JP4275328B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fixing device and an image forming apparatus using a sheet-like member in place of a pressure roller in a copying machine, a printer, a facsimile machine using these electrophotographic methods, and a multifunction machine having these functions.
[0002]
[Prior art]
A conventional fixing device of this type is configured as shown in FIG. As shown in FIG. 6, the fixing device includes a heat fixing roller 1 provided with a heater 2 that is provided inside and a heater 2, and a pressure fixing roller 3 that is in pressure contact with the heat fixing roller 1. In addition, the fixing device includes temperature detecting means 4 for detecting the surface temperature of the heat fixing roller 1 heated by the heater 2, a guide plate 5 for guiding the paper between the heat fixing roller 1 and the pressure fixing roller 3, and heat fixing. A separation claw 6 that separates the paper wound around the roller 1 from the heat fixing roller 1, a conveyance roller pair 7 provided on the paper exit side of the fixing device, and the like.
[0003]
The sheet on which the toner image is transferred is conveyed to the nip portion between the heat fixing roller 1 and the pressure fixing roller 3 through the guide plate 5 to the fixing device. After the toner image is fixed on the sheet by being pressurized / heated at the nip portion, the sheet is discharged to the outside through the conveying roller pair 7. Note that the toner adhering to the heat fixing roller 1 when the sheet passes through the nip portion is removed by a cleaning pad (not shown).
[0004]
The surface temperature of the heat fixing roller 1 is detected by the temperature detection means 4, and based on the detection result of the temperature detection means 4, the heating control by the heater 2 is performed by the control means.
[0005]
Conventionally, the fixing device employs an infrared heater or a halogen heater as a heater, and is constituted by a pair of rollers including a heat fixing roller 1 and a pressure fixing roller 3. However, the pressure fixing roller has a structure in which a silicon rubber layer is formed on a cored bar and a release layer such as a Teflon (registered trademark) tube is formed thereon, so that the heat capacity is large. Even when heating is started by this, the pressure fixing roller 3 side does not warm easily, and this tendency becomes more prominent due to control in consideration of energy saving in recent years, which causes a fixing defect. In addition, there was a demerit that the parts cost was high.
[0006]
Further, in order to ensure an appropriate nip width at the nip portion between the heat fixing roller 1 and the pressure fixing roller 3, a large pressure is required, and the pressure causes stress on the paper, which causes fixing wrinkles. Therefore, a nip portion is formed by pressing a sheet-like pressure member against the heat fixing roller instead of the pressure fixing roller 3, and the image is fixed to the paper by passing the paper through the nip portion. Fixing devices have been devised. Since the fixing device having this configuration is a sheet-like member, it can be easily warmed and a nip width can be secured.
[0007]
[Problems to be solved by the invention]
However, in the pressure member using the sheet-shaped member having such a configuration, in order to pressurize the heat fixing roller, for example, the sheet-shaped member is pressed against the heat fixing roller from the back surface side by a pressure spring. It is conceivable to secure the applied pressure. In this case, since the sheet-like member moves up and down according to the thickness of the sheet and the nip width varies, the types of sheets that can be printed are limited.
[0008]
The present invention is directed to solving the problems of the prior art, and provides a fixing device and an image forming apparatus capable of obtaining a stable nip width even when the thickness of a sheet to be printed changes. The purpose is to do.
