JP2014020592A - Ceramic glow plug with combustion pressure detection sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ceramic glow plug with a combustion pressure detection sensor in which a heater is composed of a ceramic substrate and a metal pipe press-fitted to and fitted around the ceramic substrate and a seal member arranged in an annular space between an inner peripheral surface at a tip end of a housing and an outer peripheral surface of the heater is welded to the pipe without inhibiting deformation of the seal member, in order to prevent a combustion gas from intruding into a deeper area by passing through a space between an inner circumferential surface of the pipe and an outer circumferential surface of the ceramic substrate.SOLUTION: A different-diameter pipe 20 having an annular thick wall part 24 having a thick wall in a portion located in an annular space K2 is used in a part of a pipe in a longitudinal direction. A seal member 60 is welded to an outer peripheral surface of a thin wall pipe part 21 having a thin wall in a tip end side of the annular thick wall part 24. A ceramic substrate 11 is fastened strongly owing to an arrangement of the annular thick wall part 24 and therefore airtightness is enhanced. Deformation of the seal member is not inhibited because the seal member is welded to the thin wall pipe part 21.

Description

  The present invention relates to a ceramic glow plug with a combustion pressure detection sensor provided with a sensor for detecting (detecting) combustion pressure in addition to promoting ignition in an engine combustion chamber.

  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. 10 is a broken vertical sectional view showing a simplified cross-sectional structure of a glow plug 901 of the same type. In this figure, a rod-shaped (circular shaft-shaped) ceramic heater 10 that generates heat when energized is placed in a cylindrical housing 110, and its own 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 of the housing 110. In the present application, with respect to the glow plug, or its component parts, component parts, and portions, the front end refers to the lower end thereof in FIG. 10, and the rear end refers to the opposite end (upper end). A two-dot chain line in FIG. 10 indicates the vicinity of the combustion chamber in the plug hole of the engine head H.

  In such a glow plug 901, a ceramic heater (hereinafter also simply referred to as a heater) 10 is about several tens of μm in the axis (axis) G direction (front-rear direction) in the housing 110 in order to detect the combustion pressure. Although it is minute, it is arranged so that it can be displaced. For this reason, the heater 10 is disposed with a gap (annular gap) between itself and the inner peripheral surface of the housing 110. An energizing shaft member 25 is provided behind the heater 10 via a connecting short tube (circular tube) 19 disposed coaxially and in a butted manner. Thus, the displacement or pressure generated when the heater 10 is pushed rearward from the tip 10a by the combustion pressure is detected (measured) by the sensor (strain gauge or piezoelectric element) to detect the combustion pressure. ing. For example, in the same figure, the displacement or pressure is applied to, for example, a strain member 210 provided behind the shaft member 25, and the strain amount is detected by a strain gauge 220 attached thereto. The combustion pressure is detected.

  By the way, in this glow plug 901, the high-temperature and high-pressure combustion gas rushes toward the front end of the housing 110 as indicated by the broken line arrow below the plug hole in FIG. It is necessary to prevent the rearward entry of the housing 110 through the annular gap (gap) K between the inner peripheral surface of the part and the outer peripheral surface of the heater 10 (to ensure a seal). For this reason, the glow plug 901 shown in the figure includes a metal seal member 60 that prevents intrusion of combustion gas in an annular gap formed inside the distal end portion (front end side housing 131) of the housing 110. . Since the seal member 60 needs to allow displacement of the heater 10 in the axis G direction with respect to the housing 110, the seal member 60 is made of a sufficiently flexible metal such as a metal thin film (membrane) that can be easily deformed. It is common to make it annular or cylindrical like a bellows or diaphragm (annular diaphragm) made of a thin material (for example, made of stainless steel or nickel alloy). Incidentally, the film thickness is about 0.1 to 0.2 mm.

  The sealing member 60 in the figure is a bellows whose rear end side is a large diameter portion and whose front end side is a small diameter portion. Such a seal member 60 is welded along the circumferential direction, with the rear end side on the inner peripheral surface of the housing 110 and the front end side on the outer peripheral surface of the ceramic heater 10. By disposing the seal member 60 in this manner, the annular gap K in the housing 110 is shut off in an airtight manner, and a seal is formed between the inner space K2 and the outside on the tip side (outside of the glow plug). (Airtight) is maintained. Since the ceramic heater 10 is a ceramic heater in which a heating element 12 is formed in a rod-shaped ceramic base 11, a metal sealing member 60 cannot be directly welded to the outer peripheral surface 11b. . 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 by press fitting, and the outer periphery of the pipe 20 is close to the end of the seal member 60. The part is laser-welded, for example, along the circumferential direction at a predetermined position from the outside. An electrode terminal (grounding electrode) 16 for energizing the heating element 12 is pressed against the inner peripheral surface 22 of the pipe 20 and is electrically connected to the housing 110 via a welded seal member 60. ing. The other electrode 17 is connected to the shaft member 25 via the connecting short tube 19 described above.

  On the other hand, both the outer peripheral surface 11b of the ceramic substrate 11 and the inner peripheral surface 22 of the pipe 20 are finished to a high degree of surface roughness, for example, Ra, of 0.15 to 0.2 μm or less. Thereby, the airtight maintenance between the inner peripheral surface 22 of the pipe 20 to which the seal member 60 is welded and the outer peripheral surface 11b of the ceramic base 11 is achieved.

JP 2009-520941 A JP 2011-089688 A

  However, in the above-described ceramic glow plug with a combustion pressure detection sensor, the pressure detection accuracy is sometimes lowered. This is because the combustion gas (GAS) enters from the front end side to the rear through the space between the outer peripheral surface 11b of the ceramic base 11 forming the heater 10 and the inner peripheral surface 22 of the pipe 20 fitted on the outer surface. Is due to That is, this gas is caused to enter the space K2 in the back (inside) of the glow plug partitioned by the seal member 60 as shown by the broken line arrow in FIG.

