JPH01185573A - Oven fixing device - Google Patents

Abstract

PURPOSE:To prevent a heat source from being partially made into a high temperature by dividing the heat source of an oven fixing device in a paper carrying direction, and controlling the temperature of each individually. CONSTITUTION:A first heater 2 and a second heater 6 are individually temperature-controlled, and the maximum energy consumption of each can be also individually controlled. Namely, the heat source is divided in the paper carrying direction, and in the divided parts, an input heat quantity to the part at a paper inlet side to which a net belt 13 to be cooled is successively fed and the input heat quantity to the part of a paper outlet side to which the heated net belt 13 is fed are made different. Thus, the heaters 2 and 6 can be prevented from being partially made into the high temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an oven fixing device used in image forming devices such as copying machines and printers.

BACKGROUND OF THE INVENTION For example, in a film electrophotographic copying machine, an electrostatic latent image formed on a photoreceptor is developed into a toner image, and this toner image is used as a transfer material (represented by the paper in this mttusa). After being transferred to a computer, it is fixed and a copy is obtained. Practical conventional means are mostly based on heat and/or pressure, and a typical example is an oven fixing device that heats the toner mixture using radiant heat and convection heat from a heating element placed opposite to the conveyed paper. Also known is a heat roll fixing device in which a sheet is guided between a pair of heat rolls that rotate while being in pressure contact with each other. Among these, the non-contact type oven fixing device is often used particularly in copiers for large-sized drawings because it does not cause mechanical deformation such as wrinkles on the paper after fixing.

FIG. 4 is a diagram for explaining an example of a conventional oven fixing device. This oven fixing device has flat plate heaters 62 and 64 arranged in parallel above and below the transport surface of the paper 60.
A heat-resistant net belt 74 for conveying 0 is wound between the driving sprocket 66 and the driven rollers 68, 70, and 72. The paper 60 carried in passes between the flat heating plates 562 and 64 as the net belt 74 rotates, and the toner @76 on the paper 60 is fixed by radiation and convection heating at this time.

1 In the conventional oven fixing device described above, in order to maintain a constant temperature, temperature is detected at an appropriate point in the heating section (for example, approximately at the center of the heater in the paper conveyance direction).
i+1jtllll was set so that the heating temperature was approximately constant. However, in general, oven constant temperature is set at a relatively low temperature (e.g. 350°C) to avoid the risk of overheating of paper undesirably accumulated between the heaters. Since the net belt having an appropriate heat capacity is cooled at a portion other than the heated portion and is sequentially sent between the heaters, the mrtj control at the above-mentioned point - is as follows. There was an inconvenience that the temperature at the paper inlet side was lower than the set temperature, and the temperature at the paper outlet side was higher than the set temperature. For this reason, even though the heater has been made longer to avoid danger, the heater partially reaches a high temperature (on the paper exit side), and when paper jams occur in this area, the paper will smoke.
In severe cases, there is a danger that the paper may catch fire.

The present invention was created in view of these circumstances, and its purpose is to partially heat the heater. To provide an oven fixing device which prevents the temperature from reaching 3 degrees.

Steps to Solve the Problems The oven fixing device of the present invention, which has been made to solve the problems of the prior art described above, divides the heat source for radiant and convection heating in the paper conveyance direction. The temperature of each part of the heated heat source is individually controlled.

Function In the present invention, the heat source is divided in the paper conveyance direction. Among the divided parts, the cooled net belt is successively fed into the part on the paper entrance side, and the heated net belt is heated. This is to enable the amount of heat input to the portion on the exit side of the paper being fed to be different, and to eliminate the drawbacks of the above-mentioned prior art due to the heat input being uniform in the paper conveyance direction.

Back-”L-1 Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a sectional view of an oven fixing device constructed to which the present invention is applied. Inside this oven fixing device, a flat plate-shaped first heater 2 and a second heater 6 are provided in this order in the paper conveyance direction. The first heater 2 is the upper frame 1
Consisting of a heater 2a fixed to 0 and a heater 2b fixed to the lower frame 12, these heaters 2a, 2b
share the heater wire 4. The second heater 6 consists of a heater 6a fixed to the upper frame 10 and a heater 6b fixed to the lower frame 12.
6b shares the heater wire 8.

The net belt 13 for conveying the paper has a drive sprocket 14, a driven roller 16,
Kake was passed on 18.20 respectively. The drive sprocket 14 is rotated counterclockwise in the figure, and the net belt 13 is also rotated counterclockwise accordingly. The net belt 13 is desirably mesh-shaped in view of heat transfer requirements, and is preferably sufficiently small in view of safety constraints. Further, the material of the net belt 13 is preferably a liquid crystalline polymer such as Kevlar (trade name) or glass fiber in consideration of its heat resistance and exposure of the heater wire. Reference numerals 22 and 24 denote paper suction ducts fixed to the paper inlet side and the paper outlet side of the lower frame 12, respectively, and the conveyed paper is attracted to the net belt 13 by creating negative pressure inside these ducts. There is. In addition, 3
Reference numeral 0 indicates a paper guide (not shown) for guiding the paper from a transfer device to the fixing device, and 324 indicates a paper output tray.

