JPH06295778A - Heating device - Google Patents

Abstract

PURPOSE:To eliminate the troublesome adjustment of the fitting position of a safety element, and substantially improve assemblage by fitting the locating section of the element to an insulating holder in direct contact therewith. CONSTITUTION:A thermal fuse 12 as a safety element is provided at the intermediate position of the wiring 17 of a heating body 1, and both right and left sections of the fuse 12 are fastened to a pit insert 10a buried in an insulating holder 10 with screws 16, together with wiring. As a result, the locating section 12a of the thermal fuse 12 can be directly fitted to the holder 10, and no dimensional fluctuation occurs between the thermal fuse 12 and the location section 12a thereof. Thus, a fine gap (x) required between the thermal fuse 12 and the holder 10 for fastening the fuse 12 on the basis of only the dimensional accuracy thereof can be guaranteed. According to this construction, the uniform fixing quality of the thermal fuse 12 can be attained due to a nip section, without any influence upon the lengthwise temperature distribution of a heating device 18, and an adjusting work for a thermal fuse mounting position is eliminated, thereby improving assemblage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating device used in a printing section of an OA equipment, a fixing section or a laminating section of an image forming apparatus.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 5, in a heating device, a thermal fuse 54, which is a safety element, is provided in the middle of a wiring 56 of a heating body 51, and the safety element 54 is mounted on an element mounting base 55. Installed body stay 5 using a heating device
3 is configured to be fixed on. 52 in the figure
Is a heat insulating holder.

In this case, the safety element 54 needs to be attached to the heat insulating holder 52 on the back side of the heating body 51 with a minute gap δ therebetween. This is because this type of heating device using a fixed surface heating element generally has a small input power (about 700 W MAX in the present invention) to the heating element 51, and the safety element 54 contacts the heat insulating holder 52. When the heating device is operated, heat is taken only at the portion of the safety element 54 of the heating element 51, and the temperature distribution becomes low only at that portion, so that the performance of the heating device cannot be satisfied, and conversely, the distance δ is large. If this happens, the safety element 54 will not operate reliably when there is an abnormality, so the distance δ must be small. In the experiment by the inventor, desirable results were obtained when the range of δ was 0 <δ <0.3 mm.

[0004]

However, in the above-mentioned prior art example, the safety element 54 fixed to the element mounting base 55 is fixed to the main body stay 53, and the heat insulating holder 52 is also mounted on the main body stay 53. Therefore, there are drawbacks in that the dimensional tolerances of the parts are overlapped with each other, and that the safety element 54 needs to be assembled while adjusting the mounting position in order to secure and mount the minute gap δ. In addition to the temperature fuse as the safety element, the thermoswitch or the like has the same problem.

[0005]

According to the present invention, the safety element and the safety element are mounted by directly abutting the positioning portion of the safety element on the heat insulating holder for supporting the heating element. Since the position required for the safety element can be ensured by the dimensional accuracy of the above, there is no need for complicated adjustment, and there is an effect of greatly improving the assemblability. Further, there is also a function of eliminating safety problems such as adjustment errors and improving safety.

[0006]

【Example】

<Embodiment 1> FIGS. 1 and 2 show a fixing device of a copying machine according to a first embodiment of the present invention, and FIG. 2 is a sectional view thereof.
In these figures, 1 is a fixed surface heating element, 2 is a fixing film, and polyimide, polyether imide, PE
A release layer such as PTFE is coated on the outer surface of a film of a heat-resistant resin such as S having a thickness of about 20 to 40 μm. Generally, the total thickness of the film is preferably 60 μm or less.

The fixing film 2 is stretched between the driving roller 3 and the tension roller 4 and forms a film conveying path together with the heating body 1. The fixing film 2 is given tension by urging the tension roller 4 in the direction of arrow A via the tension roller bearing 5 (6) by the urging means 7 (8), and the fixing roller 2 is driven by the drive roller 3 in the direction of arrow B. Is conveyed in the direction. Here, the drive roller 3 is provided with a rubber layer such as silicon rubber on the surface of a cored bar made of iron or the like in order to reliably convey the film 2.

A pressure roller 9 has a rubber elastic layer having a good releasability, such as silicon rubber, and presses the film 2 against the heating element 1 with a force necessary for fixing to form a nip portion. .
Both ends of the pressure roller 9 are supported by bearings (not shown) so as to rotate following the film 2. 13 is an inlet guide, 14 is a separation guide, 15 is a pair of rollers 15a, 1
5b is a paper discharge roller.

FIG. 1 is a view best showing the features of the present invention, and is a longitudinal sectional view of a heating device 18 of a fixing device of this embodiment. The heating body 1 is fixed on a stay 11 having rigidity to withstand the pressure applied from the pressure roller described above via a heat insulating holder 10 made of a heat resistant resin such as aromatic polyester, and constitutes a heating device 18. is doing.

On the back side of the heat insulating member, a thermal fuse 12 which is a safety element is arranged in the middle of the wiring 17 of the heating body 1, and the bit insert 10a embedded in the heat insulating holder 10 is connected to the wiring by screws 16 respectively. It is fixed.

Here, the positioning portion 12 of the thermal fuse 12
Since a is directly attached to the heat insulating holder 10, there is no dimensional variation between the thermal fuse 12 and its positioning portion 12a. Therefore, due to the dimensional accuracy of only the thermal fuse 12 and the heat insulating holder 10, it is possible to guarantee the minute interval x necessary for fixing the thermal fuse. Therefore, without affecting the temperature distribution in the longitudinal direction of the heating device 18,
The above-mentioned nip portion can satisfy the fixing property without unevenness.

Further, when the heating device is overheated, the temperature fuse 12, which is a safety element, is surely blown, and there is no problem in product safety.

In the above structure, the recording sheet (not shown) passes over the entrance guide 13 and passes through the film 2 and the pressure roller 9.
The toner image on the recording sheet is sent between the heating element 1 and
And the heat and pressure generated by the pressure roller 9 melt and heat the toner to fix it on the recording sheet evenly in the longitudinal direction.
After passing through the above, the paper is ejected outside the apparatus by the paper ejection roller 15.

As described above, the thermal fuse 1 which is a safety element
2 is directly attached to the heat insulating holder 10 supporting the heating body 1, so that the heat insulating holder 10 and the thermal fuse 1
Since the required position of the thermal fuse 12, which is a safety element, can be assured by the dimensional accuracy of the two parts of No. 2, it is possible to greatly improve the assemblability without requiring complicated adjustment. Furthermore, problems due to adjustment errors and the like can be eliminated, and safety can be improved.

<Embodiment 2> FIG. 3 is a sectional view of a heating device of a fixing device used in an image forming apparatus according to a second embodiment of the present invention. The fixed planar heating element 21 is fixed on the stay 23 having rigidity enough to withstand the pressing force through the heat insulating holder 22 made of a heat resistant resin, similarly to the first embodiment, and the heating device 20 is fixed. I am configuring.

A non-contact type thermoswitch 24, which is a safety element, is provided on the back side of the heat insulating holder 22. A screw 26 is attached to a bit insert 22a embedded in the heat insulating holder 22 in the middle of the wiring 25 of the heating body 21. It is fixed with each wiring.

In this case, the mounting springs 24b of the thermoswitch 24 bend on both sides, and the thermoswitch positioning portion 2
Since 4a abuts the back surface of the heat insulating holder 22 on both sides, the thermoswitch 24 can be fixed while ensuring the minute gap y required as a safety element.

Therefore, the fixing property without unevenness can be satisfied without affecting the temperature distribution in the longitudinal direction of the heating device 20, and when the abnormality of the heating device 20 occurs, the thermoswitch 24, which is a safety element, surely turns off. Since the current flowing through the heating element 21 is cut off, product safety is also satisfied.

As described above, the thermoswitch 24, which is a safety element, is attached to the heat insulating holder 22 supporting the heating body 21.
Since the positioning portion 24a of the thermoswitch is directly contacted with the thermoswitch 24 and attached, the position required as a safety element of the thermoswitch 24 can be assured by the dimensional accuracy of only a single component of the thermoswitch 24. There is no need to make various adjustments, etc., and the assemblability can be greatly improved.

