JPH06274053A - Heating device - Google Patents

Abstract

PURPOSE:To prevent offset by electrical factor that electrostatically charged toner on a recording material is electrostatically transferred to film in a heating device for applying heat energy from a heating body to a body to be heated through the film. CONSTITUTION:The film is brought into contact with the fixedly supported heating body so as to slide thereon, and the material to be heated is brought into tight contact with the surface of the film on an opposite side to the heating body and moved to pass the position of the heating body with the film, so that the heat energy is applied to the material to be heated from the heating body through the film in the one-side reference heating device. An electric contact 9 for the film 2 is provided on a counter-reference side being an opposite side to the reference side of a butting reference plate, etc., and the electrostatic charge of the film is eliminated through the contact 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating device of the type which applies heat energy to a recording material through a heat resistant film.

This device is used for electrophotographic copying machines, printers,
An image heating device in an image forming apparatus such as a fax, that is, an image forming process means such as electrophotography, electrostatic recording, magnetic recording, etc., uses a recording material (electrofax sheet, electrostatic recording Recording that carries an unfixed toner image corresponding to the target image information that is directly formed on the surface of the sheet, recording material sheet, printing paper, etc., or indirect (transfer) method. It can be utilized as an image forming apparatus that performs heat fixing processing as a permanently fixed image on a material surface.

Further, it is not limited to the image forming apparatus, but can be widely used as a means and a device for heating the image carrier, such as a device for heating a recording material carrying an image to modify the surface property.

[0004]

2. Description of the Related Art Conventionally, for example, as a heating device for a recording material for heat fixing an image, a heating roller maintained at a predetermined temperature and a pressurizing member having an elastic layer for press-contacting the heating roller. A heat roller system is often used which has rollers and heats the recording material on which an unfixed toner image is formed while nipping and conveying the recording material.

Further, the applicant has previously disclosed Japanese Patent Laid-Open No. 63-31318.
Japanese Patent No. 2 discloses a fixedly supported heating element (thermal heater).
A heat-resistant film (fixing film) that is conveyed while being pressed against the heater, and a pressing member that brings the recording material into close contact with the heater via the film, and the heat of the heater is transferred through the film to the recording material. We have proposed a fixing device of a system and configuration in which an unfixed image formed and carried on the surface of a recording material is heated and fixed on the surface of the recording material by applying to the recording material. In such a film heating type fixing device, a low heat capacity heater can be used as a heater. Therefore, it is possible to save power and shorten the wait time (quick start) as compared with the conventional contact heating method such as the heat roller method and the belt heating method.

[0006]

[Problems to be Solved by the Invention] However, as a problem,
There is a point that a so-called toner offset phenomenon may be observed in which a part of the unfixed toner on the recording material is transferred and attached to the film surface. The occurrence of the toner offset can be roughly classified into a temperature factor and an electrostatic factor.

The former offset due to temperature is a low temperature offset in which the temperature of the toner in the fixing device is too low to offset without fixing, and a high temperature offset in which the toner temperature is too high and the toner melts in a liquid state. These can be prevented by appropriately setting the characteristics of the developer used, the recording material conveying speed, the pressing force, and the temperature control means.

On the other hand, in the latter electrostatic factor offset, the charged toner on the recording material is electrostatically transferred to the film. Since this phenomenon largely depends on the type of recording material, environment, material and resistance of the pressure member, etc., it is difficult to control, and adverse effects due to offset, for example, recording material stain due to retransfer of offset toner, offset toner The recording material may be wound around the pressure member due to the toner being attached to the pressure member and soiling the toner.
As a countermeasure against this, there is a method of grounding the film or grounding via a rectifying element, but it was difficult to always secure stable contacts because the thin and soft film moves and rotates.

[0009]

SUMMARY OF THE INVENTION In order to solve the above problems, in the present invention, in a heating device in which there is a reference on one side for all recording material sizes (one side reference), a reference plate with contact points is provided. It is possible to prevent contact failure due to paper dust, etc., and to obtain stable conduction at all times by installing it in the non-heated area on the anti-reference side rather than the reference side where paper dust is often generated by rubbing against etc. Can be prevented.

[0010]

【Example】

<Embodiment 1> FIG. 1 is a cross-sectional view showing a schematic configuration of a tensionless film heating type heating apparatus as an embodiment of the present invention. In this embodiment, this heating device is used as an image heating and fixing device of the image forming apparatus.

In FIG. 1, reference numeral 1 denotes a heat-resistant resin-made lateral stay, which serves as an inner surface guide member for an endless heat-resistant film 2 described below.

2 is an endless heat-resistant film,
The stay 1 including the heater 3 is externally fitted. The inner peripheral length of the endless heat-resistant film 2 and the outer peripheral length of the stay 1 including the heater 3 are larger than those of the film 2 by, for example, 3 mm. The length fits loosely with a margin.

The heater 3 is a substrate 3A made of alumina or the like.
An electric resistance material (heating element) 4 such as Ag / Pd (silver-palladium) is applied along the substantially central portion of the above to a thickness of 10 μm and a width of 1 to 3 mm by scream printing or the like, and as a protective layer 5 thereon. It is coated with glass or fluororesin.

