JP2016122489A - Ceramic heater and sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for suppressing occurrence of breakage or cracking in the heater body where a lead and a pad are formed.SOLUTION: In a ceramic heater including a heater body 102 formed of insulating ceramic, a heat element 141 embedded in the heater body 102, and an electrode pad 121 arranged on the outer surface of the heater body 102, and connected electrically with the heat element 141, the heat element 141 has a rear end side lead 143c arranged in the projection domain S of the electrode pad 121, and narrower than the width D of the electrode pad 121 over the whole area of the projection domain S, a tip side lead 143a arranged closer to the tip side than the rear end side lead 143c, and wider than the width C of the rear end side lead 143c, and a heating part 142 arranged closer to the tip side than the tip side lead 143a, and narrower than the width B of the tip side lead 143a.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a ceramic heater having a heating resistor and an electrode pad, and a sensor including the ceramic heater.

  Conventionally, a heater body formed of an insulating ceramic such as alumina, a heating resistor embedded in the heater body, and an outer surface of the heater body are electrically connected to the heating resistor. There has been known a ceramic heater having an electrode pad and a conductor portion connecting the heating resistor and the electrode pad.

  In this ceramic heater, a connection terminal connected to an external device via a lead wire is connected to the electrode pad by a brazing material or the like, and it is possible to energize the heating resistor via the external device. . (Patent Document 1).

JP 2014-13649 A

  By the way, as shown in Patent Document 1, the heating resistor has a heat generating portion on the front end side and a pair of lead portions on the rear end side, and the width of the heat generating portion on the front end side is equal to that of the lead portion. It is narrower than the width. This is because the specific resistance of the heat generating part is increased because heat generation is concentrated by the heat generating part. That is, when the heating resistor is energized, since the specific resistance of the heat generating portion is higher than that of the lead portion, heat generation can be more concentrated in the heat generating portion, and the ceramic heater can be used efficiently.

  On the other hand, as shown in Patent Document 1, the width of the lead portion is substantially uniform along the axial direction of the ceramic heater while being wider than the width of the heat generating portion. Therefore, in the region where the lead portion and the electrode pad face each other, the width of the lead portion may be larger than the width of the electrode pad. In such a case, due to the following events, the heater main body may be cut or cracked in the vicinity of the edge in the width direction of the electrode pad.

  In a round bar-shaped ceramic heater, electrode pads 1210 and heating resistors 1410 are usually printed on the upper and lower surfaces of a plate-shaped ceramic layer 1400 as shown in FIG. 8, and then the ceramic layer 1400 is formed into a cylindrical shape. Alternatively, it is formed by winding it around a cylindrical soot tube (not shown). FIG. 8 shows a cross-sectional view of the ceramic layer 1400 cut along the width direction.

  At this time, when a paste-like metal conductor is printed on the lower surface of the plate-like ceramic layer 1400 to form a heat generating resistor 1410 having a desired shape, the heat generating resistor 1410 is then dried, whereby the heat generating resistor 1410 is dried. Will shrink. That is, the heating resistor 1410 contracts inward in the width direction of the ceramic layer 1400 as shown in FIG. 8 (see arrow W1). Then, due to the shrinkage of the heating resistor 1410, stress is applied to the upper surface side of the ceramic layer 1400 on the outer side in the width direction (see arrow Y1).

  After that, when a paste-like metal conductor is printed on the upper surface of the ceramic layer 1400 and the electrode pad 1210 is formed, the electrode pad 1210 is dried like the heating resistor 1410 so that the electrode pad 1210 is placed inward in the width direction. Shrink (see arrow Z1). As a result, the direction of the stress (arrow Y1) on the upper surface of the ceramic layer 1400 due to the influence of the heating resistor 1410 and the direction of the stress (arrow Z1) when the electrode pad 1210 contracts are separated in the opposite direction. It becomes.

