JP6016506B2 - Ceramic glow plug with combustion pressure sensor - Google Patents

Description

  The present invention relates to a ceramic glow plug with a combustion pressure detection sensor having a function of accelerating ignition in a combustion chamber of an engine and detecting (detecting) a combustion pressure in addition thereto.

  Various types of ceramic glow plugs with this kind of combustion pressure detection sensor (hereinafter also simply referred to as glow plugs) are known (for example, Patent Documents 1 and 2). FIG. 7 is a cutaway longitudinal sectional view showing a simplified sectional structure of a glow plug 901 of the same type. In the figure, a rod-shaped (circular shaft-shaped) ceramic heater 10 that generates heat when energized is placed in a cylindrical housing 40, and its tip (end on the side protruding into the combustion chamber; lower end in the figure) 10a. Is provided so as to protrude from the front end 53 of the housing 40. 7 and FIG. 8 indicate the vicinity of the combustion chamber in the engine head H.

  In such a glow plug 901, a ceramic heater (hereinafter also simply referred to as a heater) 10 in the housing 40 for detecting the combustion pressure is about several tens of μm in the axis (axis) G direction (front-rear direction). Although it is minute, it is arranged so that it can be displaced. Therefore, the heater 10 is disposed with a gap (annular gap K) between the inner peripheral surface 55 of the housing 40. An energizing shaft member 60 is provided behind the heater 10 in a coaxial butted manner via a connecting pipe 19. As a result, the displacement (or pressure) generated when the heater 10 is pushed rearward from the tip 10a by the combustion pressure is applied to, for example, the strain member 210 provided rearward via the shaft member 60 and attached thereto. The detected strain sensor (strain gauge) 220 detects (measures) the amount of strain so as to detect the combustion pressure.

  By the way, in this glow plug 901, high-temperature, high-pressure combustion gas passes through the clearance (annular gap K) on the distal end side from the distal end 53 of the housing 40 to the outer peripheral surface of the heater 10. It is necessary to prevent the passage through the rear of the housing 40 (to ensure a seal). For this reason, in the glow plug 901 of the same figure, the metal seal member 30 that prevents the intrusion of combustion gas is inserted into the annular space formed inside the rear side following the distal end portion (the distal end side housing 50) of the housing 40. I have. Since the seal member 30 allows displacement of the heater 10 in the axis G direction with respect to the housing 40, a metal thin film (for example, made of SUS304 or SUS630, which is easily deformable itself, such as a bellows or a diaphragm, 0.1 A thin film having a thickness of 0.2 mm) and a ring-shaped or cylindrical shape having a sufficiently flexible annular film portion (membrane).

  In the seal member 30 in the figure, the rear end 35 side has a large diameter and the front end 32 side has a small diameter bellows. The bellows is fixed to the inner peripheral surface of the housing 40 on the rear end 35 side and to the outer peripheral surface of the portion near the rear end of the ceramic heater 10 on the front end 32 side so as to maintain airtightness along the circumferential direction. ing. By disposing such a seal member 30 in the space in the housing 40, the front and rear thereof are shut off in an airtight manner, and a seal (airtight) between the inner space K2 and the outside on the front end side is maintained. Since the heater 10 is a ceramic heater in which a heating element 12 is formed in a rod-shaped ceramic base 11, a metal seal member 30 is directly attached to the outer peripheral surface 11b of the ceramic base 11. It cannot be welded. For this reason, a thin (0.3 to 0.5 mm) metal (for example, SUS630) pipe 20 is externally fitted to the ceramic base 11, and the tip 20 of the seal member 30 is close to the outer peripheral surface 24 of the pipe 20. The part is laser-welded, for example, in the circumferential direction at a predetermined position (a black triangle in FIG. 8). The grounding electrode 16 of the heating element 12 is connected to the housing 40 via the pipe 20 and the seal member 30, and the other electrode 17 is connected to the shaft member 60 via the connection pipe 19 described above. Yes.

  On the other hand, between the inner peripheral surface 22 of the pipe 20 and the outer peripheral surface 11b of the ceramic base 11 constituting the heater 10, the pipe 20 is tightly fitted to the ceramic base 11 by press fitting or the like in order to keep the airtight therebetween. It is fitted outside. Moreover, in order to maintain the airtightness at a high level, the surface roughness of the outer peripheral surface 11b of the ceramic substrate 11 is, for example, Ra, 0.15 to 0.2 μm or less, and the surface roughness of the inner peripheral surface 22 of the pipe 20 In addition, for example, Ra was 0.15 to 0.2 μm or less. That is, the outer peripheral surfaces 22 and 11b of the pipe 20 and the ceramic base 11 are made to have a high degree of surface finish, and then the ceramic base 11 is press-fitted into the pipe 20 to make an interference fit between the inner and outer peripheral surfaces. The airtightness of the front and rear direction was secured.

JP 2009-520941 A JP 2011-089688 A

  However, the above-described ceramic glow plug with a combustion pressure detection sensor has a problem that pressure detection accuracy is lowered. This is because gas (GAS) enters from the front end side toward the rear through the space between the outer peripheral surface 11b of the ceramic base 11 constituting the heater 10 and the inner peripheral surface 22 of the pipe 20 fitted on the outer surface. . This is because this gas enters the space K2 at the back (inside) of the glow plug partitioned by the seal member 30 as shown by the broken line arrow in FIG.

  That is, in this glow plug 901, the combustion pressure (combustion gas pressure) is received by the surface on the combustion chamber side of the seal member 30 together with the tip 10 a of the heater 10, so that the distortion due to the heater 10 being pressed rearward. Since the strain sensor 220 detects the strain of the member 210 or detects the pressure based on the compression of the piezoelectric element, when gas enters the inner space K2 partitioned by the seal member 30. Since the space K2 has a high temperature and a high pressure, the sensor is affected by noise. In addition, since the pressure in the opposite direction is applied to the seal member 30, the pressing force and displacement to the rear of the heater 10 are reduced. Based on these facts, the accuracy of pressure detection decreases.

  Further, the gas entering the gap between the inner peripheral surface 22 of the pipe 20 and the outer peripheral surface 11b of the ceramic base 11 means that the heating element 12 forming the ceramic heater 10 does not enter the inner space K2. This is a problem in that heat is not easily transmitted to the pipe 20. That is, the heat is less likely to be conducted (heated) to the housing 40 and the engine head H via the pipe 20 and the seal member 30, which causes a problem that the temperature behind the glow plug 901 increases.

