JP5438961B2 - Ceramic heater and glow plug - Google Patents

Description

  The present invention relates to a ceramic heater and a glow plug. More specifically, the present invention relates to a ceramic heater that has excellent rapid thermal performance, can reduce power consumption and is excellent in durability, and rapid thermal performance, low power consumption and durability. The present invention relates to a glow plug that can achieve both of these at a high level.

  For a diesel engine, various sensors, and the like, a glow plug, a heater for a sensor, a heater for a fan heater, and the like are used in order to assist the start or to activate the sensor early. For example, a diesel engine compresses air sucked into a cylinder and burns by self-ignition by spraying fuel on air that has become hot due to adiabatic compression. However, when starting a diesel engine in winter, In the case of starting the engine, the temperature of the outside air and the engine body is low, so that it is not easy to reach the temperature required for self-ignition only by compression. Therefore, glow plugs are used in diesel engines as a fuel ignition source.

  Such a glow plug heater, sensor heater, fan heater heater, and the like have a structure in which, for example, a resistance heating element formed of, for example, conductive ceramic is embedded in an insulating ceramic base. Things are known. Specifically, in Patent Document 1, “in a ceramic heater type glow plug having a rod-shaped ceramic heater formed by embedding a resistor in an insulating ceramic material, the resistor is made of conductive ceramic. A first heating element formed of a material and embedded in the tip side of the ceramic heater, and a conductive ceramic material having a positive resistance temperature coefficient larger than that of the first heating element, and in series with the first heating element. And a lead portion of the resistor is formed of a conductive ceramic material and is embedded in the insulating ceramic material in a state of being directly connected to the second heat generator. A ceramic heater type glow plug characterized in that it is provided. The “resistor” described in Patent Document 1 is composed of a first heating element and a second heating element formed of a conductive ceramic material.

  As described above, in Patent Document 1, a combination of resistors having different resistance temperature coefficients obtains rapid thermal characteristics, or a predetermined temperature (for example, 1200 ° C.) is kept constant while a constant voltage is applied. A glow plug configured to have a control function has been proposed.

  In general, an energization control device having a function of changing various voltages (effective voltages) applied to a glow plug is used together with the glow plug in order to realize a constant temperature while improving a rapid heating property. There is. In this energization control device, normally, the duty ratio is increased at the initial stage of energization (duty ratio 100%) to increase the effective voltage, and thereafter the temperature is kept constant. Control is performed to apply an effective voltage to the glow plug.

  However, energization of various electronic devices and starter motors are performed when starting the engine, and there is also a spontaneous discharge of the battery. Even if the duty ratio is 100%, a high voltage (Japanese passenger car) In general, 12V) is not always applied to the glow plug. For this reason, it is considered to use a glow plug having a ceramic heater having a low room temperature resistance value in order to have rapid thermal performance even at a low voltage. However, since the room temperature resistance value is low, an inrush current at the start of energization is considered. There is also a drawback that becomes larger. In addition, a plurality of types of conductive ceramic materials are used in order to make the temperature coefficient of resistance and specific resistance different, which increases the number of man-hours required for manufacturing and thus increases the manufacturing cost. From this point of view, it is desirable to use only one type of conductive ceramic material.

  On the other hand, as a ceramic heater for the purpose of reducing power consumption, for example, “made of an insulating ceramic, a rod-like support extending in the axial direction, embedded in the support, and made of one kind of conductive ceramic. A ceramic heater having a resistor, wherein the resistor has a small-diameter portion that is folded back at a tip side of the support, and one end portion of the resistor is connected to both ends of the small-diameter portion via a connecting portion. And a cross-sectional area of the small-diameter portion is 1 / 2.6-1 / 25.5 of a cross-sectional area of the large-diameter portion. “Ceramic heater characterized by being in the range” is described in Patent Document 2.

  The ceramic heater described in this document can reduce power consumption by increasing the cross-sectional area ratio between the large diameter portion and the small diameter portion. However, as described in Patent Document 2, when the ratio is increased, the surface temperature in the cross section of the support may differ greatly depending on the position. By making the cross-sectional area ratio appropriate, that is, by implementing the invention described in Patent Document 2, the problem can be reduced. However, in order to make the surface temperature in the cross section of the support more uniform, the temperature inside the support (resistor) is excessively high, and the low temperature position on the support surface is the heating of the ceramic heater. The temperature must be raised to a level that does not cause a problem as a function, and there is a risk that the current-carrying durability will be reduced. That is, it can be said that power consumption and energization durability are in a trade-off relationship.

  Incidentally, in recent years, ceramic heaters that can be used as glow plug heaters or the like have been required to further reduce power consumption together with a higher level of heat generation performance and durability. In particular, for rapid thermal performance, there is a demand for a glow plug having excellent rapid thermal performance even at a low voltage without reducing the room temperature resistance value.

Japanese Patent No. 3044632 JP 2006-24394 A

  This invention makes it a subject to provide the ceramic heater which has the outstanding quick heat property, can reduce power consumption, and is excellent also in durability. Moreover, this invention makes it a subject to provide the glow plug which can achieve all of quick heat property, low power consumption, and durability at a high level.

As means for solving the problems,
According to a first aspect of the present invention, a resistor formed of conductive ceramic is embedded in a base formed of insulating ceramic, and the resistor includes a pair of lead portions extending in an axial direction of the base and the pair Each of the lead portions extending in the axial direction from each tip portion and having a single heat generating portion formed by connecting the tip portions to each other, wherein the heat generating portion has a pair of intermediate portions. The pair of intermediate portions satisfy the following conditions (1) to (3), the base has a base tip, and the base tip satisfies the following condition (9): Ceramic heater
(1) The diameter of a virtual circumscribed circle that is in contact with each contour line forming each of the pair of cross-sections cut by a plane orthogonal to the axis and includes the pair of cross-sections at the tip of the heat generating portion (2) The total cross-sectional area of the pair of cross-sections decreases toward the tip of the heat generating part. (3) A virtual inscribed contact with each of the contour lines and sandwiched between the pair of cross-sections. The diameter of the circle is constant or decreases toward the tip of the heat generating part. (9) The diameter of the circle is in contact with the contour line forming the base cross section cut by the plane and the base cross section is The diameter of a virtual circumscribed circle included inside decreases toward the tip of the base body. The second aspect of the invention is that the tip portion of the base body and the pair of intermediate portions satisfy the following conditions (12) and (13): The feature A ceramic heater according to claim 1,
(12) When cut along a plane including the axis of the base and the axis of each of the pair of intermediate portions, the contour of the tip of the base, the outer contour of each of the pair of intermediate portions, and the pair of The inner contour line of each intermediate part is linear, the distance between the contour lines of the base end part, the distance between the outer contour lines of each of the pair of intermediate parts, and the inner side of each of the pair of intermediate parts The distance between the contour lines decreases toward the tip of the heat generating portion. (13) When the substrate is cut along a plane including the axis of the base and the axes of the pair of intermediate portions, the axis of the base and the base An angle between the contour line of the tip and θa, an angle between the axis of the base body and the outer contour line of the pair of intermediate portions, θb, an axis line of the base body and an inner contour line of the pair of intermediate portions, Θa ≧ θb, where θc is the angle formed by Claim that satisfy .theta.c 3 is a glow plug comprising comprising a ceramic heater according to claim 1 or 2.

  In the ceramic heater according to the present invention, the heat generating part has a pair of intermediate parts that satisfy the conditions (1) to (3), and the base has a base end that satisfies the condition (9). The volume of the part can be reduced. For this reason, this ceramic heater can reach a predetermined temperature with a small amount of power consumption, and an excellent rapid thermal property can be obtained. As a specific example, even when the voltage applied to the ceramic heater is a low voltage such as an effective voltage of 8 V or less, the effect can be obtained. Further, for example, concentration of stress due to thermal expansion and temperature distribution when a voltage is applied is avoided, and high energization durability and mechanical durability are exhibited. In addition, since the volume of the tip of the base decreases in the tip direction, heat generated from the heat generating portion is efficiently transmitted to the outer surface of the base, and the temperature difference between the heat generating portion and the outside of the tip of the base is reduced. It has better heat resistance and can further reduce power consumption. As a result, since it is not necessary to heat the heat generating part more than necessary, the current-carrying durability is excellent. Therefore, according to the present invention, it is possible to provide a ceramic heater that has excellent rapid thermal performance even at a low voltage without reducing the room temperature resistance value, can reduce power consumption, and is excellent in durability. . Further, since the glow plug according to the present invention includes the ceramic heater according to the present invention, according to the present invention, the glow plug that can achieve all of high speed, low power consumption and durability at a high level. Can be provided.

  A ceramic heater according to an embodiment of the ceramic heater according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic perspective view showing a ceramic heater 1 which is an embodiment of the ceramic heater according to the present invention. FIG. 2 is a schematic cross-sectional view of the ceramic heater 1 shown in FIG. 1 cut along a plane including the axis C and the axis J. As shown in FIGS. 1 and 2, the ceramic heater 1 includes a rod-shaped base body 60 that extends in the direction of the axis C, and a resistor 30 embedded in the base body 60.

  The resistor 30 extends in the direction of the axis C from the pair of lead portions 31, 31 extending in the direction of the axis C of the base body 60, and the respective leading ends of the pair of lead portions 31, 31. And one heat generating portion 33 formed in this manner.

  The pair of lead portions 31, 31 extend to the rear end surface 75 of the base body 60 so as to be substantially parallel along the axis C on both sides of the axis C of the base body 60, and are exposed to the rear end surface 75 of the base body 60. ing. As shown in FIG. 2, the lead portions 31 and 31 are provided with electrode extraction portions 77 and 78 exposed on the outer peripheral surface of the base body 60. FIG. 3A is an enlarged schematic cross-sectional view when the ceramic heater 1 shown in FIG. 1 is cut along a plane including the axis C and the axis J. FIG. 3B is an enlarged schematic cross-sectional view of the ceramic heater 1 shown in FIG. 1 cut along a plane perpendicular to the plane including the axis C and the axis J. Each of the lead portions 31, 31 has a distal end (so that the cross-section when cut along a plane perpendicular to the respective axis J has a substantially constant area in the direction of the axis J (the straight line connecting the center of gravity of the cross-section). It has substantially the same fan-shaped cross-sectional shape from the rear end to the rear end (shown by a broken line in FIG. 3A). Each of the lead portions 31 and 31 is basically formed in the same shape and size as each other, but the shape and size can be appropriately adjusted according to the shape and size of the base body 60, the required temperature, and the like. it can.

  As shown in FIG. 3A, the heat generating portion 33 includes a pair of intermediate portions 40, 40 extending from the respective distal ends of the pair of lead portions 31, 31 toward the distal end side in the axis C direction, and the pair of intermediate portions 40. , 40 and one heat generating tip 50 formed by connecting the tips thereof, and the pair of intermediate portions 40, 40 and the heat generating tip 50 are integrally formed. In order to make it easier to understand the features of the present invention of the pair of intermediate portions 40, 40, the shape of the heat generating portion 33 will be described first. As can be understood from FIG. It has a pointed shape toward the tip.

  FIG. 3C is a cross-sectional view showing a cross-section CP when the ceramic heater 1 shown in FIG. 3A is cut along an arbitrary plane P perpendicular to the axis C in the pair of intermediate portions 40 and 40. . In this example, the shape of the pair of cross-sectional portions 57 and 57 of the pair of intermediate portions 40 and 40 cut by the plane P is a fan shape, but the shape of the cross-sectional portion is appropriately determined depending on the required temperature or the like. The cross-sectional shape may be substantially circular, elliptical, polygonal, or the like.

  The pair of intermediate portions 40, 40 satisfy the condition (1). That is, as shown in FIG. 3, the pair of intermediate portions 40, 40 is in contact with the contour lines forming the pair of cross-sectional portions 57, 57 formed by cutting along the plane P orthogonal to the axis C of the base body 60. In addition, the diameter dCh of the virtual circumscribed circle CCh that includes the pair of cross-sectional portions 57 and 57 decreases toward the tip of the heat generating portion 33. In this example, as shown in FIG. 3C, the virtual circumscribed circle CCh is centered on the center of gravity of each of the pair of cross-sectional portions 57 and 57, and the intersection point O between the plane P and the axis C is defined. It has the smallest diameter at the center.

4 (a) to 4 (c) show a ceramic heater which is an embodiment of the ceramic heater according to the present invention when cut along the planes P ₁ , P ₂ and P ₃ shown in FIG. 3 (a), respectively. the cross-section _{CP 1, CP 2, CP 3} is a sectional view showing, respectively. With reference to FIGS. 3 and 4, for example, a more detailed description will be given by taking as an example the case where the pair of intermediate portions 40, 40 are cut at planes P ₁ , P ₂ , P ₃ orthogonal to the axis C of the base body 60. To do. In cross-section CP ₁ formed by cutting in any plane _{P 1} perpendicular to the axis C of the base body 60, a pair of cross portions ₅₇ P1 to the pair of intermediate portions 40, 40 in this plane _{P 1} is formed by cutting, _{57 P1} respectively And a diameter of a virtual circumscribed circle CCh _{1 including} a pair of cross-sectional portions 57 _P1 and 57 _P1 inside is dCh ₁ . Similarly, virtual circumscribing circle CCh the _second diameter and DCH _2, the plane _{P 3} on the distal end side of the heat generating portion 33 than the plane _{P 2} when taken along a plane _{P 2} of the front end side of the heat generating portion 33 than the planar _{P 1} in the DCH ₃ the diameter of an imaginary circumscribed circle CCh ₃ when cut. At this time, the pair of intermediate portions 40 and 40 satisfy the relationship of dCh ₁ > dCh ₂ > dCh ₃ .

If the diameter dCh of the virtual circumscribed circle CCh decreases toward the tip of the heat generating portion 33, the reduction rate is not particularly limited. Preferably, the decreasing rate of the diameter dCh of the virtual circumscribed circle CCh is the base end of each of the pair of intermediate portions 40 and 40 (in other words, the tip of each of the pair of lead portions 31 and 31. The broken line in FIG. the diameter DCH _a virtual circumscribing circle CCh in), a virtual circumscribing circle of each of the tip pair of intermediate portions 40, 40 (in this example corresponds to the maximum heating unit 55. FIGS. 3 (a) shown by the broken line in.) the diameter difference between the diameter DCH _b of _{CCh dCh a-b = dCh a} -dCh b is 0.1～2.5Mm, particularly preferably, the diameter difference DCH _a-b is in 0.3~2.0mm is there. When the difference in diameter is within the above range, the outer diameter of the pair of intermediate portions 40, 40 is appropriately reduced toward the tip, and the volume thereof is reduced. It has excellent rapid heat characteristics and can further reduce power consumption. The reduction ratio of the diameter dCh is preferably selected from the above range in consideration of the dimensions of the base 60, the dimensions of the pair of intermediate portions 40, 40, the required heat generation temperature, and the like. In this example, the decreasing rate of the diameter dCh is selected from the above range, and the decreasing rate from dCh ₁ to dCh ₂ and the decreasing rate from dCh ₂ to dCh ₃ are constant at the same rate.

  Further, the pair of intermediate portions 40, 40 satisfy the condition (2). That is, as shown in FIG. 3, the pair of intermediate portions 40, 40 has a total cross-sectional area Sch of a pair of cross-sectional portions 57, 57 cut by a plane P orthogonal to the axis C of the base body 60. Decreasing towards the tip of the.

This will be described in more detail with reference to FIGS. The total cross sectional area of the pair of the cross section ₅₇ P1, _{57 P1} in the section CP ₁ and Sch _1, and the total cross-sectional area of the pair of the cross section ₅₇ P2, _{57 P2} in the cross section CP ₂ and Sch _2, in the cross section CP ₃ The total cross-sectional area of the pair of cross-sectional portions 57 _P3 and 57 _P3 is Sch ₃ . At this time, the pair of intermediate portions 40 and 40 satisfy the relationship of Sch ₁ > Sch ₂ > Sch ₃ . The reduction ratio in the total cross-sectional area Sch of the pair of cross-sectional portions 57 and 57 is appropriately adjusted in consideration of the reduction ratio in the diameter dCh. In this example, the decreasing rate from Sch ₁ to Sch ₂ and the decreasing rate from Sch ₂ to Sch ₃ are constant at the same rate.

  When the pair of intermediate portions 40, 40 satisfy the conditions (1) and (2), the volume of the heat generating portion 33, that is, the pair of intermediate portions 40, 40 and the heat generating tip portion 50 is reduced. Stress due to thermal expansion that occurs in the pair of lead portions 31 when the voltage is applied to the pair, stress during handling, and the like are gradually absorbed by the pair of intermediate portions 40 and 40, and these stresses are concentrated on the heat generating tip portion 50. Can be avoided. In addition, since the volume of the heat generating tip 50 is reduced, the heat generating tip 50 has higher heat resistance, can reach a predetermined temperature with little power consumption, and can prevent the heat generating tip 50 from being damaged by the stress. it can. As a result, the resistor 30, particularly the heat generating portion 33, has an excellent rapid heat property, can reach a predetermined temperature with a small amount of power consumption, and can exhibit high energization durability and mechanical durability.

  The pair of intermediate portions 40, 40 satisfies the condition (3) in addition to the conditions (1) and (2). That is, as shown in FIG. 3, the pair of intermediate portions 40, 40 is in contact with the contour lines forming the pair of cross-sectional portions 57, 57 formed by cutting along the plane P orthogonal to the axis C of the base body 60. In addition, the diameter dIh of the virtual inscribed circle ICh sandwiched between the pair of cross-sectional portions 57 and 57 decreases toward the tip of the heat generating portion 33. When the pair of intermediate portions 40 and 40 satisfy the condition (3), it is possible to further improve the rapid thermal performance and further reduce the power consumption. In this example, the virtual inscribed circle ICh is positioned between the pair of cross-sectional portions 57 and 57, and the center of gravity of each of the pair of cross-sectional portions 57 and 57 and the center of the virtual circumscribed circle CCh are in a straight line. And has a minimum diameter centered on an intersection O between the plane P and the axis C.

This will be described in more detail with reference to FIGS. The diameter of an imaginary inscribed circle Ich ₁ in cross-section CP ₁ and diH _1, the diameter of a virtual inscribing circle Ich ₂ in cross-section CP ₂ and diH _2, and diH ₃ a diameter of a virtual inscribing circle Ich ₃ in the cross section CP ₃ To do. At this time, the pair of intermediate portions 40 and 40 satisfy a relationship of dIh ₁ > dIh ₂ > dIh ₃ .

As long as the diameter dIh of the virtual inscribed circle ICh decreases toward the tip of the heat generating portion 33, the reduction rate is not particularly limited. Preferably, the decreasing rate of the diameter dIh of the virtual inscribed circle ICh is such that the diameter dIh _a of the virtual inscribed circle ICh at the proximal end of each of the pair of intermediate portions 40, 40 and the above-mentioned of each of the pair of intermediate portions 40, 40. The diameter difference dIh _a -dIh _{b from} the diameter dIh _b of the virtual inscribed circle ICh at the tip is 1.0 mm or less, and particularly preferably, the diameter difference dIh _a -dIh _b is 0.6 mm or less. When the difference in diameter is within the above range, the outer diameter of the pair of intermediate portions 40, 40 is appropriately reduced toward the tip, and the volume thereof is reduced. It has excellent rapid heat characteristics and can further reduce power consumption.

Adjusting from the above range in consideration of the dimensions of the base 60, the dimensions of the pair of intermediate portions 40, 40, the required heat generation temperature, etc., so that the reduction ratio of the diameter dIh of the virtual inscribed circle ICh is within the above range. Preferably, the diameter dIh _b (corresponding to the maximum heat generating portion 55 in this example) of the virtual inscribed circle ICh at the tip of each of the pair of intermediate portions 40, 40 is 0.2 to 2.0 mm. More preferably, it is in the range of 0.2-1.0 mm. When the diameter dIh _b is within the above range, the volume of the heat generating portion 33 is reduced. Therefore, while maintaining the durability of the heat generating portion 33, the heat generating portion 33 can be more quickly heated and the power consumption can be further reduced. In addition, it is possible to effectively prevent disconnection of the resistor 30 due to migration. The migration is a phenomenon in which metal ions, for example, aluminum ions in the grain boundary phase of the substrate move with an applied voltage when the resistor 30 is energized. In this example, the reduction rate of the diameter dIh is selected from the above range, and the reduction rate from dIh ₁ to dIh ₂ and the reduction rate from dIh ₂ to dIh ₃ are constant at the same rate.

The conditions (1), (2) and (3) and the condition (9) described later will be described by arbitrarily selecting the planes P ₁ , P ₂ and P ₃ as the plane P. In the present invention, The plane P is not limited to the three types of planes P ₁ , P ₂ , and P ₃ , as long as the conditions (1), (2), (3), and (9) are satisfied in at least two arbitrary planes. Good.

