JPH01214569A - Image formation device - Google Patents

Abstract

PURPOSE:To prevent the occurrence of a sheet fold, a wrinkle, a disturbed image and the like by applying the constitution wherein the height of a carriage route at a central part in the widthwise direction of the route between a transfer means and a fixing means is set at a position relatively lower than the height of the route near both ends thereof. CONSTITUTION:An electrostatic latent image formed on a sensitive drum 1 (image carrier) is transferred to transfer paper P (recording paper) via a transfer electrifier 2 (transfer means) and carried in a center-well form in a widthwise direction along a carriage route 3 comprising a transfer belt 4, a transfer rib 5 forming the carriage route of the same height as the belt 4, a transfer rib 6 located higher than the transfer belt 4 and the transfer rib 5 over the entire length of the carriage route. The leading end of the transfer paper P ingresses into a fixing device 8 (fixing means) along a fixing inlet guide 7 and an image on the paper P is fixed therein. According to the aforesaid construction, the transfer paper P is made into a center-well condition in a widthwise direction due to the own weight thereof and the rigidity of the paper P is increased in a carriage direction, thereby enabling stable carriage along the carriage route. The contact pressure of the paper P at the fixing inlet guide 7 increases and the neighborhood near the leading end of the paper P is properly aligned with the guide 7.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an image forming apparatus that conveys a recording sheet onto which an image has been transferred by electrophotography to a fixing device and fixes the image.

(Prior Art) Conventionally, in an electrophotographic image forming apparatus, an electrostatic latent image formed on a photosensitive drum is transferred onto a transfer paper by a transfer means, and the transfer paper is conveyed on a flat conveyance path to a fixing entrance. By guiding it along the guide to the fuser nip,
The entire leading edge of the transfer paper is made to enter the nip at the same time.

However, transfer paper weighing less than about 100g has low rigidity, so it may float up from the conveyance path due to the wind flow to exhaust heat inside the machine or the curl of the paper, and the paper may not be properly guided by the fixing entrance guide. will proceed. Therefore, the degree to which the leading edge of the transfer paper floats on the fuser logite is different on the left and right sides, and if it enters the nip in this state, the leading edge on the side along the fuser entrance guide will enter the nip smoothly, but the side that is raised will enter the nip smoothly. The leading edge of the paper may come into contact with the upper surface of the inlet of the fixing device, causing paper folds, wrinkles, and image distortion. This tendency becomes even more pronounced as the width of the transfer paper increases, as the degree of floating of the leading edge tends to differ between the left and right sides.

Therefore, in conventional electrophotographic image forming apparatuses, an air suction or the like is used in the conveyance path to attract and convey the transfer paper to the conveyance path, and the transfer paper is caused to enter the nip of the fixing device along the fixing device logite.

(Problems to be Solved by the Invention) However, in such a conventional example, a device such as an air suction must be incorporated into the conveyance path, which causes a problem that the device becomes large and complicated. Another problem is that even if a device such as air suction is used, the leading edge of the recording paper may become unstable at the part where the suction effect of the fusing population guide etc. no longer works, and may not enter the nip of the fusing device along the fusing entrance guide. There were also points.

Therefore, the present invention has been made to solve the above-mentioned problems of the conventional example, and its purpose is to move the recording paper along the conveyance path without attracting the recording paper to the conveyance path by air suction or the like. The leading edge of the recording paper is conveyed along the fixing entrance guide and enters the fixing means.Also, when using a device such as air suction, the leading edge of the recording paper is more securely aligned with the fuser logite. It is an object of the present invention to provide an image forming apparatus that does not cause paper folds, wrinkles, image disturbances, etc. when the paper enters a fixing means.

(Means for Solving the Problems) In order to achieve the above object, in the present invention, a latent image formed on an image carrier is transferred onto recording paper by a transfer means to form an image, In an image forming apparatus in which the image is fixed on the recording paper by a fixing means through a conveyance path, the height of the conveyance path at the center with respect to the width direction of the conveyance path between the transfer means and the fixing means is set at both ends. It is configured by being set at a lower position than the height of the nearby conveyance path.

(Function) In the present invention having the above configuration, the height of the conveyance path at the center in the width direction of the conveyance path between the transfer means and the fixing means is set to a position lower than the height of the conveyance path near both ends. By setting the recording paper to , the recording paper is placed in an intermediate state in the width direction due to its own weight and its rigidity in the transport direction is increased, so that the recording paper is transported in a stable state along the transport path. As a result, the pressure with which the recording paper comes in contact with the fuser logite increases, and the recording paper enters the fixing means with the leading edge of the recording paper reliably following the fixing entrance guide, so there is no wrinkles, paper folds, or image disturbances. This allows images to be obtained.

