JP3232150B2 - Fixing heater - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing heater having a substrate, a resistance heating element layer provided on the substrate, and a temperature detecting element.

[0002]

2. Description of the Related Art Conventionally, an image heating and fixing apparatus has a heating roller which is maintained at a predetermined temperature and a pressure roller which has an elastic layer and is in pressure contact with the heating roller. There are various types of heat roller fixing systems in which a recording material carrying toner is heated while being nipped and conveyed.

However, this heat roller fixing method has a problem that it requires a large amount of electric power due to its large heat capacity and requires a long wait time until the temperature is raised to a predetermined temperature.

In order to solve such a problem, Japanese Patent Application Laid-Open Nos. 1-263679 and 2-15
Japanese Patent No. 7878 and the like have proposed a film heat fixing method in which a warm-up time is reduced by using a thermal head having a low heat capacity and a thin film which slides on the thermal head.

This heater has a resistor which generates heat when energized, and a ceramic substrate having good thermal conductivity on which the resistor is provided, and a detection output of a temperature detecting element for detecting a temperature of the substrate is constant. The current supply to the resistor is controlled.

[0006]

However, the above-mentioned conventional apparatus has the following problems. First, in the above-described film type fixing device, the temperature rise and fall of the heater is fast because the heat capacity of the heater is small, and the temperature ripple increases when the response time of the temperature detecting element is long. Further, if the contact state of the temperature detection element with the substrate is poor, not only normal temperature control is not performed, but also excessive temperature rise occurs. Further, in a fixing device using such a heater, fixing unevenness and gloss unevenness occur.

In order to solve this problem, a proposal has been made to provide a resistance heating layer and an electrode for taking out the output of a temperature detecting element on a substrate, and to bond the temperature detecting element on the substrate to speed up the response of the temperature detecting element. Has been made.

However, in this method, an electrode for taking out the output of the temperature detecting element is usually made of Ag, which is ionized by moisture in the air under a high temperature environment, and moves by an electric field between the electrodes, thereby causing a short circuit between the electrodes. This causes a phenomenon called migration. This problem can be prevented by using Au, Ag / Pd, Ag / Pt, or the like as the electrode material, but these materials are more expensive than Ag.

If the electrodes and the temperature detecting element are coated with a moisture-proof material such as silicone resin, epoxy resin or glass, migration can be similarly prevented. In this case, the adhesion of the temperature detecting element depends on the heating / cooling cycle of the heater. Peeled off due to thermal expansion and contraction of the moisture-proof coat. Unless the moisture-proof coating is placed only on the electrode and on the temperature sensing element, the temperature sensing element will not peel off,
Migration cannot be prevented.

[0010] It is also known that when a glass layer is provided between a substrate such as alumina or the like and an electrode to reduce the hygroscopicity of the substrate, migration is improved, but this is not a complete prevention measure.

An object of the present invention is to provide a fixing heater that solves the above-mentioned problems and that reliably prevents migration at low cost.

[0012]

According to the means and functions to an aspect of the present invention energization, the object includes a substrate, which is provided on the substrate
In a fixing heater having a resistance layer that generates heat, a chip-shaped temperature detecting element for detecting a temperature and an output from the temperature detecting element provided on the substrate are provided.
And a pair of electrodes for extending the temperature detecting element .
Both ends overlap on the pair of electrodes, and are achieved by filling an insulating material between the two electrodes and a region surrounded by the temperature sensing element and the substrate.

[0013]

[0014]

[0015]

According to the present invention, since the temperature sensing element is disposed via the pair of electrodes, the response of the temperature sensing element is fast, and the temperature sensing element is connected to the substrate by the pair of electrodes. Since the enclosed region is filled with an insulating material, migration of ions between the pair of electrodes is prevented, and migration does not occur.

[0016]

[0017]

[0018]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

<Embodiment 1> First, Embodiment 1 of the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional view of a heat fixing device using a heater according to a first embodiment of the present invention.

In FIG. 1, reference numeral 7 denotes an endless belt-shaped fixing film. The fixing film 7 is disposed with a left driving roller 8 and a right driven roller 9 fixedly supported below the rollers 8 and 9. It is stretched between the low-heat-capacity linear heater 1 provided.