  The heat generating tip 50 is formed in a substantially arc shape or a substantially U shape starting from the tip of each of the pair of intermediate portions 40, 40 satisfying the above conditions. The heat generating tip 50 is formed to be thin so that the cross-sectional area in the extending direction is small, and the maximum heat generating portion 55 (the part that reaches the highest temperature when a voltage is applied to the resistor 30) has the smallest cross-sectional area. In general, the pair of intermediate portions 40 and 40 are positioned in the vicinity of the tip of each of the pair of intermediate portions 40 and 40. Thus, since the highest heat generating portion 55 of the resistor 30 is usually present at the heat generating tip portion 50, the cross-sectional area of the tip portion in each of the pair of intermediate portions 40, 40 is the same as the cross-sectional area of the highest heat generating portion 55 or It should be set large.

The maximum heat generating portion 55 present in the heat generating front end portion 50 preferably has a cross-sectional area of 0.05 to 1.20 mm ² when cut by a plane perpendicular to the extending direction of the maximum heat generating portion 55. . When the cross-sectional area of the maximum heat generating portion 55 is within the above range, high heat resistance and power consumption can be reduced, and the concentration of stress acting during energization can be dispersed to further improve energization durability. To do.

  More preferably, the maximum heat generating portion 55 has a cross-sectional area of 1/60 to 1 / 2.6 with respect to the cross-sectional area of the lead portion 31. Here, the cross-sectional area of the lead portion 31 is a cross-sectional area when the lead portion 31 is cut along a plane perpendicular to the axis C. When the cross-sectional area of the maximum heat generating portion 55 is within the above-mentioned ratio, the ratio of the cross-sectional area of the maximum heat generating portion 55 to the cross-sectional area of the lead portion 31 is in an appropriate range, and excellent in rapid heat performance, low power consumption, and durability. In addition, the heat generation temperature of the highest heat generating portion 55 becomes even more uniform. Therefore, when this ceramic heater 1 is used as a heater for the glow plug 20, it is excellent in quick heat performance, low power consumption and durability, and excellent in engine startability.

  Specifically, the heat generating portion 33 having a pair of intermediate portions 40, 40 and a heat generating tip 50 has a pair of intermediate portions 40, 40 as a part of the outer peripheral surface as shown in FIG. It has a pointed shape from the tip of each of the pair of lead portions 31, 31 to the heat generating tip 50 with the portion 50 as the top. That is, in the pointed shape, the pair of intermediate portions 40, 40 extend from the tips of the pair of lead portions 31, 31 toward the heat generating tip 50 with both the outer diameter and the interval in the JJ plane direction decreasing. And one heating tip 50 extends from each of the line portions. In other words, the heat generating portion 33 has a conical shape or a tapered shape that penetrates in a direction perpendicular to the JJ plane and has a vertical space portion 59 whose interval gradually narrows toward the tip at the top. Furthermore, the heat generating portion 33 is formed so that the heat generating tip portion 50 gathers at one point on the axis C as shown in FIGS. 1 and 3. In other words, as shown in FIG. 3, the pair of intermediate portions 40, 40 has a tapered shape in which both the cross-sectional shape in the JJ plane and the side shape viewed from the direction perpendicular to the JJ plane decrease toward the tip. Yes.

  Therefore, as shown in FIG. 3C, the pair of intermediate portions 40, 40 has a pair of cross-sectional portions 57, 57 in the plane P, which are similar to each other. And when the heat generating part 33 is formed in this way, it has excellent rapid heat characteristics, can reach a predetermined temperature with a small amount of power consumption, and can exhibit high energization durability and mechanical durability. And can be very easily formed.

  In the heat generating part 33, the length Lh in the axis C direction (see FIG. 3A) is preferably 0.5 to 20 mm. When the length Lh in the axis C direction of the heat generating portion 33 is within the above range, the effect of satisfying the conditions (1) and (2) can be sufficiently exerted, and when the voltage is applied, the lead The boundary temperature between the portion 31 and the intermediate portion 40 becomes relatively low, and breakage of the boundary portion between the lead portion 31 and the intermediate portion 40 can be effectively prevented.

  As shown in FIGS. 1 to 3, the base body 60 in which the resistor 30 is embedded has the same diameter part 70 in which the pair of lead parts 31, 31 are embedded, and the base end part 80 in which the heat generating part 33 is embedded. doing. The base end portion 80 is a portion in which the pair of intermediate portions 40 and 40 are embedded, and specifically, for example, is a portion located at the front end with respect to the broken line shown in FIG.

  The same-diameter portion 70 is a rod-like body extending in the direction of the axis C, and has a shape and a size capable of incorporating a pair of lead portions 31 and 31. In the ceramic heater 1, the same-diameter portion 70 is a rod-shaped body or columnar body having a substantially circular or elliptical cross section.

  The base end portion 80 is shaped into a pointed shape following the shape of the heat generating portion 33, that is, formed into a pointed shape substantially similar to the heat generating portion 33 except that it does not have the vertical space portion 59, The heat generating portion 33 is surrounded from the outer peripheral side. Therefore, the base end portion 80 satisfies the condition (9). That is, the base end portion 80 is in contact with the contour line forming the base cross section 87 cut along the plane P, and the diameter DCb of the virtual circumscribed circle CCb that includes the base cross section 87 is directed toward the tip of the base 60. It is decreasing. When the base end portion 80 satisfies the condition (9), the volume of the base end portion becomes small, so that the heat generated from the heat generating tip portion 50 can be efficiently transmitted to the outer peripheral surface of the base body 60, and the rapid thermal performance is further increased. Improvement, further reduction of power consumption, improvement of energization durability and higher heat generation uniformity can be achieved. Further, since the temperature difference between the heat generating tip 50 and the outside of the base tip 80 becomes small, the temperature can be rapidly raised at a low voltage, and when the base tip 80 is brought to a desired temperature, the resistor 30 As a result, it is excellent in durability. Furthermore, since the resistor sectional area with respect to the sectional area of the substrate section 87 cut along the plane P is increased, the stress acting on the resistor 30 can be relieved and the durability is excellent.

  In this example, as shown in FIG. 3C, the virtual circumscribed circle CCb is the outer periphery of the base section 87 and its center coincides with the center of gravity of the base section 87, and the plane P and the axis C And has a minimum diameter centered on the intersection O. The shape of the cross section 87 of the substrate can be appropriately adjusted according to the required temperature and the like, and the shape may be substantially circular, elliptical, polygonal, etc. From the viewpoint of uniformity and durability, it is preferable that the shape is substantially circular.

This will be described in more detail with reference to FIGS. For example, the diameter of a virtual circumscribed circle CCb ₁ that contacts each contour line forming the base cross section 87 _P1 in the cross section CP ₁ and includes the base cross section 87 _P1 is DCb ₁ . Similarly, the diameter of an imaginary circumscribed circle CCb ₂ in cross-section CP ₂ and DCb _2, the diameter of the imaginary circumscribed circle CCb ₃ in the cross section CP ₃ and DCb _3. At this time, the base end portion 80 satisfies the relationship of DCb ₁ > DCb ₂ > DCb ₃ .

If the diameter DCb of the virtual circumscribed circle CCb decreases toward the tip of the base body 60, the reduction rate is not particularly limited. Preferably, the decreasing rate of the diameter DCb of the virtual circumscribed circle CCb is the diameter of the virtual circumscribed circle CCb at the base end of the base body distal end portion 80 (in other words, the distal end of the same diameter portion 70; indicated by a broken line in FIG. 3A). and DCb _a, the diameter difference between the diameter DCb _b virtual circumscribed circle CCb the outer peripheral surface of the base tip 80 up to the heat generating portion 55 corresponds to a buried position _{DCb a-b = DCb a -DCb} b 0.1 is 2.5 mm, particularly preferably, the diameter difference _{DCb a-b} is 0.3 to 2.0 mm. When the difference in diameter is within the above range, the heat generated from the heat generating tip 50 can be more efficiently transmitted to the outer peripheral surface of the base body 60 while maintaining the cantilever strength.

The reduction ratio of the diameter DCb is preferably selected from the above range in consideration of the dimensions of the base tip 80, the heat generating tip 50, the required heat generating temperature, and the like. In this example, the reduction rate of the diameter DCb is selected from the above range, and the reduction rate from DCb ₁ to DCb ₂ and the reduction rate from DCb ₂ to DCb ₃ are constant at the same rate.

It can also be said that the decrease in the diameter DCb in the virtual circumscribed circle CCb is the decrease in the cross-sectional area SCb in the base section 87. That is, in the base end portion 80, the virtual cross-sectional area SCb of the base cross section 87 cut by the plane P decreases toward the front end of the base 60, as in the pair of intermediate portions 40 and 40. Specifically, the base member distal end portion 80, and the virtual cross-sectional area SCb ₁ of the base cross section _{87 P1,} the virtual cross-sectional area SCb ₂ of the base cross section _{87 P2,} and the virtual cross-sectional area SCb ₃ of the base cross section _{87 P3} SCb ₁ > SCb ₂ > SCb ₃ is satisfied. Here, the virtual sectional area SCb of the base section 87 is a sectional area calculated from the diameter DCb of the virtual circumscribed circle CCb.

  The base end portion 80 and the pair of intermediate portions 40, 40 satisfy the condition (12). That is, as shown in FIG. 3A, the pair of intermediate portions 40, 40 has a base when cut along a plane including the axis C of the base 60 and the axis J of each of the pair of intermediate portions 40, 40. The contour line of the distal end portion 80, the outer contour line of each of the pair of intermediate portions 40, 40, and the inner contour line of each of the pair of intermediate portions 40, 40 are linear, and the contour lines of the base end portion 80 are , The distance between the outer contour lines of each of the pair of intermediate portions 40, 40, and the distance between the inner contour lines of each of the pair of intermediate portions 40, 40 decrease toward the tip of the heat generating portion 33. doing. When the base end portion 80 and the pair of intermediate portions 40, 40 satisfy the condition (12), the contour line of the base end portion 80, the outer contour line of each of the pair of intermediate portions 40, 40, and the pair of intermediate portions Since the inner contour lines of 40 and 40 are linear and do not have irregularities or the like, thermal stress is concentrated when a voltage is applied to the resistor 30, and local temperature rise is reduced. can do. Further, the distance between the contour lines of the base end portion 80, the distance between the contour lines outside each of the pair of intermediate portions 40, 40, and the distance between the contour lines inside each of the pair of intermediate portions 40, 40 are the heat generating portions. Since it decreases toward the tip of 33, it is possible to prevent thermal stress from concentrating on the heat generating tip 50. Therefore, the ceramic heater 1 has an excellent rapid heat property, can reach a predetermined temperature with a small amount of power consumption, and at the same time can exhibit higher energization durability.

