JP2000296934A - Image forming device - Google Patents

Abstract

(57) Abstract: Provided is an image forming apparatus having a one-pass double-sided function without causing image defects or increasing a driving load. SOLUTION: Upstream / downstream image forming unit 10
U and 10L are stacked one on top of the other in such a manner that the transfer material transport directions are alternately arranged, and are connected by a connection path 50. A switching flapper 51 for switching whether the transfer material discharged from the 10 L is sent to the paper output unit 40 or the connection path 50 is configured. Connection path 5
A cooling fan 503 for generating an air flow from the outside to the inside of the apparatus main body is provided in the middle of 0. This prevents the downstream-side image forming unit 10U from being heated by the high-temperature sheet P discharged from the upstream-side image forming unit 10L, and prevents solidification of the toner stored in the developing device. ,

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrophotographic or electrostatic recording type image forming apparatus such as a copying machine or a printer.

[0002]

2. Description of the Related Art Conventionally, there has been known an image forming apparatus having a plurality of image forming means, particularly an image forming apparatus having a so-called one-pass double-sided function having image forming means for each side for forming images on both sides of a transfer material. Proposed.

FIG. 7 shows an example of a conventional image forming apparatus.
The image forming apparatus of the present embodiment has two image forming units 101 and 102 in an apparatus main body 10, and each of the image forming units 101 and 1.
02, paper feeding means 201, 202, transfer material cassette 3
01, 302, and paper discharge units 401, 402 are connected respectively.

The transfer direction of the transfer material of the two image forming units 101 and 102 is configured to cross each other.

A connecting path 500 is provided as connecting means for connecting two image forming means 101 and 102 to form an image on both sides and conveying a transfer material. A switching flapper 501 that switches between transferring the transfer material discharged from the upstream image forming unit 101 to the paper discharge unit 401 and feeding the transfer material to the connection path 500 is provided at the most upstream portion of the connection path 500.

In the double-sided image forming mode, the switching flapper 501 is switched to the connection path 500 side, and the transfer material is fed from the transfer material cassette 301 so that the two image forming means 1
01 and 102, the sheet is further discharged to the sheet discharge unit 402.

In the single-sided image forming mode, the transfer material is fed from the transfer material cassette 301 or 302 and is discharged through the image forming means 101 and 102, respectively.
1, 402.

Further, by simultaneously operating these two image forming means, it is possible to form a single-sided image with high productivity.

An image forming apparatus having a configuration shown in FIG. 8 has been proposed as a so-called one-pass double-sided function. 7, the same elements as those of the image forming apparatus of FIG. 7 are denoted by the same reference numerals.

This apparatus is configured so that the transfer direction of the transfer material of the image forming means 101 and 102 is the same as that of the image forming apparatus shown in FIG. Accordingly, the image forming surface of the transfer material is different between the upstream image forming means 101 and the downstream image forming means 102, and the image forming surface of the transfer material in the upstream image forming means 101 is lower, and the transfer is performed in the downstream image forming means 102. The image forming surface of the material is on the upper side.

In such an image forming apparatus, when operating the upstream image forming means 101 in the one-sided mode,
This is a so-called face-down paper discharge in which the image forming surface is discharged on the lower side. On the other hand, when the downstream-side image forming unit 102 is operated, a so-called face-up discharge is performed in which the image forming surface is discharged on the upper side.

Thus, for example, when both the copier function and the printer function are provided, the copier function discharges the paper face-up using the downstream image forming means 102, and the printer function uses the upstream image forming means 101 to face the paper. It is possible to use them properly, such as discharging paper when down.

[0013]

An image forming apparatus employing an electrophotographic method forms a latent image on a photosensitive drum as an image carrier using light, magnetism, electric charge, and the like, and develops the latent image. A transfer material transporting means for transporting the toner image to a transfer position of the image forming unit for visualizing the toner image; and a fixing means for fixing the toner image to the transfer material on which the toner image has been transferred at the transfer position by heat and pressure.

