JPH05135849A - Heater and fixing device - Google Patents

Abstract

PURPOSE:To firmly bond a thermister chip to a board as well as to enhance the responsiveness of a temperature detecting element by bonding the temperature detecting element to a thermister conductive board with metallic paste. CONSTITUTION:When metallic paste is filled in between a heater board 2 and a thermister board 105 in such a way as to be, for example, less than 500mum in thickness so as to be sintered at termperature equal to or more than 600 deg.C, solvent and organic binder are burnt out first roughly at 400 deg.C, non-organic binder is fused at 600 deg.C while paste reacts with a ceramic substrate acting as a heater and a thermister substrate or penetrates therein, so that bonding is completed. Metallic powder and the like such as Au, Pt, Cu, Ni and the like is included in the paste used for bonding so that it is conductive. Thus, a thermister chip 102 can firmly be bonded onto the heater substrate by bonding the thermister chip 102 on the substrate with metallic paste. Furthermore, since a metallic paste layer 107 is high in thermal conductivity, thermal contact resistance between the heater and a thermister is almost eliminated.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Conventionally, an image heating and fixing device has a heating roller which is maintained at a predetermined temperature and a pressure roller which has an elastic layer and is brought into pressure contact with the heating roller. A heat roller fixing method is often used in which a recording material on which an attached toner image is formed is heated while being nipped and conveyed.

However, this heat roller fixing method requires a large amount of electric power because of its large heat capacity, and it takes a wait time until the temperature rises to a predetermined temperature.

To solve such a problem, the applicant has previously disclosed Japanese Patent Application Laid-Open No. 1-263679 and Japanese Patent Application Laid-Open No. 2-263679.
A heat fixing device using a thermal heater having a small heat capacity and a thin film was previously proposed in Japanese Patent No. 157878.

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

[0006]

However, since the heater has a small heat capacity, the temperature rise and fall of the heater is fast, and if the response time of the temperature detecting element is long, the temperature ripple becomes large.

If the contact state of the temperature detecting 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, uneven fixing and uneven gloss occur.

[0009]

The present invention which solves the above problems provides a heater having a good heat conductive substrate, and a resistance heating layer and a temperature detecting element provided on the good heat conductive substrate. The temperature sensing element is adhered to the good thermal conductive substrate with a metal paste, the good thermal conductive substrate, and a resistance heating layer provided on the good thermal conductive substrate. And a temperature detecting element, and a film that slides on the heater,
In a fixing device that fixes an unfixed image on a recording material through a film with heat from a heater whose temperature is controlled so that the detection output of the temperature detection element is constant, the temperature detection element uses a metal paste It is characterized by being bonded to a conductive substrate.

[0010]

FIG. 1 is a sectional view of a heat fixing device using a heater according to an embodiment of the present invention.

Reference numeral 7 denotes an endless belt-shaped fixing film, which has a driving roller 8 on the left side, a driven roller 9 on the right side, and
The low heat capacity linear heater 1 fixedly supported below the rollers 8 and 9 and parallel to each other, the three members 8
・ It is suspended between 9 and 1.

The driven roller 9 also serves as a tension roller for the endless belt-shaped fixing film 7, and the fixing film 7 has a predetermined peripheral speed in the clockwise direction when the driving roller 8 is driven to rotate in the clockwise direction. It is driven to rotate without any speed delay.

Reference numeral 10 is a pressure roller as a pressure member having a rubber elastic layer with good releasability such as silicon rubber,
The lower film portion of the endless belt-shaped fixing film 7 is sandwiched between the heating member 1 and the lower surface of the heater 1 and is pressed against the lower surface of the heater 1 by a biasing means with a contact pressure of, for example, 4 to 7 kg. Therefore, the transfer material sheet 12 as a recording material rotates in the counterclockwise direction in the forward direction.

