JP2005108497A - Heating element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heating element having a self-security function incorporated in the heating element itself, and equipped with a safety mechanism relatively moderately operated when exceeding a predetermined temperature. <P>SOLUTION: By composing this heating element which is formed of an assembly of a positive resistance temperature characteristic heat generation element composed by electrically serially connecting two or more heating parts each having a heat generation part 6 normally mainly generating heat and having small heat generation width and a heat generation part 5 used as a backup heat generation part and having large heat generation width, the heating element capable of always accurately monitoring presence of abnormality in the whole surface of the heating element itself, internally provided with the security function moderately operated in exceeding a predetermined temperature rather than being operated at the last minute, capable of further improving reliability of the heating element, and safely usable for relatively various applications can be provided. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a heating element that can be used as a heat source for heating, heating, drying, and the like.

  Conventionally, as this type of heating element, there is one in which a solid compound that generates a gas by a pyrolysis reaction is mixed in a resistor at a predetermined temperature higher than a normal heating temperature (for example, Patent Documents). 1).

In this heating element, assuming that the resistor burns due to some abnormality or burns due to sparks between the electrodes, a high-temperature state exceeding the normal heating temperature always occurs in the process of reaching such a state. In this state, the compound mixed in the resistor generates a thermal decomposition reaction, generates a space by gas, expands the resistor, and interrupts the conductive path of carbon black contained in the resistor. Due to this action, the resistor prevents abnormal heating and combustion.
Japanese Patent Laid-Open No. 60-180084

  However, the safety function of the conventional heating element is a brilliant function that operates for the first time when a very high temperature condition occurs, and originally prevents such a condition from occurring. A mechanism is desired. Moreover, the reliability of the correctly designed planar heating element is excellent, and it is particularly difficult to assume a mechanism in which the planar heating element having a positive resistance temperature characteristic is abnormally heated. From such a point of view, the conventional heating element is one means as the final safety mechanism, but it has not been adopted as a safety mechanism because almost no functioning scene is assumed. For this reason, the conventional heating element of this type is configured to be able to maintain a predetermined temperature range by a temperature control device, a self-temperature control function, etc., and if such a temperature control function is lost, A system is employed in which an overheat prevention device such as a thermal fuse functions so as not to reach a predetermined temperature. However, there is a limit to the temperature monitoring range of such a safety device, and it is necessary to provide a large number of safety devices when the heat generating surface has a large area. In addition, there are methods to stretch the overheat detection sensor line that can monitor a wide area, or to incorporate a surface temperature sensor, etc., but there are restrictions on the product configuration, a separate control circuit is required, etc. There were many obstacles.

  As described above, the conventional heating element recognizes the operating limit of the safety function, and secures the safety by taking comprehensive measures such as devising the configuration. In addition, among the conventional heating elements, the positive resistance temperature characteristic heating element is apt to be seen in the category of the self-protection function built-in type, but even with such a heating element, as a safety measure in case of failure of one component Security devices such as thermal fuses were often incorporated. Although the present situation is such a situation, originally, it is desirable not to provide a security mechanism at a position apart from the heating element, but to incorporate a self-security function in the heating element itself. In addition, there is a need for a safety mechanism that operates more gently when the temperature exceeds a predetermined temperature, rather than a safety mechanism that has few opportunities to operate effectively and that operates only on the brink. If such a safety mechanism can be realized, the conventional problems will be solved, and the heating element can be used under environmental conditions that could not be used so far, and no components are required to ensure safety. It is thought that very great value will be found, such as improvement of.

  The present invention solves the above-described conventional problems, and the heating element itself constantly monitors the presence or absence of an abnormality on the entire surface of the heating element with high accuracy and does not operate on the brink, but at a predetermined temperature. The purpose is to provide a heating element with a built-in safety function that operates gently when the temperature exceeds the limit, and to further improve the reliability of the heating element so that it can be used with peace of mind in more diverse applications. .

  In order to solve the above-described conventional problems, the heating element according to the present invention has two or more heat generation elements, each having a heat generation part with a narrow heat generation width that generates heat mainly during normal time and a heat generation part with a large heat generation width that becomes a backup heat generation part. It consists of an assembly of positive resistance temperature characteristic heating elements formed by electrically connecting parts in series.

  As a result, the heating element itself constantly monitors the presence or absence of an abnormality on the entire surface of the heating element with high accuracy, and does not operate on the brink, but has a security function that operates gently when a predetermined temperature is exceeded. It is a built-in heating element, further improving the reliability of the heating element, and can be used safely in more diverse applications.

