JPH0916009A - Heater and fixing device as well as image forming device - Google Patents

Abstract

PURPOSE: To provide a heater with which the power feed from one end are possible with simple constitution and for which miniaturization is made possible, a fixing device as well as an image forming device. CONSTITUTION: This heater H has a cylindrical base body 1 consisting of an electrically insulating material formed with a through-hole 11, a resistance heating element film 2 formed on the outer peripheral surface 1A of this base body 1 and terminals 5 for power feeding of which at least one among the plural terminals electrically connected to this resistance heating element film 2 are formed on the inner peripheral surface 1B at the end of the base body 1. This fixing device D is fitted with this heater H. This image forming device P is equipped with the fixing device D. As a result, there are no conductive parts and projections exposed on the outside surface of the cylinder heater H and the safety is enhanced. In addition, the miniaturization is made possible, the wirings are simplified and the power feeding at the single end is made possible. The electric circuits are surely shut off by destroying the base body of the heater H in the event of the occurrence of abnormality, by which the firing by overheating, etc., are prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heater used in, for example, toner fixing and heating devices and heating devices in OA equipment, a fixing device using the heater, and an image forming apparatus having the fixing device.

[0002]

2. Description of the Related Art In an electronic copying machine, for example, a copy paper on which a toner image is formed is passed while being pinched between a roll heater and a pressure roller, and the heat of the heater heats the copy paper to fuse the toner. I am trying to fix it.

As the above-mentioned roll heater, a long halogen light bulb is used as a heating source inside a cylindrical heating cylinder made of aluminum on which a fluorine resin coating having heat resistance and elasticity such as Teflon (registered trademark) is formed. Is used. Then, the fixing device opposes a roll heater and a pressure roller having a rotation axis parallel to the heater and rotates them in opposite directions to turn on the halogen bulb and heat the heating cylinder by the radiant heat of the bulb. Is used as a heater. When the copy paper is supplied between the roll heater and the pressure roller, the toner is heated by the heat of the roll heater and the pressure between the heater and the pressure roller so that the toner is fused and fixed on the copy paper. Has become.

However, since this roll heater heats the heating cylinder by the radiant heat of the halogen bulb, it takes time to warm up the heating cylinder to a predetermined temperature, which causes poor start-up characteristics and large heat loss, resulting in poor efficiency. There was a problem. Further, since the halogen bulb uses a filament coil, it sometimes breaks.

Therefore, instead of such an indirectly heating halogen bulb, a roll heater in which a film-like resistance heating element having a high thermal efficiency, which comes into direct contact with copy paper, is formed on the surface of the roller has been developed and put into practical use. Has been converted.

This roll heater is disclosed in, for example, Japanese Patent Laid-Open No. 63-
It is described in Japanese Patent No. 158583. This heater has a thin resistance heating element film such as nickel formed on the outer surface of a cylindrical heating tube formed by electrically insulating the surface of ceramic or metal, and has a fast temperature rising time and good rising characteristics. It has the advantage that it requires less power and is highly efficient.

[0007]

However, Japanese Patent Application Laid-Open No.
The heater described in Japanese Patent No. 158583 has a power feeding portion to the resistance heating element film at both ends of a long heating cylinder. With such a configuration, the heater becomes longer and a power feeding portion in a fixing device or the like. There is a problem that the power supply line to is separated into two places and the wiring becomes complicated. In addition, it is necessary to dispose a temperature detecting sensor or the like, a protection circuit component, etc. in the vicinity of such a heater, but it is difficult to secure a space and wiring of the component wiring is similar to the above. It was sometimes complicated and troublesome. In addition, there is a problem that the device becomes large in size to store them together.

Further, when a conductive wire or the like is exposed on the outer peripheral surface of the rotating heater in the fixing device, the skewed copy paper comes into contact with the conductive wire or the like to cause a break in the conductive wire or the like, thereby acting as a heater. It may not be done. Further, depending on the size of the copy paper, the energization range to the resistance heating element film may be changed to prevent the unnecessary portion from generating heat.

In addition, in electrical equipment, except for special ones in consideration of space, price, commonality with other parts and safety, usually, voltage and current control lower than the rated input voltage to the equipment is performed. Is designed and assembled so that various parts that operate according to can be used. This is the same in the above copying machine as well, and the roll heater for fixing is used by limiting the voltage or current lower than the voltage supplied to the copying machine.

Recently, however, diversification of equipment has been desired, and when controlling voltage and current, there are cases where electronic components increase due to complicated circuits, and the probability of occurrence of troubles such as accidents increases accordingly. Is coming. of course,
Electrical equipment is designed to deal with various accidents, and when such accidents occur, safety devices are supposed to operate.However, double or triple safety devices do not work or accidents extend to other circuits. There are also unexpected accidents that extend.

For example, in a copying machine using a roll heater as described above, if the safety device does not operate even when an overcurrent flows through the heater, energization continues and the heater may overheat, which may cause ignition. It is necessary to take measures to prevent it.

The present inventor can supply power from the inside of the substrate in a roll heater and the like, and can also supply power from one end with a simple structure, which can downsize the fixing device and the like, and when an overcurrent flows to the heater, it is overheated. In order to prevent ignition due to overheating, the power supply to the heater is forcibly stopped.

[0013]

A heater according to claim 1 of the present invention comprises a cylindrical base made of an electrically insulating member, a resistance heating element film formed on the outer peripheral surface of the base, and At least one of the plurality electrically connected to the resistance heating element film is provided with a power supply terminal formed on the inner peripheral surface of the end portion of the base body.

A heater according to a second aspect of the present invention is a cylindrical base body made of an electrically insulating member having a through hole formed therein, a resistance heating element film formed on an outer peripheral surface of the base body, and At least one of a plurality of wiring conductor films electrically connected to the resistance heating element film and extending to the inner peripheral surface of the end portion of the substrate and a plurality of wiring conductor films connected to the wiring conductor film is It is characterized by including a power supply terminal formed on the inner peripheral surface of the end portion of the base body.

A heater according to a third aspect of the present invention is characterized in that a glassy protective coating is formed on the surface of the resistance heating element film.

In the heater according to claim 4 of the present invention, a power feeding conductor connected to the resistance heating element film and the power feeding terminal is provided on the inner peripheral surface of the base, and all the power feeding terminals are provided on one end side of the base. Is formed.

In the heater according to claim 5 of the present invention, a plurality of power supply terminals connected to the resistance heating element film are formed on the inner peripheral surface of the base body at intervals in the longitudinal direction of the base body. Is characterized by.

The heater according to claim 6 of the present invention is characterized in that the resistance heating element film is a film having a resistance value higher than that of the power supply terminal.

The heater according to claim 7 of the present invention is characterized in that the through hole formed in the base has a lower strength than other portions.

The heater according to claim 8 of the present invention is characterized in that a conductive film for connection for electrically connecting the resistance heating element film and the power supply terminal is formed in the through hole of the substrate. There is.

The heater according to claim 9 of the present invention is characterized in that the conductive film for connection formed in the through hole is a film having a higher resistance value than the film of the resistance heating element film.

The heater according to claim 10 of the present invention is characterized in that a conductor film for wiring is formed in the vicinity of the through hole.

A heater according to claim 11 of the present invention is characterized in that a wiring conductor connected to a sensor for detecting the temperature of the base is provided on the inner peripheral surface of the base.

A heater according to a twelfth aspect of the present invention is characterized in that cap-shaped members electrically connected to the resistance heating element film are provided at both ends of the base in the longitudinal direction.

A heater according to a thirteenth aspect of the present invention is characterized in that the cap-like member provided at the end of the base has a plurality of conductive terminals coaxially insulated from each other.

A heater according to a fourteenth aspect of the present invention is characterized in that a cap-like object provided at an end portion of the base body is a support shaft forming an electrical connection portion.

The fixing device according to claim 15 of the present invention is
A heater according to any one of claims 1 to 14, and a rotatable pressure roller that has an axial direction along a supporting axial direction of the heater and that is provided facing the heater. It is characterized by that.

An image forming apparatus according to a sixteenth aspect of the present invention is characterized by including the fixing device according to the fifteenth aspect and a housing for accommodating the fixing device.

[0029]

According to the invention described in claim 1, since electric power is supplied to the resistance heating element film from the inside of the base body, there is no conductive portion or protrusion exposed on the outer surface except the supporting portion at the end of the heater, which is safe. high. In addition, wiring can be simplified in a device equipped with a heater.

According to the invention described in claim 2, in addition to the function of claim 1, when the heater is overheated due to the occurrence of an abnormality, the strength is increased due to the distortion during drilling and the distortion due to the thermal expansion of the substrate. A crack is formed in the weakened through hole or in the vicinity of this hole, and this breaks the electric circuit to stop energizing the heater.

According to the third aspect of the present invention, even if heat is absorbed by the copying paper in the fixing device, for example, the heater and the copying paper have high adhesion, and the heater also accompanies the transportation of the copying paper. Since it rotates reliably, there is no partial temperature drop. Further, since it is made of glass, no static electricity is generated between it and the copy paper, it is possible to prevent the protective film and the copy paper from coming into close contact with each other, and the fixing is performed accurately to improve the quality.

Further, according to the invention described in claim 4, the heater can be a one-terminal type heater, and the electric wiring can be simplified.

According to the fifth aspect of the invention, the electric terminal can be easily taken out from the intermediate portion of the resistance heating element film, and the length of the heating section can be changed.

According to the sixth aspect of the invention, the temperature of the power supply terminal is lower than that of the resistance heating element film during energization, and the terminal functions as an electrical connecting portion.

Further, according to the invention of claim 7, the through hole portion which is perforated is weak in strength because the strain during processing and the strain due to the thermal expansion of the substrate remain, and it is the weakest among the substrates. It is a fragile portion, and when a thermal shock such as a temperature rise is applied to the vicinity of this portion due to an abnormality or the like, a crack is generated and the substrate can be broken to interrupt the electric circuit.

According to the eighth aspect of the present invention, it is possible to connect the resistance heating element film and the power supply terminal to each other without energizing them outside the substrate.

Further, according to the invention of claim 9, the connecting conductor film formed in the through hole has a higher resistance value and is higher than the temperature rising temperature of the resistance heating element film, and the film has an abnormally high current. When a current flows, a crack can be generated in the through hole portion, which is weak in strength, and the substrate can be destroyed to interrupt the electric circuit.

According to the tenth aspect of the present invention,
When an abnormally high current flows through the conductor film for wiring near the through-hole, the conductor film for wiring abnormally heats up, causing cracks in the through-hole that is weak in strength and destroying the substrate to interrupt the electric circuit. be able to.

According to the eleventh aspect of the present invention,
Wiring of the detection circuit by the sensor can be simplified and its electrical extraction can be facilitated.

According to the twelfth aspect of the present invention,
The cap-shaped material at the end of the heater forms an electrical connection to the resistance heating element film.

