JP2004038037A - Fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make a fixing device for use in a full-color image forming device superior in maintainability and recyclability and advantageous in respect to cost and to considerably reduce wear of a fixing roll. <P>SOLUTION: A pressing roll 20 for giving a prescribed pressing force is arranged in contact with a fixing roll 10, and a recording medium is caused to pass between the fixing roll and the pressing roll to fix a color toner image on the recording medium. An oil coating roll has an oil holding member 32 which has dimethyl silicone oil and a gellant mixed at a prescribed compounding ratio and is provided with a three-dimensional mesh structure and a porous polytetrafluoroethylene layer 33 formed on the surface of the oil holding member. The compounding ratio of dimethyl silicone oil and the gellant is set to 30 to 50%. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fixing device used for fixing a toner image on a recording medium such as recording paper in an image forming apparatus using an electrophotographic method.
[0002]
[Prior art]
Generally, as an image forming apparatus using an electrophotographic method, for example, a printer, a copying machine, a facsimile, and the like are known. In this type of image forming apparatus, a photoconductor as an image carrier is used in accordance with image information. After exposing a photosensitive drum (for example, a photosensitive drum) to form an electrostatic latent image on the photosensitive drum, the electrostatic latent image is developed by a developing device to form a toner image. Then, the toner image is transferred to a recording medium such as recording paper, and the toner image on the recording medium is fixed by a fixing device.
[0003]
The fixing device is provided with a fixing roller for fixing the toner image. In order to prevent a phenomenon that the toner on the recording medium is transferred to the surface of the fixing roller during fixing (a so-called offset phenomenon), A so-called release oil is supplied to the fixing roller. Particularly, in a full-color image forming apparatus, that is, when a full-color image is handled, a large amount of release material such as release oil is required because a large amount of toner adheres to a recording medium.
[0004]
Conventionally, when supplying release oil to the fixing roller, an oil application roller or a cleaning web roller has been used, and among these, the oil application roller uses an oil application roller for the fixing roller to be applied with oil. It is rotated while being in contact with the fixing roller to apply release oil to the fixing roller.
[0005]
However, in the oil application roller, even if the supply amount of the release oil is increased at first, the supply amount of the release oil is increased only in the initial period of the continuous printing operation. Since the amount decreases, it is difficult to stably supply the release oil to the fixing roller. Further, if the interval (time) from the end of printing to the next printing is long, the release oil leaks and seeps out, and as a result, a large amount of release oil is deposited on the leading end of the recording medium. , And image defects may occur. Therefore, the supply amount of the release oil varies depending on the printing situation (whether continuous printing or sporadic printing), and it is difficult to supply the release oil stably. Further, the service life of the oil application roller greatly differs depending on the use condition of the image forming apparatus, that is, the fixing device.
[0006]
In order to prevent such a problem, for example, an oil application roller in which a porous PTFE (polytetrafluoroethylene) layer having pores filled with gelled silicon is arranged on the surface of an oil holding material impregnated with release oil is used. There is also known an oil application roller in which a ceramic member and a felt layer are provided on an oil holding member, and a porous PTFE layer is disposed on the surface thereof (for example, JP-A-2001-318550).
[0007]
By the way, in the above-described oil application roller, porous PTFE is disposed on the surface of the oil retaining material, and the porous PTFE is inferior in air permeability, so that the oil application roller comes into contact with the fixing roller and is heated. In this case, the water contained in the release oil may expand, and the oil application roller may burst. In order to prevent such a rupture, if the water in the release oil is removed, the release oil is consumed and the amount of the release oil decreases. Another disadvantage is that the temperature decreases. In order to prevent such a problem, for example, there is known an oil application roller having a ventilation hole for ventilating the inside of the oil application roller and the outside air. However, in such an oil application roller, if the oil application roller is tilted so that the air hole formed in the oil application roller is downward, the release oil leaks from the air hole, resulting in poor handling. . Therefore, there is an oil application roller provided with a sealing member so that the release oil does not easily pass through the ventilation hole.
[0008]
Even in the above-described oil application roller, if the amount of the release oil applied is large, for example, if the interval between the end of printing and the next print is long, the release oil seeps out. For this reason, a mechanism for retracting the oil application roller from the fixing roller during the print standby is required.
