JP2754986B2 - Pressure fixing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure fixing device for fixing an unfixed toner image on a supporting surface of an image support by a pair of rollers which are in pressure contact with each other.

[0002]

2. Description of the Related Art In a pressure fixing device, an image support such as a sheet having an unfixed toner image is passed between a pair of rollers in pressure contact with each other, and the toner image is pressed against a support surface of the image support. Is a device for fixing the image. In this type of apparatus that has been frequently used in the related art, since the load tends to concentrate on the ends of the abutted pair of rollers, the shaft centers of the pair of rollers are corrected in order to correct the insufficient pressure at the substantially central portion in the roller axis direction. They cross each other so that the pressure required for fixing is generated substantially uniformly along the axial direction of the roller.

On the other hand, as a device capable of correcting a pressure shortage near a central portion in the roller axial direction without crossing the axis of the roller and obtaining a substantially uniform pressure distribution, one of a pair of rollers is used. There has been proposed a pressure fixing device in which a roller is constituted by a so-called center support roller (JP-A-49-77641). The center support roller above
A roller in which the central portion in the axial direction of the cylindrical sleeve is supported by the rotating shaft from the inner peripheral surface side, and a relatively large pressure acts on the central portion in the axial direction when pressed against another roller. . Therefore, according to this fixing device, since it is not necessary to correct the pressure in the central portion in the axial direction by crossing the axes of the rollers, it is possible to prevent the generation of an axial force and the asymmetric curl generated on the image support after fixing. It is possible to

However, in these conventional fixing devices, when the load applied to the rollers is constant, the distribution of the fixing pressure along the axial direction of the rollers becomes smaller as the width of the image support entering between the pair of rollers becomes smaller. Tends to be non-uniform. This tendency is based on the so-called corner registration type fixing device based on the axial edge of the roller, rather than the so-called center registration type fixing device in which the image support enters between the fixing rollers based on the axial center of the roller. Is more pronounced. The reason will be described below.

FIG. 6 shows the displacement of a roller when a small-sized image support 6 is inserted into a corner registration type fixing device. Reference numeral 20 denotes a fixedly supported fixing roller.
Reference numeral 21 is a pressure roller pressed against the aforementioned fixing roller 20 acts load F _L and F _R at both ends. Here, as shown in FIG. 6, when the width of the image support 6 is sufficiently smaller than the axial length of the rollers 20 and 21, the thickness of the image support between the fixing roller 20 and the pressure roller 21 is increased. A gap 22 is formed. Therefore, when there is a load F _L and F _R at both ends of the pressure roller 21 are equal, since the pressure roller 21 as shown by the solid line is inclined in a direction of narrowing the gap 22, the fixing pressure which acts on the image supporter 6 Is low at the end portions of the rollers 20 and 21, but extremely high at the center. Here, the fixing roller
20 and the pressure roller 21 have been described by taking as an example a roller having both ends supported.However, even when the above-mentioned center support roller is used for one of the rolls, the fixing pressure for the small-sized image support 6 is also reduced. Is non-uniform.

For the above reasons, in the conventional fixing device of the corner resist type, the distribution of the fixing pressure on the small-sized image support is likely to be non-uniform. There are problems that the image support becomes translucent and paper wrinkles occur at a high portion.

As a countermeasure against such a problem, the ratio of the load applied to both ends of the fixing roller is changed according to the width of the image support to prevent the pressure roller from being inclined with respect to the fixing roller. (See Japanese Utility Model Laid-Open No. 57-63362 and Japanese Utility Model Laid-Open No. 62-74262). However, this proposal requires a detector for detecting the width of the image support and a mechanism for changing the load applied to both ends of the roller based on the output signal of the detector, which increases the size and cost of the fixing device. Such a problem occurs.

[0008] By the way, since an image support such as paper absorbs moisture in the air and elongates, the image support left for a long period of time has a wavy edge due to a difference in elongation rate between the center and the periphery. However, when pressure fixing is performed on the image support having such a wavy shape, there is a problem that wrinkles are easily generated on the image support.

In order to solve such a problem, there has been proposed a pressure fixing device using a drum-shaped roller in which the diameter at the central portion in the axial direction is smaller than the diameter at both ends (see, for example, Japanese Patent Application Laid-Open No. H11-157556). See JP-A-57-63362 and JP-A-62-74262. Since the drum-shaped roller has a faster peripheral speed at both ends than that at the center, according to this pressure fixing device,
Even an image support having a wavy peripheral portion can pass between a pair of rollers without generating wrinkles.
However, even in the fixing device according to this proposal, when a small-sized image support is caused to enter between the rollers by the corner registration method, the peripheral speed distribution of the rollers along the axial direction and the location where the image support is wavy are generated. However, it was not possible to prevent wrinkles from being generated on the image support.

[0010]

As described above, in the conventional pressure fixing device, when pressure fixing is performed on an image support having a small width in the feed direction, the distribution of the fixing pressure becomes non-uniform, so that the fixing failure and the image quality may be reduced. There were problems such as damage to the support and wrinkling of the image support, and good fixing could not be performed.

The present invention has been made in view of such a problem, and a first object of the present invention is to provide a substantially uniform pressure distribution along an axial direction without being affected by the width of an image support. It is another object of the present invention to provide a pressure fixing device which can obtain a good fixing strength and can prevent the image support from being damaged.

A second object of the present invention is to provide a pressure fixing device capable of effectively preventing wrinkles from being formed on a fixed image support without being affected by the width of the image support. It is to provide a device.

[0013]

In order to achieve the first object, a first technical means of the present invention comprises a pair of rollers which are in pressure contact with each other, and one of the rollers is a cylindrical roller. A center support roller in which a support shaft is engaged with the inner peripheral surface of the sleeve. The image support having an unfixed toner image passes between the pair of rollers, and the toner image is transferred to the support surface of the image support. In the pressure fixing device for fixing, the engagement position between the sleeve of the center support roller and the support shaft is shifted from the axial center of the sleeve to the position of the image support in accordance with the reference position of conveyance of the image support in the axial direction of the roller. It is characterized by being displaced to the transport reference side.

In order to achieve the second object,
A second technical means of the present invention includes a pair of rollers that come into contact with each other under pressure, and one of the rollers is a drum-shaped roller having a concave curved outer peripheral surface. A pressure fixing device that passes an image support having an unfixed toner image to the support surface of the image support and fixes the toner image on the support surface of the image support in accordance with a transport reference position of the image support in the axial direction of the roller. The minimum outer diameter portion of the roller is displaced from the axial center portion of the roller toward the conveyance reference side of the image support.

[0015]

According to the first technical means, the engagement position between the sleeve of the center support roller and the support shaft is determined in accordance with the axial reference position of the image support in the axial direction of the roller. From the image support to the conveyance reference side of the image support, even when the width of the image support in the feed direction is small, the parallelism of the pair of rollers is substantially maintained, and a substantially uniform pressure distribution is obtained along the axial direction. .

According to the second technical means, the minimum outer diameter of the drum-shaped roller is moved from the axial center of the roller to the transport reference side of the image support in accordance with the transport reference position of the image support. Even when the width of the image support in the feed direction is small, the circumferential speed distribution of the rollers along the axial direction and the location where the image support undulates correspond almost exactly, and the image support Wrinkling is prevented.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a pressure fixing device according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 and FIG. 2 show a first embodiment of the present invention to which the above-mentioned first technical means is applied. The pressure fixing device according to this embodiment is broadly supported by a cylindrical solid roller 2 that is supported by a fixed housing 4 via a bearing 7 and a movable housing 5 that is similarly supported by a bearing 11. The image support 6 is fed between the pair of rollers 1 and 2 with one end of the image support 6 aligned with the transport reference position A. The rollers 1 and 2 have the same size, the effective length is 270 mm, and the outer diameter is 35 mm.

The movable housing 5 and the fixed housing 4 are swingably connected via a connecting shaft 8, and the movable housing 5 is pressed against the movable housing 5 in the direction B in the drawing with a total load of 400 kg. A device 9 is provided. Thus, the image support 6 that enters between the center support roller 1 and the solid roller 2 can be pressed with a predetermined linear pressure.

The center support roller 1 has a cylindrical sleeve 11 having an outer diameter of 35 mm, the surface of which is subjected to hard chrome plating, and penetrates the hollow portion of the sleeve 11 to engage with the inner peripheral surface of the sleeve 11. And a support shaft 12. The support shaft 12 is formed so that the outer diameter of the support portion 13 that engages with the sleeve 11 is gently larger than the outer diameter of both ends, and the support portion 13 is located between the central portion between the pair of bearings 7,7. The sleeve is shifted 30 mm from the image support 6 to the transport reference position A.
11 is engaged. The support shaft 12 is fixed by press-fitting the support portion 13 into the sleeve 11, and the contact length between the support portion 13 and the sleeve 11 is 50 mm.

FIG. 3 shows the distribution of the pressure acting on two types of image supports having different sizes between the pair of rollers 1 and 2. The two types of image supports are an image support in which the width along the axial direction of the roller 1 is less than half the roller length (hereinafter, a small size image support), and a width along the axial direction of the roller is the roller length. (Hereinafter referred to as a large-sized image support). The solid line in FIG. 3 shows the measurement result of the present embodiment in which the engagement position between the sleeve 11 and the support shaft 12 in the center support roller 1 is shifted to the transport reference position A side, while the broken line shows the support shaft.
12 shows measurement results of a comparative example in which a conventional center support roller 12 engages with the center of the sleeve 11 in the axial direction.

As is apparent from the results, in the case of a large-sized image support, there is no large difference in pressure distribution between the present embodiment and the comparative example, and in both cases, a substantially uniform pressure acts over the entire area. ing. However, in the case of a small-sized image support, the pressure at the center of the roller is extremely higher than that at the end in the comparative example. Is smaller than that in the comparative example, which indicates that the pressure distribution is improved.

Therefore, according to the pressure fixing device of the present embodiment, a substantially uniform pressure distribution can be obtained for a large-sized image support in the same manner as the conventional device, and a small-size image support can be obtained. However, a uniform pressure distribution can be obtained as compared with the conventional apparatus, and a good fixing pressure can be applied to all the image supports of various sizes entering the fixing device by the corner resist method.

FIG. 4 shows a second embodiment of the present invention to which the above-mentioned second technical means is applied. The pressure fixing device according to the present embodiment includes a pair of drum-shaped rollers 3 that are supported by a fixed housing 4 and a movable housing 5 via a bearing 7, and in this embodiment, the image support 6 is one of them. The side end is matched with the transport reference position A, and is fed between the drum-shaped rollers 3. Since the fixed housing 4 and the movable housing 5 are the same as those in the first embodiment shown in FIGS. 1 and 2, the same reference numerals are given to FIG. 4 and the description is omitted. In addition, since the drum-shaped roller 3 cannot be discriminated with the naked eye from the cylindrical solid roller 2 shown in the first embodiment, its detailed outer shape is shown in FIG. 5 described later, and FIG. Its outer shape is shown as a solid roller.

The hourglass roller 3 has a concave curved outer peripheral surface, and the difference in radius between the maximum outer diameter portion, that is, both ends of the roller 3 and the minimum outer diameter portion is 15 μm. Although the effective length of the drum-shaped roller 3 is 270 mm, its minimum outer diameter portion is formed at a position shifted from the axial center of the roller 3 by 30 mm toward the transport reference position A of the image support 6. I have. The solid line in FIG. 5 is a graph showing in detail the outer peripheral surface shape of the hourglass roller 3 of the present embodiment,
The horizontal axis represents the position in the roller axis direction with reference to the end, while the vertical axis represents the difference ΔR between the radius at the minimum outer diameter portion and the radius at each position of the roller 3 in the axial direction. For comparison, the outer peripheral surface shape of the conventional drum-shaped roller in which the minimum outer diameter portion is formed at the center in the axial direction of the roller is indicated by a broken line in the same graph.