  In such a situation, when the ceramic layer 1400 is further wound around the soot tube, the stress on the upper surface side of the ceramic layer 1400 is further increased. As a result, in the formed heater main body, the end of the electrode pad in the width direction is increased. There was a risk of cutting or cracking in the vicinity of the edge.

  The present invention has been made to solve the above-described conventional problems, and an object of the present invention is to suppress the occurrence of cuts and cracks in a heater main body portion where lead portions and electrode pads are formed.

The present invention relates to a round bar-shaped ceramic heater extending in the axial direction, a heater main body formed of insulating ceramic, a heating resistor embedded in the heater main body, and an outer surface of the heater main body. An electrode pad electrically connected to the heating resistor, and a conductor portion connecting the heating resistor and the electrode pad, and a ceramic heater comprising:
The heating resistor is disposed in a projection region in which the electrode pad is projected in a direction perpendicular to the axial direction, and a rear end side lead portion that is narrower than the width of the electrode pad over the entire projection region. And a distal end side lead portion wider than a width of the rear end side lead portion and a distal end side than the distal end side lead portion, And a heat generating portion narrower than the width of the lead portion.

  According to the ceramic heater of the present invention, the heating resistor is disposed in a projection area obtained by projecting the electrode pad in a direction perpendicular to the axial direction, and is narrower than the width of the electrode pad over the entire projection area. And a rear end side lead portion. As a result, even if the stress applied to the heater body due to the contraction of the rear end side lead part and the stress of the electrode pad contraction occur, the directions of the stresses cancel each other, and the heater body It can suppress that a cutting | disconnection, a crack, etc. arise in the edge part vicinity of the width direction of an electrode pad among parts.

  Furthermore, according to the ceramic heater of the present invention, the leading end side lead portion disposed on the leading end side with respect to the trailing end side lead portion and wider than the width of the trailing end side lead portion, and the leading end side with respect to the leading end side lead portion. And a heat generating portion that is narrower than the width of the leading end side lead portion. In this way, by forming the leading end side lead portion wider than the heating portion and the rear end side lead portion, it is possible to concentrate heat generation on the heating portion, and the ceramic heater can be used efficiently.

  In the ceramic heater of the present invention, it is preferable that a width of the heat generating portion is narrower than a width of the rear end side lead portion. In this way, the width of the heat generating part is narrower than the width of the rear end side lead part, so that heat generation can be surely concentrated on the heat generating part without generating heat at the rear end side lead part. A ceramic heater can be used well.

  Further, in the ceramic heater of the present invention, the heating resistor has a connection lead portion that connects the front end side lead portion and the rear end side lead portion and decreases in width toward the rear end side in the axial direction. It is preferable. Thus, by having the connection lead portion whose width decreases toward the rear end side in the axial direction, the corner portion where the electric field tends to concentrate is not formed on the front end side lead portion and the rear end side lead portion. Can be suppressed.

  Furthermore, the ceramic heater according to the present invention is characterized in that the connection lead portion is disposed on the tip side of the projection region. This makes it possible to make the width of the lead part narrower than the width of the electrode pad within the projection area, and cut or crack near the edge of the heater body in the width direction of the electrode pad. Etc. can be further suppressed.

Further, the sensor of the present invention is a sensor comprising a bottomed cylindrical sensor element, a metal shell for holding the sensor element, and a ceramic heater disposed in the cylindrical hole of the sensor element,
The ceramic heater is the ceramic heater according to any one of claims 1 to 4.

  As described above, the ceramic heater of the present invention is used for a sensor including a bottomed cylindrical sensor element, a metal shell for holding the sensor element, and a ceramic heater disposed in the cylindrical hole of the sensor element. Thus, it is possible to further suppress the occurrence of cutting or cracking in the vicinity of the edge in the width direction of the electrode pad in the heater main body.

