JP2786051B2 - Planar heating element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet heating element of a fixing unit in an electrophotographic recording apparatus such as a laser printer using a photosensitive member and toner, and more particularly to a heater safety circuit for the sheet heating element.

[Technical environment] In the printer which is an output device of a personal computer, an electrophotographic printer such as a laser printer for recording on a plain paper is rapidly increasing in terms of printing speed, printing quality, noise during printing, and the like. The market is expanding. Also, in the facsimile apparatus and the like, the electrophotographic facsimile apparatus capable of recording on plain paper has been rapidly expanding in market similarly to a printer in that the received recording information can be used as a document as it is.

An electrophotographic printer typified by a laser printer or the like has a charging unit 601 as shown in FIG.
A photosensitive drum 603 having a developing unit 602, a laser unit 604 for forming an electrostatic latent image on the photosensitive drum 603, and a developed toner image (not shown) on the photosensitive drum 603 on a recording paper. 605, and a fixing unit 607 for fixing the toner image on the surface of the recording paper 605.
05, and a controller 609 that processes recording data sent from a host computer (not shown) and controls an optical signal 608 from a laser unit 604. It is.

In the case of a facsimile apparatus, the host computer is a communication line, and the controller 609 has a function of not only recording, but also transmitting an image signal read by a line sensor or the like to the communication line. It is.

[0005] The formation of an electrostatic latent image in electrophotographic recording using such a photosensitive drum is not limited to a method using a laser unit, but also includes an LED that forms an electrostatic latent image using an LED array formed in a horizontal row. There is also a liquid crystal system that forms an electrostatic latent image using a liquid crystal shutter, and is also called a page printer because all of them record on a page basis. You can do it.

[Common Technology] For these reasons, electrophotographic printers and facsimile machines have been rapidly expanding. In such electrophotographic printers and facsimile machines, however, electrophotographic printers and facsimile machines are formed on paper. A fixing unit for fixing the toner image on the paper surface is required. As an example of the structure of the fixing unit, as shown in FIG. 7, an endless film 701 is hung on a tube of a sheet heating element 702 and a dive roller 703. The heating surface of the sheet heating element 702 is pressed by the pressure roller 704, and the drive roller 70
In some cases, the recording paper 705 is caused to pass through the heating surface of the sheet heating element 702 and the tube of the pressure roller 704 by rotating the sheet 3.

[0007]

2. Description of the Related Art As a heating element used in such a fixing device, as shown in FIG. 8, lead electrodes 802 are formed at both ends of an elongated ceramic base, and a resistor 803 is provided between the lead electrodes 802 at both ends. A thermistor 806 is formed on a heat-resistant resin holder 805 having a concave portion 804 that matches the outer shape of the ceramic substrate 801 having the resistor 803 so that the ceramic substrate 801 can be contacted from the back surface of the holder 805. In some cases, the holder 805 and the ceramic base 801 are bonded almost at a communication portion.

Here, the holder 805 and the ceramic base 8
01 is bonded only at the center because the temperature rises or falls when power is supplied to or cut off from the heating element. However, due to the difference in the thermal expansion characteristics between the ceramic base 801 and the holder 805, the heat is generated. This is because a large displacement occurs at both ends of the body, and only the central portion is bonded to absorb the displacement.

As shown in FIG. 9, an extraction electrode 802 of a heating element formed by bonding and fixing to the holder 805 forms a connector in which a contact 901 is fixed with an insulating resin mold 902, and this connector is heated. The holder 805 is fitted into the body extraction electrode 802 together with the holder 805, and heater power is supplied by electric wiring to this connector.

[0010]

The heating element of the fixing unit having such a configuration has two problems. One is that the bonding between the ceramic base 801 forming the heating element and the holder 805 is performed only at the center, and the reliability of this bonding is not so high, and the temperature of the heating element is controlled. Therefore, the reliability of contact of the thermistor, which is the most important, becomes low, and in a printer using paper, there is a danger of smoke or ignition due to the high temperature.

