JPH01307785A - Fixing device of electrophotographic printer - Google Patents

Abstract

PURPOSE:To improve fixing performance by constituting a heating unit which heats a heater roll with the combination of plural plus temperature coefficient thermistors which are electrically connected in parallel to a constant voltage source. CONSTITUTION:The heating unit is constituted by combinating the plural plus temperature coefficient thermistors 2 which are electrically connected in parallel to the constant voltage source 3. The plus temperature coefficient thermistors 2 are disposed in file in the direction of the length of the heater roll 1, and the thermistors 2 are loaded in the way that they come in contact with the inner peripheral surface of the heater roll 1. If the surface temperature of the part of the heater roll1 is lowered due to printing sheet inhalation and so on, the electric resistance of the plus temperature coefficient thermistor 2 which is situated at the part is lowered and an electric current flowing the part is increased. Resultantly, temperature rises and the temperature of the heater roll 1 is partially corrected. Thus the fixing performance is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrophotographic printer, and more particularly to a fuser thereof.

[Conventional technology]

Conventionally, the fixing device of this type of electrophotographic printer has used a single halogen lamp or heating wire as a heating element.

[Problem to be solved by the invention]

The fuser of the conventional electrophotographic printer mentioned above uses a single halogen lamp or heating wire as a heating element, so when correcting a local temperature drop, the overall temperature rises. , good printing could not be obtained.

An object of the present invention is to provide a fixing device for an electrophotographic printer that solves the above problems.

[Means to solve the problem]

To achieve the above object, the present invention provides a fixing device for an electrophotographic printer that includes a heater roll and a heating element that heats the heater roll, in which the heating element is electrically connected in parallel to a constant voltage source. It is constructed by a combination of a plurality of positive temperature coefficient thermistors.

〔Example〕

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

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a temperature-resistance characteristic diagram of a positive temperature coefficient thermistor.

In the figure, the present invention constitutes a heating element by combining a plurality of positive temperature coefficient thermistors 2゜2... electrically connected in parallel to a constant voltage source 3, and the positive temperature coefficient thermistors 2 are connected to a heater roll 1 They are arranged in rows in the length direction. The thermistor 2 is attached so as to be in contact with the inner peripheral surface of the heater roll 1.

In the present invention, the heater roll 1 is
When the surface temperature of a part of the positive temperature coefficient thermistor 2 decreases, as shown in Figure 2, the electrical resistance of the positive temperature coefficient thermistor 2 at that location decreases, the current flowing there increases, and as a result, the temperature increases. , the temperature of the heater roll 1 is partially corrected.

〔Effect of the invention〕

As explained above, the present invention uses a positive temperature coefficient thermistor and a constant voltage source that are electrically connected in parallel to generate heat in the fuser, thereby causing a local temperature drop to affect the part of the pond. This has the effect of improving fixing performance.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram showing an embodiment of the present invention, and Fig. 2 is a temperature-resistance characteristic diagram of a positive temperature coefficient thermistor. voltage source

Claims (1)

[Claims] (1) In a fixing device for an electrophotographic printer that has a heater roll and a heating element that heats the heater roll, the heating element is connected to a plurality of positive temperature coefficient thermistors electrically connected in parallel to a constant voltage source. A fixing device for an electrophotographic printer, characterized in that it is configured by a combination of the following.