  The heating element of the present invention has a built-in safety function that operates gently when a predetermined temperature is exceeded, further improving the reliability of the heating element, and can be used safely in more diverse applications.

  The first invention is formed by electrically connecting two or more heat generating portions having a heat generating portion having a narrow heat generating width which generates heat mainly during normal time and a heat generating portion having a large heat generating width serving as a backup heat generating portion in series. By using a heating element composed of an assembly of positive resistance temperature characteristics heating elements, the heating element itself constantly monitors the presence or absence of abnormality on the entire surface of the heating element with high accuracy, and does not operate on the brink. It is a heating element with a built-in safety function that operates gently when the temperature exceeds a predetermined temperature, further improving the reliability of the heating element, and can be used with peace of mind in more diverse applications.

  In the second invention, in particular, two or more heat generating portions having different heat generation widths in the first invention are formed through the gradient portion of the heat generation width, so that heat generation having a narrow heat generation width is generated from a heat generation portion having a wide heat generation width. It is possible to suppress a rapid change in voltage gradient, power density, and temperature in the portion leading to the portion, and to eliminate the cause of the occurrence of a locally high temperature and high resistance linear heat generation phenomenon.

  In the third invention, in particular, at least one of the two or more heat generation portions having different heat generation widths in the first invention is formed by the gradient portion of the heat generation width, thereby ensuring a change in the heat generation width. The rate of change of the heat generation width can be made moderate. As a result, it is possible to apply the necessary voltage to the heat generation part with a narrow heat generation width, while suppressing rapid changes in voltage gradient, power density, and temperature, and locally high temperature and high resistance linear heat generation phenomenon Can be prevented.

  According to a fourth invention, in particular, the electrode according to any one of the first to third inventions is composed of a pair of main electrodes having different polarities and a plurality of branch electrodes branched from the main electrodes, and the polarities differing from each other. By arranging the branch electrodes so as to alternately face each other and forming the heat generating elements between the branch electrodes, a planar heat source in which many heat generating elements are assembled can be formed. That is, the heat generating element in which two or more heat generating parts having different heat generation widths are connected in series has a small configuration size for uniform heat generation and thermal coupling, and in order to collect a large number of such heat generating elements, It is necessary to form a large number of electrodes at a narrow interval. A thin electrode is desirable for many arrangements, but on the other hand, a thick electrode is required for the main current to flow. A so-called comb electrode, in which a pair of main electrodes and branch electrodes branched from a pair of main electrodes are alternately arranged, is a very rational form for arranging a large number of electrodes with a narrow electrode interval, and generates a lot of heat. A planar heat source in which many elements are assembled can be formed.

  In the fifth invention, in particular, two or more heat generating portions having different heat generation widths in the fourth invention are alternately formed in the voltage application direction, and branch electrodes having different polarities generate heat having a wide width in the heat generating portions. By alternately forming the central portion of the portion and the narrow heat generating portion, a wide heat generating portion that hardly generates heat at the time of saturation is formed across one branch electrode, and the adjacent branch electrodes are mainly used at the time of saturation. A narrow heat generating portion that generates heat is formed with one branch electrode interposed therebetween. By gathering the wide portion and the narrow portion two by two with the branch electrode in between, a wide heat generating portion and a narrow heat generating portion can be formed as a large block. In order to obtain sufficient heat generation when the area resistance value of the resistor is high, the electrode interval is set narrow, but when the electrode interval is close, the wide portion and the narrow portion are thermally integrated. Therefore, there is a tendency that a sufficient voltage is not distributed to a narrow portion. In such a case, by forming the wide heat generating portion and the narrow heat generating portion as a large block, it is possible to adjust the thermal coupling and to provide an appropriate voltage distribution.

  In the sixth invention, in particular, the positive resistance temperature characteristic resistor having regular defects in the fourth invention is formed on the heat generation surface, and branch electrodes are formed corresponding to the defects, The heat generating element is composed of a wide heat generating portion and a narrow heat generating portion connected in series. By forming a heat generating material having a regular defective portion on the heat generating surface, a heat generating portion having a narrow defective portion. And a portion having no defective portion forms a wide heat generating portion. Since the portion without the defect portion is continuous in the width direction, it seems that the wide heat generation portion is not formed, but considering the potential distribution from the narrow heat generation portion formed in series, it is substantially electric It becomes an independent wide heat generating part. By forming branch electrodes with different polarities at the corresponding positions of the heat generating element consisting of such a wide heat generating part and a narrow heat generating part, a heat generating surface in which many heat generating elements are gathered can be rationally formed. Can do.

