JPS6218579A - Fixing device for electrophotographic recording device - Google Patents

Abstract

PURPOSE:To attain the excellent temperature responsibility with less heat capacity and to control properly temperature by constituting a fixing device with an exothermic roller equipped with an exothermic resistance and a thermistor on the outer peripheral surface and a temperature control circuit controlling the temperature of the exothermic resistance due to a change in the resistance value of the thermistor. CONSTITUTION:In terms of the constitution of the exothermic roller 10, a lower electrode 10, the exothermic resistance 13 and an upper electrode 14 are adhered and formed in a sandwiched shape almost on the entire outer periphery of an insulating roller 11, which is formed with a material having a high insulating coefficient. Ta2N is suitable to the exothermic resistance 13. On the upper electrode 14, an insulating coating film made of SiO2 is formed, and on its outer periphery the thermistor 16 changing its resistance value due to temperature is formed. The electrodes 12 and 14 of the exothermic resistance 14 and the those 17 and 18 of the thermistor 16 are exposed outside, and are connected to a temperature control circuit 50 through brushes 41-44.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a fixing device for an electrophotographic recording device for fixing an unfixed recorded image transferred onto recording paper by an electrophotographic process or the like. .

[Conventional technology and its problems] Many of the known fixing devices using a heating roller system have a heat source such as a halogen lamp inside the roller, and because of their large heat capacity, even when the main switch is turned on, There is a drawback that it takes a long time for the heating roller to reach a predetermined temperature at which the recorded image (unfixed toner) can be heated, melted and fixed (this is called warm-up time).

Various improvements have been made to shorten this warming-up time, one of which is JP-A-5B-123.
There is a publication No. 580. According to this, a thin layer electric resistor is formed on the outer peripheral surface of the heating roller, and the voltage applied to the thin layer electric resistor is made higher during warming up than during fixing processing. However, even with this improved conventional technology, since the heat capacity is still large, there is no change in the fact that voltage is constantly applied to the thin-layer electrical resistor even after warming up, resulting in increased power consumption.

Further, in these known fixing devices, a temperature sensor for controlling the temperature of the heat generating roller is installed at a distance from the roller surface. This is because if the temperature sensor is in contact with the roller surface, it may cause uneven temperature on the surface, or the roller surface may become tj! This is because there is an inconvenience that the temperature sensor may be damaged, and therefore, it is necessary to adjust the distance between the temperature sensor and the roller surface to a desired distance.

Furthermore, since this temperature sensor needs to be separated from the roller surface and accurately control its temperature, it is required to have excellent responsiveness. However, in this known fixing device, the surface temperature of the heat generating roller varies considerably between when it is rotating and when it is not rotating, and this temperature variation has no effect on the highly responsive temperature sensor. It tends to be easier to receive. In order to solve this problem, for example, in JP-A-56-165174, a screen is installed in front of the temperature sensor, and the screen is used to detect the temperature of the air layer on the surface of the roller, which is heated by the heat-generating roller and generates turbulence due to its rotation. I tried to minimize the impact on However, even with this, accurate temperature control is difficult, and the number of parts increases, resulting in troublesome assembly and adjustment.

[Purpose of the Invention] Therefore, the present invention has a low heat capacity and excellent temperature responsiveness.
Another object of the present invention is to provide a fixing device that can accurately control temperature.

(Means for Solving the Problems) A fixing device according to the present invention includes a heat generating roller having a heat generating resistor and a thermistor on its outer peripheral surface, and controlling the temperature of the heat generating resistor by changing the resistance value of the thermistor. The heating resistor and thermistor are both formed in the form of a thin film.

[Function] The heat generating roller of the present invention has a small heat capacity and reaches the operating temperature instantaneously. The heat generation temperature of the heat generating resistor is directly detected by a thermistor closely disposed through an insulating coating, and is fed back to a temperature control circuit to control the temperature to a desired temperature.

[Example] In FIG. 1, a heat generating roller 1o and a rotating roller 20 are installed facing each other, and while a recording paper 30 passes between them, a recorded image formed on the recording paper is fixed. Ru. The outer periphery of the rotating roller 20 is coated with an elastic material 21 such as silicone rubber. To explain the structure of the heat generating roller 10, a lower electrode 121 and a heat generating resistor 13 are arranged in a sandwich-like manner over almost the entire outer peripheral surface of the insulating roller 11.
゜The upper electrode 14 is sequentially deposited using methods such as sputtering, vapor deposition, and CVD. Insulating roller 11
is made of a material that is insulating and has a high heat insulation coefficient, such as ceramics such as Al2O3 or glass.

The material of the lower electrode 12 and the upper electrode 14 is Cu.
, Ni, Cr, etc. can be used. As the heat generating resistor 12, heat generating resistive materials used in thermal heads can be used, and for example, T a 2 N is suitable.

An insulating film 15 such as SiO2 is formed on the upper electrode 14.
is formed. A thermistor 16 whose resistance value changes depending on the temperature is formed on the outer peripheral surface of the insulating coating 15.
Its left and right ends are joined to side electrodes 17 and 18. Thermistor 17 is Nip.