The driven roller 9 also serves as a tension roller that applies tension in a direction in which the fixing film 7 is stretched outward. The fixing film 7 rotates at a predetermined peripheral speed in the clockwise direction as the driving roller 8 rotates clockwise. It is rotationally driven so as not to cause wrinkles, meandering and speed delay.

Reference numeral 10 denotes a pressure roller having a rubber elastic layer having good releasability such as silicone rubber as a pressure means,
The lower film portion of the endless belt-shaped fixing film 7 is sandwiched between the heater 1 and the lower surface of the heater 1, and the lower surface of the heater 1 is pressed against the lower surface of the heater 1 with a contact force of, for example, 4 to 7 kg / cm. Yes, the recording material 12 rotates counterclockwise in the forward direction in the transport direction.

The rotationally driven endless fixing film 7 is repeatedly provided for heating and fixing of the toner image, and therefore has excellent heat resistance, release properties and durability.
A thin film having a thickness of not more than μm, preferably not more than 40 μm is used. As an example, a polyimide (P
I), a single-layer film of a heat-resistant resin such as polyetherimide (PEI), polyether sulfone (PES), tetrafluoroethylene / perfluoroalkylvinyl ether copolymer resin (PFA), or a composite layer film, for example, 4 μm at least on the image contact surface side of a 20 μm thick film
For example, a release coating layer obtained by adding a conductive material to a fluororesin such as fluorinated ethylene resin (PTFE) or PAF and having a thickness of 10 μm is provided.

The heater 1 is a low-heat-capacity linear heater whose longitudinal direction extends in a direction intersecting with the film moving direction, and includes a substrate 2 having good thermal conductivity, a conductive resistance heating element layer 3, and a thermistor 503 serving as a temperature detecting element. .

The substrate 2 is an alumina substrate having heat resistance, electric insulation and low heat capacity, and is 1.0 mm thick, 10 mm wide and 2 mm long.
It is formed to be 40 mm.

The resistance heating element layer 3 is made of an electric resistance material such as Ta, silver palladium, ruthenium oxide or the like having a width of about 1.0 at substantially the center of the surface on the film sliding side of the substrate 2 along the longitudinal direction of the surface.
This is a linear or belt-shaped layer having a low heat capacity, which is provided by coating (screen printing or the like) on a mm.

Since the substrate surface of the heater 1 on which the resistance heating element layer 3 is provided is a sliding surface with the film 7,
It is preferable that the surface of the substrate including the resistance heating element layer 3 is protected by forming a slide protection layer such as Ta ₂ O ₅ .

The heater 1 as described above is provided on the side where the resistance heating element layer 3 is provided in the heating element accommodating groove 4a formed along the longitudinal direction of one surface of the horizontally long heat insulating heater holder 4. It is mounted with its surface outside, and is fixed and held by an adhesive 18. The holder 4 is fixedly supported by an adhesive 19 on the lower surface of a support 5 as a stationary member of the fixing device such that the heater 1 faces downward.

The heater holder 4 is made of, for example, a high heat resistant resin such as PPS (polyphenylene sulfide), PAI (polyamide imide), PI (polyimide), PEEK (polyether ether ketone), liquid crystal polymer, or these resins and ceramics. It is composed of a composite material with a metal or the like.

The heater 1 applies an AC voltage to the linear or belt-shaped resistance heating element layer 3 from both ends in the longitudinal direction to generate heat over the entire length of the resistance heating element layer. The temperature of the heater 1 is detected by the temperature detecting element 503, and the energization is controlled by a microcomputer based on the detected temperature so as to reach a predetermined temperature.

Further, in this embodiment, a front end / rear end sensor (not shown) of the sheet is provided in the fixing device on the upstream side of the fixing device A in the recording material conveying direction, and the sensor detects a sheet detection signal. The energization period for the heating element layer 3 is set to the sheet 1
2 is controlled only during the necessary period of passing through the fixing device A.

In the apparatus of the present embodiment as described above, the image forming apparatus (not shown) starts the image forming operation in response to the image forming start signal, and the unfixed powder toner image 11 is transferred onto the recording material 12. Is done. When the leading end of the recording material 12 is detected by the above-mentioned sensor (not shown) provided in the fixing device, the rotation of the fixing film 7 is started, and the recording material 12 is guided by the guide 16 to be heated by the heater. 1 enters a pressure contact portion (fixing nip portion) N between the pressure roller 1 and the pressure roller 10. Then, the fixing film 7 in which the surface of the unfixed toner image is moved.
The movable fixing film 7 passes while receiving a pinching pressure in an overlapping state with the movable fixing film 7 without causing surface deviation or wrinkling. As a result, the toner image bearing surface of the recording material 12 receives the heat of the heat generating layer 3 via the fixing film 7, and the toner image 11 is melted at a high temperature and softened and adhered to the recording material 12 surface.

