JP4963623B2 - Image forming apparatus - Google Patents

Description

The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine, and a multifunction machine, and more particularly to an image forming apparatus provided with a roller mechanism such as a conveyance roller provided in the main body of the image forming apparatus .

  In general, in order to transfer and record an image formed by an image forming unit of an image forming apparatus such as a copying machine on a sheet such as a recording sheet, various types of rollers such as a conveyance roller that conveys the sheet toward the image forming unit. A roller mechanism is provided.

  Conventionally, for example, a roller shaft used as a roller shaft in a conveyance roller is finished by finishing a solid steel bar to a predetermined outer diameter by grinding or polishing, or machining a hollow pipe steel pipe to a required dimension. There is something. When manufacturing a transport roller having a pipe roller shaft as a rotation axis, for example, the following procedures and processes are executed. The roller shaft serving as the roller shaft is manufactured by cutting a regular pipe material into a predetermined length and performing required machining. The roller member is formed by press-fitting or shrink fitting a rubber cylinder on the outer periphery of the roller shaft, or directly baking or molding a rubber material or an elastic polymer. Thus, a conveyance roller in which the roller shaft and the roller member are integrated is obtained. Incidentally, the outer diameter of the roller member is polished or the like so that accuracy of roundness and coaxiality is obtained. Many techniques have been proposed for manufacturing such roller shafts (see, for example, Patent Document 1). In the case of a conveying roller, for example, both ends of a roller shaft are rotatably supported by bearings, and a “roller mechanism” is configured by connecting a passive gear or the like to one end of the roller shaft. The passive gear meshes with the reduction gear train, and the rotation output from the motor of the rotational drive source is transmitted to the passive gear through the reduction gear train and the like, thereby rotating the transport roller.

  In addition to the transport roller, the roller mechanism can be used for various purposes. The image forming apparatus is used not only for the conveying roller for conveying the sheet to the image forming unit, but also for a charging roller that uniformly charges the surface of the photosensitive drum as an image carrier by applying a charging bias voltage. . Further, it is also used as a transfer roller for transferring an image obtained by converting an electrostatic latent image on a photosensitive drum into a toner image with a developer (toner).

Japanese Patent Laid-Open No. 4-312209

  By the way, in such a roller mechanism, when a pipe is used for the roller shaft, it is necessary to relatively increase the outer diameter of the shaft in order to obtain the same mechanical strength and rigidity as those of a solid roller shaft. . As the outer diameter increases, peripheral equipment and components such as bearings become larger and larger, and the installation space must be expanded as much as possible. This is very disadvantageous in the internal space of the image forming apparatus main body, which is strictly restricted. Further, for the hollow roller shaft itself, the space in the shaft is a useless space that has not been used so far, and attention can be paid to its effective use. For example, if an integrated structure is realized by incorporating devices and members of a drive transmission system in the internal space of the hollow roller shaft, it is possible to contribute to a reduction in component costs and a reduction in the installation space in the image forming apparatus main body.

  In addition, if an integrated structure is formed by incorporating other members into the internal space of the hollow roller shaft, it is expected that the rigidity when the roller shaft is a single body can be secured and compensated. If the required rigidity can be secured, for example, when used as a sheet conveying roller in the image forming apparatus main body, there is a concern that the sheet being conveyed may be skewed or wrinkled due to insufficient rigidity or a decrease in flexibility. Is wiped out. As a result, it is considered that paper jam (jam) prevention and constant image quality can be maintained, and the obtained effect is great.

  From the above, the object of the present invention is particularly useful as a roller for a conveying system, so that the installation space can be reduced, the cost can be reduced by reducing the number of parts, and the required mechanical strength is guaranteed and the functionality is excellent. Another object of the present invention is to provide an image forming apparatus equipped with such a roller mechanism.

In order to achieve the above object, an image forming apparatus of the present invention includes a first roller shaft that is rotatably supported at both ends via bearings and formed in a cylindrical shape , and an end portion of each end of the first roller shaft. A second roller shaft that is rotatably supported by using a fitting portion that is fitted to the inner periphery and is rotatable as a bearing portion, and is disposed inside the first roller shaft; and A first roller member provided on an outer periphery, and a second roller member that is rotated by driving transmitted by the second roller shaft, and each of the first roller member and the second roller member has an image. The formed sheets are transported at different positions in the transport direction .

