JP4790160B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improvement of a fixing device for heat-fixing a toner image formed on a transfer paper in an electrophotographic image forming apparatus, and more particularly to an improvement of a fixing device using a fixing roller using a thin cored bar. It is.
[0002]
[Prior art]
In an electrophotographic image forming apparatus such as a copying machine, a printer, a facsimile machine, etc., after transferring a toner image on a photosensitive member to a transfer paper, the transfer paper is pressurized while being heated by a fixing device. The image is fixed.
The fixing device includes a fixing roller having a heat source therein, and a heating roller in contact with the peripheral surface of the fixing roller. Recently, in order to reduce the heat capacity of the fixing roller itself to shorten the rise time and save power, a fixing roller made of a thin metal core is used.
However, if the fixing roller is thin, the mechanical strength will decrease, causing deflection in the axial direction, or causing the contact portion with the heating roller to be crushed. It was a cause of failure or damage to the fixing roller.
In order to solve such problems, Japanese Patent Application Laid-Open No. 8-314307 discloses a structure in which a ring of another member is inserted and reinforced in order to reinforce the thin fixing roller.
However, in the fixing device disclosed in the publication, since a separate ring is provided as a reinforcing member for the thin fixing roller, cost increases and productivity decreases due to an increase in the number of parts and an increase in assembly man-hours. Not only does this occur, but the ring may come off due to thermal expansion or deformation during use, and the adhesive will crack when bonded. In addition, defects due to bending or crushing of the core metal still remain.
On the other hand, Japanese Patent Laid-Open No. 2000-29342 discloses a reinforcing structure in which ribs extending in the axial direction, the circumferential direction, and other directions are provided inside the cored bar constituting the fixing roller. For example, the strength and shape retention of the fixing roller can be improved without using a special reinforcing member.
However, among the plurality of ribs provided in the fixing roller of this conventional example, the accuracy of the outer dimension of the core metal is likely to be lowered at the intersecting portions of the ribs whose extending directions are not parallel, and as a result, such a fixing roller. There is a problem that wrinkles are likely to occur on the transfer paper at the time of fixing using the toner.
[0003]
[Problems to be solved by the invention]
The present invention has been made in view of the above, and in a fixing device provided with a fixing roller composed of a thin cored bar, the strength of the cored bar is increased without using a special reinforcing member, so that bending or crushing can be achieved. In order to prevent fixing defects and fixing roller damage, when the ribs extending in the axial direction and circumferential direction are integrally formed on the inner surface of the metal core, the accuracy of the external dimensions that are likely to occur at the intersection of the ribs is reduced. It is an object of the present invention to provide a fixing device and an image forming apparatus that can prevent the above.
[0004]
[Means for Solving the Problems]
As described above, according to the first aspect of the present invention, the fixing roller having the thin cylindrical cored bar having the heat source therein and rotatably supported, and the pressure roller in contact with the outer peripheral surface of the fixing roller When, a fixing device provided with a, the inner peripheral surface of the core metal, in which ribs extending respectively in the axial direction and the circumferential direction are a plurality of formed, by a rib extending in the axial direction in the hollow structure It is formed, and then the rib extending in the circumferential direction is formed in a solid structure . As described above, in the fixing device of the electrophotographic apparatus, since the fixing roller is a thin roller, the fixing roller is configured by providing ribs in the circumferential direction and the axial direction while maintaining fast rising. It is possible to provide a fixing device that suppresses the deflection and crushing of the cored bar and does not cause fixing failure due to insufficient pressure. Also, if the axial ribs and the circumferential ribs are in a solid state with no space, the outer diameter of the roller cannot be accurately determined due to the intersection of both ribs, and the transfer paper is not suitable for fixing. Although there is a problem that wrinkles occur, according to the present invention, there is a hollow portion in the previously formed axial rib, so that when the circumferential rib is formed later, the hollow portion becomes a buffer portion. Thus, deformation of the outer peripheral surface of the cored bar can be mitigated. The invention of claim 2 is characterized in that the thickness of the hollow rib is 30% to 70% of the thickness of the cored bar. With such a configuration, the dimensional accuracy of the fixing roller can be ensured well, and the deflection of the roller can be suppressed during fixing of an unfixed image, thereby preventing wrinkles and fixing defects. According to a third aspect of the present invention, there is provided a fixing roller manufactured by the fixing roller manufacturing method according to the first or second aspect. Therefore, an image forming apparatus having the effects of claims 1 and 2 can be provided.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings.
