JP2009026714A - Plate heater, heating device, and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reliably detect a temperature for stopping runaway even when a temperature sensor has a lower detection level. <P>SOLUTION: Heat resistances 12, 13 each using an Ag-Pd allow as a main component are formed in parallel to the longitudinal direction of a long and flat ceramic substrate 11. Conducting electrodes 14, 15 are connected to the one-side ends of the heat resistances 12, 13, and a connection pattern 18 is connected to the other-side ends thereof. Thus, the heat resistances 12, 13 are connected in series to each other. At a longitudinal middle portion between the heat resistances 12, 13, the heat resistances 12, 13 are connected to each other via a temperature controller 21 having a negative resistance temperature coefficient. An overcoat layer 22 is formed on the heat resistances 12, 13 and the temperature controller 21. A thermistor 26 is mounted at a position opposite to the temperature controller 21 across the ceramic substrate 11. A current is passed through the connection pattern 18 in the normally heated condition of the heat resistances 12, 13 and a current is passed through the temperature controller 21 in the abnormally heated condition so that the abnormally heated condition can be detected when the thermistor 26 has a lower detection level. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a plate heater used in small equipment such as information equipment, home appliances and manufacturing equipment, and a heating device such as a printer, a copying machine, a facsimile, a rewritable card reader / writer, and the like, on which the plate heater is mounted, and The present invention relates to an image forming apparatus using the heating device.

In a conventional plate heater, a plurality of heating resistors are formed in the longitudinal direction of a strip-shaped ceramic substrate, and one end of each of the heating resistors in the same direction is provided with a power supply electrode, and the other end is provided via a conductive portion. Connected. In the heat generating resistor, taking into consideration that heat is taken away by the conductive portion, a restricting portion is formed in the heat generating resistor in the vicinity of the conductive portion to increase the resistance value, and the temperature of the restricting portion is increased. (For example, Patent Document 1)
JP 2006-91449 A

  In the technique of Patent Document 1 described above, when the detection level of the temperature sensor decreases, the temperature of the entire heater increases due to runaway without temperature control, and before the temperature sensor installed at the center of the heater operates. In addition, there is a problem that the heater is damaged due to cracking of the heater substrate or disconnection of the heater circuit.

  An object of the present invention is to provide a plate heater that reliably operates the temperature sensor during a heater runaway to prevent damage even when the detection level of the temperature sensor is lowered, a heating device using the plate heater, An object of the present invention is to provide an image forming apparatus using the apparatus.

  In order to solve the above-described problems, a plate heater of the present invention includes a long flat ceramic substrate, first and second heating resistors formed in the longitudinal direction of one surface of the ceramic substrate, The first and second heating resistors are connected to one end of the first and second heating resistors, respectively, and the other ends of the first and second heating resistors are connected to the first and second electrodes formed to supply power. The first and second heat generating resistors are connected to the connection pattern for connecting the first and second heat generating resistors in series and the longitudinal intermediate portion of the first and second heat generating resistors. A temperature control body having a negative resistance temperature coefficient connecting the bodies, the first and second heating resistors, an overcoat layer covering the temperature control body, and the ceramic substrate on which the temperature control body is formed. Temperature sensor mounted on the opposite side Characterized by comprising a chromatography, a.

  According to this invention, even when the detection level of the temperature sensor decreases and the heater runs away, the temperature sensor is reliably detected to stop the runaway, thereby preventing problems such as breakage of the plate heater. It becomes possible.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  FIG. 1A is a front view, FIG. 1B is a rear view of FIG. 1A, and FIG. 2 is a diagram for explaining one embodiment of the plate heater of the present invention. FIG.

  In FIG. 1 and FIG. 2, reference numeral 11 denotes a highly heat-resistant strip-shaped ceramic substrate which is a high-rigidity base material having electrical insulation properties such as a heat-resistant and electrically insulating material such as aluminum oxide, aluminum nitride, and silicon nitride. . The ceramic substrate 11 has dimensions of, for example, a thickness of 1 mm, a width of 10 mm, and a length of about 280 mm.

  12 and 13 are silver-based materials such as silver (Ag) / palladium (Pd) formed in parallel along the longitudinal direction of the surface side of the ceramic substrate 11, and resistor pastes such as ruthenium-based and carbon-based materials. Is a belt-shaped heating resistor made of a thick film having a predetermined resistance value. The heating resistors 12 and 13 have dimensions of, for example, a thickness of 10 μm, a width of 2.5 mm, and a length of about 226 mm.

  Reference numerals 14 and 15 denote power feeding electrodes formed adjacent to one side of the ceramic substrate 11 in the non-contact state. The electrode 14 is integrally formed with the other end of the connection pattern 16 made of a good conductor film mainly composed of an Ag / Pd alloy or the like formed by layering one end on one end of the heating resistor 12. The electrode 15 is integrally formed with the other end of the connection pattern 17 made of a good conductor film mainly composed of an Ag / Pd alloy or the like formed by layering one end on one end of the heating resistor 13. Yes.