<Embodiment 3> FIG. 4 is a sectional view of a heating device 30 of a fixing device used in an image forming apparatus according to a third embodiment of the present invention. As in the first and second embodiments, the fixed surface heating element 31 is mounted on the stay 33 having rigidity enough to withstand the pressing force required for fixing, via the heat insulating holder 32 made of a heat resistant resin. It is fixed and constitutes the heating device 30.

A non-contact type thermoswitch 34, which is a safety element, is provided on the back side of the heat insulating holder 32, and two bosses 32a of the heat insulating holder 32 are provided in the middle of the wiring 35 of the heating body 31.
Each is snapped or patched.

In this case, since the mounting spring portion 34b of the thermoswitch 34 is bent on both sides and the positioning portion 34a of the thermoswitch abuts on both sides of the thermoswitch hole 32b of the holder 32, the thermoswitch 34 serves as a safety element. The required minute gap Z with the heating element can be guaranteed and fixed.

Therefore, the fixing property without unevenness can be satisfied without affecting the temperature distribution in the longitudinal direction of the heating device 30, and in this case, the thermoswitch directly detects the heat of the heating member 30, so that when the heating member 30 is abnormally heated. Since the thermoswitch 24, which is a safety element, is turned off more reliably and the current flowing through the heating element 31 is cut off, the product safety is also satisfied.

As described above, the thermoswitch 34, which is a safety element, is attached to the heat insulating holder 32 that supports the heating body 31.
By directly abutting the positioning portion 34a of the thermoswitch onto the thermoswitch and attaching it with a patchon stopper, the thermoswitch 3
Because of the dimensional accuracy of 4 and the heat insulating holder 32, a direct minute gap between the thermoswitch and the heating body can be guaranteed, so that the assembling property can be further improved and the product safety can be improved.

In each of the above embodiments, the thermal conductivity of the heat insulating holder is 0.4 [Kcal / m] in view of the operation of the safety element.
· Hr · ° C] or less is preferable.

[0026]

As described above, according to the present invention,
By fixing the positioning part of the safety element, which shuts off the current flowing through the fixed surface heating element when it is abnormal, by directly abutting it on the heat insulating holder that supports the heating element, the position required for the safety element can be insulated. Since it can be guaranteed by the dimensional accuracy of the holder, safety element, etc., it is not necessary to make complicated adjustments and the assemblability can be greatly improved.
Further, it has an effect of reducing the assembly cost. Further, it is possible to prevent a defect of the safety element due to an adjustment error or the like and improve product safety.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of a heating device according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a fixing device of a copying machine using the heating device according to the first embodiment of the present invention.

FIG. 3 is a longitudinal sectional view of a heating device according to a second embodiment of the present invention.

FIG. 4 is a longitudinal sectional view of a heating device according to a third embodiment of the present invention.

FIG. 5 is a longitudinal cross-sectional view of a heating device which is a conventional example.

[Explanation of reference numerals] 1, 21, 31, 51 ... Heating body 2 ... Fixing film 3 ... Driving roller 4 ... Tension roller 7, 8 ... Energizing means 10, 22, 32, 52 ... Thermal insulation holder 9 ... Pressure roller 11,23,3
3, 53 ... Stay 12, 54 ... Thermal fuse 24, 34 ... Non-contact type thermoswitch

Claims (4)

[Claims] 1. A fixed surface heating element having an electric resistance film provided on a heat conducting substrate, a heat insulating holder for supporting the heating element, and a current flowing through the heating element provided on the back side of the heat insulating holder. In a heating device having a safety element for shutting off when an abnormality occurs, the positioning part of the safety element is in contact with the heat insulating holder. 2. The heating device according to claim 1, wherein the safety element is fixed to the heat insulating holder at the positioning portion. 3. The thermal conductivity of the heat insulating holder is 0.4 [Kc.
al / m · hr · ° C.] or less. 3. The heating device according to claim 1, wherein 4. A heating device is used as a fixing heater, forms a nip portion with a pressure member, and transfers an unfixed toner image carried on a recording sheet via a heat-resistant endless film. The heating device according to any one of claims 1 to 3, which is used in a fixing device that heats, melts, and fixes.