JPH09319245A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make temperature distribution in a longitudinal direction on the surface of a heat roller nearly uniform, especially, in the case of using a thin heat roller by making length from a pair of bearings provided on both sides supporting the heat roller to the end of the heat roller nearly the same. SOLUTION: The length of the heat roller 32 in the longitudinal direction is made longer by the width G of a fixing gear 27 also on a side where the gear 27 is not attached. Namely, the length H from a heat roller bearing A25 on the gear 27 side to the end of the roller 32 is made the same as the length K from the other heat roller bearing B26 to the end of the roller 32. Since heating speed by a fixing heater 33 is slow at the end of the roller 32 because of receiving the influence of outside air, the heater 33 is set so that light quantity at the end is made larger than the light quantity at a center part and it is made symmetric right and left, whereby the difference of the heating speed by the heater 33 between the center part and the end of the roller 32 is eliminated and the temperature distribution in the longitudinal direction on the surface of the roller 32 becomes nearly uniform.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer and a facsimile, and more particularly to an image forming apparatus having a fixing device for fixing a toner image on a transfer material. .

[0002]

2. Description of the Related Art Conventionally, there has been a demand for power saving of an image forming apparatus, and in particular, a fixing device supplies power only during printing, but a warming up time for that is required, and it is an important subject to shorten the warming up time. Is.

A conventional image forming apparatus will be described below. 4 is a configuration diagram of a conventional image forming apparatus, FIG. 5 is a side view of a fixing unit of the conventional image forming apparatus, FIG. 6 is a cross-sectional view of the fixing unit of the conventional image forming apparatus as viewed from the side, and FIG.
Is a sectional view of the fixing unit of the conventional image forming apparatus as seen from the front, FIG. 8 is a light distribution distribution diagram of the fixing heater of the conventional image forming apparatus, and FIG. 9 is a temperature distribution diagram of the heat roller surface of the conventional image forming apparatus. Is.

In FIG. 4, reference numeral 1 is an image forming apparatus main body, 2
Is a paper feed cassette for accommodating the transfer material 3, 4 is a paper feed roller for feeding the transfer materials 3 in the paper feed cassette 2 one by one, and 5 is a conveying direction of the transfer material 3 fed by the paper feed roller 4. A transport roller for transporting to the downstream printing unit, 6 is a process unit that stores toner 7 and includes an image carrier 8.
Reference numeral 9 is a laser scanning unit for forming an electrostatic latent image on the image carrier 8, 10 is a transfer roller which is arranged to face the image carrier 8 and transfers the image formed by the toner 7 on the image carrier 8 to the transfer material 3, Reference numeral 11 is a fixing unit described later, 12 is a discharge roller for discharging the transfer material 3 that has passed through the fixing unit 11 to the outside of the machine, and 13 is a paper discharge tray for stacking the printed transfer material 14 on which printing is completed.

5 to 7, reference numerals 15 to 31 are members constituting the fixing unit 11. Reference numeral 15 is a heat roller having an aluminum or iron cored bar provided with a heat-resistant surface layer having high releasability, and 16 is a cored bar 17 covered with a material provided with an elastic layer made of silicon rubber or the like and facing the heat roller 15. The pressure roller arranged, 18 is a frame for supporting each member of the fixing unit 11, 19 is a fixing cover, and 20 is a fixing member.
The fixing heater that heats the heat roller 15 by the radiant heat of the halogen lamp whose light distribution is designed as shown in 21, the thermistor element 21 for controlling the temperature of the surface of the heat roller 15, and 22 the transfer material 3 from the heat roller 15 Separation peeling claws, 23 and 24 support the fixing heater 20, and a terminal A and a terminal B for supplying power, and 25 and 26 heat roller bearings A and heat roller bearings for supporting the heat roller 15 on the frame body 18. B and 27 are fixing gears for transmitting the driving force from the image forming apparatus main body 1 to the heat roller 15, and 28 and 29 are movable to the heat roller 15 side along a groove cut out in the frame body 18. The pressure roller bearing A and the pressure roller bearings B, 30 and 31 configured to support the core metal portion 17 of the pressure roller 16 are the pressure roller 1.
6 is a pressure spring A and a pressure spring B for pressing 6 to the heat roller 15.

