JPS59218472A - Heat fixing device - Google Patents

Abstract

PURPOSE:To shorten the preheating time and make the fixability of a toner image uniform by setting the surface temperature of a plate-shaped heating body, which is provided in parallel with a guide member, so that the surface temperature of this heating body in both end parts in the lengthwise direction is higher than that in the center part. CONSTITUTION:A plate-shaped heating body 12 is so constituted that it faces a paper feeding guide 4 and has a length approximately equal to the length of the circumference of a heat roll 1 and the surface temperature in both end parts in the lengthwise direction is higher than that in the center part. In this constitution, when a supporting body 5 holding a toner image 6 is carried in the direction of an arrow in Fig., the toner image 6 supported on the supporting body 5 is half-fused in both end parts of the toner image 6 more than the center part. Meanwhile, since the surface temperature of the heat roll 1 has such temperature distribution that the surface temperature in both end parts is lower than that in the center part, the center part and the both end parts of the toner image 6 are half-fixed approximately uniformly and the toner image 6 is fixed to the supporting body 5 in this state when the toner image 6 is heated by the heat roll 1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides heat fixing for fixing a toner image formed on a support such as paper in an electronic copying machine, a printer, etc. between a pair of rolls, at least one of which has a heating mechanism, that rotates in pressure contact with each other. Regarding a fixing device.

As one of the fixing devices in an image forming apparatus, a heat-resistant elastic layer such as silicone rubber and/or a heat-resistant elastic material layer such as silicone rubber and/or A heat roll type heat fixing device is known which includes a heat roll coated with a heat-resistant release layer such as fluorinated ethylene and a pressure roll. (See, for example, Japanese Patent Laid-Open No. 49-81041, Japanese Patent Publication No. 53-145635, Japanese Patent Publication No. 54-19347, etc.) FIG. 1 is a schematic cross-sectional view showing an example of this type of heat constant device.

In Fig. 1, 1 is a heating roll, 2 is a pressure roll, and 3 is a heating roll.
4 indicates a paper feed guide, and 5 indicates a support member that supports a toner image 6. The heating roll 1 has a side plate supporting both ends thereof (bearings (not shown)), 4 a paper feed guide, and 5 a support body supporting a toner image 6. The outer circumferential surface of a metal hollow core 8 having a heat source 7 is coated with a heat-resistant release layer 9. On the other hand, the pressure roll 2 is formed by coating the outer circumferential surface of a metal hollow core 10 with a heat-resistant elastic layer. The heating roll 1 and the pressure roll 2 are pressed against each other by a pressure mechanism (not shown), and a predetermined contact width is formed at the pressure contact portion.

According to such a configuration, by supplying power to the heat source 7, a heating section necessary for fixing is supplied to the surface of the heating roll 1, and the heating roll 1 and the pressure roll 2 are rotated in the direction of the arrow in the figure, and the support body is heated. 5 is conveyed along the paper feed guide 4 in the direction of the arrow shown in the figure, and the toner image 6 is fixed on the support 5.

The fixed @ device has an advantage over other heat fixing devices (71-bun type, flash lamp, etc.) in that it consumes less power and can perform high-speed fixing. ,
The problem is that it takes a long time (hereinafter referred to as preheating time) of at least 1 minute for the surface of the heating roll to reach the predetermined fixing temperature of 811 degrees (approximately 150 to 200 degrees Celsius) after power is supplied to the heat source. There is.

In order to reduce the preheating time to zero, it is conceivable to reduce the heat capacity of the heating roll by, for example, making the metal hollow core smaller in diameter and thinner. However, in this case, it is necessary to increase the pressing force (0.5 to I kg/cm culm degree) in order to form a predetermined contact width to obtain the contact time necessary for fixing. Therefore, due to the small diameter and thin wall, the rigidity to withstand this pressure is insufficient, and it is not possible to obtain sufficient pressure and contact width in the longitudinal center of the hollow metal core, resulting in poor fixing. Resulting in. Furthermore, if the input power to the heat source is increased, the overshoot of the temperature with respect to the set temperature will be large, and the time required for the temperature to stabilize at the set temperature will be longer, so that the preheating time will not be shortened as a result.

