JPS5862678A - Fixing device - Google Patents

Abstract

PURPOSE:To apply a uniform and sufficient pressure accurately to a toner image at the fixing time, by providing a rotary material having an elastic material which is discontinuous in the direction orthogonal to the rotation direction and deforming the elastic material in a region, through which a supporting material passes, at least when the supporting material passes through the rotary material. CONSTITUTION:A rigid metallic roller 8 is brought into contact with a toner image on a paper S and has the surface coated with an offset preventing means and is brought into contact with an elastic roller 7, and the toner image is fixed to the paper s with a pressure by these rollers 7 and 8. Elastic parts 61-75 which are separated from one another in the direction of the axis of the roller 7 and are disposed in contact are provided on the surface layer of the elastic roller 7 so that their separation is filled up to make the surface uniform when rollers 7 and 8 are pressed to each other, and elastic parts 71 and 72 are provided in end parts, and the width of elastic parts 72-74 between them correspond to a maximum paper size (B4 size), and other elastic parts correspond to the B5 size, the A4 size, etc. respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fixing device for an image forming apparatus such as an electrostatic copying machine or an electrostatic inking machine, which forms an unfixed image on an image supporting material and conveys the supporting material for fixing. It is something.

Conventionally, the fixing devices used in photocopying machines have been heat fixing devices that heat and melt the toner image attached to the surface of a toner image support material such as paper and permanently fix it on the support material, and other devices that do not require a heat source. Therefore, pressure fixing devices, which are effective in saving power and eliminating wait time, are mainly put into practical use.

In these devices, a device that fixes the toner image by passing a support material supporting the toner image between rotating bodies, particularly rollers, is often used, and these rollers are used in pressure contact with each other at a predetermined pressure. Therefore, the pressure distribution when the supporting material supporting the toner image passes through the rollers has a great influence on the fixing performance, and is particularly important for the fixing performance of the pressure fixing device.

Conventionally, in an apparatus employing such a pressure fixing method, the central axis I of a pair of rollers 1.2 that pinch and press the toner image bearing material is
A and 2A are arranged approximately parallel to the common tangential plane of rollers 1 and 2, and are oriented so that they have a torsional relationship (having a twist angle of -) with each other (see Fig. 1).
, and add the same load to the ends of both rollers 1.2.
Figure 2 0 (vertical axis is roller 1,
2, the horizontal axis is the length of the roller)
. Therefore, in order for the width direction center line of the toner image support material of any width to pass through the center of the lower longitudinal direction, rollers l and 2 are used.
This is useful when conveying with 4C clamp pressure. However, there are various inconsistencies in transporting toner image supporting materials of any width from the paper feed cassette to the fixing device as described above. For example, in a transfer-type copying machine, there is a rule that the transfer paper should not be brought into contact with the photoreceptor so that its widthwise center coincides with the widthwise center of the photoreceptor. When conveyed in this manner, it is easy to peel off the transfer paper from the photoreceptor of the transfer machine.

Furthermore, with the above device, each time you change the dimensions of the transfer paper, that is, change the copy size, you have to realign the widthwise center of the document with the widthwise center of the document table, which requires careful attention. However, a problem often arises in which the original is placed in the wrong position and only a portion of the original can be copied.

As a solution to the drawbacks of such central reference copiers,
So-called one-sided reference copying machines are already known. In this one-sided reference copying machine, for any copy size, the document only needs to be placed on the document table with two sides sandwiching one corner aligned with the common reference.

Further, even if the size of the transfer paper varies, the side edges parallel to the conveyance surface of the paper are always conveyed with a constant common line as a reference.

Therefore, the position of one side of the paper feed cassette in which a large number of transfer paper is loaded (the transfer paper is stored at a distance of Km from one side of the paper feed cassette) is the same for all sizes, making handling easy and the structure simple. It is. In addition, when transferring the ll1i image, one side edge of the transfer paper is always urged toward the photoreceptor on a constant common line regardless of the transfer size, making it easy to separate the paper from the photoreceptor. . This is because if a claw, belt, roller, etc. is placed at the side edge position of the photoreceptor through which one end passes, the transfer paper can be easily peeled off from the photoreceptor, and such peeling can be prevented. The means are known.