The operation of the conventional image forming apparatus configured as described above will be described below. Paper cassette 2
One of the transfer materials 3 stored in is taken out by the rotation of the paper feed roller 4 in the direction of the arrow A, passes through the transport roller 5, and reaches the nip portion formed by the image carrier 8 and the transfer roller 10 in the process unit 6. Be transported. After the electrostatic latent image is formed on the image carrier 8 by the laser scanning unit 9, the toner 7 in the process unit 6 is transferred to the electrostatic latent image to form a visible image. The image formed by the toner 7 formed on the image carrier 8 is transferred to the transfer material 3 that has reached the nip portion formed by the image carrier 8 and the transfer roller 10, and the transfer material is rotated by the rotation of the image carrier 8 in the arrow B direction. 3 reaches a fixing unit 11, where an image formed by the toner 7 on the transfer material 3 is melted and fixed to the transfer material 3, and then discharged onto a paper discharge tray 13 by a discharge roller 12.

In the fixing unit 11, the heat roller 15
The surface temperature of is controlled by receiving a detection signal from the thermistor element 21 so as to reach a predetermined fixing temperature, causing the fixing heater 20 to emit light, and being heated by the radiant heat of the fixing heater 20. Further, the heat roller 15 includes a pressure roller 16
Are arranged in pressure contact with each other, and the heat roller 15 and the pressure roller 1
Toner 7 on the transfer material 3 guided to the nip portion formed by 6
The image formed by is fixed to the transfer material 3 by heat and pressure. Further, since the end portion of the heat roller 15 is hard to be heated due to the influence of the outside air, the temperature distribution on the surface of the heat roller 15 is kept uniform by increasing the light amount at the end portion with respect to the light amount at the central portion. ing. As shown in FIG. 8, the light distribution design of the fixing heater 15 is such that the light amount at the end portion is made higher than the light amount C at the central portion to make it symmetrical, and the temperature distribution on the surface of the heat roller 15 at that time is shown in FIG. As shown in.

[0008]

However, in the above-mentioned conventional configuration, as shown in FIG. 9, the temperature distribution on the surface of the heat roller 15 can be obtained only by increasing the light distribution at both ends of the fixing heater 20 symmetrically with respect to the central portion. The temperature is not uniform over the entire area, and the surface temperature F on the fixing gear 27 side is higher than the surface temperature E at the central portion of the heat roller 15, which causes a problem of offset. This is because the fixing heater 20 is the transfer material 3
While the heat roller 15 is designed to be even on the left and right with respect to the maximum width,
Is increased by the width G. That is, the length H from the heat roller bearing A25 on the fixing gear 27 side to the end of the heat roller 15 is different from the length I from the other heat roller bearing B26 to the end of the heat roller 15. This means
The temperature gradient at the end of the heat roller 15 is different between the left and right, and the heat capacity of the fixing gear 27 is different due to the mounting of the fixing gear 27.
The temperature at the 5th end has increased. This phenomenon occurs particularly remarkably when the thin heat roller 15 is used to shorten the warm-up time. Further, it is possible to make the temperature distribution on the surface of the heat roller 15 uniform by lowering the light distribution on the left and right of the fixing heater 20 on the side of the fixing gear 23 relative to the other. There is another problem that it is possible to mount the 20 in the wrong direction.

The present invention solves the above-mentioned conventional problems, and particularly provides a high-quality image forming apparatus that solves the problem of offset that occurs when a thin heat roller is used to shorten the warm-up time. The purpose is to

[0010]

In order to achieve the object, the image forming apparatus of the present invention has a length from each of a pair of bearings provided on both sides supporting a heat roller to the end of the heat roller. It has the same configuration.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention comprises a heat roller for fusing a toner image onto a transfer material,
In an image forming apparatus provided with a pressure roller arranged in pressure contact with a heat roller, the length from each of a pair of bearings provided on both sides supporting the heat roller to the end of the heat roller is configured to be substantially the same. The fixing heater having a symmetrical light distribution has an effect that the temperature distribution in the longitudinal direction of the heat roller surface can be made substantially uniform over the entire area.

According to a second aspect of the invention, in the first aspect of the invention, the length from the end of the heat roller to the end of the pressure roller is substantially the same on both sides. It has the effect that the uniformity of the temperature distribution in the longitudinal direction of the roller surface can be further enhanced.

