JP4022283B2 - Heating element, fixing device and image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a heating element, a fixing device using the same, and an image forming apparatus.
[0002]
[Prior art]
In an image forming apparatus such as a copying machine, a printer, or a facsimile, a heating element for fixing toner is disclosed in JP-A-6-324586.
[0003]
FIG. 12 is a partially cutaway front view of a conventional heating element.
[0004]
FIG. 13 is also a partially cutaway rear view.
[0005]
FIG. 14 is an enlarged cross-sectional view of the main part.
[0006]
In the figure, 121 is a wiring board made of alumina ceramics, 122 is a thick film resistance heating element, 123 is a first conductor pattern, 124a and 124b are a pair of power receiving terminals, 125 is a first through hole, 126 is a thermistor, 127 Is a second conductor pattern, 128 is a pair of through holes, and 129 is a pair of connection terminals.
[0007]
The thick film resistance heating element 122 is mainly composed of a silver / palladium alloy, and is formed on the surface of the wiring board 121 by screen printing.
[0008]
The first conductor pattern 123 is made of a conductor mainly composed of a silver / platinum alloy, one end of which is connected to one end of the thick film resistance heating element 122, and the middle extends along the thick film resistance heating element 122. The other end is connected to one power receiving terminal 124a.
[0009]
The power receiving terminals 124a and 124b are connected to a connector on the power source side to receive power and are made of a silver / platinum-based conductor. The other power receiving terminal 124 b is directly connected to the other end of the thick film resistance heating element 122.
[0010]
As shown in FIG. 3, the thermistor 126 is chip-shaped, and is fixed by an adhesive 130 at a position facing the thick film resistance heating element 122 on the back surface of the wiring board 121. In FIG. 3, the thermistor 126 and the second conductor pattern 127 of the wiring board 121 are not shown.
[0011]
One end of the pair of second conductive patterns 127 and 127 is connected to the thermistor 126, and the other end is connected to the pair of through holes 128 and 128.
[0012]
The pair of connection terminals 129 and 129 is a silver / platinum-based conductor, and is disposed on the surface of the wiring board 121 and connected to the through hole 128. The connection terminal 129 is connected to a connector provided in the control circuit of the resistance heating element 122, whereby the thermistor 126 is inserted into the temperature control circuit.
[0013]
Then, since this heating element has a small heat capacity of the thick film resistance heating element 122, when the power supply voltage is applied, the action part of the heating element contributing to fixing of the toner instantaneously increases the temperature to the required temperature. There is an advantage that no preheating time is required. For this reason, it is possible to control to generate heat by energizing the heating element only during the fixing operation, and the power consumption can be greatly reduced.
[0014]
Further, the temperature of the thick film resistance heating element 122 is measured by a chip-like thermistor 126 disposed on the back surface of the wiring board, and the temperature of the thick film resistance heating element 122 is adjusted to be constant. Control the energization amount.
[0015]
As another conventional technique, a heating element in which a thermistor is formed by thick film printing has also been proposed.
[0016]
[Problems to be solved by the invention]
However, in any of the conventional techniques, it is extremely difficult to adjust the resistance value and the B constant, which are important in designing the thermistor.
[0017]
Moreover, in the former case, since the thermistor chip is attached using an adhesive, the reliability over a long period of time is not necessarily high.
[0018]
In the latter case, since the resistance value and the B constant are determined by the material composition, the selection range is small.
[0019]
By the way, when this type of heating element is used for fixing, the size of the fixing target, for example, paper, and the conveyance speed differ depending on the specifications of the image forming apparatus in which the heating element is incorporated. It is necessary to change the shape and size of the resistance heating element and change the temperature control method. In order to make such a change using the prior art, it is necessary to design a resistance heating element and a temperature control circuit, which is very laborious and time consuming. As a result, there is a problem that the development cost becomes high and the development period becomes long.