FIGS. 1A and 1B are a schematic diagram of an entire image forming apparatus using the fixing device of the present invention, and an explanatory diagram of the structure of the fixing device. FIGS. 2A, 2B, 2C, 2D, and 2E. ) Is a front view of the fixing roller according to the present invention, a cross-sectional view thereof (circumferential rib), a cross-sectional view along AA (non-intersecting portion), an enlarged cross-sectional view thereof, and an enlarged cross-sectional view of the crossing portion. It is.
A fixing device of the present invention and an electrophotographic apparatus equipped with the fixing device will be described by taking a printer 1 as an example.
The printer 1 includes a belt-like photoconductor 2 as an image carrier, a charging charger 3 for charging the photoconductor, a laser optical system 4 for writing optical image information on the photoconductor to form an electrostatic latent image, A developing device 5 that supplies toner to the electrostatic latent image and develops it, a transfer charger 6 that transfers the toner image on the photoconductor to the transfer paper, a cleaning device 7 that removes toner remaining on the photoconductor after transfer, and a transfer paper A housed paper cassette 8, a pair of registration rollers 9 for feeding transfer paper fed from the paper feed cassette to a transfer position at a predetermined timing, a fixing device 10 for fixing a transfer paper holding a toner image, A discharge roller 11 for discharging the transfer paper and a discharge tray 11A for stacking the discharged transfer paper are provided.
[0006]
In FIG. 1, the transfer paper conveyed from the paper feed cassette 8 is conveyed to a latent image carrier composed of the belt-shaped photosensitive member 2 at a timing by a registration roller 9. The belt-like photoconductor 2 is rotated in the clockwise direction. At this time, the surface is charged by the charging charger 3 and irradiated with laser light from the laser optical system 4 to form an electrostatic latent image on the photoconductor 2. This latent image is visualized by toner when passing through the developing device 5, transferred to a transfer sheet conveyed to the photosensitive member by the transfer charger 6, and the transfer sheet in close contact with the photosensitive member is separated by the curvature. After that, the transfer paper is conveyed to the fixing device 10 and heated and pressed to fix the toner image on the transfer paper and discharged to the paper discharge tray 11A, while the photoconductor is charged with unnecessary charges by the charge eliminating lamp. After being neutralized, the residual toner is removed by the cleaning device 7 and collected.
The fixing device 10 is means for fixing the toner image on the transfer paper by applying at least heat and pressure to the toner image on the transfer paper. As shown in FIG. 1B, the fixing device 10 includes a fixing roller (heating roller) 12 including a metal core 21 that is rotationally driven with a heat source 19 therein, and an elastic member that is in pressure contact with the peripheral surface of the fixing roller 12 and is driven. A pressure roller 13 composed of a body, a cleaning pad 14 that is in sliding contact with the peripheral surface of the fixing roller 12, a separation claw 15 that separates the transfer paper with the tip close to the peripheral surface of the fixing roller, and pressure applied via a lever 16a. A pressure spring 16 that presses the roller 13 against the fixing roller 12, a fixing inlet guide plate 17, a gear (not shown) that transmits rotational driving force to the fixing roller, a bearing for the fixing roller 12, a thermistor, and the like. P is a transfer paper, and 19 is a heat source composed of a halogen heater.
[0007]
FIG. 4 is a cross-sectional view showing an example of a support structure for rotatably supporting the fixing roller 12 of the present invention. The fixing roller 12 includes a cylindrical cored bar 21 made of a thin metal plate, and ribs 22 and 23 extending in the axial direction and the circumferential direction are formed on the inner peripheral surface of the cored bar 21. Heat insulation bushes 25 are respectively provided on the outer circumferences of both ends in the axial direction of the core metal 21, and the heat insulation bushes 25 are supported by bearings 27 provided on the side plates 26. A gear member 28 is fixed to the outer periphery of one end of the core metal 21, and a driving force from a motor (not shown) is transmitted to the core metal 21 via the gear member 28 and rotates while being supported by the bearing 27. The halogen heater 19 as a heat source is fixedly supported by a support member (not shown).
The cored bar 21 constituting the fixing roller 12 has a diameter of φ20 to φ40 mm, a base material made of an aluminum alloy, a thickness of 0.25 to 0.5 mm, and an axial length of 350 to 410 mm. The thickness of the cored bar 21 is different in deformation at the time of pressurization depending on the roller diameter (even if the same thickness, the larger the roller diameter, the larger the deformation), the ratio of the thickness / outer diameter is 8 / 1000-20 / 1000, preferably 12/1000 to 20/1000. When this ratio is smaller than the above range (when the thickness of the core metal becomes too small), the deformation at the time of pressurization is large, wrinkles occur on the transfer paper, and conversely, the thickness of the core metal is smaller than the above range. If it is large, the rise of fixing is delayed.
