JPS6135556B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field) The present invention relates to a fixing device used in electrostatic copying machines, electrostatic printing machines, and the like.

(Technology Related to the Present Invention) Conventionally, in a fixing device of a copying machine or the like, a method has been used to permanently fix a toner image electrostatically adhered to the surface of a support such as paper by heating and melting the toner image onto the support. Generally adopted.

However, such a heat fixing method requires a large amount of power for the heat source, and this heat fixing consumes about 70 to 80% of the total power consumed by the entire copying machine. In addition, it takes time for the fixing device to reach the temperature required to fix the toner image, and not only does the copying machine fail to copy immediately even when the power switch is turned on, but the heat emitted from the fixing device causes the copying machine to The whole body is heated, which changes the characteristics of the photoreceptor or developer, which has the disadvantage of reducing their performance and life. Moreover, if the support jams in the fixing device, there is a problem that the support may catch fire.

Therefore, a pressure fixing method that does not have the above-mentioned drawbacks has recently been adopted. In this pressure fixing method, a support to which pressure fixing toner is attached is passed between a pair of fixing rollers that are pressed together under high pressure, thereby fixing a toner image under pressure.

Figure 1 shows a conventional pressure fixing device.
The fixing roller 1 in contact with the toner image surface of the carrier P is a metal roller, and the fixing roller 2 in contact with the back surface of the support P
The surface of the fixing roller 1 is made of an elastic material, or the surface of the fixing roller 1 is made of an elastic material.
The rollers 1 and 2 are arranged so that their central axes intersect with each other, and each roller is made of a metal roller, and both rollers 1 and 2 are pressed together under high pressure by a pressure mechanism 3.

However, in the former fixing device consisting of a metal roller and an elastic roller, the pressure applied is limited by the material of the elastic roller, so it is not possible to apply a large pressure to the fixing roller, and the elastic roller does not hold the toner. It has the disadvantage of being easily scratched by carriers, etc.

On the other hand, the latter fixing device consisting of two metal rollers can apply high pressure, but it uniformly applies a load (pressure) on the surface of the support that exceeds the critical pressure necessary to sufficiently fix the toner image. for,
The diameter of the fixing roller must be increased. Increasing the diameter of the fixing roller increases the size and weight of the apparatus, and does not have a very favorable effect on fixing performance. Furthermore, since both rollers intersect, if the diameters of the rollers are different from each other, wrinkles will occur on the support, and the wrinkles will be particularly noticeable in the case of a wide support.

According to experiments conducted by the present inventor, it has been found that the maximum pressure P ₀ per unit area is a greater factor in the fixing performance due to pressure than the total pressure W ₀ acting on the nip portion of the fixing roller. However, in the conventional fixing device, when the diameter _R1 of the fixing rollers 1 and 2 increases as shown in FIG. Since the nip width (angle α) becomes wider as the roller diameter increases, the pressure distribution at the nip portion becomes wider. Therefore, for the pressing force W ₀ applied to the roller, the maximum pressure P ₀ acting on a unit area is not larger than the pressing force W ₀ , and the pressing force
Increasing W ₀ does not help much in improving fixing properties.

In FIG. 3, numeral 4 indicates a fixing roller, which is made of a metal roller such as iron.
Reference numerals 5 and 6 denote pressure rollers that come into contact with the outer peripheral surface of the fixing roller 4, and are made of metal rollers such as iron, each having a diameter larger than the diameter of the fixing roller 4.

Note that the pressure rollers 5 and 6 may have the same diameter or different diameters, but if the pressure rollers are made of the same material and have the same structure, they may have different diameters.

As shown in FIG. 5, the center axes a, b, and c of the fixing roller 4 and pressure rollers 5, 6 in any cross section are always in contact with the fixing roller 4 and the lower pressure roller 6, as shown in FIG. They are arranged so as not to be parallel to the fixing roller 4 so as to be located on a straight line J, J ₂ , J ₃ passing through Q.

Therefore, the center axis of each roller 4, 5, 6 is on the straight line J ₁ at the front side (one end of the roller) toward the drawing, on the straight line J 2 at the center of the roller, and on the straight line J ₂ at the center of the roller. On the side (other end of the roller) straight line J ₃
exists above.

FIG. 4 shows the state of contact between the fixing roller 4 and the lower pressure roller 6. Both rollers intersect with each other, and the contact portion Q of both rollers forms a straight line H in the axial direction of the rollers.

Note that in the above example, the fixing roller through which the support passes is brought into contact with the lower pressure roller, but in this example, both rollers are separated slightly and the fixing roller and lower pressure roller are brought into contact through the support. The invention includes.

Therefore, the contact portion between the fixing roller and the pressure roller through which the support passes includes a case where the two contact directly and a case where the two contact indirectly through the support.

