Patent Grant
8688023
The present invention relates to a pressing roller and an image heating device, using the pressing roller, suitable when it is used as a fixing device to be mounted in an image forming apparatus such as an electrophotographic copying machine or an electrophotographic printer.
As the fixing device to be mounted in the electrophotographic copying machine or printer, a film fixing type fixing device has been known. The fixing device of this type includes a heater which includes a ceramic substrate and a heat generating resistor formed on the substrate, a fixing film movable in contact with the heater, and a pressing roller for forming a nip between the pressing roller and the fixing film contacted to the heater. A recording material for carrying an unfixed toner image is heated while being nip-conveyed in the nip of the fixing device, so that the toner image on the recording material is heat-fixed on the recording material. This fixing device has the advantage such that a time (rising time) required from start of energization to the heater until a temperature of the heater is increased up to a fixable temperature is short. Therefore, the printer in which the fixing device is mounted can shorten a time from input of a print instruction to output of an image on a first sheet of the recording material (FPOT: first printout time). Further, the fixing device of this type has also the advantage such that power consumption during stand-by in which the printer awaits the print instruction is decreased.
In the fixing device using the fixing film, in general, the pressing roller is rotated by a driving motor and then the fixing film is rotated by being caused to follow the rotation of this pressing roller. In the printer in which this fixing device is mounted, it has been known that when a small-sized recording material is subjected to continuous printing with the same printing interval as that for a large-sized recording material, an area (non-sheet-passing area) of the heater in which the recording material is not passed is excessively increased in temperature (referred to as non-sheet-passing portion temperature rise). This non-sheet-passing portion temperature rise is more liable to occur with an increase in processing speed (process speed) of the printer. This is because a time when the recording material passes through the nip is decreased with speed-up and therefore a fixing temperature necessary to heat-fix a toner image on the recording material is increased in many cases. Thus, when the non-sheet-passing portion temperature rise occurs, there is a possibility that respective parts constituting the fixing device are damaged. Further, when a large-sized recording material is subjected to printing in a state in which the non-sheet-passing portion temperature rise occurs, the toner is excessively melted at a portion corresponding to the non-sheet-passing area on the recording material to cause high-temperature offset in some cases.
In order to prevent an occurrence of such a problem, as one of means for reducing the degree of the non-sheet-passing portion temperature rise, such a method that a thermal conductivity of the pressing roller with respect to a longitudinal direction is increased has been known. In this method, a heat transfer property of an elastic layer (rubber layer) provided in the pressing roller is aggressively improved to accelerate movement of the heat in the longitudinal direction of the pressing roller, so that the degree of the non-sheet-passing portion temperature rise is alleviated.
Japanese Laid-Open Patent Application (JP-A) 2005-273771 discloses a pressing roller in which pitch-based carbon fibers are dispersed on a metal core. In this pressing roller, the thermal conductivity of the rubber layer is high and therefore the pressing roller is effective in alleviation of the degree of the non-sheet-passing portion temperature rise. JP-A 2009-31772 discloses a pressing roller in which a rubber layer in which pitch-based carbon fibers are dispersed is provided on a solid rubber elastic layer. In this pressing roller, the pitch-based carbon fibers are oriented in the roller longitudinal direction in the rubber layer in which the carbon fibers are dispersed and therefore a property such that the thermal conductivity with respect to particularly the roller longitudinal direction is high (thermal conductivity anisotropy) is exhibited, so that the pressing roller is effective in alleviation of the degree of the non-sheet-passing portion temperature rise.
The pressing roller disclosed in JP-A 2005-273771 is excellent in thermal conductivity of the elastic layer and is effective in alleviating the degree of the non-sheet-passing portion temperature rise but the thermal conductivity with respect to a thickness direction of the rubber layer is also high and therefore the heat is liable to be dissipated into the metal core. For this reason, in a process in which the fixing device at the time of start of the printing is increased in temperature up to a predetermined temperature (hereinafter referred to as during rising), a temperature rising speed of the fixing film surface is less liable to be increased.
In the pressing roller disclosed in JP-A 2009-31772, the rubber layer in which the pitch-based carbon fibers are oriented and dispersed is provided on the solid rubber elastic layer. As a result, the thermal conductivity with respect to the roller longitudinal direction is excellent and is effective in alleviation of the degree of the non-sheet-passing portion temperature rise, and a heat insulating property is also good and therefore the heat is less liable to be dissipated in the rubber layer thickness direction. However, in order to further shorten a time from start of printing until the fixing can be started, a further improvement in heat insulating property with respect to the rubber layer thickness direction is required.
A principal object of the present invention is to provide a pressing roller capable of improving a heat conductive property of an elastic layer with respect to a longitudinal direction of a pressing member and also capable of improving a heat insulating property with respect to a thickness direction of the elastic layer.
Another object of the present invention is to provide an image heating device including the pressing roller.
According to an aspect of the present invention, there is provided a pressing roller comprising:
a metal core; and
an elastic layer containing a needle-like filler or whisker which has an average length of 0.05 mm or more and 1 mm or less and a thermal conductivity of 500 W/(mK) or more,
wherein in the elastic layer, pore portions are dispersed.
According to another aspect of the present invention, there is provided an image heating device comprising:
a heating member for heating a recording material on which an image is carried;
a pressing roller including a metal core and an elastic layer containing a needle-like filler which has an average length of 0.05 mm or more and 1 mm or less and a thermal conductivity of 500 W/(mK) or more, wherein the elastic layer forms, together with the heating member, a nip in which the recording material is to be nip-conveyed,
wherein in the elastic layer, pore portions are dispersed.
These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.
