JP2945214B2 - Copier fixing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device for an electrophotographic copying machine, and more particularly to a fixing device for detecting the temperature of a fixing roller. The present invention relates to a fixing device that is forcibly displaced in a direction approaching a fixing roller, that is, on a safe side even when deformed.

[0002]

2. Description of the Related Art An electrostatic electrophotographic copying machine forms an electrostatic latent image corresponding to a document image on a cylindrical or belt-shaped photosensitive member having a uniformly charged surface. This is an image processing apparatus which develops an image by electrostatically attaching a developer, fixes the image on transfer paper, and visualizes the image. The electrostatic latent image on the photoreceptor
First, a document is placed on a document table made of hard transparent glass or the like, and the placed document is scanned with light irradiation from the back side, and reflected light from the document by the light irradiation light is previously exposed through an exposure optical system. It is obtained by forming an image on an electrostatically charged photoconductor. Next, the electrostatic latent image on the photoreceptor is used as a developer (toner).
, And the developed toner image is transferred onto a transfer sheet by a transfer roller that rotates while being pressed against the photoconductor, and then is heated and fused by a fixing device to fix the image on the transfer sheet.

As described above, the fixing device heats the toner image transferred onto the transfer paper and fuses the toner image onto the transfer paper. As a heating method, a heating means is used with or without bonding to the transfer paper. However, a heat roller fixing method is generally employed. The heat roller fixing method has a heater on a shaft, a fixing roller heated to a constant temperature by the heater, and a pressure roller that rotates while being pressed against the fixing roller in an axis parallel to the fixing roller. This is a fixing method in which the sheet is nipped and heated between the fixing roller and the pressure roller to be transported. The fixing temperature is maintained at a constant temperature by detecting the temperature of the surface of the fixing roller with a thermistor or the like and controlling the heater lamp current in the fixing roller based on the detected temperature. However, in the case where the thermistor fails and the temperature rises, a thermostat is separately provided to detect the surface temperature of the fixing roller, and when the temperature rises to the thermostat set temperature, the heater lamp current is cut off. The thermostat is attached to a sheet metal, and the sheet metal is mounted on a frame of the fixing device. However, a sheet metal to which a thermostat is attached is expensive and is not suitable for weight reduction, and a resin material has been used instead of the sheet metal.

[0004]

If the substrate on which the thermostat is to be mounted is made of a resin material, if the normal temperature control becomes impossible, the variation in the set temperature of the thermostat becomes a problem. That is, the resin substrate has a larger coefficient of thermal expansion than metal and is deformed when given heat is applied. If the variation in the set temperature of the thermostat is higher than the shut-off temperature, the substrate is thermally deformed, and if the substrate approaches the side closer to the fixing roller, the thermostat operates at a lower temperature than when the temperature of the fixing roller is at the initial position. In this case, the current is cut off, so the operation is on the safe side.On the other hand, if the fixing roller is deformed away from the fixing roller, the temperature of the fixing roller will increase, so the heating current must be cut off with a delay. This causes problems in safety and transferred image quality. The present invention
To provide a fixing device that does not cause such a problem.
And its purpose.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and (1) a fixing roller having a built-in heater for heating and fixing a toner image on a transfer sheet and transporting the toner image; A pressure roller that is pressed against the roller and rotated, and a resin
A plate-shaped member having a U-shaped cross section is formed using a material, and
The fixing surface is opposed to the fixing roller at a certain interval .
Secure the legs on both sides to the cabinet
And the chassis facing the fixing roller .
A temperature sensor disposed on the upper surface and heating of the fixing roller;
As a result, when the chassis using the resin material is deformed , an action force for pressing the temperature sensor toward the fixing roller is generated.
A spring extending in the vicinity of the temperature sensor having a function of forcing the deformation to the fixing roller side, and a switch for shutting off a heating power supply of the heater when a temperature detected by the temperature sensor exceeds a predetermined temperature. (2) In the above (1), the temperature sensor
Is a thermostat, and approximately at the center of the upper surface of the chassis
It is characterized by being arranged in .