  In this example, when the cutting edge is cut along a plane including the axis C of the base 60 and the axis J of each of the pair of intermediate portions 40, 40, the heat generating tip 50 surrounds the outermost end of the base tip 80 surrounding the outer periphery. The tip has a substantially arc shape or a substantially U shape that is substantially the same as the shape of the heat generating tip portion 50, and is smoothly continuous with a linear contour line at the base tip portion 80. Further, the linear contour line of the base end portion 80 smoothly continues to the linear contour line of the same diameter portion 70. In this example, since the base end portion 80 has a tapered shape, the base body 60 is not only cut when cut along a plane including the axis C of the base 60 and the axis J of each of the pair of intermediate portions 40 and 40. Even when the substrate is cut along an arbitrary plane including only the axis C, the outline of the base end portion 80 is linear. Similarly, since each of the pair of intermediate portions 40 and 40 has a tapered shape, it is not only when cut along a plane including the axis C of the base 60 and the axis J of each of the pair of intermediate portions 40 and 40. Even when cut along an arbitrary plane including only one of the axis lines J of the intermediate portion 40, the contour line of the intermediate portion 40 is linear.

  The base end portion 80 and the pair of intermediate portions 40, 40 satisfy the condition (13) in addition to the condition (12). That is, when the pair of intermediate portions 40, 40 are cut along a plane including the axis C of the base 60 and the axes J of the pair of intermediate portions 40, 40, as shown in FIG. , The angle between the axis C of the base 60 and the contour of the base end 80 is θa, and the angle between the axis C of the base 60 and the outer contour of the pair of intermediate portions 40, 40 is θb, Assuming that the angle formed by the axis C of the base body 60 and the contour lines inside the pair of intermediate portions 40 and 40 is θc, θa = θb> θc is satisfied. If the base end portion 80 and the pair of intermediate portions 40, 40 satisfy the condition (13), the intermediate portion 40 becomes thinner toward the front end direction of the heat generating portion 33, and the volume of the heat generating portion 33 is reduced. While maintaining the durability of the heat generating portion 33, it is possible to further improve the rapid thermal performance and further reduce the power consumption. Further, since the distance between the outer peripheral surface of the intermediate portion 40 and the outer peripheral surface of the base end portion 80 is constant or decreases toward the front end direction of the heat generating portion 33, the heat generated from the heat generating front end portion 50 is more efficiently generated. 80 can be transmitted to the outer peripheral surface. Therefore, it is possible to further improve the rapid heat performance and further reduce the power consumption. As a result, when the base end portion 80 is set to a desired temperature, it is not necessary to heat the heat generating portion 33 more than necessary. Also excellent.

  The angles θa, θb, and θc are not particularly limited as long as θa ≧ θb> θc and 0 <θa, θb, θc <50 ° are satisfied. The angles θa, θb, and θc are preferably adjusted from the above range in consideration of the dimensions of the base body 60, the dimensions of the pair of intermediate portions 40, 40, the required heat generation temperature, etc., but θa ≧ It is preferable that θb> θc and 0 ° <θa, θb, θc <20 °, and it is particularly preferable that θa ≧ θb> θc and 0 <θa, θb, θc <15 °. When the angles θa, θb, and θc are within the above ranges, the volume of the heat generating portion 33 is appropriately reduced toward the tip direction, and the distance between the heat generating portion 33 and the base end portion 80 can be appropriately maintained. Therefore, the heat generated from the heat generating portion 33 can be more efficiently transmitted to the outer peripheral surface of the base end portion 80, and as a result, it is possible to achieve an improvement in rapid heat performance, a reduction in power consumption, and a high energization durability.

Here, the absolute value of the circumscribed circle diameter difference between the diameter difference _{DCH a-b} in a virtual circumscribing circle CCh the diameter difference _{DCb a-b} in a virtual circumscribing circle _{CCb | DCb a-b -dCh a} -b | is 0. It is preferably 1 to 2.6 mm, and particularly preferably 0.3 to 2.6 mm. When the absolute value of the circumscribed circle diameter difference is within the above range, the position where the heat generating tip 50 is embedded is not too close to or far from the outer surface of the base tip 80, and the heat generating tip 50 is embedded. The thickness of the base end portion 80 becomes an appropriate thickness, and heat generated from the heat generating front end portion 50 can be transmitted to the outer peripheral surface of the base body 60 more efficiently and quickly, resulting in fast heat performance, low power consumption and durability. Can be achieved at a much higher level.

  In the ceramic heater 1, the position of the heat generating tip 50 embedded in the base 60 is within a range of 0.3 to 1.2 mm from the outer surface of the base tip 80 toward the rear end in the axis C direction. It is preferable that the thickness of the tip 80 is a position where the thickness is 0.3 to 1.2 mm. When the heat generating tip 50 is embedded in the position, when the ceramic heater 1 is heated to a predetermined temperature, it is not necessary to heat the heat generating tip 50 more than necessary, so that the heat generating tip 50 has excellent durability. At the same time, it is excellent in rapid heating and uniform heating. Further, when the ceramic heater 1 is used as a heater for a glow plug, even if the base 60, particularly the heat generating tip 50, is eroded at a high temperature by impurities such as Ca contained in the engine oil, the heat generating tip 50 remains at the tip of the base. It is difficult to be exposed from the portion 80 and durability is improved, and a change in resistance value can be prevented.

As an example of the dimensions of the ceramic heater 1 (excluding the above-mentioned dimensions), the total length (length in the axis C direction) of the ceramic heater 1 is 30 to 50 mm, and the diameter of the ceramic heater 1 (same diameter portion 70) is 2. 5 to 4.0 mm, the minimum thickness of the ceramic heater 1 (excluding the base end portion 80) is 100 to 500 μm, the length of the base end portion 80 in the axis C direction is 0.5 to 20 mm, and the pair of lead portions 31 and 31 The axis line JJ interval is 0.2 to 2 mm.
The smaller the diameter of the ceramic heater, the better the low power consumption and quick heat and the better the durability. Conversely, the smaller the diameter, the lower the mechanical strength of the ceramic heater and the heat generation volume. Since it becomes small, engine startability will worsen. For this reason, the diameter of the ceramic heater is preferably selected from the above range in consideration of the required heat generation temperature and the like.

  Whether or not the ceramic heater 1 satisfies the above conditions (1) to (3), (9), (12) and (13), the position of the heat generating tip 50, etc. are transmitted through the ceramic heater 1 through X-rays, for example. This can be confirmed using a photographic film obtained by photographing.

  As shown in FIG. 5A, the ceramic heater 2 of another embodiment of the ceramic heater according to the present invention has a diameter dIh of the virtual inscribed circle ICh in the condition (3) toward the tip of the heat generating portion 34. The configuration is basically the same as that of the ceramic heater 1 except that it is constant. The heat generating portion 34 of the ceramic heater 2 extends so that the outer diameters of the pair of intermediate portions 41, 41 having a constant interval decrease toward the tip, and one heat generating tip 50 is provided from each of the tips. The pointed shape is formed to be extended, and the base end portion 81 is formed into a shape similar to that of the heat generating portion 34 except that the vertical space portion 59 is not provided. The ceramic heater 2 satisfies all the conditions (1) to (3), (9), (12) and (13). As described above, when the diameter dIh of the virtual inscribed circle ICh is constant, the intermediate portions 41 and 41 can be easily formed, and the mechanical characteristics and energization durability can be further improved.

  As shown in FIG. 5 (b), the ceramic heater 3 of another embodiment of the ceramic heater according to the present invention has a reduction ratio of the diameter dCh of the virtual circumscribed circle CCh in the condition (1) and the condition (2). The reduction ratio of the total cross-sectional area Sch in FIG. 2 is not constant, but is greatly reduced in the substantially central portion in the axis C direction. The reduction ratio of the diameter DCb of the virtual circumscribed circle CCb and the reduction ratio of the cross-sectional area SCb In contrast to the condition (12), the outline of the base end portion 82 and the outer outline of each of the pair of intermediate portions 42 and 42 are directed toward the axis C. The structure is basically the same as that of the ceramic heater 1 except that a concave curve is formed. In the heat generating portion 35 of the ceramic heater 3, the outer diameter of the pair of intermediate portions 42, 42 having a distance decreasing toward the tip decreases toward the tip, and the outer peripheral surface forms a concave curved surface in the axis C direction. Except that the tip portion 82 of the base has no vertical space 59, and the tip portion 82 has a vertical shape. It is formed in a pointed shape substantially the same as 35. This ceramic heater 3 satisfies the conditions (1) to (3) and (9).

As shown in FIG. 5 (c), the ceramic heater 4 according to yet another embodiment of the ceramic heater according to the present invention has a single heating tip 51 extending from each of the pair of intermediate portions 40, 40. Is basically formed in a convex shape toward the tip, and the angles θa, θb and θc satisfy θa <θb> θc contrary to the condition (13), Are similarly configured. Then, the absolute value of the circumscribed circle diameter difference _{| DCb a-b -dCh a-} b | is adjusted to be larger than the ceramic heater 1 in the above range. This ceramic heater 4 satisfies the conditions (1) to (3), (9) and (12).

  As shown in FIG. 5D, the ceramic heater 5 according to another embodiment of the ceramic heater according to the present invention is the above except that the lead portion is formed by a lead wire 31c and a connecting portion 31b. This is basically the same as the ceramic heater 1. This ceramic heater 5 satisfies all the conditions (1) to (3), (9), (12) and (13).

