JPS61149975A - Image forming device - Google Patents

Abstract

PURPOSE:To carry out proper fixing operation by providing a means which performs control so as to vary fixation conditions during the fixation of each toner image. CONSTITUTION:A fixing device 20 consists of a fixing roller 22 and a pressure roller 24 which contacts and leaves the roller freely. The fixing roller 22 is made of a metallic pipe and has a heat source 26 internally and this heat source 26 is a two-stage change-over type heat source consisting of a main heating body 26a and a subordinate heating body 26b. The surface temperature of the fixing roller 22 is controlled by a thermistor 28 to a set temperature and the roller is rotated by a driving roller as shown by an arrow (a), so that the pressure roller 24 rotates as shown by an arrow (b). A heat-resisting elastic body is formed on the surface of the pressure roller 24 and fitted rotatably onto the shaft 32 of a rocking lever 30, and when a cam plate 44 to which a cam roller 42 is fitted is driven as shown by an arrow (c) to rotate a cam lever 40 around a shaft 38 as shown by an arrow A, the motion of the rocking lever 40 rotates a rocking lever 30 clockwise through a spring 36 to press the pressure roller 24 against the fixing roller 22, which is put in motion.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention generally relates to an image forming apparatus that forms a powder image, that is, a toner image using two or more types of toner having different fixing properties, and performs transfer and fixing processes for each toner image. Image forming apparatuses, such as color electrophotographic copying machines that are equipped with a plurality of developing devices and produce multicolor or full-color copies of two or more colors, or color recording devices with computer output units. It is related to. Although the following description will be made in connection with a color copying apparatus, the present invention is not limited thereto as described above.

Ryokanji 1j Conventionally, in image forming devices such as copying machines,
Recently, the demand for color copying and printing has increased rapidly not only in specialized fields but also in general office fields. The demand for multicolor copying and printing has increased significantly.

On the other hand, it is preferable to use a one-component toner as the toner from the viewpoint of simplifying and downsizing the developing device and the entire copying device as well as ease of operation, and magnetic toner is widely used in current copying devices.

However, since magnetic toner contains magnetite as a component, it is suitable for use as a black toner, but is not suitable for use as a brightly colored toner. Therefore, nonmagnetic one-component toners that do not contain magnetite are used for color toners such as red, blue, and green.

As described above, the black toner and the other color toners have different compositions, and as a result, the black toner and the color toners have different fixing properties. In general, black toner using magnetic toner has poorer fixing properties than color toner. For example, the appropriate fixing temperature for magnetic toner consisting of 100% styrene-acrylic resin, 6-9% carbon, and 60-80% magnetite in weight ratio However, in the case of a non-magnetic toner consisting of 100% styrene-acrylic resin and 6 to 9% carbon by weight, the suitable temperature for fixing is 190°C.

None of the conventional copying apparatuses equipped with multiple toners, that is, multiple developing devices, have focused on the differences in fixability of the toners. Therefore, image formation is performed using multiple toners with different fixability, and If the fixing temperature is set according to the toner with good fixing properties, the image created by the toner with poor fixing properties will be unfixed. If the energy is increased, it will cause excessive fixation compared to other toners with good fixing properties, which will increase the curling of transfer paper, recording paper, etc., which will hinder the conveyance of the paper, and will also cause problems from an energy-saving perspective. was there.

Furthermore, if you heat and fix at a higher temperature than the appropriate temperature.

High-temperature offset occurs, and the toner melted by the heat of the fixing device adheres to the surface of the fixing roller, resulting in a decrease in image density and staining of the fixing roller.The latter, in particular, causes a decrease in the thermal efficiency of the fixing device. There is a problem in that the surface of the subsequent transfer material is stained.

On the other hand, if the toner is heated and fixed at a temperature lower than the appropriate temperature, the toner is not sufficiently melted, so that the toner, which is difficult to adhere to the transfer material, adheres to the fixing roller side.

This causes a so-called low-temperature offset phenomenon. This low temperature offset also causes the same problems as the high temperature offset.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus that can perform an extremely appropriate fixing operation even when toners having different fixing properties are used.

Another object of the present invention is to provide an image forming apparatus that minimizes the energy required for fixing.

- Divination - The above object is achieved by the present invention. To summarize, the present invention relates to an image forming apparatus that forms an image using two or more types of toners having different fixing properties.

According to a preferred embodiment of the present invention, which is an image forming apparatus characterized by having means for controlling so as to change the fixing conditions at the time of fixing each toner image, the fixing conditions at the time of fixing each toner image are as follows: It is controlled by a signal from a detection means for classifying each developing device.

As described above, the image forming apparatus according to the present invention can be suitably embodied in a multi-color or full-color electrophotographic copying device, a color recording device of a computer output section, etc., but in this embodiment, A case will be described in which the present invention is a copying apparatus that obtains copies of two-color images, such as black and red. Further, such a color electrophotographic copying apparatus can perform various electrostatic latent image forming processes, such as primary charging-2.
The so-called N
P process or primary charging-color separation exposure steps,
Although the so-called Carlson process and others may be used, in this embodiment, an electrophotographic copying apparatus to which the Carlson process is applied will be described.

