JPH043749A - Sheet conveyance device of image forming apparatus - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a sheet conveying device for an image forming apparatus that forms images using an electrophotographic method. The present invention relates to a sheet conveying device that conveys a sheet by belt.

2. Description of the Related Art In this type of sheet conveying device, a portion in front of a transfer section comes into contact with a transfer sheet that is undergoing transfer because it guides and conveys the transfer sheet to the transfer section. For this reason, if the conveyance roller or the guide plate is directly grounded, the transfer charges charged by the transfer charger to the back surface of the transfer sheet will be released, causing a transfer failure. This is noticeable in high humidity conditions where the conductivity of the transfer sheet becomes high. Furthermore, if the paper feeding device is completely ungrounded, the power will be cut off along with the transfer sheet, causing toner to adhere to various parts of the paper feeding device and staining the transfer sheet.

As a solution to this inconvenience, Japanese Patent Application Laid-Open No. 1986-
There are those described in Japanese Utility Model Publication No. 112082 and Japanese Utility Model Application Publication No. 153060/1983. In these devices, a guide member in the paper feeding device is grounded via a resistive element.

As a result, it is possible to appropriately restrict the electric charge charged on the transfer sheet from escaping via the guide member, and the above-mentioned problem can be solved.

Furthermore, several conveyor belts installed after the transfer section of the sheet conveyor are supported by a support frame in parallel, so that the conveyor belts can be used without damaging the unfixed transferred image on the transfer sheet. In order to ensure reliable conveyance, the transfer sheet is attracted and conveyed from its back side. For this reason, the transfer sheet is only partially guided and supported from the back side, making it unstable. Therefore, the support frame is provided with a portion that guides the transfer sheet. It is desired that the support frame be made of resin to reduce cost and weight.

Problems to be Solved by the Invention However, in the portion in front of the transfer unit of the sheet conveyance device, not only the guide member comes into contact with the transfer sheet during transfer, but also the conveyance rollers such as timing rollers come into contact with the transfer sheet, which increases the charging of the transfer sheet. This also causes charge to escape, but the conventional method cannot deal with this problem. Furthermore, if the support frame after the transfer section is made of resin, when the transfer sheet reaches the belt conveyance section, it will be attracted to the contact portion with the support frame and will be difficult to convey, causing wrinkles or jamming.

SUMMARY OF THE INVENTION An object of the present invention is to provide a sheet conveying device for an image forming apparatus that can solve the above-mentioned problems by improving the sheet conveying structure before and after the transfer section.

Means for Solving the Problems In order to achieve the above-mentioned problems, the present invention electrically insulates the sheet guide and conveyance roller in front of the transfer section that are in contact with the transfer sheet being transferred from the machine body, and also The present invention is characterized in that at least the portion of the support frame of the conveyor belt after the transfer section that is in contact with the transfer sheet is made of antistatic resin and is grounded through the element.

Function According to the above structure of the present invention, in front of the transfer section, the conveyance roller and the sheet guide are each insulated from the machine body and grounded via a resistive element, so that they are not in contact with the transfer sheet being transferred. Even if the transfer sheet is transferred, it is possible to appropriately suppress the escape of the electrical charge applied to the transfer sheet, and the excess charge on the conveyance roller and sheet guide is released beyond the suppressing action of the resistive element. Therefore, it is possible to avoid a situation where excessive charges accumulate and toner adheres to the transfer sheet.

Furthermore, the support frame that supports the conveyor belt after the transfer section can guide the transfer sheet from the transfer section at various parts so that it is successfully conveyed by the conveyor belt, and in this case, the parts that come into contact with the transfer sheet are Since it is made of antistatic resin, charging is suppressed and it is possible to avoid adsorption of the transfer sheet even when it comes into contact with the transfer sheet.

EXAMPLE A paper feeding device of an image forming apparatus as an example of the present invention shown in FIGS. 1 to 4 will be described below.

