JP6059503B2 - Ceramic glow plug with pressure sensor - Google Patents

Description

  The present invention relates to a ceramic glow plug with a pressure sensor used for an internal combustion engine or the like.

  2. Description of the Related Art Conventionally, glow plugs used for diesel engine start assistance and the like include a cylindrical housing having an axial hole extending in the axial direction, a heater inserted through the axial hole, and the like. In recent years, a glow plug with a pressure sensor has been proposed in which a function for detecting pressure such as combustion pressure is provided for the glow plug.

  In addition, a ceramic heater may be employed as the heater. The ceramic heater includes a ceramic base having insulating properties and a ceramic heating element disposed inside the base and having conductivity. The heating element has an electrode extraction portion exposed on the outer surface of the base, and a conductive member electrically connected to a predetermined power source is in contact with the electrode extraction portion. Then, the heating element is heated by energizing the heating element through the electrode extraction portion (see, for example, Patent Document 1).

JP2012-154551A

  By the way, the electrode extraction part may become extremely high temperature due to heat received by the combustion operation of the engine and heat accompanying energization. Thus, when the electrode extraction part becomes high temperature, there exists a possibility that an electrode extraction part may be oxidized. As a result, the current-carrying resistance of the heat generating element increases, and there is a possibility that the power supply to the heat generating element may be hindered.

  The present invention has been made in view of the above circumstances, and the object thereof is to effectively suppress the temperature rise of the electrode extraction portion, and more reliably prevent oxidation of the electrode extraction portion and thus the current-carrying failure to the heating element. It is an object of the present invention to provide a ceramic glow plug with a pressure sensor that can be prevented.

  Hereinafter, each configuration suitable for solving the above-described object will be described in terms of items. In addition, the effect specific to the corresponding structure is added as needed.

Configuration 1. The ceramic glow plug with a pressure sensor of this configuration includes a cylindrical housing having an axial hole extending in the axial direction,
A ceramic heater inserted into the shaft hole in a state in which at least a tip portion thereof protrudes from a tip of the housing;
A cylindrical movable member that is deformable along the axis and that is directly or indirectly joined to the housing and holds the ceramic heater in a state of being relatively displaceable along the axis with respect to the housing. When,
A pressure sensor that is directly or indirectly joined to the housing and detects a pressure based on a relative displacement of the ceramic heater;
The ceramic heater is
A base made of insulating ceramic;
And having a heating element provided in the substrate,
The heating element is a ceramic glow plug with a pressure sensor having an electrode extraction part exposed on the outer surface of the base body,
Of the members directly or indirectly joined to the ceramic heater, at least a part of the portion exposed to the atmosphere has a surface emissivity of 0.75 or more.

  In addition, it can be said that "the part exposed to the atmosphere" is a part that is not in contact with other members.

  According to the configuration 1, at least a part of the portion exposed to the atmosphere among the members directly or indirectly joined to the ceramic heater including the electrode extraction portion has a surface emissivity of 0.75 or more. . Accordingly, heat dissipation and heat absorption (that is, heat exchange with the atmosphere) on the surface of the member can be promoted, and the temperature rise of the ceramic heater and thus the electrode extraction portion can be effectively suppressed. As a result, it is possible to effectively prevent oxidation of the electrode lead-out portion and, in turn, poor conduction to the heating element.

  Configuration 2. In the ceramic glow plug with a pressure sensor of this configuration, the emissivity of the surface of at least a part of the portion exposed to the atmosphere among the members directly bonded to the ceramic heater in the above configuration 1 is 0.75 or more. It is characterized by.

  According to the above configuration 2, the temperature rise of the electrode extraction portion can be more effectively suppressed, and the energization reliability for the heating element can be further increased.

  Configuration 3. In the ceramic glow plug with a pressure sensor of this configuration, in the above configuration 1 or 2, at least a part of the portion exposed to the atmosphere among the members in contact with the electrode extraction portion has a surface emissivity of 0.75 or more. It is characterized by that.

  According to the configuration 3, since heat dissipation and heat absorption can be promoted in the member in contact with the electrode extraction portion, the temperature increase of the electrode extraction portion can be further effectively suppressed. As a result, it is possible to further improve the energization reliability for the heating element.

Configuration 4. In the ceramic glow plug with a pressure sensor according to this configuration, in any one of the above configurations 1 to 3, the electrode extraction portion includes a first electrode extraction portion and a second electrode provided on a distal end side with respect to the first electrode extraction portion. An electrode extraction part,
At least a part of the portion exposed to the atmosphere among the members in contact with the second electrode extraction portion has a surface emissivity of 0.75 or more.

  The second electrode extraction portion is provided on the tip side (the side closer to the combustion chamber) than the first electrode extraction portion, and is likely to be at a higher temperature. According to the configuration 4, the member that contacts the second electrode extraction portion The emissivity of the surface is 0.75 or more in at least a part of the portion exposed to the atmosphere. Therefore, the temperature rise of the second electrode extraction portion can be extremely effectively suppressed, and oxidation of the electrode extraction portion can be more reliably prevented. As a result, it is possible to further improve the energization reliability for the heating element.

  Configuration 5. In the ceramic glow plug with a pressure sensor of this configuration, in any one of the above configurations 1 to 4, at least a part of the movable member exposed to the atmosphere has a surface emissivity of 0.75 or more. Features.

  According to the said structure 5, the heat dissipation and heat absorption in a movable member can be accelerated | stimulated, and the temperature rise of a ceramic heater and by extension, an electrode extraction part can be suppressed more effectively. As a result, it is possible to further improve the energization reliability for the heating element.

Configuration 6. The ceramic glow plug with pressure sensor of this configuration is a cylinder in which the ceramic heater is disposed on the inner periphery of the ceramic glow plug directly or indirectly joined to the tip of the housing in any of the above configurations 1 to 5. A cap member,
At least a part of the cap member exposed to the atmosphere has a surface emissivity of 0.75 or more.

  According to the configuration 6, at least a part of the portion of the cap member arranged on the outer periphery of the ceramic heater that is exposed to the atmosphere has a surface emissivity of 0.75 or more. Therefore, it is possible to more effectively suppress the temperature rise of the ceramic heater and thus the electrode extraction portion, and the energization reliability to the heating element can be further enhanced.

Configuration 7. The ceramic glow plug with a pressure sensor of the present configuration has any one of the above-described configurations 1 to 6, wherein at least one of the members directly or indirectly joined to the ceramic heater has an inner peripheral surface exposed to the atmosphere.
The emissivity of the surface is 0.75 or more in the whole area of the inner peripheral surface exposed to the atmosphere.

  According to the structure 7, heat dissipation and heat absorption in the member can be further promoted. As a result, the temperature rise of the electrode extraction portion can be more effectively suppressed, and the energization reliability with respect to the heating element can be remarkably improved.

Configuration 8. In the ceramic glow plug with a pressure sensor of this configuration, in any one of the above configurations 1 to 7, at least one of the members joined directly or indirectly to the ceramic heater has an outer peripheral surface exposed to the atmosphere,
The emissivity of the surface is 0.75 or more in the whole area of the outer peripheral surface exposed to the atmosphere.

  According to the configuration 8, heat dissipation and heat absorption in the member can be further promoted. As a result, the temperature rise of the electrode extraction portion can be extremely effectively suppressed, and the energization reliability for the heating element can be significantly increased.

It is a partially broken front view which shows the structure of a glow plug. It is an expanded sectional view which shows the structure of a glow plug.

  Hereinafter, an embodiment will be described with reference to the drawings. FIG. 1 is a partially broken front view of a ceramic glow plug 1 with a pressure sensor (hereinafter simply referred to as “glow plug 1”). In FIG. 1, the lower side of the figure is described as the front end side of the glow plug 1, and the upper side is described as the rear end side.

  As shown in FIG. 1, the glow plug 1 includes a housing 2, a cap member 3, a center shaft 4, a ceramic heater 5, a pressure sensor 6, and the like.

  The housing 2 is formed of a predetermined metal material (for example, an iron-based material such as S45C) and has a shaft hole 7 extending along the direction of the axis CL1. Furthermore, a male screw portion 8 for attaching the glow plug 1 to an engine cylinder head or the like is formed on the outer periphery of the housing 2. In addition, a tool engaging portion 9 having a hexagonal cross section is formed on the outer periphery of the rear end portion of the housing 2. When the glow plug 1 (male thread portion 8) is attached to the cylinder head or the like, the tool engaging portion The tool used for 9 is engaged.

