JPH04149569A - Image forming device - Google Patents

Abstract

PURPOSE:To always keep a carrying belt moving speed constant without generating the sagging of a carrying belt and to obtain a color image without color slurring by specifying a position where the leading end of a sheet material is brought into contact with the carrying belt. CONSTITUTION:A following roller 15 and a pair of resist rollers 11 are arranged so that the leading end of the sheet material 9 which is ed by a paper feeding roller 10 and transferred from the upside by the pair of resist rollers 11 may be brought into contact with the carrying belt 12 within the extent of a part 20 shown by oblique lines. An area shown by the oblique lines part 20 is positioned on the upper of the roller 15 and also the area is positioned on the area of he belt 12 where it is brought into contact with the roller 15. Thus, by having such a constitution, the belt 12 can be prevented from sagging even in the case that the sheet material 9 has high rigidity since the roller 15 lies under the sheet material 9. Then, the belt 12 can be moved at a constant speed between respective image forming stations, so that the color image without color slurring can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention provides an image forming method for transferring an image formed at an image forming station onto a sheet material conveyed to the image forming station by a conveying means. The present invention relates to an image forming apparatus to obtain an image, and is particularly applicable to an electrophotographic color image forming apparatus that includes a plurality of image forming stations and forms color images.

[Conventional technology]

Conventionally, an image forming apparatus using an electrophotographic process includes an image forming station that forms a latent image on a photoreceptor drum as an image carrier and visualizes the latent image to obtain a visible image; The image forming station includes at least a conveying means for conveying a sheet material to a transfer position of a photoreceptor drum of the image forming station in order to transfer an image thereon, and a fixing means for fixing the image transferred onto the sheet material onto the sheet material. are doing.

On the other hand, the purpose of the conveyance means is to place and hold a sheet material on a belt-like conveyance member (conveyance belt) and convey it to a transfer position of an image carrier and further to a fixing means. The conveyor belt is supported and moved under tension by one driving roller and at least one driven roller.

If there are multiple image forming stations, the driving roller is located downstream of the final image forming station and before the fixing means, and at least one driven roller is located upstream of the first image forming station. It is located.

The conveyor belt is stretched between the driving roller and the driven roller with a constant force, and the conveyor belt moves from the first image forming station to the final image forming station at a constant speed without slacking between the rollers. Move to image forming station.

Furthermore, electrostatic adsorption force is usually used to hold the sheet material on the conveyor belt, and this is done as follows. The sheet material fed by the sheet material supply means (cassette) is transferred to the belt at the transfer section, where it is sent out from the registration rollers, contacts the conveyor belt, and moves together with the conveyor belt to the adsorption charger. . Therefore,
The surface of the conveyor belt is charged by the attraction charger, and the sheet material is electrostatically attracted thereon. In this way, the sheet material firmly held on the conveyor belt is conveyed to each image forming station, each color image is transferred thereto, and then the transferred image is fixed in the fixing means to obtain a color image. I can do it.

[Problem that the invention is trying to solve]

However, in the conventional example described above, if a configuration is adopted in which the sheet material is sent out parallel to the conveyor belt from the registration rollers and brought into contact with it as shown in FIG. As can be seen from the bending of the material, the force applied by the sheet material to the conveyor belt in parallel to the direction of movement of the conveyor belt causes large fluctuations in the moving speed of the conveyor belt.

Therefore, as shown in Figure 3, by placing the sheet material in contact with the conveyor belt from above at an angle,
It is conceivable to reduce the force component applied to the conveyor belt parallel to the direction of movement of the conveyor belt.

However, even when the sheet material is brought into contact with the conveyor belt from above as described above,
When a highly rigid sheet material such as cardboard is used as the sheet material, when the sheet material comes into contact with the conveyor belt, as shown in Figure 4, due to the strong rigidity of the sheet material, the leading edge of the sheet material touches the conveyor belt. This causes the conveyor belt to become slack between the drive roller and the driven roller.

Normally, conveyor belts are made of fairly thin members for reasons such as transfer efficiency, and both ends of the conveyor belt move without being supported by anything, so the force that resists the downward force is extremely large. It is weak, and even the weak force of contact between the sheet materials as described above can cause loosening. This cannot be prevented simply by increasing the tension on the conveyor belt.

Because of this slack in the conveyor belt, part of the work of the drive roller that should be used to move the conveyor belt is used to eliminate the slack in the conveyor belt, and between the drive roller and the driven roller. Fluctuations occur in the moving speed of the conveyor belt. As described above, since the sheet material is held by the conveyor belt, if the moving speed of the conveyor belt fluctuates, the time it takes for the sheet material to reach the transfer position of each image forming station also fluctuates.

Assuming that the speed of the conveyor belt that conveys the sheet material to each image forming station is constant, the arrival time of the sheet material to the transfer position of each image forming station is predicted in advance by calculation, and each Since image formation is started at the image forming station, if the arrival time fluctuates, a positional shift of image transfer to the sheet material will occur between the image forming stations by the amount of the fluctuation. This appears as color misregistration of each color image on the sheet material, leading to deterioration of the image quality as a color image.

