JPH0439077B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heating device for heating a material to be heated, such as a sheet material (cut or continuous) or a recording material supporting an unfixed image.

Generally, a heating device is provided with a temperature control device equipped with a safety mechanism in order to maintain the heating state at an appropriate temperature. Furthermore, it is desired that the heating device be able to perform predetermined heating by early start-up.
A typical example is a heat fixing device that fixes an unfixed image and is equipped with a heat roller, which is often used as a heating member. This heating fixing device will be explained below, but the present invention includes a heating device similar to the technical idea of the present invention.

Conventionally, in a heat fixing device, a temperature fuse is provided as a safety mechanism for a heat fixing roller as a heating body to prevent the heat source as a heat generating means from running out of control due to an abnormality in a heating control mechanism. Conventionally, this type of safety device has had to be placed at a certain distance (referred to as D) because the temperature fuse cannot be in constant contact with the heat roller. This is because constant contact would cause scratches on the surface of the heat roller, causing problems in the life of the fixing roller and the fixing performance. However, when placed at a distance, there is an air layer between the heat roller and the temperature fuse, which is easily affected by the atmosphere and wind flow, and the surface temperature of the heat roller when the temperature fuse blows varies. (Temperature fuse rating, mounting location) was also difficult.

Furthermore, the performance of the temperature fuse itself varies, and the operating time during actual heat source runaway may differ for each component. This variation becomes a big problem in machines where the surface temperature of the heat fixing roller increases significantly per unit time, causing thermal deterioration of the roller surface or heating devices near the fixing device in the recording apparatus.

Such problems are common to heating devices.

SUMMARY OF THE INVENTION In order to alleviate or eliminate the above-mentioned drawbacks and problems, it is an object of the present invention to provide a heating device that can operate accurately and maintain safety and durability.

The present invention provides that, in the event of an abnormality as described above, a heating body such as a heat roller, a heating fixing roller, or a heating plate is connected to a temperature fuse or a temperature sensing element (thermistor).
It is characterized by having a means for moving the heating body to bring it closer to a temperature-sensitive member such as the like.

The present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of the present invention in which the present invention is applied to a fixing device. 1 is a fixing roller, 2 is a heat source heater in the fixing roller, and 3 is a heat insulating bushing made of thermoplastic resin, which is used for the surfaces at both ends of the fixing roller and bearings (not shown), and absorbs the heat on the surface of the fixing roller 1 through the bearings. prevents it from leaking out. Let the thickness of this heat insulating bushing 3 be d.

A temperature fuse 4 is arranged above the fixing roller 1 with a distance D from the fixing roller 1. The circuit is configured so that when the temperature fuse 4 blows out, the voltage application to the heat source heater 2 of the fixing roller 1 is stopped (for example, a temperature fuse may be provided in series with the heater 2, or a DC relay may be installed). (You may also turn off heater 2 via ). Reference numeral 5 denotes a pressure roller (such as a silicone rubber roller) for increasing the nip width for forming a fixing area, and is brought into pressure contact with the fixing roller 1 by a pressure spring 6 and an arm 7. The pressing direction is the rotation center direction of the fixing roller 1, which is the upward direction in FIG.

Polyphenylene oxide (PPO) or polyphenylene sulfide (PPS) is considered to be suitable as the material for the heat insulating bushing 3, considering its heat resistance since it is used for the fixing roller portion. This should be determined in consideration of the temperature of the heat insulating bushing during actual use.

In the conventional example (in which the heat insulating bushing is made of a material that does not deform due to heat), if the heat source heater 2 goes out of control, the fixing roller 1 will be kept at the controlled temperature during normal use (approximately 160°C to 200°C, depending on the machine). ), but compared to the temperature rise rate of the fixing roller 1, the temperature rise of the temperature fuse 4 is about 1/3 compared to the rise rate of the fixing roller when there is no contact.
It takes a considerable amount of time to melt.
However, in order to prevent this, lowering the rated temperature (fusing temperature) of the temperature fuse may result in false detection (false blowing).
The danger of this increases.

The purpose of this embodiment is to eliminate the above drawbacks.
The solution is to use a member made of a material that thermally deforms at a predetermined temperature. In other words, when the temperature near the heat insulating bushing 3 of the fixing roller 1 reaches approximately 260°C (this is the heat deformation temperature of PPS), the heat roller 1 is heated by using the pressure from the pressure roller 5. By bringing it closer to the fuse 4, the temperature rise rate of the temperature fuse 4 is increased and the blowout is accelerated. More preferably, the surface of the fixing roller 1 may be brought into contact with the temperature fuse 4 to further accelerate the fusing. Accelerating fusing in this manner is effective for materials with high heating efficiency and rollers with small heat capacity such as thin metal rollers.

Figure 2 shows time on the horizontal axis and temperature on the vertical axis.
Attach a graph showing temperature changes in each part.

In FIG. 2, curve A is the surface temperature of the fixing roller in the embodiment shown in FIG. 1, and curve B is the surface temperature of the temperature fuse in the embodiment shown in FIG. In this case, the temperature fuse 4 (usage rating in this case is 192°C) was blown out about 60 seconds after the runaway started from room temperature, and the temperature rise of the fixing roller 1 was stopped. Due to the application of , the slope of curve B becomes steeper at about 40 seconds. This is approximately the roller surface temperature
This is because the heat insulating bushing 3 deforms at 250° C., the fixing roller 1 approaches the temperature fuse 4, and the distance between them is reduced.

For example, if the heat-insulating bushing 3 is made of thermosetting resin as in the past without applying the above embodiment, straight line A' (fixing roller surface temperature) in FIG.
As shown by straight line B' (temperature fuse surface temperature), temperature fuse 4 is heated until it reaches its rated temperature of 192°C.
It takes 90 seconds, and the surface temperature of the fixing roller at that time is approximately
The temperature can reach up to 560℃. Such runaway not only makes the fixing roller itself unusable, but also has an adverse thermal effect on various mechanisms such as the pressure roller, power supply section, heater tube wall, photoreceptor in the recording device, and developing device. .

However, by configuring the safety mechanism to accelerate its operation as in the embodiment described above, the above-mentioned adverse effects can be minimized.

FIG. 3 shows an example of a fixing device particularly effective to which the present invention is applied. The fixing roller 1 is a thin metal cylindrical roller with a wall thickness d of about 0.2 mm to 5 mm, and more preferably one that satisfies the formula 5/γ≦d≦γ/10 with respect to the diameter r. A tetrafluoroethylene resin layer is provided on the surface of the fixing roller 1 as a release layer.
11 is a heat insulating bushing made of the same thermoplastic material as described above. 10 is a bearing, and a rolling bearing is used. A gear 12 is made of resin or partially made of resin. This gear 12 is fixed to the fixing roller and is a drive system gear 1 (not shown in FIG. 1).
Linked to 6. The pressure roller 5 has a thin solid rubber layer 13 on the outer layer and a sponge rubber layer 1 on the inner layer in order to improve the temperature rise rate of the fixing roller due to heating.
5 (with an insulated air section) and rotates about an axis 14. This pressure roller 5 is the fixing roller 1
is in contact with. F indicates a pressing direction, and the pressing roller 5 is pressed so as to orient the fixing roller 1 toward the heater 4 .

The fixing device with this configuration has a short wait time of about 10 seconds to 1 minute, and the thermal efficiency (the efficiency with which the heat of the heater heats the roller surface) is very high, so the application of the present invention can bring great effects. produce.

Incidentally, when a heating body such as the fixing roller 1 is brought close to a temperature-sensitive member such as a temperature fuse, and a gear 12 is provided to make the heating body rotatable,
Transmission gear 16 for providing drive to the gear
It is preferable that the temperature sensing member be located laterally from the straight line connecting the temperature sensing member and the rotation axis of the heating body. This allows the heating element to move linearly, thereby speeding up the fusing.

In the above embodiment, the heating body is set to a temperature sensitive member at a predetermined temperature (in the above example, the maximum temperature in the temperature control fluctuation range is 200-odds of degrees Celsius).
However, in the present invention, a member made of heat-sublimating resin is used instead of this member, and the movement of the heating body is prevented by sublimating it at a high temperature. You can do it as well.

In the above embodiment, a member whose shape and/or volume changes thermally is provided between the bearing and the heating body and between the support part and the heating body, and this shape and/or volume change is utilized. Although a mechanism is operated to bring the heating body closer to the temperature-sensitive member, the present invention has the following features.
The bearing itself may be made of a volume-changing material such as thermoplastic resin or heat sublimation resin.

The point at which the material that can change shape and/or volume changes (transition point or sublimation temperature) corresponds to the temperature at which the heating element is in a high temperature state that is lower than the dangerous temperature called abnormality, which is higher than the normal predetermined temperature. It is preferable to set it to . This is because the corresponding temperatures indicate different temperatures corresponding to the temperature of the heating body itself depending on the position of the temperature-sensitive member.

In addition to a temperature fuse, the temperature sensing member may be a thermistor that moves in a similar manner, or may be a bimetal or shape memory alloy of a switching mechanism used to cut off current. Further, although the heating body is moved upward by the pressure mechanism, it may be made to fall due to its own weight. In this case, it is preferable that the temperature-sensitive member is provided below or to the side of the heating body.

In the above embodiments, a heat fixing device is used, but it is also applicable to devices that use a heating plate instead of rollers, lighting devices that substantially heat up such as a light source, flash fixing, or general It cannot be used in heating devices such as coating rollers or heating devices for various sheet materials or fibers.

Particularly effective embodiments of the fixing device of the present invention are summarized as follows: (1) The heat roller of the heat roller fixing device is attached to a recording device side plate or the fixing device side plate via a heat insulating member, and the heat roller is made of thermoplastic resin, thermosublimable resin, or volume changeable material, and when the heat roller surface temperature reaches a certain temperature higher than the temperature during normal use, the heat insulating member is thermally deformed or sublimated.
A fixing device characterized in that the heat roller moves in the pressing direction of a pressure roller that is in contact with the heat roller (the moving distance is d), (2) in (1) above, the fixing device is characterized in that the heat roller moves in the pressing direction of the pressure roller that is in contact with the heat roller; In an apparatus having a temperature fuse disposed substantially opposite to the pressure roller, and in which the heat source in the heat roller is turned off when the temperature fuse is disconnected, the heat source in the heat roller is normally used between the temperature fuse and the heat roller. (3) In (1), the fixing device has a temperature fuse disposed close to the heat roller and substantially opposite to the pressure roller; When the temperature fuse is disconnected, the heat source inside the heat roller is turned off, and when the heat insulating member is thermally deformed or thermally sublimated, the heat roller moves in the pressing direction of the pressure roller, thereby reducing the temperature. A fixing device in which the fuse and the heat roller are in contact is preferred.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of one embodiment of the present invention, FIG. 2 is a graph diagram for explaining the effects of the embodiment of the present invention, and FIG. 3 is an explanatory diagram of another embodiment of the present invention. 1 is a fixing roller, 2 is a heater, 3 and 11 are heat insulating bushes, 4 is a temperature fuse, and 5 is a pressure roller.

Claims (1)

[Scope of Claims] 1. A heating member heated by a heat source, a temperature-sensitive member that is provided in a non-contact manner with the heating member and cuts off electricity to the heating source when the temperature of the heating member rises excessively, and a heat-insulating member that insulates the heating member. and a supporting resin material, when the temperature of the heating member increases excessively, the distance between the heating member and the temperature sensing member is reduced by softening the resin material before the temperature sensing member is activated. A heating device featuring: