JPH0736098B2 - 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 an unfixed image on a recording material by passing a recording material having an unfixed image on its surface between fixing rollers. Thus, for example, it can be used for fixing a toner image in electrophotographic recording or fixing ink for transfer thermal recording.

[Background of the Invention]

When the unfixed image is heated and fixed on the recording material by the fixing device of the above type, depending on the fixing condition, particularly the humidity condition,
Wrinkles may occur on the recording material. As a conventional measure for preventing this type of wrinkles, a method has been used in which the outer peripheral shape of the fixing roller is manufactured in advance into an inverted crown shape, and the peripheral speed at both ends is increased to absorb the expansion of both sides of the recording paper at high humidity. ing.
However, according to such a method, depending on the environmental conditions, especially in low humidity conditions, the recording material may have a small amount of elongation on both sides and tend to contract. Therefore, the transferred image on the recording material may be deformed. In addition, similar defects may occur depending on the type of recording material, such as the material, thickness, and shape.

[Object of the Invention]

An object of the present invention is to eliminate the drawbacks of the conventional fixing device as described above, without causing wrinkles on the recording material or deformation of the unfixed image on the recording material even when the fixing conditions change. An object of the present invention is to provide a fixing device capable of heating and fixing an unfixed image on a recording material.

[Outline of Invention]

The fixing device according to the present invention includes a heating roller having a plurality of heaters each having a different heat distribution inside, and a pressure roller in pressure contact with the heating roller, and an unfixed image is carried by the pressure contact portion of the roller. In a fixing device for nip-conveying and fixing the recording material, a humidity sensor for detecting the humidity is provided, and energization control of a plurality of heaters of the heating roller is switched according to information from the humidity sensor to determine the outer diameter of the roller. It is characterized by changing the shape. In particular,
By controlling the energization of these heaters based on the information from the humidity sensor, the occurrence of wrinkles under low humidity conditions is prevented.

Example of Invention

Hereinafter, the present invention will be described in detail with reference to the embodiments shown in the drawings.

FIG. 1 is a view showing an embodiment of the present invention, in which 1 is a recording paper, 2a and 2b are a pair of fixing rollers which are pressed against each other, and 3a and 3b are arranged in the fixing roller 2a. Two heat source heaters having different heat distributions. 2a of a pair of fixing rollers
Is a heating roller heated by the above heater,
2b is a pressure roller.

The recording paper 1 is fed between the fixing rollers 2a and 2b in a state where an unfixed image, for example, a toner image is supported on the surface, the image is fixed by the fixing roller, and then the recording paper 1 is sent out from the roller.

2 is a schematic block diagram of the apparatus shown in FIG. 1, 4 is a switch for controlling the energization of the heaters 3a and 3b, 5 is a control circuit for the switch 5, 6 is a humidity sensor for detecting humidity, and 7 is a heater. Power source. In the above structure, the fixing roller 2a is heated by the built-in heaters 3a and 3b to fix the transferred image on the recording paper as a heat roller, but the outer diameter shape of the fixing roller is affected by thermal expansion due to heating from the heater. Here, the heat distribution distribution characteristics of the heaters 3a and 3b are configured, for example, as shown by curves 8a and 8b in FIG. 3, respectively, and when these heaters are individually energized or controlled simultaneously or alternately, fixing is performed. The outer diameter shape of the roller 2 changes as shown in FIG. In FIG. 4, 9a shows the outer diameter shape of the roller when only the heater 8a is used, 9b when only the heater 8b is used, and 9c when the heaters 8a and 8b are simultaneously or alternately energized. Further, the roller shape before heating is as shown in 9a.

In the illustrated embodiment, the control circuit 5 controls the energization of the heater in response to a signal from the humidity sensor 6. The heater 3a is selected when the humidity is high and the heater 3b is selected when the humidity is low. When wet, the heaters 3a and 3b are alternately energized and controlled. Due to this energization control, the roller shape changes as described above, becoming an inverted crown shape when the humidity is high, a crown shape when the humidity is low, and a flat shape when the humidity is moderate. It becomes possible to carry out fixing without the need.

In the above example, the fixing operation was performed under the following conditions. As the fixing roller 2a, a 2 mm-thick aluminum pipe coated with Teflon and having a flat outer diameter of φ30 when not heated was used. Also heater 3a
The heat distribution of the fixing roller is set so that the humidity distribution of the fixing roller is about 30 ° C. higher than the central portion at both ends in the longitudinal direction of the roller. At this time, the reverse crown amount of the fixing roller is It was about. The heat distribution of the heater 3b is set so that the central portion of the fixing roller is higher than the end portion by about 15 ° C.
The crown amount was about 0.01 mm. In the embodiment, the switching of the energization control of the heater is performed by alternately switching the energization of the heaters 3a and 3b when the relative humidity is 70% or more by the output of the humidity sensor in the high humidity mode, 30% or less in the low humidity mode, and 30 to 70%. As done. As a result, even if the humidity condition changes, it is possible to perform fixing without causing wrinkles and without changing the fixed image. Although the heater energization control is performed according to the signal from the humidity sensor in the above embodiment, other fixing conditions, for example, the type of recording material, such as paper material, thickness, and shape information, are used. It is also possible to perform control according to these. In addition, it is of course possible to control the optimum fixing temperature distribution according to various fixing conditions depending on the paper type and the like by controlling a plurality of heaters having different heat distributions.

〔The invention's effect〕

As described above, the fixing device according to the present invention detects the humidity condition and other fixing conditions, controls the energization of the fixing heater, and controls the shape of the fixing roller in accordance with the above condition, thereby changing the humidity difference. The shape of the fixing roller can be adapted to the deformation of the recording material due to the difference in other conditions, and the fixing can be performed without wrinkles.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a fixing device according to the present invention, FIG. 2 is a block diagram thereof, FIG. 3 is a view showing a heat distribution of a heater, and FIG. 4 is a shape change due to thermal expansion of rollers. FIG. 1 ... Recording paper, 2a, 2b ... Fixing roller, 3a, 3b ... Heat source heater, 4 ... Switch, 5 ... Energization control circuit, 6 ... Humidity sensor, 7 ... Power supply.

Claims (1)

[Claims] 1. A recording comprising a heating roller having a plurality of heaters each having a different heat distribution inside, and a pressure roller in pressure contact with the heating roller, wherein an unfixed image is carried at a pressure contact portion of the roller. In a fixing device for sandwiching and conveying a material for fixing, a humidity sensor for detecting humidity is provided, and energization control switching of a plurality of heaters of the heating roller is performed according to information from the humidity sensor to change the outer diameter shape of the roller. A fixing device characterized by being changed.