  In this type of glow plug 901, the combustion pressure (combustion gas pressure) is received together with the tip 10a of the heater 10 on the surface of the seal member 60 facing the combustion chamber side, whereby the heater 10 is pressed backward. The pressure or displacement due to this is detected (measured) by a sensor (strain gauge or piezoelectric element) to detect the combustion pressure. For this reason, when combustion gas (hereinafter also simply referred to as gas) enters the inner space K2 partitioned by the seal member 60, the space K2 becomes high temperature and high pressure, so that noise is generated in the sensor. In addition to being affected, a reverse pressure is applied to the seal member 60, which causes a decrease in pressure and displacement that push the heater 10 backward. 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 substrate 11 means that a gas layer is formed in the gap. For this reason, even if it does not enter the inner space K2, the heat of the ceramic heater 10 is not easily radiated to the housing 110 and the cylinder head H through the pipe 20 and the seal member 60. As a result, there is a problem that the temperature of the glow plug 901 itself is increased.

  By the way, the cause of the invasion of the gas is considered as follows. When the seal member 60 is welded to the pipe 20, the pipe 20 which is a thin-walled pipe generates a weld distortion (dent) although a minute amount on the inner peripheral surface of the part corresponding to the welded part. Moreover, due to the difference in thermal expansion between the ceramic base 11 constituting the heater 10 and the metal pipe 20 press-fitted into the ceramic base 11, the pipe 20 expands relatively greatly in a high-temperature, high-pressure gas environment. When such thermal expansion occurs, the clamping force of the ceramic base 11 by the pipe 20 is greatly reduced, so that gas easily enters between the inner peripheral surface of the pipe 20 and the outer peripheral surface of the ceramic base 11. The presence of the above-described welding distortion (dent) is considered to form a gas reservoir in the use of a thin-walled pipe with a large decrease in tightening force, and is a factor that promotes gas intrusion.

  It can be said that such a problem itself can be dealt with by making the pipe 20 press-fitted into the ceramic substrate 11 into a thick pipe having a sufficiently large thickness. This is because, by sufficiently increasing the thickness of the pipe 20, the ceramic substrate 11 can be strongly tightened (with a high tightening pressure) after the press-fitting even with the same tightening allowance (press-fit allowance). . In addition, by increasing the thickness, it is possible to reduce the occurrence of welding distortion (dents) on the inner peripheral surface.

  However, the annular gap between the inner peripheral surface near the tip of the housing 110 and the outer peripheral surface of the pipe 20 forming the heater 10 is the diameter of the housing (or the screw diameter of the plug hole) and the outer diameter of the ceramic base 11. Originally, only narrow dimensions can be secured based on the dimensional constraints. Further, the seal member 60 welded to the pipe 20 needs to be easily deformable in view of its function. Therefore, for this purpose, the radial dimension (one-side dimension) of the seal member 60 is required. Must be as large as possible even within the narrow gap. On the other hand, if a thick pipe having a sufficient thickness is adopted, the dimension in the radial direction needs to be reduced. In particular, a glow plug with a structure in which the seal member cannot be used with a long front and rear length, such as a bellows, and a ring metal thin film (membrane) shape must be used. Also from the viewpoint of ensuring, it is necessary to sufficiently secure the radial dimension of the seal member. Therefore, conventionally, it is difficult to adopt a thick pipe as a pipe to which a seal member is welded. Therefore, the pipe 20 has a thickness of about 0.3 to 0.5 mm. In other words, so-called thin-walled pipes are used, causing the above problems.

  The present invention has been made in view of the above problems in a ceramic glow plug with a combustion pressure detection sensor, and its purpose is to strongly tighten the inner peripheral surface of a pipe and the outer peripheral surface of a ceramic base, which constitute a ceramic heater. This ensures high airtightness between the inner peripheral surface of the pipe and the outer peripheral surface of the ceramic base, and does not impair the ease of deformation of the seal member. It is to provide the same glow plug lug that can enhance.

According to the first aspect of the present invention, there is provided a rod-shaped ceramic heater in which a tip is projected from a tip of a cylindrical housing, and an inner peripheral surface of a portion near the tip of the housing and an outer periphery of the ceramic heater. It is arranged so that it can be displaced in the axial direction while holding an annular gap with 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 therein, and a metal pipe having an inner peripheral surface fitted in a press-contact state on the outer peripheral surface of the ceramic base. ,
In the annular gap, an annular or cylindrical metal seal member formed so as to allow the ceramic heater to be displaced in an arrangement that shuts the inside and outside of the housing in an airtight manner is provided on the pipe. In the ceramic glow plug with a combustion pressure detection sensor that is fitted and welded along the circumferential direction to the outer peripheral surface of the pipe,
The pipe has a different diameter in a part located in the front-rear direction, an annular thick part having a larger outer diameter than the other part in the part located in the annular gap and continuously thick in the circumferential direction. It is considered as a pipe,
The sealing member is welded to an outer peripheral surface of a thin pipe portion having a relatively small thickness, not the annular thick portion, of the different diameter pipe.

According to a second aspect of the present invention, the different diameter pipe includes the thin pipe portion on a distal end side of the annular thick portion, and the seal member is welded to an outer peripheral surface of the thin pipe portion. The ceramic glow plug with a combustion pressure detection sensor according to claim 1.
The invention according to claim 3 is provided with a tapered portion whose outer diameter is reduced toward the tip of the annular thick portion,
In claim 1, the seal member is welded to an outer peripheral surface of a thin pipe portion having a relatively small thickness, not the annular thick portion, of the different diameter pipes.
The ceramic glow plug with a combustion pressure detection sensor, wherein the seal member is welded to an outer peripheral surface of the tapered portion having a relatively thin thickness in the annular thick portion.

According to a fourth aspect of the present invention, the seal member is provided with a taper tube portion that is taper-fitted to the taper portion of the annular thick portion, and the seal member includes the taper tube portion and the taper portion. The ceramic glow plug with a combustion pressure detection sensor according to claim 3, wherein the ceramic glow plug is welded to the outer peripheral surface of the tapered portion at the tapered cylindrical portion.
The invention according to claim 5 is the invention according to any one of claims 1 to 4, wherein the annular thick part is provided at a rear end or a rear end portion of the different diameter pipe. This is a ceramic glow plug with a combustion pressure detection sensor.

