JPH0651659A - Heater - Google Patents

Abstract

PURPOSE:To prevent the dielectric breakdown of a protective layer of a heating body by an overvoltage noise and to lower the level of the noise released from a power source line by providing a high resistor between an endless film and a frame ground. CONSTITUTION:The film 102 is formed by coating the surface of an insulating polyimide resin with a surface release layer consisting of PTFE contg. a low- resistance material. The end of heat resistant rubber 104b of a press roller is provided with a heat resistant material 104C having a high electrical conductivity so that the conductive surface release layer of the film 102 and the arbor 104a of the press roller can be connected. Consequently, the surface of the film 102 is set at nearly the same potential as the potential of the arbor 104a. A spring 112 is pressed to the end of the arbor 104a and the opposite side of the spring 112 is connected by caulking the high resistor 113 and a press- fitting terminal 114. The opposite side of the high resistor 113 is similarly connected to a spring 116 by caulking 115. The opposite side of the spring 116 is connected to the frame ground of the image forming device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating device for heating a toner image on a recording material with heat from a resistor through a film.

BACKGROUND ART In recent years, a film heating type heating device using a fixed heater and a film sliding on the heater has been considered.

Such a film heating type device is shown in FIG.
Shown in.

In FIG. 8, reference numeral 102 denotes an endless heat-resistant film, which is externally fitted to a stay 101 which is a guide member of a film including a heating body. A stay 1 including the inner peripheral length of the endless heat resistant film 102 and a heating body
The outer peripheral length of 01 is smaller than that of the film 102, for example, 3
Therefore, the film 102 is loosely fitted on the stay 101 with a sufficient circumferential length.

The film 102 has a film thickness of 1 in order to reduce the heat capacity and improve the quick start property.
A single layer of fluororesin such as PTFE, PFA, FEP or the like having heat resistance of 00 μm or less, preferably 50 μm or less and 20 μm or more, or polyimide, polyamideimide, PE
PTF on the outer peripheral surface of heat resistant resin such as EK, PES, PPS
A composite layer film coated with a release layer made of a fluororesin such as E, PFA or FEP can be used. In this example, a polyimide film having an outer peripheral surface coated with PTFE was used.

Reference numeral 103 is a heating element, and an electric resistance material such as Ag / Pd (silver-palladium) is formed on the surface of an insulating substrate made of alumina or the like to a thickness of about 10 μm and a width of 1 to 3 mm
Is coated by screen printing or the like on top of which a protective layer 107 is formed.
As such, an insulating layer such as glass or fluororesin is coated.

Reference numeral 104 denotes a pressure roller as a rotating body for driving the film 102 by forming a nip with the heating body 103 sandwiching the film 102, and having a releasing property such as a core metal 104a and silicon rubber. It is made of good heat-resistant rubber 104b, and is driven by an unillustrated means from the end of the cored bar 104a.

For temperature control, the output of a thermistor 105 provided on the heating element (heater) 103 is A / D converted to control the CP.
Imported to U110 and based on that information, triac 1
11, the AC voltage applied to the heating element 103 is subjected to pulse width modulation such as phase and wave number control, and the heater energization power is controlled.

In such a film heating method, it may be considered that the film surface has a low resistance to be grounded in order to prevent electrostatic offset.

[0010]

However, if the film 102 is directly connected to the frame ground (hereinafter referred to as FG) of the image forming apparatus as described above, the following problems occur. First, when an excessive voltage is applied between the power source line and the FG due to external noise from the commercial power source line connected to the image forming apparatus, the excessive voltage is generated between the endless film 102 and the heating element 103. It is applied as it is,
The protective layer coated on the surface of the heating element 103 is destroyed. As a result, the insulation resistance and withstand voltage between the power supply line and FG, which are regulated by electrical safety, cannot be protected.

Secondly, the electric noise generated from the low voltage power source or the like in the image forming apparatus is similar to that in the power source line.
03, a capacitor is formed between the heating element 103 and the film 102, and noise from the heating element 103 flows into the FG via the capacitor in which the noise is formed.

As a result, the terminal noise (conduct)
The level of "d emissions" greatly exceeds the regulation value.

[0013]

SUMMARY OF THE INVENTION The present invention for solving the above-mentioned problems includes a resistor that generates heat when energized, an insulating layer that covers the resistor, and a film that slides on the insulating layer and has a low resistance layer. And a heating device for heating a recording material supporting a toner image by contacting it with a film, wherein the low resistance layer is grounded via a resistance.

[0014]

EXAMPLES Examples of the present invention will be described below.

The sectional structure is the same as that of the example shown in FIG.

FIG. 1 is a perspective view of an embodiment of the present invention. The film 102 has an insulating polyimide resin coated with a surface release layer made of PTFE containing a low resistance substance.

In the figure, a heat-resistant material 104c having high conductivity is provided at the end of the heat-resistant rubber 104b of the pressure roller 104, and the conductive surface release layer of the film 102 can be connected to the pressure-roller core metal 104a. To do so. As a result, the surface of the film 102 has almost the same potential as the core metal 104a.

A spring 112 is pressed against the end of the cored bar 104a, and the opposite side of the spring 112 is connected by caulking a high resistance body 113 and a crimp terminal 114. The opposite side of the high resistance body 113 is similarly caulked 115 with a spring 116.
, And the opposite side of the spring 116 is connected to the FG of the image forming apparatus.

High resistance body 113 and springs 112 and 11 on both sides
A part of 6 is fixed to a fixing device or an image forming device by a mold member 117.

