JPH02191978A - Non-contact heat fixing device - Google Patents

Abstract

PURPOSE:To eliminate the variance of heating and fixing by providing one or more radiant heat sources and setting the quantity of radiant heat, which these heat sources give to an image forming sheet, to the smallest value in the entrance side in the advance direction of the image forming sheet and increasing this quantity toward the exist side in the advance direction. CONSTITUTION:A plate-shaped radiant heat source 2 is provided in a tank wall 1 at an angle to a base guide 6 which is the guide for advance of the image forming sheet, and a fan 3 for agitation is provided to uniformize the air temperature distribution in the tank. When the image forming sheet is put into a device by a feed roll 4, it first comes into contact with air kept at a certain temperature by the fan 3 and has the temperature gradually raised linear-functionally by heat conduction from air. When the image forming sheet is put into the tank, it enters into the radiation range of the radiant heat source 2 and has the temperature raised furthermore by heat conduction from air and the radiant heat from the radiant heat source 2. Since the radiant heat source 2 is provided at an angle to the advance direction of the image forming sheet, the quantity of heat given to the sheet is gradually increased in accordance with advance of the sheet, and the temperature of the sheet rises exponential-functionally after the sheet enters into the radiation range of the radiant heat source 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a heat fixing device for heat fusing a toner image, etc. on an image forming sheet of a copying machine or the like. In particular, JP-A-58-88
A latent image forming sheet coated with microcapsules encapsulating a coloring agent and a sensitive substance that is sensitive to light and immobilizes the coloring agent disclosed in Publication No. 739, etc., and a latent image forming sheet coated with microcapsules that react with the coloring agent to develop color. The present invention relates to a heat fixing device suitable for a color copying machine using an image forming sheet coated with a developer.

[Summary of the Invention] The present invention uses a radiant heat source such as far infrared rays as the heat source of a heat fixing device that develops and heat-fuses the latent image transferred onto the image forming sheet, and the radiant heat source is applied to the image forming sheet. The amount of radiant heat applied is distributed such that it is least on the population side in the traveling direction of the image forming sheet and increases toward the exit side in the traveling direction, and the temperature rise of the image forming sheet traveling at a constant speed is exponential. This is a small, low-cost, non-contact heat fixing device that prevents image defects caused by rapid explosive evaporation of water contained in a formed sheet, improves heating efficiency, and eliminates uneven heat fixation.

[Prior Art] Conventionally, to thermally fuse toner images in copying machines, etc., a contact type thermal fixing device is used to heat fuse the image forming sheet by using a hollow roller whose surface is coated with silicone rubber or the like and a built-in heater such as a halogen lamp. A radiation type non-contact heat fixing device using a flash light source, a heater heat source, and the like are known.

[Problems to be Solved by the Invention] However, in the case of the above-mentioned contact type heat fixing device, the advantage is that heat fusing can be performed in a short time, but on the other hand, toner images etc. adhere to the roller during fusing, and the image forming sheet There are disadvantages such as staining the image forming sheet and wrapping the image forming sheet around the roller. Particularly, in the case of an image forming sheet such as that disclosed in Japanese Patent Application Laid-Open No. 58-88739, significant staining and curling occur.

In the case of the non-contact type heat fixing device such as the flash type or radiation type, staining of the image forming sheet is improved, but the thermal efficiency is lower than that of the contact type, so the temperature of the radiant heat source is increased. If the amount of radiant heat is not increased, it is not possible to increase the speed.
When the temperature of the radiant heat source is uniformly raised to cope with higher speeds, the temperature of the image forming sheet as disclosed in Japanese Patent Application Laid-Open No. 58-88739 etc. rises rapidly and the evaporation of moisture explodes. The image evaporates and small irregularities appear on the image. Therefore, in the case of an image forming sheet such as that disclosed in Japanese Patent Laid-Open No. 58-88739, etc., the temperature of the radiant heat source must be kept low and heated over a long distance, or separately,
It is necessary to deal with the above-mentioned image defects by heating in stages using a heater. For this reason, the fuser itself is long,
This will result in high costs.

The present invention solves these conventional drawbacks and provides a heat fixing device for copying machines that is fast, has no uneven heat fixation, has no image defects due to water evaporation in the image forming sheet, and is small and low cost. The purpose is to donate money.

[Means and operations for solving the problems] In order to solve the above problems, the present invention provides a system in which the amount of radiant heat given by the radiant heat source to the image forming sheet is minimized ( The distribution increases toward the exit side in the traveling direction, and the temperature rise rate of the image forming sheet, which advances at a constant speed, is kept low on the entrance side, and increases as the temperature rises as it progresses, reaching the maximum on the exit side. According to the heating method, the temperature of the image forming sheet increases not linearly but exponentially, and a sudden temperature increase can be prevented.