  The other ends of the heating resistors 12 and 13 are connected using a connection pattern 18 formed of the same material and means as the connection patterns 16 and 17. With this connection, the heating resistors 12 and 13 are connected in series between the electrodes 14 and 15. The portions of the heating resistors 12 and 13 connected to the connection pattern 18 are formed with narrowing portions 19 and 20 having a narrow width in the length L section.

  In addition, a conductive temperature control body 21 having one end connected to the heat generating resistor 12 and the other end connected to the heat generating resistor 13 is formed at an intermediate portion in the longitudinal direction of the heat generating resistors 12 and 13. The temperature control body 21 has a negative resistance temperature coefficient as shown in FIG. As a material having a negative temperature coefficient of resistance, for example, graphite can be considered.

  22 is formed of a glass layer or a polyimide layer by thick film printing, for example, on the heating resistors 12 and 13 and the connection patterns 16 and 17 with the electrodes 14 and 15 left, and is electrically, mechanically and chemically formed. An overcoat layer that provides protection.

  On the back side of the ceramic substrate 11 on which the heating resistors 12 and 13 are formed, as shown in FIG. 1B, terminal portions 23 and 24 are located at positions facing the electrodes 14 and 15 with the ceramic substrate 11 interposed therebetween. Are formed adjacent to each other in a non-contact state. The terminal portions 23 and 24 are made of the same material as the electrodes 14 and 15 by the same means. The terminal portion 23 is connected to one end of a thermistor 26 which is a kind of temperature sensor at a position on the back surface side where the temperature control body 21 is formed via a wiring pattern 25 which is integrally formed and fixed to the ceramic substrate 11. The terminal portion 24 is connected to the other end of the thermistor 26 through a wiring pattern 27 that is integrally formed and fixed to the ceramic substrate 11. The thermistor 26 and the wiring patterns 25 and 27 are electrically connected using, for example, a conductive adhesive.

  The thermistor 26 uses an electric resistor having a large negative resistance temperature coefficient in the temperature sensing portion, and the heat value is greatly reduced when the temperature rises, and the temperature is converted into a large or small resistance value. It is a temperature sensor consisting of elements.

  When the electrodes 14 and 15 are energized, the heating resistors 12 and 13 connected in series between the electrodes 14 and 15 generate heat. The connection pattern 18 tries to remove heat from the heating resistors 12 and 13 as indicated by a broken line indicated by an arrow a 'in FIG. However, since the resistance values of the heating resistors 12 and 13 of the throttle portions 19 and 20 are increased, the amount of heat that is deprived by the temperature detection sensor is increased, and the deprived amount of heat is earned, so that the temperature distribution characteristic a in FIG. As can be seen, it is possible to obtain a uniform temperature distribution in the heated material conveyance region.

Here, temperature adjustment based on temperature detection of the thermistor 26 will be described with reference to the circuit configuration of FIG.
That is, when the commercial power source 51 is energized to the electrodes 14 and 15 of the plate heater 100 shown in FIG. 1 via the control unit 53 connected to the control terminal of the temperature control circuit 52, the heating resistors connected in series are connected. 12 and 13 are energized to generate heat. As the heating resistors 12 and 13 generate heat, the temperature of the ceramic substrate 11 also rises. This heat is transmitted to the temperature sensing part of the thermistor 26 attached to the back side of the ceramic substrate 11 and changes the resistance value of the temperature sensing part. A change in the resistance value of the thermistor 26 is output and input to the temperature control circuit 52 to determine whether the temperature is at the set temperature. When the temperature is lower than the set temperature, an ON signal is output to the control unit 53, and when the temperature is higher than the set temperature, an OFF signal is output to the control unit 53.

  Thus, the temperature of the heating resistors 12 and 13 is adjusted by controlling the power applied to the heating resistors 12 and 13. Although the temperature control circuit 52 has been described with respect to the on / off control of the control unit 53, temperature adjustment by a pulse width modulation control method or the like may be used.

  When the plate heater 100 is supplied with electric power to the electrodes 14 and 15, current flows through the heating resistors 12 and 13, respectively, and the heating resistors 12 and 13 exhibit a substantially uniform heating temperature distribution in the longitudinal direction. become. In this embodiment, for example, when the resistance value of the heating resistors 12 and 13 is 25Ω and a voltage of 100 V is applied, a current of 4 A flows and a heating value of 400 W can be obtained.

  Normally, as described above, the thermistor 26 provided on the back side of the ceramic substrate 11 detects the temperature of the plate heater 100 and controls the control unit 53 on / off through the temperature control circuit 52 to control it to a predetermined temperature. Yes.