The pressure roller 13 has a diameter of 30 mm, a rubber thickness of 5.5 mm, a rubber length of 316 mm, and is a sponge type or a non-sponge solid type. . The fixing roller 12 was made of an aluminum alloy (A5052 or 3000 series alloy) having an outer diameter of φ30, a thickness t1 = 0.45 mm of the sheet passing portion, a thickness / outer diameter = 15/1000, and a total length of 365 mm. The rib includes an axial (longitudinal) rib 22 and a circumferential rib 23.
In manufacturing, first, the axial rib 22 is first provided. A space (hollow part) 22a is provided inside the axial rib 22 as shown in FIGS. The shape of the rib 22 at this time is 2 to 5 mm in width and 0.5 to 1 mm in height, and the thickness t2 is in the range of 30% to 70% of the thickness t1 of the core metal, that is, 0.15 to 0. .25 mm. A plurality of three to eight axial ribs 22 are arranged at predetermined intervals along the circumferential direction of the inner circumference of the core metal (six positions in the figure), and when the fixing roller core metal 21 is manufactured by extrusion molding. The rib 22 having the space 22a on the inner side is manufactured at the same time. The cored bar 21 is extruded in a cylindrical shape by an extrusion molding machine, and a hollow portion is formed in the rib 22 at that time.
[0008]
Next, after providing the axial ribs 22 by extrusion molding, circumferential ribs 23 are provided on the inner peripheral surface of the core metal. In the manufacture of the circumferential rib 23, a part of the core bar is dented toward the inner diameter side by pressing a jig such as a bite from the outer peripheral surface while rotating the core bar 21 around its axis. Formed by. As a result of indenting a part of the core metal 21, a recess, that is, a groove extending in the circumferential direction is formed on the outer peripheral surface of the core metal. Then, the outer peripheral surface of the core metal is cut until the groove disappears. To smooth the outer peripheral surface. Therefore, the thickness of the core metal at the time of extrusion molding is preliminarily manufactured to be thick assuming the last cutting.
As shown in FIG. 2A, the circumferential ribs 23 are provided at, for example, 3 to 12 locations (9 locations in the figure) in a predetermined arrangement along the axial direction, and the individual ribs 23 as shown in FIG. The width in the circumferential direction is set to 1.5 to 3 mm, and the height is set to 0.3 to 0.8 mm which is 65% to 180% of the core metal thickness t1. At this time, the interval between the ribs 23 gradually decreased as the distance from the center was closer.
The thinner the core roller 21 of the fixing roller, the faster the warm-up time. In other cases, the fixing heater 19 is turned off to achieve energy saving, and when the fixing heater is turned on, it immediately rises and is easy to use.
However, in the case of a thin metal core, without a reinforcing member, the axial deflection at the time of fixing and the crushing caused by contact with the pressure roller are large, and the pressure is easily removed especially near the center in the axial direction, resulting in poor fixing. As described above, there is a problem that the transfer paper tends to be wrinkled and wrinkles of the transfer paper are likely to occur. Therefore, by providing and reinforcing the axial rib 22 and the circumferential rib 23, a fixing device that suppresses bending and crushing while keeping the features of fast warm-up time and is free from defects such as fixing failure and wrinkle generation. Can be provided.
However, when the ribs 22 and 23 extending in the axial direction and the circumferential direction are densely configured, the dimensional accuracy of the outer peripheral surface of the cored bar 21 varies at the intersection where the ribs 22 and 23 intersect. easy. In other words, when no space is provided in the axial rib 22 as in the present invention, when the circumferential rib 23 is being manufactured (pressed with a jig from the outer peripheral surface side of the core metal, When the rib 23 is protruded), the cored bar is deformed at a portion crossing the axial rib 22, and the accuracy of the outer dimension of the cored bar 21 is deteriorated, thereby causing wrinkles on the transfer paper at the time of fixing. Resulting in. In the present invention, since the space 22a is provided inside the axial rib 22 provided earlier to form a hollow structure, the portion (intersection) that crosses when the circumferential rib 23 is provided is shown in FIG. ), The space portion is crushed and deformed, and the accuracy of the outer dimensions can be improved. That is, it is possible to prevent the dimensional accuracy of the outer peripheral surface of the cored bar from deteriorating due to the space 22a in the rib 22 being crushed by exhibiting a buffering effect.
