JP2001142314A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device furnished with the high degree of freedom in layout of the image carrier periphery by realizing appropriate inserted of transfer paper in a transferring part with limited number of components. SOLUTION: This image forming device makes a transfer belt 11 disposed in such a manner that, in the transporting direction, the upstream side has an upward slope against the downstream side of the transferring part 20a, and regist rollers 12 held in contact with the leading end of transfer paper P in contact to an upward slope at an angle by providing the above upward inclination portion 11a as the lower side guide. In such a manner, the device is made possible to mount the regist roller 12 on the lower position, for instance, to lower the mounting position of the developing device 4a, therefore the degree of freedom in layout of the image carrier 2a periphery is enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for transferring a toner image on an image carrier to a transfer sheet conveyed by a transfer belt.

[0002]

2. Description of the Related Art In an image forming apparatus of a type in which a toner image on an image carrier such as a photosensitive drum is transferred onto a transfer sheet conveyed by a transfer belt, the transfer sheet is transferred to the transfer belt when transferring. If they are not kept close to each other, problems such as partial transfer failure and paper jam may occur. Therefore, for example, in Japanese Patent Application Laid-Open No. Hei 5-11632, as shown in FIG. 3, a registration roller 54 is provided diagonally above an opposing portion (transfer section 53) between a photosensitive drum 51 as an image carrier and a transfer means 52. The transfer paper P sent out by the registration roller 54 is provided with upper and lower paper feed guides 5.
5, an image forming apparatus has been proposed in which the transfer belt 56, which moves horizontally, is brought into contact with the transfer belt 56 obliquely from above at an angle. As a result, the transfer paper P is sequentially brought into close contact with the transfer belt 56 from the leading end thereof, and is inserted into the transfer section 53 in that state, so that problems such as transfer failure and paper jam due to the lifting of the transfer paper P can be prevented.

[0003]

However, in the above-mentioned conventional image forming apparatus, since the registration roller 54 and the paper feed guide 55 need to be provided obliquely above the transfer belt 56, the transfer section upstream of the photosensitive drum 51 is required. For example, it is necessary to install the developing device 57 at a higher position, so that there is a problem that the space around the photosensitive drum is pressed and the degree of freedom of layout is reduced. In addition, the provision of the upper and lower paper feed guides 55 increases the number of parts, which complicates the assembly process and increases the cost.
SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to realize appropriate insertion of a transfer paper into a transfer portion with a small number of parts, thereby increasing the degree of freedom in layout around an image carrier. It is to provide a high image forming apparatus.

[0004]

In order to achieve the above object, the present invention provides an image carrier, a transfer roller pressed against the image carrier, and an opposing portion between the image carrier and the transfer roller. An image forming apparatus comprising: a transfer belt that allows a transfer sheet to pass through a transfer section; and a registration roller that inserts the transfer sheet into the transfer section while causing the transfer sheet to follow the transfer belt. Is arranged so that the conveying direction on the upstream side of the transfer unit is inclined upward with respect to the conveying direction on the downstream side of the transfer unit. The image forming apparatus is configured such that the leading end of the transfer paper is brought into contact with the upwardly inclined portion of the transfer belt at an angle. As described above, the upstream of the transfer portion of the transfer belt is inclined upward, so that the transfer roller is brought into contact with the transfer belt at an angle, but the registration roller is positioned at a lower position. It is possible to increase the degree of freedom of the layout around the image carrier, for example, by lowering the installation position of the developing device. In addition, by using the upwardly inclined portion of the transfer belt as the lower guide, the number of components can be reduced, and the assembly process can be simplified and the cost can be reduced.

