JPH0212185A - Fixation device - Google Patents

Abstract

PURPOSE:To prevent the deformation of the title device in a high temperature state and the jamming of transfer paper by stopping the driving of a roll for conveying in the case of detecting that the surface temperature of a heat roll becomes a specified temperature or more. CONSTITUTION:The title device is provided with the heat roll 3 incorporating a heat generating body 2, a pressurizing roll 4 which comes into contact with the heat roll 3 and holds the paper between the heat roll 3 and itself, a detecting means 5 for detecting the surface temperature of the heat roll 3 and a driving means 21 for driving to rotate the heat roll 3 and the pressurizing roll 4. When the detecting means 5 detects that the surface temperature of the heat roll 3 becomes higher than the specified temperature, the driving means 21 is made to be stopped by a CPU 20. Thus, the deformation of the device caused by heat and the jamming of the transfer paper, etc., can be prevented.

Description

[Detailed description of the invention] □ [Purpose of the invention] (Industrial application field) The present invention relates to a fixing device for an image forming apparatus.

(Prior art) Currently, in the fixing device of an image forming apparatus using electrophotographic technology, a transfer paper is held between a heat roller with a built-in heater lamp and a pressure roller, and the toner image is melted onto the transfer paper. There's something about it that sticks.

This fixing device detects the surface temperature of the heat roller and turns on/off a solid state relay depending on the detected temperature.
A device is provided to turn it off and control the surface temperature to a temperature suitable for fixing. There is also a temperature fuse to stop the supply of current if the solid state relay is shorted, turned on, and left unattended and the temperature rises.

Conventionally, the temperature fuse of such a fixing device is gap 5.
5+a+s, there was one that would burn out when the temperature of the temperature fuse reached 169℃, but when the temperature of the temperature fuse reached 169℃,
By the time the temperature reaches 69℃, 230℃ is applied at each place where the heat roller touches.
℃ or higher, and if the conveyance operation of the transfer paper continues, the device may be deformed or the transfer paper may jam.

(Problem to be Solved by the Invention) As explained above, in the conventional fixing device, when the solid state relay is short-circuited and left on, the temperature fuse reacts and by the time it blows, the device The transfer paper becomes hot and the transfer paper continues to be conveyed, resulting in deformation of the device and jamming of the transfer paper.

Here, the present invention detects the heat roller surface temperature, and when the heat roller surface temperature exceeds a predetermined value due to a short circuit in a solid state relay, etc., the conveying operation of the transfer paper is stopped, thereby preventing thermal deformation of the device. An object of the present invention is to provide a fixing device that prevents jamming of transfer paper.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above-mentioned problems, the present invention provides a heat roller having a built-in heating element, and a pressure roller that contacts the heat roller and holds a sheet between the heat roller and the heat roller. a detection means for detecting the surface temperature of the heat roller; a drive means for rotationally driving the heat roller and the pressure roller; and a detection means for detecting that the surface temperature of the heat roller has become higher than a predetermined temperature. There is provided a fixing device characterized in that the fixing device comprises a control means for stopping the driving means when this is detected.

(Function) According to the present invention, when a detection means for detecting the surface temperature of a heat roller having a heat generating element detects a temperature higher than a predetermined temperature, the drive means for the conveyance roller is stopped, and the device operates in a high temperature state. To prevent deformation of the paper and jam of the transfer paper.

(Example) An embodiment of the present invention will be described below with reference to FIG.

FIG. 2 is a side view of the fixing device of the copying machine in this embodiment.

A heat roller 3 having a built-in heater lamp 2 as a heat generating element and a pressure roller 4 whose surface is covered with an elastic material such as rubber are provided in the middle of the fixing device 1 in pressure contact with each other. The heat roller 3 and the pressure roller 4 are rotatably supported in the directions of arrows and C shown in the figure, respectively. A member Z4 connected to the support shaft of the pressure roller 4 and a member Z3 connected to the support shaft of the heat roller 3 are connected via a spring S so that the respective rollers are pressed against each other.

A thermistor 5 is provided near the heat roller 3 as a means for detecting the surface temperature of the heat roller 3.

Furthermore, a heater lamp 2 is installed near the heat roller 3 in case the temperature control circuit using the thermistor 5 is short-circuited.
A temperature fuse 6 is provided for stopping the current supply to. In addition, around the heat roller 3,
Cleaning felts 7 and 8 for cleaning the surface of the heat roller 3 and a peeling claw 9 for peeling the copy paper from the heat roller 3 are provided. A switch 10 for detecting the conveyance of the copy sheet peeled off by the peeling claw 35 is provided downstream of the copy paper conveyance on the left side in the drawing of the peeling claw 35 . A felt roller is provided around the pressure roller 4 to clean the surface of the pressure roller 4. The felt roller 11 is coated with silicone oil.

These heat roller 3 and pressure roller 4 are driven by a plastic gear (not shown).