  Furthermore, a metal sensor fixing member 10 having a cylindrical shape extending along the direction of the axis CL1 is inserted into the inner periphery of the distal end portion of the housing 2. The sensor fixing member 10 has a distal end joined to the distal end of the housing 2 and a rear end joined to a diaphragm 23 described later of the pressure sensor 6. Thereby, the pressure sensor 6 is in a state of being indirectly fixed to the housing 2 via the sensor fixing member 10.

  The cap member 3 has a cylindrical shape and is joined to the distal end portion of the housing 2 via the distal end portion of the sensor fixing member 10. Further, the outer peripheral surface on the front end side of the cap member 3 is tapered so as to taper toward the front end side in the direction of the axis CL1, and when the glow plug 1 is attached to the engine, the tapered portion becomes the seat surface of the engine. By pressure-contacting, the airtightness in the combustion chamber is ensured.

  The middle shaft 4 is inserted into the shaft hole 7, and is made of metal and has a rod shape extending along the axis CL1. Further, the front end portion of the middle shaft 4 is press-fitted into the rear end portion of the cylindrical first ring member 11 formed of a predetermined metal (for example, an iron-based material such as SUS), and the first ring member 11 The rear end portion of the ceramic heater 5 is press-fitted into the front end portion. Thereby, the middle shaft 4 and the ceramic heater 5 are mechanically and electrically connected via the first ring member 11.

  The ceramic heater 5 is inserted into the shaft hole 7 in a state where the tip end of the ceramic heater 5 protrudes from the tip of the housing 2 (cap member 3). The ceramic heater 5 includes a cylindrical base body 12 extending in the direction of the axis CL1 and a heating element 13 which is disposed inside the base body 12 and has a long and thin U shape. The base 12 is made of an insulating ceramic (for example, silicon nitride or alumina), while the heating element 13 is mainly composed of silicon nitride and is made of a conductive material (for example, silicide or nitride of molybdenum or tungsten). , Carbides, etc.).

  The heat generating element 13 includes a U-shaped heat generating portion 14 disposed at the front end portion of the ceramic heater 5 and a pair of rod-shaped lead portions 15 extending from the respective end portions of the heat generating portion 14 toward the rear end side. , 16. The heat generating part 14 is a part that functions as a so-called heat generating resistor, and has a U-shape along the curved surface at the tip of the ceramic heater 5 formed in a curved surface.

  Furthermore, the lead parts 15 and 16 are extended substantially parallel to each other toward the rear end side of the ceramic heater 5. Further, a first electrode extraction portion 17 is provided projecting in the outer peripheral direction at a position near the rear end of one lead portion 15, and the first electrode extraction portion 17 is exposed on the outer peripheral surface of the base 12. . Further, a second electrode lead-out portion 18 is provided projecting in the outer peripheral direction at a position near the rear end of the other lead portion 16, and the second electrode lead-out portion 18 is exposed on the outer peripheral surface of the base 12. Yes. In addition, the 2nd electrode extraction part 18 is located in the front end side rather than the 1st electrode extraction part 17 along the axis line CL1 direction.

  In addition, as shown in FIG. 2, the exposed portion of the first electrode extraction portion 17 is in contact with the inner peripheral surface of the first ring member 11, and the central shaft 4 connected to the first ring member 11 and the lead Electrical continuity with the portion 15 is achieved. Further, the exposed portion of the second electrode extraction portion 18 is in contact with an inner peripheral surface of a second ring member 22 (described later) that is electrically connected to the housing 2, and the electrical connection between the housing 2 and the lead portion 16. Continuity is achieved. That is, in the present embodiment, the middle shaft 4 and the housing 2 function as an anode / cathode for energizing the heat generating portion 14 of the ceramic heater 5 in the glow plug 1.

  Further, in the present embodiment, the ceramic heater 5 is attached to the housing 2 via a cylindrical movable member 19 whose other end is joined to the distal end portion of the housing 2 and can be expanded and contracted along the axis CL1. Yes. Therefore, the ceramic heater 5 can be displaced relative to the housing 2 along the direction of the axis CL1 when a pressure such as a combustion pressure is applied to the tip portion thereof.

  In addition, since the outer surface of the ceramic heater 5 is formed of ceramic, the ceramic heater 5 and the movable member 19 cannot be directly welded. Therefore, in the present embodiment, the ceramic heater 5 and the outer cylinder 20 are joined by press-fitting the ceramic heater 5 into the inner periphery of the cylindrical outer cylinder 20 formed of a predetermined metal (for example, SUS630). In the above, one end side (tip side) of the movable member 19 is welded to the outer cylinder 20 by laser welding or resistance welding. The outer cylinder 20 is inserted through the cap member 3 in a state of being separated from the inner peripheral surface of the cap member 3.