A film pressure roller 6 forms a fixing nip portion N with the heater 3 sandwiching the film 2 and drives the film 2. The film pressure roller 6 is a grounded central shaft 7 and this shaft. The roller shaft 8 is made of a heat-resistant rubber elastic body having a good releasability, such as an external silicone rubber.
The end portion of is driven by a driving unit (not shown) to be rotationally driven in the counterclockwise direction indicated by the arrow. When the pressure roller 6 is rotationally driven, the endless heat resistant film 2 is also rotationally driven in the clockwise direction shown by the arrow.

When the endless heat-resistant film 2 is not driven, most of the remaining portion, except for the portion sandwiched by the nip N between the heater 3 and the pressure roller 4, is tension-free. .

When the pressure roller 6 is rotationally driven, a moving force is applied to the film 2 at the nip portion N by a frictional force between the film 2 and the rotary pressure roller 6, so that the film 2 rotates at substantially the same speed as the rotational peripheral speed of the pressure roller 6. Then, the back surface of the film is driven to rotate clockwise while sliding on the surface of the heating element 3 (= the surface of the protective layer 5).
When the film is driven, tension is applied to the film only at the nip portion N and on the upstream side of the nip portion N in the moving direction of the film, and between the nip portion and the film inner surface guide portion near the nip portion.

While the film is being driven and the heating element 4 of the heater 3 is being energized, the recording material P carrying the unfixed toner image T is formed between the rotating film 2 in the nip portion N and the rotating pressure roller 6. If it is introduced between the image bearing surfaces upward,
The recording material P passes through the nip portion N together with the film 2, and the thermal energy of the heater 3 in contact with the back surface of the film at the nip portion N is applied to the recording material P via the film 2 to form the toner image T. Is fixed by heat.

As shown in FIG. 2, the film 2 preferably has a total thickness of 100 μm or less in order to reduce the heat capacity and improve the quick start property, and has heat resistance, strength and durability. Polyimide / PEEK / PES
A conductive layer 2-b serving as a primer is coated on the outer peripheral surface of the base layer 2-a such as PPS, and a release layer 2-c of substantially insulating PTFE, PFA, FEP or the like having excellent release properties is further formed thereon. The composite layer film coated with is used.

In the present embodiment, the outer peripheral surface of polyimide is coated with a primer in which carbon is dispersed, and P is coated on the primer.
The one coated with TFE was used. The outermost PTF
The primer is exposed without coating E only on the end on the anti-reference side. As shown in FIG. 2, an elastic conductive rubber contact 9 attached to the central shaft 7 of the pressure roller 6 is pressed against this portion at the fixing nip portion N so that the pressure roller central shaft 7 is grounded. ing.

In this case, the contact is always provided in the non-heated area on the side opposite to the reference in the case of the one side reference, so that the contact failure caused by the paper powder interposed between the film contact and the conductive rubber contact 9 is prevented. This is because the paper on the reference side is rubbed against the reference plate and the edges are likely to generate paper dust, and in small size paper the edges do not pass through the anti-reference side edge, so the anti-reference edge The reason is that the amount of paper powder attached is smaller than that on the reference side end.

By such a method, stable conduction can always be ensured and offset can be prevented.

<Embodiment 2> In the fixing device substantially similar to the above embodiment, the heater 3 is constructed as shown in FIG. In this heater 3, a through hole 13 is provided at the end of the heating element on the side opposite to the reference, an AC electrode 12 is provided on the back surface of the heater 3, and a DC electrode 11 for the temperature detecting element 10 is provided at the end of the reference side rear surface. In this way, the pattern in which the AC current of the heating element on the heater 3 flows is moved from the heating side of the heater 3 to the back side, and the contact is provided outside the heating element 4, so that the glass or film coated with the protective layer 5 is formed. Even if the pin 2 has a pinhole or is broken, the current to the heating element 4 is never grounded through the conductive rubber 9, and safety can be ensured.

At this time, the contact point to the film may be made of a metal brush or the like, and in this case, it is also effective for a short circuit due to the brush coming off or the like.

[0024]

As described above, in the heating device of the one-sided reference film heating system, the contact for grounding the film is provided at the end on the anti-reference side, so that a stable contact can be always secured. Therefore, it is possible to prevent the so-called fixing offset, which is caused by the adhesion of toner or paper powder to the film, which is caused by the charge-up of the film due to the contact failure.

Further, it is possible to avoid the risk that the current supplied to the heating element is grounded through the contacts due to pinholes or breakage of the film or the heater protection layer.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a fixing device according to first and second embodiments of the present invention.

FIG. 2 is a perspective view of a main part of the fixing device according to the first exemplary embodiment of the present invention.

FIG. 3 is a heating surface and a rear view of the heater according to the second embodiment of the present invention.

[Explanation of symbols]

1 ... Stay 2 ... Film 3 ... Heater 4 ... Heating Element 5 ... Protective Layer 6 ... Pressure Roller 7 ... Center Shaft 8 ... Roller Section 9 ... Conductive Rubber Contact 10 ... Temperature Sensing Element 11 ... DC Contact 12 ... AC Contact 13 ... Through hole

Claims (2)

[Claims] 1. A film is brought into contact with and slid on a fixedly supported heating body, and a material to be heated is brought into close contact with the surface of the film opposite to the heating body, and the film is moved and passed through the heating body position together with the film. A heating device for applying heat energy from a heating body through the film, wherein the electrical contact of the film is provided on the opposite reference side. 2. The heating device according to claim 1, wherein the contact is provided outside an end portion of the heating element on the heating element.