Another problem is that the connection between the extraction electrode portion and the heater power source is shifted due to the difference in thermal expansion between the ceramic base 801 and the holder 805 as described above. ), Holder 1
001, the electric wire 1002 is fixed, and the ceramic base 801 is fixed.
In the method of connecting by soldering 1003 using solder to the extraction electrode 802 at the end of the wire, a large distortion is generated in the soldered portion, and the connection reliability is low. There was also a problem. FIG.
0 (b), a hole is formed in the extraction electrode 802, a screw portion is formed in the holder 1004, and the crimp terminal 1006 in which the electric wire 1005 is crimped to the screw portion is jointly fastened. Due to the difference, a large strain is applied to the screw fixing portion, and the heating element is cracked, so that the reliability of the device cannot be secured.

For this reason, the connection to the heater power source requires a connector as shown in FIG. 9, which is a contact made of a material capable of maintaining springiness against heat. However, this connector is not suitable for general connectors on the market, and is expensive because of the material of the contacts. Furthermore, even when this connector is used, the contact on the connector side is taken out due to the difference in thermal expansion between the holder and the ceramic base, causing a shift in the electrode surface, and the temperature rises or rises when the printer is operated or stopped.
The contact is displaced on the extraction electrode surface due to the drop, and the extraction electrode wears due to the displacement, and from this point, there is a problem that it is not easy to ensure the reliability of the contact.

In the above-described structure of the planar heating element, if the bonding technique between the ceramic base and the holder is not sufficiently established, the contact between the thermistor and the heating section becomes poor, and the output from the thermistor becomes small. In addition, there is a danger that the sheet heating element may become abnormally high. For this reason, it is necessary to securely fix the ceramic base and the holder so that the thermistor does not separate from the heat generating portion. Also, the connection to the heater power supply is not reliable with soldering or screws,
A special connector is also required when using a connector,
Even if this connector is used, the reliability of the contact is not high, and the purpose is to improve the reliability of the contact portion without using a special connector.

[0014]

Means for Solving the Problems The planar heating element of the present invention comprises:
An electrode pattern is formed on both ends of the resistor in a planar heating element in which a resistor is formed in the longitudinal direction on a ceramic substrate or a heat-resistant substrate having a length ratio of 5 or more with respect to a width of 1, And an electrode pattern having a connection electrode pattern extending from the electrode pattern toward a central portion in the longitudinal direction of the ceramic substrate or the heat-resistant substrate, and being provided by providing an external connection electrode terminal at the central portion. Are formed on the both sides of the resistor, and are formed by forming an external connection electrode pattern on the back surface or the end face in the width direction at the center.

The electrode pattern toward the center may be on a surface opposite to the surface on which the resistor is formed,
An electrode pattern for external connection is formed on the end face in this plane or in the width direction at the center, or the electrode pattern directed to the center is formed on at least one width end face of the ceramic base material forming the resistor. It is also obtained by forming an electrode pattern for external connection at the center in this plane or on the surface opposite to the surface on which the resistor is formed.

Further, a contact which contacts the external connection terminal formed at the center and a concave portion which matches the outer shape of the planar heating element are provided, and the surface in the concave portion contacts the planar heating element. The heat-resistant resin-formed holder is formed as described above, and the widthwise end surface of the planar heating element is formed so that the end face in the width direction partially or entirely in the longitudinal direction is opposite to the resistor forming surface forming the heating element. It is obtained by forming a taper so that the width on the surface side is different, and having a holder made of a heat-resistant resin having a concave portion corresponding to the tapered portion. Further, a step is formed on an end face in a width direction of the planar heating element so that a resistor forming surface forming the heating element and a width on the opposite surface side are different in part or all in a longitudinal direction,
It can also be obtained by having a holder made of a heat-resistant resin for holding the step forming portion.

[Operation] The pattern of the extraction electrode formed on the ceramic substrate constituting the heating element is routed in a pattern to the center of the heating element, and the extraction electrode is formed at the center of the pattern. The tapered portion is formed in the shape of the ceramic base so that the tapered portion is inserted into the holder, and is fixed to the holder without bonding.

[0018]

Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a view showing an electrode and a pattern structure of a ceramic base constituting a planar heating element according to an embodiment of the present invention. An electrode 102 is formed at a longitudinal end of a ceramic base 101. And this terminal electrode 10
The resistor 103 is formed between the two using means such as thick film printing. Further, an extraction electrode 1 is provided at the center in the longitudinal direction.
An electrode pattern 105 is formed between the extraction electrode 104 and the terminal electrode 102.

