JPH09188439A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the occurrence of disturbance of a transfer image and fouling of a part due to contact with accumulated toner as flatness of the paper materials in a fixing unit is maintained. SOLUTION: A paper material conveyance guide 201 is arranged between a transfer part consisting of a photo-sensitive drum 103 and a transfer roller 113 and a fixing unit having an fixing roller 116 and a pressure roller 117, and a rib 202 is arranged in the vicinity of the tip part on the fixing side of the guide 201 and a specific difference in a stage is formed in the tip part of the guide 201. This constitution conveys the paper material without contact with the tip part on the guide 201, where toner is accumulated by the rib 202, before the paper material enters a nip between the fixing roller 116 and a pressure roller 117 but brings the paper material into contact with the tip part of the guide 201 for squeezing before the paper material enters the nip part and ensures flatness.

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 a printer or a copying machine, and more particularly to improving image quality by improving sheet material feeding by sheet material conveying guide means.

[0002]

2. Description of the Related Art FIG. 11 shows a schematic configuration example of a conventionally known image forming apparatus. This figure is a schematic cross-sectional configuration diagram of an image forming apparatus that applies an electrophotographic process technique to form an image with a laser beam. In FIG. 11, reference numeral 101 denotes a laser light source, and the laser light source 101 is the photosensitive drum 10 in the process cartridge 102 as an image forming means.
The surface of 3 is irradiated with the laser beam L. At this time, the surface of the photosensitive drum 103 is uniformly charged by the charging unit 104, and the laser beam L is applied to the surface of the photosensitive drum 103.
Is irradiated to form an electrostatic latent image. Then, the electrostatic latent image is conveyed to a portion facing the developing device 105 also disposed in the process cartridge 102 by the rotation of the photosensitive drum 103 in the direction of the arrow, and is developed as a toner image by the developing device 105. .

On the other hand, the sheet material P stored in the sheet material stacking cassette 106 is pushed up by the urging plate 108 urged by the spring 107, and the sheet material supply roller 1
The sheet material supply roller 109 is in contact with the sheet material supply roller 109 and is sequentially supplied one by one by the rotation of the sheet material supply roller 109 in the direction of the arrow.

The sheet material P is the registration roller 1.
After being held in the leading edge posture at 11, the sheet is sequentially fed to the transfer portion through the sheet material conveyance guide 112 at regular intervals. The sheet material supply roller and the registration roller are provided with an intermittent operation mechanism (not shown) such as a clutch in order to keep the feeding interval constant.

The sheet material P sent in this way passes through the facing portion of the photosensitive drum 103 on which the toner image is formed as described above and the transfer roller 113 as an image transfer means, and at this time, the sheet material P is transferred to the transfer roller 113. The toner image on the photosensitive drum 103 is transferred to the sheet material P.

Then, the transferred sheet material P is guided by a sheet material conveying guide 114 which is a sheet material conveying guide means and is sent to a fixing device 115 which is a fixing means, and a pressure contact portion (a pressure contact portion between a fixing roller 116 and a pressure roller 117 ( Hereinafter, the image is fixed by being heated and pressed by being nipped and conveyed at a nip portion).

Further, the sheet material P after fixing passes through the sheet material conveying guide 118 and the sheet material discharging roller 11
The sheet is conveyed by the sheet material 9 and is further ejected to the sheet material placing portion 122 by the sheet material ejection roller 121 via the sheet material conveyance guide 120.

As described above, in the conventional image forming apparatus, the plurality of sheet material conveying guides are provided in the apparatus, and the sheet material is smoothly conveyed to form a good image.

When the sheet material P is loosened between the transfer portion and the fixing device, waviness occurs in the width direction of the sheet material P, and this waviness causes uneven gloss of the image, wrinkles, and the like. By setting the peripheral speed of the fixing roller 116 to be slightly higher than the peripheral speed of the photosensitive drum 103, the occurrence of slack in the sheet material P between the transfer portion and the fixing device is prevented, and the sheet material guide 114 is formed as follows. The flatness of the sheet material is ensured by squeezing the sheet material at the tip of the.