[0020]
An object of the present invention is to provide a heating element provided with a thermal sensor having a desired resistance value and a B constant by improving the structure of the thermistor, and a fixing device and an image forming apparatus using the heating element.
[0021]
[Means for achieving the object]
Heating element of the invention of claim 1 includes a wiring board of electrically insulating; and resistive heating element formed in the wiring board; formed adjacent to each other by a thick film printing heat receiving position of the resistance heating element, and A thermal sensor composed of a plurality of thermistors having different resistance values and B constants connected to each other; a pair of conductor patterns formed on the wiring board and having one end connected to the thermal sensor; and connected to the other end of each conductor pattern And a pair of terminal patterns.
[0022]
In the present invention and each of the following inventions, the definitions and technical meanings of terms are as follows unless otherwise specified.
[0023]
As for the wiring board, the part which forms a heat generating body, a heat sensor, a conductor pattern, and a terminal pattern should just have electrical insulation. What formed the alumina ceramics in plate shape using the doctor blade method etc. can be used.
[0024]
The conductor pattern is suitable for forming by, for example, a thick film forming method using screen printing, but the present invention is not limited to this.
[0025]
The terminal pattern is suitable to be formed by a thick film forming method similarly to the conductor pattern, but the present invention is not limited to this.
[0026]
When the conductor pattern and the terminal pattern are formed by the thick film forming method, a silver / palladium-based conductor can be used, but the present invention is not limited to this.
[0027]
Further, the wiring board is preferably heat-resistant such as ceramics, but heat resistance is not an essential requirement. Of course, the shape of the substrate is arbitrary. Therefore, it is not limited to a flat plate, but may be a three-dimensional shape if necessary.
[0028]
The resistance heating element is not particularly limited in material, shape, size, and manufacturing method, but the most suitable is a thick film resistor formed by printing and baking a conductive paste mainly composed of a silver / palladium alloy by a screen printing method. It is a heating element. According to this thick film resistance heating element, the resistance value of the resistance heating element is set to a required temperature rise in a long heating element capable of satisfactorily fixing toner on a sheet mainly of A4 size which is usually used frequently. It is easy to set so that can be obtained.
[0029]
Further, the resistance heating element can be covered with a protective coat. As the protective coat, a glassy or organic film can be used. Furthermore, if necessary, the resistance heating element can be covered with a protective coat with good moisture resistance, and a protective coat with good wear resistance can be formed thereon.
[0030]
The thermal sensor is composed of a thermistor formed by thick film printing, and the characteristic may be either a negative characteristic thermistor or a positive characteristic thermistor.
[0031]
The thermistor according to the present invention includes a plurality of thermistors having different resistance values and B constants. What is different from each other is that either the resistance value or the B constant is different. Here, the B constant is a numerical value indicating the magnitude of resistance change of the thermistor, and is obtained by the following equation.
[0032]
B = ln (R _T / R ₀ ) / (1 / T−1 / T ₀ )
Here, ln is a constant, R _T is a resistance value at a temperature T (K), and R ₀ is a resistance value at a reference temperature T ₀ (K).
[0033]
In order to give a desired resistance value and a B constant to the thermistor, the material, film thickness, length, arrangement, and the like of the thermistor are appropriately set. The resistance value and B constant of the thermistor can be changed depending on the material, for example, by mixing ruthenium oxide in different ratios with a resistance material in which oxides such as manganese, cobalt, and nickel are combined.
[0034]
The arrangement of the plurality of thermistors can take any connection form. For example, it can be a parallel connection, a series connection, or a series-parallel connection.
[0035]
The heating element of the present invention is suitable for fixing, but is not limited to this, and is applicable to all uses.
[0036]
Furthermore, the thermal sensor can be placed at any position as long as the temperature of the resistance heating element can be sensed. For example, it can be disposed at a position facing the resistance heating element across the wiring board or at a position adjacent to the resistance heating element on the same surface as the resistance heating element.