According to the image forming apparatus of the present invention, when separate drive transmission mechanisms such as the first roller and the second roller are required at different positions in the transport direction, the first roller shaft that is the axis of the first roller and the first roller shaft Since the rotation axis of the second roller shaft, which is the axis of the two rollers, overlaps on the same axis, the apparatus main body of the image forming apparatus can be downsized .

  Preferred embodiments of a roller mechanism according to the present invention and an image forming apparatus including the roller mechanism will be described below in detail with reference to the drawings.

  FIG. 1 shows a main part of the apparatus main body 900 of the image forming apparatus according to the present embodiment, which includes a document placing table 906, a light source 907, a reading element (CIS: contact image sensor) 908, a paper feeding unit 909, and an image forming process. The image forming unit 902 is configured to be executed.

  The sheet feeding unit 909 includes sheet cassettes 930 and 931 that store sheets S such as recording sheets and are detachable from the apparatus main body 900. Each sheet cassette 930 and 931 includes a sheet feeding roller (sheet feeding unit). It is equipped.

  The image forming unit 902 includes a photosensitive drum 914 as a cylindrical image carrier, and a process unit such as a developing device 915, a transfer roller 916, a cleaner 918, and a primary charging roller 919 is provided around the drum of the photosensitive drum 914. Has been placed. Further, a conveyance guide 920 is provided on the downstream side of the image forming unit 902, and includes a fixing device 904, a discharge roller 905, and the like.

  Therefore, the apparatus main body 900 operates as follows. A paper feed signal is output from a control device (not shown) provided in the apparatus main body 900. The reflected light irradiated and reflected from the light source 907 to the document D set on the document placing table 906 is replaced with an image signal via a reading element (CIS: contact image sensor) 908. The image signal is transmitted to the laser scanner device 921 and irradiated from a laser light emitting element (not shown) to the photosensitive drum 914 via the polygon mirror 922 and the lenses 923 and 924. The drum surface of the photosensitive drum 914 is charged in advance by applying a charging bias voltage by a primary charging roller 919, and an electrostatic latent image formed by light irradiation is developed by a developing unit 915 and visualized as a toner image. The

  On the other hand, the sheet S fed from the sheet feeding unit 909 is corrected in skew by the registration rollers 910 and further conveyed to the image forming unit 902 at the same timing. In the image forming unit 902, the toner image on the photosensitive drum 914 is transferred to the sheet S by the transfer roller 916, and the sheet S that has received the transfer of the toner image is separated from the photosensitive drum 914.

  The sheet S separated from the photosensitive drum 914 is sent to the fixing device 904 by the conveying device 920, and the unfixed transfer image is permanently fixed to the sheet S by the fixing device 904 by pressing and heating. The sheet S on which the image is fixed is discharged from the apparatus main body 900 by a discharge roller 905.

(Roller mechanism: First embodiment)
FIG. 2 shows a roller mechanism including a first roller (first roller member) 1 for conveying a sheet and a second conveying system constituting the first conveying system in the apparatus main body 900. As a specific example of the first roller 1, a registration roller 910 (see FIG. 1) can be applied.

  Referring to FIG. 3, the first roller 1 constituting the first transport system has a hollow cylindrical first roller shaft 3 using a stainless pipe (SUS304) or the like as a main member. The outer diameters of the both ends of the first roller shaft 3 are narrowed once and stepped, and are supported by the small diameter portions of the both ends of the first roller shaft 3 via bearings 2a and 2b. When narrowing both ends of the shaft to a small diameter, spinning, swaging, and pressing are performed. Thus, the first roller shaft 3 is mass-produced with high accuracy, and processing costs and material costs are kept low.

