JPH0481877A - Heater for fixing - Google Patents

Abstract

PURPOSE:To obtain an optimum heating condition according to the sizes of transfer paper and to assure the stable traveling of a fixed film by electrically insulating and laminating heating members varying in length, providing thermistors on the respective heating members, and controlling energization by the outputs thereof. CONSTITUTION:Only the 1st heating member 3 operates and the output of the thermistor 14 is inputted via a temp. detecting circuit 40 to a CPU 41 in the case of fixing of the transfer paper of an A4 size. The energization of a heating element driving circuit 42 is controlled by the CPU 41 in such a manner that the output signal of the thermistor 14 attains a regulated value. The outputs of the thermistors 12, 14 are respectively inputted via the temp. detecting circuits 40, 43 to the CPU 41. The energization of the heating element driving circuits 43, 44 is controlled by the CPU 41 in such a manner that the output signals of the thermistors 12, 14 respectively attain regulated values. The heating conditions suitable for the stable traveling of the film are empirically determined and the relations between the width of the transfer paper and the output values of the thermistors 12, 14 are stored in a memory 45.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a heater for a heat fixing device of an image recording apparatus that records an image on a recording material using toner particles or ink.

[Prior art] A fixing method that replaces the conventional heat roller method was developed in Japanese Patent Application Laid-open No. 6
A fixing device described in Japanese Patent No. 3-313182 has been proposed. This fixing method places a fixing film between a heater and an elastic pressure roller, and transports the toner image recorded on the transfer material between the film and the pressure roller, with the toner image recorded on the transfer material on the film side. be.

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

To explain this in detail, when the width of the transfer material is smaller than the width of the heating element, the heat from the heating element is absorbed by the transfer material through the fixing film in the area where the transfer material passes, and the rest is transferred to the pressure roller. However, in areas where the transfer material has not passed, the heat transferred to the fixing film is transferred directly to the pressure roller. For this reason, the temperature of the pressure roller becomes non-uniform, resulting in a difference in diameter due to thermal expansion. As a result, a temperature gradient is created in the fixing film, causing changes in diameter and length due to thermal expansion, making normal film transportation impossible.

The present invention aims to solve the above problems. That is, an object of the present invention is to provide a fixing heater that enables stable film running and fixing.

[Means to solve the problem]

In order to achieve the above object, the present invention includes an endless fixing film, a film conveying means for driving the fixing film in the circumferential direction, a heating element provided on the inner peripheral surface side of the fixing film, and In the fixing device, a pressing means for pressing the fixing film against the heating element is provided at a position facing the heating element with the fixing film interposed therebetween, the heating element comprising:
It consists of a heat generating member made of multiple layers of electric resistors formed on the surface of a plate-shaped substrate, each heat generating member is electrically insulated by an electric insulator, and the heat generating length of each heat generating member is The heat generating member is made of different heat generating members, and is provided with a thermistor provided corresponding to each of the heat generating members.

[Function] According to the present invention, the heating element is composed of a heating member made of multiple layers of electrical resistors formed on the surface of a plate-shaped substrate, and each heating member is electrically insulated by an electrical insulator. In addition to being insulated, each heat generating member has a different length and is equipped with a thermistor provided corresponding to each heat generating member. The fixing film can be optimized according to the fixing conditions, and the fixing film can be stably run while satisfying the fixing conditions.

Embodiment 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 space 1. Its structure is such that electrodes 2.4 are formed at both ends of the heat generating member 3. The electrode 2.4 is made of a material with low electrical resistance, such as silver. The heat generating member 3 is made of an electrical resistor such as silver palladium or carbon, and the electrodes 2.4 and the heat generating member 3 are formed on the surface of the ceramic space 1 by printing technology. 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 electrode 2.4 is coated with an insulating material 9 such as glass.

Furthermore, a second heat generating member 6 is formed on the upper surface of the insulating material 9. Its configuration is also similar to 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 they are electrically connected, and there is an insulating material 9 between the first heat generating member 3 and the second heat generating member 6, so that they are insulated. . Second heat generating member 6
is shorter than the first heat generating member 3. The electric current M17 is guided by the lead 13 at a position adjacent to the electrode 4 without contacting each other.

Thermistor 1 for detecting the temperature of the second heat generating member 6
2 is embedded in a hole provided on the back surface of the ceramic space 1, and its position is 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 space 1, and is led to the end of the ceramic space 1 to form an electrode. Also the first
Similarly, the thermistor 14 for detecting the temperature of the first heat generating member 3 is located at a certain distance from the longitudinal end of the first heat generating member 3 and at a position that does not overlap with the second heat generating member 6.

Similarly, the output terminal of the thermistor 14 is connected to the lead pattern 1.
4a and 14b and guided to the end of the ceramic space 1 to form an electrode. Further, each electrode is connected to a connector contact terminal (not shown), and is supplied with electric power by a control circuit (not shown).

