JP3005011B2 - Fixing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device that heats and fixes a toner image on a recording material via a film.

[Related Art] Conventionally, as a fixing device used in an image forming apparatus such as a copying machine or an electrophotographic printer, a heat roller fixing method has been widely used as a heat roller fixing method.

However, the heat roller stationary method has a problem that a warm-up time until the surface of the heat roller reaches a predetermined temperature is long.

In view of this, the applicant has previously proposed in Japanese Patent Application Laid-Open No. 63-313182 a fixing device in which the warm-up time is greatly reduced or eliminated by using a fixed heating element having a low heat capacity and a thin film.

As the heating element of the fixing device, a heating element having a resistance heating layer provided on a ceramic substrate having good thermal conductivity is used.

[Problems to be solved by the invention]

Lead wires were soldered directly to the electrodes provided at the end of the ceramic substrate to energize this heating element.
There is a problem that the assemblability and exchangeability are very poor.

For this reason, it is conceivable to use a detachable connector for the current-carrying contact to the electrode. However, there is a problem in that the ceramic substrate has poor workability and is liable to be broken.

[Means for Solving the Problems] In order to solve the above problems, the present invention relates to a heating element in which a resistor that generates heat when energized and an electrode for energizing the resistor are provided on one surface of a ceramic substrate; A holding member made of a resin that holds the heating body on a surface different from one surface of the body, and a fixing device that fixes an unfixed image on a recording material by heat from the heating body. A connector for supplying power to the resistor that is detachable from the holding member, wherein the connector has a contact portion that contacts the electrode on one surface of the heating element and the holding portion that is in contact with the holding member; An engagement portion that engages with a holding member engagement portion formed on the member, and when the connector is mounted,
The connector covers both the heating element and the holding member with the contact portion and the engagement portion.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

First, a schematic structure of an image forming apparatus using the fixing device of the present embodiment will be described with reference to FIG. 2. Reference numeral 1 denotes a document placing table made of a transparent member such as glass, which reciprocates in the direction of arrow a. Scan the original. A short-focus small-diameter imaging element array 2 is disposed immediately below the document table, and an image of the document placed on the document table is illuminated by an illumination lamp 3, and a reflected light image is formed on the photosensitive drum by the array 2. 4 is subjected to slit exposure. The photosensitive drum 4a rotates in the direction of arrow b. Reference numeral 5 denotes a charger, for example, a photosensitive drum 4 coated with a zinc oxide photosensitive layer or an organic semiconductor photosensitive layer.
Charging is performed uniformly on the top. On the drum 4 uniformly charged by the charger 5, an electrostatic image subjected to image exposure by the element array 2 is formed. This electrostatic latent image is visualized by the developing device 6 using a toner made of a resin or the like that softens and melts when heated. On the other hand, the sheet P accommodated in the cassette S is pressed against the feed roller 7 and the image on the photosensitive drum 4 in a vertical direction with timing so as to be synchronized with the image on the photosensitive drum 4, and is rotated by a pair of conveying rollers 8 which are rotated. Sent up. Then, the toner image formed on the photosensitive drum 4 is transferred onto the sheet P by the transfer discharger 9. Thereafter, the sheet P separated from the drum 4 by a known separating unit is fixed by a conveying guide 10 to a fixing device.
After being guided to 11 and subjected to the heat fixing process, it is discharged onto the tray 2. After the transfer of the toner image, the residual toner on the drum 4 is removed by the cleaner 13.

 FIG. 3 is an enlarged view of the fixing device 11 of the present embodiment.

Reference numeral 12 denotes a low-heat-capacity linear heating body fixedly supported by the apparatus, and is formed by coating a surface of an alumina substrate 13 having a thickness of 1.0 mm, a width of 10 mm and a length of 240 mm with a resistance material 14 to a width of 1.0 mm as an example. Energization from both ends in the direction is 100 VDC cycle 20
A pulse corresponding to a desired temperature and energy release amount controlled by the temperature detecting element 15 with a pulse waveform of msec is given by changing the pulse width. Approximate pulse width is 0.5msec
~ 5 msec.

The energization is not pulsed, and a predetermined energy may be given by rectifying an AC power supply. In this manner, the fixing film 16 moves in the direction of the arrow in the drawing while coming into contact with the heating element 12 whose energy and temperature are controlled. As an example of the fixing film, a heat-resistant film having a thickness of 20 μm, for example, a release layer obtained by adding a conductive material to a fluororesin such as PTFE and PFA on at least the image contacting surface side of polyimide, polyetherimide, PES, and PFA. This is an endless film coated with 10 μm. The film drive moves without wrinkles in the direction of the arrow due to the driving by the driving roller 17 and the driven roller 18 and the tension.

Reference numeral 19 denotes a pressure roller having a rubber elastic layer having good releasability, such as silicon rubber, having a total thickness of 4 to 7 kg, which presses a heating body through a film and rotates by pressing against the film.

Reference numeral 22 denotes a heat-resistant resin such as PPS, polyimide, or liquid crystal polymer.
Is a heating element holding member that holds a surface different from the one surface provided with the heating element 12, and the heating element 12 is bonded onto the holding member 22 with a heat resistant adhesive. The holding member 22 performs heat insulation between the stay 23 and the heating body 12.

Furthermore, the film guide portions 22a and 22b having a curvature provided on the upstream side and the downstream side of the heating body 12 in the transport direction of the film 16 prevent the film 16 from being damaged by an edge of the heating body 12, and further bend the film 16. The film drive torque is reduced by making the part smooth.

