JP3800347B2 - Plate heater, fixing device and image forming apparatus - Google Patents

Description

[0001]
[Industrial application fields]
The present invention is used for fixing a toner in a thin plate heater mounted on a small device such as an OA device, a household electric device, or a precision manufacturing facility, and a copying machine or a facsimile equipped with the plate heater. The present invention relates to a fixing device and an image forming apparatus using the fixing device.
[0002]
[Prior art]
In general, in an electronic copying machine, a copy sheet on which a toner image is formed is passed while being directly or indirectly sandwiched between a fixing plate heater and a pressure roller. The toner is heated, melted and fixed.
[0003]
As this type of conventional plate heater for fixing, one having a structure as shown in FIGS. 5 and 6 has been put into practical use. This heater H is a glass powder (inorganic binder) made of silver / palladium alloy (Ag / Pd) powder or the like on the surface side 1a of an elongated heat-resistant / electrically insulating substrate 1 made of alumina (Al ₂ O ₃ ) ceramics. ), A paste prepared by kneading with an organic binder is printed, applied and fired to form an elongated strip-like thick resistive heating element 2, and silver or silver / platinum (Ag) is formed on both ends of the resistive heating element 2. A film made of a good conductor such as a Pt alloy or silver / palladium alloy (Ag / Pd) is formed to form a pair of power supply terminal portions 3a and 3b, and the outer surface of the resistance heating element 2 is made of glass. The overcoat layer 4 is used to improve mechanical strength such as wear resistance and impact resistance, protect against corrosion from sulfidation and oxidation, and electrically insulate the pressure roller and the like.
[0004]
As shown in FIG. 7, the fixing device of the copying machine has the plate-like heater H and the pressure roller 5 facing each other in parallel, and a heat-resistant elastic material on the surface of the pressure roller 5 having a rotation shaft. The roller portion configured as described above and the overcoat layer 4 of the plate heater H are in direct elastic contact with each other directly or indirectly through the annular endless heat-resistant sheet 6. When the copy paper P is supplied from the entrance side in between the endless heat-resistant sheet 6 of the plate heater H and the pressure roller 5, the copy paper P is over the heater H by the rotation of the pressure roller 5. The toner T on the copy paper P is heated and melted by the heat of the heater H while being slid on the coat layer 4 through the heat-resistant sheet 6, and is fixed on the paper P and discharged from the outlet side out. It has become so.
[0005]
However, when the toner T is melted, stickiness is generated, so that there is a possibility that the paper P adheres to the heat-resistant sheet 6 at the outlet side out and is wound on the heater H side.
[0006]
Therefore, in the conventional heater H, as shown in FIG. 6, an inclined surface 1 b that is lowered to the right is formed on the surface of the exit side out of the substrate 1, and an overcoat layer 4 is formed on the inclined surface 1 b by screen printing. By forming, an inclined surface 4a that falls to the right is formed at the exit end of the overcoat layer 4, and the paper P on the exit out and the outer surface of the overcoat layer 4 are interposed via the heat-resistant sheet 6. By reducing the contact area, the separation between the heat-resistant sheet 6 and the paper P, that is, the paper discharge performance is improved.
[0007]
[Problems to be solved by the invention]
However, in such a conventional heater H, as shown in FIG. 6, the inclined surface 1 b that is lowered to the right of the exit side out end portion of the substrate 1 is formed by polishing. Since it is difficult to obtain dimensional accuracy, there is a problem that the paper discharge effect is not always good.
[0008]
Accordingly, the present invention has been made in view of such circumstances, and an object of the present invention is to provide a plate heater, a fixing device, and an image forming apparatus which are improved in paper separation property with a simple configuration.
[0009]
[Means for Solving the Problems]
The present invention is configured as follows to solve the above-described problems.
[0010]
The invention according to claim 1 of the present application covers a substrate made of a heat-resistant electrical insulating material, a strip-like resistance heating element formed on one flat surface of the substrate, and an outer surface of the resistance heating element. A coating layer that is formed on a flat surface of the substrate so as to be electrically insulated, and that transfers heat generated by the resistance heating element to a moving heated object; The coating layer edge on the entry side in the moving direction of the heated body with the pressure roller that is rotatably contacted with the layer and moves the heated body on the overcoat layer, the edge of the resistance heating element, and the substrate By laminating a plurality of overcoat layers with different coat patterns between the edge portions and screen printing, while forming on the steep slope, the coat layer edge portion on the exit side in the moving direction of the heated body, Coat between the edge of the resistance heating element and the edge of the substrate By by laminating a plurality of overcoat layers with different turn screen printing, characterized in that formed on the gentle slope than the entering-side edge.