Part (a) of
Part (a) of
Parts (a), (b) and (c) of
Parts (a), (b) and (c) of
Parts (a) and (b) of
Parts (a) and (b) of
Parts (a), (b), (c) and (d) of
(1) Image Forming Apparatus
The printer in this embodiment includes a rotation drum type electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) 1 as an image bearing member. The photosensitive drum 1 is prepared by forming a layer of a photosensitive material of OPC, amorphous Se, amorphous Si or the like on an outer peripheral surface of a cylinder (drum)-like electroconductive substrate formed of a metal material such as aluminum or nickel. The photosensitive drum 1 is rotated in an arrow direction at a predetermined peripheral speed (process speed) depending on a print instruction outputted from an external device such as a host computer or a terminal machine on the network. Then, during this rotation process, the one peripheral surface of the photosensitive drum 1 is uniformly charged to a predetermined polarity and a predetermined potential by a charging roller 2 as a charging means. The uniformly charged surface of the photosensitive drum 1 is subjected to scanning exposure to a laser beam LB, which is modulation controlled (ON/OFF-controlled) depending on image information, from the external device, outputted from a laser beam scanner 3 as a scanning exposure device. As a result, an electrostatic latent image (electrostatic image) depending on an objective image information is formed on the surface of the photosensitive drum 1. A developing device 4 as a developing means deposits toner developer TO on the latent image, thus developing the latent image as a toner image (developer image). As a developing method, a jumping developing method, a two-component developing method, FEED developing method or the like are used and in many cases, a combination of image exposure and a reverse developing system is employed.
Separately, a recording material P accommodated and stuck in a sheet feeding cassette 9 is fed one by one by rotation of a feeding roller 8 and passes through a sheet path including a guide 10, thus being conveyed to a registration roller 11. The registration roller 11 feeds the recording material P, with predetermined control timing, to a transfer nip between the photosensitive drum surface and the outer peripheral surface of a transfer roller 5. The recording material P is nip-conveyed in the transfer nip and in this conveyance process, the toner image on the photosensitive drum 1 surface is successively transferred onto the recording material P by a transfer bias applied to the transfer roller 5. As a result, the recording material P carries an unfixed toner image.
The recording material P carrying the unfixed toner image (unfixed image) thereon is sequentially separated from the photosensitive drum 1 surface and is discharged from the transfer nip. Then, the recording material P is introduced into a nip N of a fixing device 6 through a conveyance guide 12. The recording material P passes through the nip N, so that the toner image is heat-fixed on the surface of the recording material P. The recording material P coming out of the fixing device 6 passes through a sheet path including a conveying roller 13, a guide 14 and a discharging roller 15 and is discharged on a discharge tray 16 as a print-out product.
The surface of the photosensitive drum 1 after the separation of the recording material P therefrom is subjected to removal of a deposited contaminant such as transfer residual toner by a cleaning device 7 as a cleaning means, thus being cleaned. Then, the photosensitive drum 1 is repetitively subjected to image formation.
The printer in this embodiment is an A4-sized paper compatible printer and the process speed thereof is 60 sheets/min (A4 portrait). Further, as the toner, a styrene-acrylic resin material is used as a principal material and in the principal material, a charge control agent, a magnetic material, silica and the like are internally or externally added as desired. The resultant toner having a glass transition point of 55-65° C. was used.
(2) Fixing Device (Image Heating Device) 6
In the following description, with respect to the fixing device and members constituting the fixing device, a longitudinal direction refers to a direction perpendicular to a recording material conveyance direction on the surface of the recording material. A widthwise direction refers to a direction parallel to the recording material conveyance direction on the surface of the recording material. A length refers to a dimension with respect to the longitudinal direction. A width refers to a dimension with respect to the widthwise direction.
The fixing device 6 in this embodiment includes a cylindrical flexible film 23 as a heating member (hereinafter referred to as a fixing film) and a ceramic heater 22 as a heating member. Further, the fixing device 6 includes a film guide 21 and a pressing roller 24 as a pressing member. These members are elongated members extending in the longitudinal direction. The film guide 21 is formed in a substantially semicircular trough shape in cross section. The film guide 21 is a molded product of a heat resistant resin material such as PPS (polyphenylene sulfide) or a liquid crystal polymer or the like. The film guide 21 is supported at its longitudinal end portions by a device frame (not shown) of the fixing device 6.
The heater 22 has a low thermal capacity as a whole and is an elongated member extending in the longitudinal direction. This heater 22 is accommodated in a groove provided along the longitudinal direction at a substantially central portion of the lower surface of the film guide 21 with respect to the widthwise disperse. The heater 22 includes an elongated heater substrate 22a of alumina extending in the longitudinal direction of the fixing film 23. Further, on a fixing film 23-side surface of the heater substrate 22a, a heat generating resistor (energization heat generating element) 22b is provided in a linear shape or a fine stripe shape along the longitudinal direction of the heater substrate. To the heat generating resistor 22b, electric energy is supplied from an energization controller 25 described later through an electric energy supply electrode (not shown) provided inside and at each of longitudinal portions of the heater substrate 22a. Further, on a fixing film 23-side surface of the heater substrate 22a, a thin surface protective layer 22c, such as a glass layer, for covering and protecting the energization heat generating element 22b is provided.
The fixing film 23 is loosely engaged externally with the film guide 21 by which the heater 22 is supported. The fixing film 23 is a composite layer film formed, by coating a parting layer on the surface of a cylindrical base film, in a total thickness of 100 μm or less, preferably 20 μm or more and 60 μm or less in order to improve a quick start property by reducing the thermal capacity. As the material for the base film, it is possible to use a resin material such as PI (polyimide), PAI (polyamideimide), PEEK (polyether ether ketone) or PES (polyether sulfone) or a metal material such as SUS or Ni. As the material for the parting layer, it is possible to use a fluorine-containing resin material such as PTFE (polytetrafluoroethylene), PFA (tetrafluoroethylene-perfluoroalkylvinyl ether) or FEP (tetrafluoroethylene-hexafluoropropylene).
The pressing roller 24 includes a cylindrical shaft metal core 24c formed of the metal material such as iron or aluminum, an elastic layer 24a provided on the outer peripheral surface of the metal core 24c, and a tube 24b as a parting layer provided to cover the outer peripheral surface of the elastic layer 24a. The pressing roller 24 is disposed under and in contact with the fixing film 23 and is supported rotatably by the device frame via bearings (not shown) at longitudinal end portions of the metal core 24c. Further, the pressing roller 24 is urged by urging springs (not shown) with a predetermined urging force, so that the elastic layer 24a of the pressing roller 24 is elastically deformed to form the fixing nip N with a predetermined width between the fixing film 23 surface and the pressing roller 24 surface.