 FIG. 1 shows a method for energizing the heating element.

FIG. 1 (a) is a cross-sectional view showing an energized connector portion, and FIG.
FIG. 2B is a cross-sectional view of the heating element and the holding member.

Reference numeral 24 denotes a resistor on one surface of the heater 12 on which the resistor 14 is provided.
An electrode portion 25 made of a material such as silver provided at both ends of 14 is a connector for supplying power to the resistor 14 via a lead wire 26 from a power source (not shown) by contacting the electrode portion 24. The connector 25 has a contact portion 25a with the electrode 24,
The holding member 22 and the heating element 12 are made of a material having a spring property so that a contact pressure is applied in a direction indicated by an arrow b in FIG. For this reason, the holding member 22 and the heating element 12 are in a pressed state. A projection 25b, which is an engagement portion, is formed on the opposite side of the electrode 24 of the connector 25, and the projection 25b is a recess 22c which is a holding member engagement portion provided on the holding member 22.
To prevent the connector 25 from easily coming off in the direction of arrow c.

 Reference numeral 25c denotes a crimped portion of the lead wire 26.

FIG. 4 is an enlarged view of a connector portion. The holding member 22 is provided with a wall 22d on the connector insertion side, and is chamfered as a guide portion 22e to improve workability at the time of connector insertion.

Since the connector covers not only the heating element but also the holding member which is a heat insulating material, the strength of the heat insulating material can prevent the ceramic substrate from being broken when the connector is attached or detached.

Further, by setting the height of the wall 22d and the heating element 12 so that the height of the wall 22d is increased by d, the connector 25 does not come into contact with the edge 13a at the end of the ceramic substrate when the connector 25 is attached or detached.

Therefore, when the contact portion 25a of the connector 25 is provided with a damaged conductive coating, it is possible to prevent a power failure due to peeling of the plating.

By preventing the edge of the ceramic substrate from being in contact with the connector in this manner, the ceramic cut from one plate can be used without processing after rounding the edge.

Further, in this embodiment, the heating element and the holding member are bonded and fixed with a thermosetting adhesive.

However, the contact pressure of the connector 25 causes the heating element 12 to
Therefore, even when an impact or vibration is applied, the contact between the heating element 12 and the holding member 22 can be reliably maintained, and an accident such as peeling of the adhesive can be prevented.

By appropriately setting the heights of the projection 25b and the recess 22c, it is possible to arbitrarily set the attaching / detaching force of the connector.

FIG. 5 shows another embodiment. In this embodiment, the holding member engaging portion 22c engages with the projection 25b of the connector as in the first embodiment.

Further, the contact portion 27a of the connector 27 has a shape wrapping around the heating body 12 from both sides, the contact portion 27a contacts the electrode portion 24 at the edge portion, and the connector is attached and detached in the front and rear direction of the drawing. .

FIG. 6 shows still another embodiment, in which a holding member is shown.
An example is shown in which the connector 22 is prevented from coming off by providing a projection 22f having an inclined surface on the connector 22 and engaging with a hole 28c provided in the connector 28. In this case, changing the inclination of the slope of the projection 22f can be arbitrarily selected.

FIG. 7 is also a partial bottom view showing another embodiment, in which a holding member engaging portion with a connector is provided on both sides of a heating body.

29a is a contact portion of the connector 29, 29b is a cut-and-raised holding member 22.
By engaging the grooves 22g provided on both sides of the connector 2,
It functions as a 9-stop. In this case, it is possible to configure so that a load when passing through the engaging portion when attaching and detaching the connector is not applied to the contact portion 29a.

[Effects] As described above, according to the present invention, the connector can be attached and detached without cracking or cracking of the heating element.

Further, the connector is not damaged when the connector is attached or detached, and the power supply failure does not occur.

[Brief description of the drawings]

FIG. 1A is a cross-sectional view showing the relationship between a heating element, a holding member, and a connector according to an embodiment of the present invention. FIG. 1B is a bottom view of the heating element and a holding member according to the embodiment of the present invention. 2 is a cross-sectional view of an image forming apparatus to which the fixing device according to the embodiment of the present invention is applied, FIG. 3 is an enlarged cross-sectional view of the fixing device according to the embodiment of the present invention, and FIG. 5 and 6 are cross-sectional views of the vicinity of an enlarged connector of a fixing device according to another embodiment of the present invention. FIG. 7 is a vicinity of the connector of a fixing device according to still another embodiment of the present invention. FIG. 12 is a heating element, 13 is a ceramic substrate, 16 is a film, 22 is a heating element holding member, 22c is a holding member engaging section, 24 is an electrode section, 2
5 is a connector.

Claims (2)

(57) [Claims] 1. A heating element in which a resistor that generates heat by energization and an electrode for energizing the resistance element are provided on one surface of a ceramic substrate, and a resin that holds the heating element on a surface different from the one surface of the heating element. A fixing member for fixing an unfixed image on a recording material by heat from the heating element, wherein a current is supplied to the resistor that is detachable from the heating element and the holding member. A connector for contacting the electrode on one surface of the heating element and a holding member engaging portion formed on the holding member on the side of contact with the holding member. A fixing device, comprising: an engaging portion, wherein the connector covers both the heating element and the holding member with the contact portion and the engaging portion when the connector is mounted. 2. The fixing device according to claim 1, wherein the holding member has a protruding portion protruding from the surface of the heating body upstream of the end of the heating body in the connector mounting direction.