JPH02259791A - Heat fixing device - Google Patents

Abstract

PURPOSE:To miniaturize a device and to prevent jam by forming a guide so that a fixed material is guided to a press-contacting part between a heating roller and a pressing roller. CONSTITUTION:The device is provided with a dividing part 8 formed in the form of a circular groove on the other periphery of the pressing roller 5 and the guide 9 formed so as to guide the fixed material 7 through the dividing part 8, the pressing rollers 5 and 6 to the press-contacting part between the heating roller 1 and the pressing roller 6. Additionally, the heating source 4 is energized, and the roller 1 reaches the prescribed temperature. When the fixed material 7 is supplied to the top surface and is held and carried by the roller 1 and the rollers 5 and 6, the toner image is fixed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is directed to an image forming apparatus such as an electrophotographic apparatus or an electrostatic printing apparatus by heating a toner image formed on a piece of paper or other object to be fixed. The present invention relates to a heat fixing device that performs fixing, and particularly relates to a heat fixing device that can be made into a square shape and can prevent paper jams.

[Conventional technology]

Conventionally, as a device for fixing a toner image formed on a recording medium or carrier such as a zinc oxide photosensitive paper, a passing paper sheet, or a plastic sheet, a heating roll and a pressure roll held in pressure contact with each other have been used. In between, a heat fixing device is used which passes the carrier in a pinched state and heats and pressurizes the carrier.

In such devices, a pressure roll whose outer surface is covered with a heat-resistant elastic material layer is brought into pressure contact with a heating roll, so as to secure a predetermined contact width or nip width between the two rolls. Generally, the outer diameter is 30~
It is normal to form it with a length of 50 m.

[Problem to be solved by the invention]

In the above fixing device, it is necessary to increase the size of the nip cap formed between the heating roll and the pressure roll in order to ensure the amount of heat transferred to the fixing object carrying the unfixed toner image. On the other hand, in order to meet the recent demand for smaller equipment, there is a trend toward smaller diameters for both heating rolls and pressure rolls.
The above-mentioned nip cap is even smaller (because it becomes smaller, so from the viewpoint of ensuring the heat transfer M, it is common to use an elastic material such as silicone rubber for the pressure roll. However, in the case of such a structure, Since the surface of the pressure roll that comes into contact with the heating roll tends to be a concave surface with a relatively small radius of curvature, there is a problem in that the object to be fixed discharged from the fixing section curls and winds around the heating roll. Furthermore, there is a tendency for development speeds to gradually increase, and it is natural that a similar increase in speed is required for the above-mentioned fixing device.

In a conventional fixing device in which a heating roll and a pressure roll are opposed to each other, there is a problem in that it is impossible to simultaneously satisfy the requirements of miniaturizing the device, increasing speed, and ensuring nip width. . On the other hand, in order to secure the nip width and reduce the diameter of the pressure roll, a proposal was made to press a plurality of pressure rolls onto a heating roll (Japanese Patent Publication No. 5B-21262
However, there is a problem in that paper jams occur between a plurality of pressure rolls.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a heat fixing device that solves the problems existing in the above-mentioned prior art, can be downsized, and can prevent single paper jams.

[Means to solve the problem]

In order to achieve the above object, one aspect of the present invention is as follows.

Equipped with a rotatable heating roll with a built-in heat source.

Two pressure rolls whose axes are parallel to the heating roll and rotatable are arranged in pressure contact with the heating roll, and an annular groove-shaped dividing part is formed on the outer periphery of the pressure roll on the upstream side of the object to be fixed. One or more are provided in the axial direction, and a guide is provided extending between these divided portions and the two pressure rolls so as to guide the object to be fixed to the pressure contact portion between the heating roll and the pressure roll. . A technical method was adopted.

In the present invention, the outer diameter of the pressure roll can be made smaller than the outer diameter of the heating roll.

[Effect]

With the above configuration, since the two pressure rolls are brought into pressure contact with the heating roll, a predetermined nip width can be secured, and the guide provided between the split part of one pressure roll and the two pressure rolls Therefore, the object to be fixed can be reliably guided between the heating roll and the pressure roll, and paper jams can be prevented.

〔Example〕

FIG. 1 is a cross-sectional view of essential parts showing an embodiment of the present invention.

FIG. 2 is a view taken along line A--A in FIG. 1.