In the fixing device 6 in this embodiment, a fixing motor M as a driving source is rotationally driven depending on the print instruction. A rotational force of an output shaft of the fixing motor M is transmitted to the metal core 24c of the pressing roller 24 via a predetermined gear train (not shown), so that the pressing roller 24 is rotated in an arrow direction. The rotational force of the pressing roller 24 is transmitted to the fixing film 23 in the fixing nip N by a frictional force between the pressing roller 4 surface and the fixing film 23 surface. As a result, the fixing film 23 is rotated in an arrow direction by the rotation of the pressing roller 24 while being contacted to the surface protecting layer 22c of the heater 22 at inner peripheral surface of the fixing film 24. Further, depending on the print instruction, the energization controller 25 supplies the electric energy to the heat generating resistor 22b via the electric energy supply electrode of the heater 22. As a result, so that the heat generating resistor 22b generates heat and thus the heater 22 is quickly increased in temperature to heat the fixing film 23. The temperature of the heater 22 is detected by a temperature detecting element (temperature detecting member) 26 such as a thermistor provided on a substrate surface of the heater substrate 22a at a side opposite from the heat generating resistor 22b side. The energization controller 25 obtains (reads) a temperature detection signal (output signal) outputted from the temperature detecting element 26 and on the basis of this temperature detection signal, and controls the energization to the heat generating resistor 22b so as to maintain the temperature of the heater 22 at a predetermined fixing temperature (target temperature). In a state in which the fixing motor M is rotationally driven and the energization to the heat generating resistor 22b of the heater 22 is controlled, the recording material P on which an unfixed toner image t is carried is introduced into the fixing nip N with a toner image carrying surface upward. The recording material P is nipped in the fixing nip N between the fixing film 23 surface and the pressing roller 24 surface and is then conveyed (nip-conveyed) in the nipped state. In this conveying process, the toner image t is heated and melted by the heater 22 via the fixing film 23 and is supplied with the nip pressure, so that the toner image t is heat-fixed on the surface of the recording material P.
(3) Pressing Roller 24
Materials constituting the pressing roller 24, a manufacturing method (process), and the like will be described below in detail.
3-1) Layer Structure of Pressing Roller 24
As described above, the pressing roller 24 includes the cylindrical shaft metal core 24c, the elastic layer 24a and the tube 24b as the parting layer.
3-1-1) Elastic Layer 24a
Part (b) of
As a heat resistant elastic material as the matrix material of the elastic layer 24a, it is possible to use a general purpose heat resistant solid rubber elastic material such as a silicone rubber or a fluorine-containing rubber. Both of the silicone rubber and the fluorine-containing rubber have sufficient heat resistant property and durability and preferable elasticity (softness) in the case where they are used in the fixing device 6. In the case where the silicone rubber is used, from the viewpoints of availability and ease of processing, a liquid addition-curable silicone rubber is preferred. In this embodiment, as the heat resistant elastic material, the liquid addition-curable silicone rubber is used but the heat resistant elastic material is not limited thereto. Other elastic materials may also be used.
The needle-like filler 24d include fibers each having an elongated fiber shape as shown in (f) of
The hollow member 24e is formed in a dispersed state among the fibers of the needle-like filler 24d oriented in the elastic layer 24a.
(a) State of Needle-Like Filler 24d and Hollow Member 24e In Elastic Layer 24
In
As shown in (a) of
(b) Needle-Like Filler (Elongated Fiber-Like Filler) 24d
As the needle-like filler 24d, from a heat conduction performance of the needle-like filler 24d, pitch-based carbon fiber manufactured by using petroleum pitch or coal pitch as a starting material is preferable. Further, in order to enhance the effect of alleviating (reducing) the degree of the non-sheet-passing portion temperature rise, a thermal conductivity γ of the needle-like filler 24d with respect to the long axis disperse may preferably be 500 W/(mK) or more. The thermal conductivity γ was measured by using a laser flash method thermal constant measuring system (“TC-7000”, mfd. by ULVAC-RIKO, Inc.).
Further, when an average length of the needle-like filler 24d is shorter than 50 μm (0.05 mm), the thermal conductivity anisotropic effect is less liable to be obtained in the elastic layer 24a, so that the non-sheet-passing portion temperature rise alleviating effect becomes small. When the average length of the needle-like filler 24d is longer than 1 mm, at the time of being kneaded with the liquid addition-curable silicone rubber 24i, the viscosity of the liquid addition-curable silicone rubber 24i becomes excessively high, so that it becomes difficult to mold the liquid addition-curable silicone rubber 24i. Therefore, in order to easily obtain the thermal conductivity anisotropic effect in the elastic layer 24a and to obtain the non-sheet-passing portion temperature rise alleviating effect, the needle-like filler 24d of 0.05 mm or more and 1 mm or less in average length and 500 W/(mK) or more in thermal conductivity with respect to the long axis disperse may preferably be used. Further, an average fiber diameter of the needle-like filler 24d may preferably be about 10 μm. In this embodiment, the average length of the needle-like filler 24d is obtained by observation through an optical microscope.
A lower limit of the content of the needle-like filler 24d in the elastic layer 24a may preferably be 5 vol. % or more. Below 5 vol. %, the thermal conductivity with respect to the roller longitudinal direction is lowered and an expected effect of alleviating the degree of the non-sheet-passing portion temperature rise. An upper limit of the content of the needle-like filler 24d in the elastic layer 24a may preferably be 40 vol. % or less. Above 40 vol. %, it becomes difficult to process and mold the elastic layer 24a. Therefore, the content of the needle-like filler 24d in the elastic layer 24a may preferably be 5 vol. % or more and 40 vol. % or less. A volume ratio of the needle-like filler 24d to the elastic layer 24a is obtained from; (Volume of whole needle-like filler 24d contained in elastic layer 24a)/(Volume of whole elastic layer 24a)×100 (vol. %).
(c) Hollow Member 24e
Part (g) of
The average particle size of the hollow member 24e in the elastic layer 24a after the curing may preferably be 70 μm or less. When the average particle size of the hollow member 24e is larger than 70 μm, as shown in (g) of
Further, a lower limit of the amount of the hollow member 24e formed in the elastic layer 24a may preferably be 1 vol. %. Below 1 vol. %, a desired heat resistant effect of the elastic layer 24a with respect to the thickness direction cannot be obtained. An upper limit of the hollow member 24e formed in the elastic layer 24a may preferably be 10 vol. %. Above 10 vol. %, the hollow member 24e hinders the orientation of the needle-like filler 24d in the roller longitudinal direction. Therefore, in order to obtain a predetermined heat insulating effect with respect to the thickness direction of the elastic layer 24a and in order that the orientation of the needle-like filler 24d in the roller longitudinal direction is not hindered, the amount of the hollow member 24e formed in the elastic layer 24a may preferably be 1 vol. % or more and 10 vol. % or less. A volume ration of the hollow member 24e to the elastic layer 24a is obtained by: (Volume of whole hollow member 24e formed in elastic layer 24a)/(Volume of whole elastic layer 24a)×100 (vol. %).