Thereafter, when the recording material 12 passes through the fixing nip N and separates from the fixing film 7, the temperature of the molten toner at the time of the separation is still lower than the glass transition point (ring and ball type) of the toner. It is in a high temperature state.

However, while the toner Ta is separated from the fixing film 7 and guided by the paper ejection guide 17 to reach a paper ejection roller (not shown), the temperature of the toner Ta higher than the glass transition point naturally lowers (natural cooling). As a result, the temperature becomes lower than the glass transition point, and the solidification occurs.

Next, the structure of the heater in this embodiment will be described in detail with reference to FIG. FIG. 2 is an enlarged view of a thermistor mounting portion serving as a temperature detecting element on the back surface of the substrate.
As shown in FIG. 2, a pair of electrodes 120 made of Ag is provided on a surface of the substrate 2 made of a high thermal conductive ceramic such as alumina or AlN opposite to the surface on which the resistance heating element layer 3 is attached. The thermistor 503 is bonded on the electrode 120 with a conductive adhesive 504. The conductive adhesive 504 is obtained by dispersing Ag particles in epoxy, silicone, polyimide resin, glass, or the like.

The electrode 120 is disposed such that the two electrodes face each other with a predetermined gap. The gap and the area formed by the thermistor chip heat-sensitive portion 501 and the substrate 2
Filling with an insulating material 510 made of epoxy, silicone, polyimide, fluororesin, glass, or the like prevents migration of Ag ions between the electrodes 120 and prevents migration.

The presence of the insulating substance 510 improves the heat conduction from the substrate 2 to the thermistor 503, and improves the response of the thermistor 503. Further, by using an adhesive material for the insulating material 510, the adhesive strength of the thermistor 510 to the substrate 2 is increased, and the thermistor is less likely to be dropped when the heater is handled.

In the heater described above, the distance between the electrodes was set to 1.0 mm, and the voltage applied to the thermistor was set to 5 V.
Table 1 shows the results of examining the time for causing a short circuit due to migration in an environment of 80 ° C. and 95% RH.

[0039]

[Table 1]

As can be seen from Table 1, short-circuiting due to migration occurs within 1000 hours without an insulating substance, whereas short-circuiting does not occur even after 2000 hours with an insulating substance.

<Embodiment 2> Next, Embodiment 2 of the present invention will be described. In this embodiment, the electrode 120 of the heater shown in FIG.
And a thermistor 503 coated with a moisture-proof coating made of epoxy, polyimide, silicone, fluororesin, or the like. In this case, the thermistor 50 is formed by the insulating material 510.
3, the thermistor 503 does not come off due to the heating / cooling cycle of the heater.
The application of the moisture-proof coat was performed after applying the adhesive 504 and the insulating substance 510 on the electrode 120 and pressing and curing the thermistor 503.
After applying, the thermistor 503 is pressurized and cured, and then a low-viscosity fluid created by dissolving an insulating resin with a solvent or the like is applied or dropped near the thermistor 503, and a capillary phenomenon is applied to the gap between the thermistor 503 and the substrate 2. Inhale,
The moisture-proof coat and the insulating material layer 510 may be formed at the same time.

In this embodiment, Ag is used as the electrode material. However, there is no problem even if the electrode material is another material such as Au, Ag / Pt, Ag / Pd.

Third Embodiment Next, a third embodiment of the present invention will be described with reference to FIGS. The same parts as those in the first embodiment are denoted by the same reference numerals, and the description is omitted.

As shown in FIG.
This is a film-type fixing device similar to that described above, and its configuration and operation are almost the same as those of the first embodiment, but the configuration of the heater 1 is different as follows.

FIG. 4 is an enlarged view of the thermistor mounting portion on the back surface of the substrate in this embodiment. As shown in FIG. 4, a substrate 2 made of a high thermal conductive ceramic such as alumina or AlN is used.
A pair of electrodes 120 made of Ag are provided on the surface opposite to the surface on which the resistance heating element layer 3 is attached, and a thermistor 503 is provided on the electrodes 120 with a conductive adhesive 504. Glued. Conductive adhesive 504
Is obtained by dispersing Ag particles in epoxy, silicone, polyimide resin or the like.