It is sectional drawing explaining the whole structure of the sensor 1 of Embodiment 1. FIG. 1 is a perspective view illustrating an appearance of a ceramic heater 100 according to Embodiment 1. FIG. 1 is an exploded perspective view illustrating an internal configuration of a ceramic heater 100 according to a first embodiment. FIG. 3 is a partial cross-sectional view of a vicinity of a joint portion taken along a one-dot chain line AA ′ in the ceramic heater 100 of FIG. It is explanatory drawing which visually recognized the electrode pad 121 of the ceramic heater 100 of Embodiment 1 in the direction perpendicular | vertical to an axial direction. It is explanatory drawing explaining the effect of the invention of the ceramic heater 100 of Embodiment 1. FIG. It is explanatory drawing which visually recognized the electrode pad of the ceramic heater of Embodiment 2 in the direction perpendicular | vertical to an axial direction. It is explanatory drawing explaining the conventional ceramic heater.

Hereinafter, Embodiment 1 to which the present invention is applied will be described with reference to the drawings.
In addition, this invention is not limited to the following embodiment at all, and it cannot be overemphasized that various forms may be taken as long as it belongs to the technical scope of this invention.

  FIG. 1 is a cross-sectional view illustrating the overall configuration of the sensor 1 according to the first embodiment. A sensor 1 according to Embodiment 1 is a sensor that is fastened to an exhaust passage of an internal combustion engine mounted on a vehicle such as a passenger car, and that has a tip portion disposed inside the exhaust passage. The oxygen concentration in the exhaust gas It is an oxygen sensor that measures

  In the following description, in the direction along the axis O shown in FIG. 1, the side on which the protector 80 is attached to the metal shell 60 (the lower side in the figure) is the tip side, and the opposite side (the upper side in the figure). Is described as the rear end side.

  As shown in FIG. 1, the sensor 1 includes a sensor element 10 (detection element 10), a ceramic heater 100, a separator 30, a seal member 40 (elastic member 40), a plurality of connection terminals 50, and lead wires. 55 (lead member 55), a metal shell 60 covering the periphery thereof, a protector 80, an outer cylinder 90 (outer cylinder member 90) and the like are mainly provided.

  The sensor element 10 is formed from a solid electrolyte having oxygen ion conductivity. The sensor element 10 has a known configuration, is formed in a cylindrical shape extending in the direction of the axis O, and has an element body 12 having a closed end portion (lower end portion in FIG. 7), and an element body 12. An outer electrode (not shown) provided on the outer peripheral surface and an inner electrode (not shown) provided on the inner peripheral surface of the element body 12 are mainly provided. On the outer periphery of the central portion of the element body 12, a flange portion 14 that protrudes radially outward is provided in the circumferential direction.

A typical example of the solid electrolyte constituting the element body 11 is ZrO _{2 in} which Y ₂ O ₃ or CaO is dissolved. In addition to this solid electrolyte, a solid electrolyte which is a solid solution of an alkaline earth metal or rare earth metal oxide and ZrO ₂ may be used. Further, a solid electrolyte containing HfO _{2 in} a solid solution of an alkaline earth metal or rare earth metal oxide and ZrO ₂ may be used.

  The outer electrode or the inner electrode is an electrode in which Pt or a Pt alloy (hereinafter referred to as “Pt or the like”) is formed porous.

  A plurality of connection terminals 50 are in contact with the outer electrode or the inner electrode. The plurality of connection terminals 50 include an inner connection terminal 51 and an outer connection terminal 52. The plurality of connection terminals 50 are metal fittings formed from a nickel alloy (for example, Inconel 750, manufactured by Inconel, UK, registered trademark).

  The inner connection terminal 51 is in electrical contact with the inner electrode of the sensor element 10, and the outer connection terminal 52 is electrically connected to the outer electrode of the sensor element 10. The inner connection terminal 51 holds the ceramic heater 100 described later, and presses the tip side of the ceramic heater 100 against the inner surface of the sensor element 10.

  The core wires of the lead wires 55 are caulked and connected to the plurality of terminal fittings 50, respectively. In FIG. 1, three of the four lead wires 55 are illustrated.

