JPH11162618A - Heater device and fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heater device and fixing device that can raise temperature up to a disired temperature rapidly and stably and can reduce its power consumption in starting. SOLUTION: For a plate-like heater device 35 used for a toner fixing device, a resistor 54 to generate heat in carrying current is provided between electrode parts 51, 52 on the surfaces of a board 44. In addition, a PTC resistor 55 is provided in parallel with the resistor 54 and between the electrode parts 51, 52. The temperature coefficient of the resistance of the PTC resistor 55 is set at a positive value larger than the temperature coefficient of the resistance of the resistor 54. Yet additionally, the curve in a graph showing the temperature coefficient of the resistance of the PTC resistor 55 is set crossing the line of a graph showing the temperature coefficient of the resistance of the resistor 54 at a predetermined temperature above the normal temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to, for example, a heater device provided with a heating element on a substrate and a fixing device for fixing an image on paper by heating toner by the heater device.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine, a page printer, and a facsimile machine, a toner image formed on a photosensitive drum is transferred onto paper, and the toner image is heated and heated by a fixing device. A configuration in which pressure is applied to fix paper is known. Further, as the fixing device, a cylindrical fixing film and a heater device disposed inside the fixing film are replaced with a cylindrical heat roller, and a pressing roller which is rotated by being pressed against the heater device via the fixing film. There is known a configuration in which a sheet on which a toner image has been transferred is conveyed between the fixing film and a pressing roller to fix the toner image.

[0003] In this configuration, the heater device is also called a ceramic heater or the like, has an elongated thin plate-shaped substrate, and a heating portion formed of a resistor layer formed by thick film formation on one surface of the substrate. While being formed, on the other surface of the substrate, a chip-shaped thermistor for temperature measurement is attached, if necessary, by bonding, etc., on the back side of the heat-generating portion, so as to detect the temperature of the heat-generating portion. It has become.

[0004]

However, in the above-mentioned conventional configuration, if the heater device is started up instantaneously, that is, if the temperature is to be raised rapidly, a large voltage is applied when the power is turned on. Temperature detection cannot be performed in time, so that a so-called temperature overshoot in which stable control becomes difficult due to an excessive rise in the temperature of the heat-generating portion, etc., is caused.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a heater device and a fixing device capable of quickly and stably starting up at a desired temperature and reducing power consumption at the time of startup. And

[0006]

According to a first aspect of the present invention, there is provided a heater device comprising: a substrate; a pair of electrode portions provided on the substrate;
A resistor electrically connected between the electrodes and having a predetermined temperature coefficient of resistance; electrically connected between the electrodes and having a positive temperature coefficient of resistance greater than the resistance temperature coefficient of the resistor; and A PTC resistor whose resistance temperature coefficient has a value equal to the resistance of the resistor at a predetermined temperature from a normal temperature to a use temperature.

In this configuration, when a voltage is applied between the electrodes, the resistor generates heat. When a large voltage is applied to rapidly raise the temperature when the power is turned on, the resistance of the PTC resistor increases as the temperature rises. You. Therefore, the temperature can be quickly and stably raised to a desired temperature, power can be saved, and deterioration of each unit due to abnormal heat generation is suppressed.

According to a second aspect of the present invention, in the heater device according to the first aspect, the PTC resistor is laminated on the resistor via a dielectric layer.

In this configuration, the width of the substrate can be reduced as compared with the configuration in which the resistor and the PTC resistor are arranged adjacent to each other, and the equipment using the heater device can be downsized. , And the requirement for positional accuracy such as print formation is reduced, and the manufacturability is improved.

According to a third aspect of the present invention, there is provided a fixing device comprising: the heater device according to the first or second aspect; and a pressing unit that presses the print material having the fixed material adhered thereto toward the heater device.

[0011] In this configuration, claim 1 or claim 2
Since the heater device described above is provided, the fixing temperature is quickly stabilized at a desired temperature, and high-quality fixing can be quickly performed. In addition, unnecessary energization is suppressed, and power can be saved.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a heater device and a fixing device according to the present invention will be described below with reference to the drawings.

FIG. 1 is a plan view showing an embodiment of a heater device according to the present invention, FIG. 2 is a sectional view taken along the line AA of FIG. 1 showing the heater device, and FIG. FIG. 4 is an explanatory diagram of an image forming apparatus having the same heater device, FIG. 5 is an explanatory diagram of a fixing device having the same heater device, and FIG. 6 is a second embodiment. It is sectional drawing which shows the form.

