JPH04277763A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent the generation of irregularities in an image caused by a lower guiding plate when the image is formed on the lower surface side of a transfer sheet at the upper carriage. CONSTITUTION:The lower guiding plate 16 is constituted so as to have an inclined surface 16a, so that the nonimage parts of both end parts of the transfer sheet P is supported, and the inclined surface 16a has an angle that the inclined surface 16a does not contact with the transfer sheet P even if it is bent downward. On the other hand, the central part of the lower guiding plate 16 has a concave shape, with a part of its inclined surface 16a left. Therefore, the transfer sheet P does not come into contact with the lower guiding plate, but the irregularities in an unfixed image is prevented.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention transfers a toner image formed on an image carrier to the lower surface of a transfer sheet in a transfer section, and then conveys the transfer sheet to a fixing device to fix the toner image. The present invention relates to an image forming apparatus that forms an image.

0002

2. Description of the Related Art In image forming apparatuses such as copying machines and printers, there is a so-called top conveying apparatus in which an image forming means including a photoreceptor is disposed on the lower side of a transfer sheet. In such image forming devices, the image is formed on the bottom side of the transfer paper, so if you are using transfer paper that is weak in stiffness, or if you are using transfer paper that has become weak due to high humidity, it is necessary to During fixing, there is a problem in that the unfixed toner image is disturbed due to the transfer paper coming into contact with the lower conveyance guide plate.

In order to prevent this problem, conventionally, as shown in FIG. 6, a device has been adopted in which a fan 30 is provided to suck the transfer paper P upward and guide it to the fixing nip 15a of the fixing device. ing. However, this device requires a fan to suck the transfer paper, resulting in a significant increase in cost.

Furthermore, as shown in FIG. 7, there is also an apparatus in which a spur 31 is provided on the lower fixing guide side to scoop up the hanging transfer paper P and guide it to the nip portion 15a. However, in this case, there is a problem in that spur marks remain on the image surface of the transfer paper.

[0005]

[Problems to be Solved by the Invention] The present invention solves the above-mentioned problems in the prior art, uses a simple structure that does not require any cost, and does not disturb the unfixed toner image transferred to the transfer paper. It is an object of the present invention to provide an image forming device that does not leave unnecessary traces on the image surface of paper.

[0006]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the invention according to claim 1 provides a method in which a toner image formed on an image carrier is transferred to the lower surface side of a transfer sheet in a transfer section. In an image forming apparatus that conveys a transfer paper to a fixing device and fixes a toner image to form an image, there is provided at both ends in the width direction perpendicular to the conveying direction between the transfer section and the fixing device. The invention according to claim 2 is characterized in that a guide member is provided to support a portion outside the area of the toner image, and in addition to the above, the guide member is continuous in the width direction and descends from both ends toward the center. The invention of claim 3 is characterized in that the slope angle of the slope is such that when the transfer paper is supported, the toner image surface does not come into contact with the transfer paper due to the downward deflection of the transfer paper. In addition to the feature of the invention in item 1, the inclined surface is characterized in that a central portion in the width direction is a recessed portion.

[0007]

[Operation] According to the present invention, as configured as described above, in the invention of claim 1, the guide member supports both ends of the transfer paper in the width direction and outside the area of the toner image. The toned image is not disturbed by the guide member. Further, since the guide member only supports the transfer paper and guides its conveyance, it does not leave any traces on the transfer paper, and furthermore, its structure is simple.

According to the invention of claim 2 or 3, by forming the guide member with an inclined angle or a recessed portion so as not to touch the image plane, it is possible to make the guide member continuous and integral in the width direction. This further simplifies the configuration.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a schematic structure of a laser printer which is an example of an image forming apparatus to which the present invention can be applied. Around the belt-shaped photoreceptor 1, there are chargers 2 that uniformly charge the photoreceptor in the rotation direction indicated by the arrow.
, an exposure unit 4 where the reflected light of the original image is formed by an optical system 3, a developing device 5 which develops an electrostatic latent image formed on the photoreceptor 1 by exposure with toner, and a registration roller 6 at the same time. A transfer charger 8 that transfers a toner image onto the transferred transfer paper at a transfer section 7, a cleaning device 9 that removes toner remaining on the photosensitive drum 1 after transfer, and the like are provided.

Reference numerals 10 and 11 are paper feed cassettes, and the transfer paper is transferred to the paper feed cassette 10 by a paper feed device 12 or 13.
Or it is fed from 11 to registration roller 6. Further, reference numeral 14 is a manual paper feed tray.

The transfer paper on which the toner image has been transferred is further conveyed by the registration rollers 6, reaches the fixing device 15, and passes through a nip portion 15a formed by the fixing roller 15-1 and the pressure roller 15-2. At this time, the unfixed toner image thereon is heated and fixed. A lower guide plate 16 as a guide member according to the present invention is provided between the transfer section 7 and the nip section 15a of the fixing device 15.

The transfer paper that has passed through the fixing device 15 is sent out by a pair of paper ejection rollers 17, and is ejected in the direction of arrows A, B, or C by switching the switching claws 18 and 19 to paper ejection trays 20 and 21, respectively. Alternatively, the sheet is ejected onto the manual paper feed table 14, or is conveyed again to the registration roller pair 6 by the feed roller pair 22, and double-sided copying is performed.

FIGS. 2 and 3 show an example of the lower guide plate 16. FIG. The lower guide plate 16 is provided between the transfer section 7 and the nip section 15a of the fixing device 15, and covers the portion of the transfer paper P other than the area where the toner image is located inside the width of the transfer paper P by a certain range. For support, it is provided with inclined surfaces 16a that descend from both ends toward the center as shown in the figure.

The angle of inclination of the inclined surface 16a is set at such an angle that even when the transfer paper P is bent downward, the inclined surface 16a does not touch the image surface thereof. In this case, the distance between the transfer section 7 and the nip section 15a is usually short, and the transfer paper P is
Since it is suction-supported by the photoreceptor 1, it will not bend downward as much if both ends are supported.

FIGS. 4 and 5 show other examples of the lower guide plate. The lower guide plate 16' has a support surface for the transfer paper P having a structure similar to that shown in FIG. 2, and has a concave central portion. The recessed portion 16'b has a depth such that it does not come into contact with the transfer paper P even if it bends downward.

[0016] Even when such a lower guide plate is provided, it is possible to provide a conveyance assisting mechanism that sucks the transfer paper P upward. In this way, the transfer paper P can be more effectively guided to the nip portion 15a of the fixing device 15.

[0017]

As described above, according to the present invention, in the invention of claim 1, the guide member supports both ends of the transfer paper in the width direction outside the area where the toner image is present, and transports the transfer paper. Since it is guided, it is possible to prevent image disturbance and generation of traces on the transfer paper, and also to simplify the structure.

According to the second or third aspect of the present invention, since the guide member has an inclination angle or a concave portion that is continuous in the width direction, it can be manufactured integrally and the structure thereof can be simplified.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a laser printer according to an embodiment.

FIG. 2 is a perspective view of a lower guide plate portion of the embodiment.

FIG. 3 is a side view of the lower guide plate portion.

FIG. 4 is a perspective view of a lower guide plate portion of another embodiment.

FIG. 5 is a side view of the lower guide plate portion.

FIG. 6 is a side view of a conventional conveyance system when a suction fan is provided.

FIG. 7 is a side view of a conventional conveyance system when a spur is provided.

[Explanation of symbols] 1 Photoreceptor (image carrier) 7 Transfer section 15 Fixing device 16, 16' Lower guide plate (guide member) 16a
Inclined surface 16'b recess

Claims (3)

[Claims] 1. An image forming apparatus that transfers a toner image formed on an image carrier onto the lower surface of a transfer sheet in a transfer section, and then conveys the transfer sheet to a fixing device to fix the toner image to form an image. In the image forming apparatus, a guide member is provided between the transfer section and the fixing device to support a portion outside the toner image area at both ends in the width direction perpendicular to the conveyance direction. Device. 2. The guide member includes an inclined surface that is continuous in the width direction and descends from both ends toward the center, and the inclination angle of the inclined surface is determined by the downward deflection of the transfer paper when the transfer paper is supported. The image forming apparatus according to claim 1, wherein the angle is such that the toner image surfaces do not come into contact with each other. 3. The image forming apparatus according to claim 2, wherein a central portion of the inclined surface in the width direction is a recessed portion.