That is, as shown in FIG. 12, the sheet material P discharged from the transfer portion where the photosensitive drum 103 and the transfer roller 113 face each other is applied to the fixing roller 116 while contacting the conveying surface of the sheet material conveying guide 114. Pressure roller 1
The sheet material P is conveyed to the nip portion 17, but the leading end portion of the sheet material P does not directly enter the nip portion, but once comes into contact with the surface of the fixing roller 116, and then the nip portion is rotated as the fixing roller 116 rotates. Then, due to the difference in peripheral speed between the fixing roller 116 and the photosensitive drum 103, the path 123 as shown in FIG. 12 is followed, and the slack is prevented.

Further, FIG. 1 is an enlarged view of part A of FIG.
As shown in FIG. 3, the tip end of the sheet material conveyance guide 114 on the fixing roller 116 side is installed so as to project onto the path 123, so that the sheet material P before entering the nip portion is conveyed to the tip end of the sheet material conveyance guide 114. The sheet material P was slightly squeezed to secure the flatness of the sheet material P while passing through the fixing device.

[0012]

However, in the above-mentioned conventional image forming apparatus, when the image is transferred into the image forming apparatus, a very small amount of toner scattered in minute amounts adheres to the surface of the transfer roller 113 (not shown). Every time the sheet material P passes over the transfer roller 113, the sheet material P adheres to the back surface (the surface opposite to the drawing surface) of the sheet material P and is conveyed to the fixing device 115. Therefore, the tip of the sheet material conveyance guide 114 as described above. When the toner is squeezed, the adhered toner may drop onto the tip.

The dropped toner is melted because the temperature near the entrance of the fixing device is high, and as shown in FIG. 13, a small amount of the toner adheres and accumulates on the end of the sheet material conveying guide 114 on the fixing device side. In this state, when the accumulated height of the toner exceeds a certain value, the leading edge of the sheet material P that has advanced on the sheet material conveyance guide 114 may be caught by the adhered toner, as shown in FIG. there were.

Due to this caught shock, the image being transferred may be disturbed or toner may scatter in the unfixed image after transfer, resulting in deterioration of the image quality. Sheet material conveyance guide 1
14 When the sheet material P passes over the leading edge of the sheet material, the sheet material P is peeled off from the surface of the sheet material transport guide 114 and reattached to the fixing roller 116, the pressure roller 117, the back surface of the sheet material, etc. It may have been a cause of stains.

In extreme cases, these phenomena may occur from about 2000 to 6000 sheets after the start of movement, and it may be difficult to maintain the quality within the movable life of the fixing device.

Further, as a result of the study, it is easy to prevent the toner scattering outside the image forming apparatus, but regarding the toner scattering inside the image forming apparatus, the relation between the sheet material jam (jam) release processing in the unfixed state is concerned. In fact, it proved difficult to eradicate it.

Therefore, the present invention provides an image forming apparatus capable of reducing the abnormal image and the stain of parts due to the contact with the accumulated toner while maintaining the flatness of the sheet material in the fixing device. Has an aim.

[0018]

According to the first invention of the present application, the above object is to provide an image forming means for forming an image by a predetermined image forming process, and an image transfer for transferring the image to a sheet material. In an image forming apparatus, a means, a fixing means for fixing the image transferred to the sheet material on the sheet material, and a sheet material conveying guide means for guiding the sheet material from the image transfer means to the fixing means. This is achieved by providing a step having a predetermined height on the upstream side of the leading end portion in the sheet material transport direction in the vicinity of the leading end portion of the sheet material transport guide means on the fixing means side.

According to the second aspect of the present invention,
The above-mentioned object is achieved in the above-mentioned first invention in that the step is formed by ribs arranged in parallel in the width direction of the sheet material conveying guide means.

Further, according to the third invention of the present application, the above-mentioned object is achieved in the above-mentioned first invention, in that the step is formed by bending the sheet material conveying guide means.

According to the fourth invention of the present application,
The above object is achieved by the sheet material conveying direction from the image transfer means to the fixing means being formed substantially horizontally in any one of the first to third inventions.