In this way, although the nine-sided standard conveyance system has various advantages, when using a conventional pressure fixing device with an evenly distributed load as shown in Figures 2-a and 2-b, When a toner image supporting material with a small width is fixed, toner image fixation on the conveyance reference line side becomes poor, and an overload is applied to the area on the opposite side of the paper from the reference line side, causing the paper surface to become glossy. ,
The problem arises that the paper becomes thinner and becomes transparent.

As shown in FIG. 3-a, if the loads applied to the left and right ends of the roller l are equal, the toner image supporting material
For example, the side edge P' on the opposite side from the conveyance reference side side edge P of the paper 8.
This is because the area near the area supports the load between the rollers where there is no paper on the right side. First, the roller l rotates slightly clockwise about this side edge P as a fulcrum, and the pressure applied to the paper on the side edge P side is reduced. This kind of inconvenience is
In particular, when rollers 1 and 2, or one of them, is a highly rigid roller such as a steel roller surface coated with hard chrome plating, and has only a small amount of elastic deformation. is especially serious.

The pressure distribution of the above-mentioned No. 3 m-a is shown in Fig. 13-b. Po is the applied pressure necessary to press and fix the toner image. As described above, due to the difference in inclination of the rollers 1.2, the paper S1. Since the 111 edge P' of 111 serves as a fulcrum, a pressure considerably larger than the predetermined applied pressure Po is applied here as a concentrated stress.

On the other hand, in the conveyance standard 1NJA edge P of Gi S, roller 1
．． A pressure smaller than the applied pressure Po cannot be applied by applying a moment in the direction in which the parts 2 are separated. In this way, at the side edges P, P' and the roller length between them, either the necessary pressure is not applied, or excessive pressure is applied, resulting in a relatively linear pressure distribution state.
Uneven pressure is applied throughout.

Therefore, in the pressure fixing device using a pair of rigid rollers, the fixing performance changes each time the paper feeding width of the toner support material changes, and overall the applied pressure is wasted, resulting in a device with poor fixing performance. .

FIG. 4-a is an explanatory diagram of a fixing device having an elastic roller 3 having a continuous elastic surface layer instead of the pair of rigid rollers. As the paper S enters, the roller 3 moves to the side edge P on the conveyance reference side.
Elastic deformation occurs between and the side edge P' of the paper S and the periphery thereof. However, as mentioned above, even in this case,
Concentrated pressure is generated at a portion of the paper S corresponding to the side edge P'. Since this concentrated stress is a continuous elastic body, it is smaller than that in the case of a rigid body, but it results in a pressure distribution as shown in FIG. 4-b.

That is, around the side edge P' of the paper to which concentrated pressure is applied, excessive pressure exceeding the predetermined pressure 9 that can be fixed is applied,
@Only a pressure equal to or less than a predetermined pressure a is applied around the edge P. Therefore, non-uniform pressure is applied to the toner image on the paper S, resulting in an increased number of cracks due to poor fixing. Also, to compensate for this, if you try to improve fixing by increasing the pressure,
The stress applied to the elastic body occurs as an unrestricted continuous stress over the entire length of the roller.In any case, the elastic body of the roller has an uneven stress distribution that connects excessive stress and insufficient stress. This has the drawback of causing damage to the elastic body and unduly reducing the durability of the roller 3.

An object of the present invention is to provide a device for efficiently fixing the film to a support material.

Hereinafter, the present invention will be further explained in detail with reference to FIGS. 5 to 7.

Figures 5 and 6 are explanatory views of one embodiment of the present invention. This figure shows a perspective view of this embodiment and the size of the paper S used (
B5. The relationship between position pA and A4, 84) is also shown. 8d
A metal roller of varying rigidity is provided on the side of the paper that comes into contact with the toner image. Although not shown, the surface of the roller 8 is provided with an anti-offset agent coating device or anti-offset processing. Reference numeral 7 denotes an elastic roller that is in pressure contact with the roller 8, which pinches the paper S with the roller 8 and feeds it to fix the toner image on the paper 8 under pressure.

The surface layer of the elastic bead 27 includes elastic parts (7s = 71
, 7m-t 74-76) are provided so that the separation is filled in and made uniform when the rollers 7.8 are pressed against each other. And elastic part 7. ,7. are provided at both end regions of the roller 7, respectively, and an elastic portion 7t* 7je 7 is provided between them.
The width K is equal to or slightly larger than the feed width of the largest size paper (B4 size paper in this embodiment).