[0037]
Furthermore, in order to connect the thermal sensor to the temperature control circuit, the thermal sensor is connected to a pair of conductor patterns and terminal patterns, but the thermistor may be printed first, and then the conductor pattern and the terminal pattern may be printed. And vice versa.
[0038]
Furthermore, the thermistor can be covered with a glassy or organic protective coat.
[0039]
Thus, in the present invention, the thermal sensor is composed of a plurality of thermistors having different resistance values and B constants. Therefore, the required characteristics as a thermal sensor and, consequently, a heating element can be obtained only by appropriately setting the combination thereof. Can do. For this reason, it is possible to easily obtain a heating element having characteristics according to the requirements of a device incorporating a heating element such as an image forming apparatus.
[0040]
Therefore, for example, when a heating element is used in the fixing device, an optimum heating element corresponding to the paper size and the conveyance speed can be provided. This means that the equipment can be adapted to various required specifications without changing the design of the temperature control circuit.
[0041]
Further, in the present invention, since the thermal sensor is thick film printing, heat conduction from the heating element to the thermal sensor is performed more quickly than in the chip thermistor, and control with a small amount of temperature fluctuation is possible.
[0042]
The heating element of the invention of claim 2 is an electrically insulating and elongated wiring board; and an elongated resistance heating element mainly composed of a silver / palladium alloy formed by thick film printing along the longitudinal direction of the wiring board; and the terminal connected pattern to the end of the resistance heating element; formed adjacent to each other by a thick film printing heat receiving position of the resistance heating element, and connected to arrayed different resistance values and B constants A thermal sensor composed of a thermistor; a pair of conductor patterns formed on the wiring board and having one end connected to the thermal sensor; and a pair of terminal patterns connected to the other end of each conductor pattern; It is a feature.
[0043]
The present invention is different from claim 1 in that the resistance heating element is formed by thick film printing whose main component is a silver / palladium alloy, and a terminal pattern is connected to the end of the resistance heating element.
[0044]
Therefore, both the resistance heating element and the thermistor, which are the main components, are formed by thick film printing, and if necessary, all of them including the conductor pattern and terminal pattern can be formed by thick film printing. Less.
[0045]
A heating element according to a third aspect of the invention is characterized in that in the heating element according to the first or second aspect, the thermal sensor comprises a plurality of thermistors connected in parallel between a pair of conductor patterns.
[0046]
In the present invention, since a plurality of thermistors are connected in parallel, the resistance value of the entire thermal sensor can be made smaller than that of a single sensor, which is suitable for controlling the heating element at a relatively low temperature.
[0047]
A heating element according to a fourth aspect of the present invention is the heating element according to the first or second aspect, wherein the thermal sensor comprises a plurality of thermistors connected in series between a pair of conductor patterns.
[0048]
In the present invention, since a plurality of thermistors are connected in series, the resistance value of the entire thermal sensor can be made relatively larger than that of a single unit, which is suitable for controlling the heating element at a relatively high temperature. Yes.
[0049]
Further, the resistance value and the B constant can be finely adjusted and set by connecting another thermistor in parallel to the serially connected thermistor.
[0050]
According to the first to fourth aspects of the present invention, the resistance value of the thermal sensor can be managed to a predetermined value with high accuracy by trimming the thermistor with a suitable means such as laser trimming or sandblast trimming after forming the thick film. . Trimming marks are formed by trimming. The direction in which trimming is performed is not particularly limited, but by trimming in a direction perpendicular to the current flow direction, the resistance value can be easily adjusted in a relatively large range.
[0051]
According to a fifth aspect of the present invention, there is provided a fixing device comprising: the heating element according to any one of the first to fourth aspects; and a pressing roller disposed in pressure contact with the heating element. It is a feature.
[0052]
According to the present invention, by using the heating element according to the first to fourth aspects of the present invention, a heat sensor having a desired resistance value and a B constant can be provided, and a fixing device that can meet various required specifications can be obtained.
[0053]
The image forming apparatus having the heating element according to any one of claims 1 to 4 forms a reversal image by attaching toner to the formed electrostatic latent image, and transfers the reversal image to a fixing body to obtain a predetermined image. 6. An image forming means for forming an image; and a fixing device according to claim 5, wherein the image is fixed by melting toner adhering to the fixing member.
[0054]
According to this aspect, it is possible to provide an image forming apparatus that includes the heating element having the configuration of claims 1 to 4 and can meet various required specifications.
[0055]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0056]
FIG. 1 is a front view showing a first embodiment of a heating element of the present invention.
[0057]
FIG. 2 is also a rear view.
[0058]
FIG. 3 is also an enlarged rear view of the main part.
[0059]
In the figure, 1 is a wiring board, 2 is a resistance heating element, 3a and 3b are first terminal patterns, 4 is a first conductor pattern, 5 is a first through hole, 6 is a thermal sensor, and 7 is a pair of first elements. 2 is a conductor pattern, 8 is a second terminal pattern, and 9 is a pair of second through holes.
[0060]
The wiring board 1 is an elongated thin plate made of alumina ceramics.
[0061]
The resistance heating element 2 is a thick film resistance heating element formed by screen-printing a conductive material mainly containing a silver / palladium alloy containing 55% by weight of palladium on the surface of the wiring substrate 1, drying and firing. It is.
[0062]
The first terminal pattern 3 a is disposed on the back surface of the wiring board 1 and is connected to one end of the resistance heating element 2 via the first through hole 5 and the first conductor pattern 4. The other terminal pattern 3 b is disposed on the surface of the wiring board 1 and is directly connected to the other end of the resistance heating element 2.
[0063]
The first conductor pattern 4 is disposed on the surface of the wiring board 1, and one end thereof is connected to the other end of the resistance heating element 2.
[0064]
As can be understood from FIGS. 2 and 3 , the thermal sensor 6 includes a first thermistor 6 a and a second 6 b formed close to each other, and a position facing the resistance heating element 2 on the back surface of the wiring board 1. It is formed by thick film printing. Further, the first thermistor 6 a and the second 6 b are arranged in parallel by being connected between one end of the pair of second conductor patterns 7 , 7 . In addition, a pair of second conductor patterns 7 and 7 are formed in advance on the wiring board 1, and first and second thermistors 6a and 6b are formed thereon.
[0065]
The other end of the second conductor pattern 7 is connected to the second through hole 8.
[0066]
The second through holes 8 are connected to a pair of second terminal patterns 9 disposed on the surface of the wiring board 1.
[0067]
FIG. 4 is an enlarged rear view showing a portion of the thermal sensor in the second embodiment of the heating element of the present invention.
[0068]
In the figure, the same parts as those in FIGS.
[0069]
This embodiment is different from the first embodiment in that laser trimming marks 6 L are formed on the first thermistor 6 a and the second thermistor 6 b . That is, the laser trimming marks 6 L, are adjusted first and second thermistors 6a, the resistance value of 6b to a predetermined value.
[0070]
In the present embodiment, first and second thermistors 6a and 6b are first formed on the wiring board 1, and then second conductor patterns 7 and 7 are formed.
[0071]
FIG. 5 is an enlarged rear view of a main part showing a third embodiment of the heating element of the present invention.
[0072]
In the figure, the same parts as those in FIGS.
[0073]
In the present embodiment, a first thermistor 6a and a second 6b are connected in series. That is, the first and second thermistors 6 a and 6 b are connected in series via the relay terminal 10.
[0074]
FIG. 6 is an enlarged rear view of a main part showing a fourth embodiment of the heating element of the present invention.
[0075]
In the figure, the same parts as those in FIGS.
[0076]
In the present embodiment, three thermistors 6a, 6b, 6c are connected in series and parallel. That is, the thermistors 6a and 6b are connected in parallel between the relay terminal 10 and the one second conductor pattern 7, while the thermistor 6c is connected between the relay terminal 10 and the one second conductor pattern 7. They are connected in series.