Further, according to a fifth invention of the present application, in the above object, in any one of the first invention to the third invention, the sheet material conveying direction from the image transfer means to the fixing means is This is achieved by being formed substantially vertically.

That is, according to the first invention of the present application, when the sheet material conveyed from the image transfer means is guided to the fixing means by the sheet material conveyance guide means, the sheet material conveyance guide means is provided in the vicinity of the tip end portion of the sheet material conveyance guide means. Due to the step difference, the sheet material reaches the fixing means without contacting the tip end portion where the toner is accumulated, so that the accumulated toner is not caught unlike the conventional case, and the disorder of the transfer image or the toner scattering does not occur. .

In the second aspect of the present application, the step formed by the ribs allows the sheet material to reach the fixing means without contacting the leading end portion where the toner is accumulated, and the conventional accumulated toner is obtained. To prevent the transfer image from being disturbed and toner from scattering.

Further, according to a third aspect of the present invention, a step formed by bending the sheet material conveying guide means allows the sheet material to reach the fixing means without contacting the leading end portion where the toner is accumulated. In addition, it is possible to prevent the toner from being caught by the accumulated toner as in the conventional case, and to prevent the disorder of the transferred image and the toner scattering.

Further, a fourth invention according to the present application is the image forming apparatus, wherein the sheet material conveying direction from the image transfer means to the fixing means is formed substantially horizontal, and the first invention to the third invention.
Since the sheet material conveying guide means provided with the step according to any one of the inventions is provided, the step allows the sheet material to reach the fixing means without coming into contact with the leading end portion where the toner is accumulated. It is possible to prevent the stuck toner from being trapped as described above and to prevent the disorder of the transferred image and the toner scattering.

Further, a fifth invention according to the present application is the image forming apparatus, wherein the sheet material conveying direction from the image transfer means to the fixing means is formed substantially perpendicular to the above first to third inventions. Since the sheet material conveyance guide means having the step described in any one of the above is provided, the stepped material allows the sheet material to reach the fixing means without coming into contact with the leading end portion where the toner accumulates, and the toner adheres and accumulates. In this type of image forming apparatus in which the speed is relatively high, it is possible to reliably prevent the accumulated toner from being caught, and to prevent disturbance of the transferred image and toner scattering.

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings.

(First Embodiment) First, a first embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, the image forming apparatus according to the present embodiment is an electrophotographic laser beam printer similar to the conventional example, but a rib 202 is provided on a sheet material conveyance guide 201 between a transfer unit and a fixing device. The point is different.
In addition, the same parts as those of the conventional example shown in FIG.

As shown in FIG. 1, a plurality of ribs 202 are arranged in parallel in the width direction of the sheet material conveyance guide 201 in the vicinity of the fixing device side tip portion on the sheet material conveyance guide 201. Has the role of providing a step with respect to the tip of the.

In such a structure, the sheet material P after the image transfer has a pressure contact portion (hereinafter referred to as a nip) between the fixing roller 116 and the pressure roller 117 along various paths on the sheet material conveyance guide 201 as shown in FIG. However, at this time, the leading edge of the sheet material P advances while contacting the surface of the rib 202 on the sheet material conveyance guide 201, and comes into contact with the fixing roller 116.

After contacting the fixing roller 116, the fixing roller 1 rotates as the fixing roller 116 rotates.
16 enters the nip portion of the pressure roller 117, but since the peripheral speed of the fixing device is set to be slightly higher than the peripheral speed of the photosensitive drum, the sheet material P is drawn to the fixing device side.
Schematically, it changes to a feed route such as the route 203 shown in FIG.

At this time, since the leading end of the sheet material conveyance guide 201 is arranged so as to project onto the path 203,
The contact pressure of the sheet material P becomes the highest, the toner transferred from the transfer roller 113 to the back surface of the sheet material P is squeezed off from the sheet material P at the leading end of the sheet material conveyance guide 201, as shown in FIG. Start melting, adhesion, and deposition.