CoO, MnO alone or a combination of these are formed by sputtering, vapor deposition, CVD, or other methods. As the material of the side electrodes 17 and 18, the same material as that of the electrodes 12 and 14 for the heating resistor 12 can be used. An insulating protective layer 19 made of T a 02 or the like is formed on the outer peripheral surface of the thermistor 16 to provide wear resistance.

Electrode 12.14 of heating resistor 13 and thermistor 16
The electrodes 17 and 18 are exposed to the outside and are connected to the temperature control circuit 5o shown in the second diagram via brushes 41 to 44 as an example of connection means.

In this embodiment, the temperature control circuit 50 includes a resistor 51 and a reference power source 52 . Differential amplifier 53. It is constituted by a resistor drive circuit 54. The differential amplifier 53 includes a reference power source 52.
A reference voltage of 1 is supplied to an input terminal 53a, and a voltage applied to the thermistor 16 is supplied to an input terminal 53b.
An output 53c is generated depending on the voltage difference between the two. The drive circuit 54 outputs the output 53c of the differential amplifier 53.
The voltage to be applied to the heating resistor 13 is generated in accordance with the voltage. Further, the drive circuit 54 is configured to operate only when receiving a printing command from the main body of the electrophotographic recording apparatus (not shown) or a computer to which it is connected.

Next, the operation of the fixing device according to the present invention will be explained.

In the fixing device according to the present invention, even when the main switch is turned on, the heat generating roller 10 shown in the first figure is not immediately driven and does not start rotating. When a printing command is issued from the main body of the electrophotographic recording apparatus or the computer to which it is connected, the heat generating roller 10 and rotating roller 20 shown in the first figure are activated, and the drive circuit 54 shown in the second figure is also put into operation. That is, the drive circuit 54 via the brushes 41, 42
The voltage generated by the electrode 1 of the heating resistor 13
By being supplied between 2.14 and 14, the heating resistor 13
generates Joule heat. At first, thermistor 16
has a high resistance value, and the voltage at the input terminal 53b is sufficiently higher than the reference voltage at the input terminal 53a, so the differential amplifier 53
The voltage of the output 53c is also high (and accordingly, the voltage of the drive circuit 54
also generates high voltage. As a result, the heating resistor 13 is rapidly warmed up. As the temperature of the heating resistor 13 increases, the resistance value of the thermistor 16 decreases, and the voltage difference between the input terminals 53a and 53b of the operational amplifier 53 decreases. As a result, the voltage at the output 53c of the differential amplifier 53 also becomes low, and balance is maintained when the heating resistor 13 reaches a desired temperature. In this way, a high voltage is applied to the heating resistor 12 at first, and as the temperature rises, the applied voltage is reduced to maintain the desired temperature. The rise time to reach the desired temperature is much shorter than in known fixing devices. As the heat generating roller 10 rotates, the recording paper 30 passes between the heat generating roller 10 and the rotating roller 20, and the recorded image is fused and fixed onto the recording paper 30.

Note that the present invention is specified only by the scope of the claims, and various modifications can be made without departing from the technical idea thereof.

For example, the electrodes 12.14 of the heat generating resistor 13 may be comb-like shaped coplanarly formed on the outer peripheral surface of the insulating roller 11, and the electrodes 17.18 of the thermistor 16 may also be formed on the outer peripheral surface of the insulating roller 11. The thermistor 16 as the electrode 12゜14
It may also have a structure in which it is sandwiched. Furthermore, it is also possible to arrange the thermistor 16 below the heating resistor 13. Further, in the above embodiment, the thermistor 16 is provided over the entire region of the heating resistor 13, but it may be provided only partially.

[Effects of the Invention] The fixing device of the present invention has a small heat capacity and excellent temperature responsiveness, so warming-up is unnecessary and low power consumption can be achieved. In addition, since the thermistor that detects the heat generation temperature of the heat generation roller is placed directly on the heat generation roller, there is no air layer between the thermistor and the heat generation roller as in the conventional case, and therefore accurate and High-speed response temperature control is possible.

[Brief explanation of the drawing]

FIG. 1 is a partially sectional front view of a fixing device according to the present invention, and FIG. 2 is a temperature control circuit diagram. 10... Heat generating roller 13... Heat generating resistor 16.
...Thermistor 41-44... Connection means (brush) 50... Temperature control circuit 52... Base $ power supply 5
3...--Operation amplifier 54...Resistor drive circuit amount Top

Claims (2)

[Claims] (1) An electronic device comprising: a heat-generating roller having a heat-generating resistor and a thermistor on its outer peripheral surface; and a temperature control circuit that controls the temperature of the heat-generating resistor by changing the resistance value of the thermistor. Fixing device for photographic recording equipment. (2) In claim 1, the heating control circuit includes a differential amplifier to which a reference voltage and a variable voltage applied to the thermistor are supplied, and a resistor that drives the heating resistor in response to the output thereof. A fixing device for an electrophotographic recording device, which includes a body drive circuit.