Next, referring to FIG. 1, a control circuit of this embodiment will be explained.

The CPU 20 controls the entire copying machine, and is composed of, for example, a microprocessor.

A driving means 21 for driving conveyance rollers and the like is connected to an output terminal of the CPU 20.

The output terminal of the first temperature detection circuit 22 is connected to the input terminal of the CPU 20 . A thermistor 5 and a resistor R1 are connected to the input terminal of the first temperature detection circuit 22. A second temperature detection circuit 23 is connected to the thermistor 5 and the resistor R1. An input terminal of a drive circuit 24 for the heater lamp 2 is connected to an output terminal of the second temperature detection circuit 23 .

The first temperature detection circuit 22 includes resistors R2 to R8 and a comparator 30, and operates on a power source DI. The first temperature detection circuit 22 detects a predetermined surface temperature of the heat roller 3 based on a change in the resistance value of the thermistor 5 using a power source D2, and sends a detection signal corresponding to the detected temperature to the CPU.
Supply to 20.

The second temperature detection circuit 23 includes resistors R12 to R16 and a comparator 31, and operates on a power source D3. Like the first temperature detection circuit 22, the second temperature detection circuit 23 detects a predetermined surface temperature of the heat roller 3 based on a change in the resistance value of the thermistor 5. Furthermore, a detection signal corresponding to this detected temperature is supplied to the drive circuit 22.

The drive circuit 24 includes a heater lamp 2, a solid state relay (hereinafter referred to as SSR) 32, a temperature fuse 6, and an AC power source 33.

5SR32 controls turning on and off of the heater lamp 2, and uses the power source D4.

Next, the operation of the above-mentioned control circuit in response to a change in the surface temperature of the heat roller 3 will be explained.

First, let the detection temperature of the thermistor 5 be, for example, 200°C,
It is assumed that the gear of the driving means for the heat roller 3 is guaranteed up to 230° C., for example. The thermistor 5 is, for example, 2
It has a characteristic of exhibiting a resistance value of 10Ω at 00°C. Resistance R
2 is set to 2Ω and the resistor R3 is set to 3Ω. Resistors R12 and R13 are set to 10Ω.

Den gDt.

The voltages of D2 and D3 are all 5v. The voltage of power source D4 is 24V.

When the surface temperature of the heat roller 3 is less than 200"C, vl is less than 2.5V. Since v2 is 2.5V, the output signal of the comparator 31 is at the rLOWJ level. In this case, the 5SR32 is in the on state. Therefore, the heater lamp 2 is turned on and heated. Since V3 is 3.OV, the output signal of the comparator 30 is also at the rLOWJ level. In this case, the CPU 20 sets the driving means 21 to normal operation.

When the surface temperature of the heat roller 3 is 200"C or more and less than 220, Vl will be 2.5V or more and less than 3.0V. Since v2 is 2.5", the output signal of the comparator 31 will be at the rHIGHJ level. .In this case 5SR32
Since the heater lamp 2 is turned off, the heater lamp 2 is turned off. V
3 is 3. Since it is OV, the output signal of the comparator 30 is at the rLOWJ level. In this case, the CPU 20 sets the driving means 21 to normal operation.

Here, due to a short circuit in 5SR32, the heat roller 3
When the surface temperature of is 220° C. or higher, VI is 3.0 V or higher. V3 is 3. Since it is ov, comparator 30
The output signal of is at rHIGHJ level. In this case CP
U20 stops the operation of the drive means 21.

Such a device can be installed without worrying about installation time or space.

Note that the present invention is not limited to this embodiment.

The set temperature controlled by the control circuit can be set depending on the material used in the fixing device. This set temperature is lower than the temperature at which the material used starts to melt due to heat.

Further, this may be used in any image forming apparatus equipped with a fixing device using a heat roller.

〔Effect of the invention〕

As detailed above, according to the present invention, when the surface temperature of the heat roller decreases due to a short circuit of the solid state relay, etc.
When the temperature exceeds a predetermined value, thermal deformation of the device, jamming of the transfer paper, etc. can be prevented.

[Brief explanation of the drawing]

1 and 2 show an embodiment of the present invention,
FIG. 1 is a block diagram of a control circuit, and FIG. 2 is a side view of a fixing device. 3...Heat roller, 5...Thermistor. 20...CPU, 21...Driving means. 22... First temperature detection circuit agent Patent attorney Nori Chika Ken Yamashita Butsuma - Fig. Fig.

Claims (1)

[Claims] a heat roller having a built-in heating element; a pressure roller that contacts the heat roller and holds the paper between the heat roller; a detection means for detecting the surface temperature of the heat roller; A drive means for rotationally driving each transport roller including a pressure roller, and control for stopping the drive means when the detection means detects that the surface temperature of the heat roller has become higher than a predetermined temperature. A fixing device characterized by comprising means.