JP2001223064A - Heating body, picture heating device and picture forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a heating body, a picture heating device and a picture forming device with high reliability, having the structure not broken by the heating stress at the part where papers are not running through, and not broken by the dielectric breakdown between a base plate and an electrode even if a contact point receives mechanical stress. SOLUTION: The heating body comprises an insulation layer 19 on a metallic base material 11 and a heating resistor 12 on the insulation layer 19. The dielectric strength between a contact point part 15 supplying electric power to the heating resistor 12 and the base material 11 is made bigger than that between the heating resistor 12 and the base material 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating element used in a heating apparatus or the like that applies thermal energy to a recording material via a heat-resistant film.

[0002] This apparatus is an electrophotographic copying machine, a printer,
An image heating device in an image forming apparatus such as a facsimile, that is, a recording material (electrofax sheet, electrostatic recording, etc.) using a toner made of a resin which can be heated and melted by an image forming process means such as electrophotography, electrostatic recording and magnetic recording. Sheet, recording material, sheet, printing paper, etc.) directly or indirectly (transferred) on the surface of the recording material carrying the unfixed toner image corresponding to the target image information. It can be used as an image forming apparatus for performing a heat fixing process as a permanent fixed image on a surface.

In addition, the present invention is not limited to the image forming apparatus, and can be widely used as a means or a device for heating the image bearing member, such as a device for heating a recording material carrying an image to improve the surface properties.

[0004]

2. Description of the Related Art For convenience, in an image forming apparatus such as an electrophotographic apparatus or an electrostatic recording apparatus, a recording medium such as a transfer material, an electrofax sheet, or an electrostatic recording paper is formed and carried by a transfer (indirect) method or a direct method. An image forming apparatus used to thermally fix (fix) an unfixed toner image as a permanent image will be described as an example.

Conventionally, a heat roller type apparatus has been widely used as an image forming apparatus. This device has a fixing roller as a heat roller heated to a predetermined surface temperature by a built-in heat source such as a halogen lamp, and a pressing roller pressed against the fixing roller. The recording medium serving as a pair to be heated is introduced into and supported by and conveyed, so that the unfixed toner image is thermally fixed on the surface of the recording medium by the heat of the fixing roller in the pressure nip.

However, since the fixing roller has a large heat capacity, a large heat loss and poor thermal efficiency, it takes time to raise the temperature of the fixing roller to a temperature suitable for heating the object to be heated. Lack of startability, it was necessary to maintain a high temperature at all times during standby, so that energy consumption was large and contrary to energy saving. In addition, even during standby, heat is released into the machine, causing a problem of temperature rise in the machine.

As an apparatus having a quick start property and capable of power-saving on-demand heating, Japanese Patent Application Laid-Open No. 63-3131 discloses
No. 82, etc., a heating device of a film heating type has been proposed and has been put to practical use. In this film heating type heating device, a planar heating element (a so-called ceramic heater) having a small heat capacity, a film that is in sliding contact with a heating surface of the heating element, and a pressure roller that forms a nip with the film interposed therebetween are provided. The recording material is sandwiched between the nips and conveyed together with the film, and the recording material is heated by heat from a heater via the film. In the case of such a configuration, the heat capacity as a heat source or a film through which heat from the heat source can be reduced, the heat capacity can be reduced as compared with a heat roller type heater or a heat roller, the temperature can be rapidly raised, and the standby state can be achieved. There is an advantage that the power of the device can be saved.

FIG. 7 is a schematic structural view of one example of this heating element. FIG. 7 (a) is a partially cutaway model view of the heating element (the side in contact with the heat-resistant film), and FIG. FIG. 7C shows an enlarged cross-sectional model diagram along the line CC in FIG. 7B.

On the surface side of the heating body in FIG.
Reference numeral 1 denotes a horizontally long ceramic base material such as alumina, and 112 denotes a resistance heating element such as silver palladium formed on the surface of the base material 111 along the length of the base material. Reference numeral 115 denotes an electrode made of silver or the like which is electrically connected to the left end of the resistance heating element 112 and formed on the surface on the left end side of the substrate. 11
Reference numeral 3 denotes an insulating surface protective layer made of glass or the like formed on the surface of the base material so as to cover the resistance heating layer 112 except for the above-described electrode 115, and formed on the surface of the base material.