As shown in FIGS. 6 and 7, the upper pressure roller 5 is rotatably provided on the upper support plate 7 via a bearing 5a, and the lower pressure roller 6 is attached to the lower support plate 7 via a bearing 6a. It is rotatably provided at 8. The fixing roller 4 is rotatably provided on the lower support plate 8 via a bearing 4a, and when in a pressurized state as described above, each roller 4, 5,
6 are arranged so that their central axes are always located on a straight line J. By aligning the central axes of each roller, a uniformly distributed load can be applied to the support S, and when the co-fixing roller 4 is held between the pressure rollers 5 and 6, the fixing roller will not pop out. Alternatively, it is possible to prevent an accident in which the fixing roller is bent due to the impact when the support body S is inserted or ejected.

Further, the fixing roller 4 is supported by the lower support plate 8 so as to be able to move slightly along the straight line J in order to apply a uniformly distributed load on the support S when pressurizing. Reference numeral 9 indicates an opening provided in the lower support plate 8, and the bearing 4a is placed in this opening 9.
Move slightly in the direction of straight line J.

A support S such as paper carrying a toner image is fed between the fixing roller 4 and the pressure roller 6 so that the toner image surface is in contact with the fixing roller.

A drive gear 10 coupled to a drive source is provided at one end of the lower pressure roller 6.
The rollers 4 and 5 are rotated as a result of the drive. Note that a drive gear may be provided at the end of the fixing roller 4.

The support plates 7 and 8 are supported by a common shaft 12 so as to be openable and closable, and a bolt 13 is fitted into a hole at the end opposite to the shaft, and a spring 14 is fitted into the bolt 13.

The bolt 13 and the spring 14 constitute a pressurizing mechanism,
As shown in FIG. 7, when the support plates 7, 8 are pressed closed by the spring 14 via the bolt 13, this pressing force is transmitted to the rollers 4, 5, 6, and the rollers are brought into pressure contact. This makes it possible to fix the toner image on the support.

Next, the influence on the fixability of a toner image when the above-described fixing device is used will be explained.

As mentioned above, the major factor that correlates with the fixability of toner images is the maximum pressure per unit area generated at the nip portion, rather than the total pressure applied to the roller. Therefore, the nip width and the maximum pressure at the nip portion for both the conventional example shown in FIG. 1 and the embodiment of the present invention shown in FIG.
The result is as shown in FIG. Figure 8 is the first
9 shows the pressurized state of the conventional fixing device shown in the figure, and FIG. 9 shows the pressurized state of the fixing device shown in FIG. 3.

The calculation formula is Pmax=0.6√ (however, W
is the linear pressure, E is the longitudinal elastic modulus of the support, and R is the radius of the fixing roller).

In both fixing devices, the same copy paper was used as the toner image support and the copy paper was transported at the same speed. In Fig. 8, the radius of fixing rollers 1 and 2 is
R ₁ is 30 mm each, pressure W is 40 Kg/cm at ₁ linear pressure, thickness of copy paper S before pressure l ₁ is 80μ, thickness when pressure is applied l ₂
When 30μ, the nip width L1 (the width of the deformed portion _of the copy paper sandwiched between the two rollers) was 2.2 mm, and the maximum pressure _P1 was 220 kg/cm.

On the other hand, in FIG. 9, the radius R ₂ of the rigid fixing roller 4 is 10 mm, the upper pressure roller 5 is a hollow rigid roller, the lower pressure roller 6 is a solid rigid roller, and both pressure rollers 5, 6 are radius R ₃ of respectively
20mm, the pressure force _W2 is 20Kg/cm in linear pressure, and the thickness _l3 of copy paper S when pressed is 30μ, then the nip width _L2 is
1.3 mm, and the maximum pressure P ₂ was 270 Kg/cm.

Therefore, as is clear from the above experiments, with the fixing device, a large load can be applied to the toner image support with a smaller pressing force than in the past, and good fixing performance can be obtained.

Further, in the conventional fixing device, the thickness of copy paper immediately after fixing is reduced to 60μ, but in the above fixing device, the thickness of copy paper immediately after fixing is 65μ. This is because the nip width of the conventional type is 2.2 mm, while the nip width of the present invention is 1.3 mm, which is about 40% narrower than the conventional type. This is because when the paper conveyance speed is the same as the conventional one, the pressurizing time of the copy paper is shortened, and the elasticity of the fibers of the copy paper is lost, or the proportion of fibers that stick together is reduced.

Furthermore, when the toner support passes between the rollers that intersect with each other, no wrinkles occur on the copy paper, the conveyance condition is stable, and constant fixing can be performed at all times.

(Object of the present invention) The object of the present invention is to form a gap to reduce the impact when the support enters between the rollers and is ejected;
It is an object of the present invention to provide a fixing device in which wear of the roller flange portion for forming the gap is prevented.

(Embodiment of the present invention) FIGS. 10 and 13 show an embodiment of the present invention, and parts having the same configuration and function as those of the previous embodiment are designated by the same reference numerals.

In FIG. 10, flange portions 106 having a larger diameter than the center portion are provided at both ends of the lower pressure roller 106.
₁ , 106 _{and 2} are provided between the fixing roller 4 through which the support S passes and the pressure roller 106, and the thickness is smaller than the elastic deformation thickness of the support S during fixing and is larger than the particle size of developer such as toner. A large gap d is formed.