FIG. 1 shows a schematic cross-sectional view of a color electrophotographic copying apparatus for obtaining two-color images of black and red.

First, the overall configuration of a color electrophotographic copying apparatus will be described. A photosensitive drum 1 having an electrophotographic photosensitive layer formed on its surface is disposed approximately in the center of the copying apparatus. The photosensitive drum l has a rotation support shaft (with a rotation center 0) in a well-known manner.
In this embodiment, the photosensitive drum 1 is rotatably and removably attached to a drum (not shown), and the photosensitive drum 1 rotates in the direction of arrow X, that is, clockwise in FIG.

A primary charger 2 is located approximately directly above the photosensitive drum 1, a developing device 3 and 4 is located on the right side of the photosensitive drum 1 in FIG. 1, and a transfer discharger 5 and a photosensitive drum 1 are located approximately directly below the photosensitive drum 1. A cleaning device 6 is disposed on the left side in FIG. Further, an optical system 7 is disposed in the upper part of the electrophotographic copying apparatus, and projects the original image onto the photosensitive drum l at an exposure section E located between the primary charger 2 and the developing device 3. It is configured as follows. Optical system 5 can use any optical system. Further, a light 171B is provided between the primary charger 2 and the cleaning device 6 for erasing residual charges on the photosensitive drum 1.
is provided.

Since the color copying apparatus described here is a color electrophotographic copying apparatus for obtaining two-color images of black and red as described above, two developing devices are arranged, but the present invention is limited to this configuration. However, it is also possible to have three or more developing devices.

The operation of the color electrophotographic copying apparatus configured as described above will be briefly explained.

The photosensitive drum 1 begins to rotate in the direction of arrow X at the start of operation, and is charged by the primary charger 2 .

The charged photosensitive drum l further rotates, and an optical image is slit-exposed at the exposure section E by the action of the optical system 7, so that electrostatic latent images of each color are formed on the photosensitive drum l. photosensitive drum l
The upper latent image is then developed by rotation of the photosensitive drum 1, which is then placed in the developing device 3.4.

brought to the image area. The photosensitive drum l in the developing area
The upper electrostatic latent image is developed as a toner image by a selected one of the developing devices 3.4 (in FIG. 1, the developing device 3 is moved to the developing position by the cam 3A). Ru.

The toner image on the photosensitive drum is transferred to a transfer area T where a transfer discharger 5 is disposed, and a transfer material P is fed from a paper feeder (not shown) and fed by registration rollers 9 in a timely manner.
transcribed into. The transfer material P carrying the toner image is then transported by the transport device 10 to the fixing device 20 and fixed thereon. Details of the fixing device 20 will be described later.

After the photosensitive drum 1 is subjected to the action of the cleaning device 6 and the light source 8, it undergoes the next image forming process again.

Next, the fixing device 20 suitably used in the electrophotographic copying apparatus according to the present invention will be described.

An embodiment of the fixing device 20 is illustrated in FIG. 2. In this embodiment, the fixing device 20 includes a fixing roller 22 and a pressure roller 24 provided so as to be able to move toward and away from the fixing roller 22.
and.

The fixing roller 22 is a metal tube with a heat source 26 inside.
has. As shown in FIG. 3, the heat source 26 is a two-stage switchable heat source including a 2N type heat source including a main heating element 26a and a sub-heating element 26b. Further, the surface temperature of the fixing roller 22 is controlled to a set temperature by a thermistor 28.

The fixing roller 22 is rotated in the direction of arrow a by a drive motor (not shown). Therefore, when the pressure roller 24 is engaged with the fixing roller 22, it rotates in the direction of the arrow. Pressure roller 24 can also be driven independently if desired.

A heat-resistant elastic body is formed on one surface of the pressure roller 24,
It is rotatably attached to the swing lever 30 via a shaft 32. One end of the swinging rail μ30 is pivotally connected to the shaft 34, and one end of a spring means 36 is connected to the other end. The spring means 36
The other end is a cam lever 40 that is swingable around the shaft 38.
attached to one end of the The other end of spring means 36 is also operatively engaged with cam roller 42.

Accordingly, when the cam plate 44 to which the cam roller 42 is mounted is driven in the direction of arrow C by a drive motor (not shown), the cam lever 40 rotates in the direction of arrow A about shaft 38. The movement of the rocking lever 40 causes the rocking lever 30 to rotate clockwise in FIG. 2 via the spring means 36, thereby forcing the pressure roller 24 to move toward the fixing roller 22. At this time, the force with which the pressure roller 24 is pressed toward the fixing roller 22, that is, the pressing force is applied to the cam plate 44.
This can be done by controlling the amount of rotation. The amount of rotation is controlled by actuators 46 and 48 provided on the cam plate 44.
This is achieved by detecting with the sensor 50. Second
It will be appreciated that the figure shows the engagement of the fuser roller 22 and the pressure roller 24 in a low pressure state, and in FIG. 4 the engagement is in a high pressure state.