Therefore, in order to shorten the preheating time, for example,
-27550, 50-93658, 50-16
No. 1244, h] No. 51-9547, No. 54-834
Although it is possible to use an auxiliary heat source as described in various publications such as No. 40, there are problems such as a fire occurring if the back side of the paper comes into contact with the preheater and poor thermal efficiency, so it is difficult to put it into practical use. There is no -C.

Further, at both ends of the heating roll 1, there are bearings (not shown) for rotationally supporting the heating roll 1, and chain wheels or gears for rotating the heating roll 1.
As shown in FIG. 2, the surface temperature of both ends of the heating roll 1 is lower than that of the medium-heated part due to the heat damage ω caused by the heating roll.
The fixing performance of the toner image also deteriorates, resulting in non-uniformity in the fixing performance of the I to I images.

SUMMARY OF THE INVENTION An object of the present invention is to provide a thermal fixing device which eliminates the above-mentioned drawbacks of the prior art, makes it possible to shorten the preheating time, and makes it possible to uniformly fix toner images.

The heat fixing device of the present invention has a pair of rotatable fixing rolls, at least one of which has a heat generating function on its surface, and the other of which is elastically deformable and covered with a heat-resistant layer. The pairs are pressed against each other to form a pressure contact portion having a predetermined contact width, and a support supporting a 1-ner image is passed through the pressure contact portion, and the pressure contact fj5 is made when viewed from the W1 feeding direction of the support. In the heat fixing device, a support guide member is installed in front of the fixing roll, and a plate-shaped heating element having a length corresponding to the axial length of the fixing roll is installed substantially parallel to the guide member. In addition, the temporary bulb is characterized in that the surface temperature of the heating body at both ends in the length lJ direction is set to be higher than the medium heating part.

The details of the present invention will be explained below with reference to the drawings.

FIG. 3 is a schematic sectional view of a heat fixing device according to an embodiment of the present invention, and FIG. 4 is a diagram J showing the temperature distribution in the length direction of a plate-shaped heating element. Indicated by the same reference numerals.

At d3 in Fig. 3, the heating roll 1 and the pressure roll 2 have the same configuration and arrangement as in Fig. 1, but in order to reduce heat capacity, the heating roll 1 and pressure roll 2 are shown in Fig. 1 with a smaller diameter and thinner wall than the one we received. As shown in Fig. 1, a metal hollow core is used.
It is different from b. Further, in FIG. 2, a plate-shaped heating element 12 having a length substantially equal to the length of the U7111 heat roll is installed opposite the paper feed guide 4.

According to such a configuration, when the support body 5 holding the toner image 6 is conveyed in the direction of the arrow shown in the figure, the support body moves toward the paper feed guide 4.
It then moves to the pressure contact area between the heating roll 1 and the pressure roll 2. At this time, electric power is supplied to the plate-shaped heating element 12 to generate heat, and the toner image 6 on the support 5 is heated to a temperature higher than the softening point of the toner (generally 100 to 130 DEG C.). Therefore, since the toner image 6 is already in a semi-molten state due to the radiant heat of the plate-shaped heating element 12 before fixing, it is possible to perform good fixing without increasing the fixing pressure or the contact width of both rolls. .

In this case, since the plate-shaped heating element 12 is close to the heating roll 1, the surface temperature of the plate-shaped heating element 12 is equal to or lower than the heat-resistant temperature of the heat-resistant release layer 8 formed on the surface of the heating roll 1.
For example, in the case of tetrafluoroethylene resin, it is necessary to set the temperature to 250° C. or lower, and from the viewpoint of maximum consumption of Mino J, it is necessary to set the surface temperature so that it is not too high. In addition, it is advantageous in terms of thermal efficiency to install the plate-shaped heating element 12 as close as possible to the paper feed guide 5 (preferably 20 m +++ or less), but it is advantageous in terms of thermal efficiency, since the surface temperature can be set low, which can save power. If the distance between the plate-shaped heating element 12 and the paper feed guide 5 is too narrow, jam troubles are likely to occur, so the distance should be determined with this in mind.

