. 2. The first image forming section has first fixing means for fixing the toner image transferred onto the first surface of the transfer material by the first image forming means, and the second fixing means is provided. The image forming unit has second fixing means for fixing the toner image transferred onto the second surface of the transfer material which has passed through the first fixing means by the second image forming means, and the first fixing means. 2. The image forming apparatus according to claim 1, wherein the conveyance speed of the transfer material passing through the fixing means is set higher than the conveyance speed of the transfer material passing through the second fixing means. 3. The image forming apparatus according to claim 1, wherein the transfer material supply speed for supplying the transfer material toward the first image carrier is set higher than the first speed. 4. A paper feed means for feeding a transfer material to the image forming means, and a paper ejecting means for ejecting the transfer material from the image forming means with respect to the predetermined image forming means. The image forming apparatus according to any one of claims 1 to 3, which is characterized in that.