When the image forming apparatus having the one-pass double-sided function performs the image forming operation continuously for a long time, the transfer material heated by the fixing means of the upstream side image forming means 101 becomes
When the operation of passing through the downstream-side image forming unit 102 is continued, the ambient temperature particularly around the downstream-side image forming unit 102 increases.

On the other hand, the toner for developing a latent image has a property of solidifying when the temperature rises. When the temperature in the apparatus becomes higher than a certain temperature, an image defect occurs due to the solidified toner and the driving load of the developing device increases. However, there is a problem that a failure of the image forming apparatus is finally caused.

When one of the image forming units is configured such that the image forming surface of the transfer material is located below the gravitational direction, the unfixed image is not fixed on the lower side while the transfer material is conveyed from the image forming unit to the fixing unit. There has been a problem that the transfer material carrying the image comes into contact with a component below the transfer material due to gravity, causing image defects such as image blurring.

Accordingly, it is a main object of the present invention to provide an image forming apparatus having a one-pass double-sided function without causing image defects or increasing a driving load.

Another object of the present invention is to prevent image defects such as image distortion from occurring even when one of the image forming means is configured so that the image forming surface of the transfer material is on the lower side in the direction of gravity.
An object of the present invention is to provide an image forming apparatus having a pass double-side function.

[0019]

The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention provides:
At least one image carrier on which an image is formed, and a transfer unit that transfers a toner image on the image carrier onto a transfer material,
Heat fixing means for heating and fixing the toner image on the transfer material,
Wherein a plurality of image forming means are connected and arranged in series in the transfer material conveying direction, and a cooling means for keeping the transfer material at a proper temperature or lower is provided between the image forming means. An image forming apparatus.

The first image forming means for forming an image on the first surface of the transfer material, and the second image forming means on the back side of the first surface.
It is preferable to have the second image forming unit for forming an image on a surface. Preferably, the cooling means is a fan. It is preferable that a path connecting the plurality of image forming units is provided adjacent to an exterior member that covers the outside of the image forming apparatus main body.

At least one pair of transport rollers is provided on a path connecting the plurality of image forming means, and at least one of the transport roller pairs has a hollow structure in the axial direction, and one of the transport rollers Preferably, an airflow is generated from the shaft end to the other shaft end to cool the transport roller. Further, at least one of the plurality of image forming units holds a toner image on the lower side in the transport direction of the transfer material,
It is preferable that a suction / conveying unit for suctioning / holding the upper side of the transfer material and conveying the transfer material between the transfer unit and the thermal fixing unit is provided, and a fan used for the cooling unit also serves as a suction source of the suction / conveying unit.

[0022]

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

Embodiment 1 A first embodiment of the present invention will be described with reference to FIGS.

As shown in FIG. 1, the image forming apparatus 1 of this embodiment has two image forming units, ie, an image forming unit 1
0U and 10L are stacked one on top of the other so that the transfer material transport directions are alternately arranged, and are connected by a connecting path 50 as connecting means. The switching flapper 51 is configured to switch between transferring the transfer material P discharged from the side image forming unit 10L to the paper discharge unit 40 and the connection path 50. Since the configuration inside each of the image forming units 10U and 10L is common, only the upstream image forming unit 10L will be described, and the description of the downstream image forming unit 10U will be omitted.

A photosensitive drum 12, which is an image carrier, has an exposure means 11, a pre-exposure lamp 13, a primary charger 1 around the photosensitive drum 12.
4, a developing device 15, a transfer charging device 16, a separating static elimination needle 17, and a cleaner 18 are arranged to constitute a well-known electrophotographic process.

The exposure means 11 has a large number of light emitting elements such as LEDs arranged in the longitudinal direction of the photosensitive drum 12, and the light emission is controlled by a light emitting element driving circuit (not shown) in accordance with image data. One beam of light emitted from the exposure unit 11 is formed on the photosensitive drum 12 to form an electrostatic latent image. The electrostatic latent image is visualized as a toner image by the developing device 15.

A sheet (transfer material) P fed from a sheet feed cassette 20 disposed at a lower portion in the upstream image forming unit 10L is fed to a timing roller pair 2 by a transport roller 32.
The toner is transferred to the transfer charger 16 at the same time as the toner image on the photosensitive drum 12, and is transferred onto the sheet P by the action of the transfer charger 16.

The paper P on which the toner image has been transferred is separated from the photosensitive drum 12 by the action of the separation and static elimination needle 17, conveyed by a conveyance belt 26, and sent to a fixing device 27. Then, the toner image is fixed by heat and pressure in the fixing device 27, and thereafter, the sheet P is discharged out of the upstream image forming unit 10 </ b> L by the discharge roller pair 28.
When forming an image on one side of the sheet P, the discharged sheet P
Are sequentially stacked on a paper discharge tray 40 by an external paper discharge roller pair 29.

At this time, the upstream image forming unit 10L
In the above, the paper transport direction is switched to the discharge tray 40 side by moving the switching flapper 51 to the position shown by the dotted line rotating in the direction of arrow a.

Under these conditions, the upstream image forming unit 1
Since 0L and the downstream image forming unit 10U can form images independently of each other, when both are operated at the same time, productivity twice as high as the image forming speed unique to the image forming unit is secured.

On the other hand, when images are formed on both sides of the sheet P, the sheet P discharged from the upstream image forming unit 10L is held by the transport roller in the connecting path 50 by holding the switching flap 51 at the position shown by the solid line in the figure. The image is formed on the back side of the sheet P by the downstream image forming unit 10U through the pair of vertical path rollers 29 and 30, and is stacked on the sheet discharge tray 40U.

In this case, since there is no sheet reversing mechanism, that is, so-called one-pass double-sided image formation without a speed reduction factor, productivity at the same speed as the image forming speed unique to the image forming unit is secured. Will be.

With the above-described configuration, the present image forming apparatus can realize high productivity when forming images on one side or both sides.

FIG. 2 is a diagram showing a characteristic portion according to the present invention, and shows the vicinity of the connection path 50 in detail.

In FIG. 2, an outer guide 501 of the connecting path 50 is formed integrally with an outer cover which is an outer member of the apparatus main body 1. Also, a pair of vertical pass rollers 29, 30
A large number of ventilation holes 501a are arranged in a part of the outer guide 501 therebetween. The inner guide 502 is the outer guide 50
1 and a connecting path 50 is formed therebetween.

At the position of the inner guide 502 facing the air hole 501a of the outer guide 501, the air hole
a are arranged in large numbers. These ventilation holes 501a, 5a
The cooling fan 503 is located inside the machine at the position where the second fan 02a is formed.
Are provided to generate an air flow from the outside to the inside of the apparatus main body.

The air flow generated by the cooling fan 503 further passes through the duct 504, and the heat generated mainly by the fixing unit 27 in the upstream image forming unit 10L is transmitted by the plurality of ventilation holes 505 formed below the duct 504. While being sucked, it is discharged out of the machine from the discharge hole 506 on the rear side of the apparatus main body.

In this configuration, the connecting path 50 is
And the cooling fan 503 is forcibly cooled, so that the vicinity of the connection path 50 is always kept at the same temperature as the outside air temperature.

Therefore, the temperature of the downstream image forming unit 10U is prevented from rising due to the high-temperature sheet P discharged from the upstream image forming unit 10L.

Further, since the heat generated from the fixing device 27 of the upstream image forming apparatus 10L is sucked by the ventilation hole 505 of the duct 504, the heat generated from the fixing device 27 is transmitted to the downstream image forming apparatus 10U by convection. Is also prevented.

For this reason, the developing unit 1 of the upper image forming unit 10U, which is caused by a rise in the temperature inside the apparatus main body, particularly
5 is prevented from solidifying, and as a result,
It is possible to prevent image deterioration due to the solidified toner, and furthermore, failure of the apparatus due to an increase in the driving load of the developing device 18.

In this embodiment shown in FIG. 2, the cooling fan 503 is arranged on the inner guide 502 side.
Of course, as shown in FIG.

Embodiment 2 Next, a second embodiment of the present invention will be described with reference to FIGS.

In the present embodiment, a pair of transport rollers 512 and 513 are provided at an intermediate portion of the connection path 50.

The transport roller pairs 512 and 513 are formed of a thin pipe material, and have a hollow shape with both ends of the shaft opened. A plurality of ventilation holes 1a are provided in the body exterior part of the opening on the side of the device body. Further, a cooling fan 514 is provided at the other opening, that is, at the back side of the apparatus main body, and a plurality of ventilation holes 1b are provided at the exterior of the main body 1. The cooling fan 514 generates an airflow from the front side to the back side of the main body.

In this configuration, the hollow portions of the transport rollers 512 and 513 formed thin are always kept at the same temperature as the outside air temperature by the cooling fan 514.

Therefore, the sheet P in the high temperature state discharged from the upstream image forming unit 10L is transported by the pair of transport rollers 51.
It cools as it passes between 2,513,
The temperature of the downstream image forming unit 10U is prevented from rising.

For this reason, as described above, the upper image forming unit 1 which is caused by a rise in the temperature of the inside of the apparatus main body, especially the upper image forming unit 1
The solidification of the toner stored in the developing unit 15 of 0 U is prevented, and as a result, the image deterioration due to the solidified toner and the failure of the apparatus due to an increase in the driving load of the developing unit can be prevented.

Further, if the pair of transport rollers 512 and 513 are used, a desired cooling effect can be obtained without disposing the connecting path 50 in the vicinity of the exterior part of the main body 1.

Therefore, it is possible to cope with a case where an application such as a sorter or a paper feed deck is arranged on the side surface of the main body or a case where a connection path cannot be arranged on the side surface of the apparatus.
The degree of freedom in the device configuration can be increased.

In this embodiment, an example is shown in which a hollow roller is used for both of the transport roller pairs 512 and 513, but it is a matter of course that only one of them may be hollow.

For example, when a heat source is provided above the fixing roller pair 27, only the transport roller 513 on the heat source side of the transport roller pairs 512 and 513 may be a hollow roller.

Embodiment 3 Next, a third embodiment of the present invention will be described with reference to FIG.

In this embodiment, the image forming surface of the sheet P in the upstream image forming unit 10L is opposite (lower) to the image forming apparatus of the first embodiment shown in FIG. I have.

The present embodiment is characterized by the vicinity of the cooling means on the connecting path 50, and the other parts are the same as those of the first embodiment, so that the description will be omitted.

The conveyor belt 26 of the lower image forming apparatus 10L
A suction duct 506 for transporting the paper P while sucking the paper P upward is disposed in the inside. Suction duct 50
6, a large number of ventilation holes 506a are arranged on the surface on the paper transport side.

On the other hand, the outer guide 501 of the connecting path 50 is formed integrally with the outer cover of the apparatus main body 1. In addition, a large number of ventilation holes 501a are arranged in a part of the outer guide 501 between the pair of vertical path guides 29 and 30. The inner guide 502 faces the outer guide 501 and forms the connection path 50 therebetween. Similarly, at the position facing the air hole 501 of the outer guide of the inner guide 502, the air hole 5
02a are arranged in large numbers.

Further, a cooling duct 504 for cooling the connection path 50 is disposed inside the device of the ventilation hole 502a, and a fan 50 disposed on the rear outer cover of the main body 1 is provided.
7 is connected. The fan 507 generates an airflow in a direction for discharging the internal air out of the main body. The suction duct 506 provided on the conveyor belt 26 is connected to the cooling duct 504.