(Example) The present invention will be explained below based on the illustrated example. 8th
The figure is a schematic configuration diagram of an image forming apparatus to which the present invention is applied. In the figure, 1 is a photosensitive drum as an image carrier, and the rotating photosensitive drum 1 is uniformly charged by a primary charger 50. is applied, and an electrostatic latent image is formed by light irradiation from a light source 51. This electrostatic latent image is developed with toner in a developing device 52, and the toner image is transferred onto transfer paper P, which is a recording paper, by a transfer charger 2, which serves as a transfer means, to form an image. That is, as shown in FIG. 1, the electrostatic latent image formed on the photosensitive drum 1 by the developing device 52 is transferred by the transfer charger 2 onto the transfer paper 3, which is conveyed with reference to the center of the image. The transfer paper P is separated from the photosensitive drum 1 by a known separating means, and separated from the conveyor belt 4.
The conveyance path 3 is made up of a conveyance rib 5 that forms a conveyance path with the same height as the conveyance path, and a conveyance rib 6 that is located at a higher position than the conveyance belt 4 and the conveyance rib 5 over the entire length of the conveyance path. The tip is transported by the fixing entrance guide l”
7 and enters a fixing device 8 as a fixing means. The image on the transfer paper P is then fixed by a fixing device 8.

Figure 2 is a view of the transport path in Figure 1 viewed from the fixing unit 8 side (arrow A), and Figure 3 is a view perpendicular to the transport direction (arrow B).
It is a figure of the conveyance path seen from. The conveyor belt 4 and the conveyor ribs 5 forming the conveyor path near the center in the width direction of the conveyor path 3 are at a lower position than the conveyor ribs 6 forming the conveyor path near both sides, and the transfer paper P conveyed along the conveyor path 3 hits the fixing entrance guide 7 with its middle opening in the width direction.

FIG. 4 is a diagram showing that the rigidity of the transfer paper P at the middle edge increases in the conveyance direction. In the plane zY perpendicular to the X axis, paper with a mid-edge has stronger rigidity in two directions relative to the X direction than flat paper. Therefore, the leading edge of the transfer paper P is conveyed without floating up from the conveyance path 3 and hits the lower part of the input logite 7. FIG. 5 is a diagram showing a state in which the leading edge of the transfer paper P at the middle edge enters the fixing device 8 along the fixing device logite 7 which is inclined so as to be higher than the conveying path on the fixing device 8 side. , Figure 6 shows C in Figure 5.
7 is a view taken along arrow D in FIG. 5.

With the above configuration, the state in which the transfer paper P enters the fixing device 8 is stable, and even curly transfer paper (especially common in double-sided or multiple copying) can be conveyed without jamming, wrinkles, etc. It's coming. That is, according to the experiments conducted by the present inventors, in the case of a device that conveys the maximum B4 size by vertical feeding, the height difference of the conveying rib 6 with respect to the conveying belt 4 and the conveying rib 5 is in the range of 1 to 6 mm (particularly 2 to 3 mm). Optimum), good conveyance results can be obtained for thick paper (approximately 128 g/rri'') and thin paper (58 g/m2), from the maximum B4 size transfer paper to the minimum business card size transfer paper. This is approximately 0.4 to 2.0 mm with respect to the width of the conveyance path.
The difference in height was 3%, and a tendency for a difference in width was obtained for an apparatus in which the maximum original size was larger than B4 size.

The second to eighth embodiments of the present invention will be described below as other embodiments that can be applied to the conveyance path shown in the first embodiment. These embodiments differ from the first embodiment only in the conveyance path 3 consisting of a conveyance belt 4, conveyance ribs 5, and conveyance ribs 6, and the other structures and functions are the same as in the first embodiment.