Since the endless belt-shaped fixing film 7 which is rotationally driven is repeatedly subjected to heat fixing of the toner image, it is excellent in heat resistance, releasability and durability, and is generally 1
A thin film having a thickness of 00 μm or less, preferably 40 μm or less is used. For example, polyimide, (PI), polyetherimide (PEI), PES, PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin)
A heat-resistant resin single-layer film or a composite layer film, for example, a 20 μm-thick film at least on the image-contacting surface side, a release coating layer in which a conductive material is added to a fluororesin such as PTFE (tetrafluoroethylene resin) / PAF Is applied to have a thickness of 10 μm.

The heater 1 is a low-heat-capacity linear heater having a longitudinal direction in the direction crossing the film moving direction, and comprises a substrate 2 having good thermal conductivity, an energization resistance heating element layer 3, a thermistor 102 which is a temperature detecting element, and the like. ..

The substrate 2 has heat resistance, electrical insulation, and low heat capacity. For example, the thickness is 1.0 mm, the width is 10 mm, and the length is 2.
It is a 40 mm alumina substrate.

In the energization heating element layer 3, one surface of the substrate 2 is used as a film sliding side surface, and an electric resistance material such as Ta ₂ N and silver palladium is formed along the longitudinal direction at a substantially central portion of the surface. ．
It is a linear or band-shaped low heat capacity layer provided by coating (screen printing, etc.) to 0 mm.

Thus, the heater 1 is provided on one side surface of the horizontally elongated heater holder 4 along the longitudinal direction of the heater, and the side where the energization heating element layer 3 is provided in the heating element accommodating groove 4a. The surface of the holder 4 is fitted into the holder 4 and is fixedly held by the holder 4 with the adhesive 18, and the holder 4 is fixed and supported by the adhesive 19 on the lower surface of the support 5 as a stationary member of the fixing device with the heater 1 facing downward. There is.

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

The heater 1 energizes the resistance heating element layer 3 in the form of a line or a strip from both longitudinal ends thereof to cause the resistance heating element layer to generate heat over its entire length. The energization is a pulsed waveform with a cycle of 20 msec of DC100V, and the energization control that gives a pulse (driving pulse) according to the desired temperature and energy emission amount controlled by the temperature detection element 6 and the microcomputer by changing its pulse width. It has a circuit configuration. The approximate pulse width is 0.5 to 5 msec.

In this embodiment, a sheet front and rear end detection sensor (not shown) is provided on the upstream side of the fixing device A in the transfer material sheet conveying direction, and a heating element is generated by the sheet detection signal of the sensor. The energization period for the layer 3 is controlled only during the required period in which the sheet 12 is passing through the fixing device A.

An image forming mechanism (not shown) performs an image forming operation in response to an image forming start signal and is conveyed to the fixing device A. The transfer material sheet 1 carrying an unfixed powder toner image 11 on its upper surface.
When the leading edge of 2 is detected by the above-mentioned sensor (not shown) disposed near the fixing device, the fixing film 7 starts to rotate, and the transfer material sheet 12 is guided by the guide 16 to guide the heater 1 and the pressure roller. Pressure contact part N with 10 (fixing nip part)
Between the fixing film 7 and the pressure roller 10 of
The unfixed toner image surface is in close contact with the lower surface of the fixing film 7 in the surface moving state, and the fixing nip portion between the heater 1 and the pressure roller 10 is overlapped with the moving fixing film 7 without causing surface deviation or wrinkling. N is passed while receiving a clamping pressure.

The toner image bearing surface of the sheet 12 receives the heat of the heating element layer 3 of the heater 1 via the fixing film 7 while passing through the fixing nip portion N in a state of pressing contact with the fixing film surface, so that the toner image is formed. 11 melts at high temperature and sheet 12
Softens and adheres to the surface.

In the case of the apparatus of this example, the sheet 12 as a recording material and the fixing film 7 are separated from each other by the sheet 12 at the fixing nip portion N.
It is done at the time of passing through.

The temperature of the toner at this separation point is higher than the glass transition point (ring and ball type).

The sheet 12 separated from the fixing film 7 is guided by the guide 17 and the temperature of the toner having a temperature higher than the glass transition point is naturally lowered (naturally cooled) while reaching the discharge roller, and the temperature is below the glass transition point. Then, the sheet 12 is solidified and the image-fixed sheet 12 is output.