  In addition, the movable member 19 has an opening on one end side having a relatively small diameter, and an opening on the other end is formed in a relatively large diameter. Then, it has two bent portions. For this reason, the movable member 19 can be stretched and deformed along the axis CL1 in combination with being formed thin with a predetermined metal (for example, stainless steel or nickel alloy).

  In the present embodiment, the movable member 19 is welded to the outer cylinder 20 at one end side over the entire circumference, and is welded to the tip end portion of the housing 2 over the entire circumference. Yes. Thereby, it is possible to more reliably prevent the combustion gas that has entered from the gap between the cap member 3 and the outer cylinder 20 from entering the housing 2 and eventually leaking to the outside.

  In addition, the relative displacement of the ceramic heater 5 is transmitted to the pressure sensor 6 via a cylindrical transmission member 21 whose rear end is connected to the pressure sensor 6 (diaphragm 23). (See FIG. 1). Since the outer surface of the ceramic heater 5 is formed of ceramic, the transmission member 21 and the ceramic heater 5 cannot be directly welded as in the case of the movable member 19. Therefore, in the present embodiment, the ceramic heater 5 is press-fitted into the cylindrical second ring member 22 made of a predetermined metal (for example, SUS630), and the ceramic heater 5 and the ring member 22 are joined, and then laser welding is performed. Further, the distal end portion of the transmission member 21 is welded to the outer periphery of the rear end portion of the second ring member 22 by resistance welding.

  Returning to FIG. 1, the pressure sensor 6 is provided on the front end side of the center portion of the housing 2 in the direction of the axis CL <b> 1, and a diaphragm 23 made of metal (for example, stainless steel) having a through-hole through which the central shaft 4 passes in the center. And a sensor element 24 (in this embodiment, a piezoresistor) joined to the surface on the rear end side of the diaphragm 23. The rear end portion of the transmission member 21 is joined to the diaphragm 23, and when the ceramic heater 5 is displaced by receiving pressure such as combustion pressure, the diaphragm 23 corresponds to the amount of displacement of the ceramic heater 5. Is bent and deformed.

  In addition, the sensor element 24 changes its own resistance value as the diaphragm 23 is bent and deformed. The resistance value of the sensor element 24 is converted / amplified into a voltage value by an integrated circuit 25 provided in the housing 2, and the converted / amplified voltage value signal (that is, a signal indicating the pressure received by the ceramic heater 5). ) Is output to an external circuit (not shown) such as an ECU via a cable (not shown). In the external circuit, the pressure based on the relative displacement of the ceramic heater 5 is detected.

  Further, in the present embodiment, the portion exposed to the atmosphere among the members joined directly or indirectly to the ceramic heater 5 has a surface emissivity of 0 by applying a black synthetic resin paint, for example. .75 or more.

  More specifically, the housing 2, the cap member 3, the sensor fixing member 10, the movable member 19, and the transmission member 21 are members that are indirectly joined to the ceramic heater 5 via other members. In this embodiment, at least a part of the housing 2, the sensor fixing member 10, and the transmission member 21 exposed to the atmosphere has a surface emissivity of 0.75 or more.

  Moreover, the cap member 3 is exposed to the atmosphere on almost the entire inner peripheral surface and outer peripheral surface thereof, and the entire surface of the cap member 3 exposed to the air has a surface emissivity of 0.75 or more. ing.

  In addition, the movable member 19 is almost exposed to the atmosphere on the inner peripheral surface and the outer peripheral surface thereof, and in this embodiment, the entire region of the inner peripheral surface and the outer peripheral surface of the movable member 19 exposed to the atmosphere. Has a surface emissivity of 0.75 or more.

  Furthermore, the first ring member 11, the outer cylinder 20, and the second ring member 22 are members that are directly joined to the ceramic heater 5. In the present embodiment, the outer cylinder 20 has almost the entire outer peripheral surface exposed to the atmosphere, and the entire area of the outer peripheral surface of the outer cylinder 20 exposed to the air has a surface emissivity of 0. 75 or more.

