JPH0380278A - Fixing device - Google Patents

Abstract

PURPOSE:To maintain stable performance by providing an electrode for supplying power to the resistance having element of a direct heating type roller which has the resistance heating element in or near a surface layer out of a range where a mold release agent for the roller is applied. CONSTITUTION:The heating roller is obtained by forming a 1st insulating layer 2, a resistance heating layer 3, a 2nd insulating layer 4 and a mold-released layer 5 on a core bar 1 in order. The electrode part 7 on the roller side which is provided on both ends in order to supply the power to the resistance having layer 3 has a shape which is swollen from the surface of the layer 5 to the outside of a radius and is disposed out of the range where the mold release agent is applied, shown by W in figure. Therefore, the mold release agent does not reach the contact part of the electrode P on a main body side in contact with the electrode part 7 on the roller side. Thus, the mold release agent does not reach the electrode and stable heating is always kept.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fixing device in an image forming apparatus such as an electrophotographic copying machine.

[Prior Art] Conventionally, various fixing methods have been proposed and implemented in general image forming apparatuses such as electrophotographic copying machines, but currently, the thermal fixing method is the mainstream. The most representative method is the heat roller fixing method.
At least one of the pair of rollers is provided with a heat source.

As an example of such a heat roller fixing method, a cylindrical fixing roller has a heat generation source such as a halogen heater in its interior space, and an elastic layer made of rubber or the like is formed on the surface layer. It contacts the pressure roller as a pair with an appropriate nip width (circumferential length), and is rotated by an appropriate drive means. The transfer material having an unfixed image is fixed by heat and pressure when it passes between the pair of rollers. As described above, the heat roller method is widely used because the fixing roller having a heat source directly contacts the transfer material and heats and fixes it, so it has very high thermal efficiency and can be made compact. Also, during operation, the surface of the roller is maintained at a nearly constant temperature by detecting the temperature of the surface of the roller, which comes into contact with the roller. It also has the disadvantage that the time during which operation is not possible, the so-called standby time, becomes long until heat is transferred from am to the roller surface and the surface reaches a predetermined temperature.

Therefore, in recent years, a fixing device using a so-called resistance heating roller having a layered M# section on or near the surface of the fixing roller has been proposed. With this method, compared to the case where a heat source is provided separately from the roller body as described above, there is no need to raise the temperature of the roller itself and the amount of heat loss can be reduced, so it is possible to heat the fixing roller efficiently. It is also possible to shorten the above waiting time.

Generally, a roller having this resistance heating element has a first insulating layer 2, a resistance heating element layer 3 on a core bar 1, as shown in FIG.
, the second insulating layer 4, and the release layer 5 are formed in this order. Power is supplied to the resistance heating element layer 3 by bringing the main body side electrode P connected to the power source into contact with the roller side electrode portion 7 exposed on the roller surface on both sides of the resistance heating element layer 3. .

In addition to the electrodes, a release agent applying roller 1O is brought into contact with the roller surface for the purpose of applying a release agent for preventing offset to the surface of the roller.

[Section B to be solved by the invention] When performing fixing with the device configuration as described above, there is a roller-side electrode 7 on the extended surface of the roller surface, and the release agent application roller 1 is applied to the area of the electrode 7. ( ), the mold release agent enters the contact point between the main body side electrode P and the roller side electrode part 7, causing a contact failure, and the heat generation of the resistance heating element layer 3 becomes unstable, causing the temperature of the roll surface to rise. There was a problem in that it was difficult to maintain stability at all times.

The present invention solves this problem and provides a fixing device that can always maintain stable heat generation without the release agent reaching the electrodes even if the release agent is applied to the heating roller having a resistive heating element. The purpose is to provide.

[Means for Solving the Problems] According to the present invention, the above object is achieved by: In a fixing device having a pair of rollers that are rotated in pressure contact while the surfaces thereof are coated with a release agent, at least one of the rollers is in the vicinity of the surface layer. It has a resistance heating element, and an electrode provided on the axial end surface for power supply to the resistance heating element is provided in the axial direction outside the range of application of the release agent to the roller. This is achieved by

[Function] In the present invention as described above, the electrode is outside the application range of the mold release agent, and the S-type agent does not reach the electrode. Also, between the electrode and the above coating range limit line.

If the S-type agent entry prevention means is provided, even if the release agent migrates toward the electrode under some circumstances, it will be blocked by the release agent entry prevention means and will not reach the electrode.

[Example] Hereinafter, the present invention will be described in detail based on the accompanying drawings.