  By the way, since the resistance value of the temperature control body 21 is larger than the resistance value of the connection pattern 18 in the folded portion of the heating resistors 12 and 13, it passes through the connection pattern 18 during normal temperature control.

  However, when the temperature detection level of the thermistor 26 changes and control is performed at a higher temperature than before, the entire temperature distribution of the temperature distribution characteristic a in FIG. 4 rises and runs away. At this time, since the temperature control body 21 has a negative resistance temperature coefficient, the resistance value decreases. The current flowing through the connection pattern 18 flows through the temperature control body 21 to generate heat, and the temperature distribution characteristic of FIG. 4 in which the temperature of the portion located in the temperature control body 21 rises as shown by the arrow b ′ in FIG. The temperature distribution is as shown in b.

  A thermistor 26 is attached at a position where the temperature control body 21 is formed. The thermistor 26 whose detected temperature has risen more than before reliably detects the rising portion of the arrow b ′ in FIG. 4 and operates the temperature control circuit in FIG. 5 to stop energization of the heating resistors 12 and 13. Etc. are controlled. As a result, the thermistor 26 can prevent adverse effects such as breakage of the ceramic substrate 11, breakage of the wiring of the circuit for energizing the heating resistors 12 and 13, and the circuit for temperature control.

  In this embodiment, even if the detection performance of the thermistor for detecting an abnormal temperature rise of the heating resistor is lower than the design value, the temperature of the thermistor is increased by increasing the temperature of the portion where the thermistor is attached. It becomes possible to stop the runaway due to the deterioration of the detection characteristics.

  Although the overcoat layer is provided on the side where the heating resistors 12 and 13 are formed, it may be provided on the side where the thermistor 26 is attached. Further, the narrowed portions 19 and 20 formed on the heat generating resistors 12 and 13 may be formed on the adjacent heat generating resistors 12 and 13 to which the connection patterns 16 and 17 are connected as necessary. Good.

Next, an embodiment of the heating device according to the present invention will be described with reference to the schematic configuration diagram of FIG. Reference numeral 100 in the figure denotes the plate heater described with reference to FIGS. 1 and 2, and the same portions are denoted by the same reference numerals and the description thereof is omitted.
FIG. 6 is a schematic configuration diagram for explaining an embodiment in which the plate heater 100 of the present invention is a heating device 200 for toner fixing.
In FIG. 6, reference numeral 201 denotes a plate heater 100 fixed to the bottom of a support 202, an AC voltage is supplied to the plate heater 100, and the plate heater 100 moves while being pressed and heated to the overcoat layer 22 of the heated plate heater 100. It is a cylindrical fixing film in which a heat-resistant sheet such as polyimide resin is rolled and wound in a circulatory manner. Reference numeral 203 denotes a pressure roller in which a heat-resistant elastic material such as a silicone rubber layer 204 is fitted on the surface of the fixing film 201, and the plate heater 100 is opposed to the rotation shaft 205 of the pressure roller 203. It is mounted in a base (not shown) in parallel with the fixing film 201. The pressure roller 203 is brought into pressure contact with the fixing film 201 based on a means (not shown) to form a nip portion, and is rotated in the direction of the arrow during operation.

  At this time, between the surface of the fixing film 201 disposed on the overcoat layer 22 and the silicone rubber layer 204, the toner image To1 is first heated and melted by the plate heater 100 via the fixing film 201, and at least the surface portion thereof. Greatly exceeds the melting point and completely softens and melts. Thereafter, on the paper discharge side of the pressure roller 203, the copy paper P is separated from the plate heater 100, the toner image To2 is naturally radiated and cooled and solidified again, and the fixing film 201 is also separated from the copy paper P.

  In this embodiment, even when the detection level of the thermistor, which is a temperature sensor, is decreased, an abnormal temperature rise of the plate heater can be detected by the thermistor. As a result, it becomes possible to operate a temperature control function for stopping energization of the heating resistor of the plate heater based on the temperature detection information of the thermistor, and it is possible to prevent harmful effects caused by temperature runaway in the plate heater. .

Next, an image forming apparatus according to the present invention will be described with reference to the schematic configuration diagram of FIG. 7, taking as an example a copier equipped with the heating device 200 according to the present invention. In the figure, the portion of the heating device 200 is the same as the configuration described in FIG. 6 described above, and the same portions are denoted by the same reference numerals and description thereof is omitted.
In FIG. 7, reference numeral 301 denotes a casing of the copying machine 300, and 302 an original placing table made of a transparent member such as glass provided on the upper surface of the casing 301, which scans the original P <b> 1 by reciprocating in the arrow Y direction.