  As shown in FIG. 5E, the ceramic heater 6 according to another embodiment of the ceramic heater according to the present invention has a reduction ratio of the diameter dCh of the virtual circumscribed circle CCh in the condition (1) and the condition (2). The ratio of reduction in the total cross-sectional area Sch is not constant, but is decreased slightly in the substantially central part in the direction of the axis C, and the diameter dIh of the virtual inscribed circle ICh in the condition (3) is constant toward the tip of the heat generating part 36. The decrease ratio of the diameter DCb and the decrease ratio of the cross-sectional area SCb of the virtual circumscribed circle CCb in the condition (9) are decreased slightly in the substantially central portion in the direction of the axis C, and the condition (12) On the other hand, except that the contour of the base end portion 82 and the outer contour of each of the pair of intermediate portions 42 and 42 form a convex curve in the radial direction of the axis C. Motor 1 and is constructed in essentially the same manner as. The heat generating portion 36 of the ceramic heater 6 is formed such that the outer diameter of the pair of intermediate portions 43, 43 having a constant interval decreases toward the tip, and the outer peripheral surface forms a convex curved surface in the axis C direction. The heat generating portion 36 is substantially the same as the heat generating portion 36 except that it has a pointed shape in which one heat generating front end portion 50 extends from each of the front ends, and the base end portion 83 does not have the vertical space portion 59. It is formed in the same pointed shape. This ceramic heater 6 satisfies the conditions (1) to (3) and (9).

  In another embodiment of the ceramic heater 7 according to the present invention, as shown in FIG. 6A, the angles θa, θb and θc in the condition (13) satisfy θa> θb> θc. Except for this, the construction is basically the same as the ceramic heater 1. The ceramic heater 7 satisfies all the conditions (1) to (3), (9), (12) and (13).

  The ceramic heater 8 according to another embodiment of the ceramic heater according to the present invention is such that the values of the angles θa, θb and θc in the condition (13) are smaller than those of the ceramic heater 1 as shown in FIG. Except for the above, the construction is basically the same as that of the ceramic heater 1. The ceramic heater 1 satisfies all the conditions (1) to (3), (9), (12) and (13).

As shown in FIG. 6C, the ceramic heater 9 of another embodiment of the ceramic heater according to the present invention has the angles θa, θb and θc satisfying θa <θb> θc, contrary to the condition (13). Except for satisfy | filling, it is comprised similarly to the ceramic heater 1 fundamentally. Then, the absolute value of the circumscribed circle diameter difference _{| DCb a-b -dCh a-} b | is adjusted to be larger than the ceramic heater 1 in the above range. This ceramic heater 9 satisfies the conditions (1) to (3), (9) and (12).

The ceramic heater 10 according to another embodiment of the ceramic heater according to the present invention, except that the values of the angles θb and θc in the condition (13) are smaller than those of the ceramic heater 1 as shown in FIG. This is basically the same as the ceramic heater 1. Then, the absolute value of the circumscribed circle diameter difference _{| DCb a-b -dCh a-} b | is adjusted smaller than the ceramic heater 1 in the above range. The ceramic heater 10 satisfies all the conditions (1) to (3), (9), (12) and (13).

  As shown in FIG. 7 (a), the ceramic heater 11 according to another embodiment of the ceramic heater according to the present invention includes a pair of intermediate portions 46, 46 partially including the conditions (1) and (2 ) And that the outer contour of each of the pair of intermediate portions 46 and 46 is not linear in a part thereof, contrary to the condition (12). Are similarly configured. That is, the heat generating part 34 of the ceramic heater 11 has an annular bulge centered on the axis C on the outer peripheral surface slightly on the tip side than the central part in the axis C direction, except for the heat generating part 34. It is formed in the same pointed shape. Therefore, this ceramic heater 11 satisfies the conditions (1) to (3) and (9).

  In another embodiment of the ceramic heater 12 according to the present invention, as shown in FIG. 7 (b), a pair of intermediate portions 47, 47 each satisfy the above condition (3). It is basically the same as the ceramic heater 1 except that the inner contour lines of each of the pair of intermediate portions 47 and 47 are not linear in part against the condition (12). It is configured. That is, the heat generating portion 39 of the ceramic heater 12 has a protruding portion extending in a direction perpendicular to the JJ plane on the inner surface of the central portion in the direction of the axis C, and in the JJ plane direction on the tip side of the protruding portion. Except for the fact that the interval is reduced, it is formed into a pointed shape substantially similar to that of the heat generating portion 34. Therefore, this ceramic heater 12 satisfies the conditions (1) to (3) and (9).

  As shown in FIG. 7C, the ceramic heater 13 according to yet another embodiment of the ceramic heater according to the present invention has a pair of intermediate portions 48, 48 each having the above-mentioned conditions (1) and ( 2) Basically the same as the ceramic heater 1 except that the outer contour of each of the pair of intermediate portions 48, 48 is not linear, contrary to the condition (12). It is configured. That is, the heat generating portion 32 of the ceramic heater 13 has substantially the same pointed shape as the heat generating portion 34 except that both the outer diameter and the interval in the JJ plane direction are gradually reduced toward the heat generating front end portion 50. Molded. Therefore, this ceramic heater 13 satisfies the conditions (1) to (3) and (9).

Examples of the insulating ceramic that forms the base of the ceramic heater include silicon nitride ceramics. The structure of the silicon nitride ceramic is such that main phase particles mainly composed of silicon nitride (Si ₃ N ₄ ) are bonded by a grain boundary phase derived from a sintering aid component described later. The main phase may be one in which a part of Si or N is substituted with Al or O, or may be one in which metal atoms such as Li, Ca, Mg, and Y are dissolved in the phase. . For example, sialon represented by the following general formula can be exemplified. The “main component” means a component having the highest mass in the ceramic.
(1) β-sialon: Si _6-Z Al _Z O _Z N _8-Z (z is more than 0 and 4.2 or less)
(2) α-sialon: M _X (Si, Al) ₁₂ (O, N) ₁₆ (x is more than 0 and 2 or less)
Here, M is Li, Mg, Ca, Y, R (R is a rare earth element excluding La and Ce).

  Silicon nitride ceramics include elements of Group 3, Group 4, Group 5, Group 13 (for example Al) and Group 14 (for example Si) in the periodic table based on the IUPAC 1990 recommendation, and Mg. 1 to 15% by mass in terms of oxide can be contained in the content of the entire sintered body. These components are mainly added in the form of oxides, and are contained mainly in the form of complex oxides such as oxides or silicates in the sintered body.

  If the sintering auxiliary component other than silicon nitride (for example, a compound containing a rare earth element, aluminum oxide, etc.) is less than 1% by mass, it becomes difficult to obtain a dense sintered body, and if it exceeds 15% by mass, the strength, toughness or heat resistance is increased. May lead to a lack of. The content of the sintering aid component is desirably 5 to 13% by mass. When a rare earth component is used as a sintering aid component, a compound containing Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu (for example, oxidation) Etc.) can be used. Among these, a compound containing Tb, Dy, Ho, Er, Tm, and Yb can be preferably used because it has an effect of promoting the crystallization of the grain boundary phase and improving the high-temperature strength.

The conductive ceramic forming the resistor of the ceramic heater only needs to contain a conductive ceramic material capable of generating heat, such as a single conductive ceramic material, a mixture of a conductive ceramic material and an insulating ceramic, or the like. It is done. Examples of the conductive ceramic material include tungsten carbide (WC), molybdenum disilicide (MoSi ₂ ), tungsten disilicide (WSi ₂ ), and the like. Examples of the mixture include tungsten carbide (WC), molybdenum disilicide (MoSi ₂ ) or a mixture of tungsten disilicide (WSi ₂ ) and a silicon nitride ceramic as a conductive ceramic material. When the resistor is formed of such a mixture, the difference in linear expansion coefficient from the substrate is reduced, and the thermal shock resistance can be improved.

  The resistor may be formed of one type of conductive ceramic, and the heat generating portion and the pair of lead portions of the resistor may be formed of conductive ceramics having different electrical resistivity. The method for making the electrical resistivity of the conductive ceramics different from each other is not particularly limited. For example, (1) a method for making the contents different in a mixture containing the same kind of conductive ceramic material, and (2) electricity Examples thereof include a method using different types of conductive ceramic materials having different resistivity, and (3) a method of combining (1) and (2).

  In the method (1), for example, the first conductive ceramic forming the heat generating portion may be 10 to 30% by volume of the conductive ceramic material, and the remainder may be an insulating ceramic. If the content of the conductive ceramic material exceeds 30% by volume, the conductivity becomes too high and a sufficient calorific value cannot be expected, and if it is less than 10% by volume, the conductivity becomes too low, and similarly the calorific value. May not be sufficient. The second conductive ceramic forming the pair of lead portions corresponding to the conduction path is preferably 15 to 35% by volume of the conductive ceramic material, and the remainder is an insulating ceramic. If the content of the conductive ceramic material exceeds 35% by volume, densification by firing becomes difficult and the strength tends to be insufficient, and the difference in thermal expansion coefficient from the base becomes large, and cracking during sintering tends to occur. . On the other hand, if it is less than 15% by volume, the heat generation at the pair of lead portions becomes too large, and the heat generation efficiency of the heat generation portion may deteriorate.

  A ceramic heater according to the present invention is prepared by preparing a mixed powder for forming a substrate that becomes an insulating ceramic and a mixed powder for forming a resistor that becomes a conductive ceramic, and forming an unfired resistor with the mixed powder for forming a resistor. An unfired resistor is embedded in the mixed powder for forming, and the resulting molded body is degreased and calcined as desired, and then sintered to form a heating portion that satisfies the above conditions (1) to (3). And manufactured.

  Briefly, an insulating ceramic, a conductive ceramic material, a sintering aid and the like are mixed in a predetermined amount ratio to prepare a mixed powder for forming a substrate and a mixed powder for forming a resistor. These mixed powders can be mixed by an ordinary method such as a wet process. An appropriate amount of a binder or the like is blended and kneaded into each mixed powder thus prepared, and then granulated as desired.

  A resistor is molded by injection molding, screen printing, sheet molding, extrusion molding, etc., using a granulated product of the resistor-forming mixed powder. At this time, it is possible to produce an unfired resistor that becomes a resistor after firing using a mold formed so that the unfired heat-generating portion that becomes the heat-generating portion of the resistor satisfies the above-mentioned conditions, or molding An unfired resistor can also be produced by polishing, tapering, R-surface processing, etc. the heat generating part of the body. Thereafter, the unfired resistor is embedded in a mixed powder for forming a substrate to obtain a molded body. Examples of the method include a method in which an unfired resistor is placed at a predetermined position of a halved mold compacted with a substrate forming mixed powder and then press-molded with the substrate forming mixed powder. Next, when the molded body is degreased and calcined as desired, a molded body in which an unfired resistor serving as a heating resistor is embedded in a powder molded body having the shape of a substrate is obtained. This compact is housed in a firing furnace and fired. Examples of the firing method include a hot press method, a gas pressure firing method, a HIP (hot isostatic press) method, and the like. For example, in the hot press method, it is housed in a pressing die made of graphite or the like, accommodated in a firing furnace, and hot press fired at a predetermined temperature for a required time. The applied pressure can be, for example, about 20 to 30 MPa. The firing temperature and firing time are not particularly limited, but the firing temperature may be 1700 to 1850 ° C., particularly 1700 to 1800 ° C., and the firing time may be 30 to 180 minutes, particularly 60 to 120 minutes. The firing environment can be performed in a non-oxidizing atmosphere such as a nitrogen atmosphere. The method of using such a half mold can be carried out with reference to the method described in, for example, 2007-240080.