According to a third aspect of the present invention, in the first aspect of the invention, a fixing gear is provided on one side of the heat roller, and the fixing gear is provided on the side opposite to the side where the fixing gear of the heat roller is grounded. Since members having the same heat capacity are provided, it has an effect that the uniformity of temperature distribution in the longitudinal direction of the heat roller surface can be further enhanced.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the heat capacity per unit length of the heat roller is 0.05 to 0.95 cal / cm · ° C. It has the effect that the effect of the invention described in 1) appears remarkably.

The embodiment of the present invention will be described below with reference to FIG.
3 is a cross-sectional view of a fixing unit of an image forming apparatus according to an embodiment of the present invention as seen from the front, FIG. 2 is a light distribution distribution diagram of a fixing heater of an image forming apparatus according to an embodiment of the present invention, and FIG.
FIG. 6 is a temperature distribution diagram of the heat roller surface of the image forming apparatus according to the embodiment of the present invention. 16 to 19 in FIG.
And 21 to 31 have the same configuration as the conventional image forming apparatus, the description thereof will be omitted. 32 is 0.3 to 0.5 mm
A heat roller having a heat-resistant surface layer with high releasability provided on an iron-based core metal having a thickness of 3 and a fixing heater 33 configured by a halogen lamp or the like for heating the heat roller 32 by radiant heat. As shown in FIG. 2, the light distribution design of the fixing heater 33 is such that the end light quantity is increased to J with respect to the light quantity C in the central part so as to be symmetrical, and the temperature distribution on the surface of the heat roller 32 at that time is shown in FIG. As shown.

The operation of the image forming apparatus according to the embodiment of the present invention configured as described above will be described.

The length of the heat roller 32 in the longitudinal direction is the width G of the fixing gear 27 even on the side where the fixing gear 27 is not mounted.
Just make it longer. That is, the length H from the heat roller bearing A25 on the fixing gear 27 side to the end of the heat roller 32 is H.
From the other heat roller bearing B26 to the heat roller 3
The length K to the end of 2 is the same. At the end of the heat roller 32, the fixing heater 33 is affected by the outside air and the like.
Since the heating speed by the fixing heater 33 is slow, the fixing heater 33 makes the light amount at the end portion higher than the light amount C at the central portion and makes it symmetrical so that the difference in the heating speed by the fixing heater 33 at the central portion and the end portion of the heat roller 32. As shown in FIG. 3, the temperature distribution in the longitudinal direction on the surface of the heat roller 32 is substantially uniform at the temperature E over the entire area.

[0018]

As described above, according to the present invention, the problem of offset that occurs when a thin heat roller is used to shorten the warming-up time can be solved, and the image quality can be improved.

[Brief description of drawings]

FIG. 1 is a sectional view of a fixing unit of an image forming apparatus according to an embodiment of the present invention as seen from the front.

FIG. 2 is a light distribution distribution diagram of a fixing heater of an image forming apparatus according to an embodiment of the present invention.

FIG. 3 is a temperature distribution diagram of a heat roller surface of the image forming apparatus according to the embodiment of the present invention.

FIG. 4 is a configuration diagram of a conventional image forming apparatus.

FIG. 5 is a side view of a fixing unit of a conventional image forming apparatus.

FIG. 6 is a sectional view of a fixing unit of a conventional image forming apparatus as seen from a side surface.

FIG. 7 is a sectional view of a fixing unit of a conventional image forming apparatus as seen from the front.

FIG. 8 is a light distribution distribution diagram of a fixing heater of a conventional image forming apparatus.

FIG. 9 is a temperature distribution diagram of a heat roller surface of a conventional image forming apparatus.

[Explanation of symbols]

 16 Pressure Roller 25 Heat Roller Bearing A 26 Heat Roller Bearing B 27 Fixing Gear 32 Heat Roller

Claims (4)

[Claims] 1. An image forming apparatus comprising a heat roller for fusing a toner image onto a transfer material, and a pressure roller arranged in pressure contact with the heat roller. A pair of rollers provided on both sides supporting the heat roller. The image forming apparatus is characterized in that the length from each of the bearings to the end of the heat roller is configured to be substantially the same. 2. The image forming apparatus according to claim 1, wherein the length from the end of the heat roller to the end of the pressure roller is substantially the same on both sides. 3. A fixing gear is provided on one side of the heat roller, and a member having substantially the same heat capacity as the fixing gear is provided on the opposite side of the heat roller from the side on which the fixing gear is mounted. The image forming apparatus according to claim 1. 4. The image forming apparatus according to claim 1, wherein the heat capacity of the heat roller per unit length is 0.05 to 0.95 cal / cm · ° C.