This elastic part 7. and an elastic portion 7 adjacent thereto. The boundary part P between the two is a reference for one-sided conveyance. This boundary part P, to B
7. Elastic part with a width corresponding to the 5t size paper feed width. When adjacent, the elastic part - which is the width to be added to the elastic part 7.0 width so as to correspond to the A4 size paper feed width, is further increased, and the elastic part 7.0 is added so as to fill the remaining width. 4, . 4. are side plates that are rotatably provided with one end thereof as a fulcrum O, and rotatably support the metal roller 8 and the elastic roller 7, respectively. A pressure spring 9 and a pressure adjustment screw 5 are provided at the other end of the fulcrum 0 so that a predetermined pressure is applied to the toner image on the paper 8 between the rollers when the paper 8 is conveyed. 9 is a rotating shaft of a metal roller, and a motor (
gear 9 that transmits the driving force from (not shown) to the roller 7°8.
is installed.

Next, referring to FIG. 6, the fixing operation will be explained.

FIG. M6 shows a schematic cross-sectional view of this embodiment and a pressure distribution curve in the axial direction of the roller. First, fixing of A4 size paper will be explained.

The toner image carried silently on the paper S by electrophotography or the like is conveyed together with the paper S moving along the side edge P on the conveyance reference side to a fixing station.

Here, the paper S is held between the rollers 7.8, but since it is A4 size, the elastic roller 7.8 has a width corresponding to the feed width of the elastic row 27. ,7. Only the paper S is elastically deformed by the thickness of the paper S and the thickness of the toner image. In the diagram, t is loaf 7
．． The elastic part 7I, 7□7.0 thickness due to pressure contact of the elastic body 7I, 7□7.0, 1° is the natural thickness (t≦chi), but due to this elastic deformation, the elastic body 7. ．． The thickness of 74 is smaller than the thickness t.

In this way, the elastic portion 7. ．． 'I, that only K performs the fixing action.
Therefore, mutually discontinuous elastic bodies 7. .

7. 7. does not participate in the fixing action of fixing the toner image onto the paper S, and is not subjected to unnecessary deformation.

Referring to the graph showing the pressure distribution of the elastic row 27 in the roller axial direction, the elastic body 78174 uniformly applies pressure equal to or higher than the standard to the toner image based on the applied pressure P6 necessary for fixing, and the elastic body 71 *7! At -71, it is clear that a pressure is being applied to maintain a predetermined pressure contact state. Therefore, the toner image of A4 size 8 is the elastic body 7. .

74 requires uniform pressure! To be given a break, Gizumi S
be well established. At this time, the discontinuous portions between the elastic bodies 7174 are filled with each other by the elastic deformation of the elastic bodies 71e740, making the discontinuous elastic bodies 7, . 74 is paper 5 (A4
It is used as an integrated elastic body for the size).

Further, since such a discontinuous portion of the elastic body is provided, stress on the elastic body is no longer excessive at the end of the toner support, which is the case in the conventional case, and the elastic layer is not damaged.

On the other hand, when fixing a toner image support having a large width, the discontinuous portions of the elastic body were filled by deformation of the elastic body, so that the fixing failure corresponding to the discontinuous portions did not occur.

Each of the above elastic bodies 71171*7. , 74e and 71 are preferably pressed against each other to form a uniform roller surface, but since it is more preferable that they exhibit the same elastic modulus during the fixing action, it is preferable that their constituent materials be the same. is preferred.

As the core material of the roller rough having the above-mentioned elastic body, gold oyster or ceramic mix is preferable.

Furthermore, using the apparatus shown in Figure 5.6 above, B5 size and A
When a toner image was fixed using three sizes (matching the feed width of A4 size), such as B4 size, the elastic body corresponding to each size was elastically deformed and good and uniform fixation was achieved. Applicable examples will be further explained using an example of this device.

For the metal roller 8 described in F, a steel roller plated with chrome is used, and an elastic body is applied to the elastic roller rough and the steel roller so that the discontinuous portion is 0°11 or less as shown in Fig. 5.6. A material coated with ultra-high molecular weight polyethylene film with a thickness of 0.5 was used.

At this time, when a total pressure of 8~/mm per unit length and width of the roller was applied to the fixing device, it was found that the elastic body corresponding to the support material of each size used was independent of the elastic body that was not used. Good and uniform fixing properties were obtained for any size of support material.