  As shown in FIG. 1, the separator 30 is a member disposed on the rear end side of the sensor element 10 and is a cylindrical member formed of an electrically insulating material, for example, alumina. The separator 30 is provided with an accommodating portion 31 for accommodating a plurality of terminal fittings 50 and the like. The accommodating portion 31 is a through hole formed so as to penetrate the separator 30 in the direction of the axis O, and allows air to flow between the space on the front end side and the space on the rear end side with respect to the separator 30. It is.

  Furthermore, a flange portion 32 that protrudes radially outward is provided on the outer peripheral surface of the separator 30. A holding metal fitting 33 formed in a substantially cylindrical shape is disposed on the outer peripheral surface of the separator 30 on the tip side of the flange portion 32. At this time, the separator 30 is disposed so as to be inserted into the holding metal fitting 33.

  The seal member 40 is a plug member that is disposed on the rear end side of the separator 30 and is made of an elastic material such as fluorine rubber. The seal member 40 is a member that closes the rear end of the outer cylinder 90 that is formed in a substantially cylindrical shape. The seal member 40 is fitted into the opening on the rear end side of the outer cylinder 90 so as to contact the surface on the rear end side of the separator 30.

  As shown in FIG. 1, the metal shell 60 is a member formed of a stainless alloy (for example, SUS310S of JIS standard), and is a member formed in a substantially cylindrical shape. The metal shell 60 is provided with a step portion 61 that supports the flange portion 14 of the sensor element 10 so as to protrude from the inner peripheral surface toward the radially inner side in the circumferential direction.

  A screw part 62 for attaching the sensor 1 to an exhaust passage (not shown) of the internal combustion engine and an attachment tool for screwing the screw part 62 into the exhaust passage are associated with the outer peripheral surface on the front end side of the metal shell 60. A hexagonal portion 63 to be joined is provided in the circumferential direction. An annular gasket 64 is disposed between the screw portion 62 and the hexagonal portion 63. The gasket 64 prevents gas from being released from the gap between the sensor 1 and the exhaust passage.

  A front end engaging portion 65 to which a protector 80 described later is engaged is formed on the front end side of the metal shell 60 with respect to the screw portion 62. The tip engaging portion 65 is a portion formed with a smaller diameter on the outer peripheral surface than the screw portion 62. Further, a rear end engaging portion 66 engaged with the outer cylinder 90 and the sensor element 10 are added to the rear end side of the metal shell 60 from the hexagonal portion 63 in order from the hexagonal portion 63 toward the rear end side. A caulking and fixing portion 67 for fastening and fixing is formed.

  Inside the metal shell 60, in order from the step portion 61 toward the rear end side, a metal front end side packing 71, a cylindrical support member 72 made of alumina, a metal rear end side packing 73, and talc powder A filling member 74, an alumina sleeve 75, and an annular ring 76 are disposed. A step portion is formed on the inner peripheral surface of the support member 72, and the flange portion 14 of the element body 11 is supported by the step portion. The rear end side packing 73 is sandwiched between the support member 72 and the flange 14.

  The ring 76 is disposed between the sleeve 75 and the caulking and fixing portion 67, and a force in the distal direction applied by the caulking and fixing portion 67 being deformed radially inward and on the distal end side, This is transmitted to the filling member 74, the rear end side packing 73, the support member 72, and the front end side packing 71. By this pressing force, the filling member 74 is compressed and filled in the direction of the axis O, and airtightly fills the gap between the inner peripheral surface of the metal shell 60 and the outer peripheral surface of the element body 11.

  The protector 80 protects the sensor element 10 protruding into the flow path from collision of water droplets or foreign matters contained in the gas flowing in the flow path when the sensor 1 is attached to the exhaust flow path. . The protector 80 is a member formed of stainless steel (for example, JIS standard SUS310S), and is a protective member that covers the tip of the sensor element 10. The protector 80 is a cylindrical member extending in the axial direction, and is formed in a shape with a closed end. The rear end edge of the protector 80 is fixed to the front end engaging portion 65 of the metal shell 60 by welding.