FIG. 1 shows a copying machine having an exposure optical system according to the present invention. This copying machine includes an exposure optical system 1, an image forming mechanism 3 that forms an image through exposure by the exposure optical system 1 and transfers it to a transfer sheet 2, and a transfer sheet 2 that is connected to the image forming mechanism 3.
It has a paper feeding mechanism 4 that feeds the paper. The exposure optical system 1, image forming mechanism 3, and paper feeding mechanism 4 are individually housed in independent optical system box 6, image forming box 7, and paper feeding box 8, respectively. The boxes 6 to 8 are stacked and connected to form a fuselage 9.

The exposure optical system 1 includes a lamp 13 that is supported by a first slider 12 that moves under a platen glass 11 to scan an original on the platen glass 11, a first mirror 14, a second slider 15, and a third slider 16. The second to fifth mirrors 17 to 20 move to keep the optical path length constant.
, a projection lens 21 provided between each of the third and fourth mirrors 18 and 19, and a sixth mirror 22 that performs optical path length correction during zooming by moving the projection lens 21 in the optical axis direction.

The image forming mechanism 3 includes a photosensitive drum 31, a charging charger 32 disposed around the photosensitive drum 31, a developing device 233, a transfer charger 34, a separation charger 135, and a cleaning device 136.
etc., and a photosensitive drum 31 using a known electrophotographic method.
A toner image corresponding to the original image to be exposed is formed on the top and transferred to the transfer sheet 2 that is fed. In front of the transfer section where the photosensitive drum 31 and the transfer charger 34 face each other, there is a paper feed box. A paper feed conveyance path 35 is provided for feeding the transfer sheet 2 received from 8 to the transfer section, and a timing roller 36 is provided on the way.The timing roller 36 feeds the transfer sheet 2 in a stopped state.
While the skew of the transfer sheet 2 is corrected by aligning the leading edge thereof, the timing of feeding the transfer sheet 2 to the transfer section is adjusted depending on the timing at which conveyance is started.

After the transfer unit, there is a conveyance device 37 that conveys the transferred transfer sheet 2 while adsorbing it to a belt, and a fixing device 38 that performs a fixing process on the transfer sheet 2 conveyed by the conveyance device 37.
, a paper discharge roller 39 for discharging the transfer sheet 2 sent out from the fixing device 38 is provided.

The paper feeding mechanism 4 has three paper feeding sections 41 to 43 that accommodate transfer sheets 2 of different sizes and selectively feed them. Each paper feed unit 41 to 43 has a paper feed cassette 44 to
Pickup roller 4 that sends out the transfer sheet 2 in 46
7 to 49, and a handling vat 51 for handling the transferred transfer sheets 2 one by one. Each paper feed section 41 to 43
Each of the blocks is divided into blocks, and the blocks can be exchanged by exchanging two blocks for one block for multiple sheets. Each paper feed section 41 to 43
The paper feed cassettes 44 to 46 are of a front loading type in which they are inserted and removed from the front side of the machine body 9, which in FIG. 1 is from the front side of the page.

The transport path of the transfer sheet 2 in the image forming mechanism 3 is shown in detail in FIG. The paper feed conveyance path 35 includes a timing roller 36 and sheet guides 61 and 62 provided before and after the timing roller 36.
An auxiliary feed roller 63 for small-sized sheets such as postcards is provided on the sheet guide 62 immediately in front of the transfer section, and directly supports this. Each of the timing roller 36, sheet guides 61, 62, and auxiliary feed roller 63 is in contact with the transfer sheet 2 during transfer, and if they are directly grounded, the charges that should be charged on the transfer sheet 2 will be released. Also, when the contact with the ground is completely released, the timing roller 3
6. The sheet guides 61 and 62 and the auxiliary feed roller 63 are charged with electricity and toner adheres to them, causing problems such as staining the transfer sheet 2.

In order to solve these problems, in this embodiment, each of the timing roller 36 and the sheet guide 61, 62 is provided with an insulating support part 65, 66, .
67, and is electrically insulated from the fuselage 9. Also, the auxiliary feed roller 63
is made of a conductive material such as metal or conductive rubber, and is electrically connected to the sheet guide 62. These timing rollers 36 and sheet guides 61.6
2 is grounded via a varistor 68. As a result, the auxiliary feed roller 63 is also grounded through the sheet guide 62 and the varistor.

