JP2831446B2 - Fixing heater - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heater of a heat fixing device of an image recording apparatus that records an image on a recording material using toner particles or ink.

[Prior art] Japanese Patent Application Laid-Open
A fixing device described in JP-A-63-313182 has been proposed. In this fixing method, a fixing film is disposed between a heater and a pressure roller having elasticity, and a toner image recorded on a transfer material is transported between the film and the pressure roller with the toner image recorded on a transfer material side. is there.

[Problems to be Solved by the Invention] However, in the above-mentioned fixing method, the temperature distribution of the heating element becomes uneven, and wrinkles are generated on the fixing film, resulting in poor fixing. There is a problem that the transportation is hindered.

More specifically, when the width of the transfer material is smaller than the width of the heating element, the heat of the heating element is taken by the transfer material through the fixing film in a portion where the transfer material passes, and the rest is transmitted to the pressure roller. However, in a portion where the transfer material has not passed, the heat transmitted to the fixing film is directly transmitted to the pressure roller. For this reason, the temperature of the pressure roller becomes non-uniform, and a difference in diameter occurs due to thermal expansion. As a result, a temperature gradient also occurs in the fixing film, and a change in diameter or a change in length due to thermal expansion occurs, so that normal film conveyance becomes impossible.

The present invention seeks to solve the above problems. That is, an object of the present invention is to provide a fixing heater capable of performing stable film running and fixing.

Means for Solving the Problems In order to achieve the above object, the present invention provides an endless fixing film, a film transport means for driving the fixing film in a circumferential direction, and an inner peripheral surface side of the fixing film. And a pressing means for pressing the fixing film against the heating element at a position opposed to the heating element with the fixing film interposed therebetween, wherein the heating element has a plate-like shape. A heating element composed of a plurality of layers of electric resistors formed on the surface of the substrate, each of which is electrically insulated by an electric insulator, and each of which has a different heating length. And a thermistor provided corresponding to each of the heat generating members.

[Operation] According to the present invention, the heating element is composed of a heating member composed of a plurality of layers of electric resistors formed on the surface of the plate-shaped substrate, and each heating member is electrically insulated by the electric insulator. And the thermistors are made of different heating lengths and are provided corresponding to the respective heating members, so that the heating conditions of the heating elements are adjusted to the size of the transfer paper. Therefore, the fixing film can be stably run while satisfying the fixing conditions.

FIG. 1 is an exploded perspective view showing a heater 10 according to an embodiment of the present invention.

That is, the first heat generating member 3 is formed on the surface of the ceramic base 1. In the configuration, electrodes 2 and 4 are formed at both ends of the heat generating member 3. The electrodes 2 and 4 are made of a material having low electric resistance such as silver. The heating member 3 is made of, for example, an electric resistor such as silver palladium or carbon. The electrodes 2 and 4 and the heating member 3 are formed on the surface of the ceramic base 1 by a printing technique. The length of the member 3 is slightly longer than the maximum width of the transfer paper, and at least the sliding portion of the fixing film except for a part of the electrodes 2 and 4 is coated with an insulating material 9 such as glass.

Further, a second heat generating member 6 is formed on the upper surface of the insulating material 9. The configuration is the same as that of the first heat generating member 3. Electrodes 5, 7 are formed at both ends of the heat generating member 6.
There is no insulating material 9 between the electrode 2 and the electrode 5 and it is electrically conductive, and there is the insulating material 9 between the first heating member 3 and the second heating member 6 to be insulated. . Second heating member 6
Is shorter than the first heat generating member 3. The electrode 7 is
The leads 13 are guided at positions adjacent to the electrodes 4 without contacting each other.

Thermistor for detecting the temperature of the second heating member 6
Numeral 12 is embedded in a hole provided on the back surface of the ceramic base 1, and its position is at a certain distance from the longitudinal end of the second heat generating member 6. The output terminal of the thermistor 12 is connected to lead patterns 12a and 12b formed on the back surface of the ceramic base 1,
Is led to the end to form an electrode. Similarly, the thermistor 14 for detecting the temperature of the first heat generating member 3 is provided at a predetermined distance from the end of the first heat generating member 3 in the longitudinal direction.
Is located at a position that does not overlap with the heat generating member 6. Similarly, the output terminals of the thermistor 14 have lead patterns 14a and 14b.
And is led to the end of the ceramic base 1 to form an electrode. Each electrode is connected to a connector contact terminal (not shown), and power is supplied by a control circuit (not shown).

FIG. 2 is a perspective view showing the relationship between the heater 10 and a connector for supplying electric power to the heater 10.