FIG. 1 is a sectional view of a first embodiment that best represents the features of the present invention. Incidentally, in this figure, parts common to those of the conventional example shown in FIG. 4 are given the same reference numerals. In FIG. 1, the heating roller has a first insulating layer 2.
A resistive heating element layer 3, a second insulating layer 4, and a release layer 5 are formed in this order. The roller-side electrode portions 7 provided at both ends for supplying power to the resistive heating element layer 3 have a shape that bulges radially outward from the surface of the release layer 5, and is indicated by W in the figure. The mold release agent is disposed outside the shown mold release agent application range, so that the mold release agent does not reach the contact portion between the roller side electrode portion 7 and the main body side electrode P that comes into contact with it.

Further, the inner surface 15 in the axial direction of the electrode part 7 is used as a means for preventing entry of the mold release agent so as to have a low surface energy so that the mold release agent does not reach the electrode contact point due to capillary action, centrifugal force, etc. A Teflon coating is applied to increase the effect of preventing mold release agent from entering.

Note that the roller side contact portion 7 is made of the same material as the resistance heating layer or a conductive material. The same applies to other embodiments below. Further, the release agent application range W indicates its maximum range. Furthermore, the second insulating layer 4 may also serve as the release layer 5. The same applies to these and other embodiments below.

FIG. 2 is a sectional view of a heating roller according to a second embodiment of the present invention. In this embodiment, 1Ily! to the electrode contact portion! ! As a means for preventing the entry of a releasing agent, a circumferential groove 8 for preventing the entry of a mold release agent is provided in the roller side electrode portion 7. The release agent application range W is located inside the release agent entry prevention circumferential grooves 8, 8 at both ends of the roller,
Even if the mold release agent oozes out toward both ends and exceeds the above range W, the mold release agent entry preventing circumferential groove 8 prevents the mold release agent from entering the electrode contact portion.

In this case as well, the effect will be further enhanced if the electrode side wall surface of the mold release agent intrusion prevention circumferential groove 8 is coated with Teflon or the like to have a low surface energy.

FIG. 3 is a sectional view of a heating roller according to a third embodiment of the present invention. In this embodiment, as a means for preventing the release agent from entering the electrode contact portion, a release agent entry preventing protrusion 9 is provided continuously in the circumferential direction on the roller side electrode portion 7. The release agent intrusion preventing protrusion 9 is.

It may be constructed integrally with the roller-side electrode section 7, or it may be constructed by adding an annular member to the electrode section 7 afterwards. In that case, the annular member need not be electrically conductive. The mold release agent application range W is located inside the mold release agent entry preventing projections 9, 9 at both ends, and even if the mold release agent seeps out toward both ends and exceeds this application range W, the mold release agent is Protrusions to prevent drug entry! 9 prevents it from entering the electrode contact portion. In this case, only the inner surface of the mold release agent intrusion prevention protrusion 9 may be treated to have a low surface energy, or the entire surface may be treated to reduce the surface energy.
The protrusion portion 9 itself may be constructed from a separate member that has low surface energy.

[Effects of the Invention] As explained above, the present invention provides an electrode for supplying power to the resistance heating element of a direct heating roller having the resistance heating element on or near the surface layer.

By installing the release agent outside the roller's application range, we have prevented the release agent from reaching the electrode area, which prevents contact failures and current conduction failures caused by the release agent entering the electrode contact area, resulting in stable performance. This has the effect of making it possible to have mixed performance.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a device according to a first embodiment of the present invention, Fig. 2 is a sectional view of a device of a second embodiment, Fig. 3 is a sectional view of a device of a third embodiment, and Fig. 4 is a sectional view of a conventional device. FIG. 3... Resistance heating element (layer) 7... Electrode (roller side electrode part) 8.9. Is・
...Mold release agent intrusion prevention means (8...mold release agent intrusion prevention circumferential groove, 9 ... mold release agent intrusion prevention protrusion,
15-・・・Inner surface) W・・・Release agent application range

Claims (3)

[Claims] (1) In a fixing device having a pair of rollers that are rotated in pressure contact while a release agent is applied to the surface of the fixing device, at least one of the rollers has a resistance heating element near the surface layer, and the roller is used to supply power to the resistance heating element. A fixing device characterized in that an electrode provided on an axial end surface of the roller is provided outside a release agent application range to the roller in the axial direction. (2) The fixing device according to claim 1, wherein the roller having the resistance heating element is provided with a release agent intrusion prevention means between the release agent application range limit line and the electrode. (3) The fixing device according to claim 2, wherein the release agent intrusion prevention means includes at least a portion of the roller surface subjected to low surface energy treatment.