JP2001240268A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of freely changing a transfer sheet feeding route from a transfer part to a fixing unit so as to increase the feedability of various types of transfer sheets and the tolerance of an image quality. SOLUTION: A transfer tank 15 comprises guides A and B foldable into two parts and a plurality of sheet feed belt 16. A fixing inlet guide 17 is formed integrally, at a proper angle, with the guide A on the feeding direction downstream side of the transfer sheet. An angle switching mechanism using an eccentric cam 21 is provided so as to vary the angle of the guide on the downstream side. The position of the eccentric cam 21 (height of guide A) is changed by the rotation of a drive motor 22.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a facsimile, a printer, etc., and more particularly, to a paper between a transfer section and a fixing section of an image forming apparatus which requires a wide range of paper types. The present invention relates to a device having improved transportability.

[0002]

2. Description of the Related Art In a conventional image forming apparatus of this type, a relay transport unit (hereinafter, referred to as a transport tank) between a secondary transfer unit and a fixing unit is used.
Is an integral type and has been used as a device for transporting transfer paper at a fixed angle with respect to the lower guide plate at the entrance of the fixing unit. Also, since the height and angle of the lower guide plate at the entrance of the fixing unit are fixed, the transferability of all types of transfer paper, from thin paper to postcard size, or from thin paper to ultra-thick paper, and a margin for image quality It was difficult to satisfy.

That is, when the size of the transfer paper is longer than the dimension of the fixing unit (between the nip and the secondary transfer portion), when the leading edge of the transfer paper enters the nip of the fixing unit, vibration occurs at the transfer position and the image is generated. Transfer blur is easy to occur. In such a case, it has been found that it is better to enter the nip of the fixing unit from above from thick paper, ultra-thick paper, or sized paper. Conversely, in the case of small size and thick paper such as a postcard, if the paper enters the fixing unit from above the nip, the leading edge of the transfer paper does not enter the nip smoothly, causing a jam that stops inside the fixing unit. I know it's easy. Therefore, it is desirable that the above-described type of transfer paper enter the nip from the same position or from below.

In addition, in the case of small-sized and thick paper such as a postcard, the contact area with the intermediate conveyance unit (belt) is small, and the rear end of the transfer paper easily floats from the conveyance tank when the fixing unit enters the nip. Therefore, it is also known that the transfer paper transfer angle of the transfer tank with respect to the nip direction of the fixing unit leads to a margin for jam.

Accordingly, the present invention can improve the transportability of various types of transfer paper and the margin of image quality by freely changing the transfer paper transport path from the transfer section to the fixing unit. It is an object of the present invention to provide an image forming apparatus according to the present invention.

[0006]

According to a first aspect of the present invention, there is provided an image forming apparatus comprising: a sheet feeding device for supplying a transfer sheet; A transfer device that forms an image on the surface of the supplied transfer paper, a relay conveyance unit that conveys the transfer paper on which the toner image has been formed by the transfer device, and a semi-permanent fixing of the toner image formed on the transfer paper An electrophotographic image forming apparatus including a fixing unit for causing the relay conveyance unit to divide at least two in the transfer direction of the transfer sheet, and changing at least one of the divided units to a transfer angle of the transfer sheet. It is characterized by being supported.

According to a second aspect of the present invention, in order to achieve the above object, a split unit having a variable transport angle is disposed on the fixing unit side, and the transport angle of the split unit is variable. It is characterized by comprising.

According to a third aspect of the present invention, in order to achieve the above object, the means for varying the transport angle of the division unit varies the transfer paper transport angle of the division unit in a plurality of stages. There is a feature.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing the basic overall configuration of an embodiment of the image forming apparatus according to the present invention. The transfer paper fed from the manual feed tray 1 or the paper feed tray 2 is temporarily stopped at the position of the registration roller 3, and at the same time, the reading, writing, charging, exposure, development, and primary transfer of the original image are performed in parallel with the original image. The basic steps of image formation in the system are performed, a toner image is formed on the primary transfer belt 10, and the transfer paper is restarted from the temporary stop state by the registration roller 3, and the primary transfer belts 10 and 2 are transferred. An unfixed image is formed on the surface of the transfer sheet when the sheet can pass through the nip formed between the transfer roller 11 and the next transfer roller 11. It is needless to say that the present invention can be applied not only to the case where the secondary transfer member is a roller but also to the case where the secondary transfer member is a belt.

Thereafter, the conveyor belt 1 in the conveyor tank 15
6, the transfer paper is conveyed to the fixing unit 25, and the transfer paper guided by the fixing entrance guide 17 is caused to enter the nip formed by the heating roll 26 and the pressure roll 27, so that the unfixed toner on the surface of the transfer paper is The image is fixed to form a semi-permanent image, and then the transfer paper is discharged to the output tray
Discharge to zero.