That is, in the non-contact heat fixing device of the present invention, the temperature of the image forming sheet can be gradually increased from the entrance side in the traveling direction, and the water contained in the image forming sheet can be gradually evaporated.

[Embodiments] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view of the structure of an embodiment of the present invention.

In the tank wall 1, a plate-shaped radiant heat source 2 is provided obliquely with respect to a base guide 6 that serves as a advancing guide for the image forming sheet. Further, a stirring fan 3 is provided to keep the air temperature distribution within the tank constant.

The image forming sheet is fed into the tank at a constant speed by a feed roller 4. When the image forming sheet enters the tank, the fan 3
It first comes into contact with air kept at a constant temperature, and the temperature gradually rises in a linear manner due to heat conduction from the air. When it further enters the tank, it enters the radiant range of the radiant heat source 2. When the image forming sheet enters the radiation range, the temperature of the image forming sheet increases due to heat conduction from the air and radiant heat from the radiant heat source 2.

FIG. 3 is an explanatory diagram of an example of the temperature rise rate of the image forming sheet depending on the distance of the radiant heat source. The relationship between the distance between the radiant heat source and the image forming sheet and the temperature rise of the image forming sheet will be explained with reference to this figure. Here, La, Lb, and Lc are the distances of the image forming sheet with respect to the same radiant heat source. As shown in this figure, as the distance becomes shorter, the temperature rise rate of the image forming sheet rises more rapidly and the saturation temperature also becomes higher.

Note that FIG. 3 shows the rate of temperature rise of the image forming sheet when the image forming sheet is left without being moved under a radiant heat source. Therefore, the amount of radiant heat given to the image forming sheet by the radiant heat source 2 in FIG. 1 gradually increases as the image forming sheet advances, since the radiant heat source 2 is provided obliquely to the advancing direction of the image forming sheet. , the temperature rise of the image forming sheet becomes exponential after entering the radiant range of the radiant heat source 2.

FIG. 2 is an explanatory diagram of an example of the rate of temperature rise within the non-contact heat fixing device. The state of temperature rise of the image forming sheet will be explained with reference to this figure. In the figure, A shows the temperature increase state in the case of the non-contact type heat fixing device according to the present invention, and B shows the temperature rise state in the case of the non-contact type heat fixing device according to the present invention, with only the radiant heat source 2 being placed in parallel with the image forming sheet. This figure shows the temperature rise state when the sensor is installed.

First, B will be explained. In case B, the temperature of the image forming sheet sent into the tank increases due to heat conduction by the air in the tank.
The image forming sheet, which increases linearly from rr to temperature Ta, is further fed into the radiant range of the radiant heat source 2. Here, the radiant heat source 2 is provided parallel to the image forming sheet, and the amount of radiant heat is constant everywhere in the traveling direction of the image forming sheet. Therefore, the temperature of the image forming sheet increases rapidly after reaching the temperature Ta. Then, the image is thermally fixed exceeding the water evaporation temperature Tb contained in the image forming sheet and further exceeding the complete thermal fusing temperature Tc.

On the other hand, in the case of A, the temperature rises up to Ta in the same way as in B. However, once the image forming sheet enters the radiation range of the radiant heat source 2, the temperature increases gradually and increases exponentially due to the radiant heat that increases with the advancing direction of the image forming sheet. Then, the image is thermally fixed exceeding the water evaporation temperature Tb contained in the image forming sheet and further exceeding the complete thermal fusing temperature Tc.

Now, the difference between the two lies in how the water evaporation temperature Tb contained in the image forming sheet is exceeded. In the case of B, the temperature rises rapidly from the temperature Ta and exceeds the temperature Tb. At this time, the water contained in the image forming sheet starts to evaporate from the temperature Tb, but before all of it evaporates, the temperature of the image forming sheet increases and evaporates rapidly and explosively. At this time, uneven image defects occur on the image forming sheet.

On the other hand, in the case of A, the temperature is gradually raised from the temperature Ta, and the temperature near the evaporation temperature Tb of the water contained in the image forming sheet is maintained for a longer period of time than in the past, and the water is gradually evaporated. Then, the image is thermally fixed by a rapid temperature rise.

Here, in order to prevent uneven image defects from occurring on the image forming sheet with the same configuration as in case B, it is necessary to set the temperature rise rate after temperature Ta to a temperature rise rate close to exceeding temperature Tb in case A. There is. This is the case of C in FIG. However, in the case of C, image defects do not occur, but the temperature exceeds the complete thermal fusion temperature Tc more slowly than in the case of A.