According to the above configuration, the cooling of the vicinity of the connection path 50 and the suction of the sheet P on the transport belt 26 can be simultaneously achieved by the operation of the fan 507.

For this reason, according to the present embodiment, not only the internal temperature rise is prevented, but also the unfixed image is carried in the image forming apparatus which is configured so that the image forming surface of the sheet P is on the lower side in the direction of gravity. Since the collected paper P is suctioned upward and conveyed, image defects such as image distortion can be prevented.

Further, as in the present embodiment shown in FIG. 6, an auxiliary fan 503 for further improving the cooling effect of the paper P on the connection path 50 is disposed on the outer guide 501 side, and external air is supplied to the cooling duct 504. You may send in.

Furthermore, a plurality of ventilation holes 505 may be arranged below the cooling duct 504 to absorb heat generated from the fixing device 27 of the upstream image forming apparatus 10L.

[0063]

As is apparent from the above description, according to the present invention, a plurality of image forming means are connected and arranged in series in the transfer material conveying direction, and the transfer material is placed between the image forming means. By providing a cooling unit for keeping the temperature below an appropriate temperature, it is possible to prevent the occurrence of image defects and an increase in driving load, and one of the image forming units moves the image forming surface of the transfer material downward in the direction of gravity. Even with this configuration, it is possible to prevent image defects such as image distortion.

[Brief description of the drawings]

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

FIG. 2 is an enlarged view of a main part showing a vicinity of a cooling unit of the image forming apparatus of FIG. 1;

FIG. 3 is an enlarged view of a main part showing a modification of the cooling means of FIG. 2;

FIG. 4 is a top sectional view showing a pair of conveying rollers according to a second embodiment of the present invention.

FIG. 5 is a cross-sectional view of the transport roller pair of FIG. 4 as viewed from line XX.

FIG. 6 is an overall configuration diagram showing a third embodiment of the image forming apparatus according to the present invention.

FIG. 7 is a schematic configuration diagram illustrating an example of a conventional image forming apparatus.

FIG. 8 is a schematic configuration diagram illustrating another example of a conventional image forming apparatus.

[Explanation of symbols]

10L Upstream image forming unit (image forming unit) 10U Downstream image forming unit (image forming unit) 12 Photosensitive drum (image carrier) 16 Transfer charger (transfer unit) 27 Fixing unit (thermal fixing unit) 50 Connecting path ( Connecting means) 503, 507 Fan (cooling means)

Claims (6)

[Claims] 1. An image carrier on which an image is formed, a transfer unit for transferring a toner image on the image carrier onto a transfer material, and a heat unit for heating and fixing the toner image on the transfer material. A plurality of image forming units including a fixing unit and a serial connecting unit arranged in series in the transfer material transport direction, and a cooling unit for maintaining the transfer material at an appropriate temperature or lower between the image forming units. An image forming apparatus comprising: 2. A first image forming means for forming an image on a first surface of a transfer material, and a second image for forming an image on a second surface behind the first surface. The image forming apparatus according to claim 1, further comprising a forming unit. 3. The image forming apparatus according to claim 1, wherein said cooling means is a fan. 4. The image forming apparatus according to claim 1, wherein the connecting means for connecting the plurality of image forming means is provided adjacent to an exterior member covering the outside of the image forming apparatus main body. 5. A transport roller having at least one pair of transport rollers on said connecting means, wherein at least one roller of said transport roller pair has a hollow structure in an axial direction, and one of said transport rollers has an axial end portion and the other has a hollow structure. The image forming apparatus according to claim 1, wherein an airflow is generated toward an end of the shaft to cool the transport roller. 6. A method according to claim 1, wherein at least one of said plurality of image forming means holds a toner image at a lower side in a conveying direction of a transfer material.
The image forming apparatus according to claim 3, further comprising a suction conveyance unit configured to hold and convey the image, wherein a fan used as the cooling unit also functions as a suction source of the suction conveyance unit.