  The protector 80 is formed in a bottomed cylindrical shape that is fixed to the inside of the outer protector 81 and an outer protector 81 in which a peripheral edge portion on the open side that is formed in a bottomed cylindrical shape is fitted to the tip engaging portion 65. An inner protector 82 is provided. In other words, the protector 80 has a double structure composed of the outer protector 81 and the inner protector 82.

  The cylindrical surface of the outer protector 81 and the inner protector 82 is provided with an inlet 83 for introducing gas into the inside. In FIG. 1, only the introduction port 83 of the outer protector 81 is shown, and the introduction port 83 of the inner protector 82 is not shown because of the arrangement. Furthermore, the bottom surface of the outer protector 81 and the inner protector 82 is provided with an outer discharge port 84 and an inner discharge port 85 for discharging water droplets and gas that have entered inside.

  The outer cylinder 90 is a member made of stainless steel (for example, JIS standard SUS304L) different from the metal shell 60, and the rear end engaging portion 66 of the metal shell 60 is inserted into the outer cylinder 90. It is fixed to the metal shell 60. Inside the outer cylinder 90, the rear end of the sensor element 10 protruding from the rear end of the metal shell 60, the separator 30, and the seal member 40 are disposed.

In the sensor 1 according to the first embodiment, the ceramic heater 100 according to the first embodiment is disposed in the cylindrical hole of the sensor element 10 as a heater for heating the sensor element 10.
FIG. 2 is a perspective view showing the appearance of the ceramic heater 100. FIG. 3 is an exploded perspective view showing the internal configuration of the ceramic heater 100.

  In the ceramic heater 100 of the present embodiment, of the both end portions in the axis AX direction, the side provided with the heat generating portion (the side where the heat generating portion 142 described later is formed) is referred to as the “tip side”, and the opposite side. The end portion will be described as “rear end side”.

  The ceramic heater 100 includes a round bar-shaped (substantially cylindrical) heater main body 102 having a heating resistor 141, and electrode pads 121 provided on the outer surface of the heater main body 102 and electrically connected to the heating resistor 141. And a metal terminal portion 130 joined to the electrode pad 121 by a conductive brazing material.

  When the ceramic heater 100 is energized to the heat generating resistor 141 from an external device (power supply device) via the electrode pad 121 provided on the rear end side of the heater main body 102, the heat generating resistor 141 generates heat. It is a configuration. Note that the heat generating portion 142 (see FIG. 2) of the heat generating resistor 141 is disposed on the front end side of the heater main body portion 102. That is, the ceramic heater 100 is configured to heat the sensor element 10 by generating heat at the front end side of the heater main body 102.

  As shown in FIG. 3, the ceramic heater 100 is manufactured by winding green sheets 140 and 146 made of alumina ceramic having high insulating properties around an outer periphery of a round rod-shaped alumina ceramic tube 101 and firing them. .

  On the green sheet 140, a heating resistor 141 mainly composed of a tungsten-based material as a heat pattern is formed. The heat generating resistor 141 includes a heat generating part 142 formed on the front end side, and a pair of lead parts 143 connected to both ends of the heat generating part 142. Further, the pair of lead portions 143 includes a front end side lead portion 143a formed on the front end side, a rear end side lead portion 143c formed on the rear end side, a front end side lead portion 143a, and a rear end side lead portion, respectively. And a connection lead part 143b for connecting to 143c. Note that the width A of the heat generating portion 142 is narrower than the width B of the leading end side lead portion 143a.

  Two conductor portions 144 are provided on the rear end side of the green sheet 140. The pair of lead portions 143 are electrically connected to the two electrode pads 121 formed on the outer surface of the ceramic heater 100 via the two conductor portions 144.