  In the seventh invention, in particular, the voltage application direction dimension of the defect portion in the fourth invention is formed smaller than the interval between adjacent branch electrodes having the same polarity, and the branch electrodes having different polarities are connected to the central portion of the defect portion By being alternately formed in the central part between the defect parts, a part without the defect part is formed between the pair of branch electrodes, and this part becomes a wide heat generation part that is substantially electrically independent. . A portion having a defect portion becomes a heat generation portion having a narrow width. The branch electrode passing through the central part of the defect part forms two narrow heating portions sandwiching the branch electrode, and the branch electrode passing through the central part between the defect parts has two widths across the branch electrode. Form a wide exothermic part. By combining the wide exothermic part and the narrow exothermic part two by two with the branch electrode in between, each exothermic part can be formed as a large block. Can be adjusted to provide an appropriate voltage distribution. Further, with this configuration, the pattern setting of the electrodes and the heat generating elements is extremely easy and can be rationally processed.

  In the eighth invention, in particular, the shape of the defect portion in the sixth or seventh invention is formed from a portion whose width increases toward the voltage application direction and a portion whose width decreases. Is formed at the position of the maximum width of the defect portion, and the next branch electrode is formed at an intermediate position between the defect portion and the next defect portion, thereby generating heat generated by the heat generation elements having two or more heat generation portions having different heat generation widths. A surface can be formed. Since the width of the defect portion changes in this way, two or more heat generation portions having different heat generation widths can be formed even if the defect portion is formed continuously in the voltage application direction or independent.

  In the ninth invention, in particular, the shape of the defect portion in the sixth or seventh invention is formed from a portion where the width increases nonlinearly and a portion where the width decreases nonlinearly in the voltage application direction. Thus, by forming one branch electrode at the position of the maximum width of the defective portion and forming the next branch electrode at an intermediate position between the defective portion and the next defective portion, two or more heat generations having different heat generation widths are formed. A heat generating surface in which heat generating elements having portions are gathered can be formed. Further, by changing the heat generation width in a non-linear manner, rapid changes in voltage gradient, power density, and temperature can be suppressed, and the cause of local high temperature and high resistance linear heat generation can be eliminated. In addition, since the width of the defect portion changes in this way, two or more heat generation portions having different heat generation widths can be formed even if the defect portion is formed continuously in the voltage application direction or independent.

  In the tenth invention, in particular, the shape of the defect in the sixth or seventh invention is a substantially circle or an ellipse, so that the circle or ellipse is a rational shape having a non-linear change. The change in the width is moderate at the center, and an abrupt change is obtained at the tip. In particular, by forming a circular or elliptical defect part independently in the direction of voltage application and alternately forming branch electrodes between the center of the defect part and the defect part, the position of the branch electrode is shifted at the center part of the defect part. However, since the change in the width is small, the influence can be minimized. In addition, since the width of the tip of the defect portion changes suddenly and closes, it is possible to draw a pattern that does not reach the defect portion even if the position of the branch electrode between the defect portions is shifted.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 shows a heating element according to Embodiment 1 of the present invention.

  As shown in the figure, the substrate 1 uses a polyethylene terephthalate film having a thickness of 188 μm. The pair of main electrodes 2, 2 ′ is formed on the substrate 1 by thick film printing with a conductive silver paste in which silver powder is dispersed in an epoxy resin. Branch electrodes 3 and 3 ′ are branched from the main electrodes 2 and 2 ′, and a pair of branch electrodes 3 and 3 ′ are alternately arranged. Further, the resistor 4 having the positive resistance temperature characteristic has a wide heat generating portion 5 and a narrow heat generating portion 6 connected in series to form one heat generating element. Resistor 4 having a positive resistance temperature characteristic is a branched electrode obtained by thick film printing by pasting a kneaded mixture of ethylene vinyl acetate copolymer and low structure carbon black using a rubber binder and a high boiling point solvent. 3, 3 '. A heating element is formed by aggregating a large number of heating elements composed of two heating portions having the positive resistance temperature characteristic. The distance between the electrodes of the branch electrodes 3 and 3 'is 4 mm, and a wide heat generating portion 5 and a narrow heat generating portion 6 are formed therebetween. The heat generating part 5 has a width of 10 mm, the heat generating part 6 has a width of 8 mm, and the dimension in the voltage application direction is 2 mm. The heating portions 5 and 6 are each formed in a very small area so that a uniform temperature can be maintained. Further, since the heat generating portion 5 and the heat generating portion 6 are also formed very close to each other, they are thermally coupled within one heat generating element, and are formed within a range where heat is effectively transmitted. The heating element of the present embodiment is formed by gathering 80 such heating elements.

