JPS6313088A - Full-color copying machine - Google Patents

Abstract

PURPOSE:To easily select the glossiness of a copy image according to user's preference by varying heating value supplied from a roller couple to transfer paper which is fixed by a fixing device. CONSTITUTION:A toner image fixed on transfer paper is supplied with sufficient heat and melts and when its plane becomes smooth, a glossy image is obtained. One terminal of a pressure spring 10 is engaged to the pin 8a of an eccentric cam 8 and a pressure roller 7 is pressed against a fixing roller 6 through a pressure lever 9. When the cam 8 is rotated to move up the pin 8a, the is pressed correspondingly and nip width b2 increases, so that the heating value supplied to the transfer paper increases. For the porpose, the nip width or/and the set temperature of the roller are varied to easily select the glossiness of an image according to the user's preference.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a full-color copying machine, and more particularly to a copying machine in which the gloss of an image fixed by a heat roller fixing device can be changed according to preference.

The image quality of paintings and photographs is determined by the color tone (hue, brightness,
It is known that the gloss of the image has an influence as well as the saturation. Photographic paper is commercially available in different gloss states such as gloss, semi-gloss, matte, and matte, and is selected and used according to the wishes of customers and users.

On the other hand, black-and-white copies made by an electrophotographic copying machine do not have pictorial elements, and it is sufficient if the density and contrast of the original, which mainly consists of line drawings, can be roughly reproduced.

Full-color copying machines that use electrophotography.

The M manuscript is color-separated using blue, green, and red color separation filters and sequentially exposed to light on a photoreceptor, and the electrostatic latent images obtained are developed in yellow, magenta, and cyan, which are complementary colors to the color separation colors, respectively. The three-color toner images thus formed are superimposed and transferred onto a single sheet of transfer paper, and this is fixed to create a copy of the same full-color image of the original. The fixing device used in this case is similar to the heat roller fixing device often used in black-and-white copying machines, in which transfer paper carrying an unfixed toner image is placed in pressure contact with each other, has a built-in heat source in at least one side, and transfer paper carrying an unfixed toner image is attached to both sides. Generally, a structure is adopted in which the transfer paper and toner are conveyed by being pinched by the pressure contact portion of the rollers, and heat is applied to the transfer paper and the toner by a pair of rollers to melt the toner and fuse it to the surface of the paper.

In full-color copying machines developed based on black-and-white copying machines, efforts have been made to improve color reproducibility, but not much consideration has been given to gloss. However, recently, color copies made by full-color copying machines are required to have image quality as high as that of photographs or printing, and it has become impossible to maintain the gloss of a single image. The sensory atmosphere of an image differs depending on the presence or absence of gloss on the image surface. Therefore, there has been a demand for a full-color copying machine that allows the user to arbitrarily select the gloss of an image, taking into consideration the balance with the gloss of the transfer paper itself.

SUMMARY OF THE INVENTION In view of the above-mentioned circumstances, it is an object of the present invention to provide a full-color copying machine that has a simple configuration and can easily change the glossiness of a copied image according to the user's preference.

In order to achieve the above object, the present invention transfers toner images of a plurality of colors onto the same transfer paper in a superimposed manner, and conveys the unfixed transfer paper by sandwiching it between a pressure contact portion of a pair of rollers each having a heat source on at least one of them. A full-color copying machine that performs fixing is characterized in that means is provided for varying the amount of heat applied by the pair of rollers to the transfer paper to be fixed by the pair of rollers of the fixing device.

The inventor of the present invention conducted experiments on factors that affect the gloss of copied images obtained with the full-color copying machine configured as described above, and as a result of repeated studies, it was found that the amount of fixing has a large effect on the gloss of copied images. It turned out that there was. The glossiness of a copied image is greatly influenced by the smoothness of the surface (toner adhering surface).