  Then, the obtained sintered body is ground to a desired dimension by, for example, a surface grinder or the like, and the tip portion of the sintered body is polished, tapered, so as to satisfy the above condition when used as the tip portion of the substrate. A ceramic heater can be manufactured by R surface processing or the like.

The ceramic heater according to the present invention is not limited to the above-described embodiments, and various modifications can be made within a range in which the object of the present invention can be achieved. For example, in the pair of intermediate portions 40 and 40 in the ceramic heater 1 or the like, the reduction ratio from dCh ₁ to dCh ₂ and the reduction ratio from dCh ₂ to dCh ₃ are respectively constant ratios. May be an irregular ratio, such as ceramic heaters 3 and 6 shown in FIGS. 5B and 5E, and a decreasing ratio from dCh ₁ to dCh ₂ and from dCh ₂ to dCh _3. The reduction ratio may be the same or different.

In the pair of intermediate portions 40 and 40 in the ceramic heater 1 and the like, the reduction ratio from Sch ₁ to Sch ₂ and the reduction ratio from Sch ₂ to Sch ₃ are respectively constant ratios. For example, the ratio may be irregular, such as ceramic heaters 3 and 6, and the reduction ratio from Sch ₁ to Sch ₂ and the reduction ratio from Sch ₂ to Sch ₃ may be the same ratio but at different ratios. There may be.

In the pair of intermediate portions 40 and 40 in the ceramic heater 1 or the like, the decreasing rate from dIh ₁ to dIh ₂ and the decreasing rate from dIh ₂ to dIh ₃ are decreasing at a constant rate, respectively. The rate of decrease from dIh ₁ to dIh ₂ and the rate of decrease from dIh ₂ to dIh ₃ may be the same rate or different rates.

  As long as the pair of intermediate portions 40, 40 satisfy the conditions (1) to (3), the tip side (heat generating tip portion 50) is on the axis C of the base 60, like the ceramic heater 1 or the like. 2, for example, a shape in which the cross-sectional shape shown in FIG. 2 has a certain width toward the tip, that is, the tip side of the pair of intermediate portions (heating tip portion) May be gathered on a straight line perpendicular to the axis C.

In the base end portion 80 of the ceramic heater 1 or the like, the decreasing rate from DCb ₁ to DCb ₂ and the decreasing rate from DCb ₂ to DCb ₃ are respectively constant rates, but these decreasing rates are irregular rates. The reduction ratio from DCb ₁ to DCb ₂ and the reduction ratio from DCb ₂ to DCb ₃ may be the same ratio or different ratios.

In the base end portion 80 of the ceramic heater 1 or the like, the reduction rate from SCb ₁ to SCb ₂ and the reduction rate from SCb ₂ to SCb ₃ are respectively constant rates, but these reduction rates are irregular rates. In addition, the decrease ratio from SCb ₁ to SCb ₂ and the decrease ratio from SCb ₂ to SCb ₃ may be the same ratio or different ratios.

  The same-diameter portion 70 in the ceramic heater 1 or the like is a rod-shaped body or columnar body having a substantially circular or elliptical cross section. However, in this invention, the shape of the same-diameter portion, that is, the outer shape of the ceramic heater is not particularly limited. Examples of the shape include a cylindrical body, an elliptic cylinder, and a rectangular parallelepiped.

  The cross-sectional shape of each of the lead portions in a plane perpendicular to the axis J direction is not particularly limited, and can be various shapes. For example, as shown in FIG. 4, in addition to the fan shape, a circle, a semicircular diameter, an ellipse, a semielliptical shape, a rectangle, and the like can be used.

  The ceramic heater according to the present invention includes a pair of intermediate portions in which the heat generating portion satisfies at least the conditions (1) to (3), and a base end portion in which the base satisfies at least the condition (9). Here, in the conventional ceramic heater, for example, as shown in FIG. 9B, a heat generating tip 53 formed in a relatively long and substantially U-shape is arranged in the vicinity of the outside along the outer shape of the base. Thus, it is considered that the substrate can be uniformly and efficiently heated to be excellent in rapid thermal performance and power consumption can be reduced. Therefore, both of the ceramic heaters of Patent Documents 1 and 2 are heat generating parts (Patent Documents). 1 and the “folded portion 3d” in Patent Document 2) were formed in a substantially U shape so as to be arranged in the vicinity of the outside along the outer shape of the base. However, when the heat generating portion and the base are formed so as to satisfy the conditions (1) to (3) and (9), contrary to expectation, it has better rapid heating and can greatly reduce power consumption. It has been newly found by the present inventor that durability can also be improved. Therefore, the ceramic heater according to the present invention has a pair of intermediate portions satisfying the conditions (1) to (3) and a base end portion satisfying the condition (9). And, the ceramic heater according to the present invention having this feature, for example, the ceramic heaters 1 to 13 have a small volume of the entire heat generating part, and the heat generating part has an excellent rapid heating property, and has a predetermined amount of power consumption. Can reach temperature and exhibits high durability.

  When the ceramic heater according to the present invention satisfies the condition (12), for example, the ceramic heaters 1, 2, 4, 5, 7, 8, 9, and 10 have excellent rapid thermal performance as described above. In addition, the predetermined temperature can be reached with a small amount of power consumption, and at the same time, higher energization durability can be exhibited. Furthermore, when the ceramic heater according to the present invention satisfies the condition (13), for example, the ceramic heaters 1, 2, 5, 7, 8, and 10 can further improve the rapid thermal performance and consume power as described above. Can be further reduced and high current-carrying durability can be achieved.

  Further, in the ceramic heater according to the present invention, the reduction rate ΔdCh of the virtual circumscribed circle CCh at the pair of intermediate portions cut at any two planes orthogonal to the axis C of the base is the virtual inscribed circle Ich. The decrease rate ΔdIh of the diameter dIh may be larger. If a pair of intermediate part is provided with this structure, the resistance body thickness in a pair of intermediate part can be made thin toward a front-end | tip to such an extent that high durability can be maintained. For this reason, the volume of the heat generating portion, particularly the heat generating tip portion is greatly reduced, and it is possible to realize a ceramic heater that is more excellent in quick heat while maintaining high durability, and can significantly reduce power consumption.

  Since the ceramic heater according to the present invention has the above-described effects, it is preferably used as a glow plug heater, a sensor heater, a fan heater heater, or the like. A glow plug according to an embodiment of the present invention using the ceramic heater according to the present invention as a glow plug heater will be described. As shown in FIG. 8, the glow plug 20 includes the ceramic heater 1. More specifically, the glow plug 20 includes the ceramic heater 1, the outer cylinder 90, the metal shell 93, and the middle shaft 94. In the glow plug 20, the outer peripheral surface of the ceramic heater 1 is surrounded in the circumferential direction by an outer cylinder 90 so that at least the base end portion 80 of the base body 60 protrudes, and the outer cylinder 90 is a front end portion of a substantially cylindrical metal shell 93. It is fixed to and consists of. The metal shell 93 and the outer cylinder 90 are, for example, brazed or press-fitted so as to fill a gap between the inner and outer peripheral surfaces of the metal shell 93 or the inner edge of the front end side opening of the metal shell 93 and the outer peripheral surface of the outer cylinder 90. It is fixed by laser welding all around.

  The metal shell 93 has a male threaded portion 98 formed on the central peripheral side surface so that the glow plug 20 can be attached to a cylinder head (not shown) of the engine. A hexagonal hook-shaped tool engaging portion 99 is formed on the side of the metal shell 93 that is not joined to the outer cylinder 90, and is used when the glow plug 20 is screwed into the cylinder head. The tool can be engaged.

  Inside the metal shell 93, a metal center shaft 94 for supplying electric power to the ceramic heater 1 from its rear end side is insulated from the metal shell 93 by a cylindrical insulating member 95 and an insulating locking member 96. The arrangement is fixed so that The insulating locking member 96 has a flange with one end of the cylinder projecting outward, and a caulking member 97 attached to the vicinity of the metal fitting of the center shaft 94 and the tool engaging portion 99 are locked by the flange. Yes. The caulking member 97 is pressed from the outer periphery and caulked. As a result, the insulating locking member 96 whose flange is locked between the middle shaft 94 and the metal shell 93 is fixed, so that it is prevented from being pulled out from the middle shaft 94.

  On the other hand, the resistor 30 of the ceramic heater 1 has one lead portion 31 electrically connected to the outer cylinder 90 at an electrode extraction portion 78 formed on the outer peripheral surface thereof, and the other lead portion 31 is connected to the outer peripheral surface thereof. The electrode take-out portion 77 formed on the electrode is electrically connected to the center shaft 94 via the electrode cylinder 91 and the conducting wire 92. The highest heat generating portion 21 in the glow plug 20 is a portion capable of generating heat up to a temperature functioning as a glow plug, and usually the outer periphery of the base end portion 80 in which the highest heat generating portion 55 of the resistor 30 is embedded. It corresponds to a surface.

  The glow plug 20 is manufactured as follows. That is, after press-fitting the outer cylinder 90 and the electrode cylinder 91 so that at least the base end portion 80 of the base 60 protrudes into the ceramic heater 1, a Ni wire is welded to the electrode cylinder 91 and the middle shaft 94, These are electrically connected. Next, these are press-fitted into the tip of the metal shell 93 and welded, and the center shaft 94 is fixed to the metal shell 93 with the insulating member 95, the insulating locking member 96, and the caulking member 97, whereby a glow plug can be manufactured.

  Since the glow plug according to the present invention includes the ceramic heater according to the present invention, it exhibits a high level of rapid thermal performance, low power consumption and durability. In particular, when the glow plug according to the present invention further includes a ceramic heater that satisfies at least one of the conditions (12) and (13), a higher level of rapid thermal performance, low power consumption, and durability. Can be demonstrated.