[0012]
The invention according to claim 2 of the present application is the plate heater according to claim 1 , wherein the steep slope edge and the gentle slope edge of the plate heater have an entry side and an exit side in the moving direction of the object to be heated. A rotatable pressure roller is arranged so as to face each other.
[0013]
Further , the invention according to claim 3 of the present application is characterized by including the fixing device according to claim 2 .
[0014]
[Action]
If the steep slope edge of the coat layer is the entrance end of the heated object, such as paper, and the gentle slope edge is the exit end, the entrance side of the coat layer is connected to the steep slope of the coat layer and the surrounding area. The object to be heated is inserted between the pressure roller and guided by a steep slope, and the insertion becomes smooth and the area where the object to be heated and the coat layer are in direct or indirect contact increases. The preheating region of the object to be heated can be made long.
[0015]
On the other hand, since the exit end of the coat layer is a gentle slope, the direct or indirect contact area between the coat layer and the heated object is reduced on the exit side, and the heated object is quickly separated from the coat layer. Since the toner is naturally cooled and solidifies quickly, the adhesiveness of the toner is drastically reduced, and the separation from the heated object, that is, the paper dischargeability is improved.
[0016]
In addition, since the inclined surface is not formed on the substrate, the work of polishing the substrate to form the inclined surface can be omitted, and the workability of forming the substrate can be improved.
[0017]
【Example】
Embodiments of the present invention will be described below with reference to FIGS. 1 to 4, the same or corresponding parts are denoted by the same reference numerals.
[0018]
FIG. 1A is a cross-sectional view taken along the line II of FIG. 2, and FIG. 2 is a plan view of an embodiment of a plate heater according to the present invention. On the surface 12a of the elongated substrate 12 having a length of about 300 mm, a width of about 8 mm, and a thickness of about 0.6 to about 1 mm made of an insulating material such as alumina (Al ₂ O ₃ ) ceramics, its longitudinal direction A strip-shaped resistance heating element 13 mainly composed of silver / palladium (Ag / Pd) alloy, nickel / tin (Ni / Sn) alloy or the like having a length of about 230 mm, a width of about 2 mm, and a thickness of about 10 μm is formed. is doing.
[0019]
At both ends of the resistance heating element 13, wide silver (Ag), platinum (Pt), gold (Au), silver / platinum (Ag / Pt) alloy, silver / palladium (about 15 mm long and about 6 mm wide) A pair of power supply terminal portions 14a and 14b made of a good conductor film mainly composed of an Ag.Pd) alloy or the like are formed in an overlapping manner.
[0020]
Further, on the surface 12a of the substrate 12, a glass having a layer thickness of 70 to 100 μm made of glass powder or the like so as to cover almost the entire surface excluding the pair of power supply terminal portions 14a and 14b and both ends in the longitudinal direction of the substrate 12. A quality overcoat layer 15 is formed.
[0021]
As shown in FIG. 1, the overcoat layer 15 is slid directly or indirectly from the entry side in to the exit side out on the upper surface in the drawing, such as copy paper. In addition, the toner image T attached to one surface of the paper P by the heat generated by the resistance heating element 13 is heated to fix the toner image T to the paper P.
[0022]
Then, as shown in FIG. 1B, the overcoat layer 15 is formed on the steep slope 15a by raising its in-side end surface from the surface 12a of the substrate 12 at a steep angle α (for example, about 30 °). The outlet-side end face is lowered at a small angle β (for example, about 15 °) to form a gentle slope 15b.
[0023]
As an example of a method of forming these slopes 15a and 15b, there is a method of changing the coat pattern of each layer when the overcoat layer 15 is formed by laminating a plurality of layers by screen printing.
[0024]
FIG. 3 shows a fixing device 21 in which the plate heater 11 constructed as described above is assembled. This fixing device 21 has a heat resistant elastic material such as a heat resistant elastic material on the outer surface of a cylindrical roller body 23 provided with rotating shafts 22 protruding from both end surfaces in the axial direction. The pressure roller 25 is formed by fitting the silicone rubber layer 24.
[0025]
The pressure roller 25 has the plate heater 11 arranged in parallel so as to face the rotating shaft 22, and the plate heater 11 is attached to a base (not shown).
[0026]
An annular endless heat-resistant sheet 26 such as polyimide resin is wound around the base including the plate heater 11, and the outer surface of the overcoat layer 15 directly above the resistance heating element 13 is the heat-resistant sheet 26. Is in elastic contact with the silicone rubber layer 24 of the pressure roller 25.
