JP3058202B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus, and more particularly, to an image forming apparatus used in a copying machine, a facsimile, a personal computer, a word processor and the like.

[0002]

2. Description of the Related Art To form an image on plain paper, a so-called transfer type electrophotographic system for transferring a toner image formed on a photoreceptor is widely used. Incidentally, printers and facsimile machines employing this type of transfer type electrophotographic system are disclosed in Japanese Patent Application Laid-Open Nos. Hei 2-212857 and Hei 2-166.
As can be seen in Japanese Patent Application Publication No. 472, the drive system for transmitting power to the electrophotographic process system and the recording medium transport system are not only complicated because they coexist. During operation, a relative displacement between these systems occurs due to existing mechanical play, which causes unclear image formation, and in addition to the former, the transfer and fixing are performed before and after. However, there is also a problem that the unfixed toner transferred in the process of transporting the recording medium is disturbed.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of such a problem.
A new image forming apparatus that simplifies the mechanism and enables clear image formation by integrating the recording medium transport system and the electrophotographic process system into a single system and performing simultaneous transfer and fixing To provide.

[0004]

According to the present invention, there is provided an image forming apparatus for achieving the above object, comprising: a platen roller rotating at the same peripheral speed as a photosensitive member and having at least an outer peripheral surface made of a dielectric material; A heat-resistant and insulating endless belt is stretched over a small-diameter heating roller disposed in the vicinity of the discharge section so that the platen-roller-side winding portion comes into contact with the peripheral surface of the photoconductor and the supply-side recording medium. It was done.

[0005]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. The drawings show an embodiment of the present invention. In the figure, reference numeral 1 denotes a gear that meshes with the drum drive gear or a platen roller that rotates at the same peripheral speed as the photosensitive drum 6 in contact with the peripheral surface of the end of the photosensitive drum 6. The endless belt 2, which is formed of a material or at least a peripheral surface of which is coated with a dielectric material and wound around the peripheral surface, is transferred onto the peripheral surface of the photosensitive drum 6 and the transfer paper s in the paper feed cassette 10. The toner image and the transfer paper s are simultaneously held and conveyed in contact with each other.

On the other hand, a film-shaped endless belt 2 stretched between the platen roller 1 and a heating roller 3 disposed above the platen roller 1 is formed of a heat-resistant insulating material such as polyimide or PET. Then, the toner image formed on the photosensitive drum 6 is electrostatically attracted by a voltage having a polarity opposite to that of the toner applied to the platen roller 1, and the transfer paper s in the paper cassette 10 is attracted and held. These are integrally conveyed to the heating roller 3, and the transfer and fixing process is simultaneously performed by the mechanical heating and pressing action acting between the heating roller 3 and the pressing roller 4. .

On the other hand, an intermediate plate 13 on which the transfer paper s is placed is provided in a paper feed cassette 12 which can be inserted and removed below the platen roller 1. A pressing spring 14 for pressing the transfer sheet s against the surface of the endless belt 2 sometimes acts on the lower surface thereof, and a part of the intermediate plate 13 is brought into contact with the belt 2 from the non-contact position only during paper feeding. A cam 15 for displacing the middle plate 13 to the position is provided. In the drawing, reference numeral 7 denotes a charger, 8 denotes a laser beam scanner, 9 denotes a developing unit, 10 denotes a cleaning unit, and 17 denotes a paper discharge tray.

In the image forming apparatus constructed as described above, first, a latent image is formed on a uniformly charged photosensitive drum 6 by a laser beam scanner 8 and then developed by a developing unit 9 as a toner image. The endless belt 2 in the same system moving at a constant speed in contact with the peripheral surface of the photosensitive drum 6 on the roller 1 is formed on the photosensitive drum 6 by an electric field acting via the platen roller 1. Electrostatically adsorbs toner.

On the other hand, when a latent image is written on the photosensitive drum 6, the cam 15 is inverted so that the missing portion is directed downward, and the cam 13 is pushed up by the urging force of the pressing spring 14, and the cam 15 is pushed up. The uppermost transfer paper s placed on the endless belt 2
Abut. As a result, the uppermost transfer paper s is electrostatically attracted to the surface of the endless belt 2 to which the toner image has been transferred, and is held on the surface of the endless belt 2 without causing relative movement with the toner image. While being conveyed to the heating roller 3 and the pressure roller 4 while being subjected to a mechanical heating and pressing action, the toner image is discharged to the discharge tray 17 integrally with the toner image on the endless belt 2. .

As described above, the heating roller 3 disposed above the platen roller 1 has a very small diameter, and the endless belt 2 is turned over with a large curvature. The transfer paper s which has been linearly transferred to the heating roller 3 cannot follow the large curvature of the belt 2 at the point where it has passed the heating roller 3, and in addition, the potential remaining on the endless belt 2 in this portion is also weak. Therefore, the transfer paper s is smoothly discharged from the endless belt 2 to the discharge tray 17 in the horizontal direction as it is.

[0011]

As described above, according to the present invention, the heat resistance and the heat resistance and the supply side recording medium are brought into contact with the peripheral surface of the platen roller rotating at the same peripheral speed as the photosensitive member. Since the insulating endless belt is wound, the electrophotographic process system and the recording medium transport system can be combined as one system via the endless belt wound around the platen roller. Clear image formation is possible by eliminating a relative speed difference generated between the transfer system and the image forming apparatus, and this type of image forming apparatus can be greatly simplified.

Further, since the other half of the endless belt is wound with a large curvature around a small-diameter heating roller disposed near the recording medium discharge section, the recording is electrostatically attracted together with the toner image and conveyed integrally. The medium in this part at the same time,
Transfer and fixing can be performed, and the recording medium conveyed in a straight line can be easily peeled off from an endless belt that reverses with a large curvature without requiring any peeling means, and can be discharged.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an apparatus showing one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Platen roller 2 Endless belt 3 Heating roller 4 Pressure roller 6 Photoreceptor drum 7 Charger 8 Laser beam scanner 9 Developing unit 12 Paper feed cassette 17 Paper discharge tray

Claims (1)

(57) [Claims] A heat-resistant and insulating endless belt is provided on a platen roller which is rotated at the same peripheral speed as the photoreceptor and has at least an outer peripheral surface made of a dielectric material, and a small-diameter heating roller disposed near a recording medium discharge portion. An image forming apparatus, wherein a winding portion on a platen roller side is in contact with a peripheral surface of the photoconductor and a recording medium on a supply side.