  When this heating element is energized, a voltage is applied to each heating element, and since the resistance is low at the beginning of energization, a large current flows and the temperature starts to rise rapidly. Since the temperatures of the heat generating portion 5 and the heat generating portion 6 are the same at the initial stage of energization, the area resistance values are the same, and the resistance values correspond to the resistor patterns. The ratio of the resistance values of the heat generating portions 5 and 6 is 1 to 1.25, and the current value is the same, so the ratio of power is also 1 to 1.25. The power per area of the heat generating portion, that is, the power density is a ratio of the squares when the area of the heat generating portion 6 is taken into consideration, but the ratio of the power density is substantially equal considering that heat is diffused because the area is small It becomes 1 to 1.25. Eventually, a difference in temperature between the heat generating portions 5 and 6 occurs due to this difference in power density, so that a difference in sheet resistance value due to the positive resistance temperature coefficient occurs, and the resistance value expands from 1: 1.25. As a result of forming a resistor having an area resistance value of 12 kΩ at 20 ° C. and applying 12 V to saturate, the heating portion 5 was heated to 45 ° C. and the heating portion 6 was 53 ° C. When the voltages of the exothermic portions 5 and 6 were measured, they were 3.5 V and 8.5 V, respectively. Since the voltage ratio is the same as the resistance value ratio, the ratio of 1 to 1.25 is expanded to 1 to 2.4. The power density should also increase at this ratio. However, since the heat generating portions 5 and 6 are very close to each other, heat is transferred from the heat generating portions 6 to 5, so that a very large temperature distribution does not occur.

  Further, since most of the voltage and power density are concentrated in the heat generating portion 6, it is necessary to consider the occurrence of a high-temperature and high-resistance linear heat generation phenomenon, but the heat generating portions 5 and 6 are very Since it was formed with a small area, it was confirmed that thermal diffusion was excellent and linear heat generation was not reached. The heat generating portions 5 and 6 have a very small area and generate only a small amount of electric power. However, a large area heat source can be formed by collecting a large number of these heat generating portions 5 and 6. In addition, a partial power density distribution is generated, but thermal uniformity can be obtained without any practical problem by thermal diffusion.

  Usually, a planar heating element having a positive resistance temperature characteristic is covered with an exterior material, and is used while being shielded from oxygen, water, etc., and therefore, a long-term durability can be expected. In addition, it is difficult to assume a mode in which the resistor deteriorates within normal use time because it does not reach a high temperature even if it is held abnormally or kept warm, and it should be confirmed by an accelerated test. Is not easy. Moreover, it has been confirmed that the stress is changed to a safe side under the assumed stress. The reliability of such a heating element is extremely high, and even if a safety device is finally installed, a test condition for confirming it by actually operating it is usually not found. In the heating element of the present embodiment, the heat generating portion 6 mainly generates heat and is exposed to deterioration factors such as voltage stress and heat. However, this also makes the resistor deteriorated within a normal use time, which is in a dangerous state. It is difficult to assume a mode that However, if the heating element deteriorates, it can be assumed that the voltage stress is large and the part is at a high temperature. Therefore, the heat generation portion 6 has a higher probability of being deteriorated compared to 5, and if it is deteriorated, it can be assumed that it is this portion. If the heat generating part 6 deteriorates and attempts to exceed a predetermined temperature, or if the resistance value decreases and exceeds a predetermined current value, heat is generated in the heat generating part 5 provided in series adjacently. The voltage applied to the heat generating portion 6 is absorbed by either the method of generating heat or the heat generating portion 5 itself generating heat, and heat is generated instead of the heat generating portion 6. Since the heat generating portion 5 has almost the same specifications as the heat generating portion 6 except for the heat generation width, it can maintain substantially the same heat generating function.

  In this way, the probability that the narrow heat-generating portion 6 is abnormal cannot be assumed to be low, and the wide heat-generating portion 5 in the same series circuit is similarly low to be unlikely to cause abnormality. The probability that the circuit will be abnormal is substantially zero, and it acts as a heating element with a double safety mechanism by the backup heating part.