Since the substrate surface of the heater 1 on the side on which the energization heating element layer 3 is provided is a sliding surface with the film 7, the substrate surface including the energization heating element layer 3 is, for example, Ta ₂ O ₅ or the like. It is preferable to protect the surface by forming a sliding protection layer of.

FIG. 2 is a partially enlarged view of the mounting portion of the thermistor on the back surface of the good thermal conductive substrate.

On the surface of the substrate 2 made of a ceramic having high thermal conductivity such as alumina or AlN, which is opposite to the resistance heating element 3,
A pair of electrodes 100 made of a metal such as Ag, Ag / Pd, Ag / Pt, Pt, Au is provided, and a thermistor chip 102 which is a temperature detecting element is bonded between them.

The thermistor chip 102 comprises a ceramic substrate 105 having a high thermal conductivity such as alumina or AlN having a thickness of 1 mm or less, and Fe ₃ O ₄ film having a thickness of 10 μm or less formed on the ceramic substrate 105 by sputtering or the like. M
gCr ₂ O ₄ , MgAl ₂ O ₄ , NiO, Mn ₂ O ₃ , Co ₂
It is composed of a metal oxide film 106 such as O ₃ and electrodes 103 provided at both ends of this metal oxide film, and has a negative temperature coefficient.

A wire 104 made of a metal such as Au extends from the electrode 103 of the thermistor chip 102 and is connected to the electrode 100 on the heater substrate 2.

Although not shown, the thermistor chip 102 and the wire 104 are protected by a protective layer made of glass, heat-resistant rubber made of silicon rubber or the like in order to prevent breakage due to impact from the outside.

The substrate 105 of the thermistor chip 102 is adhered to the heater substrate 2 by the metal paste layer 107.

The metal paste used for this bonding is at least Au, Pt, Au, Cu, for imparting conductivity.
Ni, PdO, Pd, Bi ₂ Ru ₂ O ₇ , RuO ₂ , W, M
o, etc. 325 mesh pass (American style) or less (about 43 μm
(Below) metal powder, metal oxide fine conductive powder, and glass such as boron silicate or aluminum silicate for adhering to the ceramic substrate, on a glass such as Bi ₂ O ₃ , PbO, ZnO, MgO, C.
Inorganic binder powder mixed with additives such as aO and CuO,
A mixture of an organic binder such as ethyl cellulose for imparting paste-like fluidity and a high boiling point solvent such as terpineol or butyl carbitol is usually called a thick film paste.

This metal paste is sandwiched between the heater substrate 2 and the thermistor substrate 105 with a thickness of 500 μm or less.
When fired at a temperature of 00 ° C. or higher, the solvent and the organic binder are burned off at about 400 ° C., the inorganic binder is melted at a temperature of 600 ° C. or higher, and reacts or permeates with the ceramic substrate, which is the heater and thermistor substrate, to complete the adhesion.

The output of the thermistor is taken out by connecting a connector (not shown) to the heater end E portion.

By thus bonding the thermistor chip 102 with the metal paste, the thermistor chip 10
2 can be very firmly adhered to the heater substrate. Furthermore, since the metal paste layer 107 has high heat conductivity, the thermal contact resistance between the heater and the thermistor chip is almost eliminated, and the response of the thermistor can be improved.

If the area of the metal paste layer 107 is made larger than the size of the thermistor chip 102, the metal paste layer 107 collects heat, so that the response of the thermistor 102 can be further enhanced.

FIG. 3 is a partially enlarged view of a heater according to another embodiment of the present invention.

The thermistor chip 111 is made of Fe ₃ O ₄ , M.
gCr ₂ O ₄ , MgAl ₂ O ₄ , NiO, Mn ₂ O ₃ , Co ₂
It is composed of a pair of electrodes 112a and 112b made of the above-mentioned metal paste, which faces a block 113 which is a solid solution of a metal oxide such as O ₃ or the like and which is mixed and fired and cut into a size of 1 mm square or less.