[0077]
FIG. 7 is a graph in which a difference due to a change in the connection form of the two thermistors is verified.
[0078]
In the figure, the horizontal axis indicates the temperature t (° C.), and the vertical axis indicates the resistance value (KΩ).
[0079]
A curve A is a temperature-resistance characteristic curve of the first thermistor alone, and the B (32-85) constant is 3032 (K) and the B (180-230) constant is 2902 (K).
[0080]
A curve B is a temperature-resistance characteristic curve of the second thermistor alone. The B (32-85) constant is 2428 (K), and the B (180-230) constant is 2408 (K).
[0081]
On the other hand, the temperature-resistance value characteristic and B constant when these single thermistors are connected in series and in parallel are as follows.
[0082]
A curve C is a temperature-resistance characteristic curve in the case of series connection. The B (32-85) constant is 2621 (K), and the B (180-230) constant is 2526 (K).
[0083]
A curve D is a temperature-resistance characteristic curve in the case of parallel connection. The B (32-85) constant is 2839 (K), and the B (180-230) constant is 2784 (K).
[0084]
From the above results, it can be understood that various resistance values and B constants can be set by using a plurality of thermistors having different resistance values and B constants.
[0085]
FIG. 8 is a partially cutaway front view showing a fifth embodiment of the present invention.
[0086]
In the figure, the same parts as those in FIGS.
[0087]
In the present embodiment, the thermal sensor 6 is disposed adjacent to the resistance heating element 2 on the same surface as the resistance heating element 2. As a result, all the electrical wirings including the resistance heating element 2 and the thermal sensor 6 are arranged on the surface side of the wiring board 1.
[0088]
FIG. 9 is a cross-sectional view showing an embodiment of the fixing device of the present invention.
[0089]
In the figure, reference numeral 11 denotes a heating element having the structure shown in FIGS. Reference numeral 12 denotes a pressure roller, which has a pressure contact relationship with the heating element 11, and the toner 13a adhering to the fixing body 13 is transferred to the heating body 13 by conveying the fixing body 13 with a narrow pressure therebetween. It is melted by the heat of and fixed. Note that a conveyance sheet such as made of polyimide resin may be interposed between the fixing body 13 and the pressure roller 62. Reference numeral 14 denotes a support for the heating element 11. A fixing device main body 15 accommodates the above-described components.
[0090]
FIG. 10 is a conceptual diagram of a copying machine which is a first embodiment of an image forming apparatus including a heating element according to the present invention.
[0091]
In the figure, 16 is a reading device, 17 is an image forming means, 18 is a fixing device, and 19 is a main body of the image forming device.
[0092]
The reading device 16 optically reads the base paper and forms an image signal.
[0093]
The image forming unit 17 forms an electrostatic latent image on the photosensitive drum 17a based on the image signal, and attaches toner to the electrostatic latent image to form a reverse visible image, which is fixed to a fixing body such as paper. To form an image.
[0094]
The fixing device 18 has the structure shown in FIG. 9, and heats and melts the toner adhering to the fixing body to fix it.
[0095]
The image forming apparatus main body 19 accommodates each of the above devices and means 16, 17 and 18, and includes a transport device, a power supply device, a control device, and the like.
[0096]
FIG. 11 is a conceptual diagram of a printer that is a second embodiment of an image forming apparatus including a heating element according to the present invention.
[0097]
In the figure, 21 is an image forming means, 22 is a fixing device, and 23 is a printer body.
[0098]
The image forming unit 21 includes a laser scanner 21a, a photosensitive drum 21b, and the like, and forms an image based on an image signal input from the outside.
[0099]
The fixing device 22 has a structure shown in FIG.
[0100]
The printer main body 23 accommodates the image forming unit 21 and the fixing device 22 and includes a transport device, a power supply device, a control device, and the like.