[0009]
Since the thickness t2 of the space 22a of the axial rib 22 is 70% or less of the thickness t1 of the core metal, when the circumferential rib 23 is provided, as shown in FIG. It becomes easy to deform at the intersection, and it becomes easier to secure the outer diameter accuracy of the roller. Further, if the thickness t2 of the rib hollow portion is too thin, the deflection becomes large and wrinkles are generated at the time of fixing. Therefore, the thickness of t2 is set to 30% or more of t1 so that the effective deflection can be suppressed. It was made thick.
In addition, since the thin-walled configuration is adopted as described above, when the heater 19 having an output of 700 W to 800 W is used, the fixing rising time can be extremely shortened to 10 to 15 seconds.
The shape of the space 22a inside the rib 22 does not have to be a semicircular shape, and the shape of the space inside the axial rib 22 may be circular as shown in FIG. 3, for example. Even if the rib 22 has such a space, the same effect as the rib 22 having the semicircular space shown in the example of FIG. 1 can be obtained.
[0010]
【The invention's effect】
As described above, according to the first aspect of the present invention, in the fixing device including the fixing roller composed of a thin cored bar, the strength of the cored bar is increased without using a special reinforcing member, and the bent or crushed In order to prevent fixing defects and fixing roller damage, when the ribs extending in the axial direction and circumferential direction are integrally formed on the inner surface of the cored bar, the accuracy of the external dimensions that are likely to occur at the intersection of the ribs A decrease can be prevented. That is, if both the axial rib and the circumferential rib are in a solid state with no space, the outer diameter of the roller cannot be accurately determined due to the intersection of the ribs, and the transfer paper is not fixed during fixing. Although there is a problem that wrinkles occur, according to the present invention, there is a hollow portion in the previously formed axial rib, so that when the circumferential rib is formed later, the hollow portion becomes a buffer portion. Thus, deformation of the outer peripheral surface of the cored bar can be mitigated. In the invention of claim 2, since the thickness of the rib of the hollow structure is 30% to 70% of the thickness of the cored bar, the dimensional accuracy of the fixing roller can be ensured well, and an unfixed image can be secured. This suppresses the deflection of the roller during fixing, preventing wrinkles and fixing defects. Since the invention of claim 3 is an image forming apparatus provided with the fixing roller manufactured by the method of manufacturing the fixing roller according to claim 1 or 2, the effects of claims 1 and 2 are provided. An image forming apparatus can be provided.
[Brief description of the drawings]
FIGS. 1A and 1B are an overall schematic view of an image forming apparatus using a fixing device of the present invention, and a configuration explanatory diagram of the fixing device.
FIGS. 2 (a), (b), (c), (d), and (e) are a front view of a fixing roller according to the present invention, a cross-sectional view thereof (circumferential rib), and a cross-sectional view taken along a line AA (not shown) Crossing part), its principal part expanded sectional view, and the enlarged sectional view of a crossing part.
FIG. 3 is a cross-sectional view of an axial rib according to another embodiment of the present invention.
FIG. 4 is a diagram showing an example of a fixing roller support structure according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Printer, 2 belt-shaped photoreceptor, 3 Charger charger, 4 Laser optical system, 5 Developing apparatus, 6 Transfer charger, 7 Cleaning apparatus, 10 Fixing apparatus, 12 Fixing roller, 13 Pressure roller, 14 Cleaning pad, 19 Heat source, 21 cored bar, 22 axial rib, 22a space, 23 circumferential rib.

Claims (3)

A fixing device, comprising: a fixing roller having a thin cylindrical cored bar having a heat source therein and rotatably supported; and a pressure roller in contact with an outer peripheral surface of the fixing roller, wherein the core In the fixing roller manufacturing method for manufacturing the fixing roller in which a plurality of ribs extending in the axial direction and the circumferential direction are formed on the inner peripheral surface of the gold,
A fixing roller manufacturing method , wherein the rib extending in the axial direction is formed in a hollow structure , and thereafter the rib extending in the circumferential direction is formed in a solid structure . 2. The fixing roller manufacturing method according to claim 1, wherein a thickness of the hollow rib is 30% to 70% of a thickness of the cored bar. An image forming apparatus comprising: a fixing roller manufactured by the fixing roller manufacturing method according to claim 1.

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