  The inventors of the present invention inferred the cause of the gas intrusion as described above. Since this type of glow plug is attached so that both ends of the ceramic heater 10 and the pipe 20 fitted on the ceramic heater 10 are exposed in the combustion chamber, both of them become higher in temperature toward the tip side. Even when exposed to such a high temperature, the thermal expansion of the ceramic substrate 11 forming the ceramic heater 10 can be ignored. On the other hand, since the pipe 20 is made of metal, it relatively thermally expands. For this reason, even if both of them are initially in an interference fit state, the pipe 20 is relatively greatly thermally expanded to increase its diameter, so that the internal stress of the pipe 20 due to the interference fit is reduced, and finally A gap is generated between the inner peripheral surface 22 and the outer peripheral surface 11 b of the ceramic substrate 11. In particular, in the enlarged view of FIG. 7, as indicated by the two-dot chain line in FIG. 8 and in an exaggerated manner in FIG. 10, the pipe 20 becomes hotter toward the rear end 20b toward the tip 20a side (lower end in the figure), It expands to greatly expand its diameter. And it thought that the gap which generate | occur | produces in this way is a cause which makes gas enter into back. On the other hand, the inventor of the present application tried to solve the above problem by increasing the fastening allowance (contact surface pressure) of the pipe 20 with respect to the ceramic base 11 as much as possible. I didn't. Under such circumstances, the inventor of the present application also fixes the sealing member 30 to the metal pipe 20 that is externally fitted to the ceramic base 11 by welding (usually laser welding) in the ceramic heater 10. I thought there might be a cause.

  Then, when this welded part was examined, the following was found. As exaggeratedly shown in FIG. 9, in such a welded part W <b> 1, the inner peripheral surface 22 of the pipe 20 is recessed outward in the radial direction, and a very small but concave portion 22 c is provided along the circumferential direction. I found out that it was happening. And this recessed part 22c forms a fine space | gap between the outer peripheral surfaces 11b of the ceramic base | substrate 11, and this space | gap (henceforth the space | gap 22c) also causes the above-mentioned airtight fall. I inferred.

  Such a recess 22c is considered to occur as follows. When the seal member 30 is fitted on the pipe 20 fitted on the ceramic base 11 and welded in a circular shape from the outer peripheral surface side near the tip 32, the molten metal is cooled and solidified during the welding process. The pipe 20 is cooled and solidified from a portion closer to the inner peripheral surface 22 toward the outer peripheral surface 24 side. For this reason, the outer peripheral surface 24 side of the welding part W1 is cooled and solidified last. Due to the shrinkage in the cooling and solidifying process and the stress generated due to the shrinkage, the welded portion W1 in the pipe 20 generates a welding strain that is pulled outward in the radial direction by heat shrinkage. As a result, a concave portion 22c is formed in the inner peripheral surface 22 that is first solidified, and a gap is generated between the ceramic base 11 and the outer peripheral surface 11b (hereinafter, this gap is also indicated by reference numeral 22c).

  Actually, when the welded part W1 is cut and examined, a gap 22c as shown in FIG. 9 is confirmed. When the welded portion W1 has a width of about 2 mm in the thick pipe 20 or the seal member 30, the concave portion 22c of the inner peripheral surface 22 of the pipe 20 has a radially outward depth D1 of 1 It is confirmed that the width Wh in the front-rear direction extends to about 1 mm after the front end of the welded part W1 at about 3 μm. It is considered that the gas enters the space K2 at the back (inside) of the glow plug because of the thermal expansion of the pipe 20 and the generation of a gap due to the recess 22c.

  That is, as described above, the pipe 20 is thermally expanded so as to expand its diameter, and a gap is generated between the inner peripheral surface 22 of the pipe 20 and the outer peripheral surface 11b of the ceramic base 11, so that the combustion gas enters the gap. Get in. Then, this gas tends to enter the gap in the welded part W <b> 1 of the seal member 30. On the other hand, the gap locally increases in the gap 22c. Further, the welded part is usually a part near the rear end of the pipe 20. Accordingly, as exaggeratedly shown in FIG. 10, the gas that has entered the gap 22 c is deformed so that the front end side of the pipe 20 is greatly opened with the gap 22 c as a fulcrum. Try to invade towards. By repeating such a thermal cycle, it is considered that the gas finally breaks through the rear end of the pipe 20 starting from this gap 22c and enters the space K2 behind the glow plug behind it.

  In the inventor of the present application, such a problem is caused by reducing the gap generated under the thermal cycle as described above between the inner peripheral surface 22 of the pipe 20 and the outer peripheral surface 11b of the ceramic base 11, and by welding. It was thought that the problem can be solved by preventing the generation of voids due to the concave portions 22c generated on the inner peripheral surface 22 of the above. On the other hand, the depth D1 of the concave portion forming the gap 22c is about 1 to 3 μm, which is the same as the maximum unevenness in the surface roughness (Ra) level of the inner peripheral surface 22 or the outer peripheral surface 11b of the ceramic substrate 11. is there. For this reason, for example, the inner peripheral surface 22 of the pipe 20 and at least a predetermined range in the front-rear direction sandwiching the welded portion W1 may be subjected to some degree of flexibility or deformability and resilience (elasticity) by plating or the like. ), And then compressing the metal layer with an interference fit of the pipe, it was thought that the generation of voids in the recess 22c generated during welding can be prevented. That is, it was inferred that by forming a metal layer and compressing it by an interference fit of the pipe, the recess 22c was filled with the compressed metal layer, thereby preventing the generation of voids. Therefore, actually, as an example, when a plating layer was formed on the inner peripheral surface 22 of the pipe 20 and tested, the effect was proved.

  The present invention has been made on the basis of such knowledge with respect to the above-described problems. The thermal expansion of a pipe welded to the seal member, and further, the seal member is applied to the pipe along the circumferential direction from the outer peripheral surface side. Welding prevents the deterioration of the airtightness between the outer peripheral surface of the pipe and the ceramic base caused by the depression of the inner peripheral surface of the pipe corresponding to the welded part, thereby improving the detection accuracy of the combustion pressure. It is an object of the present invention to provide a ceramic glow plug with a combustion pressure detection sensor that can be increased.