Then, the temperature distribution is such that the surface temperature of both ends of the plate-shaped heating element 12 in the direction of the long δ force is higher than that of the center (as shown in FIG. 4). In this configuration, when the support 5 holding the toner image 6 is conveyed in the direction of the arrow shown in the figure, the toner image 6 supported by the support 5 reaches a temperature d as shown in FIG. The inverse portion 4i is heated by the 4'iii sword heat from the plate-shaped heating element 12 on the right, and d is applied from the center of the toner image 6 to both ends.
3-C1 is kept in a semi-molten state. The support 6 holding the toner image 6 in this curved state further moves toward the pressure contact portion between the heating roll 1 and the pressure roll 2. heating U
- The surface temperature of the roll 1 reached 11n because it has bearings at both ends for rotationally supporting the heating roll 1, J5, and a chain wheel or gear for holding the heating roll 1 in rotation.
As shown in the figure, the temperature at both ends J5 in the length direction is lower than that at the center. As described above, the heating roll 1 having such a surface temperature distribution heats the toner image 6, which has been brought into a molten state by the plate-shaped heating element 12, from the medium heat portion of the toner image 6 to both ends thereof in advance. When the mixture is cooled, the medium-heated portions and both ends of the images 1 to 6 are transferred to the support 5 in an almost uniform semi-molten state.

The present invention will be described in detail below.

In Fig. 3, the J5 C1 heating roll 1 has an outer diameter of 27 m.
+nφ, the outside of a stainless steel vibrator (with shafts at both ends) with a wall thickness of I III Ill /i! ;j
Denolon (trade name) is coated uniformly on the surface to a thickness of 20 to 35 μl, and a length of 2 is coated inside the hollow hole.
A halogen lamp capable of generating heat uniformly over an area of 80 mm was installed facing the surface (fixing part length 280+nm).
. Further, the pressurizing member 2 was formed by uniformly applying a silicone rubber layer to the outer peripheral surface of an aluminum alloy vibrator. The plate-shaped heating elements 12 were installed using a plate heater capable of heating uniformly over the entire length of B4 size with a width of 50 mu+, so that the interval a was 7 Ill III.

Then, the pressure roll 2 is pressed against the heating roll 1 with a linear pressure of 0.5K (1/Cm), and the pressure roll 1 is rotated by a drive mechanism (not shown) (the pressure roll 2 is in contact with the outer peripheral surface of the heating roll 1). (rotates due to friction force), the thickness of the support 5 is approximately 1
Using 00 μIll plain paper (134 size) and setting the paper feeding speed to 150 mm/sec, fusing was carried out under the conditions shown in Table 1. As a result, no jam trouble occurred, and both off-setting and fusing were completed. A high quality fixed image with no defects was obtained. Moreover, it was confirmed that fixing started 25 seconds after starting power supply to the halogen lamp 7 and the freight heater. The pressure roll 2 has an outer diameter of 20 to 30 Ill Il+≠ and a pressure length of 2
Changed in the range of 60 to 280 m... and the contact width is 3.0 to 280 m...
Good results were obtained in all cases with a range of 3.5 mm. The toner used was the (NO2) magnetic toner described in Example 1 of Japanese Patent Application No. 57-13033.

As described in Table 1 and above, according to the present invention, it is possible to significantly shorten the preheating time required for hot roll type heat fixing, and moreover, it has the effect of obtaining a good standard image. .

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of a conventional heat fixing device, FIG. 2 is a temperature distribution diagram of J>I=j in the longitudinal direction of the heating roll surface, and FIG. 3 is a diagram of the temperature distribution according to an embodiment of the present invention. A schematic sectional view of the fixing device, FIG. 4 shows a temperature distribution diagram in the longitudinal direction of the plate-shaped heating element.
5: Support, 6: 1~ner image, 12: Plate heating element

Claims (1)

[Claims] 1. A pair of rotatable fixing rolls, at least one of which has a heat-generating function on its surface and is covered with a heat-resistant layer that can be elastically deformed by force; A pressure contact portion having a contact width of In the heat fixing device, a plate-shaped heating element having a length corresponding to the axial length of the fixing roll is installed substantially parallel to the guide part, and the surface temperature of the plate-shaped heating element is adjusted in the longitudinal direction. A heat fixing device characterized in that both ends are set higher than the center.