In addition, when forming images by continuously feeding sheet materials, while the image of the first sheet material is still being transferred at the downstream image forming station, the next sheet material is fed out from the registration rollers. and comes into contact with the conveyor belt. Therefore, the resulting loosening of the conveyor belt results in rapid fluctuations in the moving speed of the conveyor belt and vibrations of the conveyor belt, which directly affects the sheet material on which the image is being transferred at the image forming station. The image on this sheet material has already become a color-shifted image due to the loosening of the conveyor belt due to its own causes, and since it is affected by the above, the image is further deteriorated.

[Means to solve the problem]

The present invention was made in view of the above-mentioned conventional problems.
The purpose is to provide an image forming apparatus in which the conveyor belt is prevented from loosening and the moving speed of the conveyor belt remains unchanged.

That is, the present invention includes an image bearing member, a means for forming an image on the image bearing member, and a means for conveying the sheet material onto which the image formed on the image bearing member is transferred to a transfer position of the image bearing member. An image forming apparatus comprising: a conveying means having a belt that supports a sheet material and moves endlessly stretched between a plurality of rollers; The position where the leading edge of the sheet material sent out from the means comes into contact with the belt is in a region where the roller and the heald are in contact with each other, or in a region adjacent to this region.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments thereof with reference to the accompanying drawings.

In this embodiment described below, the image forming apparatus according to the present invention is an electrophotographic laser beam color printer (
Hereinafter referred to as "rLBP device". ) is embodied in

Referring to FIG. 1, there is shown a schematic cross-sectional configuration diagram of an LBP device as an image forming device according to the present invention, and this LBP device has a plurality of image forming stations arranged side by side,
A subtractive color mixing method uses modulated laser light as a light source to form toner images in four colors, for example, magenta, cyan, yellow, and black, using an electrophotographic process, and transfers each color image one after another onto a sheet material. This is to obtain a full-color image using the .

The configuration and operation mode of this LBP device 1 will be further explained with reference to FIG. 1.

In this embodiment, the LBP apparatus 1 has four image forming stations M, C, Y, and B, and the image forming stations M,
A conveying means 18 equipped with a conveying belt 12 is disposed below C, Y, and H to convey the sheet material, and at the outlet of the conveying means, the image on the sheet material is heated onto the sheet material. A fixing means 16 for fixing is arranged.

Here, in the conveying means 18, the conveying belt 12 is supported and moved by a driving roller 13 and driven rollers 14 and 15. At this time, by moving the roller axis position of the driven roller 14, the conveyor belt 12 is stretched tightly between the drive roller 13 and the driven roller 15, and moves endlessly at a constant speed. In this example, a conveyor belt made of polyurethane resin and having a thickness of 100 μm was used as the belt material.

Each of the image forming stations M, CSY, and B includes a means for forming an image 1, such as an image carrier rotating at a constant speed in the direction of the arrow shown in the figure, that is, an electrophotographic photosensitive drum LM1 ICS IY in this embodiment.

1B, charger 5M, 5C15Y, 5B, developer 2M.

2C12Y, 2B, transfer charger 3M, 3C13Y, 3B
and cleaner 4M, 4. It has C, 4, Y, and 4B respectively.

Next, the formation of a color image with the color LBP device having the above configuration will be described.

A sheet material 9 in a cassette 8, which is a transfer material supply means, is fed by a paper feed roller 1O, fed from above onto a conveyor belt 12 by a pair of registration rollers l/, and moves together with the conveyor belt 12. Thereafter, the sheet material 9 is attracted and held on the conveyor belt 12 by the attraction charger 19 and is conveyed.

On the other hand, after forming a latent image of the magenta component color of the image information on the photosensitive drum 1M by a known electrophotographic method using the charging section 5M and the exposing section 6M of the first image forming station M, the developing section 2M The latent image is made into a visible image by a developer containing magenta toner, and the made visible magenta toner image is transferred onto the sheet material 9 conveyed by the conveyor belt 12.

While this magenta toner image is being transferred onto the sheet material 9, a latent image of the cyan component color of the image information is formed on the photosensitive drum IC at the second image forming station C, as in the case of the magenta toner image. is formed, and then a cyan toner image is obtained using cyan toner in the developing section 2C, and the sheet material 9 on which the transfer of the magenta toner image has been completed at the first image forming station M is carried into the second image forming station C. Then, the magenta toner image is transferred to a predetermined position on the sales sheet material 9, and this cyan toner image is transferred.

Image formation was performed in the same manner for yellow and black colors, and when the four-color toner images were superimposed on the sheet material 9, the sheet material 9 was placed on the other end side of the conveyor belt means. The image is conveyed to the fixing section 16 and fixed there, and a multicolor (full color) image is obtained on the sheet material 9.

Each photosensitive drum IM, ICl/￥ after transfer has been completed
, IB are cleaned of residual toner remaining thereon by cleaning means 4M, 4C, 4Y, and 4B in preparation for the next latent image formation to be performed subsequently.