゛Another example is the relatively high pressure 15-1. c.
In the case of -, as in the previous He example, the discontinuous portion is filled by elastic deformation due to contact between the normal elastic body and the metal roller 8, but the durability may be slightly reduced due to rounding, which is constantly subjected to high pressure. Therefore, in this example, 7. The parts have been treated with measures to improve durability. Examples of this means include means for providing a non-fixing time interval between the rollers 7.8, means for constantly forming a minute gap between the rollers 7.8, and surface hardening treatment. ,7. Instead of the elastic bodies 71, 7. A roller portion made of steel, for example, is provided with a compressive modulus much larger than that of the roller portion. As a result, when the roller is stationary, the steel roller portion acts as a stopper to prevent deformation at the nip portion of the elastic bodies 7s and 74.7s, thereby eliminating the above-mentioned inconvenience.

In addition to the above-mentioned ultra-high molecular weight polyethylene, the n-type materials conveniently used in the present invention include toner image supporting material □ Thickness of the toner image supporting material due to the pressure applied when passing through tyrene, fluororesin, polyamide resin, urethane elastomer , vinylidene chloride resin, polyester, polycarbonate, polypropylene, butane elastomer, epoxy resin, and other resin-based elastomers, and as rubber-based materials, fluororubber, natural rubber, chloroprene rubber, isoprene rubber, fluororubber, etc. are preferable.

Further, it is more preferable to use a mixture of the above-mentioned materials with glass fiber, gold, or the like.

Further, in this embodiment, an example was described in which an elastic roll was applied to the opposite side of the toner support material, but it is also possible to use an elastic roll on the opposite side.

In addition, it goes without saying that the present invention is applicable to toner supporting devices having three types of widths in the embodiments.

Furthermore, FIG. 7 shows still another embodiment of the present invention, in which the elastic portion 14 of the elastic roller is provided with discontinuous elastic annular bodies disposed close to each other and shafts 11hK. Reference numeral 12 is made of ceramics. In the roller core, 13.15 is a portion having a higher elastic modulus than the elastic portion 14, as described above.

By incorporating this example into constant d'A it, excellent fixing properties as described above were obtained.

Furthermore, in the above embodiment, there is a discontinuous part between the elastic body and the elastic body, or a portion made of the elastic body and another material, at a place where both ends of the support material pass, corresponding to the feed width of the support material used. However, almost uniform pressure can be achieved even if there is some deviation from the inside to the outside.

Preferably, the discontinuous portion of the elastic body may be provided so as to correspond to a position where the width is about 1 to 5 times larger than the feed width of the support material, taking into account conveyance errors. Moreover, the present invention
It can be applied to pressure type devices such as heat fixing and pressure fixing.

As is clear from the above description, the present invention can accurately apply a uniform and sufficient pressure to the toner image during fixing.
The fixing properties are the same: 1:.

It is possible. Further, the present invention can provide a device with a durability ratio superior to that of the prior art.

[Brief explanation of the drawing]

Figure 1, Figure 2-a, Figure 2-S, Figure 43-a, g3
44-a and 4-b are explanatory diagrams of a conventional fixing device, FIG. 5 is an explanatory diagram of an embodiment of the present invention, and FIG.
The figures are still another explanatory diagram of the implementation and example of FIG. 5, and FIG. 7 is an explanatory diagram of the main part of another embodiment of the present invention. . 1.2 is a row 2.3 is an elastic roller, 4□, 4. is the side plate,
5 is a pressure adjustment screw, 6 is a pressure spring, 7 is an elastic roller, 8 is a metal roller, 71w 71*'y,, 74wTaF
i elastic body, 13.15 is the part, 14 is the elastic part, OII'
i fulcrum, PFi conveyance reference side edge, P is side edge, R' is applied pressure, Pl is boundary, S is paper Applicant: Canon Co., Ltd.

Claims (1)

[Scope of Claims] In a fixing device that clamps and conveys a support material supporting an unfixed image and fixes the unfixed image to the support material, an elastic body discontinuous in a direction crossing the rotation direction is provided. 1. A fixing device comprising a rotating body having a rotating body, wherein when the supporting material passes, an elastic body elastically deforms at least in a region where the supporting material passes to compensate for discontinuities in the region.