JPH0996982A - Fixing heater, fixing device, and image forming device - Google Patents

Abstract

(57) Abstract: By disposing an electrode of a resistance heating element on only one side of a roller base body, it is possible to achieve both simplification of the structure of power supply means for supplying power to this electrode and reduction in size and weight. A cylindrical or columnar metallic roller base body 12
An electric insulating layer 13 covering the outer surface of the metal roller base 12 with a heat-resistant electric insulating material; a resistance heating element 14 formed on the outer surface of the electric insulating layer 13;
An annular electrode 15 formed on one axial end of 3 and electrically connected to the resistance heating element 14; at least an insulating layer in the film thickness direction at the other axial end opposite to the annular electrode 15. A through hole 17 penetrating therethrough to electrically connect the resistance heating element 14 to the metal roller base 12;

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a roller-type fixing heater suitable for use in small equipment such as office automation equipment, household electric equipment and precision manufacturing equipment, and a copying machine equipped with this fixing heater. The present invention relates to a fixing device used for fixing a toner such as a facsimile and an image forming apparatus using the fixing device.

[0002]

2. Description of the Related Art Generally, in an electronic copying machine, a copy sheet on which a toner image is formed is passed between a fixing heater and a pressure roller while directly or indirectly through a heat-resistant sheet while pressing the fixing sheet. It is equipped with a fixing device that heats, melts, and fixes the toner on the copy paper by the heating of.

As a conventional fixing device of this type, there is, for example, a roller type disclosed in Japanese Patent Laid-Open No. 1-157083. This type of roller type fixing heater is shown in a partial vertical sectional view of FIG. 6 and a sectional view taken along line VII-VII of FIG. The entire outer surface is covered with a ceramic layer 2 such as alumina, and a resistance heating element 3 is concentrically formed on the outer surface of the ceramic layer 2. The ring-shaped electrodes 4a and 4b are integrally or integrally formed by, for example, pattern printing of Ag-based good conductor paste or the like, and are in contact with and electrically connected to both ends of the resistance heating element 3 over substantially the entire circumference. The outer surface of the resistance heating element 3 is almost entirely covered with a glassy overcoat layer 5.

A pressure roller (not shown) is lightly and elastically circumscribed over the entire length of the roller-type fixing heater so as to face each other, and the fixing heater is rotated by the rotation of the pressure roller. The copy sheet on which the toner image is formed is heated while being pinched to fix the toner image on the copy sheet P.

[0005]

However, in such a conventional roller type fixing heater 1, since a pair of annular electrodes 4a and 4b are provided at both ends thereof, electric power is supplied to the electrodes 4a and 4b on both sides thereof. In addition to increasing the size of the power supply device 6, the wiring 6a of the power supply device 6 needs to be extended at least to both axial ends of the roller base 1 or in the vicinity thereof. The wiring 6a becomes long. Further, the wiring becomes large, and there is a problem that the wiring becomes complicated in a limited space such as a housing of an embedded device such as a copying machine.

Therefore, an object of the present invention is to arrange the electrode of the resistance heating element on only one side of the roller base body, thereby simplifying the structure of the power feeding means for feeding power to this electrode and reducing the size and weight. An object of the present invention is to provide a fixing heater, a fixing device, and an image forming apparatus capable of performing the above.

[0007]

The invention according to claim 1 is a cylindrical or columnar metal base; an insulating layer for coating the outer surface of the metal base with a heat-resistant electrical insulating material; and an outer surface of the insulating layer. A resistance heating element formed thereon; an annular electrode formed on one axial end of the insulating layer and electrically connected to the resistance heating element; at least at the other axial end opposite to the annular electrode A through hole that penetrates the insulating layer in the film thickness direction to electrically connect the resistance heating element to the metal base.

Therefore, according to the present invention, since the ring-shaped electrode is electrically connected to the resistance heating element and the metal base through the through hole, the ring-shaped electrode and the metal base on the same side as the ring-shaped electrode are electrically connected. Power can be supplied from only one side with respect to one axial end. Therefore, it is possible to reduce the size and weight of the power supply means and to shorten the power supply wiring, so that the wiring can be very easily routed. Also,
Since single-ended power feeding can be performed in this manner, it is not necessary to provide a conductor pattern on the inner surface of the metal base.

According to a second aspect of the present invention, a cylindrical or columnar metal base; an insulating layer for covering the outer surface of the metal base with a heat-resistant electrically insulating material; and an insulating layer formed on the outer surface of the insulating layer, A resistance heating element in which an extended end portion of the insulating layer, which is longer than one end portion in the axial direction, is directly adhered to and electrically connected to the outer surface of the metal substrate; formed on the other end portion in the axial direction of the insulating layer And an annular electrode electrically connected to the resistance heating element.

Therefore, according to the present invention, since the extended end portion of the resistance heating element is electrically connected to the metal base, the annular electrode and the same side thereof are connected as in the invention of claim 1. The power can be supplied only from one side of the inner surface of the metal base body at the one end. Therefore, the same effect as that of the invention according to claim 1 can be obtained.

The invention according to claim 3 is the invention according to claim 1 or 2, which is further required to be electrically connected to the annular electrode and one axial end portion of the metal base body on the same side as the annular electrode. The power supply means for supplying the electric power of

Therefore, according to the present invention, the electric power can be supplied to the resistance heating element from only one side of the metal base through the annular electrode and the metal base. Therefore, the same operation as that of the invention according to claim 1 or 2 can be achieved. It is possible to exert an effect.

A fourth aspect of the present invention is the fixing heater according to any one of the first to third aspects, wherein the insulating layer is made of ceramics.

Therefore, according to the present invention, when the invention according to any one of claims 1 to 3 is applied to a fixing heater whose insulating layer is made of ceramics, the invention according to any one of claims 1 to 3 can be applied. The same effect as that of the invention can be obtained.

According to a fifth aspect of the present invention, there is provided the fixing heater according to any one of the first to fourth aspects, wherein the feeding means further comprises an outer peripheral surface of the annular electrode and a metal base on the same side as the annular electrode. A pair of power supply members are provided to slidably contact the inner peripheral surface of one end of the gas to supply power.

Therefore, according to the present invention, it is possible to supply electric power from the pair of power feeding bodies to the resistance heating body of the rotating roller base body.

A sixth aspect of the present invention is the fixing heater according to any one of the first to fifth aspects, wherein the insulating layer has a thickness of 0.5 mm or less.

Therefore, according to the present invention, in general, when the thickness of the insulating layer is made thicker than 0.5 mm, when the paste of the insulating layer is printed and applied on the circular outer peripheral surface of the roller base body, no one will be affected. This causes unevenness in the film thickness after firing.
For this reason, there is a difference in heat transfer temperature due to uneven film thickness,
Since unevenness occurs in the temperature distribution in the circumferential direction of the roller base,
Although image fixing unevenness occurs, since the thickness of the insulating layer is set to 0.5 mm or less in the present invention, inconvenience such as sagging of the coating film at least to the extent of affecting the image is avoided. be able to.

A seventh aspect of the present invention is the fixing heater according to any one of the first to sixth aspects, further comprising a vitreous overcoat layer coating the outer surface of the resistance heating element.

Therefore, according to the present invention, since the outer surface of the resistance heating element is covered with the glass material of the electric insulator to electrically insulate the resistance heating element, the resistance heating element is prevented from short-circuiting and the electrical characteristics are stabilized. In addition, it is possible to smoothly pass a medium such as a copy sheet passing through the glass-like outer peripheral surface.

According to an eighth aspect of the present invention, the fixing heater according to any one of the first to seventh aspects is provided; the fixing heater is arranged so as to be in pressure contact with the fixing heater, and the heat from the fixing heater is fixed. A pressure roller that acts on the toner forming the image of the body and conveys the body to be fixed.

According to a ninth aspect of the present invention, there is provided the fixing device according to the eighth aspect, wherein toner is attached to the electrostatic latent image formed on the medium to form a reverse image, and the reverse image is transferred to a fixing target. And means for forming a predetermined image.

Therefore, the fixing device according to the eighth aspect of the invention and the image forming apparatus according to the ninth aspect of the invention have the fixing heater according to any one of the first to seventh aspects. It has the same effect.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIG.
~ It demonstrates based on FIG. 1 to 5, the same or corresponding parts are designated by the same reference numerals.

FIG. 1 is a partial vertical sectional view of a fixing heater according to a first embodiment of the present invention, FIG. 2 is a sectional view taken along the line II-II in FIG. 1, and FIG. 3 is a sectional view taken along the line III-III in FIG. In these figures, the fixing heater 11 is made of alumina (Al ₂ O ₃ ) or mullite (3Al ₂ ) on almost the entire outer peripheral surface of the roller base 12 made of a straight cylindrical metal pipe such as iron or stainless steel. The electrically insulating layer 13 is formed of a heat-resistant electrically insulating material such as O ₃ .2SiO ₂ ) ceramics to have a film thickness of, for example, 0.5 mm or less by thick film printing or the like, and electrically insulated.

For example, a silver / palladium (Ag / Pd) alloy or nickel / tin (Ni) is formed on, for example, substantially the entire outer peripheral surface of the electric insulating layer 13 except for one axial end (the right end in FIG. 1).
A film-shaped resistance heating element 14 mainly composed of Sn) alloy or the like is formed concentrically by thick film printing or the like.

Further, silver or silver / platinum (Ag / P) is formed on the outer peripheral surface of one end (right end) in the axial direction of the electric insulating layer 13.
t) An annular strip-shaped external electrode 15 made of a good conductor film of an alloy, a silver / palladium alloy (Ag / Pd) or the like is formed by thick film printing. The inner end (the left end in FIG. 1) of the electrode 15 partially overlaps with the right end of the resistance heating element 14 in the drawing, for example, in the vertical direction, and is electrically connected to each other over the entire circumference. Power is supplied to the resistance heating element 14. The entire outer peripheral surface of the resistance heating element 14 and the outer peripheral surface of the inner end portion of the annular electrode 15 are entirely covered with a glassy overcoat layer 16 to improve mechanical strength such as wear resistance and impact resistance. Corrosion-resistant protection from sulfurization, oxidation, etc., and electrical insulation from a pressure roller and the like described later are achieved. However,
The overcoat layer 16 may be omitted.

A through hole 17 shown in FIG. 3 is provided at the other axial end opposite to the annular electrode 15, and the left end of the resistance heating element 14 in FIG.
2 is electrically connected to the left end. Through hole 17
Is, for example, a conductor 17b is integrally formed by thick film printing on the inner peripheral surface of the through hole 17a penetrating in the film thickness direction at the axial left end of the electric insulating layer 13 and the upper and lower peripheral edges thereof. The resistance heating element 14 on the upper surface and the metal roller base 12 are electrically connected by a conductor 17b.

A phosphor bronze plate, copper, or copper is formed on the outer peripheral surface of the annular electrode 15 of the fixing heater 11 thus constructed and on the inner peripheral surface of one end of the metal roller base 12 on the same side as the annular electrode 15. A pair of wear-resistant power supply members 18, 19 made of a conductive strip-shaped leaf spring material plated with silver or the like is elastically pressed against the ends of the power supply members 18, 19 so as to be slidable. There is. These power supply members 18 and 19 are electrically connected to the power supply device 20 via the wiring 21, and the annular electrode 15
And the roller base 12 are configured as power supply means for supplying required power.

Therefore, according to an embodiment of the present invention,
Since the left end of the resistance heating element 14 in FIG. 1 is electrically connected to the metal roller base 12 by the through hole 17,
Even when the roller base 12 rotates, the pair of power supply members 18,
By supplying required electric power from 19 to the annular electrode 15 and the roller base 12, it is possible to reliably supply power to the resistance heating element 14 to heat it by energization.

Since the left end portion of the resistance heating element 14 in FIG. 1 is electrically connected by the through hole 17, only one side of the roller base 12 on the one end side (the right end side in FIG. 1) is provided with the power feeding body 18, It suffices to dispose 19 and the power supply device 20 thereof, and it is not necessary to respectively provide them in the vicinity of both axial ends of the roller base 12 as in the conventional example. Therefore, it is possible to reduce the size and weight of the power supply means including the power supply units 18 and 19 and the power supply device 20, shorten the wiring 21, simplify the wiring 21, and save the wiring space for the wiring 21. Can be planned. Further, since the externally exposed surface of the ring-shaped electrode 15 is required only on one side, it is possible to improve the electric insulation.

Since the annular electrode 15 need only be provided on one side of the roller base 12, the resistance heating element 14 can be extended to the opposite end of the annular electrode 15. As a result, the length of the roller base 12 itself can be shortened.

Further, since the roller base 12 is formed of a straight cylindrical metal pipe, the straightness is enhanced by the polishing process required when the roller base 12 is formed of ceramics into a straight cylindrical shape. The process can be omitted.

Further, the film thickness of the electric insulating layer 13 is 0.5 mm.
When the paste is thicker than the above, usually, when the paste of the electric insulating layer 13 is applied by printing on the circular outer peripheral surface of the roller base 12, sagging occurs and unevenness in the film thickness after firing occurs. For this reason, the heat transfer temperature varies due to the unevenness of the film thickness, which causes unevenness in the temperature distribution in the circumferential direction of the roller base body 12, resulting in uneven fixing of the image. However, in the present invention, the electrical insulating layer 13 is used.
Since the thickness of the coating film is set to 0.5 mm or less, it is possible to avoid inconveniences such as dripping that affects at least the image of the coating film.

A plurality of through holes 17 may be provided at a predetermined pitch in the circumferential direction of the electric insulating layer 13. Further, without providing the through hole 17, the left end portion in FIG. 1 of the resistance heating element 14 is extended axially outward from the left end of the electric insulating layer 13, and the extended end portion is provided on the outer peripheral surface of the roller base body 12 or Alternatively, the left end face may be directly attached and electrically connected.

FIG. 4 shows the construction of an embodiment of an electronic copying machine 31 which is a kind of the image forming apparatus of the present invention. The copying machine 31 has a housing 32 in which copying paper P in a cassette 33 is placed. An image forming unit 34 that pulls in and forms a toner image corresponding to an image of an original (not shown) and a fixing device 35 that fixes the toner image on the copy paper P are built-in.

The fixing device 35 is constructed, for example, as shown in FIG. 5, and faces the pressure roller 36 to face the fixing heater 1.
1 are arranged in parallel, and the fixing heater 11 is connected to the pressure roller 3
6 and a pair of left and right supporting rollers (not shown) may be rotatably sandwiched in the vertical direction, and the outer peripheral surface of the fixing heater 11 is elastically pressed against the silicone rubber layer 37 of the pressure roller 36.

The fixing heater 11 is provided with a pair of elastic feeds made of a phosphor bronze plate or the like which slidably contacts the outer peripheral surface of the annular electrode 15 and the inner peripheral surface of the metal pipe roller base 12, respectively. The resistance heating element 14 generates heat by being energized through the bodies 18 and 19, and the overcoat layer 16 is heated. Therefore, the copying paper P on which the toner image T is formed is nipped between the outer surface of the surface glass coat layer 16 and the silicone rubber layer 37 of the pressure roller 36, and the fixing heater 1 is attached.
By heating with 1, the unfixed toner image T can be melted and fixed on the copy paper P.

Further, the power supply members 18, 19 of the fixing heater 11
Since the power supply device including the power supply device 20 and the power supply device 20 may be installed on only one side of the roller base 12, the installation is easy and the power supply device can be downsized. For this reason, it is possible to save the installation space for installing the power feeding device in the housing 32, simplify the wiring of the power supply line 21 in the housing 32, and save the wiring space. it can.

[0040]

As described above, according to the invention of claim 1 of the present application, since the annular electrode is electrically connected to the metal base through the resistance heating element and the through hole, the annular electrode, Power can be supplied only from one side of the metal base on the same side as the one axial end. Therefore, it is possible to reduce the size and weight of the power supply means and to shorten the power supply wiring, so that the wiring can be very easily routed.

According to the second aspect of the present invention, since the resistance heating element is electrically connected to the metal base at the extended end,
Similar to the described invention, power can be supplied only from one side of the annular electrode and the inner surface of one end of the metal base body on the same side as the annular electrode.
Therefore, the same effect as that of the invention according to claim 1 can be obtained.

According to the invention of claim 3, electric power can be supplied to the resistance heating element from only one side of the metal base through the annular electrode and the metal base.
The same effects as those of the described invention can be obtained.

According to the invention of claim 4, when the invention of any one of claims 1 to 3 is applied to a fixing heater whose insulating layer is made of ceramics, any one of claims 1 to 3 is adopted. The same effects as those of the described invention can be obtained.

According to the fifth aspect of the invention, electric power can be supplied from the pair of power feeding bodies to the resistance heating element of the rotating roller base.

According to the sixth aspect of the present invention, generally, when the thickness of the insulating layer is made thicker than 0.5 mm, when the paste of the insulating layer is applied by printing on the circular outer peripheral surface on the roller base, The sagging causes unevenness in the film thickness after firing. For this reason, unevenness in image fixing occurs due to unevenness in the temperature distribution in the circumferential direction of the roller base due to a difference in heat transfer temperature due to unevenness in film thickness, but in the present invention, the film thickness of the insulating layer is 0. ．
Since the thickness is set to 5 mm or less, it is possible to avoid inconveniences such as dripping that affects at least the image of the coating film.

According to the invention of claim 7, since the outer surface of the resistance heating element is covered with the glass of the electric insulator to electrically insulate the resistance heating element, the resistance heating element is prevented from being short-circuited and the electrical characteristics are stabilized. In addition to this, it is possible to smoothly pass a medium such as a copy sheet passing through the glassy outer peripheral surface.

The fixing device according to the eighth aspect of the invention and the image forming apparatus according to the ninth aspect of the invention are the fixing device according to any one of the first to seventh aspects.
Since it has the fixing heater described in any one of the above, the same operational effect as this fixing heater is obtained.

[Brief description of drawings]

FIG. 1 is a partial vertical cross-sectional view of a fixing heater according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is a sectional view taken along the line III-III of FIG. 1;

FIG. 4 is an overall configuration diagram of an image forming apparatus according to a second embodiment of the present invention.

5 is an enlarged configuration diagram of a main part of the fixing device shown in FIG.

FIG. 6 is a partial vertical cross-sectional view of a conventional fixing device.

7 is a sectional view taken along line VII-VII of FIG.

[Explanation of symbols]

 11 Fixing Heater 12 Roller Base 13 Electric Insulation Layer 14 Resistance Heating Element 15 Annular Electrode 16 Glass Coat Layer 17 Through Hole 18, 19 Power Feeder 20 Power Supply Device 31 Electronic Copier (Image Forming Device) 32 Enclosure 33 Cassette 34 Image Forming Section 35 Fixing Device 36 Pressure Roller 37 Silicone Rubber Layer P Copy Paper T Toner Image

Claims (9)

[Claims] 1. A cylindrical or columnar metal base; an insulating layer covering the outer surface of the metal base with a heat-resistant electrical insulating material; a resistance heating element formed on the outer surface of the insulating layer; An annular electrode formed on one axial end of the layer and electrically connected to the resistance heating element; at least the insulating layer penetrating at least the insulating layer in the thickness direction at the other axial end opposite to the annular electrode. And a through hole for electrically connecting a resistance heating element to a metal base. 2. A cylindrical or columnar metal base; an insulating layer for coating the outer surface of the metal base with a heat-resistant electrical insulating material; a shaft of the insulating layer formed on the outer surface of the insulating layer. A resistance heating element in which an extended end portion longer than one end in the direction is directly attached to the outer surface of the metal substrate and electrically connected thereto; a resistance heating element formed on the other end portion in the axial direction of the insulating layer And a ring-shaped electrode electrically connected to the fixing heater. 3. An annular electrode, and a power supply means for electrically supplying a required electric power to the electrically connected end of the metal base on the same side as the annular electrode. The fixing heater as described in 1 or 2. 4. The fixing heater according to claim 1, wherein the insulating layer is made of ceramics. 5. The power feeding means comprises: an outer peripheral surface of the annular electrode; and an inner peripheral surface of one end of the metal base on the same side as the annular electrode.
The fixing heater according to any one of claims 1 to 4, further comprising a pair of power supply members that slidably contact each other and supply power. 6. The fixing heater according to claim 1, wherein the insulating layer has a film thickness of 0.5 mm or less. 7. The fixing heater according to claim 1, further comprising a vitreous overcoat layer that covers the outer surface of the resistance heating element. 8. The fixing heater according to claim 1, wherein the fixing heater is arranged so as to be in pressure contact with the fixing heater so as to face the fixing heater, and the heat from the fixing heater is fixed via a conveyance sheet. And a pressure roller that acts on the toner forming the image of the body and conveys the body to be fixed. 9. A fixing device according to claim 8, wherein a toner is attached to the electrostatic latent image formed on the medium to form a reverse image, and the reverse image is transferred to a member to be fixed to form a predetermined image. And an image forming apparatus.