  In the present embodiment, the ratio of the heat generation width between the heat generating portion 5 and the heat generating portion 6 is 10 to 8. However, the ratio is not limited to this value, and the same effect can be obtained even if the ratio is changed. . When the ratio is increased, the load of the heat generating portion 6 increases and the heat generating area decreases, so that the saturated power tends to decrease. When the ratio is reduced, the load on the heat generating portion 6 is reduced and the heat generation area is increased, so that the saturated power tends to increase.

  Moreover, although the dimension in the voltage application direction of the heat generating part 5 and the heat generating part 6 is 2 mm, respectively, even if this dimension is changed, the same effect can be obtained. Lowering the area resistance value and increasing the size of the heat generating portion 6 in the voltage application direction increases the area of the heat generating portion 6 and increases the saturation power. However, if the heat generating portion 6 deteriorates, the load on the heat generating portion 5 is increased. Will increase. Conversely, if the area resistance value is increased and the dimension of the heat generating portion 6 in the voltage application direction is reduced, the area of the heat generating portion 6 is reduced and the saturation power is reduced. However, the heat generating portion when the heat generating portion 6 is deteriorated should be reduced. The load of 5 is reduced. In addition, since the probability that a high-temperature and high-resistance linear heat generation phenomenon occurs increases as the size in the voltage application direction increases, it is necessary to keep it within a range where thermal diffusion is possible.

  Even if it is assumed that a linear heat generation phenomenon occurs in the heat generating portion 6 and reaches a dangerous state, there is no safety problem because the power or temperature is reflected in the heat generating portion 5.

  As described above, the heating element according to the present embodiment electrically connects two or more heat generating portions including the heat generating portion 6 having a small heat generation width that mainly generates heat in the normal state and the heat generating portion 5 having a wide heat generation width as a backup heat generating portion. And a series of positive resistance temperature characteristic heating elements connected in series.

  That is, the heat generating portion is formed in a small region capable of substantially uniform heat generation, the heat generating element is formed in a small region capable of thermal coupling, and the heat generating element is connected to a power source via a pair of electrodes. At the start of energization, the heat generating portion in the heat generating element generates heat at a power density substantially inversely proportional to the heat generation width, but at the time of saturation, the heat generating portion 6 having a narrow heat generation width in the heat generating portion. The temperature rises to increase the resistance, and heat is generated mainly by receiving a large voltage distribution and diffuses heat into the heat generating element to saturate as a substantial planar heat source, while the heat generating portion having a narrow heat generating width Double safety heat generation function that can be operated safely by moving most of the voltage to the heat generation portion 5 having a wide heat generation width, assuming that 6 shows heat generation or resistance value deviating from the positive resistance temperature characteristic. The Is Ete become one.

  Accordingly, a security mechanism is not provided at a position apart from the heating element, but a security function is built in the heating element itself. For this reason, there are few opportunities to operate effectively unlike the prior art, and it is not a safety mechanism that operates only on the brink, but a safety mechanism that operates more gently when a predetermined temperature is exceeded. If a heating element equipped with such a safety mechanism is realized, the conventional problems will be solved, and it will be possible to use it in harsh environments that could not be used so far. And design flexibility such as space-saving design, it can be used safely in more diverse applications. In addition, since it is a safety mechanism that the heating element itself detects rather than detecting an abnormality at a distant position, the accuracy is extremely high. Moreover, it is not necessary to add a resistor or a part to add a safety function, and it has extremely excellent features such as simplifying not only the configuration but also the manufacturing process.

(Embodiment 2)
FIG. 2 shows a heating element in Embodiment 2 of the present invention.

  The difference from the first embodiment is that the two heat generating portions having different heat generation widths formed by the resistor 7 having the positive resistance temperature characteristic do not change stepwise but are formed through a gradient portion. is there.

  In the figure, the wide heat-generating portion 8 and the narrow heat-generating portion 9 are connected via a gradient portion whose width decreases. If the heat generation width changes stepwise, abrupt changes such as voltage gradient, power density, temperature, etc. occur, and the heat generation distribution associated therewith may cause a linear heat generation phenomenon. By providing the gradient portion and gradually changing the heat generation width, a rapid change in voltage gradient, power density, temperature, etc. can be suppressed. As a result, it is possible to reliably prevent the linear heat generation phenomenon that is triggered by these factors.

  In the present embodiment, the wide heat generating portion 8 and the narrow heat generating portion 9 are connected via a gradient portion where the width decreases, but they are not connected via a gradient portion. The heat generating part or both of the heat generating parts may have a gradient, and exhibit the same operational effects as in the present embodiment. Further, the gradient may be non-linear, and the gradient can be selected based on an arbitrary mathematical expression.