According to the thirteenth aspect of the present invention,
Since the cap-like material at the end of the heater has a plurality of electrically conductive terminals having one or more poles and can supply power to a plurality of portions of the formed resistance heating element film, it is possible to change the heating length and other ranges.

According to the fourteenth aspect of the present invention,
The cap-like material at the end of the heater serves as an electrical connection to the resistance heating element film and also has a function as a support for equipment and the like.

According to the fifteenth aspect of the present invention,
Since the heater according to any one of claims 1 to 14 and the pressure roller provided to face the heater are provided, the operation according to any one of claims 1 to 14 is achieved.

Further, according to the sixteenth aspect of the present invention, since the fixing device according to the fifteenth aspect and the housing for accommodating the fixing device are provided, the corresponding actions are exhibited.

[0045]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the heater of the present invention will be described below with reference to the drawings. 1 is a front view of the heater H, and FIG. 2 is FIG.
FIG. 3 is an enlarged cross-sectional front view of the left and right end portions of FIG.
It is an expanded sectional side view of the portion cut along the A line. In the figure, 1 is a heat resistant / electrically insulating material such as alumina (Al ₂
O ₃ ) Ceramic base having a length of about 360 mm, an outer diameter of about 15 mm and an inner diameter of about 11 mm, 11
L and 11R are through holes with a diameter of about 0.4 mm formed through the inside and outside of the base 1 near the end thereof. Further, 2 is the outer peripheral surface 1A of the base 1 and the through hole 11.
Resistance heating element films formed on the outer peripheral surface 1A of L and 11R, 3
Is a vitreous protective film formed to cover the resistance heating element film 2, and 4 is a connection formed from the inner wall surface of the through holes 11L and 11R on the inner peripheral surface 1B side to the inner peripheral surface 1B around the opening. A portion of the inner peripheral surface 1B of the conductor film constitutes power feeding terminals 5L and 5R. 6L and 6R are copper,
A cap-shaped support made of a metal conductor such as brass, which is inserted into the inner surfaces 1B of both ends of the base 1 and has a shaft portion 61 at its tip.
Having.

The substrate 1 is made of alumina (Al ₂
A kneaded body of O ₃ ) powder or the like is molded into a ceramic by firing, and then through holes 11L and 11R are provided at the end of the base 1 by laser processing or the like. Due to the formation of the through holes 11L and 11R, thermal processing strain remains on the base body 1 and the rigidity strength near the through holes 11L and 11R is reduced.

The resistance heating element film 2 is made of a thick film of silver-palladium (Ag.Pd) alloy or silver.
A metal paste made of a platinum (Ag.Pt) alloy or an alloy mainly composed of these is applied by screen printing on the outer peripheral surface of the substrate 1, dried, and then dried at about 850 ° C. for about 1 minute.
It is formed by firing at a high temperature for 0 minutes.
The coating film 2 has a substantially uniform film thickness of about 1 to 10 μm on the outer peripheral surface 1A of the substrate 1 without being interrupted in its rotation direction, and the sheet resistance value set to a resistance value of about 10 Ω / 100 mm is practically equal anywhere. It is formed by. On the inner wall surfaces of the through holes 11L and 11R on the outer peripheral surface 1A side, a connection conductor film 4 made of the same material as the resistance heating element film 2 and having a resistance value equal to or higher than that of the resistance heating element film 2 is formed. Has been formed.

The connecting conductor film 4 formed by being electrically connected to the resistance heating element film 2 on the inner peripheral surface 1B of the substrate 1 and the inner surfaces of the through holes 11L and 11R is electrically connected to the resistance heating element film 2 described above. Materials with lower contact electric resistance than silver (Ag), silver / platinum alloy (Ag / Pt), gold (A)
u), a metal paste such as platinum (Pt) is applied in a thick film, or the same material as the resistance heating element film 2 is applied in a thicker film than the resistance heating element film 2, and then dried and baked. Has been formed. The metal paste of the connection conductor film 4 and the resistance heating element film 2 may be applied in any order, and the firing may be performed simultaneously.

Further, the protective film 3 has lead oxide (Pb) on the surface of the resistance heating element film 2 and the end portion of the substrate 1 on the outer peripheral surface 1A side.
O) as a main component, for example, PbO (55-85 Wt
_{%) - B 2 O 3 (} 5~15Wt%) - SiO 2 (10~
30 Wt%) glass powder is applied as an insulating glass paste by screen printing to form a continuous coating film without gaps. Then, after drying, it is baked at about 700 ° C. for about 10 minutes to form a glassy layer having a thickness of 15 μm to 100 μm.

Further, the support 6L made of a cap-like material,
6R has a function as a conductive terminal member which is inserted into the inner peripheral surfaces 1B at both ends of the base body 1 and is in contact with and electrically connected to the power supply terminals 5L and 5R. Supports H and makes electrical connection from the outside. Although not shown, the supports 6L and 6R inserted into both ends of the base 1 are firmly fixed to the inner peripheral surface 1B of both ends of the base 1 by interposing a conductive adhesive in a screw or a gap. There is.

When the heater H thus constructed is energized between the supports 6L and 6R, the support 6L on the left side in FIG. 2 → the power supply terminal 5L → the conductor film 4 for connection of the through hole 11L → Left end of resistance heating element film 2 → resistance heating element film 2 → right end of resistance heating element film 2 → conductor film 4 for connecting through hole 11R → feeding terminal 5R → right support 6R (in the case of alternating current, alternate in the opposite direction for each cycle)
A current flows through the resistance heating element film 2 on the outer peripheral surface 1A of the substrate 1 to generate heat at substantially uniform temperatures in each part. In the heater H, palladium (Pd) contained in the metal alloy serves as an electric resistance element, and the resistance value of the heating element film 2 is adjusted by the ratio.