[0009]
[Means for Solving the Problems]
In order to achieve this object, the invention according to claim 1 is a fixing device that converts a latent image formed on a photoconductor into a toner image and transfers the toner image onto a sheet, and fixes the transferred toner image. A fixing roller that rotates with a heating unit; a sheet-like member that forms a nip portion in contact with the fixing roller; a sheet support material that cantilever-supports the sheet-like member; and a free end of the sheet-like member And a relief regulating member that regulates the position of the free end of the sheet-like member so that the sheet does not fall below a predetermined position, and allows the sheet to pass through the nip portion between the fixing roller and the sheet-like member while heating / pressing the sheet. bearing having the constant Chakusochi where Ru is fixing the toner image to the sheet, and an eccentric roller provided the rotary shaft of the polygonal prism preventing member escape eccentric, a recess adapted to the rotary shaft to the rotary shaft Te Supporting said rotary shaft is rotated by rotating the eccentric roller in conjunction with the rotary shaft, and adjusting the vertical position of the sheet-like member. By having such a configuration, when the sheet passes through the nip portion, the position of the free end of the sheet-shaped member may fall more than necessary is prevented by the eccentric roller, the sheet-like member by further rotation of the eccentric roller The free end of the nip can be moved up and down to adjust the nip width , and the nip width can be secured. In addition, the polygonal column-shaped rotation shaft of the eccentric roller fits into the recess, so that the rotation of the eccentric roller is restricted, the free end of the sheet-like member is stabilized, and a click feeling when operating the rotation shaft manually. It becomes possible to give.
[0013]
According to the invention of claim 2, and characterized in the invention according to claim 1, before Symbol rotation axis, in that a dial member displaying an indication of the rotational position corresponding to the vertical position of the sheet-like member To do. With this configuration, the position of the sheet-like member can be notified, and information for adjusting the nip width can be given to the user.
[0014]
According to a third aspect of the present invention, in the second aspect of the present invention, the index is a sheet thickness corresponding to the vertical position of the sheet-like member. With this configuration, a nip width corresponding to the sheet thickness can be obtained.
[0015]
According to the invention according to claim 4 , in the invention according to any one of claims 1 to 3 , the holding means for holding the fixing roller movably in the contact and separation direction with respect to the sheet-like member; And pressurizing means for urging the fixing roller in a direction in which the fixing roller is brought into contact with the sheet-like member. With this configuration, the nip pressure can be lowered by moving the fixing roller, and the processing when a paper jam occurs in the nip portion is facilitated.
[0016]
According to a fifth aspect of the present invention, in the invention according to the fourth aspect , the holding unit includes a bearing portion that rotatably holds the fixing roller, and the fixing unit is configured to be fixed by the pressing unit via the bearing unit. The roller is biased in a direction in which the roller abuts on the sheet-like member. With this configuration, the urging force of the pressing unit can be directly applied to the fixing roller.
[0017]
According to the invention according to claim 6 , in the invention according to claim 4 or 5 , a rotation shaft is provided in a portion other than the central axis of the fixing roller in the holding means, and the holding means is set around the rotation shaft. Is supported in a rotatable manner. With this configuration, the fixing roller can be moved toward and away from the sheet-like member.
[0018]
According to the invention of claim 7 , in the inventions of claims 4 to 6 , any one of a contact position where the fixing roller contacts the sheet-like member or a separation position where the fixing roller is separated from the sheet-like member. The holding means is provided with an engaging portion that engages with the moving means. With this configuration, the fixing roller can be moved toward and away from the sheet-like member by operating the moving unit.
[0021]
According to an eighth aspect of the present invention, an electrophotographic image forming apparatus has the fixing device according to any one of the first to seventh aspects. With such a configuration, it is possible to reduce the size and cost of the image forming apparatus as the fixing device is reduced in size and cost by using the sheet-like member. Further, the fixing operation can be performed stably.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Here, a facsimile machine is taken as an example of the image forming apparatus in the present embodiment.
[0023]
FIG. 1 is a sectional view showing a schematic configuration of a facsimile apparatus according to an embodiment of the present invention. In the facsimile apparatus (apparatus body 10) shown in FIG. 1, a latent image is formed on the photosensitive member 12 by the optical writing device 11 that scans the laser light L modulated based on the image data. The process cartridge 13 includes a photosensitive member 12 therein, and houses various process apparatuses for forming an image by an electrophotographic method, and is configured to be detachable from the apparatus main body 10. The toner image formed on the photosensitive member 12 is transferred onto the sheet by the transfer roller 16 in contact with the photosensitive member 12 on the sheet housed in the sheet feeding cassette 14 and fed and conveyed by the feeding roller 15 and the like. The toner image transferred onto the paper is fixed by passing through the fixing device 20 and conveyed to the paper discharge tray 18 by the conveying roller pair 17.