However, when the sheet material P sent next advances with the leading edge in contact with the rib 202, the rigidity of the sheet material itself does not contact the leading edge of the sheet material conveying guide 201 and directly reaches the fixing roller 116. Abut. Therefore,
Even if the above-described accumulated toner is present, since the step is formed by the rib 202 with respect to the tip end portion of the sheet material conveyance guide 201, the sheet material P advances without being caught by the accumulated toner, and image disturbance occurs. Occurrence is prevented.

After entering the nip portion between the fixing roller 116 and the pressure roller 117, the path of the sheet material P changes to a feeding path like the path 203, and the back surface of the sheet material contacts the tip of the sheet material conveying guide 201. It is sent while being squeezed. That is, also in the apparatus of the present embodiment, the leading end of the sheet material conveyance guide 201 is located higher than the nip position between the fixing roller 116 and the pressure roller 117, and the sheet material is squeezed to remove the sheet material at the fixing inlet. The flatness of the sheet material during fixing is ensured by suppressing the occurrence of uneven gloss and wrinkles of the image due to waviness.

As described above, before entering the nip portion, the rib 202 allows the sheet material P to be smoothly transported without abutting the accumulated toner, and after entering the nip portion, the sheet material transport guide is introduced. The flatness is ensured by the contact with the tip portion of 201, and a good fixing operation is performed without image distortion, uneven gloss, and wrinkles.

As shown in FIG. 3, the height of the rib 202 is made lower than the path 203 after the sheet material P has entered the nip portion by an appropriate amount δ so that the rib 202 does not project onto the path 203. It is necessary to.

As described above, in the present embodiment, toner accumulation cannot be prevented, but since the leading edge of the sheet material P does not pass through the leading edge of the sheet material conveyance guide 201 before entering the nip portion, image distortion and toner And the like are suppressed to a level where practically no problem occurs within the life of the apparatus, and as a result of the experiment, abnormal image generation did not occur unless the number of image forming operations of 50 to 100 times or more of the conventional number was performed.

(Second Embodiment) Next, the second embodiment of the present invention
The embodiment will be described with reference to FIGS. 4 to 6. In the present embodiment, the present invention is applied to a vertical conveyance type image forming apparatus as shown in FIG. 4, and the same parts as those in FIG.

In this apparatus, the peripheral speed of the fixing roller 116 is set higher than that of the horizontal transfer system relative to the peripheral speed of the photosensitive drum 103, so that the toner deposition rate is high, and therefore the sheet material transfer guide means, which is a sheet material transfer guide means, is used. Reference numeral 204 is an integral unit with the fixing device to match the life of the fixing device. That is, the fixing device life is shorter than the device life.

Also in this embodiment, a plurality of ribs 205 are provided on the sheet material conveying guide 204 in the width direction of the sheet material conveying guide 204 in order to provide a step with respect to the tip of the sheet material conveying guide 204. They are arranged in parallel. Therefore, as shown in FIG. 5, which is an enlarged view of the periphery of the sheet material conveyance guide 204, the sheet material P is conveyed along the ribs 205, so that the sheet material P directly contacts the fixing roller 116 without coming into contact with the leading ends of the ribs 204. It does not get caught in the accumulated toner.

Further, in this embodiment as well, the height of the tip of the rib 205 is set lower than the height of the sheet material conveying path 206 after entering the nip portion by an appropriate amount δ, as shown in FIG. After the material P enters the nip portion between the fixing roller 116 and the pressure roller 117, the state of the path 206 is established, and the flatness is ensured.

As described above, according to this embodiment, even in the vertical conveyance type image forming apparatus, since the leading edge of the sheet material does not pass through the leading edge of the sheet material conveying guide 204 before entering the nip portion, the image is formed. Disturbance, toner scattering, and the like can be suppressed to a level that causes no practical problems within the life of the fixing device.

(Third Embodiment) Next, the third embodiment of the present invention will be described.
The embodiment will be described with reference to FIGS. 7 and 8. In addition,
The same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

In this embodiment, a rib is not provided on the sheet material conveying guide, but a step is formed by bending the leading end side of the sheet material conveying guide 207 as shown in FIG. The present invention is applied to a horizontal conveyance type image forming apparatus similar to the embodiment. Therefore, the guide 20
The sheet material conveyed while being in contact with 7 contacts the fixing roller 116 without being caught by the accumulated toner, and does not disturb the transferred image.