The heater H is composed of the resistance heating element film 2
By supplying power to the inside of the base body 1, there is no charging part exposed on the outer surface except the supporting part at the end of the heater H, and electrical safety and wiring can be simplified in a device equipped with the heater H. Further, as will be described later, when an overcurrent flows through the heater H and abnormal heat is generated in the vicinity of the through holes 11L and 11R, the strength of the through holes is lowered due to distortion during drilling and distortion due to thermal expansion of the substrate 1. 1
Due to the thermal shock applied to the vicinity of 1L and 11R, the base body 1 in this portion is cracked and the connecting conductor film 4 and the like are broken, whereby the electric circuit of the heater H is cut off and the resistance heating element film 2
Fever stops.

2 and 3, the dotted line of the portion facing the supports 6L and 6R shown in the substrate 1 is the through hole 1.
, 11, ..., These through holes 11, 1
The capacity of the connecting conductor film 4 (power supply terminal 5) can be increased by increasing the number of locations.
It is also possible to apply it to multiple places, and if it disconnects due to overheating at one place even if it is distributed to multiple places, the capacity will be insufficient at the remaining place and overcurrent will flow to other places, and the other places will also be disconnected. Finally, the base 1 is cracked, the electrical connection is cut off, and the heat generation can be stopped.

FIGS. 4 and 5 show a second embodiment of the heater of the present invention, FIG. 4 is an enlarged sectional front view in which the intermediate portion is omitted, and FIGS. 5 (a) and 5 (b) are B in FIG. -B line and C-
It is an expanded sectional side view of the portion cut along the C line. In the figure, those parts which are the same as those corresponding parts in FIGS. 1 to 3 are designated by the same reference numerals, and a description thereof will be omitted. The heater H of FIGS. 4 and 5 is characterized in that the power supply terminals 5 are gathered on one end side (the left side in this figure) of the base body 1 and is also called a single-terminal heater or the like. The heater H of the second embodiment has a holding member 6L also serving as a current-carrying member at one end (on the left side in this figure),
On the other end (right side in this figure), a holding body 6R (in this case, electricity is not conducted but only for supporting) is attached via a screw or a conductive adhesive (not shown).

In FIG. 4, the connecting conductor film 4 connected to the resistance heating element film 2 at the right end portion of the substrate 1 and led out from the inner wall surface of the through hole 11R is formed in a strip shape on the inner peripheral surface 1B to the left. The wiring conductor film 7 is connected to the end portion. The wiring conductor film 7 constitutes the power supply terminal 5 at the left end.

Further, the left support 6L is provided with inner and outer two-pole current-carrying terminals 63 and 64 coaxially with each other through an insulating layer 62. When the support 6L is inserted into the inner surface of the base 1, the inner support The energizing terminal 63 is brought into pressure contact with the power feeding terminal 5 in the same manner as in the first embodiment to make an electrical connection. Further, the resistance heating element film 2 is formed on the outer energization terminal 64 even on the outer peripheral surface 65 having substantially the same diameter as the base body 1, and the small diameter portion 66 connected to the outer peripheral surface 65 serves as an electrical connection portion. Power is supplied to the small diameter part 6
6 and the shaft portion 67 connected to the energizing terminal 63.

Since the heater H of this structure can be energized from one end, wiring to the heater H is easy, and a space for arranging a sensor for detecting the temperature of the heater H, a protection circuit component, and the like. In addition to the above, there is an advantage that the wiring can be easily handled because there is no wiring around as in the above case. The heater H is supported by the support members 6 at both ends.
Whether L or 6R is supported or one end is supported, electrical and mechanical support is possible in both cases. Further, when the heater H is abnormally overheated, the base 1 is broken from the through hole 11R to cut the connecting conductor film 4 and the wiring conductor film 7 to cut off the electric circuit, so that there is no risk of ignition.

FIGS. 6 and 7 show a third embodiment of the heater of the present invention, FIG. 6 is an overall schematic explanatory view, and FIG. 7 is FIG.
FIG. 3 is an enlarged sectional front view of a left end portion of FIG. In the figure, the same parts as those in FIGS. 1 to 5 are designated by the same reference numerals and the description thereof will be omitted. This third embodiment is an extension of the second embodiment, and is an energy-saving device that can generate heat only in the minimum necessary portion, for example, by changing the heat generation width of the heater H in accordance with the size of copy paper in a copying machine. It is suitable for the type.

In this example, the width corresponding to the vertical length (297 mm) of copy paper A4 is A4 mm, the width corresponding to the horizontal length of B4 size (257 mm) is B4 mm, and copy paper A5.
The width corresponding to the vertical length of the format (210 mm) is 3 mm of A5 mm.
One heater H can generate heat for various types of lengths. That is, the through hole 1 on the right side of the substrate 1
Through holes 11A, 11B, and 11L are formed at positions A5 mm, B4 mm, and A4 mm with 1R as a reference (actually, the temperature at the end of the heater H is lower, which is longer than this).