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

The electrodes 2 and 5 at one end of the heater 10 are overlapped,
The connector 30 is inserted here in the direction of the arrow. There are contacts 31 inside the connector 30, which are led to a heater control circuit (not shown) by a leet wire 32.

The other end of the heater 10 has an electrode 4.7 into which a connector 33 is inserted in the direction of arrow E. Inside this connector 33 there are contacts 34, 35, each contacting an electrode 4, 7. Also, the lower part of the connector is the contact 36a,
36b, 36cJ6d, and glue patterns 12a, 14 from the thermistor formed on the back side of the heater 10.
a, +4b, and 12b, respectively. Further, each contact is connected to a heater control circuit (not shown) by a wire 3738.39.

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

At the bottom of the first heat generating member 3 and the second heat generating member 6 of the ceramic space 1, there are holes for embedding a thermistor 12 and a thermistor 14 (not shown). Thermistor 1
2 is embedded in this hole and fixed with adhesive 11. However, if the thickness of the ceramic space 1 is as thin as about 1 mm, the hole for the thermistor is not necessary, and it may simply be fixed to the opposing surface of the heat generating member with an adhesive.

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

A holder 16 is attached to the heater 10, and both ends of the holder 16 are supported by a frame (not shown). The fixing film 15 is transported in the direction of arrow A by transport rollers 17,18. At this time, the pressure roller 19
follows the direction of arrow B as the fixing film 15 moves. The inner surface of the fixing film 15 is pressed against the heating element of the heater 10 by a pressure roller 19. The pressure roller 1 is moved along the fixing guide 22 with the recorded image side of the transfer paper 23 facing up.
9 and the fixing film 15. Next, it is discharged in the direction of arrow C by the pair 20 and 21.

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

For example, the difference in temperature control of the heating element for transfer paper widths of A4 size and A5 size will be explained.

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 a temperature detection circuit 40, A/D converted, and input to a CPU 41. The CPU 41 controls the energization of the heating element drive circuit 42 so that the output signal of the thermistor 14 becomes a specified value. Next, when fixing A5 size transfer paper, the first heat generating member 3 and the second
energization of each of the heat generating members 6 is controlled. First, the output of the thermistor 12 is inputted to the temperature detection circuit 40, and the output of the thermistor 14 is inputted to the temperature detection circuit 43, which are respectively subjected to /D conversion and inputted to the CPIJ 41. CPI
At I41, the heating element drive circuits 42 and 44 are energized so that the output No. 3 of the thermistor 12 and thermistor 14 becomes a specified value, respectively. The fixing film can run stably under certain conditions when the temperature of the transfer paper passing section and non-passing section is set to a certain temperature. This condition is determined empirically, and the relationship between the transfer paper width and the output values of the thermistors 12 and 14 is stored in the memory 45.

In this way, by independently controlling the energization of the first heat generating member 3 and the second heat generating member 6, which have two different heat generating lengths, stable running and fixing of the fixing film can be achieved.

In this example, two types of heat generating members are used as the heat generating elements, but it is also possible to laminate three or four types depending on the size of the transfer paper.

[Effects of the Invention] As explained above, according to the present invention, the heating element is stacked with electrical insulation between the heating members having different heating lengths,
Since a thermistor is provided corresponding to each heat generating member, each temperature can be detected by the thermistor, and the energization of each heat generating member can be controlled based on the result. Therefore, the heat generating conditions of the heat generating element can be transferred. The fixing film can be optimized according to the paper size, and the fixing film can be stably run while adjusting the fixing conditions.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 shows an embodiment of the present invention. Figure 2 is a perspective view of the connection between the heater and connector, Figure 3 is a cross-sectional view of the heater in the shorter direction, Figure 4 is a side view of the main parts of the fixing device, and Figure 5 is the heat generation. It is an explanatory diagram of body control. 1... Ceramic space 3... First heat generating member 6... Second heat generating member 8
．． 9... Insulating material 10... Heater 12.14
...Thermistor 15...Fixing film 17.1
8... Conveyance roller 19... Pressure roller and 4 others Figure 1 Figure 3 Figure 4

Claims (1)

[Scope of Claims] 1. An endless fixing film, a film transport means for driving the fixing film in the circumferential direction, a heating element provided on the inner peripheral surface side of the fixing film, and a heating element sandwiching the fixing film. In the fixing device, a pressing means for pressing the fixing film against the heating element is provided at a position facing the heating element, wherein the heating element is formed of a plurality of layers of electrical resistors formed on the surface of a plate-shaped substrate. Consisting of heat generating members, each heat generating member being electrically insulated by an electrical insulator, each heat generating member having a different heat generating length, and corresponding to each heat generating member. A fixing heater comprising a thermistor provided therein. 2. The fixing heater according to claim 1, further comprising a control means for controlling energization to each heat generating member from the output of the thermistor provided in correspondence.