(Embodiment 3)
FIG. 3 shows a heating element according to Embodiment 3 of the present invention.

  The difference from the first embodiment is that the resistor 10 having the positive resistance temperature characteristic has a high area resistance value, the distance between the branch electrodes is narrowed, and two heat generating portions having different heat generation widths are formed. The array to be made has regularity of two units.

  In the figure, the area resistance value at 20 ° C. of the resistor 10 having the positive resistance temperature characteristic is 16 kΩ. In addition, the two heat generating portions having different heat generation widths are not formed by alternately forming the wide heat generating portions 11 and the narrow heat generating portions 12, but the wide heat generating portions 11 are sandwiched between two branch electrodes. Next, two heat generating portions 12 having a narrow width are formed with another branch electrode interposed therebetween. Further, both the heat generating portion 11 having a wide width and the heat generating portion 12 having a small width in the voltage application direction are formed to be 1.5 mm, and the distance between the opposing branch electrodes 3 and 3 ′ is 3 mm.

  Even though the size in the voltage application direction is reduced because the wide heat generating portion 11 that hardly generates heat during saturation and the narrow heat generating portion 12 that mainly generates heat during saturation are formed in units of two. Each region is formed in a large block unit. In order to obtain sufficient heat generation when the area resistance value of the resistor is high, it is necessary to set the interval between the branch electrodes to be narrow. The heat generation state of the heat generation part becomes thermally integrated, and there is a tendency that a sufficient voltage is not distributed to the heat generation part having a narrow width. In such a case, the two heat generating portions can be thermally separated by grouping them in units of blocks, and appropriate voltage distribution can be provided.

  When 12V was applied to the heating element of this embodiment, the saturation temperatures of the wide heating portion 10 and the narrow heating portion 11 were 44 ° C. and 52 ° C., and the voltages were 3.4V and 8.6V. It was.

(Embodiment 4)
FIG. 4 shows a heating element in Embodiment 4 of the present invention.

  The difference from the third embodiment is the formation pattern of the resistor 13 having a positive resistance temperature characteristic.

  In the figure, a resistor 13 having a positive resistance temperature characteristic is formed on the entire heat generating surface, and a plurality of defective portions 14 are regularly provided on the surface. A branch electrode 3 ′ is formed at the center of the defect 14, and branch electrodes 3 having different polarities are formed at the center of the defect 14 and the next defect 14. Further, the wide heat generating portion 15 is continuous in the direction of the branch electrode 3 and is not formed independently, but the narrow heat generating portion 16 is formed independently. The wide exothermic part 15 formed continuously in the direction of the branch electrode 3 has a property of passing the current flowing through the adjacent exothermic part 16 having a narrow width through the shortest path. The current flowing through the circuit is small, and a series circuit of a wide heat generating portion 15 and a narrow heat generating portion 16 which are substantially electrically independent is formed. Therefore, the present embodiment shows heat generation characteristics that are substantially the same as those of the third embodiment.

(Embodiment 5)
FIG. 5 shows a heating element in Embodiment 4 of the present invention.

  The difference from the fourth embodiment is the shape of the defect 18.

  In the figure, the resistor 17 having the positive resistance temperature characteristic is formed on the entire surface of the heating element, and the oval-shaped defect portions 18 are regularly provided on the surface. A branch electrode 3 ′ is formed at the center of the defect 18, and a branch electrode 3 is formed at the center of the defect 18 and the next defect 18. Further, the wide heat generating portion 19 is continuous in the direction of the branch electrode 3 and is not independently formed, but the narrow heat generating portion 20 is formed independently. Since the wide heat generating portion 19 formed continuously in the direction of the branch electrode 3 has a property of passing the current flowing through the adjacent heat generating portion 20 having a narrow width through the shortest path, The current flowing through the circuit is small, and a series circuit of a wide heat generating portion 19 and a narrow heat generating portion 20 which are substantially electrically independent is formed.