FIG. 9 (a), (b), (c) showing the second embodiment
), the transport heald 9 forming the transport path at the center in the width direction of the transport path is located at a higher position on the transfer side than the transport ribs 10 forming the transport path near both sides, and on the fixing unit 8 side is higher than the transport ribs 10. It's in a low position. That is, the reason why the conveyance belt 9 is located at a higher position than the conveyance rib 10 on the transfer unit side is to ensure that small transfer paper such as a business card or postcard is placed on the conveyance heald 9 and conveyed to the fixing device. On the fuser 8 side, the transfer paper is not placed on the conveyor belt 9 and no conveyance force is transmitted to it, but the leading edge of the transfer paper enters the nip of the fixer 8 and is conveyed. The transfer paper P, which has a wide width and weighs up to about 100 g, is conveyed along the conveyance path, and has a convex center on the transfer unit side, gradually becomes flat, and becomes a center edge on the fixing device 8 side, producing the same effect as the first embodiment. is obtained.

FIGS. 10(a), (b), and (c) show a third embodiment of the present invention, and in this embodiment, a conveyor belt 11 and a conveyor rib forming a central conveyor path in the width direction of the conveyor path are shown. 12 is located at a lower position than the conveyance ribs 13 forming the conveyance path near both ends on the transfer side, and is at the same height as the conveyance ribs 13 on the fixing device 8 side. Therefore, the transfer paper has a middle edge in the width direction on the transfer unit side, and becomes flat as it is conveyed to the fixing device 8 side. Therefore, the rigidity of the transfer paper P becomes high, so that it is conveyed along the conveyance path.

FIGS. 11(a), (b), and (c) show a fourth embodiment of the present invention. In this embodiment, the conveyor belt 14 forming the central conveyance path in the width direction of the conveyance path The ribs 15 are at the same height as the conveyance ribs 16 forming the conveyance path near both ends on the transfer side, and are at a lower position than the conveyance ribs 16 on the fixing device 8 side. Therefore, the transfer paper is flat on the transfer unit side, but as it is transported to the fixing device 8 side, it becomes mid-edge and becomes more rigid, and is transported along the transport path, which is the same as in the first embodiment. Get the effect.

FIGS. 12(a), (b), and (c) show a fifth embodiment of the present invention. In this embodiment, the conveyance path is such that the conveyance ribs 19 forming the conveyance path at both ends in the width direction are connected to the transfer portion. The conveyor belt 17 is located at approximately the same height as the conveyor belt 17 on the side, and the conveyor belt 17 is set at a lower position than the conveyor ribs 19 on the fixing device side. The conveyor rib 18 is located between the conveyor belt 17 and the conveyor rib 19, which form the central part in the width direction, and is set lower than the conveyor belt 17 on the transfer section side and at approximately the same height as the conveyor belt 17 on the fixing unit 8 side. ing. The conveyance rib 18 is configured by the width of the postcard on the conveyance path, and is located at a lower position than the conveyance belt 17 on the transfer section side.
The postcard is placed on the conveyor belt 17 and conveyed by the conveying force. As the conveyance rib 18 and the conveyance belt 17 get closer to the fuser 8 side, the difference in height between the conveyor rib 18 and the conveyor belt 17 decreases, making it difficult for the conveyance force to be transmitted. transported. Transfer paper, which is wider than a postcard, rests flat on the transfer belt 17 and transport ribs 19 on the transfer unit side, but as it advances toward the fixing device, it rests on the transport bell 17 and transport ribs 18 and 19 and becomes concave. , the same effects as in the first embodiment can be obtained.

FIGS. 13(a) and 13(b) show a sixth embodiment of the present invention. In this embodiment, the conveyance path includes a conveyor belt 20 forming the central portion in the width direction and a conveyor belt 20 extending toward both ends. The conveyor ribs 21 are configured to have a concave arc shape in the width direction due to the conveying ribs 21 whose height increases. Therefore, the transfer paper is conveyed along the conveyance path in the shape of a concave circular arc, and the same effect as in the first embodiment is obtained.

FIGS. 14(a) and 14(b) show a seventh embodiment of the present invention, and in this embodiment, the conveyance path is installed at an angle so that the center part in the width direction is lower than both ends. It is composed of two conveyor belts 22°22. Therefore, the transfer paper is conveyed on the conveyor belts 22, 22 in a V-shaped concave state, and the same effect as in the first embodiment is obtained.

15(a), (b), and (c) show an eighth embodiment of the present invention. In this embodiment, the conveyance ribs 27 forming the conveyance path near both ends in the width direction of the conveyance path and the Provided at a slightly lower position between the conveyor ribs 27,
Suction plate 28 that has the function of attracting the transfer paper to the conveyance path
are the conveyor belt 23 and the conveyor rib 2 forming the conveyance path near the center.
5, the suction sheet metal 24 between the conveyor ribs 25 and the conveyor ribs 27
The transfer paper is attracted to the suction plate metal 24, 26, and 28 and is conveyed in a concave state along the shape of the conveyance path in the first embodiment. The same effect as the example is obtained. Here, the above-mentioned suction sheet metal is a sheet metal placed in a grounded state on the conveyance path, and has the function of attracting the sheet metal to the sheet metal by the electric charge of the transfer paper after transfer, as is well known.