[0101]
【The invention's effect】
According to each of the first to fourth aspects of the present invention, the thermal sensor that receives the heat of the resistance heating element is configured by a plurality of thermistors having different resistance values and different B constants that are formed close to each other and connected to each other. In addition, since it is connected between one end of a pair of conductor patterns formed on the wiring board, it is possible to provide a thermal sensor having an arbitrary desired resistance value and B constant, and thereby various requirements specifications of the heater-embedded device. it is possible to meet the thermal sensor so is formed by a thick film, the heat conduction from the resistance heating element may provide a heating element that controls small rapid temperature variation range.
[0102]
According to the second aspect of the present invention, it is possible to provide a heating element suitable for fixing in which a thick resistance heating element is also formed.
[0103]
According to the invention of claim 3, in addition, a plurality of thermistors are connected in parallel, so that a heating element suitable for setting the resistance heating element to a relatively high temperature can be provided.
[0104]
According to the fourth aspect of the present invention, a plurality of thermistors are connected in series, so that a heating element suitable for setting the resistance heating element to a relatively high temperature can be provided.
[0105]
According to the invention of claim 5 , it is possible to provide a fixing device having the effects of claims 1 to 4 .
[0106]
Claims 1 to lever using a heating element 4 of the invention, it is possible to provide an image forming apparatus having the effects of claims 1 to 4.
[Brief description of the drawings]
FIG. 1 is a front view showing a first embodiment of a heating element of the present invention. FIG. 2 is also a rear view. FIG. 3 is an enlarged rear view of the main part. FIG. 4 is a second embodiment of the heating element of the present invention. FIG. 5 is an enlarged rear view of a main part showing a third embodiment of a heating element of the present invention. FIG. 6 is a fourth embodiment of a heating element of the present invention. FIG. 7 is a graph showing a difference in connection between the two thermistors and FIG. 8 is a partially cutaway front view showing a fifth embodiment of the heating element of the present invention. 9 is a conceptual diagram showing an embodiment of a fixing device of the present invention. FIG. 10 is a conceptual diagram of a copying machine as a first embodiment of an image forming apparatus of the present invention. FIG. 11 is a schematic diagram of an image forming apparatus of the present invention. 2 is a conceptual diagram of a printer according to an embodiment of the present invention [FIG. 12] A partially cutaway front view of a conventional heating element [FIG. 13] Missing back view [Fig. 14] Similarly, enlarged sectional view of the main part [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Wiring board 6 ... Thermal sensor 6a ... 1st thermistor 6b ... 2nd thermistor 7 ... 2nd conductor pattern 9 ... 2nd through-hole

Claims (5)

An electrically insulating wiring board;
A resistance heating element formed on the wiring board;
A thermal sensor comprising a plurality of thermistors having different resistance values and different B constants, which are formed in proximity to each other by thick film printing at positions where the resistance heating element receives heat;
A pair of conductor patterns formed on the wiring board and connected at one end to the thermal sensor;
A pair of terminal patterns connected to the other end of each conductor pattern;
A heating element comprising: An electrically insulating and elongated wiring board;
An elongated resistance heating element mainly composed of a silver / palladium alloy formed by thick film printing along the longitudinal direction of the wiring board;
A terminal pattern connected to the end of the resistance heating element; a plurality of terminals having different resistance values and different B constants formed in close proximity to each other by thick film printing at positions where the resistance heating element receives heat; A thermal sensor comprising a thermistor;
A pair of conductor patterns formed on the wiring board and connected at one end to the thermal sensor;
A pair of terminal patterns connected to the other end of each conductor pattern;
A heating element comprising: The heating element according to claim 1 or 2, wherein the heat sensor includes a plurality of thermistors connected in parallel between a pair of conductor patterns. The heating element according to claim 1 or 2, wherein the thermal sensor includes a plurality of thermistors connected in series between a pair of conductor patterns. 5. A fixing device comprising: the heating element according to claim 1; and a pressing roller disposed in a pressure contact relationship with the heating element.

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