In FIG. 4, reference numeral 11 denotes an electrophotographic copying machine as an image forming apparatus.
A feeding device 15, a transfer device 16, and a fixing device are provided along a conveyance path of a sheet (copying paper) P as a recording material as a printing material.
A reading device 18 including an optical system for reading an image is provided.

The supply device 15 includes a paper feed cassette 21, and the sheets P stacked and stored in the paper feed cassette 21 are peeled one by one, fed out, and conveyed by a plurality of conveying rollers 22.

The transfer device 16 includes a photosensitive drum 23, an optical system (not shown), a developing device 24, and a transfer corotron 2 that are sequentially arranged in the circumferential direction along the circumferential surface of the photosensitive drum 23.
5, a cleaner 26, a static elimination lamp 27, and the like. In the transfer device 16, an electrostatic latent image of an image is formed by an optical system on the photosensitive drum 23 charged by a charging corotron (not shown) based on the image read by the reading device 18. Then, a toner as a fixing object is attached to the electrostatic latent image by the developing device 24 to form a toner image T shown in FIG. Next, the photosensitive drum 23 is transferred by the transfer corotron 25.
The upper toner image T is transferred onto the conveyed paper P. Thereafter, the photosensitive drum 23 is cleaned by the cleaner 26, and is discharged by the discharge lamp 27.

Further, the fixing device 17 presses and heats the sheet P on which the toner image T has been transferred, so that the microcapsules contained in the toner are dissolved and fixed on the sheet P. That is, as shown in FIGS. 4 and 5, the fixing device 17 includes a fixing device main body (not shown), and a pressing roller 33 as pressing means provided below the conveyance path is provided on the fixing device main body. A heater device 35 which is a substrate device that is supported and is opposed to the pressing roller 33 across the transport path and is adjusted to a desired constant temperature is attached, and further surrounds the heater device 35 to be thin. And a cylindrical fixing film 36 is provided.
Further, the fixing device main body is provided with support bases 37 and 38 for guiding the paper P, which are located below the conveyance path.

Therefore, with the heater device 35 heated,
The pressing roller 33 is rotated and the fixing film 36 is rotated.
The roller P is rotated while being in sliding contact with the heater device 35, and the paper P on which the toner image (unfixed image) T has been transferred is transported along with the fixing film 36 to the transport path. The toner is pressurized and heated in a so-called nip portion which is a fixing portion between
The fixing film 36 is separated from the sheet P on which the toner is fixed when the fixing film 36 passes through the nip portion.
Subsequently, the paper P is discharged to the paper discharge unit 40.

Further, as shown in FIG.
Is rotated at substantially the same speed in the same direction as the pressing roller 33 by a driving roller, which is a moving driving means (not shown), is endless, has heat resistance, is formed by covering the polyimide film with a fluororesin layer, and is formed inside. It is supported in a substantially cylindrical shape by the plastic tray 41 arranged. It should be noted that a polyfluoroethylene film is provided between the plastic tray 41 and the fixing film 36 to enhance the lubricity. Further, the pressing roller 33 has a substantially cylindrical main body portion 33b centered on the rotating shaft 33a, and a press contact surface 33c is formed on the outer peripheral surface of the main body portion 33b.

On the other hand, the heater device 35 is also called, for example, a flat heater, a fixing heater, a planar heater, or a THP, and is a so-called thick film wiring board. As shown in FIGS. This substrate 44 has
An insulating and heat-resistant member such as alumina ceramic (Al ₂ O ₃ ) or glass having good thermal conductivity is integrally formed in an elongated rectangular plate shape, and as shown in FIG. The rear surface 44b faces the plastic tray 41, and is attached to the plastic tray 41.

As shown in FIGS. 1 and 2, the surface of the substrate 44 is firstly covered with a conductive metal.
And second electrode portions 51 and 52 are formed.
1, 52 electrically connected in parallel, and
4 are arranged in parallel along the longitudinal direction, and the resistor 54
And a PTC resistor 55.

As shown in the graph of FIG. 3, the resistor 54 has a substantially constant resistance irrespective of temperature, or has a negative resistance temperature whose resistance slightly decreases with increasing temperature. NTC (Negative Tempe)
Rt (rature coefficient) resistor or NTC thermistor, etc., and silver (Ag) / palladium (P
d) A thick-film NTC resistor paste such as a system is printed as a thick film on the substrate 44 and baked to form a heating element.