In both figures, reference numeral 1 denotes a heating roll 0. A mold release member made of a fluororesin material such as PFA or PTFE is placed on a core metal 2 formed into a hollow cylindrical shape from a material with good thermal conductivity such as aluminum or an aluminum alloy. sex layer 3
along with covering it.

A heat source 4 is provided inside. Incidentally, a shaft (not shown) is fixed to both ends of the heating roll 1 so that it can rotate freely.
, 6 are pressure rolls, and a heat-resistant elastic layer 5b made of a material such as silicone rubber is provided around the shafts 5a and 6a.
, 6b are formed and disposed close to the upstream and downstream sides of the object to be fixed 7, which will be described later, and are brought into pressure contact with the outer periphery of the heating roll 1. The axes of the pressure rolls 5 and 6 are arranged parallel to the axis of the heating roll 1, and these rolls are configured to rotate at the same circumferential speed. The object to be fixed 7 carrying a toner image (not shown) is placed between the heating roll 1 and the pressure roller 5.6.

A dividing part 8 formed in an annular groove shape is provided on the outer periphery of the sixth pressurizing roll 5 that can be pinched and conveyed in the direction of the arrow.
A guide 9 is provided that extends between the divided portion 8 and the pressure roll 5.degree.6 and is formed so as to guide the object to be fixed 7 to the pressure contact portion between the heating roll 1 and the pressure roll 6.

With the above configuration, the heating roll 1 is heated to a predetermined temperature by energizing the heat generating source 4, and the fixing object 7 carrying the toner image on its upper surface is fed in the direction of the arrow. By nipping and conveying the toner image between the heating roll 1 and the pressure roll 5.6, the toner image can be fixed. In this case, if the pressure roll 5.6 is formed to have a smaller outer diameter than the heating roll 1, the entire heat fixing device can be downsized. On the other hand, even if the nip width decreases due to a decrease in the outer diameter of the pressure rolls 5 and 6, the overall nip width is This makes it possible to secure a sufficient amount of fixation and perform the desired fixing. In addition, when the object to be fixed 7 moves from the pressure roll 5 to the pressure contact portion of the pressure roll 6, it is guided by a guide 9 provided between the two pressure rolls 5 and 6, which prevents inconveniences such as paper jams. It is possible to prevent this from occurring. Furthermore, when the width dimension (dimension in the roll axis direction) of the fixing object 7 is small, for example, for A2 size or A
A large size fixing device for 3rd editions allows you to print 5th, e.g. A3 or 8th
When fixing the 5th version of paper, especially the pressure roll 5.
Although jamming occurs frequently between the fixing objects 7 and 6, since the dividing section 8 is provided on the pressure roll 5 on the upstream side of the fixing object 7 and the guide 9 is also present in this dividing section 8, the jamming occurs frequently between the fixing objects 7. The guide to the pressure roll 6 side is extremely smooth and can be expected to prevent paper jams.

In this embodiment, an example is shown in which the number of divided portions to be provided on the pressure roll on the upstream side of the fixing object is one, but it is also possible to provide a plurality of such divided portions in the axial direction, and the number of divided portions between these divided portions is It is also possible to set the installation intervals to different dimensions, and the same effect can be expected in either case.

〔Effect of the invention〕

Since the present invention has the structure and operation as described above, it is possible to downsize the entire heat fixing device by reducing the diameter of the pressure roll, and also prevent paper jams even if the conveyance speed is increased. It has the effect of gaining.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of essential parts showing an embodiment of the present invention. FIG. 2 is a view taken along arrow A-Afi in FIG. 1: heating roll, 5□ 6: pressure roll, 8: dividing part,
9ni guide. Treetop 1 diagram

Claims (2)

[Claims] (1) A heating roll with a built-in heat source is rotatably provided,
Two pressure rolls whose axes are parallel to the heating roll and rotatable are arranged in pressure contact with the heating roll, and an annular groove-shaped dividing part is formed on the outer periphery of the pressure roll on the upstream side of the object to be fixed. One or more are provided in the axial direction, and a guide is provided between these divided portions and the two pressure rolls so as to guide the object to be fixed to the pressure contact portion between the heating roll and the pressure roll. A heat fixing device characterized by: (2) The heat fixing device according to claim 1, wherein the pressure roll has an outer diameter smaller than the heating roll.