Further, the transfer speed of the transfer paper by the registration roller is set slightly higher than the transfer speed of the transfer paper in the transfer portion, and the bottom surface of the developing device provided on the upstream side of the image carrier is raised. If the upper guide and the lower guide formed by the upwardly inclined portion of the transfer belt form a space opened toward the upstream side in the transfer paper transport direction, the transfer paper can be transferred to the bottom surface (upper side) of the developing device. guide)
In the space formed between the transfer belt and the upwardly inclined portion (lower guide), the transfer paper can be bent to absorb the speed difference between the registration roller and the transfer unit. Therefore, it is not necessary to strictly adjust the speed of the registration roller, and it is possible to allow a margin in setting the speed of the registration roller. Further, in order to prevent the leading end of the transfer paper from being bent or the like, the contact angle θ of the leading end of the transfer paper to the upwardly inclined portion of the transfer belt is desirably set within the range of 0 ° <θ ≦ 30 °. The present invention is suitable for, for example, a tandem-type image forming apparatus in which a plurality of sets of the image carrier and the transfer unit are provided in series.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments and examples of the present invention will be described below with reference to the accompanying drawings to provide an understanding of the present invention. The following embodiments and examples are examples embodying the present invention, and do not limit the technical scope of the present invention. Here, FIG. 1 is an enlarged schematic view of the most upstream transfer section 20a of the tandem type full-color printer according to the embodiment of the present invention and the vicinity thereof, and FIG. 2 is a tandem type full-color printer according to the embodiment of the present invention. 1 is an overall schematic configuration diagram of FIG. The tandem-type full-color printer Z1 according to the present embodiment is an example in which the image forming apparatus according to the present invention is embodied. First, the overall configuration of the tandem-type full-color printer Z1 will be schematically described with reference to FIG.

In the main body of the tandem type full-color printer Z1, four image forming units 1a to 1d are arranged. The image forming units 1a to 1d are in charge of forming images of four different colors, and all have the same configuration.
For example, the image forming unit 1a includes a photosensitive drum 2a (an example of an image carrier), a transfer roller 3a, a developing device 4a, an exposing device 5a, a charging device 6a, a cleaning device 7a, and the like (the image forming unit 1b). For 1 to 1d, some of the reference numerals of these elements have been omitted. An endless transfer belt 11 is wound around the transfer rollers 3a to 3d of the image forming units 1a to 1d, the driving roller 8, the driven roller 9, and the auxiliary roller 10 disposed before and after the transfer rollers 3a to 3d. The transfer belt 11 is rotated in the direction of arrow Y1 by the drive of the drive roller 8. A registration roller 12 is provided on the upstream side of the transfer belt 11 and a fixing roller 13 is provided on the downstream side. A transfer paper cassette is provided at a lower portion of the main body, and a transfer paper discharge tray 15 is provided at an upper portion of the main body. Are provided respectively.

The image forming operation of the tandem type full-color printer Z1 having the above-described schematic configuration will be briefly described. First, the transfer paper conveyed from the transfer paper cassette 14a or 14b through the paper feed path 16 as indicated by an arrow Y2. Is sent out to the image forming unit 1a by the registration roller 12 at the image forming timing. The transfer paper sent from the registration roller 12 is transferred to an opposing portion (hereinafter, a transfer portion) between the photosensitive drum 2a of the image forming portion 1a and the transfer roller 3a with its leading end along the transfer belt 11. Inserted. The transfer sheet inserted into the transfer section of the image forming section 1a is first transferred with a toner image (for example, a black image) on the surface of the photosensitive drum 2a while being conveyed by the transfer belt 11. The transfer paper is transferred to the transfer belt 11.
Are sequentially transferred through the transfer units of the image forming units 1a to 1d, so that the toner images of four colors are sequentially superimposed and transferred.
A full-color image is formed. Each of the above image forming sections 1a to 1a
The transfer paper having passed through 1d is conveyed through the paper discharge path 17 as indicated by an arrow Y3 after the transfer image is fixed by the fixing roller 13, and is discharged onto the paper discharge tray 15.

Next, the characteristic portion of the tandem type full-color printer Z1 will be described with reference to FIG. FIG.
As shown in (enlarged schematic diagram of the transfer section of the image forming section 1a and the vicinity thereof on the upstream side), the transfer belt 11 is stretched horizontally between the image forming sections 1a to 1d, but the image on the most upstream side is formed. On the further upstream side (11a) of the forming part 1a, it is stretched so as to be inclined upward. The registration roller 12
Is disposed almost horizontally or slightly below the transfer section 20a of the image forming section 1a so as to horizontally transfer the transfer paper P. As a result, the transfer paper P sent from the registration roller 12 comes into contact with the upwardly inclined portion 11a of the transfer belt 11 at an angle θ (> 0 °). Since the upstream side of the transfer portion 20a of the transfer belt 11 is inclined upward as described above, the transfer roller P is brought into contact with the transfer belt 11 at an angle even though the registration roller is contacted at an angle. 12 can be installed at a lower position, and the degree of freedom of layout around the photosensitive drum 2a can be increased, for example, by lowering the installation position of the developing device 4a. Further, a paper feed guide for guiding the transfer paper P sent from the registration roller 12 is not provided as a dedicated member, and the bottom surface 4aa of the developing device 4a is an upper guide, and the upwardly inclined portion 11a of the transfer belt 11 is downward. Each is used as a side guide. Here, the upper guide formed by the bottom surface 4aa of the developing device 4a and the lower guide formed by the upwardly inclined portion 11a of the transfer belt 11 form a space opened toward the upstream side in the transfer paper transport direction. . Thus, the number of parts can be reduced by using the bottom surface 4aa of the developing device 4a as an upper guide and using the upwardly inclined portion 11a of the transfer belt 11 as a lower guide without providing a paper feed guide as a dedicated member. Thus, the assembly process can be simplified and costs can be reduced. The nip pressure between the photosensitive drum 2a and the transfer roller 3a is set to a pressure high enough to close the leading end of the transfer paper P sent out by the registration roller 12. Further, the transfer paper sending speed of the registration roller 12 is set slightly higher than the transfer paper transport speed in the transfer section 20a.