The smoothness of the image surface depends on how much the toner is melted. For example, FIG. 1(a) shows the state of the toner image surface when a small amount of heat is applied to the transfer paper 30 and the toner 31 by a roller.Fixing is performed, but the toner 31 is completely The particles are not melted and unevenness of the particles remains on the image surface, which causes incident light to be diffusely reflected, resulting in a lackluster image. On the other hand, if a sufficient amount of heat a2 is applied from the roller to the transfer paper and toner, the first
As shown in Figure (b), the toner on the upper surface is completely melted and is pressed by the roller, so that the unevenness of the particles disappears, and the surface of the toner image 31 becomes smooth, and the light incident from one direction is uniform without being diffusely reflected. Reflects in different directions, producing a glossy image. From this result, the relationship between the amount of heat applied and the gloss of the image can be qualitatively shown in a graph as shown in FIG. In other words, fixing is not performed until the amount of heat applied to the transfer paper and toner by the fixing and pressure roller reaches a certain amount A, and when the amount of heat exceeds that amount, fixing is performed, and in that case, the gloss of the image surface is As the amount of heat increases - therefore the gloss increases. In the figure, a and ta represent the amount of heat applied to the transfer paper in the above experiment. If the amount of heat is less than A, fixing will not be completed completely, so the presence or absence of gloss on the image surface does not matter.

A heat roller fixing device passes a transfer paper between a pair of rollers rotating in pressure contact with each other at a constant rotational speed, and heats the transfer paper and toner image to melt and fix the transfer paper and toner image.

Therefore, in order to change the amount of heat given from the roller pair to the transfer paper and the toner image carried on it, it is necessary to change the set temperature of the rollers or change the time that the transfer paper is in contact with the pressure contact part of the roller pair. Bye. Or you can change both at the same time.

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

FIG. 3 shows an example of a full-color copying machine to which the present invention is applied.

Laser light modulated with digital image signals of images to be developed in magenta, cyan, yellow, and black is sequentially input to the laser writing device 2, and at the writing position, the photoreceptor drum 1
Writing is performed to form an electrostatic latent image on the photoreceptor drum. Each electrostatic latent image is formed in the developing devices 3M and 3C of the developing device 3, respectively.
, 3Y, and 38, the toner images of each color are developed and formed by a transfer drum 4 which has the same diameter as the photoreceptor drum 1 and is wound around a transfer drum 4 that rotates in the same direction and at the same circumferential speed at the transfer position in synchronization with the photoreceptor drum 1. The toner images are superimposed and transferred onto the paper, and when the transfer of the four-color toner images is completed, the transfer paper is separated from the transfer drum 4 and fixed by the fixing device 5 to produce a color print. The fixing device 5 includes a fixing roller 6 having an internal heat source and a pressure roller 7 that can be pressed against the fixing roller 6.

FIG. 4(a) shows that by changing the contact width (width) between the fixing roller 6 and the pressure roller 7, the time period during which the transfer paper being conveyed while being sandwiched between these rollers is in contact with the pair of rollers is shown. FIG. 4 is a diagram showing an example in which the glossiness of one image is changed by changing the amount of heat applied from the roller pair to the transfer paper and toner. The pressure roller 7 is pressed against the fixing roller 6 by a pressure spring 10 via a pressure lever 9. Since the surface layer of the pressure roller rough is made of a heat-resistant elastic layer such as silicone rubber, the elastic layer changes depending on the magnitude of the fixing pressure applied between the pressure roller 7 and the fixing roller 6. The contact width changes due to elastic deformation. As a means for changing the fixing pressure, in this embodiment, one end of the pressure spring 10 is hooked to a pin 8a installed around the eccentric cam 8, and the eccentric cam 8 is moved in advance by a pulse motor according to the gloss level. By rotating the pressure spring 10 by a set angle, the length of the pressure spring 10 can be changed, thereby changing the fixing pressure and thus the contact width. In FIG. 4(a), the pin 8a that engages the pressure spring 1o is located approximately to the side of the axis of the eccentric cam 8, and the contact width between the fixing roller 6 and the pressure roller 7 is . , as shown in Figure 4(b), pin 8
When the eccentric cam 8 is rotated by a pulse motor so that the position a is above the axis of the cam 8, the length of the pressure spring 10 becomes longer, the fixing pressure increases, and the contact width increases to b2. .

In another embodiment shown in FIG. 5, the fixing pressure is changed by directly rotating the pressure lever 9 with an eccentric cam 11. In the embodiment, the fixing pressure is applied directly to the shaft of the pressure roller 7 by the eccentric cam 12.
It is made to change by engaging with it.

In each of the above embodiments, image gloss is achieved by rotating the eccentric cam 7.
<This is done by controlling the rotation angle of the Luss motor, that is, the number of pulses. FIG. 7 shows an example of an operation unit of a copying machine in which the gloss level can be selected, and an image gloss selection key 14 is provided on the panel 13. In this example, the gloss selection key is above gloss.