In the invention according to claim 6, a plurality of electrode terminals for energizing the heating element provided in the outer surface of the ceramic base are exposed,
The different-diameter pipe is externally fitted to the ceramic base in such a manner that an inner peripheral surface of a portion corresponding to the annular thick portion of the inner peripheral surface is in pressure contact with one of the electrode terminals. It is a ceramic glow plug with a combustion pressure detection sensor of any one of Claims 1-5 characterized by the above-mentioned.

  In the present invention according to claim 1, the pipe press-fitted into the ceramic base is a different diameter pipe having the annular thick part, and the seal member is welded to the outer peripheral surface of the thin pipe part. Yes. For this reason, even if it is unavoidable to generate weld distortion in the thin pipe portion that is the weld location, the annular thick wall portion that is not the thin pipe portion avoids the occurrence of weld distortion that occurs in the thin pipe portion. It is done. And even if the annular thick wall portion is externally fitted to the ceramic base by press-fitting with the same tightening allowance (press fit allowance) as the thin pipe portion, the thickness is larger than the thin pipe portion. On the other hand, it is externally fitted with a strong tightening force (contact pressure in pressure welding). For this reason, even if the ceramic heater is exposed to a high-temperature, high-pressure gas, the annular thick portion of the ceramic heater is between the inner peripheral surface and the outer peripheral surface of the ceramic substrate as compared with the same other parts. Occurrence of looseness is prevented. Thereby, in this invention, the effect | action thru | or the effect which prevent the fall of the airtightness between the inner peripheral surface of a different diameter pipe and the outer peripheral surface of a ceramic base | substrate are largely acquired by this annular thick part. In other words, in the present invention, the effect of preventing the combustion gas from entering the back of the glow plug is enhanced by the presence of the annular thick portion, so that the detection accuracy can be prevented from lowering.

  Moreover, even if the annular thick portion is present, since the sealing member is welded in the thin pipe portion of the different diameter pipe, the radial dimension of the portion such as the annular metal thin film required for the sealing member is required. Can be secured in the same manner as in the prior art. For this reason, it does not impair the ease of deformation of the seal member itself and the forward / rearward movement of the heater, which are required when the heater moves forward / backward under the combustion gas pressure.

  As described above, according to the glow plug according to the present invention, the different diameter pipe can be strongly tightened with respect to the ceramic base at the annular thick portion. The airtightness in the front-rear direction between the outer peripheral surface of the base body can be made high. For this reason, since it becomes difficult for gas to enter between the outer peripheral surfaces, the heat of the heater can be easily transmitted to the housing and the cylinder head via the seal member.

  The sealing member may be welded to the different diameter pipe in the present invention either before or after the annular thick portion. Accordingly, the thin pipe portion for welding the seal member may be a rear end side (rear side) of the annular thick portion or a front end side (front side) portion. However, as described in claim 2, by setting the tip side, the annular thick-walled portion becomes a structural wall in the annular gap in the glow plug, and on the back side thereof. Will be located. That is, the annular thick wall portion is covered by the seal member that receives a direct hit of the combustion gas on the combustion chamber side of the engine, and thus is less susceptible to thermal influence. As a result, it is possible to efficiently prevent a decrease in strong clamping force (contact pressure in pressure contact) with respect to the ceramic base in the annular thick wall portion or prevent a decrease in airtightness. Moreover, since the heat of the heater can also be transferred (heated) through a short heat transfer path toward the housing via a seal member welded to the thin pipe portion located at the tip of the annular thick portion, The annular thick part is less susceptible to thermal effects.

  In the present invention, the annular thick portion has an end surface (annular end surface) that is a plane perpendicular to the axis of the pipe at a boundary with another portion (thin pipe portion) in a part in the front-rear direction of the pipe. The outer diameter may be formed so as to change abruptly in a stepped manner, or may be changed gently. And like invention of Claim 3, the said cyclic | annular thick part shall be equipped with the taper site | part by which an outer diameter reduces toward the front, The said sealing member WHEREIN: Instead of being welded to the outer peripheral surface of the thin-walled pipe portion, which is not the annular thick-walled portion of the different-diameter pipe, the seal member is included in the annular thick-walled portion. It is good also as being welded to the outer peripheral surface of the said taper site | part with comparatively thin thickness. That is, in the present invention, the annular thick portion may have an appropriate cross-sectional shape (a cross-sectional shape when cut along a plane passing through the axis of the pipe). In the case where the tapered member is provided with a tapered part whose diameter is reduced, the sealing member is welded to the outer peripheral surface of the tapered part, which is relatively thin among the annular thick part. Also good. In this case, in order to reduce the influence of welding distortion, the welded portion is preferably a portion having an outer diameter as small as possible among the tapered portions. In the present application, the “taper” is not limited to the one in which the outer diameter is linearly reduced (changes), but includes one in which the diameter is reduced in a curved shape.

  In the invention of claim 3, as in the invention of claim 4, the seal member is provided with a tapered cylindrical portion that is taper-fitted to the tapered portion of the annular thick portion, It is preferable that the sealing member is configured such that the tapered tubular portion is taper-fitted to the tapered portion and welded to the outer peripheral surface of the tapered portion in the tapered tubular portion. This is because welding such as laser welding becomes easy. The reason will be described later. Further, in the present invention, the annular thick part may be provided at any of the front and rear positions in the different diameter pipe, but as in the invention according to claim 5, the rear end or the rear end of the different diameter pipe is closer. It is good to provide in the part. That is, in the same thickness pipe (thin wall pipe), it is preferable that the annular thick portion exists at the rear end or the rear end portion. In the configuration in which the inner peripheral surface of the different-diameter pipe is in pressure contact with one of the electrode terminals (for example, the ground-side electrode terminal) to ensure electrical connection therewith, as in the invention according to claim 6 In addition, it is preferable that the inner peripheral surface of the portion corresponding to the annular thick portion is disposed so as to be in pressure contact with the electrode terminal. As a result, the surface pressure in the pressure contact can be increased, and as a result, the reliability of the electrical connection can be increased. In the setting of the position of the electrode terminal, the invention according to claim 5 supports such a setting. It is because it is easy to do.