Note that the rollers 4, 5, and 106 are arranged so that a uniformly distributed load is applied between the rollers 4, 106, and wrinkles do not occur on the support, as in the previous embodiment. Therefore, the contact portion between the fixing roller 4 and the lower pressure roller 106 that are in contact via the support S (the support is
(the part that indirectly contacts the roller) is a straight line in the axial direction of the roller.

In FIG. 11, the bearing 5 of the upper pressure roller 5
a' and the bearing 6a' of the lower pressure roller 6 are brought into contact,
The fixing roller 4 is supported by a bearing 4a', and the gap d is formed between the fixing roller 4 and the lower pressure roller 6.

In FIG. 12, a spacer 50 is provided between the bearing 5a' and the bearing 6a' to form the gap d.

As described above, the fixing roller 4 and the lower pressure roller 1
By providing the gap d between the rollers 06 and 6, it is possible to reduce the impact between the rollers when the support body S enters between the rollers and when it is discharged.

FIG. 13 relates to the main part of the present invention, and the first
This is a coating device that supplies anti-wear lubricant to the flange _portion of the lower pressure roller ₁₀₆ shown in FIG. The lubricant in the container 112 is applied to the application roller 110,
It is applied to the flange portion through the felt patch 111. Note that a toner release agent such as silicone oil may also be used as the lubricant.

113 is a blade that prevents the lubricant applied to the flange portion from entering the small diameter portion of the pressure roller 106, and 114 is a drive source that drives the application roller. Note that at least one U-shaped or V-shaped groove may be provided between the small diameter portion of the pressure roller 106 and the flange portion.

By applying lubricant to the flange,
By applying a high load to this part, it is prevented from wearing out faster than other parts.

As mentioned above, since the contact portions of the fixing roller and the pressure roller that intersect with each other are formed in a straight line,
The toner support passing through this contact portion is not wrinkled, and the toner support can be transported in a stable state at all times. This is particularly effective in preventing wrinkles when a wide toner support is used.

In addition, since the center axes of each roller in a given cross section are located in a straight line, it is possible to apply a uniformly distributed load to the toner support and a relatively high load. The diameter of the rollers can be made smaller than conventional rollers, and the total pressing force applied to each roller can also be reduced, so the pressing mechanism can be made smaller, making the device smaller and the weight of the device lighter. It has excellent practical effects, such as being about 40% lighter than conventional ones.

Furthermore, the copy paper after fixing does not become glossy or translucent as in the case of conventional pressure fixing, but has elasticity and a soft surface state that makes the image easy to see.

(Summary and Effects of the Present Invention) The present invention provides a fixing device that fixes a toner image on a support by passing a toner image support between a fixing roller and a pressure roller. The flange portion has a diameter larger than that of the flange portion, and the flange portion forms a gap between the fixing roller and the pressure roller for passing the support, and a lubricant for preventing wear is supplied to the flange portion. Since the fixing device is characterized in that the support body is conveyed between the rollers with a small impact, it is possible to prevent wear of the flange portion.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a conventional pressure fixing device, FIG. 2 is a diagram explaining the pressurized state of the device shown in FIG. 1, and FIG. 3 is a configuration diagram showing an embodiment of the pressure fixing device according to the configuration of the present invention. Figure 4 is a diagram showing the state of contact between the fixing roller and the lower pressure roller, Figure 5 is a sectional view taken along a plane that intersects the roller axis, and Figure 6 is a cross-sectional view taken along the roller axis. 7 is a side view, FIG. 8 is a diagram showing the pressurized state of the device shown in FIG. 1, FIG. 9 is a diagram showing the pressurized state of the device shown in FIG. 3, and FIG.
11 and 13 are explanatory views of main parts related to embodiments of the present invention, and FIGS. 11 and 12 are explanatory views of the structure of forming a gap other than the gap d of the present invention. 4... Fixing roller, 5, 6, 106... Pressure roller, 13... Bolt, 14... Spring, 106
₁ , 106 ₂ ... flange portion, 111 ... felt pad, 110 ... application roller, 113 ... blade. 〓〓〓〓〓

Claims (1)

[Scope of Claims] 1. In a fixing device that fixes a toner image on a support by passing a toner image support between a fixing roller and a pressure roller, both ends of the pressure roller have a diameter smaller than that of the center. It has a large flange portion, the flange portion forms a gap between the fixing roller and the pressure roller for paper passing through the support, and a lubricant for wear prevention is supplied to the flange portion. Fixing device. 2. The fixing device according to claim 1, wherein the wear-preventing lubricant is a toner release agent. 3. The gap is smaller than the elastic deformation thickness of the support during fixing and larger than the particle size of the developer of the toner image.
Fixing device as described in section. 4. The fixing device according to claim 1, wherein the fixing roller and the pressure roller intersect with each other so that their central axes are not parallel to each other.