According to the first aspect of the present invention, there is provided a rod-shaped ceramic heater having a tip thereof protruding from the tip of a cylindrical housing between a housing inner peripheral surface and a heater outer peripheral surface. It is arranged so that it can be displaced in the axial direction while maintaining a gap,
A ceramic glow plug with a combustion pressure detection sensor comprising a sensor for detecting a combustion pressure based on a pressure or displacement generated when the ceramic heater is pushed backward from the tip by the combustion pressure,
The ceramic heater has a configuration including a rod-shaped ceramic base including a heating element, and a metal pipe externally fitted to the outer peripheral surface of the ceramic base by an interference fit,
Displacement of the heater is allowed in an annular gap between the inner peripheral surface of the housing near the front end and the outer peripheral surface of the pipe so as to block the inside and outside in an airtight manner near the front end of the housing. An annular or cylindrical seal member formed so as to be deformable is arranged on the pipe in an outer fitting shape, and is fitted to the outer circumferential surface of the ceramic base by an interference fit with respect to the outer circumferential surface of the pipe. In the ceramic glow plug with a combustion pressure detection sensor having a configuration welded along the circumferential direction from the outer peripheral surface side of the seal member itself,
Between the inner peripheral surface of the pipe and the outer peripheral surface of the ceramic base, a metal layer is formed in a predetermined range in the front-rear direction sandwiching at least a welded portion formed by welding the seal member. The metal layer is compressed in an interference fit state of the pipe.

  The invention according to claim 2 is the ceramic glow plug with a combustion pressure detection sensor according to claim 1, wherein the metal layer is formed on the inner peripheral surface of the pipe by plating.

As another reference invention different from the present invention, a rod-shaped ceramic heater with its tip protruding from its tip in a cylindrical housing includes an inner peripheral surface of the housing and an outer periphery of the heater. It is arranged so that it can be displaced in the axial direction with a gap between it and the surface,
A ceramic glow plug with a combustion pressure detection sensor comprising a sensor for detecting a combustion pressure based on a pressure or displacement generated when the ceramic heater is pushed backward from the tip by the combustion pressure,
The ceramic heater has a configuration including a rod-shaped ceramic base including a heating element, and a metal pipe externally fitted to the outer peripheral surface of the ceramic base,
Displacement of the heater is allowed in an annular gap between the inner peripheral surface of the housing near the front end and the outer peripheral surface of the pipe so as to block the inside and outside in an airtight manner near the front end of the housing. A ring-shaped or cylindrical seal member formed so as to be deformable is arranged on the pipe so as to be fitted on the outer circumference of the ceramic base, and the seal member is arranged on the outer circumference of the ceramic base. In the ceramic glow plug with a combustion pressure detection sensor having a configuration welded along the circumferential direction from the outer peripheral surface side of itself,
The pipe is externally fitted to the ceramic base with a gap fit, and a metal layer is formed in the gap by wetting and spreading the molten wax to solidify, and the pipe is attached to the ceramic base via the metal layer. Fixed,
The seal member may be welded within a range in a front-rear direction in which the metal layer on the inside of the outer peripheral surface of the pipe exists .

The invention according to claim 3, wherein the metal layer is a combustion pressure detecting ceramic glow plug with sensor according to any one of claims 1 or 2, characterized in that it consists of low hardness material than the pipe is there.
The invention according to claim 4 is the ceramic glow plug with a combustion pressure detection sensor according to any one of claims 1 to 3 , wherein the metal layer is formed over the entire length of the pipe. is there.
Invention of claim 5, wherein the metal layer, the including welding site, according to any one of claims 1-4, characterized in that it is formed over the rear of the predetermined range of the welding site This is a ceramic glow plug with a combustion pressure detection sensor.

  In the present invention, the metal layer is in a predetermined range in the front-rear direction between the inner peripheral surface of the pipe and the outer peripheral surface of the ceramic base and sandwiching (including) at least a welded portion formed by welding the seal member. This metal layer is compressed in an interference fit state of the pipe. Such a seal member is, for example, laser welded along the circumferential direction from the outer peripheral surface side to the outer peripheral surface of the pipe, for example, at the front end or the end close to the front end in the tight-fitting state of the pipe. It is. In this welding, the cooling and solidification of the molten metal on the pipe side starts from the inner peripheral surface side of the pipe and proceeds to the outer peripheral surface. For this reason, due to the shrinkage stress (welding strain) generated when the outer peripheral surface side cools and solidifies, the welded portion on the inner peripheral surface of the pipe is locally pulled outward in the radial direction compared to other portions. . In this case, if there is no compressed metal layer between the inner peripheral surface of the pipe and the outer peripheral surface of the ceramic base, as described in the background art, the inner peripheral surface of the pipe Of these, the part corresponding to the welded part is recessed outward in the radial direction with a very small depth within a predetermined range including the welded part. As a result, a minute gap is generated between the inner peripheral surface of the pipe and the outer peripheral surface of the ceramic substrate.

  However, in the present invention, there is a metal layer that is compressed in an interference fit state of the pipe between the outer peripheral surfaces. For this reason, if the inner peripheral surface of the pipe is deformed so as to be recessed with a minute depth of about 2 μm outward in the radial direction, the compressed metal layer is simultaneously compressed at the portion corresponding to the recess. Released from. That is, the metal layer that has been compressed tries to return to the original shape or the original thickness before compression at the same site in response to the formation of the recess, so that the recess is filled (no void is generated). Deform. That is, in the present invention, even if a concave portion is generated on the inner peripheral surface of the pipe during welding, the concave portion acts to be filled with the compressed metal layer. As described above, in the present invention, the gap between the outer peripheral surface and the outer peripheral surface is less than the conventional one in which there is no metal layer compressed in the tight-fitting state of the pipe. The effect of preventing the occurrence of the is obtained.

  Moreover, in this invention, the metal layer is formed in the predetermined range of the front-back direction which pinches | interposes a welding site | part. Therefore, there is a metal layer compressed by an interference fit of the pipe between the inner peripheral surface of the pipe and the outer peripheral surface of the ceramic base in a predetermined range in the front-rear direction across the recess (recess). For this reason, even if a pipe is thermally expanded and a gap is generated between the outer peripheral surface of the ceramic base on the tip side, the gap is generated more than if there is no metal layer being compressed. Can be delayed. Moreover, even if the gap is generated, since the gap in the concave portion on the inner peripheral surface of the pipe caused by welding is filled with the metal layer as in the conventional case, the generation of the void is suppressed, so that the combustion gas flows into the concave portion. The effect | action which prevents that penetrate | invades further is acquired. As a result, according to the present invention, since the airtightness between the inner peripheral surface of the pipe and the outer peripheral surface of the ceramic base can be improved as compared with the conventional case, the detection accuracy of the combustion pressure in the ceramic glow plug with the combustion pressure detection sensor is improved. Is prevented.