  In particular, when the annular thick part is provided near the rear end, a part of the small diameter part that forms the thin pipe part is formed continuously in the rear part. For this reason, when fixing the tip (cylindrical portion) of the pressure transmitting shaft member that transmits the pressure or displacement of the heater using the small diameter portion, the tip of the shaft member is formed with an annular thickness. Since it can be brought into contact with the rear end-facing surface (rear end surface) of the meat part, positioning in the front-rear direction can be performed. That is, in the case where the annular thick part is provided near the rear end, when the shaft member for pressure transmission is attached in this manner, positioning in the axial direction is facilitated. This is because it becomes easy. In the present invention, the different-diameter pipe is basically a straight circular pipe (a circular pipe having the same inner and outer diameters), and a large-diameter portion is provided concentrically at a part thereof. Is the principle. However, the different-diameter pipe according to the present invention is based on a tapered pipe having a gentle taper of, for example, 1/200 to 1/400 and having substantially the same wall thickness, and forms an “annular wall portion”. Also included.

1 is a partially broken sectional view of a glow plug with a combustion pressure detection sensor embodying the present invention (first embodiment), and an enlarged view of an essential part thereof. The enlarged view of the part containing a ceramic heater and a sealing member in FIG. 1, and the further enlarged view of the principal part. The enlarged view of the P1 part of FIG. The figure explaining the assembly process of the ceramic heater assembly | attachment body explaining the assembly example of the glow plug of FIG. It is an exploded view explaining the assembly example of the glow plug of FIG. 1, Comprising: The exploded view before attaching a heater assembly etc. to a housing, and the enlarged view of the principal part. It is an exploded view explaining the assembly example of the glow plug of FIG. 1, Comprising: Explanatory drawing of the assembly | attachment process example from the state of FIG. It is a figure explaining the modification of the glow plug with a combustion pressure detection sensor of FIG. 1, Comprising: The figure corresponded in the enlarged view of the A1 part of FIG. FIG. 8 is a diagram for explaining another example (second embodiment) of the glow plug of FIG. 1 and corresponding to an enlarged view of a portion A1 of FIG. The figure explaining the modification which deform | transformed the different diameter pipe and the sealing member in FIG. The fracture | rupture longitudinal cross-sectional view which shows an example of the conventional ceramic glow plug with a combustion pressure detection sensor, and the enlarged view of the part containing the sealing member.

  A glow plug with a combustion pressure detection sensor of an embodiment (first embodiment) embodying the present invention will be described in detail with reference to FIGS. The glow plug 101 of the present example has a substantially cylindrical housing 110 and its tip 10a protruding from its tip 136, and an annular shape between the inner peripheral surface near the tip of the housing 110 and its outer peripheral surface. It is mainly composed of a rod-shaped (circular shaft-shaped) ceramic heater 10 that is disposed so as to be displaceable in the direction of the axis G while holding a gap, and a sensor that detects a combustion pressure disposed behind the heater 10. . In this example, the sensor is the piezoelectric element 40, and the electric signal generated and changed by compressing the sensor later with the pressure generated when the heater 10 is pushed backward from the tip 10a by the combustion pressure. It is configured to output and detect the combustion pressure. Hereinafter, the overall configuration of the glow plug 101 of this example will be described in detail.

  In this example, the housing 110 includes a substantially cylindrical housing main body 111, and an inner housing 121 for supporting a piezoelectric element, which is inserted and arranged inside the housing main body 111 to support the piezoelectric element 40 behind the ceramic heater 10. The main part is mainly composed of three parts including the front end housing 131 located at the front end portion of the housing main body 111. Each of these housings has a substantially cylindrical or annular shape. Among these, the housing main body 111 includes a screw 113 for attaching the glow plug 101 to the plug hole of the cylinder head by a screwing method on the outer peripheral surface near the rear end. A screw-in polygon part 115 is provided behind the screw 113, and a distal end side of the screw 113 is provided with a cylindrical tube part 117 having a diameter smaller than the valley diameter of the screw 113. The inner housing 121 is inserted and disposed in the portion near the tip of the cylindrical tube portion 117 with a gap fit, and the rear end-facing surface of the flange 123 formed to protrude from the outer peripheral surface of the portion near the tip of its own, The housing body 111 is welded in contact with the front end 118. The flange 123 has the same outer diameter as that of the cylindrical tube portion 117 of the housing main body 111. On the other hand, as shown in the enlarged view of FIG. 1, a cap 127 having a circular hole in the center is formed at the rear end 125 of the inner housing 121 for supporting the element. It is welded through the tip.

  Inside the cap 127, the piezoelectric element 40 is disposed so as to be in contact with the annular bottom plate 129, each having an annular shape, and the insulating plate 47 is disposed on both end faces via the electrode plates 43 and 44. Has been placed. As will be described in detail later, the piezoelectric element 40 has an insulating plate 47 on the lower end side at the rear end of the pressure transmitting hollow shaft member 31 arranged coaxially at the rear end of the ceramic heater 10 and extending rearward. Between the housing 110 and the annular bottom plate 129 so as to be compressed in the axial direction. In addition, it is comprised so that wiring 43b, 44b may be pulled out from each electrode plate 43,44 back, and it may output to ECU.

  On the other hand, at the front end 124 of the flange 123 of the inner housing 121 welded to the front end 118 of the housing main body 111, a seal member 60 described later is disposed through the annular flange 62 at the rear end, and the rear end of the front end side housing 131 is coaxial. It is contacted and welded. The front end housing 131 has a short cylindrical shape, and an inner peripheral surface thereof is formed so that a portion near the front end has a small diameter in two steps from the rear. Further, on the outer peripheral surface of the front housing 131, a portion near the rear end forms a cylindrical portion 133, and a portion near the front end forms a tapered portion 135 corresponding to a tapered seating surface at the back of the plug hole of the engine head.

  In the glow plug 101 of this example, the ceramic heater 10 is mainly composed of a ceramic base body 11 having a circular axis shape and a metal pipe (circular pipe) 20 that is press-fitted into the ceramic base body 11 so as to form an interference fit. Has been. This pipe 20 has a thin pipe portion 21 whose inner and outer diameters are the same diameter later, and a portion closer to the rear end thereof has a predetermined width W1 in the front-rear direction and a relatively large diameter, and is thick along the circumferential direction. Has a thick annular thick portion 24 and a different diameter pipe 20. However, the thickness of the annular thick portion 24 is set to 2 to 3 times that of the thin pipe portion 21. Further, the front and rear of the annular thick portion 24 have end faces cut along a plane perpendicular to the axis G. The ceramic base 11 is provided with a heating element 12 provided in a U-shape so as to be folded back at a portion near the tip, and on the outer peripheral surface of the ceramic base 11 at the portion near the rear end of each leg. Exposed electrode terminals 16 and 17 are provided. In this different diameter pipe 20, the inner peripheral surface 22 is in pressure contact with the outer peripheral surface 11b in the range from the front and rear intermediate portion of the ceramic base 11 to the rear rear end portion (see FIG. 2). However, the inner peripheral surface of the portion corresponding to the annular thick portion 24 in the different diameter pipe 20 is disposed so as to be in pressure contact with one of the electrode terminals (the ground side electrode terminal 16) (see FIG. 1). The annular thick portion 24 in the different-diameter pipe 20 is coaxially positioned in the annular gap K2 whose inner peripheral surface behind the distal end portion of the distal end housing 131 has a large diameter. A relatively narrow annular gap K <b> 1 is formed between the inner peripheral surface of the portion near the tip of the pipe and the outer peripheral surface 23 of the thin pipe portion 20 in the different diameter pipe 20.

  On the other hand, on the outer peripheral surface of the thin pipe portion 21b near the rear end of the different-diameter pipe 20 fitted on the ceramic base 11, a hollow shaft member for pressure transmission arranged coaxially therewith and extending rearward. 31 is externally fitted through its tip (thin tube portion) 32 and welded. And the front-end | tip 32 of the hollow shaft member 31 is made into contact shape with the rear end direction surface 24b in the cyclic | annular thick part 24 in the different diameter pipe 20, and the front-back direction positioning is made | formed. Note that a gap (annular gap) for ensuring insulation is held between the hollow shaft member 31 and the inner peripheral surface of the inner housing 121. The rear end 35 of the hollow shaft member 31 has an annular flange 36 projecting inward so as to have a circular hole in the center (see FIG. 1). As a result, when the ceramic heater 10 is pushed rearward with respect to the housing 110, between the annular flange 36 at the rear end (rear end surface) 35 of the hollow shaft member 31 and the annular bottom plate 129 on the housing side. The piezoelectric element 40 having the electrode plates 43 and 44 on both end faces is configured to be compressed in the direction of the axis G through an insulating plate 47.

  Further, behind the ceramic heater 10, inside the hollow shaft member 31, an electrically conductive shaft member (circular shaft) that retains electrical insulation therewith and extends rearward through a short tube (metal tube) 19. Member) 25 is arranged coaxially. However, the distal end portion of the short tube 19 is externally fitted to the rear end of the ceramic base 11 in an interference fit, and the inner peripheral surface thereof is pressed against the other electrode terminal 17 exposed on the outer peripheral surface 11b of the base 11. Yes. Further, the rear end portion of the short tube 19 is externally fitted into the large-diameter portion 26 at the tip of the energizing shaft member (circular shaft member) 25 so as to maintain conduction. The rear side of the energizing shaft member (circular shaft member) 25 is a circular hole at the rear end 35 of the hollow shaft member 31, and the insulating plate 47, the piezoelectric element 40, the centers of the electrode plates 43 and 44, and the inner housing. 121 extends rearward through a circular hole in the cap 127 at the rear end. The rear end portion is fixed at the rear end in the housing 110 while being insulated by an insulating material (not shown), and the rear end protruding outside is a terminal 25b. In this example, the ceramic heater 10 is configured such that most of the ceramic heater 10 except the rear end portion, together with the different diameter pipe 20, protrudes from the front end 136 of the housing 110.

  As described above, there is relatively less space between the inner peripheral surface of the distal end side housing 131 forming the housing 110 and the outer peripheral surface 23 of the thin pipe portion 21 of the different diameter pipe 20 forming the heater 10. A narrow annular gap K1 is formed. On the other hand, a relatively wide annular gap K2 is formed between the inner peripheral surface of the rear end side housing 131 and the different diameter pipe 20. Further, the annular thick portion 24 in the different diameter pipe 20 is positioned in the annular gap K2 in which the inner peripheral surface of the distal end side housing 131 has a large diameter.

  Now, in this example, the metal seal member 60 is provided in an annular gap K2 in which the inner peripheral surface of the distal end side housing 131 has a large diameter so as to block the inside and outside of the housing 110 in an airtight manner. The rear end side of the seal member 60 is sandwiched and welded between the rear end of the front end side housing 131 and the flange 123 of the inner housing 121 via the annular flange 62 as described above. However, the tip side is welded to the outer peripheral surface 23 of the thin-walled pipe part 21 in the vicinity of the annular thick part 24 in the different diameter pipe 20 as indicated by a black triangle. That is, as shown in FIGS. 2 and 3, the seal member 60 of this example has an annular metal thin film (diaphragm part or membrane part) 63 passing through a plane substantially perpendicular to the axis G on the tip side. The outer diameter pipe 20 is externally fitted. In the sealing member 60, the metal thin film (annular thin film) 63 is positioned ahead of the annular thick portion 24 in the different diameter pipe 20, and the annular thin portion 63 extends forward at the inner peripheral edge of the annular thin film 63. The outer peripheral surface 23 of the thin-walled pipe portion 21 having a relatively smaller thickness than the annular thick-walled portion 24 in the different diameter pipe 20 is welded. That is, from the outer peripheral surface side of the annular portion 65 itself of the seal member 60, welding is performed over the entire circumference along the circumferential direction, for example, as indicated by a black triangle by laser welding.

