JPS607796B2 - pressure fixing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pressure fixing device that fixes a toner image formed on copy paper by electrophotographic copying or the like by passing it between fixing rolls that are brought into contact with each other.

Conventionally used fixing methods include a fixing method using heat such as roller fixing and atmospheric fixing, and a method of dissolving and fixing a toner powder image using solvent vapor.

These fusing methods require time to warm up the roll and atmosphere to a set temperature.

For this reason, it is necessary to keep the power on even when not copying, which consumes power and has an adverse effect on other devices due to an increase in the internal temperature of the machine. Furthermore, if paper jams occur in the fixing section, it may burn or scorch, causing a fire. On the other hand, fixing methods that use solvents have problems such as solvent leakage and odors such as steam on the copy paper.
Unfavorable for human health. As a method for improving these drawbacks of the conventional fixing method, a pair of copy sheets carrying an unfixed toner image are pressed together under a predetermined pressure. A method of fixing by passing it between rollers has been proposed. This pressure fixing method has many advantages such as saving electricity and eliminating the risk of fire because there is no need to wait until the device reaches the set temperature.Furthermore, even if the copying speed is increased, the fixing performance decreases. It has the advantage of being able to pass through high-speed copying without any problems. It also has the advantage of not emitting solvent vapors that are harmful to human health. However, in general, this type of pressure fixing has a faster fixing rate than other heat fixing and solvent fixing. There are some disadvantages such as poor sex.

With heat fixing and solvent fixing, the toner completely melts or dissolves, soaking into the paper fibers and then solidifying, so it is relatively firmly fixed to the paper, but with pressure fixing, the toner hardly melts and remains solid. Since the image is fixed by the effect of sticking it into the paper (hereinafter referred to as the "projection effect"), the fixing performance is inferior to that of heat fixing or solvent fixing. This tendency is particularly strong in high-density image areas because the upper toner cannot achieve a tack effect with the paper. In order to improve fixing performance in conventional pressure fixing, improvements have been made mainly from two directions.

One is toner and the other is paper.

Toners basically use paraffin, wax, or rubber-like soft polymers as pressure-sensitive substances, and contain various fillers such as magnetic powder, conductive powder, and pigment particles. The properties of the polymer and the shape and proportion of the filler greatly affect fixing properties. Regarding paper, there are methods of surface treatment, such as applying an adhesion aid to the paper to make it more firmly adhere to the pressure fixing toner, or adding pigment particles to the paper to create a rivet effect. When improving toners, it is generally necessary to consider not only fixing properties, but also development characteristics, transfer characteristics, storage stability, etc., and these characteristics naturally include conflicting properties. There is a limit to the improvement in fixability.

Regarding the improvement of paper, as mentioned above, special treatment is applied to the surface of the paper, which increases the cost of the paper, and the inability to use plain paper is a fatal drawback for copying machines.

Generally, in pressure fixing, an unfixed image is passed between a pair of pressure-engaged metal rolls and fixed by pressure between the rolls.

In this case, the pressure required for fixing is determined primarily by the characteristics of the toner and paper. As the pressure increases, the fixing performance also improves, but the maximum pressure is naturally determined by problems such as changes in paper quality due to pressure, permissible roll load, and increase in device size.
The present invention has been made in view of the above, and its purpose is to provide a pressure fixing device that makes it possible to obtain better fixing performance than the conventional fixing performance even under the same pressure as the conventional fixing conditions. There is a particular thing.

According to microscopic observations by the inventors, the pressure-fixed toner is fixed primarily by the rivet effect with the paper, as described above, and the toner is embedded between the fibers of the paper. To achieve this state, the toner is not simply pressed into the paper by the vertical pressure between the rolls, but is also forced to move the toner slightly in the horizontal direction (hereinafter referred to as shear force). ) was found to be effective in fixing toner on paper. The present invention is configured so that there is a slight difference in the surface speed of both fixing rolls in order to apply a shearing force to the toner surface of the paper.

When paper enters between two rolls whose surface speeds are slightly different, frictional force is generated due to minute slippage between the paper surface and the roll surface, and this force causes toner particles to stick to the paper fibers. It acts as a shearing force that tries to make the material penetrate.

When the friction coefficients of the surfaces of both rolls are equal, a slight slip generally occurs on the surface where the toner is present.

Furthermore, it is clear that when silicone oil is applied as an anti-offset liquid to the toner side roll, minute slips are more likely to occur on the toner side roll. However, in order to ensure that minute slippage occurs on the toner side, the friction coefficient of the surface of the roll opposite to the toner side may be made larger than that of the roll on the toner side. Hereinafter, the present invention will be explained in more detail based on examples and with reference to the drawings.

FIG. 1 shows a side view of a pressure fixing device according to the invention, and FIG. 2 shows both fixing rolls and their drive system in the invention.