The green sheet 146 is a sheet that is pressure-bonded to the surface of the green sheet 140 on which the heat generating resistor 141 is formed.
Alumina paste is applied to the surface of the green sheet 146 opposite to the pressure contact surface in contact with the green sheet 140, and the green sheets 140 and 146 are wound around the tub tube 101 and pressed inward from the outer periphery with the applied surface facing inside. As a result, a ceramic heater molded body is formed. Thereafter, the ceramic heater molded body is fired to form the ceramic heater 100.

  Next, as shown in FIGS. 2 and 3, the ceramic heater 100 is formed with two electrode pads 121 on the anode side and the cathode side. The electrode pads 121 are provided at two positions on the outer surface of the green sheet 140 corresponding to the two conductor portions 144 (see FIG. 3). The conduction between the heating resistor 141 and the lead portion 143 is performed via a conductive paste filled in the conductor portion 144. A metal layer (plating film 122 for pads shown in FIG. 4) by plating described later is formed on the surface of the electrode pad 121.

  The metal terminal portion 130 is made of a long nickel member, and has a joint portion 133 joined to the electrode pad 121 by a brazing material, a caulking portion 135 cut out in a flat plate shape, and a joint portion 133 and a caulking portion 135. And a connecting portion 134 that connects the two.

  The distal end portion of the connecting portion 134 is bent stepwise in the thickness direction, and is formed so as to be connected to the joint portion 133. In addition, the metal terminal portion 130 is twisted so that a connection region of the connecting portion 134 with the caulking portion 135 rotates around the central axis in the longitudinal direction of the connecting portion 134.

  The metal terminal portion 130 is connected to the external circuit (external power supply device) via the lead wire 55 or the like by caulking and fixing the core wire of the lead wire 55 for connecting the external circuit to the caulking portion 135. It is done.

  The two metal terminal portions 130 configured as described above are joined to the two electrode pads 121 and function as an anode side terminal and a cathode side terminal when a voltage is applied to the ceramic heater 100.

  FIG. 4 is a partial cross-sectional view of the ceramic heater 100 shown in FIG. 2 in the vicinity of the joint portion 133 as viewed from the direction of the arrow along the one-dot chain line A-A ′. In FIG. 3, a direction from the metal terminal portion 130 toward the central axis of the ceramic heater 100 (downward in the drawing in the drawing) is a downward direction, and a direction away from the central axis (upward in the drawing in the drawing) is an upward direction. explain.

  As shown in FIG. 4, the electrode pad 121 is formed on the outer surface (upper surface in FIG. 3) of the green sheet 140 wound around the outer periphery of the soot tube 101, and the inner surface (see FIG. 3) of the green sheet 140 via the conductor portion 144. 3 is connected to the lead portion 143 of the heating resistor 141 formed on the lower surface).

  The electrode pad 121 is a pad-like metal layer containing 80% by weight or more of a main material composed of at least one element selected from tungsten and molybdenum. Tungsten and molybdenum are suitable for the composition of the electrode pad 121 because they have a high melting point and excellent heat resistance.

The metal terminal portion 130 is made of a nickel member containing 90% by weight or more of nickel. As shown in FIG. 4, the metal terminal portion 130 is joined to the electrode pad 121 covered with the pad plating film 122 by the brazing material portion 124. A nickel plating film 125 mainly composed of nickel (Ni) and a chromium plating film mainly composed of chromium (Cr) are further formed on the metal terminal portion 130 and the electrode pad 121 joined together by the brazing material portion 124. 126 is formed. A chromium plating film 126 is formed on the upper side of the nickel plating film 125, and the nickel plating film 125 and the chromium plating film 126 are provided to prevent corrosion of the brazing material portion 124 and the metal terminal portion 130 due to oxidation. .
Instead of the chromium plating film 126, a nickel plating film, a platinum plating film, or a gold plating film may be formed.

  And the brazing material part 124 which joins the electrode pad 121 and the metal terminal part 130 brazes the electrode pad 121 and the metal terminal part 130 using Au-Cu brazing material or Ag-Cu brazing material. Yes.