On the other hand, as shown in FIG. 5, the cam plate 44 is
When the cam roller 42 is reversed in the direction of , the pressing force of the cam roller 42 against the cam lever 40 is released.

Therefore, the pressing force of the pressure roller 24 against the fixing roller 22 is also lost, and the pressure roller 24 is separated from the fixing roller 22 due to the weight of the pressure roller 24, the spring force of the spring means 36, and the like.

In the above configuration, in the present invention, if image formation is performed using toner with poor fixing properties, the fixing device M2
The fixing condition of 0 is that the heat source 26 is the main heating element 26a.
and the sub-heating element 26b are used, and the pressing force of the pressure roller 24 against the fixing roller 22 is set to a high pressure state.

When image formation is performed using a toner with good fixing properties, the fixing conditions of the fixing device 2o are as follows: The fixing conditions of the fixing device 2o are as follows. The pressing force of the fixing roller 24 against the fixing roller 22 is kept in a low pressure state. In some cases, the pressure roller 24
The pressing force on the fixing roller 22 will be in a high pressure state.

Generally, the factor that determines the degree of fixing is called the nip amount, and it is known that the nip amount is composed of time x heating amount x nip width. Fixing is performed under the conditions of high roller pressure and high temperature, while in copying using toner with good fixing properties, fixing is performed under conditions of low pressure and low temperature. Therefore, fixing is performed under different conditions with respect to the nip amount.

As mentioned above, when copying is performed using toner with poor fixing properties, proper fixing operation can be achieved by changing the pressure and heating temperature of the fixing device and making them higher than when copying with toner with good fixing properties. It is done. However, according to the present invention, it is not necessary to change both the pressing force and the heating temperature, and only the factors that do not increase curl, such as curl, are changed depending on the physical properties of the toner and recording paper used, and the absolute nip amount is changed. Just do it.

The fixing conditions of the fixing device 20 configured as described above are controlled by signals from the classification detection means provided in the developing devices 3 and 4. The detection means can have any configuration, but an example thereof is as shown in FIG. It is also possible to provide a configuration in which detection plates 3a or 4a are provided at different positions on the sides of the copying apparatus, and the detection plates are detected by a plurality of photointerrupters 3b and 4b provided in the main body of the copying apparatus. The array of photointerrupters 3b and 4b will be provided at each developing device installation position where a developing device is installed.

Effects of the Invention Since the image forming apparatus according to the present invention is configured as described above, it is possible to perform an extremely appropriate fixing operation even when toners with different fixing properties are used, and the energy required for fixing is minimized. be able to. Further, according to the present invention, it is possible to reduce the occurrence of curls, wrinkles, etc. in sheets such as transfer paper and recording paper used. Furthermore, according to the present invention, it is possible to prevent so-called high-temperature offset and low-temperature offset in the fixing device, thereby preventing a decrease in image density and staining of the fixing roller, as well as a decrease in thermal efficiency of the fixing device and staining of the subsequent transfer material. can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of a color electrophotographic copying apparatus which is an embodiment of an image forming apparatus according to the present invention. FIG. 2 is a schematic cross-sectional view of one embodiment of the fixing device used in the copying machine of FIG. 1. FIG. 3 is a sectional view of a heat source used in the fixing device of FIG. 2. FIG. 4 is a diagram similar to FIG. 2, and shows a case where the pressing state between the pressure roller and the fixing roller is high. FIG. 5 is a diagram similar to FIG. 2, and shows a state in which the pressure roller is separated from the fixing roller. 3.4: Developing devices 3a, 4a; 3b, 4b = Developing device classification detection means 20: Fixing device 22: Fixing roller 24: Pressure roller Figure 2 Figure 3 6b1 Figure 4 Figure 5 Foot procedure correction form (Method) % formula % Relationship with the case of the person making the amendment As per the patent applicant's appendix j:;, -
,,・, ”--'+() ・ (-) "Brief explanation of drawings" should be corrected as follows. (1) Between lines 4 and 5 on page 15 of the specification: ``Figure 6 is a schematic perspective view of the photosensitive drum and the developing device, illustrating how the developing device is inserted into and taken out of the main body of the copying apparatus.'' Insert.

Claims (1)

[Scope of Claims] 1) An image forming apparatus that forms images using two or more types of toners having different fixing properties, characterized by having means for controlling fixing conditions at the time of fixing each toner image to be changed. image forming device. 2) The image forming apparatus according to claim 1, wherein the fixing conditions at the time of fixing each toner image are controlled by a signal from a detection means for classifying each developing device.