The high resistance element used in this embodiment is a thick film resistor having a resistance value of 100 MΩ ± 20% and a withstand voltage of 5 kv.

It has been confirmed that the following effects can be obtained by using the fixing device having the structure shown in FIG.

1. Measures against noise from power supply line Excessive voltage noise from the power supply line, specifically, a lightning surge that is generally called is applied with a peak value of 5 kv, and at that time, the film 102 and the power supply line that is a heating body The voltage generated during this period can be kept below 1.6 kv. It is not easy to give the protective layer on the surface of the heating element up to a withstand voltage of 5 kv, but if it is about 1.6 kv, glass as a protective layer may be applied multiple times.

As described above, the thickness of the protective layer can be reduced, and the quick start property of the device is not deteriorated.

FIG. 2 shows the voltage waveform.

FIG. 3 shows an electric circuit configuration of the fixing device of the present invention. In the figure, 121 is a commercial power source and 122 is an external noise source. The high resistance arranged between the film and FG, which is a feature of the present invention, is R, and the heating element 103
When the stray capacitor generated between the film and the film 102 is C, the circuit diagram on the right side of FIG. 3 is equivalently obtained.

From this, it can be seen that the voltage applied to the protective layer on the surface of the heating element, that is, the voltage Vc across the capacitor C, is a voltage considerably suppressed from the noise voltage.

As a result, the dielectric strength standard value of the protective layer can be lowered as described above, and the cost of the ceramic heater can be reduced. The dielectric strength level of the protective layer is increased by firing glass material and repeating it many times. Therefore, by lowering the dielectric strength standard of the protective layer, the number of firing steps can be reduced, and the cost of the ceramic heater can be reduced.

2. Reduction of terminal noise As can be seen from Fig. 3, by adding a high resistance, noise from the heating element can be suppressed.

The measurement results of the terminal noise are shown in FIGS.

4 and 6 are in the frequency range of 10 KHz to 450 KHz, and FIGS. 5 and 7 are in the range of 450 KHz to 1.0 MH.
This is data in the frequency domain of z.

4 and 5 show a state without high resistance, and FIGS. 6 and 7 show a state with high resistance attached. From these data, it is possible to reduce the noise of about 10 dB by mounting the high resistance.

3. Prevention of leakage current increase to FG If the protective layer of the heating element is destroyed, leakage current may flow from the commercial power supply line, which is the heating element, to the FG. By arranging them in between, this leakage current can be suppressed to almost zero, and there is no danger to the operator of the image forming apparatus.

The resistance value of the resistor connected between the conductive layer of the film 102 and FG is preferably 10 MΩ to 300 MΩ.

If it is less than 10 MΩ, the noise countermeasure effect becomes insufficient.

On the other hand, if it is larger than 300 MΩ, a high voltage is generated in the film due to the current flowing from the recording material to the resistance through the film, and an electric field for attracting the toner is generated.
An electrostatic offset will occur.

FIG. 9 shows another embodiment.

In the figure, a conductive film 118 is brought into contact with the outer surface of the endless film 102 just opposite to the heating body 103, and the conductive film 119 is attached to the metal plate 1.
It is fixed at 19.

The connection method between the metal plate 119 and the FG is shown in FIG.
The connection method between the core metal 104a and the FG is the same.

Further, the heat-resistant material 1 having the structure shown in FIG.
It is also possible that 04c is made of a high resistance material and the cored bar 104a is directly connected to the FG.

Alternatively, the pressure roller 104b itself shown in FIG. 1 may be made of a high resistance material, and the core metal 104a may be directly connected to the FG as described above.

[0041]

As described above, by providing the high resistance body between the endless film and the FG, the dielectric breakdown of the heating body protective layer due to the excessive voltage noise coming from the commercial power supply line is prevented, and the heating body protective layer is released from the power supply line. It has the effect of reducing the noise level.

[Brief description of drawings]

FIG. 1 is a perspective view of a heating device according to an embodiment of the present invention.

FIG. 2 is a diagram showing overvoltage noise from a commercial power supply line and its reduction.

FIG. 3 is an electrical equivalent circuit of the heating apparatus of this embodiment.

FIG. 4 shows 10 KHz to 4 when the film is directly grounded.
It is a figure which shows the noise level of 50 KHz.

FIG. 5: 450 KHz when the film is directly grounded
It is a figure which shows the noise level of 1.0 MHz.

FIG. 6 is a diagram showing noise levels of 10 KHz to 450 KHz according to the present embodiment.

FIG. 7 is a diagram showing a noise level of 450 KHz to 1.0 MHz according to the present embodiment.

FIG. 8 is a sectional view of a film heating device.

FIG. 9 is a perspective view of another embodiment of the present invention.

[Explanation of symbols]

 102 Endless Film 103 Heating Body 104 Pressure Roller 113 High Resistance 121 Commercial Power Supply 122 Overvoltage Noise Source

Claims (3)

[Claims] 1. A recording material, which has a resistor that generates heat when energized, an insulating layer that covers the resistor, and a film that slides on the insulating layer and has a low resistance layer, and that indicates a toner image. A heating device for heating the low-resistance layer by contacting it with the ground, via a resistor. 2. The resistance value of the resistor is 10 MΩ to 300 M
The heating device according to claim 1, wherein the heating device is Ω. 3. The heating device according to claim 1, wherein the low resistance layer is a surface release layer that comes into contact with a toner image.