[0006]

A temperature sensor such as a thermostat is provided on a resin material substrate at a fixed distance from the fixing roller to control the heating current of a heating heater in the fixing roller to make the temperature of the fixing roller constant. At this time, even if the substrate of the resin material is deformed due to the heating of the fixing roller, the substrate is forcibly deformed toward the fixing roller, thereby speeding up the thermal response of the temperature sensor.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a copying machine to which the present invention is applied will be described. FIG. 2 is a front sectional view for explaining an example of a copying machine according to the present invention. In the drawing, reference numeral 21 denotes a copying machine main body (cabinet); Is a rod lens array, 26 is a charger, 2
7 is a photoreceptor roller, 28 is a developing device, 29 is a paper feed unit, 3
0 is a registration roller, 31 is a transfer roller, 32 is a toner storage unit, 33 is a cleaning device, 34 is a fixing roller,
35 is a pressure roller, and 36 is a temperature sensor.

[0008] In FIG.
A movable document table 22 to be described later is installed, and a document 23 is placed on the document table 22. The original 23 is illuminated from below by an illumination lamp 24, and reflected light from the original 23 is condensed by a rod lens array 25 to expose the surface of a photoreceptor roller 26. The surface of the photoreceptor roller 26 is uniformly charged by the charger 26, and an electrostatic latent image is formed on the surface of the photoreceptor roller 26 by exposing the original 23 to the rod lens array 25. The electrostatic latent image is developed by electrostatic attraction by receiving a developer (toner) 28a stored in the developing device 28 from the developing device 28, and a toner image corresponding to the electrostatic latent image is formed. Is done. The toner image is transferred onto a transfer sheet by a transfer roller 31 that rotates in contact with the axis of the photosensitive roller 27 in parallel with the axis. The transfer paper is conveyed from a manual paper feed unit 29 and is locked by registration rollers 30. The transfer paper is unlocked in synchronization with the formation of the toner image, and is inserted between the photosensitive roller 27 and the transfer roller 31 to transfer the toner image onto the transfer paper. The transfer paper is heated and fixed by the toner of the transfer image conveyed between the fixing roller 34 heated to a fixed temperature via the temperature sensor 36 and the pressure roller 35 and discharged.

After the transfer, the toner adheres to the transfer roller 31, but the toner remains on the surface of the transfer roller 31 by applying a voltage having a polarity opposite to that of the toner charge charged to the transfer roller 31 to the transfer roller 31. The accumulated toner moves to the photoconductor roller 27. The toner that has moved to the photoconductor roller 27 is removed by the cleaning device 33 together with the toner remaining on the photoconductor roller 27, and the toner is stored in the toner storage unit 32.
Is stored inside. Thereafter, the surface of the photoreceptor roller 31 is irradiated with direct light from the irradiation lamp 24 to uniformly remove electricity from the surface.

FIG. 3 is a perspective view for explaining a platen moving mechanism of the copying machine according to the present invention. In FIG. 3, reference numeral 38 denotes an endless gear, 38a and 38b denote rack gears, 39 and 40 denote planetary gears, and 41 denotes a planetary gear. Drive gear.

The original table moving mechanism shown in FIG. 3 is for reciprocating the original table 22 shown in FIG. 2 horizontally. The original table 22 is driven by an endless gear 38. Rack gears 38 having different pitches are provided on the inner circumference of the endless gear 38.
a and 38b are formed, and the rack gears 38a and 38b mesh with one of the planetary gears 39 and 40 driven by the drive gear 41, so that the endless gear 38 is moved. Since the pitches of the rack gears 38a and 38b are different, the endless gear 38 is driven by the driving gear 41 having a constant rotation, so that the movement of the endless gear 38 has two stages, and the document table 22 is moved at different speeds during feed and return. be able to.

FIG. 1 is a front view for explaining an embodiment of a fixing device of a copying machine according to the present invention. In the drawing, reference numeral 1 denotes a cabinet upper surface, 2 denotes a cabinet bottom surface, 3 denotes a chassis, 4 denotes a pressing spring, 5 is a thermostat, 6 is a thermistor,
7 is a fixing roller, 8 is a heater lamp, 9 is a terminal, 10
Denotes a pressure roller, 11 denotes a fixing roller gear, 12 denotes a pressure roller spring, and 13 denotes a pressure roller bearing.