In FIG. 5, the substrate 2 of the heater 1 is
Shows the state of adhesion. A hole 4b as shown in FIG. 6 is formed in the heater holder 4 so that the thermistor 503 does not contact the holder. When the hole 4b is bonded as shown in FIG. 5, the adhesive 18 seals the hole 4b, and the thermistor 503 and the electrode 120 disposed in the hole 4b and the bonding portion between the thermistor 503 and the electrode 120 are exposed to outside air. And not to touch.

As described above, by forming the thermistor output circuit system in an airtight structure and preventing moisture from entering, it becomes possible to prevent migration.

The adhesive 18 may be a simple elastic body having no adhesive property. This is because the heater 1 is always pressed from below by the pressing roller 10 as shown in FIG.
This is because the airtightness of the thermistor output system is maintained.

Further, a low humidity gas such as N ₂ may be introduced into the hole 4 b of the holder 4.

Fourth Embodiment Next, a fourth embodiment of the present invention will be described with reference to FIGS. In this embodiment, as shown in FIG. 7, a coat 150 made of an insulating material such as glass, epoxy, or polyimide resin is provided on the electrode 120. The electrode 120 is moisture-proof by this coat 150. Then, the thermistor 503 and the thermistor bonding portion are bonded to the holder 4 so as to be airtight by an adhesive 135,
The substrate 2 is bonded to the holder 4 with an adhesive 18 '.

Normally, it is difficult to adhere the entire back surface of the heater to the holder 4, and a gap is formed somewhere. In this case, it cannot be checked whether there is a gap. In FIG. 7, the electrode 120 is pre-coated, the lack of the coat 150 can be easily visually inspected, and the moisture protection is complete. After that, only by bonding the adhesive 135 between the substrate 2 and the holder 4, the thermistor circuit system can be made dampproof.

In FIG. 8, the vicinity of the thermistor 503 is filled with an elastic body 170 such as silicone rubber so as to maintain airtightness. The electrode 120 is moisture-proof by the coat 150, and can similarly prevent migration.

[0053]

As described above, according to the present invention,
In a heater having a substrate, a resistance heating element layer provided on the substrate, a temperature sensing element, and a pair of electrodes for extracting an output of the temperature sensing element, migration is performed by filling an insulating material between the electrodes. Can be prevented, the responsiveness of the thermistor can be improved, the adhesive strength of the thermistor can be increased, and the handling of the heater can be simplified.

[0054]

[0055]

[Brief description of the drawings]

FIG. 1 is a sectional view of a fixing device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a schematic configuration of a heater in the apparatus of FIG.

FIG. 3 is a sectional view of a fixing device according to a third embodiment of the present invention.

4 is a diagram showing a schematic configuration of a heater in the apparatus in FIG.

5 is a diagram showing a state in which the heater in the apparatus of FIG. 3 is attached to a support.

FIG. 6 is a view for explaining a concave portion of the support of FIG. 5;

FIG. 7 is a diagram illustrating a schematic configuration of a heater according to a fourth embodiment of the present invention.

FIG. 8 is a diagram showing a schematic configuration when a concave portion of a support is filled with an elastic body according to a fourth embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 heater 2 substrate 3 resistance heating element layer 4 support 4b hole (recess) 7 fixing film (film member) 10 pressure roller (pressure member) 120 electrode 503 thermistor (temperature detecting element) 510 insulating material

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G03G 13/20 G03G 15/20 H05B 3/20-3/38

Claims (3)

(57) [Claims] And 1. A substrate, a current provided on the substrate
In a fixing heater having a resistance layer that generates more heat, a chip-shaped temperature detecting element for detecting a temperature and an output from the temperature detecting element provided on the substrate are taken out.
And a pair of electrodes of Sutame, across <br/> overlaps on the pair of electrodes, insulating the region surrounded by the electrodes between the above temperature sensing element and the substrate of the temperature detecting element A fixing heater characterized by being filled with a substance. 2. The fixing heater according to claim 1, wherein the insulating material is an adhesive . 3. The temperature detecting element is provided with a moisture-proof coating.
Fixing heater <br/> data according to claim 2, characterized in that they are.