The hollow member 24e in the elastic layer 24a in this embodiment refers to pore portions formed in the elastic layer 24a. Examples of the pore portions may include those in which only pores are formed by deflation of capsules after the molding of the elastic layer 24a and those in which pores are formed with microballoons such as glass balloons in capsules after the molding of the elastic layer 24a.
As described above, in the elastic layer 24a, it is preferable that the needle-like filler 24d in an amount of 5 vol. % or more and 40 vol. % or less and the hollow member (pore portions) 24e in an amount of o1 vol. % or more and 10 vol. % or less are dispersed.
(d) Definition of Orientation Degree of Needle-Like Filler
In order to know the thermal conductivity of the elastic layer 24a, an orientation degree (orientation percentage) of the needle-like filler 24d in the elastic layer 24a is defined. Here, an inclination (angle) of the filler when a surface A shown in (a) of
The definition of the orientation degree will be described with reference to
The orientation degree of the needle-like filler 24d is obtained by using the sample 24a1 shown in (a) of
At each of the surfaces A and B, when the fibers of the needle-like filler 24d with the angles θ within ±5 degrees are present in an amount (orientation degree) of 20% or more in the entire needle-like filler 24d, the following functional effect can be obtained. That is, the thermal conductivity of the elastic layer 24a with respect to the roller longitudinal direction is better and a desired non-sheet-passing portion temperature rise alleviating effect is achieved. Further, it is possible to enhance the heat insulating performance of the elastic layer 24a with respect to the thickness direction.
3-1-2) Tube 24b
The tube 24b is provided on the outer peripheral surface of the elastic layer 24a. Specifically, as the tube 24b, PFA tube, FEP tube and the like may suitably be used but the tube 24b is not limited to these tubes. In this embodiment, a 50 μm-thick tube 24b is used but the thickness is not particularly limited when the tube 24b has the thickness in which a sufficient parting property is imparted to the pressing roller 24.
3-2) Manufacturing Method of Pressing Roller 24
As a manufacturing method of the pressing roller 24, it is generally possible to use a molding method such as metal molding or coat molding can be used.
The needle-like filler 24d has the elongated fiber shape and therefore when is kneaded with the liquid addition-curable silicone rubber before curing and then is molded, the fiber length portion L of the needle-like filler 24d is liable to be oriented in the flowing direction of the liquid addition-curable silicone rubber, i.e., the roller longitudinal direction of the elastic layer 24a. For that reason, when the liquid addition-curable silicone rubber before curing is cured to mold the elastic layer 24a, the thermal conductivity of the elastic layer 24a with respect to the roller longitudinal direction is enhanced.
3-3) Evaluation of Pressing Roller 24
<Orientation Degree>
The orientation degree was obtained in accordance with the above-described definition with respect to each of pressing rollers in Embodiments 1 to 7 and Comparative Embodiments 1 to 7 described later.
<Thermal Conductivity>
A measuring method of the thermal conductivity of the elastic layer 24a will be described with reference to
When the thermal conductivity was measured, as shown in (b) of
<Evaluation of Non-Sheet-Passing Portion Temperature Rise>
The non-sheet-passing portion temperature rise was evaluated after each of the pressing rollers in Embodiments 1 to 7 and Comparative Embodiments 1 to 7 was mounted in a film-heating type fixing device. In each of printers in which the respective fixing devices were mounted, the peripheral speed (process speed) of the pressing roller of the fixing device was adjusted at 370 mm/sec and the fixing temperature was set at 180° C. at the surface of the fixing film. The recording material passed through the nip of the fixing device was A4-sized paper (80 g/m2). The non-sheet-passing portion temperature rise (temperature at the non-sheet-passing portion) on the fixing film surface was measured at the time when 500 sheets were continuously passed through the nip at rate of 60 sheets/min.
<Rising Performance>
The rising performance was evaluated by measuring the surface temperature of the fixing film surface at the time of rising of the fixing device in each printer. Specifically, a time until the temperature of the fixing film surface reaches a predetermined fixing temperature (target temperature) was measured. Here, the time of rising refers to the time from start of energization to the heater until the fixing film surface temperature is increased up to the fixable temperature.
<Evaluation Results>
The evaluation results of the pressing rollers in Embodiments 1 to 7 and Comparative Embodiments 1 to 7 were summarized in Table 1 appearing at the last of the description on the pressing rollers in Embodiments 1 to 7 and Comparative Embodiments 1 to 7.
3-4) Pressing Rollers in Embodiments 1 to 7 and Comparative Embodiments 1 to 7
The needle-like filler 24d and the hollow member 24e which were used in each of the pressing rollers in Embodiments 1 to 7 and Comparative Embodiments 1 to 7 will be described. As the needle-like filler 24d, three types (A) to (C) of pitch-based carbon fibers shown below are used. Further, as the hollow member 24e, three types (D) to (F) of resin balloons shown below were used.
(A) Type: 100-15M
Trade name: “XN-100-15M” (mfd. by Nippon Graphite Fiber Corp.)
Average fiber diameter: 9 μm
Average fiber length: 150 μm
Thermal conductivity: 900 W/(mK)
(B) Type: 100-05M
Trade name: “XN-100-05M” (mfd. by Nippon Graphite Fiber Corp.)
Average fiber diameter: 9 μm
Average fiber length: 50 μm
Thermal conductivity: 900 W/(mK)
(C) Type: 100-01
Trade name: “XN-100-01” (mfd. by Nippon Graphite Fiber Corp.)
Average fiber diameter: 10 μm
Average fiber length: 1 mm
Thermal conductivity: 900 W/(mK)
(D) Type: 80SDE
Trade name: “F-80SDE” (mfd. by Matsumoto Yushi-Seiyaku Co., Ltd.)