[0009]
In addition, even if the amount of toner on the recording medium is small, if the toner is transferred to the surface of the fixing roller, the toner is reversely transferred to the oil application roller, and the outermost porous PTFE layer is clogged. When the clogging occurs, the release oil supply amount decreases, and the toner is offset to the surface of the fixing roller. In the worst case, a problem such as the recording medium being wound around the fixing roller occurs. Will be. In order to prevent such a problem, for example, a cleaning roller is brought into contact with an oil application roller to prevent clogging with toner.
[0010]
As described above, in the conventional fixing device, it is necessary not only to take various measures on the oil application roller itself, but also to provide a retracting mechanism for the cleaning roller and the oil application roller. Costs will increase. That is, the cost per print becomes high. Further, there is a problem in how to treat the oil application roller which has reached the end of its life, such as disposal or recycling. In particular, in a full-color image forming apparatus, it is necessary to simplify the maintenance of the release oil supply mechanism (oil application roller), recycle problems, improve stickiness due to release oil, and reduce costs.
[0011]
That is, in the full-color image forming apparatus, since the four-color toner images are superimposed to form a full-color image, not only the toner layer on the recording medium is thickened, but also the number of photographic images and the like is increased and the printing rate is increased. Furthermore, in order to ensure the transparency of OHP, it is necessary to make the binder of the toner easy to dissolve (a very wide non-offset area is required for the toner). For this reason, in a full-color image forming apparatus, a toner containing a release agent (wax: usually 5 to 10%) in the toner itself is used. Such a toner is manufactured by a so-called pulverization method or a polymerization method.
[0012]
In the pulverization method, the materials constituting the toner are mixed uniformly by stirring with a mixer, and the uniformly mixed materials are further kneaded (melt kneaded) by applying heat and pressure using a kneader, and then air-flow type. Alternatively, the toner is pulverized mechanically to obtain toner (hereinafter, this toner is referred to as pulverized toner). In such a pulverization method, when a large amount of a release agent (wax) is added to the toner, the dispersibility of the release agent is deteriorated, and toner cracks occur at the interface between the resin (binder) and the release agent. , The durability may be reduced.
[0013]
In order to prevent such inconveniences, in the polymerization method, at the time of polymer production, pigments and various chemicals are charged together with raw materials for the polymer to produce a polymer, and the polymer is used as a toner (hereinafter, this toner is referred to as a polymerized toner ( Polymer toner)). As described above, when producing the polymerized toner, the kneading, pulverizing, and classifying steps which require large energy are not required. In the case of the polymerized toner, the manufacturing process is simple, so that the toner can be manufactured at a low cost and fine particles can be easily manufactured. In addition, each particle diameter and composition of the toner are uniform, and the printing performance is excellent. ing. Furthermore, the polymerized toner has a high fluidity even with a small particle size (because of its round shape), and can greatly reduce the driving torque of the developing device. As a result, not only can the drive unit be reduced in size, but also the transferability can be increased, and high image quality can be realized. In addition, the capsule technology makes it possible to lower the fixing temperature by about 30 ° C. as compared with the conventional pulverized styrene / acrylic acid ester-based copolymer toner, so that the energy for printing can be reduced.
[0014]
By using the polymerized toner as described above, in the full-color image forming apparatus, the simplification of maintenance and the problem of recycling, the stickiness of the image, and the cost reduction can be achieved.
[0015]
[Problems to be solved by the invention]
By the way, in a fixing roller used in an image forming apparatus, in particular, a full-color image forming apparatus, in order to improve durability and prevent toner transfer (so-called offset), a fluorine-based resin layer (for example, 10 to 50 μm) or a fluorine-based tube (for example, 30 to 50 μm in thickness) to improve heat conduction.
[0016]
However, when the frequency of use of these fluorine-based resin layers and fluorine-based tubes increases, the flatness of the surface of the fixing roller deteriorates due to the microslip phenomenon that occurs at the nip portion of the fixing roller. There is. Furthermore, a local abrasion may occur on the fixing roller due to a thermistor and a separation claw that are in contact with the surface of the fixing roller. In addition, the surface of the fixing roller may be damaged by the edge of the recording medium. There is.
[0017]
SUMMARY OF THE INVENTION It is an object of the present invention to provide a fixing device used in an image forming apparatus, which is excellent in terms of maintainability, recyclability, and cost, and has very little wear of a fixing roller.