[0024]
The document set on the document table is discharged to the outside by passing through the contact sensor 19 by the transport system. At this time, the image of the original is optically read by the contact sensor 19 when passing through the contact sensor 19. The image data read by the contact sensor 19 is transmitted and output to the outside. Further, image data received and input from the outside or image data read by the contact sensor 19 is sent to the optical writing device 11.
[0025]
In the optical writing device 11, the surface of the photoconductor 12 is irradiated with laser light L modulated based on image data, and an electrostatic latent image is formed on the surface of the photoconductor 12. A toner image is formed by attaching toner to the electrostatic latent image, and the toner image is transferred onto a sheet by a transfer roller. Then, the toner image is fixed on the paper by being pressurized / heated by the fixing device 20, and is discharged to the outside by the conveying roller pair 17.
[0026]
2 is a side view showing a schematic configuration of the fixing device included in the facsimile apparatus in FIG. 1. FIG. 2 (a) is a contact position of the fixing roller with a sheet-like member, and FIG. 2 (b) is a separated position. State.
[0027]
In FIG. 2, 21 is a fixing roller, 22 is a heater, 23 is a sheet-like member serving as a pressure member, and 24 is a holding means for holding the fixing roller 21 by a bearing portion 24a, and rotates about a shaft 24b as a support shaft. A possible housing 25 is a transmission gear for transmitting a driving force from a driving means (not shown) for rotationally driving the fixing roller 21, and 26 is provided between the housing 24 and the housing, and the fixing roller 21 is a sheet-like member. A pressurizing means for urging the sheet member 23, a sheet support member 27 for supporting the sheet member 23, and a stopper member 28 for the sheet member 23 attached to the support member.
[0028]
Reference numeral 29 denotes a moving unit that moves the fixing roller 21 to a contact position where a nip portion is formed between the sheet-like members 23 and a separation position where the fixing roller 21 is separated from the sheet-like members 23. One end of the moving means 29 engages with an engaging claw 24c provided in the housing 24, and the other end is a drive unit (not shown) that moves between the contact position and the separation position. Is provided. Further, locking means (not shown) for locking the housing 24 at a position where the one-side pressure at the nip portion is 0.5 to 10 (9.8 N) in the direction in which the housing 24 is urged by the pressing means 26. have.
[0029]
Reference numeral 30 denotes an escape preventing member. The escape prevention member 30 is disposed downstream of the nip portion in the sheet conveyance direction and on the back surface side of the free end portion of the sheet-like member 23. When the fixing roller 21 is moved to the contact position by the moving means 29, the free end of the sheet-like member 23 is lowered by the pressure from the fixing roller 21, as shown in FIG. 30 abuts. That is, the position of the free end of the sheet-like member 23 is regulated by the escape preventing member 30.
[0030]
In the apparatus shown in FIG. 2, the sheet-like member 23 used for the fixing device 20 is made of a heat-resistant resin such as a fluororesin or polyimide having rigidity, a base material having heat resistance and rigidity coated with a fluororesin, and a base. A metal plate may be applied to the material or a metal plate (rigid iron, copper, etc.) may be used. Further, the base material may be configured to contain bubbles in consideration of heat storage properties.
[0031]
The sheet P on which the toner image has been transferred is conveyed to the fixing device 20 and is heated / pressurized at the nip portion between the fixing roller 21 and the sheet-like member 23 to fix the toner image. At this time, the fixing roller 21 is heated to a temperature at which fixing can be performed by the heater 22 of the heating unit, is moved to a contact position with the sheet-like member 23 by the moving unit 29, and is rotated by the driving unit to carry the paper. Has been. The fixing process is performed when the paper P passes through the nip portion.
