JPH0524930Y2 - - Google Patents

Description

[Detailed description of the invention] (Industrial application field) The invention is used in the technical field of fixing devices, and in particular prevents excessive temperature rise in a fixing roller in which a resistance heating layer is formed on a cylindrical base material. The present invention relates to a fixing roller device.

(Prior art) As a heating method for a cylindrical fixing roller, in contrast to the conventional indirect heating method using a halogen lamp, a method in which a resistance heating layer is provided on a cylindrical base material to directly heat the roller has recently been introduced. It is widely adopted. Since the fixing roller having such a resistance heating layer is directly heated, it takes less time from supplying power until the fixing roller reaches the set temperature under the same operating conditions than the indirect heating method described above. It has the advantage of being shorter. However, on the other hand, it also has the problem that the so-called overshoot, in which the temperature once greatly exceeds the set temperature and then drops to around the set temperature, is greater than that of the indirect heating method. Since the temperature rise gradient is large, measures must be taken to prevent excessive temperature rise in the event of an abnormality such as failure of the device. As a countermeasure to this problem, it is possible to use a temperature fuse, a thermoswitch, etc., but these methods also have the problem that they are difficult to control due to poor thermal response. Furthermore, if an attempt is made to increase the thermal conductivity by bringing a temperature fuse or the like into contact with it in order to improve its responsiveness, a problem arises in that it causes wear and scratches.

(Means for Solving the Problems) The present invention solves the problems of the conventional devices mentioned above, and provides a compact and inexpensive fixing device that does not require a special temperature detector, has excellent durability, and is compact and inexpensive. The purpose is to provide a roller device.

In order to achieve the above object, the present invention includes a cylindrical base material, a surface release layer formed on the cylindrical base material, and a resistance heating element layer provided between the cylindrical base material and the surface release layer. , and a fixing roller having a power receiving part provided in a circumferential shape for energizing the resistance heating layer, and a fixing roller that slides on the power receiving part of the fixing roller and presses it in the radial direction of the fixing roller by its own elasticity. and a power supply member made of a shape memory alloy, the power supply member being deformed in a direction opposite to the direction of pressure at a certain temperature or higher, and separating from the power receiving part. It is.

(Example) Hereinafter, an example of the present invention will be described based on the accompanying drawings.

FIG. 1 is a partially cutaway perspective view of the device of this embodiment.

In the figure, reference numeral 1 refers to a core metal which is a base material and has a cylindrical shape, and step portions 1A are formed at both ends, and each layer to be described later is laminated between the step portions, and the fixing roller as a whole is finally formed by the step portions 1A. The outer diameter of the part is uniformly finished.

A heat-resistant insulating layer 2 is provided on the core metal 1. Examples of the material of the heat-resistant insulator include ceramic.

A resistive heating element layer 3 made of silicon carbide or the like is formed on the heat-resistant insulating layer 2, and a release layer 4 is applied thereon. The mold release layer 4 is not applied to both ends,
At both ends, the resistance heating layer 3 is exposed, forming a power receiving section 3A. Note that in the figure, only the power receiving section 3A at the left end is shown, and the power receiving section at the right end is omitted.

A power supply member 5 made of a shape memory alloy is in contact with the power receiving section 3A (the same applies to the other power receiving section). The power supply member 5 is pressed against the fixing roller in the radial direction, and due to its own elasticity comes into sliding contact with a contact pressure that does not interfere with the rotation of the fixing roller during use. The power supply member deforms in a direction opposite to the direction of the above-mentioned pressing at a certain set temperature, for example, 260° C. or higher, as shown by the two-dot chain line in FIG.
Conditions are set so that the power receiving section 3A is moved away from the power receiving section 3A.

The above set temperature is designed to prevent the surface of the fixing roller from rising excessively due to a malfunction or accident in the fixing device, temperature sensor, or the device that drives the fixing device, which could damage these devices and the fixing roller itself. This is the upper limit temperature when there is a temperature, and is at least higher than the phase transition point temperature of the power supply member 5. At that time, if the difference between the phase transition point temperature and the above-mentioned set temperature is large, it can be adjusted by adjusting the distance between the power supply member and the roller, or by providing a heat insulating means.

In this embodiment as described above, the power supply member 5
The resistive heating element layer 3 receives electric power from the heater and generates heat, raising the temperature of the fixing roller. However, when the temperature rises excessively due to some kind of failure or accident and the fixing roller reaches the upper limit temperature, the power supply member 5 As shown by the two-dot chain line in FIG. 1, it moves away from the power receiving section 3A, power supply is stopped, and the fixing roller and other devices are protected.

(Effects of the invention) As described above, the present invention provides a fixing roller having a resistance heating layer on a cylindrical base material, in which the power supply member that supplies power to the resistance heating layer from outside the fixing roller is connected to a certain amount of time. By forming the shape memory alloy so that it separates from the power receiving part when the temperature exceeds the set temperature, it becomes possible to easily suppress the temperature rise when the temperature of the fixing roller increases abnormally, and as a result, the fixing roller itself In addition, damage to other peripheral devices can be prevented, and the structure for this purpose is extremely simple and can be manufactured easily.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway perspective view showing an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Base material, 2... Heat-resistant insulating material layer, 3... Resistance heating element layer, 3A... Power receiving part, 4... Release layer, 5...
...Power supply component.

Claims (1)

[Claims for Utility Model Registration] A cylindrical base material, a surface release layer formed on the cylindrical base material, a resistance heating element layer provided between the cylindrical base material and the surface release layer, and the resistor. A fixing roller having a power receiving portion provided in a circumferential shape for energizing the heat generating layer; and a power feeding member that slides on the power receiving portion of the fixing roller and is pressed by its own elasticity in the radial direction of the fixing roller. A fixing roller device comprising: the power feeding member is made of a shape memory alloy, and is configured to deform in a direction opposite to the direction of pressure at a certain temperature or higher and separate from the power receiving portion.