The transfer operation of the transfer paper P having the above-described configuration will be specifically described. The leading edge of the transfer paper P sent out in the horizontal direction by the registration roller 12 abuts on the upwardly inclined portion 11a of the transfer belt 11 at an angle θ (FIG. 1A). Here, the angle θ is 0 ° <θ.
It is desirable to set within the range of ≦ 30 °. If the angle θ exceeds 30 °, the tip is likely to bend, etc., which causes image defects and paper jams. Then, as the transfer paper P is further sent out by the registration rollers 12, the transfer paper P is sequentially brought into close contact with the transfer belt 11 from the leading end thereof, and is conveyed toward the transfer unit 20a. Here, since the transfer paper sending speed by the registration rollers 12 is set slightly higher than the transfer paper transport speed in the transfer unit 20a, when the leading end of the transfer paper P reaches the transfer unit 20a (FIG. 1 (b)). )) The transfer paper P is subjected to a force forcibly inserted into the transfer portion 20a by the registration roller 12. However, since the nip pressure of the transfer unit 20a is set to a pressure high enough to close the front end of the transfer paper P sent out by the registration roller 12, the front end of the transfer unit P is forced into the transfer unit 20a. The transfer is performed at an appropriate transfer start timing and transfer speed in the transfer unit 20a without being inserted into the transfer unit. At this time, the transport speed difference between the registration roller 12 and the transfer unit 20a causes the transfer paper P to bend between the bottom surface 4aa (upper guide) of the developing device 4a and the upwardly inclined portion 11a (lower guide) of the transfer belt 11. (FIG. 1 (c)). As described above, the transfer paper P is bent in the space formed between the bottom surface 4aa (upper guide) of the developing device 4a and the upwardly inclined portion 11a (lower guide) of the transfer belt 11, so that the resist Since the difference in transport speed between the roller 12 and the transfer unit 20a can be absorbed, the speed of the registration roller 12 does not always need to be strictly adjusted to the transport speed of the transfer unit 20a. It became possible to make it.

As described above, in the tandem type full color printer Z1 according to the present embodiment, the transfer belt 1
The registration roller 12 is set at a low position despite the fact that the transfer paper P is made to contact the transfer belt 11 at an angle by making the upstream side of the transfer portion 20a upwardly inclined. This makes it possible to increase the degree of freedom in layout around the photosensitive drum 2a, for example, by lowering the installation position of the developing device 4a. In addition, since a sheet feed guide as a dedicated member is not provided, and the bottom surface 4aa of the developing device 4a is used as an upper guide and the upwardly inclined portion 11a of the transfer belt 11 is used as a lower guide, the number of parts can be reduced, and assembly is possible. The process can be simplified and costs can be reduced. Further, the transfer paper P is bent in a space formed between the bottom surface 4aa (upper guide) of the developing device 4a and the upwardly inclined portion 11a (lower guide) of the transfer belt 11, so that the registration roller 12 is bent. And the transfer speed of the transfer unit 20a can be absorbed, so that the speed of the registration roller 12 does not always need to be strictly adjusted to the transfer speed of the transfer unit 20a. Became possible.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a tandem type image forming apparatus as exemplified in the above embodiment, unless images are formed at optimal timing in each image forming section, a finally formed image may have color misregistration. Would. Therefore, it is considered that the present invention can exert the most remarkable effect by applying to such a tandem type image forming apparatus, but it is needless to say that the present invention is applicable to an image forming apparatus having only one set of image forming apparatuses. Is also effective. Further, in the above embodiment, the registration roller 12 is configured to send out the transfer paper P horizontally. However, it goes without saying that the registration paper 12 may be sent out slightly diagonally downward or diagonally upward.