The electrode 110 is an electrode made by firing the above-mentioned metal paste. After the electrode pattern is printed on the heater substrate 2 with a metal paste to a thickness of 500 μm or less, the thermistor chip 111 is placed and fired at 600 ° C. or higher to form the electrode 110, the thermistor chip electrode 112 b and the electrode 1.
10 bonds are completed. After that, the electrode 112a and the electrode 100 are connected by a wire such as Au.

In this case, since the electrode 110 collects heat, the response of the thermistor becomes faster.

FIG. 4 is a partially enlarged view of a heater according to still another embodiment of the present invention.

In this embodiment, the metal oxide film side of the thin film thermistor used in the embodiment of FIG. 2 is bonded to the heater substrate side by the metal paste 103 which also serves as an electrode.

The electrode 120 is made by firing the above-mentioned metal paste. Before the electrode 120 is fired, the thermistor chip 102 is placed on the unfired electrode 120 and fired at the same time, whereby the adhesion between the thermistor electrode 103 and the electrode 120 is completed. Adhesion between the metal pastes is performed by melting and permeating the inorganic binders.

It is needless to say that after the electrode 120 is fired, the metal paste may be applied again to the thermistor contact portion of the electrode 120, the thermistor 102 may be placed and fired to bond them.

In the present embodiment, the heat of the heater substrate is transmitted to the film only by the electrodes without passing through the thermistor substrate, so that the response of the thermistor 102 can be further enhanced.

Further, as the material of the thermistor substrate 105, a material having low heat conduction, for example, glass is used, or the substrate 10 is used.
It is possible to increase the thickness of 5 to increase the strength of the thermistor chip.

Further, in the present embodiment, the thermistor can be attached to the heater very easily without requiring wire bonding.

As described above, when the heater substrate and the thermistor are bonded using the metal paste, the resistance to the heat cycle becomes extremely strong. For example, when the thermistor electrode 103 and the heater electrode 120 are soldered with Sn / Pb eutectic solder having a melting point of 300 ° C. or higher in place of the metal paste of the embodiment of FIG. While it peels off within 10,000 times, it cannot peel off more than 100,000 times if a metal paste is used as in this embodiment.

[0051]

As described above, according to the present invention, the temperature detecting element can be firmly adhered to the substrate without floating or peeling, and the responsiveness of the temperature detecting element can be improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a fixing device according to an exemplary embodiment of the present invention.

FIG. 2 is a partially enlarged view of the heater according to the embodiment of the present invention.

FIG. 3 is a partial enlarged view of a heater according to another embodiment of the present invention.

FIG. 4 is a partial enlarged view of a heater according to still another embodiment of the present invention.

[Explanation of symbols]

 1 Heater 2 Heater Substrate 3 Resistance Heating Layer 4 Holders 102, 111 Thermistor 105 Thermistor Substrate

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yoji Tomoyuki 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Daizo Fukuzawa 3-30-3 Shimomaruko, Ota-ku, Tokyo In Canon Inc. (72) Inventor Shunji Nakamura 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (6)

[Claims] 1. A heater having a good thermal conductive substrate, a resistance heating layer and a temperature detecting element provided on the good thermal conductive substrate, wherein the temperature detecting element is made of a metal paste to provide the good thermal conductivity. A heater characterized by being bonded to a substrate. 2. The heater according to claim 1, wherein the detection output of the temperature detecting element is taken out from the metal paste. 3. The heater according to claim 1, wherein the good heat conductive substrate is made of ceramics. 4. A heater having a good heat conductive substrate, a resistance heating layer provided on the good heat conductive substrate, and a temperature detecting element, and a film sliding on the heater, In a fixing device for fixing an unfixed image on a recording material through a film by heat from a heater whose temperature is controlled so that the detection output of the temperature detecting element becomes constant, A fixing device characterized by being adhered to a conductive substrate. 5. The fixing device according to claim 4, wherein the detection output of the temperature detecting element is extracted from the metal paste. 6. The heater according to claim 4, wherein the good heat conductive substrate is made of ceramics.