[0018]
[Means for Solving the Problems]
According to the present invention, it is used when fixing the toner image transferred onto the recording medium to the recording medium, and includes a fixing roller and a pressing roller that contacts the fixing roller and applies a predetermined pressing force. In the fixing device, the recording medium is inserted into a nip portion between the fixing roller and the pressing roller so that the toner image is fixed on the recording medium. Comprising an oil holding member having a three-dimensional network structure and a porous resin layer formed on the surface of the oil holding member, wherein the oil applying roller is the fixing roller and the pressing roller At least one of which is rotatably abutted together with the roller.
[0019]
Thus, as an oil application roller, an oil holding member having a three-dimensional network structure in which dimethyl silicone oil and a gelling agent are mixed at a predetermined mixing ratio, and an oil holding member formed on the surface of the oil holding member, for example, When an oil application roller having a porous resin layer such as a porous polytetrafluoroethylene layer is used, the flatness of the fixing roller can be maintained and local wear can be prevented. Further, a cleaning roller is not required, and not only the maintainability and the recyclability are improved, but also the local wear is small, so that the life of the fixing roller is extended and the cost is advantageous.
[0020]
In the present invention, a toner or a polymer toner to which a release agent is added is used as the toner used when forming the toner image. If the above-described oil application roller is further provided using such a toner, the fixing property can be made extremely good.
[0021]
In the present invention, the silicone oil is dimethyl silicone oil, and the compounding ratio of the dimethyl silicone oil and the gelling agent is in the range of 30 to 50%. When the compounding ratio is in this range, not only can the release oil be satisfactorily held, but also a small amount of release oil can be stably supplied to the fixing roller.
[0022]
In the present invention, the porous resin layer is a porous polytetrafluoroethylene layer, and the porous polytetrafluoroethylene layer has a continuous portion having a fiber and a spherical nodule and a void portion surrounded by the fiber and the spherical nodule. It is a porous body. If such a continuous porous body is used, a trace amount of release oil can be uniformly supplied over a long period of time.
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention but to the description examples unless otherwise specified. Only.
[0024]
Referring to FIG. 1, the illustrated fixing device is used in a full-color image forming apparatus (hereinafter, simply referred to as an image forming apparatus), and is mounted on a recording medium (recording paper) onto which a color toner image (four-color toner image) is transferred. The color toner image is fixed (the recording medium is inserted between the fixing roller and the pressing roller described later, and the toner image is fixed on the recording medium). Here, the above-mentioned pulverized toner (toner containing a release agent (wax)) or polymer toner is used as the toner.
[0025]
The illustrated fixing device includes a fixing roller 10, and the fixing roller 10 includes, for example, a heater. That is, the fixing roller 10 is a heat roller. A pressing roller 20 is disposed in contact with (in contact with) the fixing roller 10, and the pressing roller 20 includes, for example, a heater. Further, an oil application roller 30 is disposed in contact with the fixing roller 10. A fixing roller temperature control thermistor 40 is arranged in contact with the fixing roller 10, and the surface temperature of the fixing roller 10 is controlled by the thermistor 40. Similarly, a thermistor 41 for controlling the temperature of the pressing roller is arranged in contact with the pressing roller 20, and the surface temperature of the pressing roller 20 is controlled by the thermistor 41. As shown, a pressing roller separating claw 50 is arranged, and the pressing roller 20 is separated from the fixing roller 10 by the pressing roller separating claw 50.
[0026]
The fixing roller 10 includes, for example, the aluminum tube 12 having a diameter of 36 mm and a thickness of 1.5 mm in which the heater 11 (for example, 450 W) is built as described above. A 1.5 mm thick silicon rubber layer (JIS rubber hardness A0 degree) 13 is formed on the surface of the aluminum pipe 12. Further, on the silicon rubber layer 13, a 30 μm thick fluorine resin layer ( For example, a PFA coat or a PFA tube (here, a PFA tube is used) 14 is formed.
[0027]
On the other hand, as described above, the pressing roller 20 incorporates the heater 21 (for example, 350 W) and has, for example, an aluminum tube 22 having a diameter of 36 mm and a wall thickness of 1.5 mm. A 1.5 mm thick silicone rubber layer (JIS rubber hardness A10 degree) 23 is formed on the surface of the aluminum tube 22. Further, a 30 μm thick fluororesin layer (for example, PFA) is formed as the outermost layer. A coat or a PFA tube (here, a PFA tube is used) 24 is formed. Here, the pressing width (nip width) between the fixing roller 10 and the pressing roller 20 was 5.5 mm.