FIG. 2 is a perspective view of the transport tank of the apparatus shown in FIG. The transport tank 15 is formed by guides A and B that can be folded in two and a plurality of paper transport belts 16, and the fixing entrance guide 17 has an appropriate angle with respect to the guide A on the downstream side in the transfer paper transport direction. It is integrally formed to hold. The fixing entrance guide 17 is urged downward by a spring 23. Fixing entrance guide 1
7 may be provided detachably with respect to the guide A.

An angle (height) switching mechanism using an eccentric cam 21 is provided to vary the angle of the guide A on the downstream side. The angle can be changed around the drive shaft). The bearing 19A of the rotating shaft 19 and the bearing 19B of the guide B are fixed to side plates of an image forming apparatus main body (not shown).

FIG. 3 is a side view showing the movement of the eccentric cam 21 and the guide A. The position of the eccentric cam 21, that is, the height of the guide A is determined by the rotation amount of the drive motor 22. In switching only up and down, as shown in FIG. 3, the nip formed by the heating roll 26 and the pressure roll 27 of the fixing unit 25 can be changed only at two positions.
FIG. 4 shows the shape of the eccentric cam 21a for adjusting the height in three steps, such as high, medium and low. In any case, it is necessary to link the rotation amount or the rotation direction of the drive motor 22.

Such a configuration and keys on an operation panel of the image forming apparatus main body (not shown; for example, postcard mode, etc.)
Alternatively, by associating a program, the height of the fixing entrance guide 17 and the angle of the guide A can be changed while being set in the image forming apparatus main body.

FIG. 5 is a side view showing a measure for improving the transferability of the transfer paper and the image quality margin in the embodiment of the present invention. FIG. 5A shows a normal state, that is, a state in which transfer paper from thin paper to plain paper is transported. The fixing inlet guide 17 in the transport tank 15 is set to an optimal angle so as to face the nip direction of the fixing unit 25. It is. FIG.
7B and 7C show a setting state for conveying large-size thick paper and ultra-thick paper, and the fixing entrance guide 17 is set at an angle such that it faces upward from the nip direction of the fixing unit 25. . Further, FIG. 5D shows a setting state for conveying a postcard and a small-sized cardboard, FIG. 5E shows an enlarged view thereof, and the fixing entrance guide 17 includes a fixing unit 25.
Is set to face downward from the nip direction. That is, the angle θ between the transfer sheet P and the guide A when the transfer sheet P is added to the nip of the fixing unit 25 is shown in FIG.
5B, the rear end of the transfer paper P can be pressed in a state as shown in FIG. 5E, so that the transport quality is reliably stabilized.

[0016]

Since the image forming apparatus according to the present invention is as described above, it is possible to improve the transportability of various kinds of transfer paper and the margin of image quality. There is an effect that it becomes possible to provide an image forming apparatus such as a printer.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a basic entire configuration of an embodiment of an image forming apparatus according to the present invention.

FIG. 2 is a perspective view of a transfer tank of the embodiment apparatus of FIG. 1;

FIG. 3 is a side view showing movement of an eccentric cam and a guide of the embodiment device of FIG. 1;

FIG. 4 is a side view showing another shape of the eccentric cam of FIG. 3;

FIG. 5 is a side view showing measures for improving transferability of transfer paper and improving image image margin in the embodiment of the present invention.

[Explanation of symbols]

 Guides A and B 1 Manual tray 2 Paper feed tray 3 Registration roller 5 Photoconductor unit 6 Developing unit 7 Belt cleaning 10 Primary transfer belt 11 Secondary transfer roller 15 Relay transport unit (transport tank) 16 Paper transport belt 17 Fixing entrance guide Reference Signs List 18 Conveyor belt drive roller 19 Rotary shaft 20 Conveyor belt drive gear 21 Eccentric cam 22 Eccentric cam drive motor 23 Tension spring 25 Fixing unit 26 Heating roller 27 Pressure roller 30 Discharge tray

Claims (3)

[Claims] A paper feeder for supplying a transfer paper, a transfer device for forming an image on a surface of the transfer paper supplied by the paper feeder, and a transfer of the transfer paper on which a toner image is formed by the transfer device And a fixing unit for semi-permanently fixing the toner image formed on the transfer paper, the relay conveyance unit at least in the transfer direction of the transfer paper in the electrophotographic image forming apparatus. An image forming apparatus, wherein the image forming apparatus is divided into two and at least one of the divided units is variably supported at a transfer angle of the transfer sheet. 2. The image forming apparatus according to claim 1, further comprising: a split unit having a variable transport angle disposed on the fixing unit side; and a unit configured to vary a transport angle of the split unit. 3. The image forming apparatus according to claim 2, wherein the means for varying the transport angle of the division unit varies the transfer paper transport angle of the division unit in a plurality of stages.