When the image support 6 was made to enter the pressure fixing device of the second embodiment having the above-described structure and was actually pressed, the wrinkles generated on the small-sized image support were It decreased sharply compared to a pressure fixing device using a drum-shaped roller.
It is considered that this is because the distribution of the peripheral speed of the drum-shaped roller 3 of the present embodiment appropriately corresponded to the location where the extension of the image support 6 occurred when the small-size image support was entered by the corner registration method. .

If one of the pair of drum-shaped rollers 3, 3 is a center support roller, it is not necessary to allow the shaft centers of these rollers 3, 3 to be toleranced. When a center support roller is not used as a roller, it is preferable that the axes of the rollers 3, 3 are made to have a tolerance. Further, in the second embodiment, both of the pair of rollers are constituted by the drum-shaped rollers 3, but if either one is the drum-shaped roller 3, the other may be a roller having a flat outer peripheral surface. .

[0027]

As described above, according to the first pressure fixing device of the present invention, the engagement position between the sleeve of the center support roller and the support shaft is determined by the reference of the conveyance of the image support in the axial direction of the roller. By displacing the center of the sleeve in the axial direction toward the conveyance reference side of the image support according to the position, even if the image support enters the fixing device by the corner registration method, it is affected by the width of the image support. As a result, a substantially uniform pressure distribution is generated along the axial direction, so that good fixing strength can be obtained and damage to the image support can be prevented.

According to the second pressure fixing device of the present invention, the minimum outer diameter portion of the drum-shaped roller is transported from the axial center of the roller in accordance with the transport reference position of the image support. By displacing to the reference side, even if the image support enters the fixing device by the corner registration method, the peripheral speed distribution of the roller along the axial direction and the location where the image support undulates almost exactly correspond However, it is possible to effectively prevent wrinkles of the image support.

[Brief description of the drawings]

FIG. 1 is a front view showing a first embodiment of a pressure fixing device of the present invention.

FIG. 2 is a side view showing a first embodiment of the pressure fixing device of the present invention.

FIG. 3 is a graph showing a distribution of pressure acting on an image support in the first embodiment.

FIG. 4 is a front view showing a second embodiment of the pressure fixing device of the present invention.

FIG. 5 is a graph showing an outer peripheral surface shape of a drum-shaped roller according to a second embodiment.

FIG. 6 is a front view showing a conventional pressure fixing device.

[Explanation of symbols]

1 center support roller, 2 solid roller, 3 drum-shaped roller, 6 image support

Continuation of the front page (72) Inventor Ken Satomi 2274 Hongo, Ebina-shi, Kanagawa, Fuji Xerox Co., Ltd. Ebina Works (56) References JP-A-55-118054 (JP, A) JP, A) JP-A-3-150585 (JP, A) JP-A-62-274262 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 15/20

Claims (2)

(57) [Claims] 1. A center support roller comprising a pair of rollers which are in pressure contact with each other, one of which is constituted by a center support roller having a support shaft engaged with an inner peripheral surface of a cylindrical sleeve. In a pressure fixing device for passing an image support having an unfixed toner image and fixing the toner image on a support surface of the image support, the center support may be moved in accordance with the reference position of the image support in the axial direction of the roller. A pressure fixing device, wherein an engagement position between a sleeve of a roller and a support shaft is displaced from a central portion in the axial direction of the sleeve to a conveyance reference side of the image support. 2. A roller having a pair of rollers which are in pressure contact with each other, and one of the rollers is a drum-shaped roller having a concave curved outer peripheral surface, and an unfixed toner image is provided between the pair of rollers. In a pressure fixing device for passing the image support and fixing the toner image on the support surface of the image support, a minimum outer diameter portion of the drum-shaped roller is provided in accordance with a reference position of the image support in the axial direction of the roller. Wherein the roller is displaced from the axial center of the roller to the conveyance reference side of the image support.