[0010] On the back surface of the heating element in FIG.
・ 116 is formed parallel to and along the length of the back surface of the base material from the right end side of the base material to substantially the center in the longitudinal direction of the base material.
A strip-shaped conductive pattern 114 made of silver or the like is a temperature detecting resistor 114 formed on the back surface of the base material by conducting electricity between the left ends of the two striped conductive patterns 116.

[0011] When an AC voltage is applied between the two electrodes 115 from an energizing circuit (not shown), the resistance heating element 112 generates heat over its entire length, and the temperature of the heating element rapidly rises.

The temperature of the heating element 1 is measured by a temperature detecting resistor 114 on the back side of the base material, and
Output of conductor pattern 116 (DC line)
Is supplied to an unillustrated energization control circuit, and energization to the AC line is controlled so that the temperature of the heating element 101 is maintained at a predetermined temperature. That is, the temperature of the heating body 101 is controlled.

[0013]

As ceramics used as a base material of the heating element 101, alumina has conventionally been used. However, when very thick paper or paper is fed multiple times,
Temporarily separates from the pressure roller 104 outside the paper edge, and heat is not taken away by the paper or the pressure roller 104, so that the temperature rises rapidly and a large temperature gradient is generated, so that the sheet is destroyed by thermal stress. There was a case. Therefore, as a countermeasure, it has been proposed to use aluminum nitride, which has several times better thermal conductivity than alumina, as a base material and prevent a large temperature gradient from occurring. However, the base material using aluminum nitride is very expensive, so that the cost is higher than when alumina is used.

Accordingly, a relatively inexpensive thin metal substrate is coated with glass as an insulating layer, and a resistance heating element, a contact point, and insulating glass are provided thereon in the same manner as a conventional heating element. It is conceivable to adopt a configuration in which the heating element is not broken even if a large temperature gradient is formed in the body.

However, in the heating element, the insulating property is maintained by the glass coated on the conductive metal, and there is a problem that the mechanical strength of the insulation is weak.
In particular, when the AC contact leading to the resistance heating element is formed by thick-film printing on an insulating glass coating, since the AC contact has a high voltage and a large current, it is necessary to firmly contact the heating element side contact and the connector side contact. Since a relatively strong pressure is applied to the contacts, the contacts may rub against each other due to thermal shrinkage during insertion or repeated heat treatment, and large mechanical stress is applied to the contacts and the insulating glass coat under the contacts. Sometimes. This mechanical stress may destroy the glass coating of the contact portion and short-circuit the contact and the metal of the base material.

Accordingly, the present invention uses a metal base material and is configured not to be broken by the thermal stress of the non-sheet passing portion, and the insulation between the substrate and the electrode is broken even if a mechanical stress is applied to the contact portion. It is an object of the present invention to obtain a highly reliable heating element, an image heating apparatus, and an image forming apparatus that do not need to be used.

[0017]

Means for Solving the Problems A heating element, an image heating apparatus and an image forming apparatus according to the present invention are characterized by the following constitution in order to solve the above-mentioned problems.

[1] A heating element including an insulating layer on a metal base material and a resistance heating element on the insulation layer, and a contact portion for supplying power to the resistance heating element. A heating element characterized in that the insulating property with respect to the base material is higher than the insulating property between the resistance heating element and the base material.

[2] A heating element comprising an insulating layer provided on a metal base material and a temperature detecting element provided on the insulating layer, wherein the heating element comprises a contact portion of the temperature detecting element and the base material. A heating element characterized in that the insulating property is higher than the insulating property between the temperature detecting element and the substrate.

[3] The heating element according to [1] or [2], further comprising a heat-resistant insulating member between the contact portion and the substrate.

[4] The heating element according to [3], wherein the heat-resistant insulating member has a shape covering an end face of the base material.

[5] The heating element according to [3] or [4], wherein the heat-resistant insulating member is made of ceramics, glass or heat-resistant resin.

[6] An image heating apparatus for heating an image on a recording material by the heating element according to any one of [1] to [5].

[7]: The heating element according to any one of [1] to [5], a film in sliding contact with the heating element, and a pressure for forming a nip with the heating element via the film. A recording material holding an image, sandwiched by the nip, transporting the recording material together with the film, and heating the image on the recording material by heat from the heating element. Heating equipment.

[8]: In an image forming apparatus having an image forming means for forming an image on a recording material and an image heating means for heating the image on the recording material, [6] or [ [7] An image forming apparatus comprising the image heating device according to [7].

<Operation> The invention according to the present application is directed to a heating element that substitutes a conventional ceramic substrate by coating glass as an insulating layer on a metal base material.
By providing a heat-resistant insulator between the contact portion and the metal base material to enhance insulation, and by increasing the mechanical strength of the contact portion, a strong mechanical force is applied when the connector is attached to the contact. Even if stress is applied, insulation between the base material and the contact is not destroyed, thereby improving reliability.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS <Embodiment 1> FIG. 1 shows a schematic configuration diagram of a heating body of the present invention. FIG. 1 (a) is a partially cutaway surface model diagram of the heating body (the surface side in contact with the heat-resistant film).
1 (b) is a model diagram of a vertical section of a contact portion, and FIG. 1 (c) is an enlarged model diagram of a cross section along line CC of FIG. 1 (b).

In FIG. 1, reference numeral 11 denotes a metal base material such as stainless steel. The contact portion of the base material 11 has the same thickness as the thickness of the insulation reinforcing member (heat resistant insulation member) 17 on the side opposite to the surface on which the resistance heating element is formed. And the insulation reinforcing member 17 is fixed to that portion. An insulating glass layer 19 serving as an insulating layer is formed thereon, and silver palladium (Ag / Pd) .RuO is further formed thereon.
_A resistive heating element 12 is patterned by screen-printing a paste material of an electrical resistance material such as 2.Ta ₂ N, and an AC contact (contact portion) 15 for supplying power to the resistance heating element is provided at one end in one longitudinal direction. And finally a glass coat layer 14 as an insulating surface protective layer. Reference numeral 5 denotes a glass bead type temperature detecting element, which is bonded or abutted on the surface on the side opposite to the resistance heating element 12. The power to the resistance heating element 12 is controlled based on the temperature detected by the temperature detecting element 5 to adjust the temperature to a predetermined temperature.

Reference numeral 6 denotes a connector for supplying power to the resistance heating element 12. The contact (electrode) 6a is connected to the heating element side contact 1.
5 is in contact.

More specifically, as shown in FIG. 1B, a 0.7 mm thick stainless steel base material 11 is bent into a crank shape by press working or the like. The bending height h at this time is the same as the thickness of the insulation reinforcing member 17, ie, 1.8.
mm. In this portion, an insulation reinforcing member 17 made of alumina having a thickness of 1.8 mm is provided. This insulation reinforcing member 1
As a fixing method of No. 7, some nails may be provided at the end of the stainless steel base material 11 and the nails may be bent to be fixed, but in the present embodiment, they are fixed with a heat-resistant adhesive. . Although a slight gap or a step is formed on the surface of the insulating reinforcing member 17 and the base 11 on which the resistance heating element 12 is formed, a thickness of about 40 μm is required in order to prevent the insulating glass layer 19 from inferior insulation due to pinholes. And print this with 2
When the glass layer of about 80 μm is formed by repeating the process, the gaps and steps are almost filled, and the level does not cause a serious problem in the subsequent steps. Further thereon, a resistance heating element 12, an AC contact 15, and a glass coat layer 14 are sequentially formed by thick film printing.

For comparison, a heating element in which an insulating glass layer 19, a resistance heating element 12, and an AC contact 15 are directly formed on the substrate 11, and an insulation reinforcing member 17 on the substrate 11 as in this embodiment. A comparative study was conducted with the heating element 1 in which the insulating glass layer 19, the resistance heating element 12, and the AC contact 15 were sequentially formed.

The contact pressure of the contact 6a of the connector 6 is 150N
Since the insertion and removal of the connector 6 is usually performed once or twice for each heating element, the test was repeated 30 times. Thereafter, an AC current having an amplitude of 1.5 kV was applied between the AC electrode and the substrate 11, and a dielectric strength test was performed. This test was performed on 20 heating elements for each heating element. As for the heating element formed directly with the insulating glass layer 19, the resistance heating element 12, and the AC contact 15, 5 out of the 20 heating elements had one side of the AC contact. Caused insulation failure. Although there is no problem if insulation failure occurs on one side only during normal use, insulation failure may occur on both sides, and it is necessary to further increase reliability in terms of safety. On the other hand, in the heating elements of the present embodiment, none of the 20 heating elements had defective insulation.

In this embodiment, the insulation reinforcing member 17 is used.
Thus, the distances h and j between the AC contact 15 and the substrate 11 (the distance between the contact 6a and the substrate 11) are secured. In order to confirm the reliability due to this, the cracked insulation reinforcing member 17 was used.
Was used to form a heater 1, and the same test as above was conducted, but no insulation failure occurred. That is, the insulation reinforcing member 17
With the thickness, not only the insulating property of the material but also a spatial insulating distance can be taken, and the reliability can be further improved.

<Embodiment 2> The insulation reinforcing member 18 of this embodiment is shown in FIG. 2 (a), and FIG. 2 (b) is a longitudinal sectional model view of the contact portion of the heater 1 of this embodiment.

As shown in FIG. 2, the insulation reinforcing member 18 of this embodiment has a cap shape. By forming the base 11 in such a shape as to cover the entire contact-side end, the base 11
Can be covered with an insulator without being exposed, so that the distance between the AC contact 15 and the base 11 along the surface can be increased. Thereby, the same effect as that of the above embodiment can be obtained within the limited width, and the size of the AC contact 15 can be widened to the end of the substrate, so that the contact area between the contact and the electrode can be increased, A more reliable power supply method can be adopted.

In this embodiment, the cap is formed so as to cover the three surfaces of the base material 11. However, in the case where there is a margin in the longitudinal dimension or when a sufficient distance can be secured on the surface of the heating body, the AC shape may be used. Depending on the shape of the contact 15 or the like, only two or one surface may be covered. In addition, there is no problem if the shape is such that only the bent end face is hidden in an L-shape instead of the cap shape if necessary.

<Embodiment 3> In the above embodiment, the contact portion for supplying power to the resistance heating element has been described. However, if a short circuit occurs, a failure such as abnormal temperature rise or temperature adjustment may not be possible.Therefore, the insulation between the contact part of the temperature sensing element and the board is It is effective to increase the insulation property.

Therefore, in the present embodiment, an insulation reinforced member is used also for the contact portion of the temperature detecting element. Since other configurations are the same as those of the first embodiment, the same components are denoted by the same reference numerals and description thereof is omitted.

In FIG. 6, reference numeral 19 'denotes an insulating layer provided on the metal substrate 11, 5 denotes a temperature detecting element (such as a thermistor) provided on the insulating layer, and 16 denotes a conductive element connected to the temperature detecting element 5. The path 16a is a contact portion of the temperature detecting element 5. The contact 6a 'of the external connector 6' comes into contact with the contact portion 16a, and the temperature information by the temperature detecting element 5 is detected.

As shown in FIG. 6C, an insulation reinforcing member 17 is provided between the contact portion 16a and the base 11, similarly to the contact portion of the resistance heating element 12. The insulation reinforcing member 17 on the contact portion 16a side is the same as that on the contact portion 15 side, and the distances h and j to the base material 11 are the same. Lower than the power to
Since the contact pressure is also small, the insulation reinforcing member 17 on the contact portion 16a side may be made thinner and the distances h and j may be set accordingly.

<Other Embodiments> In the above embodiment, the contacts 15 are formed only at one end of the heating element 1. However, the present invention is not limited to this. Contact points are provided at both ends of the heating element to insulate this section. It is good also as a structure which raises. FIG. 3A shows a configuration in which two resistance heating elements having different lengths, that is, two resistance heating elements 12 corresponding to different paper passing areas are provided, and contacts are provided at both ends of the heating element. At this time, as shown in FIG. 3B, both end portions are provided with an insulation reinforcing member 17.

<Image Heating Apparatus> FIG. 4 is a schematic diagram showing the structure of an image heating apparatus according to the present invention.

Reference numeral 1 denotes a heating element shown in the above embodiment having a longitudinal direction perpendicular to the drawing, 102 denotes a heating element holder which fixedly supports the heating element 1 downward, 103 denotes a heat-resistant film, and 104 denotes elastic pressure. A fixing nip portion N as a heating portion having a predetermined width is formed by pressing the heating member 1 and the pressure roller 104 with the heat-resistant film 103 therebetween and pressing the heating member 1 against the heating member 1.

The film 103 is brought into contact with the surface of the heating body 1 at the fixing nip N at a predetermined speed in the direction of the arrow while sliding in close contact with the surface of the heating element 1 by the driving means (not shown) or the rotational driving force of the pressure roller 104. Traveled and transported.

In a state where the film 103 is traveling and conveyed at a predetermined speed and the temperature of the heating body 1 is adjusted to a predetermined temperature,
By introducing the recording medium P as a heated body between the film 103 and the pressure roller 104 in the fixing nip portion N, the recording medium P adheres the fixing nip portion N to the surface of the film 103, and The fixing nip portion N is conveyed together with the fixing member 103, and in the conveying process, the unfixed toner image T is thermally fixed on the recording medium surface by receiving heat from the heating body 1 via the film 103.

The recording medium P that has passed through the fixing nip N is separated from the surface of the film 103 and is discharged and conveyed.

The use of the heating element 1 and the heat-resistant film 103 having a low heat capacity allows the fixing nip portion N serving as a heating portion to be intensively heated via the film 103, so that the apparatus has a quick start property. And power-saving on-demand heating is possible.

That is, since the temperature of the heating element 1 rises in a short time, even if the recording medium as the object to be heated is immediately passed, the heating element 1 is required until the recording medium reaches the fixing portion N. Can be heated to temperature. In addition, no heating is performed during standby, so there is no temperature rise inside the machine and no energy is consumed.

<Example of Image Forming Apparatus> FIG. 5 is a schematic structural view of an example of the image forming apparatus. The image forming apparatus of this embodiment is a laser beam printer using an electrophotographic process.

Reference numeral 21 denotes a rotating drum type electrophotographic photosensitive member (hereinafter, referred to as a photosensitive drum) as a first image carrier, which is rotationally driven at a predetermined peripheral speed (process speed) clockwise as indicated by an arrow. , it is uniformly charged to a predetermined negative dark potential V _D by a primary charger 22 in the rotation process.

Reference numeral 23 denotes a laser beam scanner, which is a laser beam L modulated according to a time-series electric digital image signal of target image information input from a host device such as an image reading device, a word processor, and a computer (not shown). To scan and expose the uniformly charged surface of the rotating photosensitive drum 21.

By this laser beam scanning exposure, the exposed portion of the uniformly charged surface of the rotating photosensitive drum 21 has a small absolute value of potential and becomes a bright potential _VL .
An electrostatic latent image corresponding to the target image information is formed on one surface. Next, the latent image is subjected to reversal development (toner is adhered to the laser exposure light potential _VL portion of the photosensitive drum surface) with the negatively charged powder toner by the developing device 24, and the toner image T
Is visualized as

On the other hand, a recording material P fed from a paper feed tray (not shown) is exposed to a pressure nip (transfer portion) m between a transfer roller 25 as a transfer member to which a transfer bias is applied and a photosensitive drum 21. The sheet is fed at an appropriate timing synchronized with the rotation of the drum 21, and the toner image T on the surface of the photosensitive drum 21 is sequentially transferred onto the surface of the recording material P.

Then, each of these elements 21, 22, 2
The recording material P on which the unfixed toner image T has been formed by the image forming means composed of 3, 24, 25, and the like is separated from the surface of the rotating photosensitive drum 21 and the fixing device (image heating means) described in the above embodiment. The toner image T is introduced into the R, undergoes a fixing process, and is discharged out of the apparatus as an image formed product (print).

The rotating photosensitive drum 21 after the recording material is separated
The surface is cleaned by the cleaning device 26 to remove the residual toner such as toner remaining after transfer, and the surface is repeatedly provided for image formation.

According to the above configuration, even when small-sized paper P such as a postcard or an envelope is continuously passed, the temperature rise in the non-paper passing portion is alleviated by the metal base material 11 having higher thermal conductivity than the ceramic substrate. In addition, problems due to high temperature offset and thermal stress can be suppressed. Further, even when the temperature of the non-sheet passing portion rises due to extremely thick paper passing or a paper jam, the toughness is higher than that of the ceramic substrate, and no breakage occurs. Further, since insulation failure at the contact portion 15 is also prevented, stable image formation can always be performed, and reliability is improved.

[0057]

As described above, according to the present invention, not only the structure which is not broken by the thermal stress of the non-sheet passing portion but also the insulation between the substrate and the electrode is obtained even if the contact portion is subjected to a mechanical stress. A highly reliable heating element, image heating apparatus, and image forming apparatus that are not destroyed can be obtained.

[Brief description of the drawings]

1A and 1B are schematic views of a heating body according to a first embodiment of the present invention, in which FIG. 1A is a partially cutaway surface model diagram (surface side in contact with a heat-resistant film 3), and FIG. Figure,
(C) is an enlarged cross-sectional model diagram along line CC in (a).

FIG. 2 is a schematic diagram of a heating body according to a second embodiment, and (a)
FIG. 3 is an explanatory view of the insulation reinforcing member 18, and FIG.

FIG. 3 is a schematic view showing another embodiment of the heating element according to the present invention.

FIG. 4 is a structural model diagram of an image heating apparatus according to the present invention.

FIG. 5 is a structural model diagram of an image forming apparatus according to the present invention.

FIG. 6 is a schematic diagram of a heating element according to a third embodiment.

7 (a) is a partially cutaway surface model diagram of a heating body in a conventional example, (b) is a back surface model diagram, and (c) is an enlarged cross-sectional model diagram along line CC of (b). is there.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 Heating element 5 Temperature detecting element 11 Metal substrate 12 Resistance heating element 14 Glass coat 15 AC contact 17 Insulation reinforcing member of Embodiment 1 18 Insulation reinforcing member of Embodiment 2 19 Insulating glass layer P Recording material T Toner

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) 2H033 AA23 AA42 BA26 BA32 BE03 3K034 AA02 AA03 AA10 AA16 AA37 BA05 BB02 BB14 BC04 BC12 DA05 EA04 3K092 PP18 QA05 QB02 QB03 QB32 QB64 QB75 RF03 RF09 RF17V06

Claims (8)

[Claims] A heating element comprising: an insulating layer on a metal base; and a resistance heating element on the insulation layer, wherein a contact portion for supplying power to the resistance heating element and the base are provided. A heating element characterized in that the insulating property with respect to the material is higher than the insulating property between the resistance heating element and the base material. 2. A heating element comprising: an insulating layer on a metal base; and a temperature detecting element on the insulating layer, wherein an insulating property between a contact portion of the temperature detecting element and the base is provided. Characterized in that the temperature of the heating element is higher than the insulating property between the temperature detecting element and the substrate. 3. The heating element according to claim 1, further comprising a heat-resistant insulating member between said contact portion and said base member. 4. A heating element according to claim 3, wherein said heat-resistant insulating member has a shape covering an end face of said base material. 5. The heating element according to claim 3, wherein the heat-resistant insulating member is made of ceramics, glass, or heat-resistant resin. 6. An image heating apparatus for heating an image on a recording material by the heating element according to claim 1. Description: 7. A heating element according to claim 1, further comprising: a film that is in sliding contact with the heating element; and a pressing member that forms a nip with the heating element via the film. An image heating apparatus, wherein a recording material carrying an image is sandwiched between the nips, the recording material is conveyed together with the film, and the image on the recording material is heated by heat from the heating body. 8. An image forming apparatus comprising: an image forming unit for forming an image on a recording material; and an image heating unit for heating an image on the recording material, wherein the image heating unit is used as the image heating unit. An image forming apparatus comprising the image heating device of (1).