Although three are provided for the middle and bottom, there may be more or two, or a rotary switch or the like may be used.

FIG. 8 is a circuit diagram for changing the contact width, and FIG. 9 is a flow chart of the contact width changing operation.

When the operator selects the gloss level of the copied image by pressing one of the selection keys 4 on the operation panel 13.

The input is input to the CPU 20 shown in the circuit diagram of FIG. 8, drives the pulse motor 22 via the driver 21, and returns it to the reference position. When the sensor 23 detects that the pulse motor 22 has returned to the reference position, the pulse motor 11 stops. . If the selected glossiness is in the standard state (low glossiness, small contact width between the rollers), the pulse motor 22 will remain stopped, and if any other glossiness is selected, the The pulse motor rotates by a preset number of pulses, and when that number is reached, the motor stops and copying becomes possible. changes.

FIG. 10 shows a known setting of an embodiment in which the glossiness of an image is changed by changing the amount of heat applied to the transfer paper to be fixed and the toner image carried thereon by changing the set temperature of the fixing roller. It is a circuit diagram regarding temperature change. Selection switch SWI.

SW2. SW3 (corresponds to selection key 14 in Fig. 7)
is provided in contact with the fuser roller and the resistor selected by
The resistance of the thermistor 24, whose temperature changes depending on the surface temperature of the fixing roller, is input to the comparator amplifier 25, these are compared, and the difference is amplified and output.
7 on and off to maintain the temperature of the fixing roller so that the amount of heat required to obtain the required glossiness is transmitted to the transfer paper passing through the fixing roller and the pressure roller.

In each of the above embodiments, in order to change the amount of heat transferred from the pair of fixing rollers to the transfer paper and toner, either the contact width of the pair of rollers or the set temperature of the fixing roller is varied. , it is also possible to change both at the same time to change the amount of heat transferred.

As described above, according to the present invention, a full-color copy image obtained by a full-color copying machine can be changed to a desired gloss level with a simple configuration and operation, and the image quality can be improved. .

[Brief Description of the Drawings] Figures 1 (a), (b) and 2 are explanatory diagrams explaining the present invention in detail, and Figure 3 shows the configuration of an example of a full-color copying machine to which the present invention is applied. Cross-sectional views shown in Fig. 4 (a) and (b)
5 is a sectional view showing another embodiment of the present invention, FIG. 6 is a sectional view showing still another embodiment, and FIG. 7 is a sectional view showing each of the above embodiments. FIG. 8 is a circuit diagram showing an eccentric cam drive circuit of each of the above embodiments, FIG. 9 is a flowchart thereof, and FIG. 10 is a plan view showing an example of an operation panel used for controlling the embodiments. FIG. 7 is a fixing roller temperature control circuit diagram of another embodiment. 1... Photosensitive drum 3... Developing device 4... Transfer drum 5... Fixing device 6... Fixing roller
7... Pressure roller 8.11.12... Eccentric cam 9... Pressure lever 10... Pressure spring 13...
・Operation panel 22... Pulse motor 24... Thermistor 27... Heater Fig. 1 (a) (b) Light No. 21] 1 Heat amount □ 6.3 Fig. 4 (a) (b) 5th Figure 6

Claims (4)

[Claims] (1) In a full-color copying machine in which toner images of multiple colors are superimposed and transferred onto the same transfer paper, and fixed by being held and conveyed by a pressure contact portion of a pair of rollers each having a heat source on at least one side, the above-mentioned roller of the above-mentioned fixing device A full-color copying machine characterized by being provided with means for varying the amount of heat applied by a pair of rollers to a transfer sheet fixed by the pair of rollers. (2) A full-color copying machine according to claim 1, wherein the means for varying the amount of heat applied to the transfer paper by the pair of rollers is a means for varying the set temperature of the rollers. . (3) According to claim 1, the means for varying the amount of heat applied to the transfer paper by the roller pair is a means for varying the pressure contact width of the pressure contact portion of the roller pair. full color copying machine. (4) A patent claim characterized in that the means for varying the amount of heat applied to the transfer paper by the roller pair is a means for varying both the set temperature of the rollers and the pressure contact width of the pressure contact portion of the roller pair. A full-color copying machine according to scope 1.