The heating element thus formed is formed with a contact 106 which is in contact with an extraction electrode 104 at the center, and a concave portion 107 which conforms to the outer shape of the ceramic base 101. When the thermistor 110 is fitted into the holder 108 and the thermistor 110 is mounted on the thermistor receiver 109 formed on the inner surface of the concave portion of the holder 108, the thermistor 110 is brought into close contact with the back surface of the ceramic base 101, and the extraction electrode 104 formed on the ceramic base 101 is The contact 106 of the holder 108 is supported and fixed by soldering with high-temperature solder or the like or fixing with screws or the like.

FIGS. 2A and 2B show an example of a fixed state of the extraction electrode 104 at the center of the contact 106, the holder 108 and the ceramic base 101. A window through which the extraction electrode 104 can be seen is formed. The extraction electrode 104 formed on the ceramic base 101 and the contact 106 fixed to the holder 108 are soldered from this window, and the tab terminal 201 formed on the contact is soldered. To the bottom of the holder.

The planar heating element thus configured is formed by performing a soldering process with the contact 106 for connecting the extraction electrode 104 formed at the center to the outside, so that the bonding step is not required. . Further, when power is supplied to the heating element, the ceramic base 101 and the holder 108 thermally expand. However, since this thermal expansion occurs isotropically around the extraction electrode 104, the contact 106, and the fixed portion, the connection portion In this case, there is no effect of thermal expansion, and no stress is applied to the connection and fixing portions. Therefore, the adhesion between the ceramic base and the thermistor is always constant, and the reliability of temperature control is remarkably improved.

FIGS. 3A and 3B show the ceramic base 10.
FIG. 3 is a diagram showing an arrangement example of an electrode pattern for connecting between a resistor 103 and an extraction electrode 104 formed in FIG.
(A) is the end of the ceramic substrate 101 which is turned to the back,
The connection electrode pattern 301 up to the extraction electrode 104 is formed on this back surface, and FIG. 3B shows the connection electrode pattern formed on the widthwise end surface of the ceramic base 101. 3 (a) and 3 (b)
Although not shown, the extraction electrode 104 formed at the center of the ceramic base 101 is not limited to one divided on both sides in the width direction, and two extraction electrodes are formed on one side of the ceramic base. Similar effects can be obtained by forming a connection electrode pattern so as to be connected to these two extraction electrodes.

FIG. 4 is a view showing the configuration of a planar heating element according to another embodiment of the present invention. A ceramic substrate 401 constituting the heating element has a surface on which a resistor 402 is formed on an end face in a width direction. And the tapered portion 40 so that the width of
3 is provided. On the other hand, similarly to the case shown in FIG. 1, the contactor 40 having an externally connected tab terminal 406 that contacts the extraction electrode of the ceramic base 401 is provided on the holder 404.
7 and a thermistor 408, and the heating element of the ceramic base 401 is slid into the holder 404. Then, with the slide inserted, the ceramic substrate 4
01 and the extraction electrode 405 and the holder 404
Contact 40 formed on contact 401 fixed to
7 is supported and fixed by soldering or screwing.

FIG. 5 shows another embodiment for providing the same effect as the taper to the ceramic substrate. In the ceramic substrate 501, the width of the surface of the resistor 502 and the width of the back surface of the ceramic substrate are different. A planar heating element is provided by providing a step 503 and slidingly inserted into a holder 504 formed with a receiver corresponding to the step 503.

Also in the embodiment shown in FIGS. 4 and 5, the bonding between the holder and the ceramic base is unnecessary, and the connection between the contact for external connection and the terminal for taking out the heating element is thermally expanded. Since the position is not affected by the above, the reliability of the connection is high, the thermistor and the heating element are not separated, and the reliability of the temperature control can be further improved.

[0027]

As is apparent from the above description, in the sheet heating element of the present invention, the electrode connection to the outside and the fixing between the heating element and the holder are shifted by expansion and contraction caused by a rise in temperature and effects. Therefore, no stress is generated in this connection portion, and the reliability of connection and fixing is improved. In addition, since the fixing of the heating element and the holder is not bonding, the reliability in the production process is high, and since the thermistor does not separate from the heating element, the reliability of the temperature control also increases.
The danger of smoking and ignition is reduced. Furthermore, even if there is a difference in the thermal expansion characteristics, there is no contact portion or a fixed portion at the place where the displacement occurs, so that there is an effect that the conditions for selecting the material of the holder become wide.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a heating element and a holder of a sheet heating element according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a structural example of an extraction electrode portion of a holder according to the present embodiment.