In FIG. 1, a fixing roller 7 has a coaxial fixing roller gear 11 which is rotatably driven at one end of the fixing roller 7, is a cylindrical body whose outer peripheral surface is processed with a fluorine resin, and is not in contact with an axial line. Is provided with a heater lamp 8. Also,
The fixing roller 7 is provided with a pressure roller 10
Are pressed by a pressure spring 12 and are rotatably disposed around a pressure roller bearing 13. The fixing roller 7
And the pressure roller 10 are provided between the cabinet upper surface 1 and the cabinet bottom surface 2 of the cabinet.
It is arranged through. The chassis 3 includes side plates 3a, 3
a plate-like body section U-shaped consisting of a and the upper plate 3b, the side plates
3a, the end of 3a as a leg, and the bottom of the cabinet
It is fixed to the surface 2 . The upper plate 3b of the chassis 3 is provided with a thermostat 5 in the approximate center and a thermistor 6 in the vicinity of the end, facing the fixing roller 7 at a slight center in parallel with the axis of the fixing roller 7. Further, pressing springs 4 and 4 are stretched between the upper surface of the cabinet in the vicinity of the thermostat at the center to apply a spring force for pressing the chassis 3 provided with the thermostat 5 toward the fixing roller 7. .

In the fixing device configured as described above,
The fixing roller 7 is heated by a heat source of a heater lamp 8 which is heated by a power supply applied via terminals 9 and 9.
The temperature is detected by the thermistor 6, and the current of the heater lamp 8 is controlled by a heater lamp control circuit described later, so that the surface temperature of the fixing roller 7 is kept constant. However, even when the temperature of the fixing roller 7 rises due to the malfunction of the temperature control system and the chassis 3 is deformed, the thermostat 5 is displaced toward the fixing roller 7 due to the spring force of the holding spring 4. That is, the thermostat 5 moves to the safe side as described above.

A specific resin material of the chassis 3 is, for example, a polycarbonate resin, and its heat-resistant temperature is 145 ° C.
The thermostat 5 is placed 0.75 m from the surface of the fixing roller 7.
m at a distance. For example, thermostat 5
When the temperature setting was 140 ° C., the surface temperature of the fixing roller was about 170 to 180 ° C. When the thickness of the resin material is set to 2.5 mm so that the chassis 3 is easily deformed by heat, the following specifications are suitable for the pressing spring 4. Material SUSWPB (stainless steel wire) Wire diameter 1.0mm Outside diameter 10.0mm Effective number of turns 13.5 Free length 31.2mm Load length 20mm Load 1.0kgf

FIG. 4 is a diagram showing an example of a control circuit for a heater lamp of a fixing device of a copying machine according to the present invention.
3 is a CPU (Central Processing Unit), 54 is a triac, 55 is a comparison unit, 58 is a signal line, 59 is a thermostat, 60 is a DC amplifier, and 61 is a phototriac coupler.

In FIG. 4, first, the surface temperature of the fixing roller 7 is detected by the thermistor 50, and the temperature is converted into a voltage based on a change in resistance between the resistors 51 and 52 and the thermistor 50, and this voltage is read by the CPU 53. . CPU
53 outputs a signal 58 to control the gate G of the triac 54 via the DC amplifier 60 and the opto-triac coupler 61 so that the surface temperature of the fixing roller 7 becomes 14
The current of the heater lamp 8 is ON-OFF controlled at the power supply frequency so as to maintain 3 ° C. If an abnormality occurs in the heater lamp 8, the CPU 53 sends a command to cut off the current of the heater lamp 8 until the surface temperature of the fixing roller 7 reaches 160 ° C. Further, when the CPU 53 goes out of control, the voltage of the thermistor 50 based on the temperature detection is compared with the reference voltage divided by the resistors 56 and 57 by the comparing unit 55. When the temperature detected by the thermistor 50 reaches a voltage corresponding to 180 ° C., the CPU 53 sends a signal for dropping the signal on the signal line 58 to Low and shutting off the power of the heater lamp 8. Also, the terminal T _{1 of the} triac 54
And short-circuited between terminals T _2, such as when it becomes uncontrollable, resulting poor attachment of the thermistor 50, if such detected temperature changes, the triac 54 connected in series with thermostat 59 detects the abnormal temperature And shut off the power.