  In addition, the radial direction dimension (depth D1) of the recessed part resulting from the welding which generate | occur | produces on the internal peripheral surface of a pipe is about 1-3 micrometers, This is the surface roughness of the internal peripheral surface or the outer peripheral surface of a ceramic base | substrate. The level of roughness (Ra: about 0.5 μm) is almost the same as the unevenness, and is extremely small. Therefore, the thickness of the metal layer may be set such that when such a recess is generated, the recess can be filled by deformation or restoration by the metal layer itself. For this reason, this thickness is set according to physical properties such as hardness and elasticity of the metal layer. For example, the thickness of the metal layer is set at 0.1 μm.

  The metal layer is preferably formed over the entire length of a pipe that is externally fitted to the ceramic substrate. This is due to the following reason. Regarding the temperature distribution in the front-rear direction of the ceramic heater, the thermal expansion of the ceramic substrate itself can be ignored when the tip side is relatively hot. On the other hand, the pipe expands relatively remarkably greatly, and expands (increases in diameter) greatly toward the tip side where the temperature becomes high. However, there is a metal layer that is compressed between the inner peripheral surface of the pipe and the outer peripheral surface of the ceramic base, so that the metal layer is released from compression in the thermal expansion of the pipe, Deformation follows the thermal expansion of the pipe. That is, since the metal layer is between the outer peripheral surfaces of the both, it acts to eliminate the gap between them, but this action region is preferably longer from the viewpoint of airtightness retention.

  On the other hand, the pipe is thermally expanded so that the gap between the outer peripheral surfaces of the pipes becomes larger toward the tip side. In this case, even if the metal layer is on the entire length of the pipe, the effect of maintaining airtightness on the tip side is small depending on the thickness of the metal layer. On the other hand, the thermal expansion of the pipe is small because the rear end side is not as hot as the front end side. Further, the welding of the seal member is usually performed at a portion near the rear end of the pipe. Therefore, in the case where a metal layer is provided near the rear end of the pipe, it is possible to prevent the occurrence of voids existing between the inner and outer peripheral surfaces as in the prior art. This is because the airtightness between the outer peripheral surfaces is efficiently enhanced. That is, it is efficient or rational to form the metal layer over a predetermined range behind the welded part including the welded part. In particular, when an expensive metal such as Au or Ag is used for the metal layer, this is preferable from the viewpoint of cost.

In the present invention, the metal layer can be easily formed by plating. On the other hand, when the entire pipe is formed by electrolytic plating, it is usually formed on the outer peripheral surface. On the other hand, when there is a plating layer at the welded part, it may be a factor of poor bonding of the seal member due to the alloy layer generated during welding. Therefore, the plating layer is preferably formed selectively only on the inner surface of the pipe. The metal layer is preferably formed by plating, but may be formed by vapor deposition or thermal spraying. The metal layer may be a single layer or a plurality of layers. Furthermore, such a metal layer should just be formed in at least one of the internal peripheral surface before externally fitting a pipe, and the outer peripheral surface of a ceramic base | substrate. Further , in a reference invention different from the present invention, a high melting point molten solder such as Ni brazing or Cu brazing is poured into a gap between a pipe fitted in a ceramic base constituting a ceramic heater, and the pipe in the cooling and solidifying process. A metal layer can be formed at the same time as the interference fit by making an interference fit using heat shrinkage.

The ceramic heater that forms the ceramic glow plug with the combustion pressure detection sensor of the present invention is not limited to one in which a pipe is press-fitted into a ceramic base . Further, in the reference invention different from the present invention, as described above, the pipe is not fitted into the ceramic base by a gap fit, but is fitted by a gap fit, and a molten wax is poured into the gap to spread it. A ceramic heater can be configured by forming a metal layer by solidifying and fixing both of them through the metal layer . As described above, when a molten solder is used for forming the metal layer, the metal pipe expands relatively greatly in the heat of the molten wax or in a heat atmosphere for melting. In the subsequent cooling and solidification process, the expanded pipe is thermally contracted. Thereby, after the solidification, the metal layer (the brazing material layer) existing between the inner peripheral surface of the pipe and the outer peripheral surface of the ceramic base is compressed between the outer peripheral surfaces. Airtightness between them is maintained. As will be understood from this, the pipe is externally fitted with a gap fit to the ceramic base, and melted wax is spread in the gap to solidify it. The effect similar to the effect of the said invention is acquired by welding the sealing member which should be welded in the front-back direction range in which the brazing material layer exists in the inner peripheral surface of a pipe.

  That is, even when the brazing material layers are fixed to each other as described above, when the seal member is welded to the pipe, welding distortion (concave portion) is generated on the inner peripheral surface of the pipe. However, between the inner peripheral surface of the pipe and the outer peripheral surface of the ceramic substrate, there is a brazing material layer (hereinafter also referred to as a metal layer) in a compressed state between the peripheral surfaces. For this reason, the brazing material layer in the portion corresponding to the weld distortion (concave portion) of the inner peripheral surface of the pipe generated during the welding is released from the compressed state, and therefore follows the concave portion (dent). Swell and deform. As a result, as in the above-described invention, the brazing material fills the recess, so that no void is generated. Unlike plating, when forming a metal layer by wetting and spreading molten solder in the gaps between the peripheral surfaces, the thickness of the metal layer can be easily increased. Even if the concave portion becomes deep, it is easy to fill it. Therefore, it is suitable for the use of thin pipes that tend to generate large welding distortion.

As described above, in the reference invention different from the present invention , when the pipe is externally fitted to the ceramic base, it is not an interference fit but a gap fit state, and then the molten wax is poured into the gap. By spreading and solidifying, the two are fixed . In this case as well, the formation region (formation range) in the front-rear direction of the brazing material layer may be a predetermined range in the front-rear direction sandwiching (including) the welded portion, as described above. That is, the sealing member may be welded within a range in the front-rear direction where the brazing material layer inside the pipe exists. It is preferable that the brazing material layer exists over the entire length of the pipe in terms of airtightness, but it may be formed over a predetermined range behind the welded part including the welded part. As described above, the brazing filler may be selected from a high melting point brazing (alloy) mainly composed of Cu or Ni so as to withstand the temperature of the combustion gas.

  In the present invention, the metal layer is preferably made of a low hardness material (soft material) rather than a pipe. By doing so, the metal layer itself is compressed and crushed and easily deformed by the interference fit of the pipe, and airtightness retention between the outer peripheral surface of the ceramic base and the inner peripheral surface of the pipe is improved. For example, if the metal pipe is a 400 Hv SUS630 material, the metal layer is preferably made of a metal mainly composed of Au, Ag, Cu, or Ni.