  On the outer periphery of the first roller shaft 3, a roller member 4 made of a rubber material or an elastic plastic material is formed by injection molding or the like, or a single piece processed into a cylindrical shape on the first roller shaft 3. Are combined and integrated by means such as shrink fitting or press fitting. Thereby, the main body of the first roller 1 that functions as a conveying roller for conveying the sheet in the conveying direction is configured. There is no particular limitation on the material of the roller member 4. A material coated with a high friction material in contact with the sheet S during conveyance is used, and is molded with a coating thickness necessary to ensure the required durability. The coating layer is set in such a range that the circumferential length of the outer periphery of the roller caused by wear falls within the allowable range of the sheet conveying speed.

  As shown in FIG. 3, the first roller shaft 3 is rotatably supported on the side plates 5 and 12 of the apparatus main body 900 via bearings 2a and 2b at the small diameter portions at both ends. A passive gear 6 is fitted and fixed to the outer periphery of the small-diameter portion on one end side, and the rotational power output from the rotational drive source motor 8 (see FIG. 2) by the passive gear 6 passes through the reduction gear train 7. Receive. The first roller 1 composed of the first roller shaft 3 and the roller member 4 is rotationally driven at a required rotational speed (rpm) by the motor rotational power transmitted to the passive gear 6 to constitute a first transport system.

  In addition to the first roller 1 that constitutes the first conveyance system, a second roller (second roller member) 15 that constitutes the second conveyance system is disposed with the rotation axis parallel to the first roller 1. . A second roller shaft 9 that functions as a drive shaft for the second roller 15 is inserted inside the first roller shaft 3 so as to have the same rotational axis as the first roller shaft 3. As a specific example of the second roller 15 constituting the second transport system, it can be applied to the discharge roller 905 shown in FIG.

  The second roller shaft 9 that constitutes the second conveyance system together with the second roller 15 is a thin rod-shaped member that is made of, for example, solid stainless steel, and the first roller shaft 3 of the first roller 1 is used. The inside is inserted coaxially. The second roller shaft 9 is fitted to the inner periphery of the small diameter portion at both ends of the first roller shaft 3, and is supported rotatably by using the fitting portion as a bearing, and further protrudes outward therefrom. . The passive gear 10 is coupled to one end side that has penetrated, and the pulley 13 is coupled to the other end side. As shown in FIG. 4, the rotational power output from the motor 11 that is the rotational drive source of the second transport system is transmitted to the passive gear 10, rotated with the second roller shaft 9 as the drive shaft, and from the pulley 13 to the timing belt. 14, the discharge roller 905 in FIG. The pulley 13 and the timing belt 14 constitute a second conveyance system together with the second roller shaft 9 and the second roller 15.

  That is, in the present embodiment, the first roller shaft 3 of the first roller 1 is supported and fixed to the side plates 5 and 12 via the bearings 2a and 2b at the small diameter portions at both ends thereof. On the other hand, the second roller shaft 9 of the second conveyance system is rotatably supported and fixed with the fitting portion fitted to the inner periphery of the small diameter portion of the first roller shaft 3 as a “bearing portion”. Accordingly, the first roller shaft 3 and the second roller shaft 9 can be rotated independently and independently without interfering with each other, and function as a first transport system and a second transport system.

  As understood from the above, the first and second roller shafts 3 and 9 have a coaxial inner / outer double structure. That is, the first transport system and the second transport system “share” one rotation axis. Therefore, in the case of a structure that is customary for the two transport systems, the first and second roller shafts 3 and 9 are arranged with a certain distance between the axes with the rotation axes parallel. In the case of the present embodiment, by sharing one rotation axis and one rotation axis, it is possible to reduce the space for estimating the distance between the axes, which is effective in suppressing the increase in the size of the apparatus main body 900. In addition, there is a synergistic effect that the reduced space can be used for installing other members such as a conveyance guide and a sheet detection sensor.

(Roller mechanism: Second embodiment)
Next, FIG. 5 and FIG. 6 show a second embodiment according to the present invention. The first roller 51 of the second embodiment also has a hollow cylindrical first roller shaft 53, and is similar to that of the first embodiment up to the structure in which both narrowed ends are rotatably supported by bearings 52. is there. The technique of providing a roller member 54 made of rubber or the like on the outer periphery of the first roller shaft 53 is the same as that in the first embodiment. The difference from the first embodiment is the following structure.