[0032]
FIG. 3 is a front view showing the configuration of the escape preventing member. Reference numeral 31 denotes an eccentric roller having a rotating shaft 32 at a position deviated from the central axis. The rotating shaft 32 is a quadrangular prism shape with a square bottom surface, and the position of the rotating shaft 32 is set so that one diagonal line of the square on the rotating shaft 32 passes through the center of the eccentric roller 31. Further, bearings 33 and 33 are provided at lower portions on both sides of the free end portion of the sheet-like member 23, and the receiving portion on which the rotary shafts 32 and 32 are placed is formed in a V-shape having an angle of 90 °. Yes.
[0033]
When the eccentric roller 31 is placed on the bearings 33, 33, the free end portion of the sheet-like member 23 comes into contact with the eccentric roller 31.
[0034]
A rotary shaft 32 on one side of the eccentric roller 31 is provided with a dial 34 having the rotary shaft 32 as a central axis. The dial 34 is rotated by the user.
[0035]
When the corner of the rotating shaft 32 close to the central axis of the eccentric roller 31 is in contact with the bearings 33, 33, the sheet-like member 23 is positioned closest to the rotating shaft 32 as shown in FIG. It becomes like this. Then, the dial 34 is rotated by 90 °, the next corner is fitted to the bearings 33, 33, stops with a click feeling, and the sheet-like member 23 is lifted. As a result, the winding angle of the sheet-like member 23 around the fixing roller 21 is increased as compared to before the rotation, and the nip width can be ensured. Further, when the dial 34 is rotated by 90 ° and the next corner portion is fitted to the bearings 33 and 33, the sheet-like member 23 comes to be located at the position farthest from the rotation shaft 32 as shown in FIG. The maximum nip width can be ensured. Thus, the nip width can be switched by operating the dial 34.
[0036]
The dial 34 displays the paper type, environment, and the like so that the user can determine the position at which the corner of the rotary shaft 32 is fitted to the bearings 33, 33. In the present embodiment, for example, the sheet-like member 23 is selected as the lowest position in the case of thick paper, the sheet-like member 23 is selected as the uppermost position in the case of thin paper, and the sheet-like member in the case of plain paper. “Thick paper”, “plain paper”, and “thin paper” are displayed so that 23 is selected as an intermediate position.
[0037]
According to the present embodiment configured as described above, the eccentric roller 31 abuts on the free end portion of the sheet-like member 23, so that the eccentric roller 31 functions as a escape prevention member, and when the sheet passes through the nip portion. The vertical movement of the sheet-like member 23 is restricted, and the nip width can be secured. Further, by rotating the eccentric roller 31, the vertical position of the sheet-like member 23 can be changed, and the nip width can be adjusted by the user's dial operation.
[0038]
In this embodiment, the sheet-like member 23 is moved up and down by the rotation of the eccentric roller 31. However, the present invention is not limited to this. For example, a relief member is provided at the free end of the sheet-like member 23. The escape prevention member may be configured to be slidable in the vertical and horizontal directions to adjust the position.
[0039]
Further, by separating the fixing roller 21 and the sheet-like member 23 by the moving means 29, the nip portion of the sheet-like member 23 that comes into contact with the rotation of the fixing roller 21 on the same surface is worn, and the sheet-like shape The deformation of the member 23 can be reduced.
[0040]
Further, the stopper member 28 provided with a gap on the back side of the sheet-like member 23 prevents the sheet-like member 23 from being deformed, particularly in the nip portion, due to a paper jam or the like occurring in the fixing device. it can. The sheet-like member 23 may be a structural part having a certain degree of heat resistance, such as polycarbonate resin or ABS resin, and is composed of a member used for an apparatus housing, and further formed integrally with a sheet support member 27. This also makes it possible to reduce the number of parts.
[0041]
Further, since the fixing roller 21 can be separated from the sheet-like member 23 by the moving means 29, it is possible to smoothly perform processing such as paper jam occurring at the nip portion. Here, when the fixing roller 21 is separated from the sheet-like member 23, it is possible to move the sheet-like member 23, but in that case, the escape preventing member 30 is retracted to a position where it does not contact the sheet-like member 23. It is necessary to keep it. However, in this embodiment, it is not necessary to provide means for retracting the escape preventing member 30 in order to move the fixing roller 21.