The longitudinal cross-sectional view of the glow plug with a combustion pressure detection sensor which embodies this invention (1st Embodiment), and the enlarged view of the site | part near the front-end | tip of the housing. The enlarged view of the A section of FIG. The enlarged view which exaggerated and showed the B section of FIG. The figure explaining the assembly process of the glow plug of FIG. The enlarged view which exaggerated and showed the C section in FIG. The figure explaining the assembly process of the glow plug of FIG. The fracture | rupture longitudinal cross-sectional view of the conventional glow plug with a combustion pressure detection sensor, and the enlarged view of the site | part near the front-end | tip of the housing. The enlarged view of the A section of FIG. The enlarged view of the B section of FIG. The figure which exaggerated and showed the state which a pipe expands thermally and deform | transforms in the enlarged view of the B section of FIG.

  An embodiment (first embodiment) of a ceramic glow plug with a combustion pressure detection sensor embodying the present invention will be described with reference to FIGS. However, this configuration is the same as the conventional glow plug described in the background art except for the formation of the metal layer which is the main part of the present invention. Therefore, although the description of the overall configuration of the glow plug 101 is duplicated, the main part including the overall configuration will be described in detail below. The housing 40 constituting the glow plug 101 of the present example includes a housing main body 41 and a distal end side cylindrical housing 50 fixed to the distal end thereof. The glow plug 101 includes a ceramic heater 10 having a tip 10a (lower end in the figure, lower end) 10a protruding from the tip 53 of the tip-side cylindrical housing 50 inside the housing 40, and the inside of the housing 40. A shaft member (shaft member) 60 for applying voltage is arranged coaxially so as to extend rearward from the rear end of the heater 10, and combustion pressure detection provided in the inner space of the housing 40 at the rear end of the shaft member 60. It is comprised from the distortion | straining member 210 which comprises a sensor, and the distortion | strain sensor 220 attached to this.

  In this example, the housing 40 is made of, for example, SUS303, and includes a substantially cylindrical housing main body 41 and a front end side cylindrical housing 50 or the like that is coaxially fitted to the front end 42 side and welded. ing. Among these, the front end side housing 50 is provided with a flange-shaped front end annular portion 54a that protrudes inward along the circumferential direction so that the diameter of the inner peripheral surface 54 of the front end 53 is smaller than the rear side. This rear portion forms an inner peripheral surface (expanded annular inner peripheral surface) 55 whose diameter is larger than that of the inner peripheral surface 54 of the tip annular portion 54a. The distal end surface 54b of the distal end portion 53 of the distal end side tubular housing 50 is pressed against the seat surface Z of the plug hole to ensure a seal, and forms a tapered taper surface.

  The ceramic heater 10 includes a ceramic base 11 having a hemispherical shape with a convex tip 10a and a cylindrical shape, and a metal pipe 20 fitted on the ceramic base 11, and is disposed coaxially with the axis G of the housing 40. ing. A columnar (outside diameter of about 3 mm) ceramic base 11 constituting the heater 10 has a resistance heating element (for example, conductive ceramic) 12 embedded therein. The resistance heating element 12 is formed in a folded shape (U shape) having a folded portion at a portion near the tip 10a of the ceramic substrate 11. Further, on the side surface (outer peripheral surface) of the ceramic base 11 near the rear end of the heater 10, the energization electrode terminals 16 and 17 connected to the rear end portions of the legs 12 a and 12 b of the resistance heating element 12 are provided. Is exposed.

  The ceramic base 11 is provided with a metal pipe 20 (for example, a circular pipe having an outer diameter of 4 mm and a wall thickness of 0.45 mm, for example, made of SUS630) at an intermediate portion thereof. And it is fitted by interference fit. As a result, the inner peripheral surface 22 near the rear end of the pipe 20 is brought into pressure contact with and electrically connected to the grounding electrode terminal 16 positioned relatively on the front end side. However, on the inner peripheral surface 22 of the pipe 20, an Au plating layer 25 is formed as a metal layer with a predetermined thickness before the press-fitting.

  The metal layer is not limited to Au (gold) but may be Ag or Ni. Such an Au plating layer (hereinafter also simply referred to as a plating layer) 25 is formed on the entire inner peripheral surface 22 (the entire surface over the entire length) in this example. However, among the inner peripheral surface 22, the seal member 30 made of bellows described below sandwiches a welded part W <b> 1 welded to the outer peripheral surface 24 of the pipe 20, for example, a certain range in the front-rear direction shown in FIG. 2. It may be formed on the entire surface (entire in the circumferential direction) only at L1. The surface roughness of the outer peripheral surface 11b of the ceramic base 11 before press-fitting into the pipe 20 is Ra: about 0.5 μm, and the surface roughness of the inner peripheral surface 22 of the pipe 20 before press-fitting (before plating) is Ra: About 0.6 μm or less and Ry: 3 μm or less.

  On the other hand, a gap (annular gap) between the enlarged diameter inner peripheral surface 55 of the distal end side cylindrical housing 50 and the outer peripheral surface 24 of the metal pipe 20 that forms the outer peripheral surface of the heater 10 is formed in the pipe 20. A sealing member (hereinafter also referred to as a bellows) 30 made of a thin metal material (made of SUS316 and having a thickness of 0.07 mm) having a cylindrical shape of a bellows is disposed so as to be loosely fitted. That is, a metal bellows 30 loosely inserted in the housing 40 is externally fitted to the pipe 20 press-fitted into the ceramic base 11, and a predetermined portion near the tip 32 of the bellows 30 is Laser welding is performed on the outer peripheral surface 24 of the pipe 20 forming the heater 10 along the circumferential direction with a predetermined width (for example, 2 mm) to form a welded portion W1. In addition, the rear end portion 35 of the bellows 30 in which a predetermined portion near the tip 32 is welded to the outer peripheral surface of the pipe 20 in this way is the tip 42 of the housing body 41 and the portion near the rear end of the tip-side cylindrical housing 50. The inner peripheral surface of 57 is welded along the circumferential direction. In this example, the bellows 30 is made of a single plate, but may be formed of a plurality of thin plates.