Then, the connecting conductor films 4, 4 (1) are formed on the inner peripheral surfaces 1B of the openings of the through holes 11A and 11B on the left side.
The 1B side is not shown. ) Is formed, and wiring conductor films 7 and 7 (11B side is not shown) are continuously provided on the connection conductor films 4 and 4 and are provided on the inner peripheral surface 1B toward the left end portion. There is. The power supply terminals 51, 52, 53 (5) are provided on the left end portion of the wiring conductor films 7, 7 (11B side is not shown) and the opening inner peripheral surface 1B of the through hole 11L.
3 is not shown. ) Is formed. Then, a support 6L having a multi-coaxial structure, which insulates the energizing terminals 65, 67 and 68 as shown in the second embodiment, is inserted into the left end portion, and the power feeding terminal 51 is the energizing terminal 67. The power supply terminal 52 is electrically connected to the power supply terminal 68, and the power supply terminal 53 (not shown) is electrically connected to the power supply terminal 65. A support 6R as shown in the first embodiment is inserted at the right end. The heater H is supplied through the through hole 1 if a voltage is supplied between the right support 6R and the left support 6L.
It is possible to generate heat in the entire A4 mm width portion between 1R and 11L. Further, if a voltage is supplied between the right end support 6R and the left end support 6L of the current-carrying terminals 68, the B4 mm wide portion between the through holes 11R and 11A can be heated.

The heater H whose heat generation length can be switched is used in a fixing device of a copying machine or the like to save energy.
Also, this heater H is also connected from the through hole 11R at the right end to the current-carrying terminal of the support 6L at the left end via the wiring conductor film 7, and the one end side of the base 1 (left side in this figure).
It is also possible to use a single-terminal type heater in which current-carrying terminal portions are collected. Further, when the heater H also abnormally overheats, the base body 1 breaks from the through hole 11R portion and disconnects the electric circuit in the same manner as described above, so that there is no fear of ignition.

FIGS. 8 and 9 are enlarged sectional front views showing the essential parts of another embodiment of the heater of the present invention. In the figure, those parts which are the same as those corresponding parts in FIGS. 1 to 7 are designated by the same reference numerals, and a description thereof will be omitted. While the resistance heating element film 2 or the connecting conductor film 4 is formed in the through hole 11 in the above-described embodiment, this embodiment is characterized in that the through hole 11 having no conductor is provided. It is a thing.

That is, the through holes 11, 11 are provided in the vicinity of the conductor film 7 for wiring formed by being connected to the conductor film 4 for connection on the inner peripheral surface 1B of the base body 1, as shown in FIG.
Are on both sides of the wiring conductor film 7. In FIG. 8, the wiring conductor film 7 is also a film having a high resistance value, and an overcurrent flows through the electric circuit of the heater H to cause abnormal heat generation, and the same film 4 as the resistance heating film 2 is formed. When the base 11 is not cracked even when the hole 11R becomes high in temperature, cracks W, W from the portions of the through holes 11, 11 having poor strength formed on both sides thereof due to the heat of the wiring conductor film 7 which also becomes high in temperature. , And so on, the substrate 1 is broken, and the wiring made of the wiring conductor film 7 is cut to disconnect the electric circuit. In addition, FIG.
8 is the same as that of FIG. 8, but the wiring from the resistance heating element film 2 to the inner peripheral surface 1B of the base 1 is formed by the connecting conductor film 4 formed through the end face of the base 1 without passing through the through holes. The conductor film 7 for wiring, which is connected to the conductor film 7 for wiring and has a higher resistance value than the resistance heating element film 2, has a high temperature and cracks W, W from the through hole 11 portion,
... is generated and the substrate 1 is broken in the same manner as described above.

Further, FIGS. 10 and 11 show an example of a fixing device D such as a copying machine or a facsimile in which the cylindrical roll heater H is incorporated, and FIG. 10 is a partial sectional front view of the main part of the fixing device D. 11 is a cross-sectional side view of a portion cut along the line EE in FIG. Since the heater H portion in the figure is the same as that in FIGS. 1 to 9 described above, the same portions are designated by the same reference numerals and the description thereof is omitted. In the figure, R is a pressure roller,
A heat resistant elastic material such as silicone rubber R3 is fitted on the surface of a cylindrical roller main body R2 having both ends thereof provided with a rotary shaft R1 protruding therefrom.

The heater H and the pressure roller R oppose the chassis S forming a part of the casing in parallel with each other in the axial direction so that the outer circumferences thereof are lightly elastically contacted in a substantially straight line. Installed. That is, mounting holes S1, S1, S2, S2 are bored in the chassis S, and conductive bearings S4 are provided in the mounting holes S1, S1 via locking members S3, S3 formed of an electrically insulating resin. , S4 are mounted, and the shaft portion 61 of the support 6 of the heater H is inserted into the through holes S5, S5 formed in the conductive bearings S4, S4.
Is rotatably fitted and attached.

The mounting holes S2, S2 of the chassis S are also provided.
Bearings S6 and S6 composed of bearings are mounted on the shafts. The rotary shaft R1 of the pressure roller R is rotatably fitted and attached to the through holes S7 and S7 of the bearings S6 and S6.

The heater H and the pressure roller R are combined with a motor and a reduction gear at a position extending to the left of the shaft portion 61 of the support 6 and the rotation axis R1 in FIG. It is connected to a source (not shown) and is driven in conjunction with it.

The fixing device D is incorporated in a copying machine and used at a commercial voltage of 100 V, for example, and the heater H is energized by controlling the current by a current controller in the copying machine. This energization is performed from the lead wires 8 and 8 through the bearings S4 and S4 formed as conductors, and through the shaft portion 61 of the support body 6 supported by the bearings S4 and S4 to the power supply terminal 5 in the same manner as above. The resistance heating element film 2 generates heat.

Then, the copy paper K is inserted between the heater H and the pressure roller R such that the surface side on which the toner T is attached faces the cylindrical heater H, and these heater H and pressure roller R are inserted. Are interlocked with each other via a power source (not shown) to rotate in opposite directions. This cylindrical heater H
Due to the heat and the pressure between the heater H and the pressure roller R, the toner T can be fused and fixed on the copy paper K, and the copy paper K is conveyed in the arrow direction.

In the fixing device D, the roll heater H for fixing directly transfers the copy paper K by heat conduction from the resistance heating element film 2.
Since it is heated, it can be heated with high thermal efficiency. Further, since the protective coating 3 on the outermost surface of the heater H is made of glass, static electricity is not generated between the protective coating 3 and the copy paper K, so that the suction action does not work and the protective coating 3 and the copy paper K are prevented from sticking to each other too much. Therefore, the copy paper K can be smoothly transported.

If, for example, an electronic component such as a semiconductor constituting the current controller is abnormal and an overcurrent has flown into the heater H, but the safety device connected to the current controller does not operate, resistance heating occurs. Body membrane 2 and through hole 1
The high resistance connecting conductor film 4 formed on the inner surfaces of the 1L and 11R is overheated. When the resistance heating element film 2 and the connecting conductor film 4 continue to be overheated, the coating 4 having the highest resistance value among the coatings of the base 1 reaches the maximum temperature, and is perforated to have the highest strength in the base 1. Cracks due to thermal shock are generated in the through-holes 11L and 11R, which are weakened.

Due to the cracks, the substrate 1 made of alumina is broken apart from the inner wall surface of the through holes 11L and / or 11R and in the vicinity thereof, and the current-carrying circuit of the resistance heating element film 2 has through holes 11L and / or 11L.
At the R part, the circuit is disconnected and the electrical connection is cut off. Therefore, heat generation from the resistance heating element 2 is stopped, and an unexpected situation such as ignition from the copying machine can be eliminated.

In an experiment conducted by the present inventors, in the heater H having the structure shown in FIG. 1, the resistance heating element film 2 having a resistance value of about 32 ohm [Ω] on the substrate 1 and the resistance values of about 0 at the through holes 11L, 11R. When a connecting conductor film 4 having a high resistance value of 0.6 [Ω / □] is formed and a rated voltage of 70 V is applied between the power supply terminals 5 and 5, a current of about 2.2 A flows and resistance heating occurs. Body membrane 2
The surface temperature of the connecting conductor film 4 was about 200 ° C. Then, the applied voltage is 80
When the voltage was increased to V, the current was about 2.5 A, the surface temperature of the resistance heating element film 2 was about 400 ° C., and the surface temperature of the connecting conductor film 4 was about 400 ° C. Further, the applied voltage is increased to 95 V, the current becomes about 3.0 A, the surface temperature of the resistance heating element film 2 is about 500 ° C., and the surface temperature of the connection conductor film 4 is about 500.
When the temperature reached ℃, the vicinity of the through hole 11R where the conductor film 4 for connection having a high resistance value was formed was cracked, the substrate 1 was disassembled, the heater H was broken, and the energizing circuit was disconnected.

Further, the fixing device D having the above structure is
It is incorporated in a copying machine P as an image forming apparatus as shown in FIG. FIG. 12 is a cross-sectional view showing a schematic configuration of the copying machine P. P1 is a housing of the copying machine P, P2 is an original placing table made of a transparent member such as glass provided on the upper surface of the housing P1 in the arrow Y direction. The original G is scanned by reciprocating.

A lamp L for irradiating light is provided above the inside of the housing P1.
Is provided, and the reflected light beam from the original G illuminated by the lamp L is slit-exposed onto the photosensitive drum P4 by the short-focus small-diameter image-forming element array P3. In addition,
The photosensitive drum P4 rotates in the arrow direction.

Further, P5 is a charger, which uniformly charges, for example, the photosensitive drum P4 coated with a zinc oxide photosensitive layer or an organic semiconductor photosensitive layer. On the drum P4 charged by the charger P5, an electrostatic image subjected to image exposure by the imaging element array P3 is formed. This electrostatic image is visualized using a toner made of a resin or the like that softens and melts when heated by the developing device P6.

On the other hand, the copy paper K stored in the cassette P7 is a pair of conveying rollers P9 which are rotated in pressure contact with each other in the vertical direction at a timing synchronized with the image on the feeding roller P8 and the photosensitive drum P4. Is sent onto the drum P4. Then, the transfer discharger P10 transfers the toner image formed on the photosensitive drum P4 onto the copy paper K. After this, the copy paper K separated from the drum P4
Is guided to the fixing device D by the transport guide P11, subjected to heat fixing processing, and then discharged onto the tray P12. In addition,
After the toner image is transferred, the residual toner on the drum P4 is removed by the cleaner P13.

The fixing device D has an effective length in the direction perpendicular to the moving direction of the copy paper K, which corresponds to the width (length) of the maximum-size paper that can be copied by the copying machine P, that is, the width (length of the maximum-size paper). A cylindrical roll heater H having a longer resistance heating element film 2 extended is arranged, and the resistance heating element film 2 is provided so as to make a light elastic contact in the extending direction of the resistance heating element film 2. A pressure roller R is provided. Then, the unfixed toner image on the copy paper K sent between the heater H and the pressure roller R is melted by receiving heat from the resistance heating element film 2, and characters, alphanumeric characters are formed on the surface of the copy paper K. Make a duplicated image of a symbol, drawing, etc. appear. In the copying machine P in which the fixing device D is assembled as described above, the fixing device D is miniaturized as described above, wiring can be simplified, and the copying machine P can be made compact. Further, even if an abnormality occurs in the heater H and the safety device does not operate and the temperature rises, cracks occur in the substrate 1 and the electric circuit is cut off, so there is no fear of ignition.

Further, since a rotatable heater can be used for the fixing device D, it is possible to prevent a partial temperature drop, and to obtain a clear high-quality copy having the same contrast without transfer unevenness over the entire surface. Further, since the copy paper K is heated by the heat conduction from the resistance heating element film 2, the copy paper K can be fixed uniformly with high thermal efficiency, and the copy paper K does not adhere too much to the copy paper K. Can be transported smoothly.

The present invention is not limited to the above embodiment,
For example, the base material is not limited to alumina ceramics,
Other ceramics, glass, a synthetic resin member having high heat resistance and electric insulation such as polyimide resin, or the like, or a material such as a metal whose surface is electrically insulated may be used. Good. An undercoat layer such as glass may be formed on the surface of the substrate.

Further, the through hole is left with thermal strain due to perforation by laser processing, etc., and the strength in the vicinity of this through hole is weakest in the vicinity of the other parts in the substrate, and the through hole may be drilled in the middle part of the substrate. In order to make the base easily cracked, it is preferable to provide a through hole near the end of the base. Further, the number of through holes is not limited to one, and a plurality of through holes may be drilled, and the shape thereof is not limited to a perfect circle, and may be a circle, a corner, or a notch with a part of which is opened at the edge. It may be. In short, it suffices that a portion having weak strength is provided by leaving a thermal strain or the like by performing processing or by providing a hole, a notch or the like and changing the state or shape with other portions.

In addition to the materials described in the above embodiments, nickel-based or ruthenium-based materials may be used for the resistance heating element film. Further, the materials for forming the connecting conductor film, the wiring conductor film, the vitreous protective film, and the like are not limited to those of the embodiment.
These materials may be appropriately selected according to the heat generation temperature and the situation of use. Further, it is desirable that the film formed on the inner wall surface of the through hole or in the vicinity of the through hole has a high resistance value equal to or higher than that of the resistance heating element film.

Further, the cap-shaped support body inserted into the end portion of the base does not have to be formed of a metal member in particular when one is not used as a current-carrying member, and the shape thereof is not limited to that shown in the drawings and is stationary. The shaft part is not necessary in the one used.

Further, a temperature detecting sensor such as a thermistor or a thermocouple and other measuring elements or circuit parts may be housed and arranged inside the substrate, and wiring for these sensors or parts may be provided. The conductor film may be formed on the inner peripheral surface of the substrate as in the resistance heating element film described above. In this case, the cap provided at the end of the base body may be similarly used for taking out the signal from the sensor or the like. Further, if a wiring conductor film is used for connection with these sensors, for example, when the wiring conductor film connected to the sensor or the like is cut without cutting the electric circuit to the resistance heating element film even if the base body is broken, From the point where detection is not possible, it is possible to know that something is wrong with the heater, and early countermeasures can be taken. further,
In the embodiment of the fixing device described above, the copy paper directly contacts the surface of the vitreous protective film, but it may be indirect contact with a plastic sheet interposed to protect the heater and smoothly feed the paper.

Furthermore, the heater of the present invention is not limited to fixing of OA equipments, but can be put to various practical uses in other fields such as heating of heating equipments and heating furnaces. Not limited to this, it can be applied to a stationary object. Further, the image forming apparatus is not limited to the copying machine and can be applied to various OA equipment.

[0086]

The heater according to the first aspect can be miniaturized by shortening the overall length of the terminals if the power supply terminals are in the base and the effective heat generation length is the same. In addition, there is no exposed charging part or protrusion on the outer peripheral surface side, which is highly safe. Wiring can be simplified in a device equipped with this heater.

A heater according to a second aspect is the heater according to the first aspect.
In addition to the effect of, when the safety device does not operate at the time of overheating,
Cracks will form in the through holes or in the vicinity of the holes that have become weaker in strength due to the boring process of the substrate or heat, and this will break the electric circuit reliably, stopping the energization of the heater and causing further heat generation and ignition. It has become possible to prevent accidents.

The heater according to the third aspect of the present invention has a high adhesion between the heater and the copy paper, enables uniform fixing with good thermal efficiency, and has the same contrast and clear high quality with no transfer unevenness over the entire surface. A copy is obtained. Further, since it is made of glass, no static electricity is generated between it and the copy paper, and there is no adsorption, so that the copy paper can be transported smoothly.

In the heater described in claim 4, since the power supply terminal is provided on one end side of the heater, the electric wiring can be simplified.

In the heater according to claim 5, the length of the heat generating portion is changed so that heat can be generated only in a necessary portion corresponding to the size of the target object to be heated, and energy is saved without wasting power. You can

In the heater according to the sixth aspect, heat generation in unnecessary portions is prevented and good electrical connection is made.

In the heater according to the seventh aspect, a weakened portion is formed in a part of the substrate by forming a punched portion having a shape different from that of another portion by punching or processing the punched portion by thermal shock when overheated. It is possible to prevent accidents such as cracking from the part, destruction of the substrate, interruption of the electric circuit and ignition.

In the heater according to the eighth aspect, since the connecting conductor is passed through the base, there is no protrusion on the outer surface of the heater.

In the heater according to the ninth aspect, the coating film that is most heated when an abnormally high current flows is formed in the through hole portion, which is weak in strength. It can be destroyed to break the electric circuit.

According to the invention described in claim 10,
Since the coating film that heats up the most when an abnormally high current flows is formed in the vicinity of the through hole, which is weak in strength, cracks occur from this hole and the substrate can be destroyed and the electric circuit can be cut off. .

In the heater according to the eleventh aspect, it is possible to easily take out a signal from the temperature sensor or the like and attach the sensor or the like, and since the heater can be housed in the base body, accurate measurement and saving of the installation space can be achieved. it can.

In the heater according to the twelfth aspect, the cap-like material serves as an electrical connection portion to the resistance heating element film.

Since the heater according to the thirteenth aspect can supply power to a plurality of locations on the resistance heating element film, the range such as the heating length can be changed so that only the necessary portion corresponding to the size of the object to be heated is heated. It is possible to save energy without wasting electric power. The heater according to claim 14,
The cap-like material is used as a support for an electrical connection part and a device to be mounted, and can be rotationally supported as well as stationary.

The fixing device according to claim 15 includes the heater according to any one of claims 1 to 14 and the pressure roller provided so as to face the heater, and therefore the fixing device according to any one of claims 1 to 14 is provided. Any one of the effects of item 14 can be exhibited.

Since the image forming apparatus according to the sixteenth aspect includes the fixing device according to the fifteenth aspect and the housing that accommodates the fixing device, it is possible to obtain the corresponding effects.

[Brief description of the drawings]

FIG. 1 is a front view showing a first embodiment of a heater of the present invention.

FIG. 2 is an enlarged sectional front view showing a part of the heater shown in FIG.

3 is a sectional side view showing a portion cut along line AA in FIG. 2. FIG.

FIG. 4 is a partially cutaway enlarged sectional front view showing a second embodiment of the heater of the present invention.

5A is a sectional side view showing a portion cut along the line BB in FIG. 4, and FIG. 5B is a sectional side view showing a portion cut along the line CC as well. Is.

FIG. 6 is an overall schematic explanatory view showing a third embodiment of the heater of the present invention.

FIG. 7 is an enlarged sectional front view of the left end portion of FIG.

FIG. 8 is an enlarged sectional front view showing a main part of another embodiment of the heater of the present invention.

FIG. 9 is an enlarged sectional front view showing a main part of another embodiment of the heater of the present invention.

FIG. 10 is a partial cross-sectional front view showing a main part of an embodiment of the fixing device of the present invention.

11 is a cross-sectional side view showing a portion cut along line EE in FIG.

FIG. 12 is a sectional view showing a schematic configuration of a copying machine represented by an image forming apparatus of the present invention.

[Explanation of symbols]

 H: Heater 1: Base 1A: Outer peripheral surface 1B: Inner peripheral surface 11, 11A, 11B, 11L, 11R: Through hole 2: Resistance heating element film 3: Protective coating 4: Connection conductor film 5: Power supply terminals 6, 6L , 6R: Cap-shaped support 61: Shaft 65, 67, 68: Current-carrying terminal 7: Conductor film for wiring D: Fixing device R: Pressure roller K: Copy paper P: Copy machine

Claims (16)

[Claims] 1. A cylindrical base body made of an electrically insulating member; a resistance heating element film formed on an outer peripheral surface of the base element; and at least one of a plurality of electrically connected to the resistance heating element film. And a power supply terminal formed on the inner peripheral surface of the end portion of the base body. 2. A cylindrical base body made of an electrically insulating member having a through hole formed therein; a resistance heating element film formed on an outer peripheral surface of the base element; electrically connected to the resistance heating element film. A conductor film for wiring formed to extend to the inner peripheral surface of the end portion of the base; and at least one of a plurality of conductor films connected to the conductor film for wiring is formed on the inner peripheral surface of the end portion of the base body. And a power supply terminal; 3. The heater according to claim 1, wherein a vitreous protective coating is formed on the surface of the resistance heating element film. 4. A power supply conductor connected to a resistance heating film and a power supply terminal is provided on the inner peripheral surface of the base, and all the power supply terminals are formed on one end side of the base. The heater according to claim 1 or 2. 5. A plurality of power supply terminals connected to the resistance heating element film are formed on the inner peripheral surface of the base body at intervals in the longitudinal direction of the base body. The heater according to any one of 4 above. 6. The resistance heating element film is a film having a resistance value higher than that of the power feeding terminal.
The heater according to any one of 1. 7. The heater according to claim 2, wherein the through hole formed in the substrate has lower strength than other portions. 8. The connection conductor film for electrically connecting the resistance heating element film and the power supply terminal to each other is formed in the through hole of the base body. The heater described in Kaichi. 9. The heater according to claim 8, wherein the connection conductor film formed in the through hole is a film having a higher resistance value than the film of the resistance heating element film. 10. The heater according to claim 2, wherein a conductor film for wiring is formed in the vicinity of the through hole. 11. The heater according to claim 1, wherein a wiring conductor connected to a sensor for detecting the temperature of the base is provided on the inner peripheral surface of the base. . 12. The cap-shaped object electrically connected to the resistance heating element film is provided at both ends of the base in the longitudinal direction, as claimed in any one of claims 1 to 11. heater. 13. The heater according to claim 12, wherein the cap-shaped member provided at the end of the base has a plurality of conductive terminals that are coaxially insulated from each other. 14. The heater according to claim 13, wherein the cap-like object provided at the end of the base body is a support shaft that forms an electrical connection portion. 15. A heater according to claim 14; and a rotatable pressure roller which has an axial direction along a supporting axial direction of the heater and is provided facing the heater. Characterizing fixing device. 16. An image forming apparatus comprising: the fixing device according to claim 15; and a housing that houses the fixing device.