  In the present embodiment, since the shape of the defect portion 18 is an ellipse, the heat generation widths of the wide heat generation portion 19 and the narrow heat generation portion 20 change smoothly in a non-linear manner. When the heat generation width changes abruptly, a rapid change in voltage gradient, power density, temperature, etc. occurs, and the heat generation distribution associated therewith may cause a linear heat generation phenomenon. Abrupt changes such as voltage gradient, power density, and temperature can be suppressed by smoothly changing the heat generation width in a non-linear manner. As a result, it is possible to reliably prevent the linear heat generation phenomenon that is triggered by these factors. Further, the oval-shaped defect portion 18 has a rational shape having a non-linear change, and the change in the width becomes gentle at the central portion in the voltage application direction, and a rapid change is obtained at the tip portion. For this reason, a gradual change in the heat generation width is obtained in the narrow heat generation portion 20, and the heat generation width rapidly expands along the current flow toward the wide heat generation portion 19. In addition, since the change in the width of the defect portion 18 is gentle in the central portion of the elliptical defect portion 18 in the voltage application direction, even if the position of the branch electrode 3 ′ is shifted in the voltage application direction, the heat generation width has an effect. It is difficult to receive, and since its width is rapidly reduced toward the tip of the defect portion 18 and closed, the defect portion 18 does not reach the defect portion 18 even if the position of the branch electrode 3 is shifted in the voltage application direction. There is something.

  In the present embodiment, the shape of the defect 18 is an ellipse and is formed apart in the voltage application direction. However, the adjacent defect 18 can be made closer by being elongated in the voltage application direction. . By adopting such a configuration, since the portion where the wide heat generating portion 19 is continuous in the direction of the branch electrode 3 ′ is reduced, an electrically more completely independent circuit can be obtained. In addition, the shape of the defect portion can be reduced instead of being elongated in the voltage application direction. With this configuration, heat is generated from the wide heat generating portion 19 toward the narrow heat generating portion 20. It is possible to form a pattern whose width is rapidly reduced non-linearly. This is advantageous when it is desired to make the interval between the branch electrodes close to each other, and is also advantageous when it is desired to increase the formation interval of the defect portion in the direction of the branch electrode. In this way, various shapes can be selected even when the shape is an ellipse, and naturally, not only an ellipse but also a circle can be selected. In addition, it is not necessary to accurately draw an ellipse, and an elliptical shape or a substantially elliptical shape has the same functions and effects.

(Embodiment 6)
FIG. 6 shows a heating element in Embodiment 6 of the present invention.

  The difference from the fifth embodiment is the shape of the defect portion 22.

  In the figure, a resistor 21 having a positive resistance temperature characteristic is formed on the entire surface of the heating element, and rhombus-shaped missing portions 22 are regularly provided on the surface. A branch electrode 3 ′ is formed at the center of the defect 22, and a branch electrode 3 is formed at the center of the defect 22 and the next defect 22. The wide heat generating portion 23 is continuous in the direction of the branch electrode 3 and is not formed independently, but the narrow heat generating portion 24 is formed independently. The wide heat generating portion 23 formed continuously in the direction of the branch electrode 3 has a property of passing the current flowing through the adjacent heat generating portion 24 having a narrow width through the shortest path, and therefore, the direction of the branch electrode 3 Is small, and a series circuit of a wide heat generating portion 23 and a narrow heat generating portion 24 which are substantially electrically independent is formed. In the present embodiment, since the shape of the defect portion 22 is a rhombus, the heat generation widths of the wide heat generation portion 23 and the narrow heat generation portion 24 change linearly. When the heat generation width changes abruptly, a rapid change in voltage gradient, power density, temperature, etc. occurs, and the heat generation distribution associated therewith may cause a linear heat generation phenomenon. Abrupt changes in voltage gradient, power density, temperature, and the like can be suppressed by linearly and smoothly changing the heat generation width. As a result, it is possible to reliably prevent the linear heat generation phenomenon that is triggered by these factors.

  Further, the diamond-shaped defect portion 22 has a rational shape having a linear change, and since the rate of change in width is constant toward the voltage application direction, the heat generation portion 23 having a narrow width generates heat. Over the portion 24, the heat generation width decreases at a constant rate along the current flow. Therefore, even if the position of the branch electrode 3 ′ or 3 is shifted in the voltage application direction, the rate of change in the heat generation width does not change, so that it is hardly affected by the voltage gradient, power density, temperature, etc. There is something.

  In the present embodiment, the shape of the defect portion 22 is a rhombus shape and is formed apart in the voltage application direction. However, the adjacent defect portion 22 is made closer or overlapped by being elongated in the voltage application direction. Can be made. By adopting such a configuration, since the portion where the wide heat generating portion 18 is continuous in the direction of the branch electrode 3 ′ is reduced, an electrically more completely independent circuit can be obtained. In addition, the shape of the defect portion of the defect portion 22 can be reduced instead of being elongated in the voltage application direction. With this configuration, the heat generation portion 23 having a wide width can be reduced to the heat generation portion 24 having a small width. On the other hand, it is possible to form a pattern in which the heat generation width decreases linearly and rapidly. This is advantageous when the interval between the branch electrodes is desired to be close, and is also advantageous when it is desired to increase the formation interval of the defect portion in the direction of the branch electrode. In this way, the rhombus shape can be selected in various ways. Naturally, not only the rhombus shape but also a regular quadrilateral shape can be selected. In addition, it is not necessary to accurately draw a rhombus, and the same operation and effect can be achieved with a rhombus or substantially rhombus.