  In this example, the gap between the inner peripheral surface 55 of the portion close to the tip of the housing 40 (tip-side cylindrical housing 50) and the outer peripheral surface of the heater 10 is caused by the bellows 30 thus fixed. In airtight state. That is, by the bellows 30 disposed in the housing 40, the inner space K2 and the space K connected to the outside on the front end side are shut off in an airtight manner. The bellows 30 itself can be easily deformed including the front-rear direction. As a result, when the heater 10 moves front-rearly with respect to the housing 40, the seal member 30 itself is deformed, and the front-rear direction is increased. It is formed to allow movement (displacement).

  Further, the bellows 30 forms a relay conduction portion between the electrode terminal 16 for grounding of the heater 10 and the housing 40 in addition to blocking and sealing (airtight holding) the space in this way. Further, the heater 10 is held in the housing 40 so as to be able to move forward and backward, and also serves as a heat transfer member that releases the heat of the heater 10 to the engine head H through the housing 40.

  In addition, the welding site | part W1 welded to the outer peripheral surface 24 of the pipe 20 which makes the heater 10 among the site | parts near the front-end | tip 32 of the bellows 30 is as having exaggerated and shown in FIG. That is, since the ceramic substrate 11 is press-fitted into the pipe 20 having the Au plating layer 25 formed on the inner peripheral surface 22, the Au plating layer 25 is compressed and thinner than in the free state. In addition, a concave portion 22c that is recessed by welding is generated at a portion corresponding to the welded portion W1 on the inner peripheral surface 22, and the compressed Au plating layer 25 enters the concave portion 22c. Details regarding this part will be described later.

  As described above, the shaft member 60 for applying voltage is arranged coaxially with the rear end of the heater 10. In other words, the heater 10 and the shaft member 60 are configured such that the metal pipe 19 is fitted and fixed to the both at the front end of the shaft member 60 and the rear end of the heater 10 by press-fitting to each other. Is additionally welded to connect the two. The electrode terminal (positive potential side terminal) 17 positioned relatively rearward of the heater 10 is electrically connected to the shaft member 60 while being electrically connected to the inner peripheral surface of the pipe 19. In other words, the connecting pipe 19 is responsible for ensuring electrical continuity as well as integration of the heater 10 and the shaft member 60.

  On the other hand, a screw 43 for fixing the glow plug 101 to the plug hole of the engine head H by a screwing method is formed on the outer peripheral surface of the housing body 41 with a predetermined length. Further, the rear end portion of the housing body 41 includes a diameter-expanded cylindrical portion 45 that is expanded to have a relatively large diameter. A sealing protective cylinder (cap) 70 is attached to the rear end of the diameter-expanded cylindrical portion 45 by welding or the like with a portion near the outer periphery of the sensor strain member 210 interposed therebetween. The strain member 210 has an annular shape (or a cylindrical shape) as a whole. For example, the strain member 210 is press-fitted into a portion near the rear end of the shaft member 60 via the insulating cylinder 65 at a portion near the inner periphery. It is fixed by. As a result, when the heater 10 is moved forward and backward by the combustion pressure, the strain member 210 is deformed corresponding to the movement of the shaft member 60 integrated therewith, and the strain sensor 220 attached to the strain member 210 causes the combustion pressure (electrical signal). ). A rubber member 69 for sealing is loaded in a small-diameter portion on the rear end side of the protective cylinder 70 for sealing at the rear end, and is fixed by caulking the protective cylinder 70 to a reduced diameter. Yes. Note that the terminal fitting 75 provided at the rear end of the shaft member 60 penetrates the rubber member 69 and protrudes backward.

  Now, the glow plug of this example having the above-described configuration is assembled, for example, as follows (see FIG. 4 and the like). That is, as shown on the right side of FIG. 4, the pipe 20 in which the Au plating layer 25 is formed on the inner peripheral surface 22 is press-fitted into the ceramic base 11 by external fitting. In the state of the heater side assembly 80 including the ceramic heater (assembly) 10 as a part assembled in this way, or the shaft member 60 fixed coaxially thereto, etc., a seal member made of bellows on the heater 10 30 is fitted and positioned. And in the front-end | tip part 32 of this seal member 30, this is welded to the outer peripheral surface 24 of the pipe 20 from the outer peripheral surface side by laser La, for example. FIG. 5 shows a portion corresponding to the portion B in FIG. 2 before welding (enlarged view in which the portion C in FIG. 4 is exaggerated).

  As shown in FIG. 4, the heater-side assembly 80 after welding of the seal member 30 is inserted into the front end side housing 50 from the front end side, and is inserted into the housing main body 41 from the rear end side. Then, the rear end 35 of the seal member 30 is sandwiched between the rear end and the front end of the front housing 50 and the housing main body 41 in a butting manner, and welded in the circumferential direction at the butting portion. In this way, the glow plug work in progress shown on the left side of FIG. 6 is obtained. Thereafter, the strain member 210 for sensors shown in the right diagram of FIG. 6 may be sequentially attached and assembled as described above.

  In the glow plug having the above-described configuration, the pipe 20 having the plating layer 25 formed on the inner peripheral surface 22 is externally fitted to the ceramic base 11 by press fitting, and the sealing member 30 is attached to the externally fitted pipe 20. Is welded in a circular manner from the outer peripheral surface side at the tip portion 32. During this process, when the pipe 20 is press-fitted into the ceramic substrate 11, the plating layer 25 formed on the inner peripheral surface 22 is compressed between the inner peripheral surface 22 and the outer peripheral surface 11 b of the ceramic substrate 11. Therefore, the thickness T1 of the plated layer 25 when compressed is thinner than that in the free state during plating (see FIG. 5).

  As shown in FIG. 5, in such a state, the seal member 30 is fitted to the outer peripheral surface 24 of the pipe 20 constituting the heater 10 and positioned, and a predetermined position in the front-rear direction of the distal end portion 32 is determined. Laser welding is performed in a circular manner from the outer peripheral surface side at the position (welding position). Therefore, the welded portion W1 is exaggerated in FIG. That is, the pipe 20 of the other party by this welding has an inner peripheral surface 22 at the portion corresponding to the welded portion W1 of the inner peripheral surface 22 by the outward pulling by cooling and solidification of the molten metal by welding. A concave portion 22c having a small depth is generated. However, as shown in FIG. 3, the plating layer 25 formed on the inner peripheral surface 22 of the pipe 20 before press-fitting at a portion corresponding to the recess 22 c is released from compression based on the press-fitting. , Causing deformation to return to its original thickness. That is, in the compressed plating layer 25, the portion corresponding to the concave portion 22c is deformed so as to swell and fill the concave portion 22c. In this example, the concave portion 22c is generated, but there is a gap Is almost never generated. That is, it is considered that the plated layer 25 forming the metal layer is restored as if it was compressed rubber at a minute portion called the concave portion 22c to fill the concave portion 22c.