[0042]
【The invention's effect】
As described above, according to the present invention configured as described, when the sheet passes through the nip portion, the position of the free end of the sheet-shaped member may fall more than necessary is prevented by the eccentric roller, the further eccentric roller By rotating, the free end of the sheet-like member can be moved up and down to adjust the nip width , and the nip width can be secured. As a result, it is possible to obtain a stable fixing property. In addition, the polygonal column-shaped rotation shaft of the eccentric roller fits into the recess, so that the rotation of the eccentric roller is restricted, the free end of the sheet-like member is stabilized, and a click feeling when operating the rotation shaft manually. It becomes possible to give.
[Brief description of the drawings]
1 is a cross-sectional view showing a schematic configuration of a facsimile apparatus according to an embodiment of the present invention. FIG. 2 is a schematic configuration of a fixing device included in the facsimile apparatus shown in FIG. 1, and (a) is a sheet-like member of a fixing roller. (B) is a side view showing the state of the separated position. FIG. 3 is a front view showing the configuration of the escape preventing member. FIG. 4 is a side view of FIG. 3. FIG. FIG. 6 is a side view showing a state in which the dial is rotated by 180 °. FIG. 6 is a cross-sectional view showing a schematic configuration of a fixing device included in a conventional facsimile apparatus.
20 fixing device 21 fixing roller 23 sheet-like member 24 housing 24a engaging claw 25 transmission gear 26 pressure means 27 sheet support material 28 stopper member 29 moving means 30 escape preventing member 31 eccentric roller 32 rotating shaft 33 bearing 34 dial

Claims (8)

A latent image formed on a photosensitive member is converted into a toner image and transferred onto a sheet, and the fixing device fixes the transferred toner image,
A fixing roller that rotates with a heating unit; a sheet-like member that forms a nip portion in contact with the fixing roller; a sheet support material that cantilever-supports the sheet-like member; and a free end of the sheet-like member And a relief regulating member that regulates the position of the free end of the sheet-like member so that the sheet does not fall below a predetermined position, and allows the sheet to pass through the nip portion between the fixing roller and the sheet-like member while heating / pressing the sheet. in the constant Chakusochi where Ru is fixing the toner image to the sheet Te,
The escape preventing member is an eccentric roller provided with an eccentric polygonal rotating shaft, and the rotating shaft is supported by a bearing having a recess adapted to the rotating shaft, and the rotating shaft is rotated together with the rotating shaft. A fixing device that adjusts the vertical position of the sheet-like member by rotating the eccentric roller . The fixing device according to claim 1 , wherein a dial member displaying a rotation position index corresponding to the vertical position of the sheet-like member is provided on the rotation shaft . The fixing device according to claim 2 , wherein the index is a sheet thickness corresponding to a vertical position of the sheet-like member . A holding unit that holds the fixing roller so as to be movable in a contact / separation direction with respect to the sheet-like member; and a pressing unit that urges the fixing roller in a direction to contact the sheet-like member. The fixing device according to any one of claims 1 to 3 , wherein the fixing device is characterized in that: The holding means includes the bearing portion that rotatably holds the fixing roller, and the pressing means biases the fixing roller in a direction to contact the sheet-like member via the bearing portion. The fixing device according to claim 4, characterized in that: 6. The fixing according to claim 4 , wherein a rotation shaft is provided at a portion of the holding means other than the central axis of the fixing roller, and the holding means is rotatably supported around the rotation shaft. apparatus. A moving unit that moves the fixing roller to either a contact position that contacts the sheet-like member or a separation position that separates the fixing roller from the sheet-like member; The fixing device according to claim 4 , wherein the fixing device is provided in a holding unit . In an electrophotographic image forming apparatus, the image forming apparatus characterized by having a fixing device according to any one of the claims 1-7.

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