The transfer sheet 2 during transfer is transferred to the timing roller 36,
Even when the transfer sheet 2 contacts the sheet guides 61, 62 and the auxiliary feed roller 63, it is possible to suppress the charge on the transfer sheet 2 from escaping and ensure that the transfer is performed successfully. Also, timing roller 36, sheet guide 61.6
2. Even if each of the auxiliary feed rollers 63 is excessively charged, the excess charge is released beyond the control of the varistor 68. This prevents excess charge from remaining and causing toner to adhere and staining the transfer sheet 2.

Further, in the conveyance device 37 located immediately after the transfer section, at least the portion of the resin frame 72 that supports the perforated belt 71 that contacts the transfer sheet 2 is made of antistatic resin. In this embodiment, the entire resin frame 72 including the side guide 72a that guides the transfer sheet 2 from the side and receives it in the perforated belt 71, and the transfer sheet 2 disposed beside each perforated belt 71, A resin transfer sheet guide 73 that guides the transfer sheet 2 from the bottom surface is made of antistatic resin. The antistatic resin has a surface resistivity of, for example, about 10 8 to 10 13 Ω, and has an antistatic effect. As a result, even if the transfer sheet 2 after transfer reaches the conveyance device 37 and comes into contact with the resin frame 72, the transfer sheet guide 73, etc., it will not be attracted to them due to static electricity and will be conveyed smoothly. Therefore, by using resin for the main structure of the conveyance device 37, cost reduction and weight reduction can be realized without any problem in conveying the transfer sheet 2. As the antistatic resin, there is Toyorank Barrel, an ABS resin-based permanent antistatic resin manufactured by Toshi Co., Ltd.

As shown in FIGS. 2 to 4, the perforated belt 71 is stretched by rollers 75 and 76 that are supported by U-shaped bearings 74 formed on the upper surface of the resin frame 72. Each transfer sheet guide 73 has rollers 75 and 76 attached to the bearing portion 7.
It also has the function of holding it down within 4 and ensuring stable rotation. Here, the perforated belt 71 is stretched by the roller 7
5.76, as shown in FIG. 4, by fitting each roller 75, 76 into the opposing bearing part 74 from the same side with the hooks being crossed, and then pressing each part with the transfer sheet guide 73. It can be easily assembled to the resin frame 72. The transfer sheet guide 73 is attached to the resin frame 72 using screws 95 and engagement pieces 96.

A suction box 77 for suctioning the transfer sheet 2 is located inside the perforated belt 71 and must be attached to the resin frame 72 with screws 78. The procedure for this operation is to insert the suction box 77 inside the perforated belt 71 before either or both of the rollers 75 and 76 are fitted into the bearing portion 74. Next, when both or the remaining rollers 75 and 76 are fitted into the bearing part 74 and the porous heald 71 is placed along the top surface of the resin frame 72, the suction box 77 can also be placed along the top surface of the resin frame 72 at the same time, and the suction box 77 can be placed along the top surface of the resin frame 72. It can be screwed with a screw 78. In other words, the perforated belt 71 and the suction box 77 inside the belt can be attached to the resin frame 72 from one side all at once.

The suction box 77 is formed by coupling an upper plate 77a and a lower plate 77b by elastic engagement between an engagement spring 81 and an engagement hook 82. Each porous belt 71 is attached to the upper plate 77a.
A suction port 83 facing the suction fan 84 is formed in the lower plate 77b, and a connection port 85 with a suction fan 84 is formed in the lower plate 77b.

The suction fan 84 has upper and lower casings 84a, 84
A separate car 86 is housed between the spaces B and is attached to the resin frame 72 from the back side, so that the suction port 87 communicates with the connection port 85 of the suction box 77 through the connection port 88 of the resin frame 72. It's Nishide. 89 is an exhaust port of the suction fan 84.