  In addition, the entire area of the outer peripheral surface of the first ring member 11 that is in contact with the first electrode extraction portion 17 is exposed to the atmosphere, and the emissivity of the surface is set to 0.75 or more over the entire outer peripheral surface. ing.

  At the same time, the entire area of the outer peripheral surface of the second ring member 22 that is in contact with the second electrode extraction portion 18 is exposed to the atmosphere, and the emissivity of the surface of the second ring member 22 is 0.75 or more over the entire area of the outer peripheral surface. ing.

  In addition, in each of the members joined directly or indirectly to the ceramic heater 5, the position and range where the surface emissivity is 0.75 or more may be appropriately changed. In order to sufficiently improve heat dissipation and heat absorption, the surface emissivity is preferably 0.75 or more in the range of 10% or more of the surface area of the member, and the surface in the range of 25% or more of the surface area of the member. The emissivity of the surface is more preferably 0.75 or more, and the emissivity of the surface is more preferably 0.75 or more in the range of 40% or more of the surface area of the member.

  As described above in detail, according to the present embodiment, the members (housing 2, cap member 3, sensor fixing member 10, first ring member 11, movable member 19, and the like directly or indirectly joined to the ceramic heater 5 are used. At least a portion of the outer cylinder 20, the transmission member 21, and the second ring member 22) exposed to the atmosphere has a surface emissivity of 0.75 or more. Therefore, heat dissipation and heat absorption can be promoted in each member. Thereby, the temperature rise of the ceramic heater 5 and by extension, the electrode extraction parts 17 and 18 can be suppressed effectively. As a result, it is possible to prevent the electrode extraction portions 17 and 18 from being oxidized more reliably, and to effectively prevent a failure in energization of the heating element 13.

  In particular, in the present embodiment, the surface emissivity of the members exposed to the atmosphere among the members (the first ring member 11, the outer cylinder 20, and the second ring member 22) directly joined to the ceramic heater 5 is 0. 75 or more. Therefore, the temperature rise of the electrode extraction parts 17 and 18 can be suppressed more effectively, and the energization reliability for the heating element 13 can be further improved.

  Moreover, in this embodiment, the surface emissivity is 0.75 or more in the part exposed to the atmosphere among the members (the first ring member 11 and the second ring member 22) in contact with the electrode extraction portions 17 and 18. It is said that. Therefore, the temperature rise of the electrode extraction parts 17 and 18 can be suppressed very effectively, and the energization reliability for the heating element 13 can be further enhanced.

  In addition, in the present embodiment, surface radiation is performed in the entire area of the first ring member 11, the movable member 19, the outer cylinder 20, and the second ring member 22 that is exposed to the atmosphere on the outer peripheral surface and the inner peripheral surface. The rate is 0.75 or more. Therefore, heat dissipation and heat absorption can be further promoted in the first ring member 11, the movable member 19, and the like. As a result, the temperature rise of the electrode extraction parts 17 and 18 can be suppressed extremely effectively, and the energization reliability with respect to the heating element 13 can be remarkably enhanced.

  In addition, it is not limited to the description content of the said embodiment, For example, you may implement as follows. Of course, other application examples and modification examples not illustrated below are also possible.

  (A) In the above embodiment, the surface emissivity of at least some of the parts exposed to the atmosphere is 0.75 or more in all the members joined directly or indirectly to the ceramic heater 5. In at least one of the members joined directly or indirectly to the ceramic heater 5, at least a part of the portion exposed to the atmosphere only needs to have the above emissivity.

  (B) In the above embodiment, the ceramic heater 5 is fixed to the outer cylinder 20 and the second ring member 22 by being press-fitted into the outer cylinder 20 and the second ring member 22. The fixing method between the heater 5 and the outer cylinder 20 is not particularly limited. Therefore, for example, the ceramic heater 5 and the outer cylinder 20 may be fixed by brazing or the like.

  (C) The arrangement position of the pressure sensor 6 in the above embodiment is an exemplification, and the arrangement position of the pressure sensor 6 is not particularly limited. Therefore, for example, a pressure sensor may be provided on the inner periphery of the rear end side of the housing 2 or a pressure sensor may be provided outside the housing 2.

  (D) In the above embodiment, a piezoresistor is cited as the sensor element, but a piezoelectric element or the like may be used as the sensor element.