[0028]
Here, the oil application roller 30 will be described with reference to FIG. The oil application roller 30 has, for example, a metal shaft 31 having a diameter of 6 mm, and an oil holding layer 32 having a diameter of about 15 mm is arranged concentrically with the metal shaft 31. The oil holding layer 32 has a three-dimensional network structure in which dimethyl silicone oil and a gelling agent are blended (the blending ratio is 30 to 50%), and has a three-dimensional network structure. ). On the surface of the oil holding layer 32, a Gore-Tex (trade name) film 33 is provided, which is made of PTFE (polytetrafluoroethylene) by a special processing and has a continuous porous body. The Gore-Tex film 33 is a continuous porous body of PTFE including fibrils (fibers), nodes (spherical nodules), and pores surrounded by these. Although not shown, both ends of the oil application roller 30 are sealed so that oil does not leak.
[0029]
Here, the oil application roller 30 is pressed against the fixing roller 10 with a load of 500 gf (one side) so that the application amount of the release oil is 0.1 to 0.01 mg per sheet for an A4 size recording medium. I made it. The oil application roller 30 is rotatably supported by a frame of the fixing device. That is, bearings (not shown) are arranged at both ends of the oil application roller 30, and the oil application roller 30 is brought into contact with the fixing roller 10 as described above, and is driven in accordance with the rotation of the fixing roller 10. It is possible (it may be configured as a unit to make it detachable).
[0030]
Here, as described above, the diameter of the metal shaft 31 is 6 mm, the diameter of the gelling oil holding layer 32 is 15 mm, and the mixing ratio of dimethyl silicone oil (100 CS: filled with about 27 g) and the gelling agent is about 5: 5. The oil application roller 30 was pressed against the fixing roller 10 having a PFA tube (thickness: 30 μm) at the outermost layer with a load of 500 gf (one side), and the printing ratio of A4 size recording paper was 5%. %, 300,000 sheets (300k sheets) intermittent printing (8,000 sheets / day at 10 sheets / minute) (full color image printing), and the wear of the fixing roller 10 was evaluated.
[0031]
In the abrasion evaluation described above, the amount of oil applied was 0.1 mg / A4 size at the initial stage, and was 0.02 mg / A4 size after printing about 40 k sheets. From then on, up to 300k sheets, the amount of oil applied was 0.01 mg / A4 size and was stable. Even when a full-color image was printed in a state where the maximum oil application amount was 0.1 mg / A4 size (initial state), no stain image was generated on the recording paper by the oil.
[0032]
The outer diameter of the oil applying roller 30 was initially 14.7 mm, and after printing 300 k sheets, the outer diameter of the oil applying roller 30 was 14.2 mm (outer diameter change rate Δ = 3.4). %). And the oil consumption was 4.01 g. After printing 300k sheets, the appearance of the oil application roller 30 was checked. As a result, no toner adhesion was observed, and it was found that the cleaning roller for the oil application roller 30 was unnecessary.
[0033]
Further, with respect to the wear evaluation, the abrasion of the surface of the fixing roller 10 contacted by the thermistor 40 in contact with the surface of the fixing roller 10 was evaluated. When 300 k sheets were printed as described above using the fixing device to which the oil application roller 30 was not attached, the fixing roller 10 was worn by 12 μm at the contact portion. On the other hand, when the above-described oil application roller 30 was mounted, the fixing roller 10 was worn by 5.8 μm at the contact portion in a state where 300 k sheets were printed. That is, depending on the presence or absence of the oil application roller 30, there is a wear difference of 6.8 μm at the contact portion of the thermistor 40 after printing 300k sheets. Thus, it can be understood that the wearing of the oil application roller 30 can prevent the wear at the contact portion.
[0034]
As described above, in the oil application roller 30, the oil holding layer 32 has a three-dimensional network structure, and the network structure contains release oil. That is, the oil holding layer 32 is in an intermediate state between a solid and a liquid. For this reason, for example, regarding the problem that the oil application roller is tilted (or the oil application roller is in an upright state) at the time of storage or transportation and the release oil leaks from the roller end, it is difficult to improve the air permeability. Even if a high quality PTFE layer is used, there is no problem since the roller end has a two-layer structure (gelling layer + PTFE layer), and as a result, there is no need to provide ventilation holes.
[0035]
As described above, the oil holding layer is formed by mixing dimethyl silicone oil and a gelling agent to form a three-dimensional network structure, and porous PTFE (polytetrafluoroethylene) is provided on the surface of the oil holding layer. In this case, the flatness of the fixing roller can be maintained and local wear can be prevented.