  When the glow plug 101 of this example having such a metal layer 25 is screwed into a screw hole in the plug hole of the engine head H, the glow plug 101 is used for promoting the start of the engine and detecting the combustion pressure after the start. Has the following effects. That is, in this process of use, the heaters 10 and the pipes 20, particularly the portions near their tips, become extremely hot. At this time, the thermal expansion of the ceramic substrate 11 constituting the ceramic heater 10 can be ignored, but since the pipe 20 is made of metal, even if it is initially in an interference fit state, the thermal expansion is relatively large. For this reason, as the thermal expansion increases, the internal stress of the pipe 20 itself that has occurred in the interference fit decreases (the interference fit becomes weak).

  On the other hand, in the glow plug 101 of this example, the metal layer 25 is formed on the entire inner peripheral surface 22 of the pipe 20, and the inner peripheral surface 22 of the pipe 20 and the ceramic base body 11 in the front-rear direction across the recess 22 c. The outer peripheral surface 11b is compressed by an interference fit by the pipe 20. For this reason, even if the thermal expansion of the pipe 20 increases and a gap is generated between the outer peripheral surface 11b of the ceramic base body 11 on the tip side, there is no metal layer 25 that is compressed. It is possible to delay the generation of the gap rather than the thing. Even if the gap is generated, the gap in the concave portion 22c of the inner peripheral surface 22 of the pipe 20 caused by welding is filled with the metal layer 25 as in the prior art. Therefore, the effect | action which prevents that combustion gas penetrate | invades into the back from the recessed part 22c by that much is acquired. As a result, in the glow plug 101 of the present example, the metal pipe 20 is directly fitted into the ceramic base 11 by press fitting or the like, as in the conventional case, and in this state, the seal member 30 is placed on the outer periphery of the pipe 20. Compared to the structure welded from the surface side, the airtightness between the inner peripheral surface 22 of the pipe 20 and the outer peripheral surface 11b of the ceramic base 11 can be enhanced. This prevents a decrease in combustion pressure detection accuracy.

  Next, in order to confirm the effect in this example, a glow plug sample is made, the front end side of the heater is heated so that the rear end portion of the pipe 20 becomes 450 ° C., and under that, a gas pressure of 5 MPa is set to 10 MPa. A leak test was performed over a period of minutes, and the presence or absence of a leak was measured. However, the sample used in this example is silicon nitride (outer diameter: 3.0 mm) as the ceramic substrate forming the heater, and the pipe to be pressed into this is made of SUS630 (hardness HV400), with a thickness of 0.45 mm, length, 20 mm. The designed inner diameter of the pipe is 2.93 mm, and the press-fitting allowance is 70 μm in diameter. In the sample forming the example (1-7), the plating layer forming the metal layer is Au plating and has a thickness of 0.2 to 0.65 μm. The comparative example has no plating. The leak test is performed after the heater is energized or the rear end is heated to 450 ° C. using a heating furnace or the like. The results are as shown in Table 1.

  As shown in Table 1, in the example in which the plated layer was formed on the inner peripheral surface of the pipe, no leakage occurred in most samples. Moreover, when the thickness of the plating layer was 0.1 μm, leakage was observed, but it was still confirmed that the amount of leakage was much smaller than that of the comparative example in which the plating layer was not formed. . These facts are for the purpose of demonstrating the effects of the present invention described above. As can be understood from this test, it is understood that a thicker plating layer is preferable.

  In the above example, the case where Au plating is formed on the inner peripheral surface of the pipe on the metal layer is exemplified, but Ag plating or Ni plating may be used. Further, a plating layer may be formed on the outer peripheral surface of the ceramic substrate by electroless plating. As described above, although the thickness of the plating layer depends on the inner peripheral surface of the pipe and the surface roughness of the outer peripheral surface of the ceramic base, the effect of the present invention is that the concave portion generated on the inner peripheral surface of the pipe during welding is reduced. Based on filling with a compressed metal layer. And the depth of this recessed part is the level of the unevenness | corrugation in the surface roughness of the outer peripheral surface of a ceramic base | substrate, and the internal peripheral surface of a pipe. For this reason, if the surface roughness of the outer peripheral surface of the ceramic substrate is Ra 0.2 μm and the surface roughness Ra of the inner peripheral surface of the pipe is 0.15 μm, the total of these is considered to be 0.35 μm or more. Further, as described above, the metal layer is not limited to the plating layer, but the metal layer is softer (lower than the metal forming the pipe that is externally fitted to the ceramic substrate) by any forming means. Hardness), that is, it is preferable to be easily deformed.

  In addition, the region (range) in the front-rear direction of the metal layer to be formed is preferably as long as possible in the front-rear direction across the portion (welded portion) of the pipe to which the seal member is welded. However, as described above, when an expensive metal (noble metal) such as Au or Ag is used, a predetermined range in the front-rear direction sandwiching the welded portion may be used. In this case, as described above, it is preferable to set the predetermined range behind the welded portion. In the above example, the case where the welding is laser welding has been described. However, the present invention is also applied to a case where a concave portion due to welding is generated on the inner peripheral surface of the pipe even in the case of electron beam welding or other welding. it can.

In the above example, the ceramic heater 10 to which the seal member 30 is welded is press-fitted into the pipe 20 in which the metal layer (plating layer 25) is formed on the inner peripheral surface 22 to make an interference fit. It was assumed formed by maintaining a hermetic seal between the inner and the peripheral surface 22 and the outer circumferential surface 11b of the base 11 and cut by the embodied child transgression in the different reference iNVENTION in the following, as the present invention . In the above example, the inner diameter of the pipe 20 is set larger than the outer diameter of the ceramic substrate 11 by about 0.3 mm, for example. The pipe 20 is externally fitted to the ceramic base 11 with a gap fit and positioned in the front-rear direction. Under this positioning state, molten wax (waxing material) is poured into the gap by capillary action or the like, and the molten wax is spread between the outer peripheral surfaces 22 and 11b. Thereafter, by cooling and solidifying, a brazing material layer is formed between the outer peripheral surfaces 22 and 11b, and both are integrated. That is, by using the ceramic heater 10 in which both are brazed and the airtightness between the outer peripheral surfaces is maintained, the seal member 30 can be welded to the pipe 20 as described above. The same effect can be obtained. Even when the brazing material layer is formed between the inner peripheral surface 22 of the pipe 20 and the outer peripheral surface 11b of the base body 11 as a metal layer, the shape shown in FIG. Will be the same.