Also in the present embodiment, the height of the tip of the step portion is set lower than the sheet material conveying path 208 after entering the nip portion by an appropriate amount δ, as shown in FIG. As a result, after the sheet material P has entered the nip portion between the fixing roller 116 and the pressure roller 117, the state of the path 208 is established and flatness is ensured.

As described above, according to this embodiment, since the leading edge of the sheet material does not pass through the leading edge of the sheet material transport guide 207 before entering the nip portion, image disturbance, toner scattering, etc. are within the life of the apparatus. It can be suppressed to a level where practically no problem occurs.

(Fourth Embodiment) Next, the third embodiment of the present invention
The embodiment will be described with reference to FIGS. 9 and 10. The same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

As shown in FIG. 9, the present embodiment is provided with a step by bending the sheet material conveying guide 209, and is applied to a vertical conveying type image forming apparatus similar to that of the third embodiment. It is something. Therefore, the sheet material P conveyed while contacting the sheet material conveyance guide 209 does not get caught by the accumulated toner and abuts on the fixing roller 116, so that the transfer image is not disturbed.

Also in the case of this embodiment, the height of the tip of the step portion is set lower than the sheet material conveying path 210 after entering the nip portion by an appropriate amount δ, as shown in FIG. Therefore, the sheet material P includes the fixing roller 116 and the pressure roller 1.
After entering the nip portion of 17, the state of the path 210 is established, and the flatness is ensured.

As described above, according to the present embodiment, since the leading edge of the sheet material does not pass through the leading edge of the guide 209 before entering the nip portion, image disturbance, toner scattering, etc. are practical problems within the life of the apparatus. Can be suppressed to a level that does not occur.

As described above, the present invention is not limited to one form, and various modifications can be made. Further, in the above-mentioned apparatus, the application is applied only to the fixing inlet, but it is needless to say that the application can be applied to other portions after the image transfer.

In the above embodiment, the present invention is applied to the image forming apparatus provided with the fixing device of the type using the fixing roller, but it is disclosed in JP-A-63-313182 and JP-A-2-157878. JP-A-4-44075-44
As disclosed in Japanese Patent Publication No. 083 or the like, a heat source is adhered to one side of a heat-resistant film and a recording material is adhered to the other side of the heat-resistant film, and the sheet material is moved along with the film so that heat energy of the heat source is transferred to the sheet through the film. An image forming apparatus provided with a fixing member of a system for applying a material and a toner image on the sheet material, and further, to the above heat-resistant film having a metal layer or a roller made of metal, eddy current is generated by magnetic induction heating. The present invention can also be applied to an image forming apparatus provided with a so-called magnetic induction heating type fixing device that heats by heating.

[0054]

As described above, the first embodiment according to the present application is described.
According to the invention, since the step is provided in the vicinity of the leading end of the sheet material conveying guide means, the sheet material can reach the fixing means without contacting the leading end portion where the toner is accumulated, and the transfer image is disturbed. The toner scattering and the like can be suppressed to practically no problem within the life of the apparatus main body or unit parts, and the image quality can be significantly improved. The practical effect is very large.

In the second invention of the present application, the step formed by the ribs allows the sheet material to reach the fixing means without coming into contact with the leading end portion where the toner is accumulated, and the conventional accumulated toner is obtained. It is possible to prevent clogging of the transfer image and to suppress the disturbance of the transferred image and the toner scattering within the life of the main body of the device or the unit parts to a practically no problem.
The image quality was also greatly improved. The practical effect is very large.

Further, according to the third invention of the present application, the step material formed by bending the sheet material conveying guide means allows the sheet material to reach the fixing means without contacting the leading end portion where the toner is accumulated. , It is possible to prevent the stuck toner from being trapped as in the past, and to suppress the disturbance of the transferred image and the toner scattering within the service life of the main body of the device or unit parts to a practically problematic level, and the image quality is greatly improved. I was able to improve. The practical effect is very large.