[0036]
Further, a cleaning roller is not required, and not only the maintainability and the recyclability are improved, but also the local wear is small, so that the life of the fixing roller is extended and the cost is advantageous. At this time, if the compounding ratio of dimethyl silicone oil and the gelling agent is 30 to 50%, not only can the release oil be maintained well, but also a small amount of release oil can be stably supplied to the fixing roller. I knew I could do it.
[0037]
Further, it was found that when a toner or a polymer toner to which a release agent was added was used as a toner used when forming a color toner image, fixability could be extremely improved. If a continuous porous body (Gore-Tex (trade name) membrane) having voids surrounded by fibers and spherical nodules and between fibers and spherical nodules is used as the porous polytetrafluoroethylene layer, a trace amount can be obtained over a long period of time. Can be uniformly supplied.
[0038]
In the above-described example, the example in which the oil application roller 30 is brought into contact with the fixing roller 10 to rotate the fixing roller 10 and the oil application roller 30 has been described, but the oil application roller 30 is brought into contact with the pressing roller 20. Alternatively, the oil application roller 30 may be brought into contact with both the fixing roller 10 and the pressing roller 20.
[0039]
【The invention's effect】
As described above, according to the present invention, as the oil application roller, an oil holding member having a three-dimensional network structure in which dimethyl silicone oil and a gelling agent are mixed at a predetermined mixing ratio, and formed on the surface of the oil holding member. Since the roller having the porous polytetrafluoroethylene layer is used, there is an effect that the flatness of the fixing roller can be maintained and local wear can be prevented. Further, the cleaning roller is not required, so that not only the maintainability and the recyclability are improved, but also because the local wear is small, the service life of the fixing roller is prolonged, which is advantageous in terms of cost. Even when a monochrome image is handled, the offset can be effectively reduced if high-density printing such as a photograph or image is performed by a high-speed machine (for example, the number of prints per minute is 50 or more). Can be prevented.
[0040]
In the present invention, since a toner or a polymer toner to which a release agent is added is used as the toner used when forming a color toner image, there is an effect that the fixability can be extremely improved.
[0041]
In the present invention, since the compounding ratio of dimethyl silicone oil and the gelling agent is in the range of 30 to 50%, not only the release oil can be favorably held, but also a small amount of the release oil can be stably fixed. There is an effect that can be supplied to.
[0042]
In the present invention, as the porous polytetrafluoroethylene layer, a continuous porous body having voids surrounded by fibers and spherical nodules and fibers and spherical nodules is used, so that a minute amount of mold release over a long period of time There is an effect that oil can be supplied uniformly.
[Brief description of the drawings]
FIG. 1 is a sectional view showing an example of a fixing device according to the present invention.
FIG. 2 is a perspective view showing the oil application roller shown in FIG. 1 with a part cut away.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Fixing roller 11, 21 Heater 12, 22 Aluminum pipe 13, 23 Silicon rubber layer 14, 24 Fluororesin layer 20 Press roller 30 Oil application roller 31 Metal shaft 32 Oil holding layer 33 Continuous porous body (porous polytetrafluoro Ethylene layer)
40, 41 Thermistor 50 Press roller separation claw

Claims (4)

Used when fixing the toner image transferred on the recording medium to the recording medium, has a fixing roller, a pressing roller that applies a predetermined pressing force by contacting the fixing roller, the fixing roller In a fixing device configured to fix the toner image on the recording medium by inserting the recording medium through a nip portion between the pressing roller and the recording medium, the silicone oil and the gelling agent are mixed at a predetermined mixing ratio, and the three-dimensional image is formed. An oil applying roller having an oil holding member having a mesh structure and a porous resin layer formed on the surface of the oil holding member, wherein the oil applying roller is provided on at least one of the fixing roller and the pressing roller. A fixing device rotatably contacted with the fixing device. The fixing device according to claim 1, wherein a toner or a polymer toner to which a release agent is added is used as the toner used when forming the toner image. The fixing device according to claim 1, wherein the silicone oil is dimethyl silicone oil, and a compounding ratio of the dimethyl silicone oil and the gelling agent is in a range of 30% to 50%. The porous resin layer is a porous polytetrafluoroethylene layer, and the porous polytetrafluoroethylene layer is a continuous porous body having a fiber and a spherical nodule and a void surrounded by the fiber and the spherical nodule. The fixing device according to claim 1, wherein:

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