In the LBP apparatus as described above, in this embodiment, the paper is fed by the paper feed roller 10, and the registration roller pair l
/ so that the leading edge of the sheet material 9 sent out from above comes into contact with the conveyor bell i.12 within the shaded area 20.
A driven roller 15 and a registration roller pair l/ are arranged. The area indicated by the shaded area 20 is the area where the driven roller 15
This is the area on the conveyor belt 12 that is located above and in contact with the driven roller 15.

By arranging the position where the tip of the sheet material 9 contacts the conveyor belt 12 in the above-mentioned shaded area 20,
Even if the sheet material 9 is made of a highly rigid material such as cardboard, the conveyor belt 12 may become slack as shown in FIG. There's nothing to do. Therefore, the conveyor belt 12 can move between each image forming station at a constant speed, and a color image without color shift can be obtained.

Next, another embodiment of the present invention will be described with reference to FIG. In this embodiment, the overall configuration of the LBP device is the same as that of the previous embodiment, so a description thereof will be omitted and only the main parts will be described.

In this embodiment, the driven roller 15 and Registration roller pair/
are placed. This shaded area 21 is an area adjacent to the shaded area 20 described above. In the area indicated by the diagonal line 21, the conveyor belt 12 is out of contact with the driven roller 15, but because it is located very close to the driven roller 15, even if the conveyor belt is pushed downward by a highly rigid sheet material, Does not cause slack.

In the image forming apparatus of this embodiment, the distance from the contact point a between the driven roller 15 and the conveyor belt 12 to the transfer position of the first image forming station is f=120 mm, and the sheet material is 205 g/m''. When paper was used, the range in which the shaded area 21 did not get pinched or loosened was about 1/51 (24 mm) from the contact point a.
This value is appropriately set depending on the belt thickness, material, and usable sheet material.

Therefore, by making sure that the leading edge of the sheet material 9 is always in contact with the conveyor belt 12 at a distance of about 0 to 24 mm from the driven roller 15, the conveyor belt 12 moves between each image forming station at a constant speed. It is possible to obtain a color image without color shift.

In the two embodiments described above, an adsorption charger is used to adsorb and hold the sheet material on the conveyor belt before the sheet material reaches the first image forming station, but the present invention is not limited to this. It goes without saying that the present invention can also be applied to an image forming apparatus that has a configuration in which the sheet material is attracted to the belt at the same time as the transfer is performed in the first image forming station.

Moreover, although the case has been described as an example in which a plurality of image forming stations are provided, the image forming apparatus may also be an image forming apparatus that supplies a sheet material to one image carrier using a conveyor belt.

〔Effect of the invention〕

As explained above, according to the present invention, by specifying the position where the leading edge of the sheet material contacts the conveyor belt,
Even when a highly rigid sheet material such as cardboard is used, the conveyor belt does not slacken, and the moving speed of the conveyor belt can always be kept constant, resulting in color images without color misalignment. can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view schematically showing a first embodiment of an image forming apparatus according to the present invention. FIG. 2 is an explanatory diagram showing the state when the sheet material is sent out parallel to the conveyor belt. FIG. 3 is an explanatory view showing the state when the sheet material is fed out from above with respect to the conveyor belt. FIG. 4 is an explanatory diagram showing how the conveyor belt becomes slack due to the highly rigid sheet material. FIG. 5 is a sectional view schematically showing a second embodiment of the image forming apparatus according to the present invention. LM, IC, IY, IB... Image carriers 2 to 1.2C, 2Y, 2B... Developing device 9... Sheet material l/... Registration roller pair 12... Conveyor belt 13... Drive roller 14.15...driven roller

Claims (6)

[Claims] (1) An image carrier, a means for forming an image on the image carrier, and a means for transporting the sheet material onto which the image formed on the image carrier is transferred to a transfer position of the image carrier. an image forming apparatus comprising: a conveying means having a belt that carries the sheet material and moves endlessly while being stretched between a plurality of rollers; An image forming apparatus characterized in that the position where the leading end of the sheet material that is sent out comes into contact with the belt is in an area where the roller and the belt are in contact, or an area adjacent to this area. (2) The image forming apparatus according to claim 1, wherein the means for feeding out the sheet material is a pair of rollers. (3) The direction in which the belt carries the sheet material and moves toward the transfer position is approximately horizontal, and with respect to this direction of movement, there is a gap between the contact point of the belt and the roller and the transfer position. 3. The image forming apparatus according to claim 1, wherein the adjacent area is within a range of about 1/5 from the contact point, where 1 is a distance. (4) The image forming apparatus according to claim 3, wherein the belt and the roller are not in contact with the adjacent area. (5) In the image forming apparatus, a plurality of the image carriers are arranged in parallel in the conveying direction of the sheet material to constitute a plurality of image forming stations, and the transfer position is the image bearing member on the most upstream side in the conveying direction of the sheet material. Claims 1-
4. The image forming apparatus according to 4. (6) Images of different colors are formed at the plurality of image forming stations, and as the sheet material sequentially passes through the transfer position of each image carrier, each color image is superimposed and transferred onto the sheet material, resulting in a multicolor image. The image forming apparatus according to claim 5, wherein: is formed.