The PTC resistor 55 is a PTC (Positi
ve Temperature Coefficient) It is also called a thermistor, etc., as shown in the graph of FIG. 3, has a positive resistance temperature coefficient whose resistance value increases with temperature rise, and this resistance temperature coefficient is used from normal temperature. At a predetermined temperature up to the temperature, the resistance value of the resistor 54 coincides with the resistance value, that is, the lines of the graph of the temperature-resistance characteristic cross each other. The PTC resistor 55 is formed by printing and baking a paste obtained by kneading a powder of, for example, tungsten (W), nickel (Ni), platinum (Pt) as a main component. Parts are first and second
(A) extending parallel to each other from the electrode portions 51 and 52 of
g) are connected to the extending portions 51a and 52a which are conductors.

In this state, the resistor 54 and the PTC resistor 55 are connected to the first and second electrode portions 51 and 52 in parallel with each other, so to say, form a branch resistance. Therefore, as shown in the graph of FIG. 3, the combined resistance of the resistor 54 and the PTC resistor 55, that is, the parallel circuit resistance, rises rapidly at a predetermined temperature exceeding normal temperature, and rises and falls around this predetermined temperature. , The resistance value is kept substantially constant.

Further, on the surface side of the substrate 44, etc., a resistor
A glass coat (overcoat layer) 56 having heat resistance and insulation properties is formed of glass or a heat-resistant resin so as to cover 54 and the PTC resistor 55.

Although not shown, a predetermined wiring pattern is also formed on the back side of the substrate 44, a chip-shaped thermistor for measuring the temperature is electrically connected, and a reinforcing and heat transfer Is covered with an adhesive such as polyimide resin or epoxy resin for
It is bonded and fixed to 44.

By applying AC power between the first and second electrode portions 51 and 52 of the heater device 35 from a AC power source via a switching element and a fuse, the resistor 54 and the PTC resistor 55 are formed. Fever. The thermistor is connected to a control device and receives a DC voltage. Then, the control device captures a change in the resistance value of the thermistor as a change in voltage, detects the temperature of the heater device 35, and controls the switching element based on the detection result, that is, changes the pulse width (PWM control). ) Or on / off control to change the power supplied between the first and second electrode portions 51 and 52, thereby forming a power supply circuit for adjusting and maintaining the temperature of the heater device 35 at a predetermined temperature. ing.

According to the heater device 35 of the present embodiment, when a large voltage is applied to rapidly raise the temperature when the power is turned on, the resistance of the PTC resistor 55 increases as the temperature increases. For this reason, it is possible to suppress an unnecessary rise in temperature due to an excessive current supply, that is, to suppress a temperature overshoot by self-control. For this reason, it is possible to quickly and stably start up to a desired temperature, to reduce power consumption at the time of start-up by an amount corresponding to suppression of overshoot, and to suppress deterioration of each part due to abnormal heat generation.

Further, since the heater device 35 uses not only the PTC resistor 55 whose heating temperature can be adjusted only at the time of formation but also the resistor 54 which is an NTC resistor, the heater device 35 is applied using, for example, a thermistor. By adjusting the voltage, it is possible to finely adjust the temperature at the time of stability after startup. Also, when the PTC resistor 55 is used as a main heat generating means, power consumption can be reduced.

The fixing device 17 using such a heater device 35 and the electrophotographic copying machine 11 as an image forming device can quickly stabilize the fixing temperature to a desired temperature and can quickly obtain good quality. Fixing is possible, and the quality of an image can be improved. Further, unnecessary power supply can be suppressed, power can be saved, and further, occurrence of a failure can be suppressed and reliability can be improved.

In the above embodiment, an NTC resistor having a negative temperature coefficient of resistance was used as the resistor 54. However, the present invention is not limited to this. PTC if they cross at temperature
4 having a smaller temperature coefficient of resistance than the resistor 55, that is, FIG.
If the slope of the line in the graph shown in FIG. 7 is gentler than the PTC resistor 55, it can be used. That is, a resistor having a positive temperature coefficient of resistance can be used as the resistor 54.

In the above-described embodiment, the linear resistor 54 and the PTC resistor 55 are disposed one by one between the first and second electrode portions 51 and 52 provided at both ends of the substrate 44. Although the arrangement of the electrodes and the resistor can take various forms, for example, the first and second electrode portions 51 and 52 are formed at one end of the substrate 44, 54 and the PTC resistor 55 may be arranged so as to be folded back. Further, for example, a resistor 54 is disposed at a central portion between the first and second electrode portions 51 and 52 provided at both ends of the substrate 44, and in parallel along both sides of the resistor 54, PT
A C resistor 55 may be provided. Further, the resistor 54 and the PTC resistor 55 can be arranged not only on the front surface of the substrate 44 but also on the back surface side.