[0013]

As described above, according to the present invention, the image bearing member and the transfer roller pressed against the image bearing member, and the transfer paper on the transfer portion which is the facing portion between the image bearing member and the transfer roller are provided. An image forming apparatus comprising: a transfer belt to be passed therethrough; and a registration roller for inserting the transfer paper into the transfer portion while causing the transfer paper to pass along the transfer belt. The transfer roller on the upstream side of the transfer unit is disposed so as to be inclined upward with respect to the transfer direction on the downstream side, and the registration roller uses the upwardly inclined portion of the transfer belt as a lower guide to move the leading end of the transfer paper. Since the image forming apparatus is configured so as to contact the upwardly inclined portion of the transfer belt at an angle, the transfer paper is formed at an angle with respect to the transfer belt. This Despite so as to,
Since the registration roller can be installed at a lower position, the degree of freedom in layout around the image carrier can be increased, for example, by lowering the installation position of the developing device. In addition, by using the upwardly inclined portion of the transfer belt as the lower guide, the number of components can be reduced, and the assembly process can be simplified and the cost can be reduced.

Further, the transfer paper sending speed by the registration roller is set slightly higher than the transfer paper transport speed in the transfer section, and the bottom surface of the developing device provided on the upstream side of the image carrier is raised. If the upper guide and the lower guide formed by the upwardly inclined portion of the transfer belt form a space opened toward the upstream side in the transfer paper transport direction, the transfer paper can be transferred to the bottom surface (upper side) of the developing device. guide)
In the space formed between the transfer belt and the upwardly inclined portion (lower guide), the transfer paper can be bent to absorb the speed difference between the registration roller and the transfer unit. It is not necessary to strictly adjust the speed of the registration rollers, and it is possible to provide a margin in setting the speed of the registration roller. Further, in order to prevent the leading end of the transfer paper from being bent or the like, the contact angle θ of the leading end of the transfer paper to the upwardly inclined portion of the transfer belt is desirably set within the range of 0 ° <θ ≦ 30 °.

[Brief description of the drawings]

FIG. 1 is an enlarged schematic view of the most upstream transfer unit 20a and the vicinity of an upstream side thereof in a tandem type full color printer according to an embodiment of the present invention.

FIG. 2 is an overall schematic configuration diagram of a tandem-type full-color printer according to an embodiment of the present invention.

FIG. 3 is an enlarged schematic diagram of a transfer section 53 and an upstream vicinity thereof in an image forming apparatus according to the related art.

[Explanation of symbols]

 1a: Image forming unit 2a: Photoconductor drum (an example of an image carrier) 3a: Transfer roller 4a: Developing device 4aa: Developing device bottom surface 11: Transfer belt 11a: Upward inclined portion of transfer belt 12: Registration roller 20a: Transfer unit P… Transfer paper

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Akihiro Ozaki 1-2-2 Tamazo, Chuo-ku, Osaka Mita Industries Co., Ltd. F-term (reference) 2H032 AA15 BA11 BA19 BA23 3F049 DA03 EA14 LA04 LB03 3F102 AA02 AB01 DA08

Claims (3)

[Claims] An image bearing member, a transfer roller pressed against the image bearing member, a transfer belt for passing a transfer sheet through a transfer portion facing the image bearing member and the transfer roller, and the transfer belt. And a registration roller for inserting the transfer paper into the transfer section while causing the transfer paper to follow the transfer paper. The registration roller is disposed so that the conveying direction on the upstream side of the transfer unit is inclined upward, and the registration roller uses the upwardly inclined portion of the transfer belt as a lower guide and the leading end of the transfer paper to the upwardly inclined portion of the transfer belt. An image forming apparatus characterized in that the image forming apparatus is configured to be brought into contact at an angle. 2. A transfer paper sending speed by the registration roller is set to be slightly higher than a transfer paper transport speed in the transfer section, and a bottom surface of a developing device provided on the upstream side of the image carrier is set. 2. The image forming apparatus according to claim 1, wherein a space opened toward an upstream side in a transfer paper conveying direction is formed by the upper guide and the lower guide formed by an upwardly inclined portion of the transfer belt. . 3. The image forming apparatus according to claim 1, wherein an abutment angle θ of the leading end of the transfer sheet with respect to an upwardly inclined portion of the transfer belt is set within a range of 0 ° <θ ≦ 30 °.