Further, a fourth aspect of the present invention is an image forming apparatus in which the sheet material conveying direction from the image transfer means to the fixing means is formed to be substantially horizontal, and the above first to third aspects.
Since the sheet material conveying guide means provided with the step according to any one of the inventions is provided, the step allows the sheet material to reach the fixing means without coming into contact with the leading end portion where the toner is accumulated. It is possible to prevent the stuck toner from being trapped in such a way as described above, and it is possible to suppress the disorder of the transferred image and the toner scattering to a practically no problem within the life of the main body of the apparatus or the unit parts, and to greatly improve the image quality. I was able to. The practical effect is very large.

Furthermore, a fifth aspect of the present invention is an image forming apparatus in which the sheet material conveying direction from the image transfer means to the fixing means is formed substantially vertically, and the fifth aspect of the invention is the same as the first aspect of the invention. Since the sheet material conveyance guide means having the step described in any one of the above is provided, the stepped material allows the sheet material to reach the fixing means without coming into contact with the leading end portion where the toner accumulates, and the toner adheres and accumulates. In this type of image forming device where the speed is relatively high, it is possible to reliably prevent the accumulated toner from being caught, and to prevent the disturbance of the transferred image and the toner scattering within the life of the main body of the device or the unit parts. The image quality could be greatly improved. The practical effect is very large.

[Brief description of the drawings]

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

FIG. 2 is a diagram illustrating a step of a sheet material conveyance guide unit and a sheet material conveyance path according to the first embodiment of the present invention.

FIG. 3 is a diagram showing the vicinity of the fixing device side tip portion of the sheet material conveyance guide means in the first embodiment of the present invention.

FIG. 4 is a diagram showing a schematic configuration of an image forming apparatus according to a second embodiment of the present invention.

FIG. 5 is a diagram illustrating a step of a sheet material conveyance guide unit and a sheet material conveyance path according to a second embodiment of the present invention.

FIG. 6 is a diagram showing the vicinity of a fixing device side tip portion of a sheet material conveying guide unit according to a second embodiment of the present invention.

FIG. 7 is a diagram illustrating a step of a sheet material conveyance guide unit and a sheet material conveyance path according to a third embodiment of the present invention.

FIG. 8 is a diagram showing the vicinity of a fixing device side tip portion of a sheet material conveying guide unit according to a third embodiment of the present invention.

FIG. 9 is a diagram illustrating a step of a sheet material conveyance guide unit and a sheet material conveyance path according to a fourth embodiment of the present invention.

FIG. 10 is a view showing the vicinity of a fixing device side tip portion of a sheet material conveyance guide unit according to a fourth embodiment of the present invention.

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

FIG. 12 is a diagram illustrating a sheet material conveyance path around a fixing device in a conventional image forming apparatus.

FIG. 13 is a diagram showing the vicinity of a fixing device side tip portion of a sheet material conveyance guide unit in a conventional image forming apparatus.

[Explanation of symbols]

102 process cartridge (image forming means) 113 transfer roller (image transfer means) 115 fixing device (fixing means) 201, 204, 207, 209 sheet material conveying guide (sheet material conveying guide means) 202, 205 rib P sheet material

Claims (5)

[Claims] 1. An image forming means for forming an image by a predetermined image forming process, an image transfer means for transferring the image to a sheet material, and a fixing means for fixing the image transferred on the sheet material to the sheet material. And a sheet material conveyance guide means for guiding the sheet material from the image transfer means to the fixing means, in the vicinity of the tip of the sheet material conveyance guide means on the fixing means side, An image forming apparatus, wherein a step having a predetermined height is provided on the upstream side in the sheet material conveying direction with respect to the leading end. 2. The image forming apparatus according to claim 1, wherein the step is formed by ribs arranged side by side in the width direction of the sheet material conveying guide means. 3. The image forming apparatus according to claim 1, wherein the step is formed by bending the sheet material conveying guide means. 4. The image forming apparatus according to claim 1, wherein the sheet material conveying direction from the image transfer means to the fixing means is formed substantially horizontal. 5. The image forming apparatus according to claim 1, wherein the sheet material conveying direction from the image transfer means to the fixing means is formed substantially vertical.