JPH0675491A - Image fixing device - Google Patents

Abstract

PURPOSE:To shorten time until attaining fixing feasible temperature and to miniaturize a device. CONSTITUTION:A columnar heat roller 18 is supported in a device frame 1 so as to positively rotate. A heat insulating layer 20 made of silicon rubber and having elasticity is formed on the outer periphery of the core bar 19 of the roller 18, and a heat transmitting layer 21 made of metallic material and having 5-100mu thickness is formed on the outer periphery of the layer 20. By applying 'Teflon(R)' on the outer periphery of the layer 21, a surface layer 22 having 5-30mu thickness is formed. A ceramic heater 23 is arranged to be opposed to the outer peripheral surface of the roller 18 so as to extend along the axial direction of the roller 18. A heat insulating material 27 made of felt, etc., is arranged so that the almost half of the outer peripheral surface of the roller 18 may be covered with the material 27, thereby preventing the heat transmitted to the roller 18 by the heater 23 from dissipating to the outside.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image fixing device for fixing a toner image on a sheet by a heating device.

[0002]

2. Description of the Related Art In a conventional image fixing device of this type, as a heating device, a structure is known in which a halogen lamp is inserted and arranged on a central axis of a cylindrical heat roller made of an aluminum material or the like. .

[0003]

However, it takes time for the halogen lamp to reach a high temperature.
Moreover, since the halogen lamp is arranged on the central axis of the roller, a non-short distance is formed between the halogen lamp and the peripheral wall of the roller. Further, a pressure roller is pressed against the heat roller in order to press the paper from the front and back during heat fixing. Therefore, the heat roller needs to have sufficient strength to withstand pressure contact with the pressure roller, and the wall thickness cannot be made so thin.

Therefore, in this conventional structure, it takes a considerable amount of time for the outer peripheral surface of the roller to reach the fixable temperature. For this reason, the fixing device having the above-described configuration is unsuitable for a facsimile device that needs to output an image immediately after reception. Further, as described above, since it is necessary to arrange a halogen lamp inside the heat roller,
It was difficult to miniaturize the heating device.

The present invention has been made to solve the above problems, and an object thereof is to reduce the time required to reach the fixing temperature and to downsize the image. To provide a device.

[0006]

In order to achieve the above object, according to the present invention, a sheet on which a toner image before fixing is attached is heated by a heat roller to fix the toner image. In the fixing device, the heat roller is formed by providing a heat conductive layer on the outer periphery of the heat insulating layer, and a heater for applying heat to the heat roller is arranged opposite to the outer peripheral surface of the heat roller.

[0007]

Therefore, according to the present invention, since the heat roller is heated by the heater arranged to face the outer peripheral surface of the heat roller,
The heat of the heater is directly transferred to the outer peripheral surface of the heat roller. Moreover, since the heat roller is formed by providing the heat conducting layer on the outer circumference of the heat insulating layer, the heat of the heater is immediately transferred only to the heat conducting layer on the outer circumference side of the heat roller, and the heat conducting layer is short-lived. Reaches the fixing temperature. Further, since the heater is provided not on the inside of the heat roller but on the outer peripheral side, the diameter of the heat roller can be reduced. Therefore, the heat from the heater can be efficiently transmitted to the heat roller, and the size of the entire apparatus can be reduced.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is embodied in an image forming apparatus will be described below with reference to the drawings.

As shown in FIG. 1, a photosensitive drum 2 is rotatably supported in the apparatus frame 1. The charger 3 uniformly charges the outer peripheral surface of the photosensitive drum 2 to a predetermined potential. The exposure device 4 forms an electrostatic latent image of a predetermined potential on the photosensitive drum 2 by irradiating light. The developing device 5 has a toner case 6 for containing the toner T and a developing roller 7. A predetermined potential is applied to the toner T by the developing roller 7, and the toner T is attached to the electrostatic latent image based on the difference between the potential and the potential of the electrostatic latent image, and the electrostatic latent image is attached. Is visualized.

The transfer unit 8 and the guide roller 9 are arranged so as to face the photosensitive drum 2 with a sheet transfer path interposed therebetween. Then, the paper P transported through the pair of feed rollers 10 and the pair of paper guides 11 is brought into close contact with the photosensitive drum 2 by the guide rollers 9, and
A predetermined electric potential is applied to the contact portion by the transfer device 8, and the toner image is transferred onto the paper P based on the difference between the electric potential and the electric potential of the toner image. The charge eliminating lamp 12 irradiates the outer peripheral surface of the photosensitive drum 2 after the transfer with light to eliminate the charge on the outer peripheral surface. The cleaner 13 cleans the residual toner on the photosensitive drum 2.

The heat fixing device 14 as an image fixing device is
The heating device 15 is arranged on the downstream side of the photosensitive drum 2.
And a pressure roller 16 made of silicon rubber or the like, which is in contact with the heating device 15 with the sheet transfer path interposed therebetween. Then, the paper P is fed between the heating device 15 and the pressure roller 16 via the paper guide 17, and the paper P is conveyed.
The toner image above is heat-fixed.

Here, the heating device 15 will be described in detail. A cylindrical heat roller 18 extending in the width direction of the paper P is supported in the device frame 1 so as to be positively rotatable. In this heat roller 18, an elastic heat insulating layer 20 made of silicon rubber is formed on the outer periphery of a core metal 19, and a heat conductive layer made of a metal material and having a thickness of 5 to 100 μ is formed on the outer periphery of the heat insulating layer 20. 21 is formed. The heat conductive layer 21 is formed by plating or sputtering. Moreover, since the outer circumference of the heat conductive layer 21 is coated with Teflon,
A surface layer 22 having a thickness of 30 μm is formed. This surface layer 2
2 prevents the toner T from adhering to the heat roller 18. The outer diameter of the entire heat roller 18 is about 1
The pressure roller 16 is in contact with the heat roller 18 at a required pressure. The pressure roller 16 is rotated as the heat roller 18 rotates.