Therefore, the temperature increase state in which the image is heated and fixed quickly without causing image defects is the case A in which the temperature rises exponentially, and according to the configuration of the present invention, the temperature rise is in the A state.

FIGS. 4 and 6 show other preferred embodiments of the present invention.

Description will be given below with reference to the drawings.

In FIG. 4, the configurations of the tank wall 1, fan 3, feed roller 4, discharge roller 5, and base guide 6 are the same as in FIG.

However, the plate-shaped radiant heat source 2 is provided parallel to the base guide 6.

Furthermore, a heat shield plate 7 is provided below the radiant heat source 2 to control the amount of radiation.

As shown in FIG. 5, the heat shield plate 7 has openings 7a having different opening areas with respect to the traveling direction of the image forming sheet.

This opening 7a is small on the entrance side in the direction of movement of the image forming sheet and becomes larger toward the exit side. That is,
The aperture ratio is smallest on the inlet side, increases toward the outlet side, and becomes largest on the outlet side.

Therefore, in this configuration, the amount of radiant heat received by the image forming sheet from the radiant heat source 2 is distributed by the heat shield plate 7 such that the amount of radiant heat received by the image forming sheet is minimized on the entrance side in the advancing direction of the image forming sheet and increases toward the opening side in the advancing direction. The same effect as in Figure 1 is obtained.

Next, in FIG. 6, the configurations of the tank wall l, fan 3, feed roller 4, discharge roller 5, and base guide 6 are the same as in FIG. It is a rod-shaped heat source.

The arranged radiant heat sources are arranged at wide intervals on the entrance side and arranged at narrow intervals towards the exit side with respect to the advancing direction of the image forming sheet. Each reflection jii 12a distributes the radiant heat equally within the receiving range of each radiant heat source 2.

Therefore, the amount of radiant heat received by the image-forming sheet is the smallest on the entrance side in the direction of travel of the image-forming sheet, and increases toward the exit side in the direction of travel, resulting in the same effect as shown in FIG. 1.

Furthermore, instead of changing the interval between the radiant heat rA2, the same effect can be obtained by setting the temperature of each radiant heat source 2 to be lowest on the entrance side in the image forming sheet traveling direction and increasing toward the exit side in the traveling direction. .

[Effects of the Invention] As explained above, according to the present invention, it is possible to achieve high speed fixing, uneven heat fixing, no image defects due to evaporation of water contained in the image forming sheet, and furthermore, a compact and low-cost non-woven fabric for copying machines. A contact type heat fixing device can be realized.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the configuration of an embodiment of a non-contact heat fixing device according to the present invention, FIG. 2 is an explanatory diagram of an example of the temperature rise rate of an image forming sheet, and FIG. 3 is an image of the radiant heat source at different distances. An explanatory diagram of an example of the temperature rise rate of the formed sheet, FIGS. 4 and 6 are sectional views of the structure of other embodiments of the non-contact fixing device according to the present invention, and FIG. 5 is a schematic diagram of a heat shield plate. .・Tank wall ・Radiant heat source ・Reflector ・Fan ・Feed roller ・Discharge roller 6 ・Base guide 7 ・Heat shield plate 7a ・・Opening part and above Applicant Seiko Electronic Industries Co., Ltd. Agent Patent attorney Takayuki Hayashi Help No. 1 Explanation of Figure 1 of the Climbing Cliff 2 No. 2
Figure 3 Leap

Claims (2)

[Claims] (1) In a non-contact heat fixing device that heats and thermally fuses a toner image formed on an image forming sheet of a copying machine or the like using radiant heat such as far infrared rays, one or more radiant heat sources are provided,
A non-contact type heat fixing device characterized in that the amount of radiant heat given to the image forming sheet by the radiant heat source is distributed such that the amount of radiant heat given to the image forming sheet is smallest on the inlet side in the direction of travel of the image forming sheet and increases toward the outlet side in the direction of travel of the image forming sheet. (2) The radiant heat source is a plate-shaped radiant heat source, and the radiant heat source is arranged such that the distance between the image forming sheet and the radiant heat source is longest on the entrance side in the direction of movement of the image forming sheet and becomes shorter toward the exit side. is provided obliquely to the traveling direction of the image forming sheet, and the amount of radiant heat given to the image forming sheet by the radiant heat source is distributed such that it is least on the entrance side in the traveling direction of the image forming sheet and increases toward the exit side in the traveling direction. The non-contact type heat fixing device according to claim 1, characterized in that: