JPH05188824A - Fixing device for image forming device - Google Patents

Abstract

PURPOSE:To provide the fixing device for the image forming device provided with a fixing temperature control means and where fixing of a good toner image can always be carried out. CONSTITUTION:The device is provided with a temperature sensor 20 which is a temperature detection means provided in contact with the device on the same circumferencial surface of a heating roll 16a and outside an image range of a fixed toner image, and a temperature fuse 21 which is an electrical current circuit breaker means breaking when the temperature of the heating roll 16a is risen exceeding a fixed set temperature range is provided in contact with the device. This fuse 21 is assembled within an electrical current circuit of a heater lamp 16c a of the heating roll 16a and a power source.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control means necessary for managing the fixing temperature of a fixing device mounted on an image forming apparatus such as a copying machine or an image scanner.

[0002]

2. Description of the Related Art Generally, in an electrophotographic image forming apparatus such as a copying machine or an image scanner, a platen on which a document is placed, a document irradiation lamp reciprocating below the platen, a reflection mirror and a fixed projection lens. And a reflection mirror, a photoconductor drum that is endlessly rotated by a predetermined potential charged by a band electrode, and an electrostatic latent image formed on the photoconductor drum surface by the scan optical system. A developing device that applies toner to the image to develop it, a transfer pole that transfers the toner image onto the surface of the recording paper, which is a transfer device that is conveyed below the surface of the photosensitive drum, and a separation electrode and a removal electrode. A fixing device for fixing the toner image transferred onto the surface of the recording paper, and a cleaning device for removing toner, paper dust, etc. remaining on the surface of the photoconductor after the transfer. .

Then, desired toner images are successively recorded on the surface of the recording paper which is intermittently conveyed along a predetermined conveying path.

To fix the toner image transferred on the recording paper, the toner is heated and fused and fixed on the recording paper by sandwiching and rotating a heating roller having a built-in heater and a pressure contact roller which is in pressure contact with the heating roller. I am trying to do it. Then, a temperature sensor is brought into contact with the peripheral surface of the heating roller to constantly detect the surface temperature of the heating roller, and C stored in advance is stored.
The power of the heater is turned on and off by the control of pu to maintain the set temperature range. If, for example, a temperature fuse is provided in the circuit of the heater and a power source for heating the heater and the temperature fuse is brought into contact with the peripheral surface of the heating roller and the surface temperature rises above the set value, the temperature fuse is By melting and cutting off the circuit between the heater and the power supply, the heating of the heater is stopped to prevent accidents such as burning of the recording paper and ignition.

[0005]

The conventional temperature sensor and temperature fuse which come into contact with the above-mentioned heating roller are, for example, provided on the peripheral surface of the heating roller within the image area of the recording paper to be fixed and at intervals in the width direction. It was arranged.

Therefore, as the number of fixing times increases, the peripheral surface of the heating roller is scratched by the respective contact pressures, which adversely affects the image quality of the toner image fixed by the pressure roller and contaminates the recording paper. I have

An object of the present invention is to solve the above problems and to provide a fixing device for an image forming apparatus which does not adversely affect the toner image and recording paper to be fixed by keeping the peripheral surface of the heating roller good. To aim.

[0008]

The object of the present invention is to detect the temperature by contacting the peripheral surface of a heating roller having a heating means, and a current circuit for shutting off the current circuit between the heating means and the power source by a specific temperature. A fixing device for an image forming apparatus, comprising: a shutoff means, wherein the temperature detecting means and the current circuit interrupting means are provided on the same circumferential surface of the heating roller. To be achieved.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention is a side sectional view showing the construction of the fixing device of FIG. 1, a top view showing the arrangement of the temperature sensor and the temperature fuse of FIG. 2, and the construction of the image forming apparatus of FIG. A side sectional view will be described. However, the present invention is not limited to this embodiment.

As shown in FIG. 3, an electrophotographic image forming apparatus
Reference numeral 18 denotes a platen glass P for placing the original M on the upper surface of the main body 1.
The scanning optical system 2 is provided below the platen glass P in the main body 1. The scanning optical system 2 includes a reciprocating document irradiation lamp 2a, a first mirror 2b, second and third mirrors 2c forming a V shape, a fixed lens 2d and a fourth mirror 2e. A photoconductor drum 3 is rotatably provided in the center of the main body 1 in the direction of the arrow, and a belt electrode 4 and a toner replenishing device 5 are provided around the photoconductor drum 3 to uniformly charge the photoconductor 3a along the rotation direction. The developing device 6 in which the toner is replenished with the developing sleeve 6a, the transfer electrode 7, the separation electrode 8, the charge eliminating electrode 9, and the cleaning device 10 are sequentially arranged. Supply cassette 11, 1
Two types of recording papers having different sizes are stored in 1'and set in the main body 1. Reference numeral 12 denotes a first paper feed roller that feeds the recording paper stored in the paper feed cassette 11 to a standby position before the second supply roller 13, and rotates via a belt to prevent double feeding of the recording paper. It is composed of a roller 12a to be driven and a stop roller (also referred to as a separating roller) 12b. Reference numeral 13 is an appropriate timing so that the recording paper fed by the first paper feed roller 12 is temporarily stopped at the standby position, and then the leading edge of the visible image on the photoconductor 3a is aligned with the recording paper at the transfer position. The second to feed paper again toward the transfer position
A paper feed roller 14 is a guide plate for guiding the recording paper fed by the first paper feed roller 12 to the position of the second paper feed roller 13. Reference numeral 15 is a conveying device that conveys the recording paper after transfer to the fixing position, and the fixing device 16 is composed of a heating roller 16a and a pressure contact roller 16b. The discharging roller discharges the recording paper after fixing to the outside of the main body. It is composed of a roller 17a and a paper discharge lower roller 17b.

When the copy button is operated in the above apparatus, the original M on the platen glass P is exposed and scanned by the scanning optical system 2, and an electrostatic latent image of the original M is formed on the photoconductor 3a of the photoconductor drum 3. It This electrostatic latent image is developed by the developing device 6.
As a result, a visible image is formed, and this visible image is transferred by the transfer electrode 7 to the recording paper fed from one of the paper feed cassettes 11 and 11 'of the main body 1. After the transfer, the recording paper is separated from the photoconductor 3a by the separation electrode 8 and is fixed by the conveying device 15 to the fixing device.
It is conveyed to 16 and is fixed there.
The paper is discharged by a and 17b.

In this way, the required toner images are successively recorded on the recording paper surface.

In the present invention, the temperature detecting means (temperature sensor) and the current circuit interrupting means (temperature fuse) of the fixing device mounted on the image forming apparatus 18 are arranged as follows, eliminating the above-mentioned problems. .

As shown in FIG. 1, the fixing device 16 includes a heating roller 16a having a heater lamp 16c built in the central portion thereof, and a pressure roller 16b and a heating roller which rotate under pressure of a predetermined pressure contact force under the heating roller 16a. A cleaning roller 22 that rotates above the 16a under pressure contact with a predetermined pressing force to clean the peripheral surface of the heating roller is rotatably supported on both side surfaces of a casing 25 of the fixing device 16. The heating roller 16a connected to the drive source is a main driving roller, and the pressure roller 16b and the cleaning roller 22 are driven rollers. On the right side of the heating roller 16a and the pressure roller 16b, an upper entrance guide plate 19a and a lower entrance guide plate 19b, which serve as a conveyance guide for the recording paper indicated by the chain line conveyed in the direction of the arrow, have a predetermined interval. The recording paper guide surfaces facing each other are formed as shown in the drawing, and the left tip ends thereof are close to the peripheral surfaces of the heating roller 16a and the pressure bonding roller 16b and are integrally attached to the housing 25. Further, on the left side of the heating roller 16a and the pressure-bonding roller 16b, there are a pair of a paper discharge upper roller 17a and a paper discharge lower roller 17b, which rotate in pressure contact with each other at a predetermined interval, on both side surfaces of the housing 25. It is pivotally supported. And the bottom discharge roller
17b and the heating roller 16a to which the drive source is connected are meshed with each other by gears provided on their supporting shafts so that the rotation is transmitted from the heating roller 16a to the paper ejection lower roller 17b and the paper ejection lower roller 17b. The rotation is transmitted to the paper discharge upper roller 17a that is in pressure contact with.

The upper and lower rollers 17a and 17b for each sheet discharge are designed to rotate in the same direction as indicated by the arrows in synchronization with the heating roller 16a and the pressure roller 16b. Then, as shown in FIG. 1, a temperature sensor 20 which is a temperature detecting means for contacting the peripheral surface of the heating roller 16a to detect the surface temperature of the heating roller 16a and a current fuse 21, for example, a temperature fuse 21, are provided.

The temperature fuse 21 is incorporated in a circuit of the heater lamp 16c and a power source for heating the heater lamp 16c and melts against a specific temperature when the surface temperature of the heating roller 16a rises above the set fixing temperature. Current circuit breaking means for breaking the circuit.

The temperature sensor 20 and the temperature fuse
The position where 21 and the peripheral surface of the heating roller 16a come into contact with each other is, as shown in FIG. 2, outside the image area A of the toner image recorded in the width direction of the B4 size recording paper (or may be above) and the heating roller. They are provided in series on the same circumferential surface of 16a, pressing in the direction of the arrows. The interval between the temperature sensor 20 and the temperature fuse 21 arranged in series and the arrangement order thereof may be appropriately set at a position where they do not interfere with the recording paper to be conveyed and fixed. A temperature sensor 20 such as a thermistor detects the surface temperature of the heating roller 16a and stores a preset temperature range Cpu (not shown).
The power source for heating the heater lamp 16c as necessary is fed back to Cpu control based on this detection information.
By turning N and OFF, the surface temperature of the heating roller 16a is always kept within the set temperature range.

On the other hand, when the temperature fuse 21 exceeds the set temperature range and the surface temperature of the heating roller 16a rises as described above and reaches, for example, around 230 ° C., the temperature fuse is melted and the circuit between the heater lamp 16c and the power source is cut off. Since it is shut off, the temperature rise stops and the temperature gradually decreases, so that accidents such as charring or ignition of the recording paper are prevented.

The current circuit breaking means is a temperature fuse 21.
Not limited to the above, bimetal may be used.

In this way, the temperature sensor 20 and the temperature fuse 21 are arranged on the same circumference of the heating roller 16a and outside the image area A of the recording paper to be fixed to control the fixing temperature of the fixing device 16. As a result, even if the fixing device 16 is operated for a long period of time, a good toner image is always fixed on the peripheral surface of the heating roller 16a without causing harmful damage to the recording paper.

Further, compared with the case where the heating rollers 16a are arranged side by side in the width direction, it is naturally possible to minimize scratches on the peripheral surface of the heating roller 16a and to make the fixing device 16 compact.

The recording paper conveyed through the upper entrance guide plate 19a and the lower entrance guide plate 19a is heated by the heating roller 16.
After a predetermined fixing is performed by sandwiching and rotating a and the pressure roller 16b, the paper is discharged to the outside of the image forming apparatus 18 by the upper and lower rollers 17a and 17b.

[0023]

As described above, the temperature sensor as the temperature detecting means and the temperature fuse as the current circuit interrupting means, for example, are provided on the same circumferential surface of the heating roller according to the present invention and in the image area to be fixed or outside the fixing roller. Despite the operation of the fixing device, a good toner image is always fixed on the recording paper. It is also extremely effective in reducing the size of the fixing device.

[Brief description of drawings]

FIG. 1 is a side sectional view showing the configuration of a fixing device according to an embodiment of the present invention.

FIG. 2 is a top view showing an arrangement of a temperature sensor and a temperature fuse according to an embodiment of the present invention.

FIG. 3 is a side sectional view showing the configuration of the image forming apparatus.

[Explanation of symbols]

 1 main body 2 scanning optical system 3 photoconductor drum 4 belt electrode 6 developing device 7 transfer electrode 10 cleaning device 16 fixing device 16a heating roller 16b pressure roller 16c heater lamp 17a paper discharge upper roller 17b paper discharge lower roller 18 image forming device 20 temperature detection Means (temperature sensor) 21 Current circuit breaking means (temperature fuse)

Claims (1)

[Claims] 1. An image provided with temperature detecting means for contacting a peripheral surface of a heating roller having a heating means to detect a temperature and current circuit breaking means for breaking a current circuit between the heating means and a power source according to a specific temperature. In the fixing device of the image forming apparatus, the temperature detecting unit and the current circuit breaking unit are provided on the same circumferential surface of the heating roller.