JPH1124466A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the load of a heating roller, to prolong the service life thereof and to realize excellent high-speed both-side fixing by providing a device with two pairs of the heating rollers and arranging at least the first heating roller pair executing the fixing first as the heating roller pair constituted by forming a rubber layer on a core bar. SOLUTION: Heating rollers 3 and 4 are arranged so that they can be into press-contact with each other to constitute a first heating roller pair. Further to the first pair, a second heating roller pair constituted of heating rollers 6 and 7 so that they can be in press-contact with each other is arranged on the downstream side in the carrying direction of paper. The first pair of rollers 3 and 4 and the second pair of rollers 6 and 7 (at least the first pair of rollers 3 and 4) are constituted by forming rubber layers 3b, 4b, 6b and 7b made of a material such as silicone rubber on the core bars 3a, 4a, 6a and 7a. Here, it is preferable that a fixing temperature at the first pair of rollers 3 and 4 is set to be lower than that at the second pair of rollers 6 and 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fixing device for forming a fixed toner image on both sides of a recording material.

[0002]

2. Description of the Related Art As a configuration for fixing a toner image on both sides of a recording material such as paper, a first configuration is as follows.
After transferring the toner image to the (front surface), the recording material holding the unfixed toner image is passed through a fixing device to first fix the toner image on one side of the recording material, and then the recording material is removed. After reversing, the toner image is transferred to the other surface (back surface) of the recording material, the recording material holding the unfixed toner image is passed through a fixing device, and the toner image is transferred to the other surface of the recording material. The second configuration is to transfer the toner image to one side (front surface) of the recording material and then fix the toner image in the unfixed state. The toner image is also transferred to the other surface (back surface) of the recording material while holding the recording material, and the recording material holding the unfixed toner image on both surfaces is passed through a fixing device to perform one fixing step. There is known an image forming apparatus capable of fixing a toner image on both sides simultaneously.

[0003] In the case of the first configuration, if the recording material is an individual sheet one by one, the surface-fixed sheet is turned upside down by a reversing device such as a switchback mechanism, and then the front surface is turned over. It is possible to re-feed the paper to the printing and fixing sections used for printing, but if the recording material is long and continuous, so-called continuous paper, use it for front-side printing. Since the sheet cannot be fed again to the imprinting section and the fixing section, the fixing device for the front side fixing and the fixing device for the back side fixing are required as a result, and the apparatus cost is increased. Problem. On the other hand, in the case of the second configuration, one fixing device is sufficient, and the cost of the device can be reduced.

As a second configuration, for example, a configuration as shown in FIG. 4 is adopted. In the figure, a sheet 2 holding an unfixed toner image 1 on both sides is heated by a preheating plate (preheater) 12 provided in non-contact with the sheet surface, and then a pair of heating Roller 1
The toner image 1 is fixed on each side of the sheet 2 by being nipped and conveyed by 3 and 14.

[0005]

In the configuration of the fixing device shown in FIG. 4, the amount of heat supplied to the sheet can be secured by using a large pre-heater or reducing the distance between the pre-heater and the sheet. It is conceivable to improve the configuration of the pre-heater by using the pre-heater. In addition, when the distance between the preheater and the sheet is reduced, it is difficult to approach the sheet in consideration of fluttering caused by the slack of the sheet being conveyed, which is technically difficult. Therefore, in the configuration of this type of fixing device, it has been general to secure a heat supply amount to a target sheet by increasing the temperature and pressure of the heating roller.

However, in recent years, as the printing speed of the printing apparatus has been increased, the supply of heat to the paper cannot be caught by simply increasing the temperature and pressure of the heating roller. When the pressure is increased, there is a problem that the speed of wear and deterioration of the surface of the heating roller increases, and the life of the heating roller is significantly reduced.

Accordingly, an object of the present invention is to provide a fixing device capable of reducing the load on the heating roller, extending the life of the heating roller, and realizing excellent high-speed double-side fixing. It is in.

[0008]

SUMMARY OF THE INVENTION The object of the present invention is to provide a heating roller pair supported so as to be able to press against each other, and a long recording material holding an unfixed toner image on both sides of the heating roller pair. In a fixing device for fixing the toner image to a recording material while nipping and conveying the pressing member, a pair of heating rollers arranged in a front-back relationship along a recording material conveying direction is provided, and at least the recording material conveyed is provided. On the other hand, this is achieved by providing a first heating roller pair for performing fixing first as a heating roller pair having a rubber layer provided on a cored bar.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) As shown in FIG. 1, a heating roller 3 and a heating roller 4 are provided so as to be in pressure contact with each other to form a first heating roller pair. Also, the first heating roller pair 3, 4
On the other hand, on the downstream side in the sheet transport direction, a second heating roller pair constituted by a heating roller 6 and a heating roller 7 which are provided so as to be able to press against each other is provided.

The first pair of heating rollers 3, 4 and the second pair of heating rollers 6, 7 are provided on cores 3a, 4a, 6a, 7a with rubber layers 3b, 4b, 6b, made of a material such as silicon rubber. 7
It is configured as a so-called soft roller provided with b.

The fixing temperature of the first pair of heating rollers 3, 4 is set lower than the fixing temperature of the second pair of heating rollers 6, 7.