Average particle size: 20-40 μm
(E) Type: 50E
Trade name: “F-50E” (mfd. by Matsumoto Yushi-Seiyaku Co., Ltd.)
Average particle size: 40-70 μm
Here, this material has a high water content and therefore the hollow member 24e is dried, before mixing, in a drying step.
(F) Type: 80DE
Trade name: “F-80DE” (mfd. by Matsumoto Yushi-Seiyaku Co., Ltd.)
Average particle size: 9 μm
3-4-1) Effect of Forming Hollow Member 24e
A pressing roller having a constitution in which the needle-like filler 24d was contained in the elastic layer 24a formed on the outer peripheral surface of the metal core 24c and in which the hollow member 24e was dispersed in the elastic layer 24a was used as a pressing roller P1 in Embodiment 1. On the other hand, a pressing roller having a constitution in which the needle-like filler 24d was contained in the elastic layer 24a formed on the outer peripheral surface of the metal core 24c and in which the hollow member 24e was not dispersed in the elastic layer 24a was used as a pressing roller P8 in Comparative Embodiment 1.
(Pressing Roller in Embodiment 1)
The pressing roller P1 in Embodiment 1 includes the elastic layer 24a in which the needle-like filler 24d is contained as the hollow member 24e is formed. With reference to
Then, liquids A and B shown below are mixed in a mixing ratio of 1:1 and thereto, a platinum compound as a catalyst is added, thus obtaining the liquid addition-curable silicone rubber 24i.
Weight average molecular weight (Mw)=65000
Number average molecular weight (Mn)=15000
Liquid A: vinyl group concentration (0.863 mol. %), SiH concentration (0 (zero) mol. %), viscosity (7.8 Pa·s)
Liquid B: vinyl group concentration (0.955 mol. %), SiH concentration (0.780 mol. %), viscosity (6.2 Pa·s)
H/Vi=0.43 (when A/B=1/1)
With respect to the pressing roller P1 in Embodiment 1, the pitch-based carbon fiber (“100-15M”) as the needle-like filler 24d was added in the liquid addition-curable silicone rubber 24i so as to occupy the proportion of 20 vol. %. Further, in the liquid addition-curable silicone rubber 24i, the resin balloon (“80SDE”) was added so as to occupy the proportion of 5 vol. %. The liquid addition-curable silicone rubber 24i, the pitch-based carbon fiber (“100-15M”) and the resin balloon (“80SDE”) were uniformly kneaded to obtain a liquid addition-curable silicone rubber composition 24i1 before curing.
Before molding the elastic layer 24a, in order to bond the metal core 24c and the elastic layer 24a together, a primer was applied onto the outer peripheral surface of the metal core 24c of Al (21 mm in diameter). Next, as shown in
(Pressing Roller in Comparative Embodiment 1)
The pressing roller P8 in Comparative Embodiment 1 was, similarly as in the case of the pressing roller P1 in Embodiment 1, prepared by forming the elastic layer 24a on the metal core 24c. However, in the elastic layer 24a, only the needle-like filler 24d was contained but the hollow member 24e was not formed.
By comparing the pressing roller P1 in Embodiment 1 with the pressing roller P8 in Comparative Embodiment 1, it is possible to check an effect of forming the hollow member 24e in the elastic layer 24a having the thermal conductivity anisotropy. With respect to the pressing roller P8 in Comparative Embodiment 1, the constitution thereof was the same as that of the pressing roller P1 in Embodiment 1 except that the hollow member 24e was not contained.
Evaluation results of the pressing roller P1 in Embodiment 1 and the pressing roller P8 in Comparative Embodiment 1 are summarized in Table 2 below. Both of the pressing rollers P1 and P8 were prepared by forming the elastic layer 24a on the outer peripheral surface of the metal core 24c.
In the fixing device including the pressing roller P1 in Embodiment 1, the pressing roller P1 in Embodiment 1 includes, in addition to the constitution of the pressing roller P8 in Comparative Embodiment 1, the hollow member 24e formed in the elastic layer 24a. Thus, in the pressing roller P1 in Embodiment 1, the hollow member 24e is formed in the elastic layer 25a but compared with the pressing roller P8 in Comparative Embodiment 1, the orientation degree and the thermal conductivity are comparable and the transfer suppressing effect for the non-sheet-passing portion temperature rise is not impaired. In addition, in the pressing roller P1 in Embodiment 1, the hollow member 24e is formed in the elastic layer 24a and therefore the thermal conductivity with respect to the z direction is lower than that of the pressing roller P8 in Comparative Embodiment 1, so that the rising performance of the fixing film 23 is improved.
3-4-2) Constitutions with Changed Formation Proportions of Hollow Member 24e
Next, as an example of the pressing roller, a constitution in which the elastic layer 24a is formed on the outer peripheral surface of a solid rubber elastic layer 24f will be described. Further, an effect with respect to the formation proportion of the hollow member 24e will be described by using pressing rollers P2, P3 and P4 in Embodiments 2, 3 and 4 and pressing rollers P9, P12 and P13 in Comparative Embodiments 2, 5 and 6.
Parts (a) and (b) of
(Pressing Roller in Embodiment 2)
The pressing roller P2 in Embodiment 2 is prepared by forming the elastic layer 24a on the outer peripheral surface of the solid rubber elastic layer 24f. In the elastic layer 24a, the needle-like filler 24d is contained and the hollow member 24e is formed. The elastic layer 24a is formed on the outer peripheral surface of the solid rubber elastic layer 24f, so that the pressing roller P2 in Embodiment 2 has a higher thickness direction heat insulating effect than that of the pressing roller P1 in Embodiment 1. That is, the pressing roller P2 in Embodiment 2 has a lamination structure of at least two layers including the solid rubber elastic layer 24f and the elastic layer 24a. As the outermost elastic layer, the elastic layer 24a containing the needle-like filler 24d which has an average length of 0.05 mm or more and 1 mm or less and has the thermal conductivity anisotropy providing the length direction thermal conductivity of 500 W/(mK) or more is used. In this elastic layer 24a, the hollow member 24 is formed and the needle-like filler 24d is oriented in the roller longitudinal direction.
With reference to
First, on the outer peripheral surface of the metal core 24c of Al with the diameter of 18 mm, the solid rubber elastic layer 24f is provided by using an addition type silicone rubber with a density of 1.20 g/cm3 in accordance with the metal molding method to obtain the solid rubber elastic layer molded product ((a) of
Next, the molding method of the elastic layer 24a will be described. By the same method as in the case of the pressing roller P1 in Embodiment 1, the liquid addition-curable silicone rubber is obtained.