The electrodes 2 and 5 at one end of the heater 10 are overlapped, and the connector 30 is inserted in this direction in the direction of arrow D. connector
The inside of 30 has a contact 31 and is led to a heater control circuit (not shown) by a lead wire 32. The other end of the heater 10 has electrodes 4 and 7, into which a connector 33 is inserted in the direction of arrow E. Inside the connector 33, there are contacts 34 and 35, which contact the electrodes 4 and 7, respectively. The lower part of the connector has contacts 36a, 36b, 36c, and 36d.
Lead pattern 12 from the thermistor formed on the back surface of
a, 14a, 14b, and 12b, respectively. Further, each contact is connected to a heater control circuit (not shown) by leads 37, 38, and 39.

FIG. 3 is a cross-sectional view of the heater 10 in the lateral direction, and the description of the same reference numerals as in FIG. 1 is omitted.

Holes for embedding a thermistor 12 and a thermistor 14 (not shown) are provided below the first heat generating member 3 and the second heat generating member 6 of the ceramic base 1. The thermistor 12 is embedded in this hole and fixed with the adhesive 11. However, if the thickness of the ceramic base 1 is as thin as about 1 mm, the hole of the thermistor is unnecessary, and it may be merely fixed to the facing surface of the heat generating member with an adhesive.

FIG. 4 is a side view showing a main part of a fixing device using the fixing heater of the present invention.

The heater 10 has a holder 16 attached thereto, and both ends of the holder 16 are supported by frames (not shown).
The fixing film 15 is transported in the direction of arrow A by the transport rollers 17 and 18. At this time, the pressure roller 19 is driven in the direction of arrow B as the fixing film 15 moves. The inner surface of the fixing film 15 is pressed by the pressure roller 19 against the heating element of the heater 10. The paper passes between the pressure roller 19 and the fixing film 15 along the fixing guide 22 with the recording image surface of the transfer paper 23 facing upward. Next, the arrow C is indicated by the pair 20, 21.
Is discharged in the direction of.

FIG. 5 is a schematic block diagram showing the relationship between the transfer paper width fixed by the fixing device and the temperature control of the heating element.

For example, the difference in the temperature control of the heating element between the transfer paper width A4 size and the transfer paper width A5 size will be described. When fixing A4 size transfer paper, the first heat generating member 3 operates and the second heat generating member 6 does not operate. The output of the thermistor 14 is input to the temperature detection circuit 40, A / D converted, and input to the CPU 41. CP
In U41, energization of the heating element drive circuit 42 is controlled so that the output signal of the thermistor 14 becomes a specified value. Next, when fixing A5 size transfer paper, the energization of each of the first heating member 3 and the second heating member 6 is controlled. First, the output of the thermistor 12 is input to the temperature detection circuit 40,
The output of 14 is input to the temperature detection circuit 43, A / D converted, and input to the CPU 41. The CPU 41 controls the energization of the heating element drive circuits 42 and 44 so that the output signals of the thermistor 12 and the thermistor 14 become the specified values, respectively. The temperature of the passing portion and the non-passing portion of the transfer paper can stably run the fixing film under certain conditions. These conditions are determined empirically, and include the transfer paper width and the thermistor 12 and thermistor 14.
Are stored in the memory 45.

As described above, by independently controlling the energization of the first heating member 3 and the second heating member 6 having two different heating lengths,
Stable running and fixing of the fixing film can be achieved.

In the present embodiment, two types of heat generating members are used as the heat generating elements. However, three or four types of heat generating members can be stacked according to the size of the transfer paper.

[Effects of the Invention] As described above, according to the present invention, the heating elements are laminated while electrically insulating the heating members having different heating lengths, and the thermistor is provided corresponding to each heating member. Since the temperature is detected by the thermistor, it is possible to control the energization of each heat generating member from the result, so that the heat generating condition of the heat generating element is optimized according to the size of the transfer paper. Therefore, there is an effect that the fixing film can run stably while satisfying the fixing conditions.

[Brief description of the drawings]

Drawings show an embodiment of the present invention, FIG. 1 is an exploded perspective view of a heater, FIG. 2 is a perspective view of a connection relationship between a heater and a connector, FIG. FIG. 4 is a side view of a main part of the fixing device, and FIG. 5 is an explanatory diagram of heating element control. DESCRIPTION OF SYMBOLS 1 ... Ceramic base 3 ... 1st heating member, 6 ... 2nd heating member 8, 9 ... Insulating material, 10 ... Heater 12, 14 ... Thermistor, 15 ... Fixing film 17, 18 ... … Transport roller, 19… Pressure roller

Claims (2)

(57) [Claims] An endless fixing film; a film transport means for driving the fixing film in a circumferential direction; a heating element provided on an inner peripheral surface side of the fixing film; A pressing unit for pressing the fixing film against the heating element at a position facing the body, wherein the heating element is a heating member formed by a plurality of layers of electric resistors formed on the surface of a plate-shaped substrate. Consisting of
Each of the heat generating members is electrically insulated by an electric insulator, and each of the heat generating members has a different heat generation length, and includes a thermistor provided corresponding to each of the heat generating members. A fixing heater. 2. A fixing heater according to claim 1, further comprising control means for controlling energization of each heat generating member from an output of a thermistor provided in correspondence therewith.