Further, the first heating roller pair 3, 4 and the second
Between the pair of heating rollers 6 and 7, there is provided a buffer plate 5 which is swingably supported on the recording material 2 and absorbs the slack of the recording material 2. Here, the slack of the recording material 2 also has a function of absorbing a difference in the sheet conveyance speed caused by thermal expansion of the soft rollers 3 and 4 and the soft rollers 6 and 7.

In the above configuration, the continuous paper 2 holding the unfixed toner image 1 on both sides is first fixed by the soft rollers 3 and 4 and then fixed by the soft rollers 6 and 7 to form the toner image 1. The image is fixed on each side of the sheet 2.

(Embodiment 2) FIG. 2 shows a second embodiment of the present invention. The configuration of FIG. 2 differs from the configuration of FIG. 1 in that a hard roller configuration is employed as the second heating roller pair.

The heating roller 8 and the heating roller 9 are made of a metal core 8a,
Rubber layers 8b, 9 made of a material such as silicon rubber on 9a
b is provided as a soft roller. On the other hand, the heating roller 10 constituting the second heating roller pair
The heating roller 11 is configured as a hard roller in which resin layers 10b and 11b made of Teflon-based material are provided on cores 10a and 11a.

The other structure is the same as that of the structure shown in FIG. In the above configuration, the continuous paper 2 holding the unfixed toner image 1 on both sides is first fixed by the soft rollers 8 and 9 and then fixed by the hard rollers 10 and 11 so that the toner image 1 is It is fixed on each side.

FIG. 3 shows the relationship between the type of the heating roller and the glossiness of the toner image after the heat and pressure fixing. Here, depending on the purpose and the target printed matter, there may be a case where the higher the gloss is, the better the print quality is. In the present invention, the lower the gloss is, the better the print quality is. In FIG. 3, Comparative Examples 1 and 2 are added in addition to the configurations of the above-described Examples 1 and 2. Here, in Comparative Example 1, the first heating roller pair is configured as a hard roller, and the second heating roller pair is configured as a soft roller. In Comparative Example 2, both the first heating roller pair and the second heating roller pair are configured as hard rollers.

FIG. 3 shows a first embodiment of the present invention.
The glossiness of the toner image fixed by heating and pressurizing with the fixing device was very small, and good print quality could be secured. The glossiness of the toner image fixed by heating and pressing by the fixing device of Example 2 also showed a tendency to be higher than that of Example 1, but showed a very small value as compared with Comparative Examples 1 and 2. In addition, print quality equivalent to that of the first embodiment could be secured.

Further, in the conventional fixing device, since the preheater is not in contact, it is necessary to increase the temperature and pressure of the soft roller in order to increase the amount of heat supplied from the preheater to the paper. According to the fixing device of the present invention, the sheet is nipped and conveyed while applying a heating and pressurizing action to the sheet by two pairs of heating rollers arranged in a front-back relationship along the recording material conveying direction. Can be supplied to the sheet at a temperature equal to or higher than that of the conventional configuration at a lower temperature, and the speed of double-sided fixing can be increased.

In the case of the configuration of the second embodiment, the number of replacements of the soft roller, which is considered to be shorter than that of the hard roller, by combining the soft roller and the hard roller is smaller than that of the configuration of the first embodiment. Since this can be reduced, there is a practical effect that the cost spent on the soft roller can be reduced.

[0022]

As described above, according to the present invention, the load on the heating roller can be reduced, the life of the heating roller can be prolonged, and good high-speed double-side fixing can be realized. An apparatus can be provided.

[Brief description of the drawings]

FIG. 1 is a side view showing a first embodiment of a fixing device of the present invention.

FIG. 2 is a side view showing a second embodiment of the fixing device of the present invention.

FIG. 3 is an explanatory diagram illustrating a relationship between a fixing device configuration and a glossiness of a fixed toner image.

FIG. 4 is a side view showing an example of a conventional fixing device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Toner image 2 ... Recording material (paper) 3, 4, 6, 7, 8, 9 ... Heating roller (soft roller) 5 ... Buffer means (buffer plate) 10, 11 ... Heating roller (hard roller)

Claims (6)

[Claims] An elongating recording material having a pair of heating rollers supported so as to be able to be pressed against each other and holding an unfixed toner image on both sides while nipping and transporting the recording material at a pressure contact portion of the pair of heating rollers; In a fixing device for fixing a toner image to a recording material, two pairs of heating rollers provided in a front-rear relationship along a recording material conveyance direction are provided, and at least a first fixing is performed on at least the conveyed recording material. Wherein the heating roller pair is a heating roller pair having a rubber layer provided on a cored bar. A second heating roller pair provided downstream of the first heating roller pair in a recording material conveying direction is a heating roller pair having a rubber layer provided on a cored bar. The fixing device according to claim 1, wherein: 3. A heating roller pair provided with a resin layer on a cored bar, wherein the second heating roller pair provided downstream of the first heating roller pair in the recording material conveyance direction. The fixing device according to claim 1, wherein: 4. The fixing device according to claim 1, wherein the first heating roller pair and the second heating roller pair have different surface hardness and / or surface material. 5. The fixing device according to claim 1, wherein a fixing temperature of the first heating roller pair is set to a value lower than a fixing temperature of the second heating roller pair. 6. A printing apparatus according to claim 1, further comprising a buffer means between the first heating roller pair and the second heating roller pair, the buffer means being swingably supported on a recording material surface and absorbing slack of the recording material. The fixing device according to claim 1, wherein