  In FIG. 6, a passive gear 56 that is fitted to the outer periphery of the small-diameter portion on one end side of the first roller shaft 53 that is thinly drawn and indicated by reference numeral 58 in the drawing and receives rotational power from the motor of the rotational drive source is coupled. The small diameter portions at both ends are fitted to the tips and supported by bearings 52 and 52. The structure of the bearing 52 is characteristic.

  That is, the bearing 52 has a first bearing surface that abuts the tip surface of the small-diameter portion of the first roller shaft 53 and supports the outer periphery of the tip surface so as to be rotatable. Further, a step is formed with the first bearing surface, and the end portion of the second roller shaft 59 penetrates and is formed to have a second bearing surface that is rotatably fitted and supported.

  As the second roller shaft 59 of the second transport system, the inner space of the first roller shaft 53 is coaxially inserted, inserted into the inner circumference of the small diameter portion at both ends of the first roller shaft 53, and The bearing 52 is rotatably supported in a form that fits and penetrates the second bearing surface of the bearing 52. A passive gear 55 and a transmission gear 57 are coupled to the most distal end portions of both ends of the second roller shaft 59 that have passed through the bearing 52 by fitting to constitute a second drive system. The drive transmitted to the transmission gear 57 is transmitted to a discharge roller 905 which is a roller member different from the first roller by a belt or the like.

  Therefore, also in the second embodiment, the first roller shaft 53 is supported by the bearings 52 at the small diameter portions at both ends, and the second roller shaft 59 is rotatably supported by the inner periphery of the small diameter portion. As the bearing 52 for rotating and supporting both the first and second roller shafts 53 and 59 with two bearing surfaces, an integrally molded product molded with a high sliding grade resin such as POM can be used. . By machining the first bearing surface and the second bearing surface of the bearing 52 with high accuracy, the rotation axes of the first roller shaft 53 and the second roller shaft 59 can be realized with high accuracy coaxiality. Further, the use of a highly slidable resin reduces wear and enhances the durability of the apparatus. If it is an integrally molded product, the number of parts can be reduced, and the cost of parts can be reduced.

(Roller mechanism: Third embodiment)
Next, FIG. 7 and FIG. 8 show the first roller 61 of the third embodiment according to the present invention, which has a hollow cylindrical first roller shaft 63 as in the first and second embodiments. A roller member 64 made of rubber or the like is formed on the outer periphery of the first roller shaft 63. In the first and second embodiments, the first roller shaft supported by the bearing is based on a structure in which the second roller shaft is supported on the same inner axis. On the other hand, in the third embodiment, the second roller shaft 69 on the coaxial inner side is supported by the side plates 5 and 12 (see FIG. 2) via the bearings 62 and 62 at both ends, and the second roller shaft 69 An outer first roller shaft 63 is supported so as to ride. That is fundamentally different from the structures of the first and second embodiments. The following is the detailed structure.

  Both end portions of the first roller shaft 63 are not drawn as thinly as in the first and second embodiments, but remain in a straight shape, and a passive gear 66 is joined to one end portion thereof by press-fitting, A stopper-shaped plug 68 is joined to the other end by press-fitting or the like. Rotational power is received by a passive gear 66 from a motor (not shown) as a rotational drive source, and the first roller 61 is rotationally driven to constitute a first transport system.

  The second roller shaft 69 of the second transport system is inserted coaxially through the first roller shaft 63 and also passes through the passive gear 66 and the plug 68 at both ends of the first roller shaft 63. The second roller shaft 69 is rotatably supported by bearings 62 and 62 at both ends. A passive gear 65 is coupled to one of both ends of the second roller shaft 69 that is supported by the bearings 62 and 62 and further protrudes outward, and a transmission gear 67 is coupled to the other. The drive transmitted to the transmission gear 67 is transmitted to a discharge roller 905 which is a roller member different from the first roller by a belt or the like.

  Accordingly, in the third embodiment, the inner second roller shaft 69 is supported by the bearings 62, 62, and the passive gear 66 and the plug 68 that are coupled to the outer periphery of the second roller shaft 69 that is supported by press-fitting are plugged. Thus, the first roller shaft 63 is coaxially and rotatably supported. The first roller shaft 63 is rotationally driven from the passive gear 66 at a required rotational speed, and the second roller shaft 69 can rotate at an original rotational speed without interfering with the first roller shaft 63. .