With respect to the pressing roller P2 in Embodiment 2, the pitch-based carbon fiber (“100-15M”) as the needle-like filler 24d was added in the liquid addition-curable silicone rubber 24i so as to occupy the proportion of 20 vol. %. Further, in the liquid addition-curable silicone rubber 24i, the resin balloon (“80SDE”) was added so as to occupy the proportion of 1 vol. %. The liquid addition-curable silicone rubber 24i, the pitch-based carbon fiber (“100-15M”) and the resin balloon (“80SDE”) were uniformly kneaded to obtain a liquid addition-curable silicone rubber composition 24i2 before curing.
Before molding the elastic layer 24a, in order to bond the solid rubber elastic layer 24f and the elastic layer 24a together, a primer was applied onto the outer peripheral surface of the solid rubber elastic layer 24f of the solid rubber elastic layer molded product. Next, as shown in
(Pressing roller in Comparative Embodiment 2)
In the pressing roller P9 in Comparative Embodiment 2, similarly as in the case of the pressing roller P2 in Embodiment 2, the elastic layer 24a is formed on the outer peripheral surface of the solid rubber elastic layer 24f. In the elastic layer 24a, only the needle-like filler 24d is contained and the hollow member 24e is not formed. By comparing the pressing roller P2 in Embodiment 2 with the pressing roller P9 in Comparative Embodiment 2, it is possible to confirm an effect of formation of the hollow member 24e.
Thus, the pressing roller P2 in Comparative Embodiment 2 was prepared in the same manner as in the case of the pressing roller P2 in Embodiment 2 except that the hollow member 24e is not contained in the elastic layer 24a.
(Pressing Rollers in Embodiments 3 and 4 and Comparative Embodiments 5 and 6)
The pressing rollers P3 and P4 in Embodiments 3 and 4 were, similarly as in Embodiment 2, prepared by forming the elastic layer 24a on the outer peripheral surface of the solid rubber elastic layer 24f. The pressing rollers P12 and P13 in Comparative Embodiments 5 and 6 were also, similarly as in Embodiment 2, prepared by forming the elastic layer 24a on the outer peripheral surface of the solid rubber elastic layer 24f. Further, in the pressing rollers P3 and P4 in Embodiments 3 and 4 and the pressing rollers P13 and P14 in Comparative Embodiments 5 and 6, the formation proportion of the hollow member 24e in the elastic layer 24a is changed.
That is, the pressing rollers, P3, P4, P12 and P13 in Embodiments 3 and 4 and Comparative Embodiments 5 and 6, respectively, were obtained similarly as in the case of the pressing roller P2 in Embodiment 2 except that the formation proportion of the hollow member 24e in the elastic layer 24a was changed.
Evaluation results of the pressing rollers P2 to P4 in Embodiments 2 to 4 and the pressing rollers P9, P12 and P13 in Comparative Embodiments 2, 5 and 6 are summarized in Table 3 below. Further, relationships among the formation proportion of the hollow member 25e in the elastic layer 24a, the orientation degree and the thermal conductivity are shown in (a) to (d) of
In the fixing device including the pressing roller P2 in Embodiment 2, the pressing roller P2 in Embodiment 2 includes, in addition to the constitution of the pressing roller P9 in Comparative Embodiment 2, the hollow member 24e formed in the elastic layer 24a. Thus, in the pressing roller P2 in Embodiment 2, the hollow member 24e is formed in the elastic layer 25a but compared with the pressing roller P9 in Comparative Embodiment 2, the orientation degree and the thermal conductivity are comparable and the transfer suppressing effect for the non-sheet-passing portion temperature rise is not impaired. In addition, in the pressing roller P2 in Embodiment 2, the hollow member 24e is formed in the elastic layer 24a and therefore the thermal conductivity with respect to the z direction is lower than those of the pressing rollers P9, P12 and P13 in Comparative Embodiments 2, 5 and 6, so that the rising performance of the fixing film 23 is improved.
In the respective fixing devices including the pressing rollers P2 to P4 in Embodiments 2 to 4, the formation proportion of the hollow member 24e in each of the elastic layers 24a of the pressing rollers P2 to P4 in Embodiments 2 to 4 is changed. As shown in (d) of
In the pressing rollers P12 and P13 in Comparative Embodiments 5 and 6, in addition to the constitution of the pressing roller P9 in Comparative Embodiment 2, the hollow member 24e is formed in the elastic layer 24a in the formation proportions 0.5 vol. % and 15 vol. %, respectively. However, in the fixing device including the pressing roller P12 in Comparative Embodiment 15, the proportion of the hollow member 24e formed in the elastic layer 24a of the pressing roller P12 in Comparative Embodiment 4 is low. For this reason, as shown in (d) of
As is understood from (a) of
From the above, the hollow member 24e may preferably be formed in the elastic layer 24a having the thermal conductivity anisotropy, in the formation proportion of 1 vol. % or more and 10 vol. % or less. That is, the hollow member 24e may preferably be formed in the elastic layer 24a at a volume ratio of 1% or more and 10% or less.
3-4-3) Constitutions with Changed Average Particle Sizes of Hollow Member 24e
(Pressing Rollers of Embodiment 5 and Comparative Embodiment 7)
A pressing roller P5 in Embodiment 5 and a pressing roller P14 in Comparative Embodiment 7 were, similarly as in the case of the pressing roller P2 Embodiment 2, prepared by forming the elastic layer 24a on the outer peripheral surface of the solid rubber elastic layer 24f. In the pressing roller P5 in Embodiment 5 and the pressing roller P14 in Comparative Embodiment 7, the average particle size of the hollow member 24e formed in the elastic layer 24a is changed.
Thus, the pressing rollers P5 and P14 in Embodiment 5 and Comparative Embodiment 7, respectively, were prepared in the same manner as in the case of the pressing roller P2 in Embodiment 2 except that the average particle size of the hollow member 24e is changed. Evaluation results of the pressing roller P5 in Embodiment 5 and the pressing roller P14 in Comparative Embodiment 7 are summarized in Table 4.