By the way, as shown in FIG. 2, the sheet guide 62 forms a bent sheet feeding path from the timing roller 36 to the transfer section, so that when a thick sheet such as a postcard passes through the timing roller 36, it The edge jumps up, and the vibration of the transfer sheet 2 at that time affects the transfer and distorts the image. To solve this problem, an elastic resin sheet 91 extending toward the timing roller 36 is attached to the upper guide 62a of the sheet guide 62. This sheet 91
is a slightly stiff and thin elastic sheet made of polyethylene terephthalate (PET), and even if the rear end of the thick transfer sheet 2 passes through the timing roller 36 and tries to jump up, it is prevented by its own elasticity, and the transfer sheet 2 can be stably transferred until the end.

Furthermore, in the case where the fuser 38 performs heat fixing, if the transfer sheet 2 is in a high humidity state, a lot of steam will be generated during the fixing, and this will cause a large temperature difference between the transfer sheet 2 and the fuser 38 part in particular. That is, dew condensation occurs on the sheet guide 93 and the like on the side farther away from the fixing device 38. For this reason, when the transfer sheet 2 leaving the fixing device 38 reaches the sheet guide 93, the leading edge of the transfer sheet 2 comes into close contact with the sheet guide 62, which may result in jamming without being conveyed. This is thin transfer sheet 2
Significant in cases of In this embodiment, in order to solve this problem, an elastic resin sheet 94 extending toward the paper ejection roller 39 is provided at the bent portion of the front end of the upper guide 93a of the sheet guide 93, where the transfer sheet 2 is likely to adhere. Elastic resin sheet 94
is the elastic resin sheet 91 immediately after the timing roller 36
The transfer sheet 2 may be of the same quality as the metal sheet guide 93, and the steam is less likely to condense, and the transfer sheet 2 can be smoothly guided to the paper ejection roller 39 and reliably ejected.

Note that in this embodiment, the timing roller 3 of the paper feed conveyance path 35
6. Although a varistor is used to ground the sheet guides 61 and 62, the present invention is not limited to this, and any material can be used as long as it can appropriately suppress the escape of charge. In this sense, a resistor or the like may be used, and in general, a resistive element may be used. Further, although this embodiment has been shown only in the case of a copying machine, the present invention can be applied to all image forming apparatuses that form images using an electrophotographic method, such as printers.

Furthermore, the specific configuration of the sheet conveying device is not limited to the embodiments, and can be modified in various ways.

Effects of the Invention According to the present invention, in front of the transfer unit, each of the conveyance roller and the sheet guide is insulated from the machine body and grounded via a resistive element, and is in contact with the transfer sheet being transferred. Also, since the transfer sheet appropriately suppresses the escape of the electrical charges applied for the transfer, the transfer can be performed satisfactorily. In addition, excess charges on the conveyance rollers and sheet guides are released beyond the suppressing action of the resistive element, so that it is possible to avoid excessive charges from accumulating and causing toner to adhere to the transfer sheet and staining the transfer sheet.

Furthermore, the support frame of the conveyor belt after the transfer section can guide the transfer sheet from the transfer section at various parts so that it is successfully conveyed by the conveyor belt, and in this case, the parts that come into contact with the transfer sheet are antistatic. Since the transfer sheet is made of a synthetic resin and suppresses charging, it is possible to avoid the transfer sheet from being attracted, and the transfer sheet is prevented from being adsorbed and being prevented from conveying, causing wrinkles or jams. I can do it.

As a result of the above, in the present invention, transfer is successfully performed and image formation with comparable image quality and sheet quality is reliably achieved.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional front view of a copying machine having a paper feeding device as an embodiment of the present invention, FIG. 2 is an enlarged view showing the conveyance path of a transfer sheet, and FIG. 3 is an enlarged front view of a suction conveyance device. , FIG. 4 is an exploded perspective view of the suction conveyance device. Insulating member - Varistor 111 - Porous belt - Resin frame - One side guide Transfer sheet guide 65.66.67 68. −−−−−−−−− 72a −−−−− 73−・−1−−−−−

Claims (1)

[Claims] (1) A support frame that electrically insulates the sheet guide and conveyance roller in front of the transfer section that are in contact with the transfer sheet being transferred from the machine body, and that is grounded via a resistance element and supports the conveyance belt after the transfer section. 1. A sheet conveying device for an image forming apparatus, wherein at least a portion of the sheet in contact with a transfer sheet is formed of an antistatic resin.