In the first to eighth embodiments described above, the conveyance path is composed of a conveyance belt and conveyance ribs, but even if the conveyance path is entirely constituted by conveyance ribs or is entirely constituted by a conveyance belt, the shape of the conveyance path may vary depending on the width. It is acceptable as long as it is concave in the direction.

Further, although a suction plate is used in the conveyance path only in the eighth embodiment, an air suction device may be used instead of the suction plate. It goes without saying that if the present invention is similarly applied to other embodiments, the effects can be significantly increased.

(Effects of the Invention) As explained above, according to the present invention, by setting the height of the conveyance path near the center in the width direction of the conveyance path to a lower position than the height of the conveyance path near both ends. , the recording paper is transported in a concave state in the width direction, improving rigidity in the transport direction, and the copy paper is transported in a stable state along the transport path, reducing wrinkles, paper folds, and image distortion. It is possible to obtain good images without Furthermore, since it is possible not to use air suction or the like, there is also the effect that the device can be made smaller and simpler.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing the main parts of the first embodiment of the present invention;
The figure is a view in the direction of the arrow in FIG. 1, FIG. 3 is a configuration diagram seen from direction B in FIG. 1, FIG. 4 is an explanatory diagram of the transfer paper in the same embodiment, and FIG. 5 is in the same embodiment. A perspective view showing the conveyance state of the transfer paper, FIG. 6 is a view taken in the C direction of FIG. 5, and FIG.
8 is a schematic configuration diagram of an image forming apparatus to which the present invention is applied, and FIGS. 9(a), (b), (
c) is a configuration diagram showing the conveyance path in the second embodiment of the present invention, a front view on the transfer side, a front view on the fixing side, and FIG. 10(a)
, (b), and (c) are block diagrams showing the conveyance path in the third embodiment of the present invention, a front view of the transfer side, and a front view of the fixing side. A configuration diagram showing a conveyance path in the fourth embodiment of the present invention, a front view on the transfer side, a front view on the fixing side, FIGS. 12(a) and 12(b),
(c) is a configuration diagram showing a conveyance path in a fifth embodiment of the present invention, and a front view on the transfer side. A front view of the fixing side, FIGS. 13(a) and 13(b) are a configuration diagram showing a conveyance path in the sixth embodiment of the present invention, and a front view of the transfer and fixing side, FIGS. 14(a) and (b) are a perspective view, a front view, and a
), (b), and (c) are a perspective view, a configuration diagram, and a plan view showing a conveyance path in an eighth embodiment of the present invention. Explanation of symbols 1... Photosensitive drum (image carrier) 2... Transfer charger (transfer means) 3... Conveyance path 8... Fixing device (fixing means) P... Transfer paper (recording paper) ) Figure 9 (C) Figure 10 (Q) (b) (C)

Claims (1)

[Scope of Claims] (1) A latent image formed on an image carrier is transferred onto recording paper by a transfer means to form an image, and the image is fixed on the recording paper by a fixing means through a conveyance path. In the image forming apparatus, the height of the conveyance path at the center with respect to the width direction of the conveyance path between the transfer means and the fixing means is set to a lower position than the height of the conveyance path near both ends. An image forming apparatus characterized by: (2) The image forming apparatus according to claim 1, wherein the conveyance path at the entrance portion of the fixing means is horizontal with respect to its width direction. (3) The image forming apparatus according to claim 1, wherein the conveyance path at the exit portion of the transfer means is horizontal with respect to its width direction. (4) The image forming apparatus according to claim 1, wherein the difference between the height of the central portion in the width direction of the conveyance path and the height of both end portions is 0.004 to 0.023 times the width of the conveyance path. (5) The image forming apparatus according to claim 1, further comprising means for aligning the recording paper in a concave shape with respect to the width direction of the conveyance path. (6) The image forming apparatus according to claim 5, wherein an air suction device or a suction plate is used as a means for forcing the recording paper along the conveyance path. (7) The image forming apparatus according to claim 1 or 6, wherein the conveyance path is constituted by conveyance ribs, and the suction plate is arranged between the conveyance ribs.