In the fixing device including the pressing roller P5 in Embodiment 5, the hollow member 24e having a large average particle size of 40-70 μm is formed in the elastic layer 24a. Even when compared with a pressing roller P4 in Embodiment 4 in which the average particle size of the hollow member 24e is 20-40 μm, both of the orientation degree and the thermal conductivity are comparable with those of the pressing roller P4 in Embodiment 4, so that both of the non-sheet-passing portion temperature rise suppressing effect and the rising performance of the fixing film 23 are also substantially comparable with those of the pressing roller P4 in Embodiment 4.
In the fixing device including the pressing roller 14 in Comparative Embodiment 7, the hollow member 24e having the average particle size of 90-110 μm which is further larger than that in the pressing roller P5 in Embodiment 5 is formed in the elastic layer 24a. For that reason, as described above with reference to (g) of
From the above, the average particle size of the hollow member 24e formed in the elastic layer 24a may preferably be 70 μm or less.
3-4-4) Constitutions with Changed Average Fiber Lengths and Contents of Needle-Like Filler 24d
(Pressing Rollers in Embodiments 6 and 7 and Comparative Embodiments 3 and 4)
Pressing rollers P6 and P7 in Embodiments 6 and 7 are, similarly as in the case of the pressing roller P2 in Embodiment 2, prepared by forming the elastic layer 24a having the thermal conductivity anisotropy on the outer peripheral surface of the solid rubber elastic layer 24f. Further, pressing rollers P10 and P11 in Comparative Embodiments 3 and 4 are also, similarly as in the case of the pressing roller P2 in Embodiment 2, prepared by forming the elastic layer 24a having the thermal conductivity anisotropy on the outer peripheral surface of the solid rubber elastic layer 24f. In the pressing rollers P6, P7, P1 and P11 in Embodiments 6 and 7 and Comparative Embodiments 3 and 4, respectively, the average fiber length and content of the needle-like filler 24d in the elastic layer 24a are changed.
The pressing rollers P6 and P7 in Embodiments 6 and 7 are equal in average fiber length and content of the needle-like filler 24d in the elastic layer 24a to those in the pressing rollers P10 and P11 in Comparative Embodiments 3 and 4, respectively. Further, in addition to the constitutions of the pressing rollers P10 and P11 in Comparative Embodiments 3 and 4, in the pressing rollers P6 and P7 in Embodiments 6 and 7, the hollow member 24e is formed. By comparing the pressing rollers P6 and P7 in Embodiments 6 and 7 with the pressing rollers P10 and P11 of in Comparative Embodiments 3 and 4, respectively, it is possible to confirm the effect of formation of the hollow member 24e when the average fiber length and content of the needle-like filler 24d in the elastic layer 24a are changed.
The pressing rollers 6 and 7 in Embodiments 6 and 7 were prepared in the same manner as in the case of the pressing roller P2 in Embodiment 2 except that the average fiber length and content of the needle-like filler 24d in the elastic layer 24a were changed. The pressing rollers P10 and P11 in Comparative Embodiments 3 and 4 were prepared in the same manner as in the case of the pressing roller P2 in Embodiment 2 except that the average fiber length and content of the needle-like filler 24d in the elastic layer 24a were changed and that the hollow member 24d was not formed in the elastic layer 24a.
Evaluation results of the pressing rollers P6 and P7 in Embodiments 6 and 7 and the pressing rollers P10 and P11 in Comparative Embodiments 3 and 4 are summarized in Table 5.
The effect of formation of the hollow member 24e when the average fiber length and content of the needle-like filler 24d are changed will be confirmed.
In the pressing roller P6 in Embodiment 6 and the pressing roller P10 in Comparative Embodiment 3, the needle-like filler 24d having a relatively short average fiber length of 50 μm is contained in the elastic layer 24a at the low content of 5 vol. %.
In the fixing device including the pressing roller P6 in Embodiment 6, the pressing roller P6 in Embodiment 6 includes, in addition to the constitution of the pressing roller P10 in Comparative Embodiment 3, the hollow member 24e formed in the elastic layer 24a having the thermal conductivity anisotropy. Thus, in the pressing roller P6 in Embodiment 6, the hollow member 24e is formed in the elastic layer 25a but compared with the pressing roller P10 in Comparative Embodiment 3, the orientation degree and the thermal conductivity are comparable and the transfer suppressing effect for the non-sheet-passing portion temperature rise is not impaired. In addition, in the pressing roller P6 in Embodiment 6, the hollow member 24e is formed in the elastic layer 24a and therefore the thermal conductivity with respect to the z direction is lower than that of the pressing roller P10 in Comparative Embodiment 3, so that the rising performance of the fixing film 23 is improved. As a result, even when the average fiber length of the needle-like filler 24d was 50 μm and the content of the needle-like filler 24d was 5 vol. %, the effect of formation of the hollow member 24e in the elastic layer 24a was obtained.
In the pressing roller P7 in Embodiment 7 and the pressing roller P11 in Comparative Embodiment 4, the needle-like filler 24d having a relatively long average fiber length of 1 mm is contained in the elastic layer 24a at the high content of 40 vol. %.
In the fixing device including the pressing roller P7 in Embodiment 7, the pressing roller P7 in Embodiment 7 includes, in addition to the constitution of the pressing roller P11 in Comparative Embodiment 4, the hollow member 24e formed in the elastic layer 24a having the thermal conductivity anisotropy. Thus, in the pressing roller P7 in Embodiment 7, the hollow member 24e is formed in the elastic layer 25a but compared with the pressing roller P11 in Comparative Embodiment 4, the orientation degree and the thermal conductivity are comparable and the transfer suppressing effect for the non-sheet-passing portion temperature rise is not impaired. In addition, in the pressing roller P7 in Embodiment 7, the hollow member 24e is formed in the elastic layer 24a and therefore the thermal conductivity with respect to the z direction is lower than that of the pressing roller P11 in Comparative Embodiment 4, so that the rising performance of the fixing film 23 is improved. As a result, even when the average fiber length of the needle-like filler 24d was 1 mm and the content of the needle-like filler 24d in the elastic layer 24a was 40 vol. %, the effect of formation of the hollow member 24e in the elastic layer 24a was obtained.