  The glow plug according to the present invention is not limited to the above-described embodiment, and various modifications can be made within a range in which the object of the present invention can be achieved.

(Production of ceramic heater)
WC having an average particle size of 0.7 μm, silicon nitride having an average particle size of 1.0 μm, and Er ₂ O ₃ as a sintering aid were wet mixed in a ball mill for 40 hours to obtain a mixed powder for forming a resistor (this The content of WC in the mixed powder was adjusted between 27% by volume (63% by mass) and 32% by volume (70% by mass) so that the room temperature resistance of the ceramic heater after firing was about 400 mΩ. The resistor-forming mixed powder was dried by a spray drying method to produce a granulated powder, and then a binder was added so as to have a ratio of 40 to 60% by volume and mixed in a kneading kneader for 10 hours. Thereafter, the obtained mixture was granulated with a pelletizer to a size of about 3 mm. The granulated product is put into an injection molding machine equipped with a mold capable of forming an intermediate part of Examples 1 to 6 and Comparative Example 1, and is then subjected to injection molding. An unfired resistor having the following was obtained.

On the other hand, silicon nitride having an average particle size of 0.6 μm, Er ₂ O ₃ as a sintering aid, and CrSi ₂ , WSi ₂ and SiC as thermal expansion modifiers were wet mixed in a ball mill, and a binder was added. Thereafter, it was dried by a spray drying method to obtain a mixed powder for forming a substrate for forming a substrate.

  Next, the unfired resistor was embedded in the mixed powder for forming the substrate and press-molded to obtain a molded body to be a ceramic heater. This molded body was degreased and calcined for 1 hour in a nitrogen atmosphere at 800 ° C., and then sintered by hot pressing in a nitrogen atmosphere of 0.1 MPa at 1780 ° C. and a pressure of 30 MPa for 90 minutes. A sintered body was obtained. The obtained sintered body was polished into a substantially cylindrical shape with a diameter of 3.3 mm, and the tip portion 80 of the substrate was tapered, polished, or R-polished as desired to produce each ceramic heater.

The ceramic heater of Example 1 (total length 42 mm) had the same shape as the ceramic heater 1 shown in FIGS. 1 to 4 and had the following dimensions.
・ The length Lh of the heat generating part 33 in the direction of the axis C is 7 mm.
The length of the intermediate portion 40 in the direction of the axis C is 7 mm, the diameter difference dCh _a -dCh _b is 1.7 mm, and the diameter difference dIh _a -dIh _b is 0.4 mm.
-The cross-sectional area of the highest heat generating part 55 in the resistor 30 is 0.40 mm ²
The cross-sectional area ratio of the highest heat generating portion 55 to the lead portion 31 is 1 / 9.3.
The position of the heat generating tip 50 is 0.5 mm from the outer surface of the base tip 80
・ The distance between the pair of lead portions 31, 31 is 0.6 mm.
The length of the base end 80 in the direction of the axis C is 7 mm, the diameter difference DCb _a -DCb _b is 1.8 mm, and the wall thickness is 0.5 mm.
-Angle θa is 11 °, angle θb is 11 °, angle θc is 8 °

The ceramic heater of Example 2 has the same shape as the ceramic heater 7,
The diameter difference dCh _a -dCh _b in the intermediate part 40 is 1.9 mm, the diameter difference dIh _a -dIh _b is 0.3 mm,
The cross-sectional area of the maximum heat generating portion 55 in the resistor 30 is 0.06 mm ^2;
The cross-sectional area ratio of the highest heat generating portion 55 to the lead portion 31 is 1/59,
The position of the heat generating tip 50 is 0.3 mm from the outer surface of the base tip 80,
The diameter difference DCb _a -DCb _b at the base end 80 is 2.5 mm and the wall thickness is 0.3 mm.
-It had the same dimensions as the ceramic heater 1 of Example 1 except that the angle θa was 12 °, the angle θb was 11 °, and the angle θc was 1 °.

The ceramic heater of Example 3 has the same shape as the ceramic heater 2 shown in FIG.
The diameter difference dCh _a −dCh _b in the intermediate part 41 is 1.3 mm, the diameter difference dIh _a −dIh _b is 0 mm,
-The distance between the pair of lead portions 31, 31 is 0.4 mm,
The diameter difference DCb _a −DCb _b at the base end portion 80 is 1.2 mm,
-It had the same dimensions as the ceramic heater 1 of Example 1 except that the angle θa was 6 °, the angle θb was 6 °, and the angle θc was 0 °.

The ceramic heater of Example 4 has the same shape as the ceramic heater 10 shown in FIG.
- said diameter difference _{dCh a -dCh b} is 1.6mm in the intermediate portion 40, the diameter difference _dIh b _{-dIh a} is 0.2 mm,
The diameter difference DCb _a −DCb _b at the base end portion 86 is 1.8 mm,
-It had the same dimensions as the ceramic heater 2 of Example 3 except that the angle θa was 11 °, the angle θb was 7.5 °, and the angle θc was 1 °.

The ceramic heater of Example 5 has the same shape as the ceramic heater 8 shown in FIG.
The diameter difference DCb _a -DCb _b at the base end portion 87 is 1.6 mm,
-It had the same dimensions as the ceramic heater 10 of Example 4 except that the angle θa was 7.5 °, the angle θb was 7.5 °, and the angle θc was 1 °.

The ceramic heater of Example 6 has the same shape as the ceramic heater 9 shown in FIG.
The diameter difference DCb _a −DCb _b at the base end portion 85 is 0.6 mm,
-It had the same dimensions as the ceramic heater 10 of Example 4 except that the angle θa was 3.5 °, the angle θb was 7.5 °, and the angle θc was 1 °.

The ceramic heater (total length 42 mm) of Comparative Example 1 has the same shape as the ceramic heater 14 shown in FIG.
- said diameter difference at the intermediate portion 44 dCh _a -dCh _b is 0.7 mm, the diameter diH is increased toward the tip of a virtual inscribed circle Ich (the diameter difference _dIh b _{-dIh a} is 0.6 mm) and,
- except that the diameter difference _DCh a -DCh _b at the base tip 85 is 0.7mm had the same dimensions as the ceramic heater 8 of Example 5.

The ceramic heater (total length 42 mm) of Comparative Example 2 had the same shape as the ceramic heater 15 shown in FIG. 9B, and had the following dimensions.
-Length Lh in the axis C direction of the heat generating part 54 is 7 mm.
The length of the intermediate portion 49 in the direction of the axis C is 7 mm, the diameter difference dCh _a -dCh _b is 0 mm, the diameter difference dIh _b -dIh _a is 1.0 mm (the diameter dIh of the virtual inscribed circle ICh is toward the tip) Increase)
The cross-sectional area of the maximum heat generating portion 55 at the heat generating front end portion 53 is 1.1 mm ²
The cross-sectional area ratio of the highest heat generating portion 55 to the lead portion 31 is 1 / 2.8.
・ The position of the heat generating tip 53 is 1 mm from the outer surface of the tip of the base.
-The distance between the pair of lead portions 31, 31 is 0.4 mm.
The base is formed with the same diameter portion 73, and the tip portion is formed in a hemispherical shape.

(Manufacture of glow plugs)
After the outer cylinder 90 and the electrode cylinder 91 are press-fitted into the ceramic heaters thus produced so that at least the tip of the base protrudes, Ni wire is applied to the electrode cylinder 91 and the middle shaft 94. They were welded and connected electrically. These were press-fitted into the tip of the metal shell 93 and welded. Next, the glow plugs of Examples 1 to 6 and Comparative Example 1 were manufactured by fixing the center shaft 94 to the metal shell 93 with the insulating member 95, the insulating locking member 96, and the caulking member 97.

(Measurement of glow plug saturation temperature, power consumption and 1000 ° C arrival time)
The apparatus shown in FIG. 10 was used to measure the saturation temperature, power consumption, and 1000 ° C. arrival time of these glow plugs. 10 includes a controller 100, a DC power source 101 connected to the controller 100, an oscilloscope 105 connected to the DC power source 101, a radiation thermometer 104 and a personal computer 106 connected to the oscilloscope 105, And a conducting wire extending from the DC power supply 101. Details of the apparatus are shown in FIG.

  Using the glow plugs of Examples 1 to 6, Comparative Examples 1 and 2 and the apparatus shown in FIG. 10, the saturation temperature and power consumption were measured by the following method. That is, each glow plug was connected to the conducting wire of this apparatus, the applied voltage was set by the controller 100 to control the DC power supply 101, and the voltage applied to the glow plug 20 was controlled. The maximum surface temperature of the glow plug ceramic heater was measured with a radiation thermometer 104 including the camera 102 and the main body 103, and the measured maximum surface temperature was set as the saturation temperature (emissivity 0.935).

Further, the oscilloscope 105 monitored the applied voltage and current applied from the DC power source 101, and the radiation thermometer 104 monitored the measurement temperature measured as the surface temperature of the ceramic heater. The oscilloscope 105 can record the measured temperature, applied voltage, and current data in synchronization using the applied voltage as a trigger. The data obtained in this way was edited by, for example, the personal computer 106, and the power consumption when the saturation temperature was 1200 ° C. was calculated. Measure the temperature of the highest heat generating part on the outer peripheral surface of the ceramic heater when a DC voltage with a saturation temperature of 1200 ° C. is applied to the glow plug, measure the 1000 ° C. arrival time, evaluated. The results are shown in Table 1.
FIG. 12 is a graph showing changes in the temperature of the highest heat generating portion 21 on the outer peripheral surface of the ceramic heater with respect to the elapsed time for the glow plugs of Examples 1 and 2 and Comparative Examples 1 and 2.

(Glow plug energization durability test)
Using the glow plugs of Examples 1 to 6 and Comparative Examples 1 and 2, an energization durability test was performed. The test temperature of the current-carrying durability test was adjusted to 1350 ° C., which is the limit temperature of heat resistance, by adjusting the applied voltage. Energization of the glow plug was repeated by energizing for 1 minute and stopping energization for 30 seconds (forcibly cooled with compressed air during this period) as one cycle. The upper limit of the number of energization cycles was 100,000 cycles, and when the room temperature resistance value changed by 10% or more, the test was terminated at that time. The room temperature resistance value of the glow plug is an electrical resistance value between two electrode extraction portions exposed on the outer peripheral surface of the ceramic heater substrate at 20 ° C., and was measured according to a conventional method. The results are shown in Table 1.