[0027]
The plate heater 11 is energized through an elastic connector (not shown) made of a phosphor bronze plate or the like in contact with the power supply terminal portions 14a and 14b, and is heated on the overcoat layer 15 of the resistance heating element 13 that generates heat. The copy paper P on which the toner image T is formed is heated by the plate heater 11 between the outer surface of the provided heat-resistant sheet 26 and the silicone rubber layer 24, whereby the unfixed toner image T is melted and the copy paper P Has been established.
[0028]
That is, on the copy paper P entrance side in of the pressure roller 25, the unfixed toner image T on the copy paper P is first heated and melted by the plate heater 11 through the heat-resistant sheet 26, and at least the surface portion has a high melting point. Superbly softens and melts. Thereafter, at the copy paper P exit side out of the pressure roller 25, the copy paper P is separated from the plate heater 11, the toner image T is naturally radiated and cooled and solidified again, and the heat-resistant sheet 26 is also separated from the copy paper P. The
[0029]
Thus, after the toner image T is once completely softened and melted, it is cooled and solidified again at the paper exit side out of the pressure roller 25, so that the condensing force of the toner image T is very large.
[0030]
Then, since the overcoat layer 15 is a steep slope 15a as shown in FIGS. 1A and 1B at the paper entrance side in of the plate heater 11, the copy side is copied at the entrance side in as shown in FIG. While the leading end of the paper P is guided by the steep slope 15a, the paper P is smoothly inserted between the heat-resistant sheet 26 outside the steep slope 15a and the pressure roller 25. At the insertion end, the resistance heating element 13 is inserted. Is preheated quickly through the overcoat layer 15 and the heat-resistant sheet 26 due to the heat generated from the sheet, and gradually heated as the copy sheet P moves to the outlet side out.
[0031]
That is, immediately after the entry side end surface 15a of the overcoat layer 15 rises from the surface 12a of the substrate 12 at a steep angle, the copy paper P is brought into contact with the copy paper P via the heat-resistant sheet 26, so that the preheating area of the copy paper P can be increased. Therefore, preheating and heating can be sufficiently performed accordingly.
[0032]
On the other hand, since the overcoat layer 15 falls on the gentle slope 15b at the exit side out of the copy paper P, the copy paper P is quickly separated from the heat-resistant sheet 26 , and the toner image T is quickly cooled and solidified by natural heat dissipation. As a result, the adhesiveness of the toner can be drastically reduced. For this reason, the paper separation property (paper discharge property) of the outlet side out of the overcoat layer 15 is improved.
[0033]
FIG. 4 shows the configuration of an electronic copying machine 31 incorporating the fixing device 21 configured as described above. The copying machine 31 is a document placing table made of a transparent member such as transparent glass provided on the upper surface of a housing 32. The document 34 is scanned by reciprocating 33 in the direction of the arrow in the figure.
[0034]
A light irradiating lamp 35 is provided in the upper portion of the housing 32, and the reflected light beam from the original 34 irradiated by the lamp 35 is slit-exposed on the photosensitive drum 37 by the short focus small diameter imaging element array 36. The The photosensitive drum 37 is coated with, for example, a zinc oxide photosensitive layer or an organic semiconductor photosensitive layer, and rotates in the direction of the arrow.
[0035]
The charger 38 uniformly charges the photosensitive drum 37. The photosensitive drum 37 charged by the charger 38 has an electrostatic image subjected to image exposure by the imaging element array 36. Is formed. This electrostatic image is visualized by using toner made of a resin that softens and melts when heated by the developing device 39.
[0036]
On the other hand, the copy paper P stored in the cassette 40 is fed by a pair of conveying rollers 42 which are rotated in pressure contact with each other in a vertical direction so as to synchronize with the feeding roller 41 and the image on the photosensitive drum 37. Then, it is fed onto the photosensitive drum 37. Then, the toner image T formed on the photosensitive drum 37 by the transfer discharger 43 is transferred onto the copy paper P.
[0037]
Thereafter, the copy sheet P that is separated from the photosensitive drum 37 is guided to the fixing device 21 by the conveyance guide 44, and after being heated and fixed, is discharged to the tray 45. After the toner image is transferred, the residual toner on the photosensitive drum 37 is removed by the cleaner 46.
[0038]
The fixing device 21 has an effective length corresponding to the width (length) of the maximum size paper that can be copied by the copying machine 31 in the direction orthogonal to the moving direction of the copy paper P, that is, the width (length) of the maximum size paper. A plate-like heater 11 in which a long resistance heating element 13 (see FIGS. 1 and 2) is extended is arranged, and is sent between the plate-like heater 11 and the pressure roller 25 via a heat-resistant sheet 26. The unfixed toner image T on the copy paper P is melted by receiving heat from the resistance heating element 13, and a copy image of characters, alphanumeric characters, drawings, etc. appears on the copy paper P surface.
[0039]
In such a copy image by the fixing device 21, the resistance heating element 12 is continuously formed in an elongated shape over the length (width) of the maximum size sheet allowed by the copying machine 31, and is almost uniform in the extending direction. A clear temperature distribution is obtained, and on the copy paper P, a clear and high-quality copy having the same contrast with no transfer unevenness over the entire surface is obtained.
[0040]
Further, as described above, since the fixing device 21 has good insertion property and paper separation property of the copy paper P, paper jams can be reduced or prevented.
[0041]
Note that the present invention is not limited to the above-described embodiment. For example, the material of the substrate 12 of the plate heater 11 is not limited to alumina (Al ₂ O ₃ ) ceramics, and other materials such as ceramics, glass, and polyimide resin are heat resistant. A highly synthetic resin member may be used.
[0042]
Further, the formation of the overcoat layer 15 covering the resistance heating element 12 and the substrate 11 is not essential, and even when this is formed, the material of the glass is not limited to that of the embodiment, Needless to say, it can be selected appropriately according to the situation of use.
[0043]
【The invention's effect】
As described above, in the present invention, when the steep slope edge of the coat layer is the entrance end of the heated body such as paper, and the gentle slope edge is the exit end thereof, on the entrance side of the coat layer, Between the steep slope and the pressure roller that directly or indirectly circumscribes the steep slope, the heated body is guided by the steep slope and inserted, and the insertion is smooth and the heated body and the coat layer are directly connected. Or since the area which contacts indirectly increases, the preheating area | region of a to-be-heated body can be taken long.
[0044]
On the other hand, since the exit end of the coat layer is a gentle slope, the direct or indirect contact area between the coat layer and the object to be heated is reduced on the exit side, and the object to be heated is quickly separated from the coat layer. Therefore, the separation from the heated body, that is, the paper discharge performance is improved.
[0045]
In addition, since the inclined surface is not formed on the substrate, the work of polishing the substrate to form the inclined surface can be omitted, and the workability of forming the substrate can be improved.
[Brief description of the drawings]
FIGS. 1A and 1B are cross-sectional views taken along line II of FIG.
FIG. 2 is a plan view of an embodiment of a plate heater according to the present invention.
FIG. 3 is a longitudinal sectional view of a fixing device including the plate heater shown in FIG.
4 is a longitudinal sectional view of a copying machine equipped with the fixing device shown in FIG. 3. FIG.
FIG. 5 is a plan view of a conventional plate heater.
6 is a sectional view taken along line VI-VI in FIG.
7 is a longitudinal sectional view of a fixing device including the conventional plate heater shown in FIG. 5 and the like.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 Plate heater 12 Board | substrate 12a Board | substrate surface 13 Resistance heating element 14a, 14b Power supply terminal part 15 Overcoat layer 15a Incoming side steep slope 15b Outlet side gentle slope 21 Fixing device 22 Rotating shaft 23 Roller body 25 Rotating plug roller 31 Copying machine 35 Lamp 36 Imaging element array 37 Photosensitive drum P Copy paper T Toner image

Claims (3)

A substrate made of a heat-resistant electrical insulating material;
A belt-like resistance heating element formed on one flat surface of the substrate;
A coating layer formed on a flat surface of the substrate so as to cover and electrically insulate the outer surface of the resistance heating element, and to transfer heat generated from the resistance heating element to a moving heated object; Comprising
The coating layer edge on the entry side in the moving direction of the heated body with the coating layer and a pressure roller that is rotatably contacted with the coating layer and moves the heated body over the overcoat layer is formed on the resistance heating element. By laminating a plurality of overcoat layers with different coating patterns between the edge and the edge of the substrate, screen printing is performed to form a steep slope, while the heating target exits in the moving direction. By laminating a plurality of overcoat layers with different coat patterns between the edge of the resistance heating element and the edge of the substrate and screen printing the coat layer edge from the entrance edge A plate heater characterized by being formed on a gentle slope.   The plate-shaped heater according to claim 1 is opposed to a rotatable pressure roller so that the steep slope edge and the gentle slope edge of the plate heater are on the entry side and the exit side in the moving direction of the heated object. A fixing device characterized by being arranged.   An image forming apparatus comprising the fixing device according to claim 2.

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