(Pressing Roller in Comparative Embodiment 8)
In the pressing roller in Comparative Embodiment 8, the content of the needle-like filler 24d was 45 vol. % which was excessively large and therefore the viscosity was very high when the needle-like filler 24d was mixed with the liquid addition-curable silicone rubber, so that it was impossible to mold the elastic layer 24a.
From the above, the average fiber length of the needle-like filler 24d contained in the elastic layer 24a may preferably be 50 μm or more and 1 mm or less. The content of the needle-like filler 24d in the elastic layer 24a may preferably be 5 vol. % or more and 40 vol. % or less. That is, the elastic layer 24a may preferably contain the needle-like filler 24d at a volume ratio of 5% or more and 40% or less.
As described above, when the orientation degree of the needle-like filler 24d at the surface B (cross section of the elastic layer 24a at the thickness center portion) of the cut sample 24a1 from the elastic layer molded product is high, the thermal conductivity of the elastic layer 24a with respect to the roller longitudinal direction is good. Further, when the orientation degree of the needle-like filler 24d at the surface A (cross section of the elastic layer 24a with respect to the longitudinal direction) of the cut sample 24a1 from the elastic layer molded product is low, the thermal conductivity of the elastic layer 24a with respect to the thickness direction is not lowered. As a result, by defining the orientation degree of the needle-like filler 24d in the elastic layer 24a, it is possible to estimate the thermal conductivity of the elastic layer 24a.
In the pressing rollers in Embodiments 1 to 7 and Comparative Embodiments 1 to 8, when both of the orientation degrees at the surfaces A and B are 20% or more in terms of the percentage of the fibers of the needle-like filler 24d with the angle of within ±5 degrees when the roller longitudinal direction is taken as 0 degrees, the following effects can be achieved. That is, even when the hollow member 24e is formed in the elastic layer 24a, the non-sheet-passing portion temperature rise suppressing effect comparable to that of the pressing roller in which the hollow member 24e is not formed in the elastic layer 24a can be obtained and the rising performance of the fixing film 23 can also be improved.
As shown in Table 1 below, the pressing rollers having the orientation degree of 20% or more at both of the surfaces A and B are the pressing rollers P1 to P7 in Embodiments 1 to 7 and the pressing rollers P8 to P12 in Comparative Embodiments 1 to 5.
Further, as in the pressing rollers in Comparative Embodiments 7 and 8, in the case where the orientation degrees at the surfaces A and B are less than 20%, even when the hollow member 24e is formed in the elastic layer 24e, the rising performance of the fixing film 23 cannot be improved while keeping the temperature rise suppressing effect with respect to the non-sheet-passing portion temperature rise.
Further, when the thermal conductivity of the needle-like filler 24d with respect to the length direction is not 500 W/cm·K) or more, the roller longitudinal direction thermal conductivity of the elastic layer 24a having the thermal conductivity anisotropy is low, so that the effect of alleviating the degree of the non-sheet-passing portion temperature rise becomes small.
As described above, the pressing roller 24 in the present invention includes the elastic layer 24a containing the needle-like filler 24d which has an average length of 0.05 mm or more and 1 mm or less and has the thermal conductivity anisotropy providing the length direction thermal conductivity of 500 W/(mK) or more. In this elastic layer 24a, the hollow member 24 is formed and the needle-like filler 24d is oriented in the roller longitudinal direction. As a result, the pressing roller 24 in the present invention achieves such a functional effect that the thermal conductivity of the elastic layer 24a with respect to the roller longitudinal direction and the heat insulating property of the elastic layer 24a with respect to the thickness direction can be improved. Therefore, the fixing device in the present invention having the constitution in which the pressing roller 24 is used achieves the functional effect such that the degree of the non-sheet-passing portion temperature rise can be reduced and that the rising time of the fixing device, i.e., the time from the start of energization to the heater until the temperature of the heater reaches the fixable temperature can be shortened.
While the invention has been described with reference to the structures disclosed herein, it is not confined to the details set forth and this application is intended to cover such modifications or changes as may come within the purpose of the improvements or the scope of the following claims.
This application claims priority from Japanese Patent Applications Nos. 160570/2010 filed Jul. 15, 2010 and 141762/2011 filed Jun. 27, 2011, which are hereby incorporated by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-160570 | Jul 2010 | JP | national |
| 2011-141762 | Jun 2011 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 6007657 | Eddy et al. | Dec 1999 | A |
| 6459878 | Tomoyuki et al. | Oct 2002 | B1 |
| 6952553 | Sakakibara et al. | Oct 2005 | B2 |
| 6989182 | Chen et al. | Jan 2006 | B2 |
| 7001653 | Chen et al. | Feb 2006 | B2 |
| 7008678 | Chen et al. | Mar 2006 | B2 |
| 7014899 | Chen et al. | Mar 2006 | B2 |
| 7321746 | Sakakibara et al. | Jan 2008 | B2 |
| 7974563 | Sakai et al. | Jul 2011 | B2 |
| 8005413 | Sakakibara et al. | Aug 2011 | B2 |
| 8224223 | Sakakibara et al. | Jul 2012 | B2 |
| 8369763 | Sakakibara et al. | Feb 2013 | B2 |
| 8369764 | Sugawara | Feb 2013 | B2 |
| 8380113 | Natori et al. | Feb 2013 | B2 |
| 8401450 | Sekihara et al. | Mar 2013 | B2 |
| 20050214044 | Sakakibara et al. | Sep 2005 | A1 |
| 20090003902 | Sakakibara et al. | Jan 2009 | A1 |
| 20090116886 | Sakai et al. | May 2009 | A1 |
| 20110091252 | Sekihara et al. | Apr 2011 | A1 |
| 20110217092 | Sekihara et al. | Sep 2011 | A1 |
| 20120027479 | Uekawa et al. | Feb 2012 | A1 |
| Number | Date | Country |
|---|---|---|
| 11302545 | Nov 1999 | JP |
| 2002351243 | Dec 2002 | JP |
| 2005-273771 | Oct 2005 | JP |
| 2008-191557 | Aug 2008 | JP |
| 2008197585 | Aug 2008 | JP |
| 2009-31772 | Feb 2009 | JP |
| 2009-109952 | May 2009 | JP |
| Entry |
|---|
| Machine Translation of Japanese Patent JP2002351243. Dec. 6, 2002. |
| Number | Date | Country | |
|---|---|---|---|
| 20120014726 A1 | Jan 2012 | US |