During brazing, the nickel component of the pad plating film 122 provided on the electrode pad 121 diffuses into the brazing material portion 124.
That is, in the ceramic heater 100 of the first embodiment, as shown in FIG. 3, the pad plating film 122 before brazing has a contour shape indicated by a dashed line 123 at the boundary with the brazing material portion 124. After the brazing, a part of the pad plating film 122 is diffused and melted into the brazing material portion 124, and the pad plating film 122 and the brazing material portion 124 are formed in an integrated state. .

  FIG. 5 is an explanatory diagram in which the electrode pad 121 of the ceramic heater 100 according to the first embodiment is viewed in a direction perpendicular to the axial direction. In FIG. 5, the brazing material portion 124 and the metal terminal portion 130 are omitted in order to clarify the positional relationship between the electrode pad 121 and the rear end side lead portion 143c. Further, although the lead portion 143 is embedded in the heater main body portion 102, it is indicated by a dotted line in FIG.

  As shown in FIG. 5, the rear end side lead portion 143c is disposed in a projection region S (shaded portion in FIG. 5) obtained by projecting the electrode pad 121 in a direction perpendicular to the axis AX direction (the front and back direction in FIG. 5). ing. Further, the width C of the rear end side lead portion 143c is narrower than the width D of the electrode pad 121 over the entire area in the projection region S. That is, both end edges 143cT of the rear end side lead part 143 are arranged on the inner side in the width direction so as not to overlap the boundary ST in the width direction of the projection region S. Thereby, even if the stress applied to the heater main body 102 due to the contraction of the rear end side lead part 143c and the contraction stress of the electrode pad 121 are generated, the directions of the stresses cancel each other. In the heater main body 102, it is possible to suppress the occurrence of cutting or cracking in the vicinity of the edge in the width direction of the electrode pad 121.

  This reason is shown in FIG. FIG. 6 is an explanatory view illustrating the effect of the invention of the ceramic heater 100 of the first embodiment, and is a green sheet 140 before being wound around the soot tube 101. As shown in FIG. 6, when a paste-like metal conductor is printed on the lower surface of the green sheet 140 to form a heat generating resistor 141 having a desired shape, the heat generating resistor 141 is subsequently dried to thereby generate the heat generating resistor. 141 contracts. That is, the heating resistor 141 (rear end side lead portion 143c) contracts inward in the width direction of the green sheet 140 as shown in FIG. 6 (see arrow W). Then, due to the shrinkage of the heating resistor 141, stress is applied to the upper side of the green sheet 140 on the outer side in the width direction (see arrow Y).

  After that, when a paste-like metal conductor is printed on the upper surface of the green sheet 140 and the electrode pad 121 is formed, the electrode pad 121 is dried in the width direction inner side by drying the electrode pad 121 like the heating resistor 141. Shrink (see arrow Z). However, in the first embodiment, the electrode pad 121 is disposed in the projection region S, and the width C of the rear end side lead portion 143c is made narrower than the width D of the electrode pad 121 over the entire region in the projection region S. Therefore, the direction of the stress (arrow Y) on the upper surface of the green sheet 140 due to the influence of the rear end side lead portion 143c and the direction of the stress (arrow Z) when the electrode pad 121 contracts are directed to cancel each other. Will occur.

  Under such circumstances, even when the green sheet 140 is wound around the soot tube 101, it is possible to suppress the occurrence of cuts, cracks, and the like in the vicinity of the edge in the width direction of the electrode pad 121 in the heater main body 102.

  Further, according to the ceramic heater 100 of the first embodiment, the heating portion 142 is wider than the width B of the leading end side lead portion 143a while the width B of the leading end side lead portion 143a is wider than the width C of the trailing end side lead portion 143c. The width A is narrow (see FIG. 3). In this way, by forming the leading end side lead portion 143a having the width B wider than the width A of the heat generating portion 141 and the width C of the rear end side lead portion 143c, it is possible to concentrate heat generation on the heat generating portion 142 more. Yes, the ceramic heater 100 can be used efficiently.