  As can be seen from the above description and the drawings, in the case of this embodiment, both ends of the first roller shaft 63 are not drawn to a small diameter at one end as in the first and second embodiments. The part is straight and has not been specially drawn. The passive gear 66 is press-fitted and coupled to one side of the outer periphery of both straight ends, and a stopper-shaped plug 68 is press-fitted and coupled to the other side. Accordingly, the number of steps and man-hours are reduced by the amount that the drawing process is not performed on both ends of the first roller shaft 63, and the cost can be reduced. In addition, the passive gear 66 and the plug 68 at both ends also serve as a “bearing” for the first roller shaft 63 and are rotatably supported on the outer periphery of the second roller shaft 69, and are processed by high precision coaxiality. Then, it becomes possible to constitute a highly accurate transport system.

  As mentioned above, although several embodiment was described about this invention, it is not limited to these embodiment within the range which does not deviate from the main point of this invention, Other embodiment, an application example, a modification, and those combinations are also included. Is possible. For example, the discharge roller 905 is driven by the second roller shafts 9, 59, and 69. However, the rotational drive from the second roller shafts 9, 59, 69 may be transmitted to rotate any rotating body in the image forming apparatus. Although the timing belt is illustrated as the drive transmission member that transmits the rotation of the second roller shafts 9, 59, and 69 to the discharge roller 905, other members such as a gear train may be used.

  In each of the above embodiments, as shown in FIG. 1, an example of application to the registration roller 910 as the first roller and an example of application to the discharge roller 905 as the second roller have been described. The registration roller 910 requires a separate drive transmission mechanism such that the registration roller 910 repeatedly stops and repeats the image forming speed to align the leading edge of the sheet S, and the discharge roller 905 repeatedly accelerates and decelerates to discharge to the discharge tray. Therefore, it is optimal to be applied to the first roller and the second roller, and among the many effects described above, the distance between the axes of the rotation axes overlaps on the same axis, which can contribute to downsizing of the apparatus. This is a great advantage.

1 is a diagram illustrating an example of an image forming apparatus equipped with a roller mechanism according to a first embodiment of the present invention. The perspective view which shows the roller mechanism of 1st Embodiment. Sectional drawing which shows the roller mechanism of 1st Embodiment. The figure which shows the one side structure of the roller mechanism of 1st Embodiment in detail. The perspective view which shows the roller mechanism of 2nd Embodiment by this invention. Sectional drawing which shows the roller mechanism of 2nd Embodiment. The perspective view which shows the roller mechanism of 3rd Embodiment by this invention. Sectional drawing which shows the roller mechanism of 3rd Embodiment.

Explanation of symbols

1 First roller (first roller member)
2a, 2b Bearing 3 Hollow cylindrical first roller shaft 4 Roller member 5, 12 Side plate 6 Passive gear 8 First transport system rotational drive source motor 11 Second transport system rotational drive source motor 9 Solid shaft second Roller shaft 15 Second roller (second roller member)
900 Image forming apparatus main body 902 Image forming unit 905 Discharge roller (first transport system)
904 Fixing device 909 Paper feed unit 910 Registration roller (second transport system)
915 Developing device 921 Laser scanner 914 Photosensitive drum

Claims (2)

Both end portions are rotatably supported via bearings, and a first roller shaft formed in a cylindrical shape,
A second roller that is rotatably supported by using a fitting portion that is fitted to the inner periphery of both end portions of the first roller shaft and is rotatable as a bearing portion, and is disposed inside the first roller shaft. A shaft,
A first roller member provided on an outer periphery of the first roller shaft;
A second roller member that is rotated by driving transmitted by the second roller shaft ,
Wherein each of the first roller member and the second roller member, the image forming apparatus characterized by conveying the sheet on which an image is to be formed at mutually different positions in the conveying direction. The first roller member is a registration roller that corrects skew of a sheet before an image forming process is executed,
The image forming apparatus according to claim 1, wherein the second roller member is a discharge roller that discharges the sheet to the outside of the apparatus main body after the image is fixed.

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