  In the case of forming the brazing material layer, as described above, the pipe 20 that has undergone relatively large thermal expansion due to the flow of the molten wax contracts during the cooling and solidification process of the molten wax. The brazing filler metal layer (metal layer) that has spread out is compressed between the inner peripheral surface 22 of the pipe 20 and the outer peripheral surface 11b of the ceramic substrate 11 after solidification. That is, since the pipe 20 is contracted to the ceramic base 11 through the compressed brazing material layer, the brazing material layer corresponds to the plating layer 25 in FIG. . Therefore, when the sealing member 30 is welded within the front-rear direction of the outer peripheral surface 21 of the pipe 20 where the inner brazing material layer is present, the inner peripheral surface 22 is welded (recessed) 22c. However, as in the case of the plating layer, the compressed brazing material layer swells and enters into the recess. That is, since the brazing material layer fills the recess 22c in place of the plating layer 25 in the above example, generation of voids is prevented as in the above example, and the same effect is obtained. In general, the brazing material layer is bonded (brazed) to the inner peripheral surface 22 of the pipe 20, while being pressed (closely adhered) to the outer peripheral surface 11 b of the ceramic base 11. It is thought that it is not brazed). For this reason, the brazing material layer is on the side pressed against the outer peripheral surface 11b of the ceramic base 11 (the interface side with the outer peripheral surface 11b) with the occurrence of the weld distortion (concave portion) 22c of the inner peripheral surface 22. It can also be said that the brazing material layer itself swells and fills in the welding strain (concave portion) that is to occur in the layer itself.

  When the brazing material layer is used as described above, unlike the plating layer, the brazing material layer, that is, the metal layer can be easily formed thick, so that the welding distortion (concave portion) becomes deeper. Even you can fill it. Therefore, it is possible to obtain an effect that it is possible to cope with the use of a thin pipe which tends to generate a large welding distortion. Further, since the airtightness can be maintained even when the surface roughness is low, the surface treatment of both members becomes easy. In the case of using the brazing material layer in this way, from the viewpoint of preventing the generation of the voids, the formation region (formation range) in the front-rear direction of the brazing material layer is the welded portion of the seal member as described above. It can be said that a predetermined range in the front-rear direction (including) is sufficient, but it is preferable to form a brazing material layer over the entire length of the pipe in order to improve airtightness. However, it is not limited to this, as in the case of forming a plating layer.

  The glow plug of the present invention is not limited to the above-described one, and can be embodied with appropriate modifications. For example, in the above example, the seal member is a bellows-like bellows, but a simple diaphragm (thin film) shape in the shape of an annular plate, a membrane structure, or other annular or cylindrical film body, etc. It may be of an appropriate shape and structure. This is because, when this is welded and fixed to a pipe that is externally fitted to the ceramic base, a concave portion is generated on the inner peripheral surface of the pipe as described above. Further, in the glow plug described above, the housing includes a housing main body and a tip side housing that is coaxially butted and fixed to the tip of the housing. However, the structure of the housing forming the glow plug is limited to this. It can be embodied even if it is not a thing but what consists of one cylinder (cylindrical metal shell).

  Further, the sensor (detection means) in the glow plug with a combustion pressure detection sensor as in the present invention deforms the strain member by the forward / backward movement generated when the heater is pushed backward from the tip by the combustion pressure in the above example. A strain sensor (strain gauge) that performs the detection is exemplified, but the present invention is not limited to this. Various sensors (sensor elements, such as those using a semiconductor strain gauge such as a semiconductor element provided with a piezoresistor, or detecting a voltage change generated by compressing a piezoelectric element with combustion pressure) ) Method can be widely applied to glow plugs with combustion pressure detection sensors.

DESCRIPTION OF SYMBOLS 10 Ceramic heater 10a The tip of a heater 11 Ceramic base | substrate 11b The outer peripheral surface of a ceramic base | substrate 20 The metal pipe formed by interference fitting on the outer peripheral surface of a ceramic base | substrate 22 The outer peripheral surface of a pipe 24 The outer peripheral surface of a pipe 25 Metal layer 30 Seal MEMBER 40 HOUSING 53 HOUSING TIP 55 HOUSING TIP LOCATION INNER PART 101 CERAMIC GLOW PLUG WITH COMBUSTION PRESSURE DETECTION SENSOR 220 SENSOR G AXIS W1 WELDING SITE

Claims (5)

A rod-shaped ceramic heater with its tip protruding from its tip inside a cylindrical housing is displaced in the axial direction with a gap between the inner peripheral surface of the housing and the outer peripheral surface of the heater Are arranged so that
A ceramic glow plug with a combustion pressure detection sensor comprising a sensor for detecting a combustion pressure based on a pressure or displacement generated when the ceramic heater is pushed backward from the tip by the combustion pressure,
The ceramic heater has a configuration including a rod-shaped ceramic base including a heating element, and a metal pipe externally fitted to the outer peripheral surface of the ceramic base by an interference fit,
Displacement of the heater is allowed in an annular gap between the inner peripheral surface of the housing near the front end and the outer peripheral surface of the pipe so as to block the inside and outside in an airtight manner near the front end of the housing. An annular or cylindrical seal member formed so as to be deformable is arranged on the pipe in an outer fitting shape, and is fitted to the outer circumferential surface of the ceramic base by an interference fit with respect to the outer circumferential surface of the pipe. In the ceramic glow plug with a combustion pressure detection sensor having a configuration welded along the circumferential direction from the outer peripheral surface side of the seal member itself,
Between the inner peripheral surface of the pipe and the outer peripheral surface of the ceramic base, a metal layer is formed in a predetermined range in the front-rear direction sandwiching at least a welded portion formed by welding the seal member. A ceramic glow plug with a combustion pressure detection sensor, wherein the metal layer is compressed in an interference fit state of the pipe.   The ceramic glow plug with a combustion pressure detection sensor according to claim 1, wherein the metal layer is formed on the inner peripheral surface of the pipe by plating. The metal layer is, the combustion pressure detecting ceramic glow plug with sensor according to any one of claims 1 or 2, characterized in that than the pipe made of a low hardness material. The ceramic glow plug with a combustion pressure detection sensor according to any one of claims 1 to 3, wherein the metal layer is formed over the entire length of the pipe. The ceramic glow plug with a combustion pressure detection sensor according to any one of claims 1 to 4, wherein the metal layer is formed over a predetermined range behind the welded part including the welded part. .

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