  (E) In the above embodiment, the ceramic heater 5 has a round bar shape, that is, a circular cross section. However, the ceramic heater 5 does not necessarily have a circular cross section. It may be a shape. The technical idea of the present invention may be applied to a so-called plate heater in which a plurality of plate-like substrates are formed and a heating element is sandwiched therebetween.

  (F) The movable member 19 only needs to be deformable along the direction of the axis CL1, and the shape thereof is not particularly limited. Therefore, for example, a movable member having a bellows-like cylindrical portion extending in the direction of the axis CL1 may be used. Moreover, you may use the cyclic | annular member which extends in the direction which cross | intersects the axis line CL1, and can bend and deform in the direction of the axis line CL1.

  (G) In the above embodiment, the entire heating element 13 (the heating part 14 and the lead parts 15 and 16) is made of conductive ceramic, but a part of the heating element 13 is made of a material other than the conductive ceramic. May be formed. Therefore, for example, only the heat generating portion 14 may be formed of a conductive ceramic, and the lead portions 15 and 16 may be formed of a metal having excellent heat resistance (for example, tungsten or a metal including the same).

  DESCRIPTION OF SYMBOLS 1 ... Glow plug (ceramic glow plug with a pressure sensor), 2 ... Housing, 3 ... Cap member, 5 ... Ceramic sensor, 6 ... Pressure sensor, 7 ... Shaft hole, 10 ... Sensor fixing member, 11 ... 1st ring member, DESCRIPTION OF SYMBOLS 12 ... Base | substrate, 13 ... Heat generating element, 17 ... 1st electrode extraction part, 18 ... 2nd electrode extraction part, 19 ... Movable member, 20 ... Outer cylinder, 21 ... Transmission member, 22 ... 2nd ring member, CL1 ... Axis line .

Claims (8)

A cylindrical housing having an axial hole extending in the axial direction;
A ceramic heater inserted into the shaft hole in a state in which at least a tip portion thereof protrudes from a tip of the housing;
A cylindrical movable member that is deformable along the axis and that is directly or indirectly joined to the housing and holds the ceramic heater in a state of being relatively displaceable along the axis with respect to the housing. When,
A pressure sensor that is directly or indirectly joined to the housing and detects a pressure based on a relative displacement of the ceramic heater;
The ceramic heater is
A base made of insulating ceramic;
And having a heating element provided in the substrate,
The heating element is a ceramic glow plug with a pressure sensor having an electrode extraction part exposed on the outer surface of the base body,
A ceramic glow plug with a pressure sensor, characterized in that at least a part of a portion exposed to the atmosphere among members directly or indirectly joined to the ceramic heater has a surface emissivity of 0.75 or more.   2. The ceramic glow plug with pressure sensor according to claim 1, wherein a surface emissivity of at least a part of a part exposed to the atmosphere among members directly joined to the ceramic heater is 0.75 or more. .   3. The ceramic glow with pressure sensor according to claim 1, wherein a surface emissivity of at least a part of a portion exposed to the atmosphere among members in contact with the electrode extraction portion is 0.75 or more. plug. The electrode extraction part has a first electrode extraction part and a second electrode extraction part provided on the tip side of the first electrode extraction part,
The emissivity of the surface of at least a part of the part exposed to the atmosphere among the members in contact with the second electrode extraction part is 0.75 or more. Ceramic glow plug with pressure sensor as described.   5. The ceramic glow with a pressure sensor according to claim 1, wherein an emissivity of a surface of at least a part of the movable member exposed to the atmosphere is 0.75 or more. plug. It is directly or indirectly joined to the front end of the housing, and includes a cylindrical cap member in which the ceramic heater is disposed on its inner periphery,
6. The ceramic glow with a pressure sensor according to claim 1, wherein the emissivity of a surface of at least a part of the cap member exposed to the atmosphere is 0.75 or more. plug. At least one of the members directly or indirectly joined to the ceramic heater has an inner peripheral surface exposed to the atmosphere,
The ceramic glow plug with a pressure sensor according to any one of claims 1 to 6, wherein the emissivity of the surface is 0.75 or more in the whole area of the inner peripheral surface exposed to the atmosphere. . At least one of the members directly or indirectly joined to the ceramic heater has an outer peripheral surface exposed to the atmosphere,
8. The ceramic glow plug with a pressure sensor according to claim 1, wherein the emissivity of the surface is 0.75 or more in the entire area of the outer peripheral surface exposed to the atmosphere. 9.

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