The ceramic heater 23 is arranged opposite to the outer peripheral surface of the heat roller 18 so as to extend along the axial direction thereof. On the long plate-shaped ceramic substrate 24, the heating resistor 25 is arranged along the length direction,
The heating resistor 25 is covered with a high hardness glass coat layer 26. The glass coat layer 26 is in sliding contact with part of the surface layer 22 provided on the outermost periphery of the heat roller 18. Therefore, even if friction occurs between the surface layer 22 and the glass coat layer 26 as the heat roller 18 rotates, both of them have a small coefficient of friction and high hardness. There is no risk of wear.

When the heating resistor 25 is energized, it generates heat over its entire length. Since the heating resistor 25 is in direct contact with the outer peripheral surface of the heat roller 18 via the very thin glass coat layer 26, the heating resistor 2
The heat from the heat conduction layer 21 on the outer peripheral side of the heat roller 18
Will be immediately transmitted to. Further, since the heat insulating layer 20 is provided on the inner peripheral side of the heat conducting layer 21, the heat from the heating resistor 25 is efficiently transferred only to the heat conducting layer 21 and does not escape to other portions.

A heat insulating material 27 made of felt or the like is arranged so as to cover almost half of the outer peripheral surface of the heat roller 18,
It is in sliding contact with the outer peripheral surface of the heat roller 18. And
The heat insulating material 27 prevents the heat transferred to the heat roller 18 by the ceramic heater 23 from escaping to the outside. Further, the heat insulating material 27 is impregnated with silicon oil, so that the friction between the heat roller 18 and the heat insulating material 27 due to the rotation of the heat roller 18 is minimized. Further, by coating the heat roller 18 with silicone oil, the toner T is prevented from being fused to the outer peripheral surface of the heat roller 18.

In the image forming apparatus of this embodiment, the paper P on which the toner image is transferred by the transfer device 8 is
It is sent between the heat roller 18 and the pressure roller 16 of the heating device 15 through the transfer path. The heat roller 18 is heated by the ceramic heater 23, and the heat from the heat roller 18 melts the unfixed toner image on the paper P. The paper P is the heat roller 1
While being transported by rotation of 8, the toner image on the paper P is fixed by being pressed between the roller 18 and the pressure roller 16.

As described above, in the image forming apparatus of this embodiment, the ceramic heater 23 for heating the heat roller 18 is in sliding contact with the outer peripheral surface of the heat roller 18. Moreover, the heat roller 18 is configured by providing a very thin heat conducting layer 21 having a thickness of 5 to 100 μ on the outer periphery of the heat insulating layer 20 made of silicon rubber. Therefore, the heat from the ceramic heater 23 is efficiently transferred to the heat conductive layer 21 on the outer peripheral side of the heat roller 18 in a short time and does not escape to other portions. Moreover, since the heat conductive layer 21 is thin, the temperature is quickly raised to reach the fixing possible temperature immediately.

Therefore, for example, when the image forming apparatus is embodied as a facsimile apparatus, even if the heating device 15 is energized at the same time when a reception signal is input,
The heating device 15 can reach the fixing temperature immediately. Therefore, unlike the conventional halogen lamp, it does not take time to reach the fixable temperature, and image output can be performed immediately after reception.

Further, in this embodiment, the ceramic heater 2
3 is used, the ceramic heater 23 reaches a high temperature in a very short time as compared with the conventional halogen lamp. Therefore, the heat roller 18 can be heated to the fixing temperature in a shorter time.

Further, in this embodiment, the heat roller 18
Since approximately half of the outer peripheral surface of the heat insulating material 27 is covered with the heat insulating material 27, the heat transferred to the heat roller 18 by the ceramic heater 23 can be prevented from escaping to the outside. Therefore, the heat roller 18 can be heated more efficiently.

Further, since the ceramic heater 23 is arranged so as to face the outer peripheral surface of the heat roller 18, it is not necessary to incorporate the heater into the heat roller, unlike the conventional case. Therefore, the structure can be simplified and the diameter of the heat roller 18 can be reduced.
Then, by reducing the diameter of the heat roller 18, heat from the ceramic heater 23 is transferred to the heat roller 18.
In addition, the transmission can be performed more efficiently, and the size of the entire device can be reduced.

The present invention is not limited to the above embodiment, but can be embodied in the following modes, for example. (1) As a heater for heating the heat roller 18, a heater other than a ceramic heater, for example, configured to heat the heat roller 18 by irradiating infrared rays. (2) The heater is provided in a non-contact state with the heat roller 18. (3) A heater is provided along the outer peripheral surface of the heat roller 18.

[0023]

As described above in detail, according to the present invention, it is possible to shorten the time required to reach the fixable temperature and to achieve the miniaturization.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view showing an embodiment in which an image fixing device of the present invention is embodied in an image forming device.

[Explanation of symbols]

14 ... Heat fixing device, 15 ... Heating device, 18 ... Heat roller, 20 ... Thermal insulation layer, 21 ... Heat conduction layer, 23 ... Ceramic heater, T ... Toner, P ... Paper.

Claims (1)

[Claims] 1. An image fixing device in which a toner image before being fixed is heated by a heat roller to fix the toner image in the image fixing device, wherein the heat roller conducts heat to the outer periphery of a heat insulating layer. A heater for applying heat to the heat roller, which is formed by providing a layer,
An image fixing device that is arranged opposite to the outer peripheral surface of the heat roller.