JPH04333884A - Fixing device - Google Patents

Abstract

PURPOSE:To fix a toner image under conditions fit for the image. CONSTITUTION:Plural fixing condition changing means H(1)-H(n) arranged in a direction orthognally crossed with the carrying direction of a transfer material P and a fixing temperature control means 10 for controlling the fixing condition of the changing means based on image information are provided in a fixing device 1. Thus, a graphic image and a solid image are fixed at an appropriate temperature and a dot is prevented from being battered.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device for an image forming apparatus such as a printer, a copier, or a facsimile machine.

0002

2. Description of the Related Art Conventionally, it has been widely known that the above-mentioned fixing device is equipped with a heating roller having a heat source and a pressure roller in contact with the heating roller. In this fixing device, the transfer material is While being held and conveyed, the unfixed toner is heated and melted to be fixed.

0003

However, the fixing device described above uses a single heat source to fix toner in all areas under substantially the same conditions. Therefore, there has been a problem in that it is not possible to faithfully reproduce an image in which different images coexist, such as an image in which a part of a character image includes a graphic image. That is, in the case of a graphic image made up of fine dots, if the toner is heated too much, the dots will be crushed or the dots will overlap, resulting in an unclear image, and in the case of a solid image, if the toner is not heated sufficiently, density unevenness will occur. Therefore, if an image in which a graphic image and a solid image are mixed is fixed under the same conditions, the image quality of one of them will deteriorate.

0004

[Means for Solving the Problems] The present invention has been made to solve the above problems, and includes a plurality of fixing condition changing means disposed in a fixing device in a direction perpendicular to the conveying direction of the transfer material; and control means for controlling the fixing condition changing means based on image information.

[0005]

[Operation] According to the above-mentioned fixing device, the fixing conditions are adjusted by the plurality of fixing condition changing means based on the image information. The toner is also fixed on the image under conditions that match those conditions.

[0006]

[Embodiment] Hereinafter, a specific example of the above-mentioned fixing device will be described with reference to FIGS. 1 and 2. In these figures, 1
is a fixing device of the present invention. Rollers 2, 3, and 4 are arranged parallel to each other, and roller 2 is connected to a drive source (not shown). 5 is a heating element, n heating elements H(1)
, ~, H(n). The heating element 5 is arranged in an area surrounded by the rollers 2, 3, and 4, and the heating portions of the heating elements H(1) to H(n) are in contact with the upper outer peripheral surface of the roller 4. . 6 is an endless heat-resistant film,
It surrounds the rollers 2 and 3 and the heat generating element 5, and is held between the contact part between the heat generating part of the heat generating element 5 and the roller 4. 8 is a guide plate,
One end thereof is located near a contact portion 7 (hereinafter referred to as "nip portion 7") between the roller 4 and the heat-resistant film 6. Reference numeral 9 denotes an image density reading device, which is composed of n sensors S(1) to S(n) each having a light emitting element and a light receiving element, and is mounted parallel to the roller 2, facing the guide plate 8. It is located. Further, the sensors S(1), . . . , S(n) are arranged on the same straight line as the heating elements H(1), .about., H(n), respectively. 10 is a control device, and this control device 1
0 inputs signals from sensors S(1), .about., S(n) and outputs remote signals of heating elements H(1), .about., H(n). The control device 10 also includes a RAM.
11 and ROM 12 are connected.

In the fixing device 1 having the above configuration, when the roller 2 is rotated in the direction of the arrow by a drive source (not shown), the heat-resistant film 6 is driven to rotate in the same direction, and the rollers 3 and 4 are rotated in accordance with the rotation of the film 6. do. Further, a voltage determined based on a signal from the control device 10 is applied to each of the heating elements H(1), -, H(n) of the heating element 5, and the heating element is maintained at a predetermined temperature state. .

The transfer material P having unfixed toner on its upper surface is conveyed along the guide plate 8 from the left side in the figure. Also,
The transfer material P that has passed through the guide plate 8 is held between the heat-resistant film 6 and the roller 4 at the nip portion 7 and is conveyed to the right side in the figure. At this time, the sensors S(1) to S(n) illuminate an image passing through their detection positions, and output a voltage signal corresponding to the amount of reflected light to the control device 10. That is,
The image density of the toner image attached to the transfer material P is measured. In the control device 10, sensors S(1), ~, S(n)
Based on the output voltage from the ROM 12, fixing temperature data is created according to a program written in the ROM 12, and is stored in the RAM 11. And sensor S(1), ~
, S(n) arrives at the nip section 7, the corresponding fixing temperature data is read from the RAM 11, and based on this fixing temperature data, the heating elements H(1), -
, (n). Therefore, the image passing through the nip portion 7 is fixed under the most suitable conditions for the image.

A second embodiment will be explained with reference to FIGS. 3 and 4. In this second embodiment, the fixing device of the present invention is applied to a laser printer, and image density data of an unfixed toner image is obtained from image data input from a host computer to the laser printer. Therefore, unlike the first embodiment described above, the fixing device 1a does not include the image reading device 9, and instead only a sensor SS for detecting the leading edge of the transfer material P is provided. Further, as shown in FIG. 4, the laser printer controller 16
The laser emission data from the
(1) It is designed to be output to 13.