  An illuminating device 302 including a light irradiation lamp and a reflecting mirror is provided in the upper direction in the housing 301, and a reflected light source from the document P1 irradiated by the illuminating device 302 is a short focus small diameter imaging element. A slit exposure is performed on the photosensitive drum 304 by the array 303. The photosensitive drum 304 rotates in the direction of the arrow.

  Reference numeral 305 denotes a charger that uniformly charges, for example, a photosensitive drum 304 coated with a zinc oxide photosensitive layer or an organic semiconductor photosensitive layer. An electrostatic image subjected to image exposure by the imaging element array 303 is formed on the photosensitive drum 304 charged by the charger 305. This electrostatic image is visualized using toner made of a resin that softens and melts when heated by the developing device 306.

  The copy paper P stored in the cassette 307 is rotated by a pair of conveying rollers 309 which are rotated while being pressed in the vertical direction while synchronizing the timing between the feeding roller 308 and the image on the photosensitive drum 304. Sent on 304. The toner image formed on the photosensitive drum 304 by the transfer discharger 310 is transferred onto the copy paper P.

  Thereafter, the paper P that is separated from the photosensitive drum 304 is guided to the heating device 200 by the conveyance guide 311 and subjected to a heat fixing process, and then is discharged into the tray 312. After the toner image is transferred, residual toner on the photosensitive drum 304 is removed using a cleaner 313.

  The heating device 200 has an effective length according to the width (length) of the maximum size paper that can be copied by the copying machine 300 in the direction orthogonal to the moving direction of the copy paper P, that is, the width (length) of the maximum size paper. A plate heater 100 having a long heating resistor is provided in a state of being pressed by a silicone rubber layer 204 attached to the outer periphery of the pressure roller 203.

  The unfixed toner image T1 on the paper P sent between the plate heater 100 and the pressure roller 203 is melted by receiving heat from the heating resistor 12, and is printed with letters, alphanumeric characters, Copy images such as symbols and drawings are displayed.

  In this embodiment, the temperature control circuit can be controlled even when the temperature detected by the thermistor rises from the design value. As a result, it is possible to realize an image forming apparatus with excellent safety using the heating device by the plate heater 100 that prevents the adverse effects caused by the temperature runaway of the plate heater.

  The plate heater is used for fixing image forming apparatuses such as copying machines, but is not limited to this. For household appliances, precision equipment for business use and experiments, equipment for chemical reaction, etc. It can be used as a heat source for heating and heat retention.

BRIEF DESCRIPTION OF THE DRAWINGS (a) is a front view for demonstrating one Embodiment regarding the plate-shaped heater of this invention, (b) is a rear view of (a). Xx sectional drawing of FIG. Explanatory drawing for demonstrating the characteristic of the principal part of FIG. Explanatory drawing for demonstrating the effect of this invention. The circuit block diagram for demonstrating an example of the temperature control circuit used for this invention. The schematic block diagram for demonstrating one Embodiment regarding the heating apparatus of this invention. 1 is a schematic configuration diagram for explaining an embodiment of an image forming apparatus according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Ceramic substrate 12, 13 Heating resistor 14, 15 Electrode 16-18 Connection pattern 19, 20 Restriction part 21 Temperature control body 22 Overcoat layer 23, 24 Terminal part 25, 27 Wiring pattern 26 Thermistor 100 Plate heater 200 Heating device 300 copier

Claims (5)

A long flat ceramic substrate;
First and second heating resistors formed in the longitudinal direction of one surface of the ceramic substrate;
First and second electrodes connected to one end of each of the first and second heating resistors and formed to supply power;
A connection pattern for connecting the other ends of the first and second heating resistors, and connecting the first and second heating resistors in series;
A temperature control body having a negative resistance temperature coefficient connecting the first and second heating resistors to an intermediate portion in the longitudinal direction of the first and second heating resistors;
An overcoat layer covering the first and second heating resistors, the temperature control body;
And a temperature sensor attached to a position on the opposite surface of the ceramic substrate on which the temperature control body is formed.   2. The plate heater according to claim 1, wherein when the heat generation temperature of the heat generating resistor is abnormal, the temperature of the temperature control body is increased.   3. The plate heater according to claim 1, wherein the temperature sensor stops energization of the first and second heat generating resistors when the heat is higher than the heat generated by the heat generating resistors. 4. A heating roller;
The plate heater according to claims 1 to 3, wherein the first and second heat generating resistors arranged to face the heating roller are pressed against each other.
A heating apparatus comprising: a fixing film movably provided between the plate heater and the pressure roller. Forming means for attaching a toner to an electrostatic latent image formed on a medium and transferring the toner to a sheet to form a predetermined image;
5. A heating apparatus according to claim 4, wherein the toner is fixed by passing the paper on which the image is formed through the fixing film while being pressed against the heater by a pressure roller. Image forming apparatus.

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