FIG. 5 shows a flowchart of the heater lamp control circuit shown in FIG. 4 in the present invention. After turning on the power of the heater lamp 8, step 1 : check whether the surface temperature of the fixing roller 7 is 143 ° C. or more. step 2 : If it is 143 ° C. or lower, the heater lamp 8 is turned on
(Closed), step 3 : If the temperature is 143 ° C. or higher, the heater lamp 8 is turned off.
F (open). step 4 : Fixing roller 7 with heater lamp 8 off
It is checked whether the surface temperature is 137 ° C. or lower. step5 : When the temperature falls below 137 ° C., the heater lamp 8 is turned on until the surface temperature of the fixing roller 7 becomes 143 ° C. or higher.
Continue the state of.

FIG. 6 is a flowchart of the thermostat of the heater lamp control circuit shown in FIG. 4 according to the present invention. step 1 : It is detected whether the detected temperature of the thermostat 5 at a fixed distance from the fixing roller 7 is 140 ° C. or lower, and if it is, the thermostat 5 continues to be ON. step 2 : When the temperature rises to 140 ° C or higher, the thermostat 5 becomes O
It becomes FF, and the heating current of the heater lamp 8 is cut off.

[0020]

As is apparent from the above description, according to the present invention, the temperature control system for heating the surface temperature of the fixing roller to a predetermined temperature breaks down and faces the fixing roller as protection means against a rise in temperature. The thermostat installed on the resin chassis has a variation in the set operating temperature, and even if the chassis is deformed, the thermostat must be displaced in a safe direction closer to the fixing roller due to spring force, so it is an inexpensive and safe fixing device It can be.

[Brief description of the drawings]

FIG. 1 is a front view for explaining an embodiment of a fixing device of a copying machine according to the present invention.

FIG. 2 is a front sectional view for explaining an example of a copying machine according to the present invention.

FIG. 3 is a perspective view for explaining a document table moving mechanism in an example of the copying machine according to the present invention.

FIG. 4 is a diagram showing an example of a control circuit of a heater lamp of the fixing device of the copying machine according to the present invention.

FIG. 5 is a diagram showing a flowchart of a heater lamp control circuit shown in FIG. 4;

6 is a diagram illustrating a flowchart of a thermostat of the heater lamp control circuit illustrated in FIG. 4;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Cabinet top surface, 2 ... Cabinet bottom surface, 3 ... Chassis, 4 ... Holding spring, 5 ... Thermostat, 6
... Thermistor, 7 ... Fixing roller, 8 ... Heater lamp, 9
... Terminals, 10 ... Crimping rollers, 11 ... Fixing roller gears, 1
2 ... Crimping roller spring, 13 ... Crimping roller bearing.

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G03G 13/20 G03G 15/20

Claims (2)

(57) [Claims] 1. A fixing roller having a built-in heater for heating and fixing a toner image on a transfer sheet and transporting the toner image, a pressure roller which is pressed against and rotated by the fixing roller ,
A plate-like body having a U-shape, and the upper surface of the plate-like body is opposed to the fixing roller at a predetermined interval.
A chassis having legs at both ends fixed to a cabinet, a temperature sensor facing the fixing roller and disposed on an upper surface of the chassis , and the resin material being heated by the fixing roller.
When the chassis is deformed, the temperature sensor is pressed against the fixing roller to generate an acting force, thereby fixing the deformation.
A spring extending in the vicinity of the temperature sensor having a function of forcing the roller side, and switch means for shutting off a heating power supply of the heater when a temperature detected by the temperature sensor exceeds a predetermined temperature. Characteristic fixing device for copier. 2. The temperature sensor is a thermostat,
2. The fixing device for a copying machine according to claim 1, wherein the fixing device is disposed substantially at the center of the upper surface of the chassis .