In the figure, numerals 3 and 4 are fixing rolls, which are made of carbon steel S5$ and have a diameter of ■50mm as an example of their dimensions.
It has 3 arteries, 50.00 ribs, and a length of 280 sides, and the surface is hard chrome plated. Both rolls are rotatably supported by an upper frame 1 and a lower frame 2, respectively.

In order to obtain uniform pressure over the entire length of the rolls, the axes of both rolls are crossed by 1.2 degrees around the center. The lower frame 2 is fixedly supported by the copying machine body, and the upper frame 1
is mounted at the tip of the lower frame 2 so as to be rotatable up and down about the pivot pin 5 above the lower fixed frame. The load between both fixing rolls is applied by a bolt 6 via a compression spring 7 located at the rear end of the frame, and the load is, for example, 700 k9. The method of driving the rolls is as shown in Fig. 2. The driving force from the motor is applied to the sprocket 13 attached to the end of the lower roll 4.
is transmitted to the chain 14. Inside the sprocket 13, gears for transmitting driving force to the upper roll are attached to the ends of both fixing rolls. Therefore, it can be considered that both rolls are driven in this embodiment. In addition, since the gears are made to have exactly the same number of teeth and outer diameter, the upper and lower rolls of the above dimensions will reach 0 per second.
．． If it rotates six times, the surface speed will differ by 0.6 ribs/sec. This pressure fixing device has a surface speed of 10 m/s.
When the unfixed toner image was pressure-fixed in step c, almost no toner displacement or paper damage caused by the difference in roll surface speed occurred. Furthermore, the fixing performance was clearly improved compared to the fixing performance of conventional devices.

FIG. 3 is another embodiment based on the present invention, and is an enlarged axial sectional view of both fixing rolls.

3 and 4 are fixing rolls made of S5 or both ends diameter 6.
It has 5 lengths and 34 ribs, and the surface is hard chrome plated.

The central paper passing portion 260 of these pair of fixing rolls has a step so that the diameter is slightly different from the diameter at both ends, and the pair of rolls always rotate in contact with each other at both ends.
It is configured to have a gap which is a paper passing portion.

In this case, in order to make the surface speeds of both fixing rolls slightly different in the paper passing part, one roll has a larger roll diameter in the passing part than both ends, and the other roll has a height difference opposite to that of the previous roll. It is provided. The amount of gap in the paper passing portion is set to the thickness when the copy paper on which the toner is applied is compressed with a pressure that can be fixed. According to experiments conducted by the inventors, the gap amount was 0.06 willow, and the load required for it was 800 kg in B Nogi vertical feed. The inventors set the roll diameter of the paper passing portion of fixing rolls 3 and 4 to 65.1, respectively.
4 sides, 64.74 ribs, load between rolls was set to 1300 kg, lower roll 4 was the drive side roll, 3 was the driven side roll, and when pressure fixing was performed with the toner side facing up, the upper roll was lower than the lower roll. It was driven at both ends and rotated in contact with the lower roll without slipping, and there was almost no disturbance of the toner image or damage to the paper due to the difference in roll surface speed in the paper passing section.

Furthermore, the fixing performance was clearly improved compared to the previous device.

Further, in this embodiment, since there is always a gap in the paper passing portion, there is no abnormal compressive deformation of the leading and trailing ends of the paper, and there are few occurrences of scratches due to offset toner or foreign matter.

In addition, since both rolls do not move up and down but remain fixed while rotating in contact with each other, there is no difference in pressure depending on the inside of the paper, and there is also the advantage that there is no noise generated when paper enters or exits. As is clear from Examples 1 and 2 above, the present invention creates a slight difference in the surface speed of a pair of fixing rolls to exert a force that causes the toner particles to sink into the paper fibers. This improves fixing properties.

It goes without saying that the method of creating a slight difference in the surface speed of the pair of fixing rolls is not limited to the configurations shown in Examples 1 and 2, but also includes all other similar configurations.

[Brief explanation of the drawing]

FIG. 1 is a side view of the pressure fixing device according to the present invention, FIG. 2 is a sectional view of the roll of the pressure fixing device in the first embodiment, and FIG. 3 is a sectional view of the roll of the pressure fixing device in the second embodiment. Show each. Explanation of symbols, 1... Upper frame, 2...
...Lower frame, 3...Upper fixing roll, 4
...Lower fixing roll, 5...fulcrum, 6...bolt,
7...Compression spring, 8...Cleaning device, 9
...Upper bearing, 10...Lower bearing, 11...Upper gear, 12...Lower gear. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. A pressure fixing device that fixes a toner image visualized on a copy sheet by passing it between a pair of fixing rolls that are pressed into engagement with each other, and is configured so that the surface speeds of both the fixing rolls have a slight speed difference. This pressure fixing device is characterized by: