JPS6237785B2 - - Google Patents

Description

[Detailed Description of the Invention] A. Purpose of the Invention [Field of Industrial Application] The present invention provides a method for performing each process of charging, exposing, developing, transferring, etc. between a pair of fixing rollers that rotate under pressure by applying a predetermined pressure. The present invention relates to a pressure fixing device in an electronic copying machine that fixes a toner image under pressure through an image support material such as copy paper on which a toner image is formed.

[Conventional technology]

Conventionally, in this type of pressure fixing device, a pair of rigid metal rollers is used as the fixing roller, or one of the fixing rollers is a metal roller and the other is an elastic roller.

In the former case, which uses a pair of metal rollers, the circumferential width (nip width) of the rollers in contact with the copy paper is small, so the pressure applied to the copy paper during fixing is locally increased to improve fixing performance. You can get a good copy of it. However, it is very difficult to bring a pair of rigid metal rollers into contact with uniform pressure over their entire length. As a means to improve this drawback, it is known to bring a pair of rollers into contact with each other at a crossing angle of about 0.5° to 1.5°. In order to make the fixing device smaller and lighter, it is desirable to reduce the diameter of the rollers, but this angle of intersection must be increased as the diameter of the rollers becomes smaller. If the crossing angle becomes large, the conveyance of the copy paper becomes unstable when it enters, and the copy paper may wrinkle during fixing, or the paper may tear if it is made of thick paper. On the other hand, since the pressing force is large, even a thin copy paper of about 70 to 80 μm receives a very large impact when entering and ejecting the copy paper. In order to reduce this impact, a method has been proposed in which the leading edge of the paper enters the contact line of the fixing roller obliquely, but this may impair the conveyance of the paper. Further, since the fixing roller is in contact over the entire surface even when the roller is not in use, the roller surface may be plastically deformed, which may cause fixing failure.

The latter pressure fixing device using a metal roller and an elastic roller is superior to the former in that it can generate pressing force uniformly and in that it can reduce the impact when paper enters.

[Problems to be Solved by the Invention] However, in a pressure fixing device using a metal roller and an elastic roller, in which pressure is constantly applied between both rollers, even when not fixing, Since a sufficient pressing force continues to act between both rollers, the load tends to cause the elastic roller to undergo plastic deformation over time, which shortens the life of the device.

The present invention is also a pressure fixing device using a metal roller and an elastic roller, and is of the type that constantly applies pressure between the two rollers, but it reduces the pressure load on the elastic roller when not fixing. The object of the present invention is to provide an elastic roller that is devised to prevent plastic deformation of the elastic roller.

B. Structure of the Invention [Means for Solving the Problems] The present invention provides for passing an image support material having a toner image between first and second rollers that rotate under pressure, so that the toner image is transferred onto the support material. In a pressure fusing device, the first roller is rigid and the second roller cooperates with the first rigid roller to fix the toner image on the image support introduced between the rollers. The elastic roller portion to be fixed comes into contact with both ends of the first rigid roller on both sides to limit the pressure between the first rigid roller and the elastic roller portion of the second roller when not fixing. The gist of the present invention is a pressure fixing device characterized by having a roller-like rigid body portion.

[Effect]

During non-fixing, that is, when no image support material is introduced between the rollers, the second roller, including its elastic roller portion and roller-like rigid portions at both ends, is similar to the first rigid roller. Although it is in pressure contact with
The roller-like rigid body portions at both ends are in contact with and received by both ends of a first roller, which is also a rigid body, and serve as spacer rollers, and the elastic roller portion is in contact with the first rigid roller. The pressure received at the point is low and limited.

On the other hand, during fixing, that is, during the process in which the image supporting material is introduced between the rollers and passing through, the image supporting material passes between the first rigid roller and the elastic roller portion of the second roller that is in contact with it. By being bitten and passing through, the elastic roller part causes compressive deformation against elasticity at the contact part with the image supporting material due to the thickness of the image supporting material passing through, and the reaction force of the compressive deformation increases the first rigidity. A sufficient pressure fixing force greater than that in the non-fixing case is obtained between the body roller and the elastic roller portion of the second roller, and the toner image is properly pressure fixed.

Thus, during fixing, sufficient pressure fixing force is obtained between the first rigid roller and the elastic roller portion of the second roller, and when non-fixing, the elastic roller portion of the second roller is lower than during fixing. A limited pressure receiving state is maintained, and as a result, plastic deformation of the elastic roller portion over time due to the pressure receiving load during non-fixing and shortening of the device life due to this is prevented.

〔Example〕

Embodiments will be described below with reference to figures. In FIG. 1, 4 is an upper roller as a first roller made of a rigid metal, 5 is an elastic member in the center that contributes to fixing, and short roller-shaped flanges 51 at both ends thereof, 51 is a lower roller as a second roller made of a rigid metal; 6 and 7 are upper and lower supports for a pair of left and right bearing shafts at both ends of the upper roller 4 and lower roller 5, respectively; , 8 is a shaft connecting the upper and lower supports 6 and 7 so as to be openable and closable, 9 is a bottom plate attached between the left and right lower supports 7, 7, and 10 is the opposite side of the opening and closing shaft 8 of the left and right upper supports 6 Lower support 7 with a bolt loosely passed through a hole in the free end of
or insert it into the hole and screw the nut onto the lower end. 11 is the head of the bolt 10 and the upper support 6
A compression spring provided between the rollers 4 and 5 serves as a pressing mechanism between the rollers 4 and 5. A gear 12 is attached to the shaft 41 of the upper roller 4, and driving force is transmitted from a drive source such as a motor (not shown in the figure) to drive the upper roller 4. The lower roller 5 follows the upper roller 4, and the rollers 4, The copy paper sent during the interval 5 is fixed and carried out in the direction of arrow A.

FIG. 2 shows a non-fixing state, in which the length l1 and diameter D1 of the elastic roller portion of the lower roller 5 that is made of resin and which performs the fixing action, and the length l2 and diameter D2 and D1 of the metal flange portion 51. >D2. In addition, the pressing loads applied to the left and right axial pressure parts of the upper and lower rollers 4 and 5 by the pressing mechanisms 10 and 11 are W/2, respectively, and the load per unit length of the l1 portion due to the pressing loads w
Assuming that the load W1 received by parts 1 and l2 is W1, the load W of the entire roller is W=w1l1+2W1, and the contact part of the lower elastic roller part l1 with the upper roller 4 is compressed and δ=1/2(D1-D2 ), and the metal flange portion 51 comes into contact with the upper metal roller 4 to act as a pressing force limiting stopper. However, the elastic roller is made of a material that does not undergo plastic deformation under this amount of deformation δ and load w1.

When a copy paper P with a width l enters between the upper and lower rollers 4 and 5 in this state as shown in FIG. Assuming the load W2, W≒
w2l+2W2. Copy paper is generally about 80μ thick,
It shrinks to about 30-50μ during pressure fixing.

Therefore, the amount of deformation of the elastic roller (δ
+40 μ), the material of the elastic roller 5 and its diameter D are selected so as to generate the necessary pressing force w2 to fix the pressure.
1. The diameter D2 of the flange portion 51 is selected.

In FIG. 4, the elastic roller portion l1 of the lower roller and the flange portions 51, 51 have the same diameter, and the flange portion 5
The portion 42 of the upper metal roller 4 that is in contact with each other is a stepped roller having the relationship D1>D2, and functions in the same manner as in the previous example.

C. Effects of the Invention As described above, according to the present invention, sufficient pressure fixing force can be obtained between the first rigid roller 4 and the elastic roller portion l1 of the second roller 5 during fixing. On the other hand, during non-fixing, the elastic roller portion l1 of the second roller is kept in a limited pressure receiving state lower than during fixing,
As a result, plastic deformation over time due to the pressure load of the elastic roller portion l1 during non-fixing is prevented, and shortening of the device life due to this is prevented, and the intended purpose is well achieved.

There are also the following effects.

a Since the first roller 4 in contact with the image surface is made of a rigid body, it cannot be scratched by toner carrier.

b When the second roller 5 is not fixed, the pressing force between the rollers 4 and 5 is mainly supported by the roller-shaped rigid body parts 51, 51 near the bearings at both ends, so that the deflection that occurs in the elastic roller part l1 is This makes it possible to minimize the amount of noise and reduce the driving force.
Therefore, it is possible to use a core metal of the second roller 5 that is thinner than the conventional core metal, and a lightweight pressure fixing device can be manufactured.

c Roller-shaped rigid bodies 5 at both ends of the second roller 5
1 and 51 rotate with the rotation of the second roller 5, and therefore, their rigid bodies always change the contact position with the end circumferential surface of the first roller 4, which is the opposing roller, to prevent uneven wear. You can extend your lifespan without this problem.

d a first roller 4 which is basically a rigid body;
Since the roller pair is a combination of the second roller 5, which is an elastic body, it is possible to generate a uniform pressing force over the entire surface of the image support material, and to reduce the impact when the image support material enters and is ejected between the roller pair. This can reduce the appearance of waves and wrinkles.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an embodiment of the pressure fixing device of the present invention, FIG. 2 is an explanatory diagram of the roller at rest, and FIG.
The figure is an explanatory diagram of the fixing operation, and FIG. 4 is another embodiment. 4 is a fixing roller made of a rigid body, 5 is a pressure roller made of an elastic body, 6 and 7 are roller supports, 8 is an opening/closing shaft,
10 and 11 are pressing mechanisms, δ is the amount of deformation of the elastic roller, and 51 and 51 are metal flanges.

Claims (1)

[Scope of Claims] 1. In a pressure fixing device that fixes the toner image on the support material by passing an image support material having a toner image between first and second rollers rotating in pressure contact, the first roller is a rigid body, and the second roller has an elastic roller portion introduced between it and the first rigid roller that fixes the toner image on the image support material in cooperation with the roller; The first rigid roller is in contact with both ends of the first rigid roller during non-fixing.
1. A pressure fixing device comprising a rigid roller and a rigid roller portion that limits pressure between the rigid roller and the elastic roller portion of the second roller.