FIG. 3 is a configuration diagram showing another example of forming an electrode pattern on a ceramic base constituting the planar heating element of the present invention.

FIG. 4 is a configuration diagram of a sheet heating element showing another embodiment of the present invention.

FIG. 5 is a configuration diagram of a sheet heating element showing still another embodiment of the present invention.

FIG. 6 is a configuration diagram showing a general laser printer.

FIG. 7 is a configuration diagram showing a relationship between a heating element of a conventional planar heating element and a holder.

FIG. 8 is a configuration diagram of a heating element and a holder of a planar heating element showing a conventional example.

FIG. 9 is a configuration diagram showing a conventional external connection connector of a sheet heating element.

FIG. 10 is a diagram for explaining a problem in the case where a conventional planar heating element is connected to an external device other than a connector.

[Explanation of symbols]

101, 401, 501, 801 Ceramic substrate 102 Electrode 103, 402, 502, 803 Resistor 104, 405, 802, 1002 Extraction electrode 105 Electrode pattern 106, 407 Contact 107, 804 Concave part 108, 404, 504, 805, 1001,1004
Holder 109 Thermistor receiver 110, 806 Thermistor 201, 406 Tab terminal 403 Tapered section 503 Step 601 Charge section 602 Developing section 603 Photoconductor drum 604 Laser unit 605, 705 Recording paper 606 Transfer section 607 Fixing section 608 Optical signal 609 Controller 701 Endless film 702 Sheet heating element 703 Drive roller 704 Pressure roller 1003 Soldering 1005 Electric wire 1006 Crimping terminal

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-81877 (JP, A) JP-A-6-27840 (JP, A) JP-A-5-273880 (JP, A) JP-A-5-273880 266963 (JP, A) JP-A-5-100586 (JP, A) JP-A-3-150584 (JP, A) JP-A 63-176291 (JP, U) JP-A 59-82987 (JP, U) (58) Field surveyed (Int. Cl. ⁶ , DB name) H05B 3/00 310 G03G 15/20 101 H05B 3/16

Claims (8)

(57) [Claims] 1. A planar heating element in which a resistor is formed in a longitudinal direction on a ceramic substrate or a heat-resistant substrate having a length ratio of not less than 5 to a width of 1. A first electrode pattern, a second electrode pattern connected to the first electrode pattern and formed toward the center in the longitudinal direction of the ceramic base or the heat-resistant base, and the second electrode pattern provided at the center. A planar heating element comprising: an external connection electrode terminal connected to the electrode pattern. 2. The second electrode pattern is formed on the same plane as the resistor and on both sides of the resistor, and is formed on the back surface or the end face in the width direction at the center. The planar heating element according to claim 1, wherein: 3. The method according to claim 1, wherein the second electrode pattern is formed in a surface opposite to a surface on which the resistor is formed, and is formed in the center or on an end surface in a width direction at the center. The sheet heating element according to claim 1, wherein: 4. The method according to claim 1, wherein the second electrode pattern is formed on at least one widthwise end surface of the ceramic substrate or the heat-resistant substrate surface forming the resistor, and is formed in the central portion within the plane or on the surface. 2. The sheet heating element according to claim 1, wherein the sheet heating element is formed on a surface opposite to a surface on which the resistor is formed. 5. A sheet heating element according to claim 1, a contact member of said sheet heating element which contacts said electrode terminal for external connection, and an outer shape of said sheet heating element. And a holder on the inner surface of which a thermistor is disposed so as to be in contact with the planar heating element. 6. An end face shape in a width direction of the planar heating element is as follows:
6. The sheet heating element according to claim 5, wherein a part of or a whole of the longitudinal direction has a taper having a different width between the surface on which the resistor is formed and the opposite surface. 7. The planar heating element according to claim 6, wherein the taper is a step. 8. The sheet heating element according to claim 5, wherein the holder is made of a heat-resistant resin.