  Further, according to the ceramic heater 100 of the first embodiment, the width A of the heat generating part 141 is narrower than the width C of the rear end side lead part 143c. As described above, since the width A of the heat generating portion 141 is narrower than the width C of the rear end side lead portion 143c, heat generation is reliably concentrated on the heat generating portion 141 without generating heat at the rear end side lead portion 143c. Therefore, the ceramic heater 100 can be used efficiently.

  Further, according to the ceramic heater 100 of the first embodiment, the leading end side lead portion 143a and the trailing end side lead portion 143c are connected, and the connecting lead portion 143b whose width decreases toward the rear end side in the axis AX direction is provided. It is preferable. As described above, the tapered connection lead portion 143b whose width decreases toward the rear end side in the axis AX direction forms a corner portion where the electric field tends to concentrate on the front end side lead portion and the rear end side lead portion. Since it is not carried out, it can suppress that insulation falls.

  Furthermore, according to the ceramic heater 100 of the first embodiment, the connection lead portion 143b is disposed on the tip side of the projection region S. Accordingly, the width C of the rear end side lead portion 143c can be surely made narrower than the width D of the electrode pad 121 in the projection region S, and the electrode pad 121 of the heater main body portion 102 can be reduced. It is possible to further suppress the occurrence of cuts or cracks in the vicinity of the edge in the width direction.

  As mentioned above, although Embodiment 1 of this invention was demonstrated, this invention is not limited to the said Embodiment 1, In the range which does not deviate from the summary of this invention, it is possible to implement in various aspects. .

  For example, in the first embodiment, the connection lead part 143b has been described with respect to the front end side of the projection region S. However, the present invention is not limited to this. For example, as shown in FIG. 7, a part of the connection lead part 143b may overlap with the projection region S. However, the width of the connection lead portion 143b is preferably narrower than the width D of the electrode pad 121 in the projection region S.

DESCRIPTION OF SYMBOLS 1 ... Sensor 10 ... Sensor element 100 ... Ceramic heater 102 ... Heater main body part 121 ... Electrode pad 141 ... Heat generating resistor 142 ... Heat generating part 143 ... Lead part 143a ... Front end side lead part 143b ... Connection lead part 143c ... Rear end side lead Part S ... Projection area

Claims (5)

A round bar-shaped ceramic heater extending in the axial direction,
A heater body formed from an insulating ceramic;
A heating resistor embedded in the heater body,
An electrode pad disposed on the outer surface of the heater body and electrically connected to the heating resistor;
A conductor portion connecting the heating resistor and the electrode pad;
A ceramic heater comprising:
The heating resistor is
A rear end side lead portion that is disposed within a projection region in which the electrode pad is projected in a direction perpendicular to the axial direction and is narrower than the width of the electrode pad over the entire projection region;
A leading end side lead portion that is disposed on the leading end side of the trailing end side lead portion and wider than the width of the trailing end side lead portion;
A heat generating portion that is disposed closer to the tip side than the tip side lead portion and narrower than the width of the tip side lead portion;
A ceramic heater comprising: The ceramic heater according to claim 1,
The ceramic heater according to claim 1, wherein a width of the heat generating portion is narrower than a width of the rear end side lead portion. The ceramic heater according to claim 1 or 2,
The heat generating resistor includes a connection lead portion that connects the front end side lead portion and the rear end side lead portion, and has a connection lead portion that decreases in width toward the rear end side in the axial direction. The ceramic heater according to claim 3,
The ceramic heater according to claim 1, wherein the connection lead portion is arranged on a distal end side with respect to the projection region. A bottomed cylindrical sensor element;
A metal shell for holding the sensor element;
A ceramic heater disposed in the cylindrical hole of the sensor element;
A sensor comprising:
The said ceramic heater is a ceramic heater as described in any one of Claims 1 thru | or 4. The sensor characterized by the above-mentioned.