As in the second embodiment shown in FIG. 6, the first and second electrode portions along the longitudinal direction of the substrate 44 are provided.
Extension portions 51a, 52 made of a conductor such as silver (Ag) of 51, 52
With both sides connected to a, PT
The C resistor 55 is formed and formed by thick film printing and baking, and a dielectric layer 61 having excellent insulating properties is formed on the PTC resistor 55 as an intermediate layer by thick film printing or the like. On the dielectric layer 61, silver (Ag) / silver (Ag) /
A thick film NTC resistor paste such as palladium (Pd) is printed and fired to form a resistor 54, and a glass coat (overcoat layer) 56 is formed on the resistor 54.
Can also be formed. That is, in this configuration, the electrode portions 51 and 52 at both ends are shared by the resistor 54 and the PTC resistor 55.

In the configuration of the second embodiment, the width dimension of the substrate 44 can be reduced and the material cost can be reduced as compared with the configuration in which the resistor 54 and the PTC resistor 55 are arranged in parallel on the substrate 44. And the product outer shape can be reduced. Further, in this configuration, the resistor 54 and the PTC resistor 55
It is not necessary to form prints adjacent to each other at a narrow interval, and the requirement for printing positional accuracy can be reduced, so that manufacturability can be improved. In this configuration, the resistor 54 may be arranged on the substrate 44 side, and the PTC resistor 55 may be arranged on the resistor 54 via the dielectric layer 61.

In each of the embodiments described above, the fixing device 17 of the copying machine 11 has been described. However, OA equipment such as a facsimile device using an electrophotographic system, or an image processing device such as a page printer such as a laser printer. Besides,
The present invention can also be applied to a thin plate-shaped heater device used by being attached to small appliances such as household electric appliances and precision manufacturing equipment.

[0036]

According to the heater device of the first aspect, when a large voltage is applied to rapidly raise the temperature when the power is turned on, the resistance of the PTC resistor increases as the temperature increases. Unnecessary rise in temperature due to excessive energization can be suppressed. For this reason, it is possible to quickly and stably start up at a desired temperature, thereby saving power, and also suppressing deterioration of each part due to abnormal heat generation.

According to the heater device of the second aspect, in addition to the effect of the first aspect, by stacking the PTC resistor on the resistor via the dielectric layer, the resistor and the PTC resistor can be separated. Compared with the configuration in which the heaters are arranged adjacent to each other, the width of the substrate can be reduced, the size of a device using the heater device can be reduced, the requirement for positional accuracy such as print formation can be reduced, and productivity can be improved.

According to the fixing device of the third aspect, since the heater device of the first or second aspect is provided, the fixing temperature can be quickly stabilized at a desired temperature, and high-quality fixing can be quickly performed. At the same time, unnecessary power supply can be suppressed to realize power saving.

[Brief description of the drawings]

FIG. 1 is a plan view showing an embodiment of a heater device according to the present invention.

FIG. 2 is a sectional view taken along the line AA of FIG. 1 showing the same heater device.

FIG. 3 is a graph showing resistance-temperature characteristics for explaining the operation of the above heater device.

FIG. 4 is an explanatory diagram of an image forming apparatus provided with the above heater device.

FIG. 5 is an explanatory diagram of a fixing device having the same heater device.

FIG. 6 is a partial cross-sectional view showing a second embodiment of the substrate device of the present invention.

[Explanation of symbols]

 17 Fixing device 33 Pressing roller as pressing means 35 Heating device 44 Substrate 51, 52 Electrode 54 Resistor 55 PTC resistor 61 Dielectric layer P Paper as printing material

Claims (3)

[Claims] A substrate; a pair of electrode portions provided on the substrate; a resistor electrically connected between the electrode portions and having a predetermined temperature coefficient of resistance; and electrically connected between the electrode portions. ,
A PT having a positive resistance temperature coefficient larger than the resistance temperature coefficient of the resistor, and the resistance temperature coefficient having a value equal to the resistance value of the resistor at a predetermined temperature from normal temperature to use temperature.
And a C resistor. 2. The heater device according to claim 1, wherein the PTC resistor is laminated on the resistor via a dielectric layer. 3. A heater device according to claim 1, wherein:
Pressing means for pressing the printing material having the fixing material attached thereto toward the heater device side.