JP2005055721A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize the reduction of man-hour required for assembly or disassembly and the prevention of the cost rise of an image forming apparatus by simplifying the positioning structure in the shaft direction of a heat roller. <P>SOLUTION: The heat roller fixing type image forming apparatus 1 is provided with ribs 13 and 13 abutting on the end face 6a of the heat roller 6 in the shaft direction of the roller 6 on the fixing frame 8 of a fixing device 4, and the cross-sectional area of the roller 6 perpendicular to the shaft direction of the roller 6 is set to be the narrowest at the leading edge part of the roller 6 opposed to the ribs 13 and 13, and the ribs 13 and 13 abut only on a part of the end face 6a on a plane perpendicular to the shaft direction of the roller 6. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a heat roller fixing type image forming apparatus.

  Conventionally, in an image forming apparatus provided in a printer, a facsimile, or the like, a heat roller fixing method capable of fixing toner at high speed has been generally employed.

In such a heat roller fixing type fixing device, the heat roller is prevented from coming off in the axial direction, for example, as follows.
First, the heat roller is supported by the main body frame of the fixing device via a bearing so as to be rotatable in a radial direction (a direction perpendicular to the axis) and axially movable. Groove processing is performed on the peripheral surface of the heat roller, and when a notch ring such as a C ring is fitted into the groove, a protrusion is provided on the outer periphery of the roller. Then, the movement of the heat roller in the axial direction is restricted using the contact between the protrusion and the bearing of the main body frame.

Further, in the technique disclosed in Patent Document 1, a protruding portion is provided on the outer periphery of the heat roller by forming a ring-shaped protrusion that is integrally fired on the outer periphery of the heat roller.
In the case of this technique, there is an advantage that the strength does not decrease even if the roller is thinned, as compared with a configuration in which the peripheral surface of the roller is grooved and the ring is fitted.

JP-A-8-292672

In the configuration in which the protrusion is provided on the outer periphery of the heat roller, in the case of a configuration in which a groove is formed on the peripheral surface of the roller and the ring is fitted, the number of parts is large, and the number of assembling steps is accordingly increased. It was.
Moreover, in recent years, due to environmental problems, a device design that is easy to disassemble is desired. However, if a ring is fitted, disassembly workability is deteriorated.
Further, in order to shorten the warm-up time, the roller tends to be thinned to reduce the heat capacity of the heat roller. However, if the roller is thinned, groove processing cannot be performed in the first place.

  Further, in the case of the technique disclosed in Patent Document 1, it is necessary to integrally fire ring-shaped protrusions on the outer periphery of the heat roller, which is restricted by an increase in the number of manufacturing steps of the heat roller and selection of materials.

  That is, the problem to be solved is to simplify the positioning structure of the heat roller in the axial direction, to reduce the man-hours required for assembly and disassembly and to prevent the cost of the image forming apparatus from increasing.

  The problems to be solved by the present invention are as described above. Next, means for solving the problems will be described.

That is, in claim 1, an image forming apparatus of a heat roller fixing system,
The image forming apparatus main body is provided with a contact portion that comes into contact with the end surface of the heat roller in the axial direction.
As this action, the heat roller comes into contact with the contact portion at the end portion in the axial direction, and movement to the corresponding portion side is restricted. In particular, the heat roller is positioned in the axial direction by providing contact portions on both end sides in the axial direction of the heat roller.

According to a second aspect of the present invention, the cross-sectional area perpendicular to the axial direction of the heat roller is the narrowest at the end surface in contact with the contact portion.
As this action, the frictional resistance at the contact portion between the heat roller and the contact portion is reduced.

According to a third aspect of the present invention, the contact portion contacts only a part of the end surface of the heat roller.
As this action, the frictional resistance is reduced as compared with the case where the entire end face of the heat roller in the axial direction is in contact with the contact portion, and the rotation of the heat roller becomes smooth.

According to a fourth aspect of the present invention, the contact portion is formed integrally with the frame of the fixing device that supports the heat roller and the press roller.
As this effect, there is no positional deviation between the heat roller and the press roller. There is no problem with the fixing process.

  As effects of the present invention, the following effects can be obtained.

  According to the first aspect of the present invention, the movement of the heat roller in the axial direction can be restricted without providing a protrusion on the outer periphery of the heat roller, and the roller positioning structure in the axial direction is simplified.

  The durability of the image forming apparatus is improved.

  The durability of the image forming apparatus is improved.

  According to the fourth aspect of the present invention, there is no occurrence of a printing error or a printing position misalignment in the toner fixing process.

An image forming apparatus 1 according to an embodiment of the present invention will be described with reference to the drawings.
The image forming apparatus of the present invention is an apparatus adopting a heat roller fixing system, and includes a heat roller and a press roller, and is configured to perform toner fixing by applying heat and pressure to toner on a recording sheet.
Examples of image forming apparatuses that employ the heat roller fixing method include facsimile machines and printers.

As shown in FIG. 1, the image forming apparatus 1 is provided with a paper feeding device 50 as a supply source of the recording paper 8, and a recording paper conveyance path 10 passing from the paper feeding device 50 to the image forming apparatus 1 is provided. Is formed.
A developing device 2 including a toner chamber 22, a photosensitive drum 3, a transfer roller 32, and a fixing device 4 are arranged along the recording paper conveyance path 10 with the paper feeding device 50 as the most upstream and downstream. The image forming apparatus 1 is configured by these devices, and image information is transferred to the recording paper 8 fed out from the paper feeding device 50, and toner is fixed.

As shown in FIGS. 1 and 2, the fixing device 4 includes a heat roller 6 and a press roller 7 that face each other with a recording paper conveyance path 10 interposed therebetween.
The heat roller 6 is formed of a hollow cylindrical member and is formed of aluminum in the present embodiment, but may be formed of iron, stainless steel, or the like. Further, heating means such as a halogen lamp 27 is disposed inside the heat roller 6 so that the heat roller 6 is heated.
The press roller 7 is configured by covering a metal roller shaft 14 with rubber 15.
Then, the heat roller 6 and the press roller 7 heat and press the recording paper 8 onto which the toner image has been transferred between the rollers 6 and 7 to fix the toner image on the recording paper.

  A driving gear 12 for transmitting a rotational driving force to the heat roller 3 is provided at the end of the heat roller 6. As shown in FIG. 1, the drive gear 12 meshes with a gear 29 provided in the drive transmission mechanism 28 provided in the image forming apparatus 1, and rotates in conjunction with the drive of the drive transmission mechanism 28. The heat roller 3 that is integral with the drive gear 12 is rotationally driven by the drive transmission mechanism 28.

Next, the peripheral structure of the heat roller 6 will be described with reference to FIGS.
In the present embodiment, the image forming apparatus 1 is provided with a fixing device 4 including a heat roller 6 and a press roller 7. The heat roller 6 is supported by the fixing frame 8 of the fixing device 4 and is supported by the main body of the image forming apparatus 1.
In the following, the direction is defined with the recording paper conveyance direction as the front-rear direction.

  As shown in FIG. 2, bearings 9 are provided at both ends of the heat roller 6 in the axial direction. The bearings 9 and 9 are respectively fixed to ribs 8a and 8a formed on the fixing frame 8 so as to protrude toward the heat roller 6 side. The heat roller 6 is restrained from moving in the radial direction (direction perpendicular to the axial direction) by the bearings 9.

A driving gear 12 is provided on the outer periphery of the heat roller 6 at one end of the heat roller 6.
Specifically, a long hole (U-shaped) notch 6b is formed in the heat roller 6 toward the inner side of the axial roller end surface 6a, and a protruding portion 12a fitted to the notch 6b. Is formed so as to protrude from the inner periphery of the drive gear 12. The drive gear 12 is restrained from moving in the radial direction of the roller 6 with respect to the heat roller 6 by the fitting of the notch 6b and the protrusion 12a. The drive gear 12 meshes with a gear provided in a drive transmission mechanism (not shown) and is rotationally driven by driving the drive transmission mechanism. With the above-described fitting configuration, the drive gear 12 and the heat roller 6 are driven. And rotate together.
Further, the axial positioning of the drive gear 12 with respect to the heat roller 6 is performed by a rib 8b formed on the fixing frame 8 so as to protrude toward the heat roller 6 side. The heat roller 6 is positioned in the axial direction with respect to the fixing frame 8 by the configuration described below, and accordingly, the driving gear 12 is positioned in the axial direction with respect to the fixing frame 8.

As shown in FIGS. 2 and 3, the fixing frame 8 is provided with a contact portion that comes into contact with the end surface (roller end surface 6 a) in the axial direction of the heat roller 6.
The abutting portion is composed of ribs 13 and 13 formed on the inner surface of the fixing frame 8, and the rib end surfaces 13 a of the ribs 13 facing the roller end surface 6 a abut on the roller end surface 6 a.
In the present embodiment, the corresponding portion is provided on both ends of the heat roller 6.

For this reason, the heat roller 6 comes into contact with the contact portion at the end portion in the axial direction, and the movement toward the corresponding portion is restricted.
In particular, the heat roller 6 is positioned in the axial direction by providing contact portions on both ends of the heat roller 6 in the axial direction.

Therefore, the movement of the heat roller 6 in the axial direction can be restricted without providing a protrusion on the outer periphery of the heat roller 6, and the roller positioning structure in the axial direction is simplified.
On the other hand, when the protrusion is formed on the outer periphery of the heat roller 6 as in the prior art, a groove is formed on the heat roller 6 to fit the ring, or the protrusion is integrally formed on the outer periphery of the heat roller 6. It is necessary to increase the number of members, increase the number of assembling and disassembling processes, or process the heat roller 6.

  In the present embodiment, the heat roller 6 is configured to be restricted from moving in the axial direction by contact portions (ribs 13 and 13) provided in the fixing frame 8 provided in the fixing device 4. Here, the heat roller 6 only needs to be configured to be supported by a fixed frame in the image forming apparatus 1, and the contact portion is disposed on the fixing frame 8 that is one of the fixed frames in the image forming apparatus 1. It is not limited.

  In the present embodiment, each rib 13 is formed of a POM (polyacetal) resin having high frictional wear resistance and fatigue resistance performance. Each rib 13 may be formed of ABS (acrylonitrile butadiene styrene) resin.

The press roller 7 is supported by the fixing frame 8 with the following configuration.
Support frames 16 and 16 for supporting the press roller 7 are respectively arranged on the left and right sides (in the recording paper conveyance direction) of the fixing frame 8, and the support frames 16 and 16 are fixed to the fixing frame 8. ing.
Each support frame 16 is provided with a movable body 17 that pivotally supports the end of the roller shaft 14 so that the press roller 7 is slidably supported in the direction of the heat roller 6 (vertical direction).
In addition, a spring 19 is interposed between each moving body 17 and the support frame 16 so that the press roller 7 is urged toward the heat roller 6.

That is, the heat roller 6 and the press roller 7 are supported on the fixing frame 8 of the fixing device 4.
Further, the contact portion that contacts the roller end surface 6 a in the axial direction of the heat roller 6 is formed integrally with the fixing frame 8.

  For this reason, no positional deviation occurs between the heat roller 6 and the press roller 7. There is no problem with the fixing process.

  Therefore, in the toner fixing process, no printing error or printing position deviation occurs.

Further, as shown in FIGS. 2 and 3, the ribs 13 and 13 constituting the contact portion are provided so as to contact only a part of the roller end surface 6a.
Here, the ribs 13 and 13 are in contact with the roller end surface 6 a in a plane perpendicular to the axial direction of the heat roller 6. The entire end surface of the heat roller 6 is annular in a plane perpendicular to the axial direction of the heat roller 6, but the ribs 13 and 13 are in contact with only a part of the annular portion.

  For this reason, the frictional resistance is reduced and the rotation of the heat roller 6 becomes smooth as compared with the case where the entire roller end surface 6a in the axial direction of the heat roller 6 contacts the contact portion.

  Therefore, the durability of the image forming apparatus 1 is improved.

As shown in FIG. 4, the end of the roller in the axial direction of the heat roller 6 is chamfered. This is a configuration for reducing the contact area on the heat roller 6 side in contact between the heat roller 6 and the contact portion (rib 13).
Here, the heat roller 6 is formed in a cylindrical shape with a constant thickness, and the cross-sectional area (cross-sectional area perpendicular to the axial direction) is basically constant at any part in the axial direction. . This cross-sectional area is proportional to the constant thickness L0 of the heat roller 6.
By the way, at the end of the roller, the chamfering process is performed, so that the cross-sectional area is narrower than the portion other than the end. That is, in the heat roller 6 having a constant thickness, the thickness at the end is exceptionally thin. Therefore, this cross-sectional area is minimized at the end of the heat roller 6. The wall thickness L1 at the end of the roller 6 is thinner than the wall thickness L0, and therefore the cross-sectional area is narrower than that of the portion having the wall thickness L0.

  In other words, the heat roller 6 is formed such that the cross-sectional area (cross-sectional area perpendicular to the axial direction) of the heat roller 6 is the narrowest at the end surface in contact with the contact portion.

  For this reason, the frictional resistance in the contact | abutting with the heat roller 6 and the said contact part (rib 13) is reduced.

  Therefore, the durability of the image forming apparatus 1 is improved.

Note that the configuration for reducing the contact area between the roller 6 and the ribs 13 and 13 on the heat roller 6 side is limited to a configuration in which chamfering is performed on the roller end as in the present embodiment. It is not a thing.
Next, the case where the end of the heat roller is rounded will be described.

The configuration of the heat roller 106 according to the second embodiment of the present invention will be described with reference to FIG.
The image forming apparatus according to the second embodiment is different from the heat roller 6 only in the processing configuration of the end portion of the heat roller 106, and the other points are the same. To do.
In the heat roller 106, the roller end is rounded, and the contact area between the roller end surface 106a and the rib end surface 13a is narrower than the portion excluding the end in the axial direction. . Here, the roller end surface 106a indicates the area of a portion parallel to the rib end surface 13a in the end portion of the heat roller 6 formed in a curved surface shape. The thickness L2 at the end of the roller 106 is thinner than the thickness L0 of the portion excluding the end, and therefore the cross-sectional area is also narrower than the portion of the thickness L0.

In particular, the contact between the heat roller 6 and the rib 13 is not limited to surface contact, and may be point contact or line contact. For example, when the cross-sectional shape (the cross-sectional shape along the axial direction) of the end portion of the heat roller 6 is formed in a semicircular shape by rounding, the contact between the heat roller 6 and the rib 13 is a line contact. .
In other words, on the heat roller side, a configuration for reducing the contact area between the heat roller and the ribs 13 and 13 is that the cross-sectional area perpendicular to the axial direction of the heat roller is the largest roller facing the contact portion. What is necessary is just to make it become the narrowest at an edge part.

The configuration of the fixing device 204 in the third embodiment of the present invention will be described with reference to FIG.
The image forming apparatus according to the third embodiment is different from the fixing device 4 according to the first embodiment only in the configuration of the ribs for positioning the heat roller 6 and the drive gear 12. Since it is the same, the description regarding the same point is abbreviate | omitted.

As shown in FIG. 6, ribs 213 and 213 protrude from the inner surface of the fixing frame 208 at both ends of the heat roller 6. In each rib 213, a roller side rib end surface 213a facing the roller end surface 6a and a gear side rib end surface 213b facing the drive gear 12 are formed in a step difference (so that the axial position is different).
The heat roller 6 is substantially in contact with both of the roller side rib end surfaces 213a and 213a at both ends thereof, so that movement in the axial direction is restricted, and the axial positioning of the heat roller 6 with respect to the fixing frame 208 is performed. Further, the driving gear 12 is positioned with respect to the heat roller 6 by the gear side rib end surface 213b, and the positioning of the driving gear 12 in the axial direction with respect to the fixing frame 208 is performed.

In the above, the ribs 213 and 213 are the contact portions that contact the end surfaces (roller end surfaces 6 a and 6 a) in the axial direction of the heat roller 6, and also the contact portions that contact the drive gear 12. That is, the rib 213 is configured to serve as both the rib 13 of the fixing device 4 and the rib 8a.
Accordingly, the fixing device 4 includes the ribs 213 in the fixing device 204 in addition to the operations and effects of the ribs 13.

1 is a schematic diagram illustrating a configuration of an image forming apparatus 1. FIG. FIG. 6 is a cross-sectional view of the fixing device 4 as viewed from the recording paper conveyance direction. 3 is a cross-sectional view of the fixing device 4 as viewed from the axial direction of the heat roller 6. FIG. FIG. 3 is a cross-sectional view of a main part of the fixing device 4 showing a contact portion between a roller end surface 6a and a rib end surface 13a. FIG. 7 is a cross-sectional view of a main part of a fixing device in a second embodiment showing a contact portion between a roller end surface 106a and a rib end surface 13a. FIG. 10 is a cross-sectional view of a fixing device 204 according to a third embodiment viewed from the recording paper conveyance direction.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 6 Heat roller 6a Roller end surface 7 Press roller 8 Fixing frame 13 Rib 13a Rib end surface

Claims (4)

A heat roller fixing type image forming apparatus,
The image forming apparatus main body is provided with a contact portion that comes into contact with the end surface in the axial direction of the heat roller.
An image forming apparatus. The cross-sectional area perpendicular to the axial direction of the heat roller was made the narrowest at the end surface in contact with the contact portion.
The image forming apparatus according to claim 1. The contact portion is configured to contact only a part of the end surface of the heat roller.
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. The contact portion is integrally formed on the frame of the fixing device that supports the heat roller and the press roller.
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.