  In the present embodiment, the shape of the defect portion 22 is a rhombus. However, the shape is not limited to a rhombus, and the shape is the same as long as the shape increases or decreases even if the width is linear or non-linear in the voltage application direction. The effects and effects can be brought about. In addition, if the shape is such that the width increases or decreases in the voltage application direction, it is possible to form a wide heat generating portion and a narrow heat generating portion even if the defect portion overlaps in the voltage application direction. Variations can be developed.

  As mentioned above, although each Embodiment 1-6 was demonstrated, this invention is not limited to these Embodiment, Even if the kind of a board | substrate, an electrode, and a resistor changes, the same effect is obtained. . Further, the rate of change of the heat generation width formed in the wide heat generating portion and the narrow heat generating portion, or the shape of the defective portion formed in the resistor is not limited to a specific rate of change or shape. The same effects as those of the embodiment can be obtained even in a multi-step step shape, a curve based on a special function, a combination of a plurality of shapes, etc., which are not shown in the embodiment. Further, the formation interval, size, formation density, and the like of the defect portions are not limited to those in the embodiment. The thermal coupling is maintained, and the balance between heat generation and soaking that does not lead to linear heat generation is maintained. As long as the configuration is more subdivided or integrated, the same effects as those of the embodiment can be obtained.

  As described above, the heating element according to the present invention has a built-in safety function that operates gently when a predetermined temperature is exceeded, and further improves the reliability of the heating element for more various uses. It can be used with peace of mind and can be used as a heat source for various types of heating equipment, heating devices, drying devices and the like.

The top view of the heat generating body in Embodiment 1 of this invention Plan view of a heating element in Embodiment 2 of the present invention Plan view of a heating element in Embodiment 3 of the present invention Plan view of a heating element in Embodiment 4 of the present invention The top view of the heat generating body in Embodiment 5 of this invention The top view of the heat generating body in Embodiment 6 of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Board | substrate 2, 2 'Main electrode 3, 3' Branch electrode 4, 7, 10, 13, 17, 21 Resistor 5, 8, 11, 15, 19, 23 Wide heating part 6, 9, 12, 16 , 20, 24 Narrow exothermic part 14, 18, 22 Defect part

Claims (10)

A positive resistance temperature characteristic heating element in which two or more heating parts having a heating part having a narrow heating range and a heating part having a wide heating range as a backup heating part are electrically connected in series. A heating element consisting of an assembly of The heating element according to claim 1, wherein two or more heat generating portions having different heat generation widths are formed through the gradient portion of the heat generation width. 2. The heating element according to claim 1, wherein at least one of the two or more heating portions having different heating widths is formed by the gradient portion of the heating width. The electrodes are composed of a pair of main electrodes having different polarities and a plurality of branch electrodes branched from the main electrodes, and the branch electrodes having different polarities are alternately arranged opposite to each other, and a heating element is provided between the branch electrodes. The heating element according to any one of claims 1 to 3, wherein the heating element is formed. Two or more heat generating portions having different heat generation widths are alternately formed in the voltage application direction, and branch electrodes having different polarities are alternately arranged in the central portion of the heat generating portion having a wide width and the heat generating portion having a small width. The heating element according to claim 4 formed. The heating element according to claim 4, wherein a positive resistance temperature characteristic resistor having a regular defect portion is formed on a heat generation surface, and a branch electrode is formed corresponding to the defect portion. The voltage application direction dimension of the defect portion is formed smaller than the interval between adjacent branch electrodes having the same polarity, and branch electrodes having different polarities are alternately formed at the center portion of the defect portion and the center portion between the defect portions. The heating element according to claim 4. The heating element according to claim 6 or 7, wherein the shape of the defect portion is formed from a portion whose width increases toward a voltage application direction and a portion whose width decreases. The heating element according to claim 6 or 7, wherein the shape of the defect portion is formed of a portion whose width increases nonlinearly and a portion whose width decreases nonlinearly in the voltage application direction. The heating element according to claim 6 or 7, wherein the shape of the defect portion is substantially a circle or an ellipse.

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