As is clear from the results shown in Table 1, in Examples 1 to 6, the resistor includes a heat generating portion having a pair of intermediate portions that satisfy the conditions (1) to (3) and (9). Glow plugs have excellent heat resistance, can reduce power consumption, and have excellent durability.
Usually, in order to increase the rapid heat property, it is necessary to use two kinds of conductive materials or to lower the room temperature resistance value to 300 mΩ or less, but the glow plugs of Examples 1 to 6 use one kind of conductive material, Even when the room temperature resistance value was about 400 mΩ and greatly exceeded 300 mΩ, when a low DC voltage saturated to 1200 ° C. was applied, it reached 1000 ° C. within 3.5 seconds. Since rapid thermal performance was obtained without lowering the room temperature resistance value to 300 mΩ or less, in addition to being able to suppress inrush current at start-up, rapid thermal performance was obtained without applying a particularly high voltage. Even without a controller, it was confirmed that a sufficiently rapid heat resistance could be obtained. Of course, this result does not preclude the use of the controller.
Especially Examples 1-5 which satisfy | fill all the said conditions (1)-(3), (9), (12) and (13) have more excellent quick heat property, and reduce power consumption still more. Can be made and also has excellent durability.
On the other hand, Comparative Examples 1 and 2 that do not satisfy both of the conditions (1) to (3) and (9) require power consumption of 47 W and 62 W, respectively, and the results of the rapid thermal test are also examples. It was not superior. In Comparative Example 1, the power consumption was slightly lower than that in Comparative Example 2 and the rapid thermal performance was increased, but sufficient power consumption and excellent rapid thermal performance were not obtained.

FIG. 1 is a schematic perspective view showing a ceramic heater of one embodiment of the ceramic heater according to the present invention. FIG. 2 is a schematic cross-sectional view showing a ceramic heater according to an embodiment of the ceramic heater according to the present invention, taken along a plane including an axis C and an axis J. FIG. 3 is an enlarged cross-sectional view showing a ceramic heater of one embodiment of the ceramic heater according to the present invention. FIG. 3A shows an axis C and an axis J of the ceramic heater of one embodiment of the ceramic heater according to the present invention. 3B is an enlarged cross-sectional view of the ceramic heater according to an embodiment of the present invention cut along a plane perpendicular to the plane including the axis C and the axis J. FIG. FIG. 3C is a sectional view showing a section CP when the ceramic heater of one embodiment of the ceramic heater according to the present invention is cut along an arbitrary plane P perpendicular to the axis C. FIG. 3D shows an angle formed between the axis C and the outline of the tip of the substrate when the ceramic heater according to one embodiment of the present invention is cut along a plane including the axis C and the axis J. a, it is a schematic diagram showing the angle θc between the angle .theta.b, inner contour line of the axis C and an intermediate portion of the outer contour line of the axis C and the intermediate portion. FIG. 4 is a cross-sectional view showing a cross-section CP when the ceramic heater of one embodiment of the ceramic heater according to the present invention is cut along a plane P, and FIG. 4A is one embodiment of the ceramic heater according to the present invention. of a cross-sectional view showing a cross section CP ₁ when cut at a plane P ₁ of the ceramic heater, FIG. 4 (b) of a cutaway of the ceramic heater of one embodiment of a ceramic heater according to the present invention in a plan P ₂ is a cross-sectional view showing a cross section CP _2, FIG. 4 (c) is a sectional view showing a section CP ₃ obtained by cutting the ceramic heater of one embodiment of a ceramic heater according to the present invention in a plan P _3. FIG. 5 is an enlarged sectional view showing a ceramic heater according to another embodiment of the ceramic heater according to the present invention, and FIG. 5A shows an axis of the ceramic heater according to another embodiment of the ceramic heater according to the present invention. FIG. 5B is an enlarged cross-sectional view when cut along a plane including C and the axis J, and FIG. 5B is a plane including the axis C and the axis J in another embodiment of the ceramic heater according to the present invention. FIG. 5C is an enlarged cross-sectional view when the ceramic heater according to another embodiment of the ceramic heater according to the present invention is cut along a plane including the axis C and the axis J. FIG. 5 (d) shows an enlarged section when the ceramic heater of another embodiment of the ceramic heater according to the present invention is cut along a plane including the axis C and the axis J. A diagram, FIG. 5 (e) is an enlarged sectional view of a cutaway of the ceramic heater of yet another embodiment of the ceramic heater according to the present invention a plane including the axis C and the axis J. FIG. 6 is an enlarged cross-sectional view showing a ceramic heater according to another embodiment of the ceramic heater according to the present invention. FIG. 6A shows an axis of the ceramic heater according to another embodiment of the ceramic heater according to the present invention. FIG. 6B is an enlarged cross-sectional view when cut along a plane including C and the axis J, and FIG. 6B is a plane including the axis C and the axis J in another embodiment of the ceramic heater according to the present invention. FIG. 6C is an enlarged cross-sectional view when the ceramic heater of still another embodiment of the ceramic heater according to the present invention is cut along a plane including the axis C and the axis J. FIG. 6D is an enlarged view of a ceramic heater according to another embodiment of the present invention cut by a plane including the axis C and the axis J. It is a cross-sectional view. FIG. 7 is an enlarged sectional view showing a ceramic heater according to another embodiment of the ceramic heater according to the present invention, and FIG. 7A shows an axis of the ceramic heater according to another embodiment of the ceramic heater according to the present invention. FIG. 7B is an enlarged cross-sectional view when cut along a plane including C and the axis J, and FIG. 7B is a plane including the axis C and the axis J in another embodiment of the ceramic heater according to the present invention. FIG. 7C is an enlarged cross-sectional view when cut, and FIG. 7C is an enlarged cross-sectional view when a ceramic heater of still another embodiment of the ceramic heater according to the present invention is cut along a plane including the axis C and the axis J. It is. FIG. 8 is a schematic sectional view showing a glow plug of one embodiment of the glow plug according to the present invention. FIG. 9 is an enlarged sectional view of a conventional ceramic heater cut along a plane including the axis C and the axis J. FIG. 9A shows an example of the conventional ceramic heater. FIG. 9B is an enlarged cross-sectional view when a ceramic heater showing another example of a conventional ceramic heater is cut along a plane including the axis C and the axis J. FIG. is there. FIG. 10 is an explanatory diagram for explaining the outline of the apparatus used for measuring the saturation temperature and power consumption of the glow plug. FIG. 11 is an explanatory diagram for explaining details of the apparatus used for measuring the saturation temperature and power consumption of the glow plug. FIG. 12 is a graph showing the relationship between the temperature of the highest heat generating portion on the outer peripheral surface of the ceramic heater and time.

Explanation of symbols

1-14 Ceramic heater 20 Glow plug 21, 55 Maximum heat generating portion 30 Resistor 31 Lead portion 31b Connection portion 31c Lead wires 32-39, 54 Heat generating portion 40-49 Intermediate portion 50-53 Heat generating tip portion 57 Cross section 59 Vertical space Part 60 Base 70 to 73 Same diameter part 75 Rear end face 77, 78 Electrode extraction part 80 to 86 Base tip 87 Base cross section 90 Outer cylinder 91 Electrode cylinder 92 Conductor 93 Main metal fitting 94 Central shaft 95 Insulating member 96 Insulating locking member 97 Caulking member 98 Male thread portion 99 Tool engaging portion 100 Controller 101 DC power source 102 Camera 103 Main body 104 Radiation thermometer 105 Oscilloscope 106 Personal computer C, J Axis P, P ₁ , P ₂ , P ₃ plane CP, CP ₁ , CP _2, CP ₃ cross _{CCh, CCh 1, CCh 2,} CCh 3 virtual circumscribing circle dCh _{dCh 1, dCh 2, dCh 3} , dCh a, dCh b virtual circumscribing circle having a diameter _{SCh, SCh 1, SCh 2,} SCh 3 cross-sectional area of the virtual circumscribing circle _{ICh, ICh 1, ICh 2,} ICh 3 virtual inscribed circle dIh , DIh ₁ , dIh ₂ , dIh ₃ , dIh _a , dIh _b Diameter of virtual inscribed circle SIh, SIh ₁ , SIh ₂ , SIh ₃ Cross sectional area of virtual inscribed circle CCb, CCb ₁ , CCb ₂ , CCb ₃ virtual circumscribed Circle DCb, DCb ₁ , DCb ₂ , DCb ₃ , DCb _a , DCb _b Virtual circumscribed circle diameter

Claims (3)

A resistor formed of conductive ceramic is embedded in a base formed of insulating ceramic, and the resistor includes a pair of lead portions extending in the axial direction of the base and a pair of lead portions. A ceramic heater having one heat generating part that extends in the axial direction from the tip part and is formed by connecting the tip parts to each other,
The heat generating portion has a pair of intermediate portions, the pair of intermediate portions satisfy the following conditions (1) to (3), the base has a base tip, and the base tip has the following conditions ( The ceramic heater characterized by satisfying 9).
(1) The diameter of a virtual circumscribed circle that is in contact with each contour line forming each of the pair of cross-sections cut by a plane orthogonal to the axis and includes the pair of cross-sections at the tip of the heat generating portion (2) The total cross-sectional area of the pair of cross-sections decreases toward the tip of the heat generating part. (3) A virtual inscribed contact with each of the contour lines and sandwiched between the pair of cross-sections. The diameter of the circle is constant or decreases toward the tip of the heat generating part. (9) The diameter of the circle is in contact with the contour line forming the base cross section cut by the plane and the base cross section is The diameter of the virtual circumscribed circle contained inside decreases toward the tip of the substrate. 2. The ceramic heater according to claim 1, wherein the front end portion of the base body and the pair of intermediate portions satisfy the following conditions (12) and (13).
(12) When cut along a plane including the axis of the base and the axis of each of the pair of intermediate portions, the contour of the tip of the base, the outer contour of each of the pair of intermediate portions, and the pair of The inner contour line of each intermediate part is linear, the distance between the contour lines of the base end part, the distance between the outer contour lines of each of the pair of intermediate parts, and the inner side of each of the pair of intermediate parts The distance between the contour lines decreases toward the tip of the heat generating portion. (13) When the substrate is cut along a plane including the axis of the base and the axes of the pair of intermediate portions, the axis of the base and the base An angle between the contour line of the tip and θa, an angle between the axis of the base body and the outer contour line of the pair of intermediate portions, θb, an axis line of the base body and an inner contour line of the pair of intermediate portions, Θa ≧ θb, where θc is the angle formed by To meet the θc   A glow plug comprising the ceramic heater according to claim 1.

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