In the fixing device 1a having the above configuration, laser emission data, that is, image data is output to the RAM (1) 13 as the image forming device is driven, and this image data is processed when the data of a plurality of scanning lines are complete. Control device 1
Output to 0a. The control device 10a replaces the image data with image information for each block corresponding to the heating elements H(1), -, H(n), and creates corresponding fixing temperature data according to the program written in the ROM 15. , writes this fixing temperature data into RAM (2) 14. On the other hand, a toner image is created by a normal electrophotographic method based on the image data, and when the transfer material on which the toner image is transferred is conveyed to the fixing device 1a, the leading edge of the transfer material is detected by the sensor SS. Ru. The control device 10a includes a sensor S
When the tip detection signal from S is input, the above RAM (2
) 14, and set the temperatures of the heating elements H(1), . . . , (n) according to the data. Therefore, the image passing through the nip portion 7 is fixed under the most suitable conditions for the image.

FIG. 5 shows the temperature set based on the image data and the heating element H(
An example of fixing temperature data regarding 1) is shown below. Here, the upper part of the figure shows an example in which laser emission data, that is, image data written in RAM (1) 13 is converted into actual fixing temperature according to the program in ROM 15, and this fixing temperature data is written in RAM (2) 14. shows. On the other hand, the lower part of the figure shows an example in which the fixing temperature data is written into the RAM (2) 14 as an increase/decrease value with respect to a certain standard temperature.

In the third embodiment, image data is obtained from reflected light of light illuminating an original in an analog copying machine. That is, as shown in FIG.
0, the original placed on the original table glass 21 is illuminated by the exposure lamp 22, and the reflected light is exposed to the charged area of the photoreceptor 25 through the lens 23, half mirror 24, etc., and an electrostatic latent image is formed. It is formed. After the electrostatic latent image is visualized as a toner image in the developing device 26, the electrostatic latent image is transferred to the transfer charger 27.
The image is transferred onto a sheet of paper conveyed from the sheet feeding section 28 at a portion opposite to the sheet feeding section 28. The paper onto which the toner image has been transferred is transported by a transport device 29 to a fixing device 1a having the configuration shown in FIG. 3, where the toner image is heated and fixed, and then discharged onto a tray 30.

On the other hand, a part of the light incident on the half mirror 24 passes through the half mirror 24 and is transmitted to an image reading device 31 consisting of a plurality of CCD sensors CS(1), -, (n).
is incident on the In the control device, as shown in FIG.
Create document image data and fixing temperature data from the outputs of the D sensors CS(1), ~, CS(n), and calculate the heat generation temperature of the heat generating elements H(1), ~, H(n) based on this. Control. Note that specific image data processing is performed in the same manner as in the second embodiment.

In the above embodiments, the present invention was applied to a heating type fixing device, but the present invention can also be applied to a pressure type fixing device 40 shown in FIG. This fixing device 40 includes an upper fixing roller 41 fixed at both ends, and pressure devices 46, 47, 4 at both ends and the center.
a lower fixing roller 42 supported by the upper fixing roller 41 and in pressure contact with the upper fixing roller 41; and a sensor 43 located near the nip between these rollers 41 and 42 for reading image data on the transfer material conveyed from the direction of arrow a. , 44, 45.

[0015] In the above fixing device, the sensors 43, 44, 4
5 reads image data of a document conveyed from the direction of arrow a. The pressure devices 46, 47, and 48 adjust the force applied to the lower fixing roller 42 based on the image data. For example, if the toner image is a high-density image such as a solid image, increase the pressure force to fix the toner uniformly, and if the toner image is a low-density image such as a line image, reduce the pressure force to fix the toner uniformly. prevent collapse.

[0016] Furthermore, if the images at the edges and the center are different,
The pressure of the pressure device is adjusted to perform fixing at a pressure that matches the image quality. For example, if the image detected by the sensor 43 is a solid image, the pressing force of the pressing device 46 is increased, and if the image detected by the sensors 44, 45 is a line image, the pressing force of the pressing device 47, 48 is increased. Reduce the pressure to prevent lines from collapsing.

Note that the durability of the roller can be improved by providing a member with a high reflectance below the sensor and reducing the pressing force of the pressing device during standby.

[0018]

As is clear from the above description, the fixing device of the present invention includes a plurality of fixing condition changing means, a control means for controlling the fixing condition changing means based on image information,
It is equipped with Therefore, toner images containing a mixture of character images, graphic images, solid images, etc. are fixed on the transfer material under conditions suitable for each image, and for example, in the case of an image composed of small dots, each dot is not crushed. Reproduced in its proper size,
In addition, in a line image, the lines are reproduced with appropriate thickness, so the created image is faithful to the original. In particular, in devices that form images as a collection of dots of different colors, such as full-color image forming devices, each color dot is maintained at the correct size, so colors that are faithful to the original can be reproduced. Reproduction becomes possible.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a fixing device according to a first embodiment.

FIG. 2 is a control circuit diagram of the first embodiment.

FIG. 3 is a perspective view of a fixing device according to a second embodiment.

FIG. 4 is a control circuit diagram of a second embodiment.

FIG. 5 is a diagram showing a storage state of fixing temperature data.

FIG. 6 is a sectional view of the copying machine.

FIG. 7 is a control circuit diagram of a third embodiment.

FIG. 8 is a perspective view of a fixing device according to a fourth embodiment.

[Explanation of symbols]

1... Fixing device, 2, 3, 4... Roller, 5... Heating element, 6...
Heat-resistant film, 7... Nip portion, 8... Guide plate, 9... Image reading device, 10... CPU, H(1), ~, H(n)... Heat generating element, S(1), ~, S(n)... sensor.

Claims (1)

[Claims] 1. A fixing device of an image forming apparatus that fixes unfixed toner held on a transfer material, comprising: a plurality of fixing condition changing means disposed in a direction perpendicular to the conveying direction of the transfer material; A fixing device comprising: a control means for controlling the fixing condition changing means based on the above.