In the above configuration, the temperatures of the first heater 2 and the second heater 6 are individually controlled, and in this embodiment, the maximum power consumption can also be individually controlled. The control method for the first heater 2 will be explained below, but the second heater 6 can also be controlled in a similar manner.

FIG. 2 is a block diagram of a control circuit for the first heater 2. As shown in FIG.

34 is a power source for energizing the heater 14; 36 is a switching element such as a triac that turns on and off the heater circuit; 38 is a voltage detector applied to the heater wire 4; and 39 is a current flowing through the heater wire 4. 40 is a multiplier that receives the outputs of the voltage and current detectors 38 and 39;
2 is a comparator that compares the signal level corresponding to the power setting value and the output level of the multiplier 40 and outputs a power difference signal; 4;
4 is a temperature sensor provided near the heater wire 4; 46 is a temperature controller that compares the output level of the temperature sensor 44 with a signal level corresponding to a temperature set value and outputs a temperature difference signal; 48 is a power difference An AND gate 50 to which the signal and the temperature difference signal are input is a control circuit for the switching element 36.

The multiplier 40 outputs the product of the voltage and current of the heater wire 4, ie, a power signal, which is compared with a set maximum power value by the comparator 42. If the power consumption in the heater wire 4 is smaller than the set maximum power, the difference signal becomes positive and the AND gate 48 is opened. Therefore, if the temperature of the heater wire 4 is below the set value, the output of the temperature controller 46 is supplied to the control circuit 50, the switching element 36 is turned on, and ff1R is supplied to the heater wire 4. Further, when the temperature of the heater wire 4 exceeds the set value, the output of the temperature controller 46 disappears, the switching element 36 is turned off, and the current supply to the heater wire 4 is stopped. - On the other hand, if the power consumption in the heater wire 4 increases due to an increase in the power supply voltage or a decrease in the resistance value of the heater wire 4, the power difference signal from the comparator 42 becomes negative and the AND gate 48 is closed. . Therefore, regardless of the temperature of the heater wire 4, the switching element 36 is turned off and the supply of current to the heater wire 4 is stopped.

FIG. 3 shows the positive input (a), negative input (b), output (C), and heater of the comparator 42 when the set power value signal to the comparator 42 in FIG. 4 is a sawtooth wave. FIG. 4 is a diagram showing the phase relationship of the current (d) supplied to line 4; The energization time to the heater wire 4 is controlled before and after the actual power consumption changes (Ll).

In this way, in this embodiment, the maximum power consumption is also individually controlled for the first heater 2 and the second heater 6, so for example, the set power value of the first heater 2, which requires a relatively large amount of power, can be adjusted. By setting an appropriate ratio (for example, 6:4) between the power consumption and the set power value of the second heater 6, which does not require a relatively large amount of power, a steady state can be maintained from the time the power is turned on, even if the total power consumption is limited. This makes it possible to reduce the time it takes.

Note that the multiplier 40 in FIG.
An adder may be used, provided that the signal levels from 8.39 are approximately equal. This is because under such conditions, the power consumption error is as small as 1% or less.

In the above description, the heat source is divided into two parts, but the present invention is not limited to this, and the heat source may be divided into three or more parts.

Effects of the Invention As detailed above, according to the present invention, the heat source of the oven fixing device is divided in the paper conveyance direction and the temperature is controlled individually for each, so that the heat source becomes partially high temperature. As a result, the danger caused by overheating of paper undesirably staying inside the fixing device can be avoided. Further, the entire fixing device can be brought into a steady state (warm-up completed) in a minimum amount of time.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional configuration diagram of an oven fixing device showing an embodiment of the present invention, Fig. 2 is a block diagram of a control circuit of the heater in Fig. 1, and Fig. 3 is a control circuit according to the control circuit shown in Fig. 2. FIG. 4 is an explanatory diagram of a conventional oven fixing device. 2... First heater, 6... Second heater, 13
... Net belt, 14... Drive sprocket. Applicant: Fuji Xerox Co., Ltd.

Claims (1)

[Scope of Claims] An oven fixing device comprising a non-contact type heat source that heats an unfixed toner image by radiation and convection, and means for conveying paper along the heat source, wherein the heat source is directed in the paper conveyance direction. An oven fuser characterized by dividing the heat source and individually controlling the temperature of each part of the divided heat source.