  On the other hand, the outer peripheral edge of the annular thin film 63 in the seal member 60 has a cylindrical portion 61 extending rearward along the inner peripheral surface of the front end housing 131, and outwards at the rear end of the cylindrical portion 61. As described above, the projecting annular flange 62 includes the front end 124 of the flange 123 of the inner housing 121 welded to the front end 118 of the housing main body 111, and the rear end of the cylindrical portion 133 of the front side housing 131 having a short cylindrical shape. The both contact surfaces of the annular flange 62 are welded along the circumferential direction. In the present example, the seal member 60 arranged in this manner causes a portion near the tip of the housing 110, that is, the annular gap between the inner peripheral surface of the front end housing 131 and the outer peripheral surface of the heater 10. It is shut off in an airtight manner inside and outside. When the heater 10 is displaced rearward by the combustion gas pressure with respect to the housing 110, the seal member 60 is heated mainly in the annular metal thin film (diaphragm portion or membrane portion) 63. It is configured to deform and to allow the displacement while maintaining the airtightness inside and outside the housing 110.

  Thus, when the glow plug 101 of the present example having the above configuration is used by being attached to the cylinder head of the engine, in addition to functioning as a glow plug for promoting the ignition of fuel, the combustion gas pressure ( When the heater 10 pushes the heater 10 backward from the tip 10a, the combustion pressure is detected based on an electric signal obtained by compressing the piezoelectric element 40, and functions as a glow plug with a combustion pressure detection sensor. And the following specific effects can be obtained.

  In this example, the pipe press-fitted into the ceramic base 11 is the different-diameter pipe 20 having the annular thick portion 24 as described above, and the seal member 60 is provided at the tip side of the annular thick portion 24. Is welded to the outer peripheral surface 23 of the thin-walled pipe portion 21 in the vicinity. For this reason, even if the occurrence of welding strain in the thin-walled pipe portion 21, which is the welding location, is unavoidable, the occurrence of welding strain in the annular thick-walled portion 24 can be avoided. And even if the annular thick portion 24 is externally fitted to the ceramic base 11 by press-fitting with the same tightening allowance (press fitting allowance) as the thin-walled pipe portion 21, the wall thickness is much higher than that of the thin-walled pipe portion 21. The thicker part is externally fitted to the ceramic substrate 11 with a strong tightening force (contact pressure in pressure contact). For this reason, even if the ceramic heater 10 is exposed to a high-temperature, high-pressure gas, the annular thick portion 24 has an inner peripheral surface and an outer peripheral surface of the ceramic substrate 11 as compared with other portions. It is possible to reduce the occurrence of looseness between the two. That is, the airtightness between the inner peripheral surface of the different diameter pipe 20 and the outer peripheral surface of the ceramic substrate 11 is prevented by the amount of the annular thick portion 24. This enhances the effect of preventing the combustion gas from entering the back of the glow plug.

  Even if the annular thick portion 24 is present, the seal member 60 is welded at the thin-walled pipe portion 21, so the deformability of the seal member 60 is not impaired. That is, since the dimension in the radial direction of the portion forming the annular metal thin film 63 responsible for the deformation can be ensured in the same manner as in the prior art, the forward and backward movement of the heater 10 is not hindered.

  Further, in the above example, the thin pipe portion 21 to which the seal member 60 is welded is the thin pipe portion 21 on the tip side from the annular thick portion 24. For this reason, the annular thick part 24 is not directly exposed to the combustion gas by the seal member 60. In the present invention, the annular thick portion 24 can be positioned on the tip side from the seal member 60. However, in the above example, the annular thick portion 24 is less susceptible to the thermal influence of the combustion gas. ing. As a result, the tightening force and airtightness of the ceramic substrate 11 can be prevented from being lowered. In addition, the heat of the heater 10 is transferred from the thin pipe portion 21 positioned ahead of the annular thick portion 24 through the seal member 60 to the housing 110 via a short heat transfer path. The high temperature of the annular thick portion 24 is also prevented.

  In the above example, the different diameter pipe 20 is externally fitted to the ceramic base 11 in such a manner that the inner peripheral surface of the portion corresponding to the annular thick portion 24 is pressed against the electrode terminal 16. For this reason, since the clamping force with respect to the electrode terminal 16 is high, a highly reliable electrical connection is obtained. Further, as described above, the annular thick portion 24 is provided near the rear end, and a thin pipe portion (small diameter portion) 21b is also present partly rearward (rear end portion). And since the hollow shaft member 31 for pressure transmission is externally fitted to the small diameter portion 21b and brought into contact with the rear end facing surface 24b of the annular thick portion 24, the fixed front and rear positioning is performed. Can be easily. In the above example, the seal member 60 is formed so that the annular film portion 63 responsible for deformation is perpendicular to the axis G. However, the seal member 60 may be formed to have a tapered shape. However, as shown by the broken line in FIG. 3, the shape structure may be an appropriate one as long as the displacement can be allowed with the forward / rearward movement of the heater 10, such as a bellows shape. That's fine.

  For example, the glow plug 101 in the above example may be assembled as follows. As shown in FIG. 4A, the energizing shaft member 25 is fixed to the heater 10 formed by press-fitting the different diameter pipe 20 into the ceramic base 11 through the short pipe 19 as described above. Next, as shown in FIG. 4B, the hollow shaft member 31 for pressure transmission is externally fitted to the rear end of the different-diameter pipe 20 through the tip 32 and welded. Then, as shown in FIG. 4C, the seal member 60 is externally fitted and welded to a predetermined position in the different diameter pipe 20. On the other hand, as shown in FIG. 5, the piezoelectric element 40 and the like are arranged at the rear end of the pressure transmitting hollow shaft member 31 in the assembly 201 assembled in this way, and the cylindrical cap 127 is welded. The inner housing 121 for supporting the piezoelectric element is assembled to the hollow shaft member 31 by being externally fitted from the rear end side. That is, as shown in the left diagram of FIG. 6, the piezoelectric element supporting internal housing 121 with the cylindrical cap 127 welded is externally fitted to the hollow shaft member 31 from the rear end side, and the front end side housing 131 is ceramic. It fits from the front end 10a of the heater 10. Further, as shown in the right view of FIG. 6, the housing main body 111 is also externally fitted so that the annular flange 62 of the seal member 60 is sandwiched between the three members. In this state, as described above, welding is performed along the circumferential direction between the contact surfaces. Thus, it assembles like FIG. 1 by performing predetermined press-fitting, assembly | attachment, and welding.

  Here, a modification of the first embodiment will be described with reference to FIG. However, the following description will focus on the differences from the first embodiment including other examples, and the same or corresponding parts will be given the same reference numerals, and the description thereof will be omitted as appropriate. That is, in the above example, the annular thick portion 24 is provided at the rear end portion of the different-diameter pipe 20, and the thin pipe portion (small diameter portion) 21b is also provided at the rear (rear end portion). Here, the structure is such that the front end of the hollow shaft member 31 for pressure transmission is fitted, but in FIG. 7, the annular thick portion 24 is provided at the rear end of the different diameter pipe 20. Then, the tip of the hollow shaft member 31 is externally connected to a short tube (metal tube) 19 that connects the rear end of the ceramic base 11 and the tip of a current-carrying shaft member (circular shaft member) 25 extending rearward thereof. It is assumed to be fitted and fixed by welding or the like. That is, in the present invention, as shown in this example, the annular thick portion 24 may be provided at the rear end of the different diameter pipe 20. In addition, the cross-sectional shape thereof may be a semicircular cross-section that is convex as shown by a broken line in the figure, for example, within a range that does not impair the ease of deformation of the seal member 60, and has a strong clamping force. It can be made into an appropriate shape so that it may be obtained.

  Now, a second embodiment of the glow plug with a combustion pressure detection sensor of the present invention will be described with reference to FIG. However, this is the same as the cross section of the annular thick portion 24 in the different diameter pipe 20 press-fitted into the ceramic base 11 in the glow plug with the combustion pressure detection sensor of the first embodiment, and is welded thereto. The only difference is that the cross-sectional shape of the sealing member 60 and the welded part (position) of both are changed.

  That is, in the above example, the annular thick portion 24 of the different-diameter pipe 20 is assumed to have a constant thickness at a predetermined width W1, and the front and rear thereof have end faces cut along a plane perpendicular to the axis G. Yes. Then, the seal member 60 is welded to the thin pipe portion 21 located near the annular thick portion 24 and on the distal end side thereof. On the other hand, in this example, the annular thick part 24 provided in the different diameter pipe 20 is provided with a tapered portion 24c whose outer diameter is reduced from the tip of the annular thick part 24 in the above example toward the front. It is said.

  On the other hand, the sealing member 60 is provided with a tapered cylindrical portion 67 between the annular thin film 63 and the annular portion 65 extending to the tip, which is taper-fitted to the tapered portion 24c of the annular thick portion 24. Then, the sealing member 60 has the tapered cylindrical portion 67 taper-fitted to the tapered portion 24c, and the outer peripheral surface of the tapered portion 24c in the tapered cylindrical portion 67 is indicated by a black triangle in FIG. Welded. That is, in the annular thick portion 24, the seal member 60 is welded to the outer peripheral surface of the taper portion 24c having a relatively small thickness. In other words, the portion having the predetermined width W1 is later formed in the annular thick portion. 24, and it can be said that the tapered portion 24c is regarded as a thin-walled pipe portion. In order to enhance the deformability of the seal member 60, the welding location is preferably a position close to the minimum diameter (outer diameter) portion of the tapered portion 24c.

  Also in this case, since there is an annular thick part 24 which is thicker than the thin pipe part 20, a strong clamping force (contact pressure in pressure welding) is applied to the ceramic base 11 in the vicinity of the part including that part. ). In this example, it can be said that the seal member 60 is welded to the end face facing the tip of the annular thick portion 24. However, since the end face facing the tip forms a tapered portion 24c, the welding can be performed under favorable conditions. The reason is as follows. When welding the seal member 60 to the different-diameter pipe 20, the seal member 60 is externally fitted to the different-diameter pipe 20 that is externally fitted to the ceramic base 11 constituting the heater 10, and, for example, the heater 10 is While rotating around the axis, the welded portion of the seal member 60 is irradiated with a laser for welding. In the external fitting of the seal member 60, it is easy to work so that it is a gap fitting. On the other hand, in the laser welding, it is not preferable that there is a gap (gap) between the outer peripheral surface of the different-diameter pipe 20 serving as a welding location and the inner peripheral surface of the seal member 60. On the other hand, in the present example, since the taper fitting is set as described above, in the welding, the tapered cylindrical portion 67 which is the planned welding portion of the seal member 60 is easily formed into the tapered portion 24c. Since it can be closely attached or bitten, welding can be performed without any gaps. Moreover, in laser welding, there is an advantage that welding can be performed under favorable conditions such that the laser irradiation angle can be set in a plane perpendicular to the axis of the different diameter pipe 20 or in a state close thereto. In the above example, the sealing member 60 is provided with the tapered cylindrical portion 67 that is taper-fitted to the outer peripheral surface of the tapered portion 24c of the different diameter pipe 20. However, the tapered cylindrical portion 67 is not provided. It is also possible to simply fit the outer peripheral surface of the taper portion 24c so as to bite it and make it closely contact. This is also because in this case, welding can be performed without any gaps by welding at the close contact portions.

  FIG. 9 is a modification of the previous example. In the previous example, the annular thick part 24 provided in the different diameter pipe 20 is directed from the tip of the annular thick part 24 having a predetermined thickness W1 toward the front. In contrast to the tapered portion 24c whose outer diameter is reduced, in this example, the annular thick portion 24 is a tapered portion 24c whose outer diameter is reduced toward the front in a different diameter pipe. It is formed as comprising. In addition, the seal member 60 has a tapered cylindrical portion 67 that is connected to the annular thin film 63 and extends to the tip thereof as a tapered cylindrical portion 67 that is taper-fitted to the tapered portion 24 c of the annular thick portion 24. Then, the seal member 60 is shown with a black triangle in FIG. 9 on the outer peripheral surface of the tapered portion 24c in the tapered tubular portion 67 in a state where the tapered tubular portion 67 is taper-fitted to the tapered portion 24c. It is welded to. As in the previous example, the seal member 60 is welded to the outer peripheral surface of the tapered portion 24c. However, in this example, the annular thick portion 24 does not have a predetermined width portion having a constant thickness. Is preferably welded to a thin portion having a relatively thin wall thickness, which is a position close to the tip side where the wall thickness is minimum in the taper portion 24c.

  Although not shown in FIGS. 8 and 9, the annular thickness of the different-diameter pipe 20 is formed in the annular portion 65 extending forward at the inner peripheral edge of the annular thin film 63 using the sealing member having the shape in the first embodiment. You may weld to the outer peripheral surface 23 of the thin-walled pipe part 21 whose thickness at the front end side is thinner than the taper part 24c which forms the meat part 24. In other words, in the present invention, the annular thick portion can have an appropriate cross-sectional shape (a cross-sectional shape when cut along a plane passing through the axis of the pipe). Regardless of the cross-sectional shape, strong tightening to the ceramic base is achieved at the annular thick part, resulting in high airtightness in the front-rear direction between the inner peripheral surface of the different diameter pipe and the outer peripheral surface of the ceramic base It is because it can be. In addition, an annular thick part may be divided | segmented into plurality in the front and back, and two or more may be provided. The seal member can also be applied when a bellows-shaped member is used. In the above example, the sensor is a piezoelectric element, but the sensor is capable of detecting the combustion pressure from the pressure when the combustion gas presses the heater backward or the displacement of the heater in the front-rear direction. Therefore, for example, a strain gauge using a sensor can be similarly applied.

  Further, in the glow plug of the above example, the housing is embodied as a configuration comprising a housing body, an inner housing for supporting a piezoelectric element, and a distal end side housing, but the present invention is limited to such a configuration. However, the present invention can be changed and applied as appropriate without departing from the gist of the present invention. In addition, the annular flange on the outer peripheral edge of the seal member is embodied by being welded and fixed in such a manner as to be sandwiched between the front end side housing and the flange of the inner housing. It is not limited to this. In the assembly of other parts, a welding structure is mainly adopted. However, other than welding along the circumferential direction of the seal member with a different diameter pipe, appropriate fixing means such as caulking, screwing, brazing, etc. are used. Can be used. In the above example, laser welding is used for welding the seal member, but appropriate welding means such as electron beam welding can be used.

DESCRIPTION OF SYMBOLS 10 Ceramic heater 11 Ceramic base | substrate 11b The outer peripheral surface 12 of a ceramic base | substrate The heat generating elements 16 and 17 Electrode terminal 20 Different diameter pipes 21 and 21b The thin pipe part 22 The inner peripheral surface 23 of a different diameter pipe The outer peripheral surface 24 of a thin pipe part Annular thick part 24c Tapered part forming an annular thick part 40 Sensor (piezoelectric element)
60 Seal member 67 Tapered tube portion 101 of seal member Ceramic glow plug 110 with a combustion pressure detection sensor Housing 110 having a cylindrical shape Ends K1, K2 of housing Annular gap

Claims (6)

In a cylindrical housing, a rod-shaped ceramic heater with its tip protruding from its tip holds an annular gap between the inner peripheral surface near the tip of the housing and the outer peripheral surface of the ceramic heater. It is arranged so that it can be displaced in the axial direction,
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 therein, and a metal pipe having an inner peripheral surface fitted in a press-contact state on the outer peripheral surface of the ceramic base. ,
In the annular gap, an annular or cylindrical metal seal member formed so as to allow the ceramic heater to be displaced in an arrangement that shuts the inside and outside of the housing in an airtight manner is provided on the pipe. In the ceramic glow plug with a combustion pressure detection sensor that is fitted and welded along the circumferential direction to the outer peripheral surface of the pipe,
The pipe has a different diameter in a part located in the front-rear direction, an annular thick part having a larger outer diameter than the other part in the part located in the annular gap and continuously thick in the circumferential direction. It is considered as a pipe,
The ceramic glow with a combustion pressure detection sensor, wherein the sealing member is welded to an outer peripheral surface of a thin-walled pipe portion having a relatively small thickness instead of the annular thick-walled portion of the different-diameter pipe. plug.   The said different diameter pipe is equipped with the said thin pipe part in the front end side of the said annular thick part, The said sealing member is welded to the outer peripheral surface of this thin pipe part. Ceramic glow plug with combustion pressure detection sensor as described. The annular thick portion is provided with a tapered portion whose outer diameter is reduced toward the tip,
In claim 1, the seal member is welded to an outer peripheral surface of a thin pipe portion having a relatively small thickness, not the annular thick portion, of the different diameter pipes.
The ceramic glow plug with a combustion pressure detection sensor, wherein the seal member is welded to an outer peripheral surface of the tapered portion having a relatively thin thickness in the annular thick portion.   The seal member is provided with a taper tube portion that is taper-fitted to the taper portion of the annular thick portion, and the seal member is configured such that the taper tube portion is taper-fitted to the taper portion. The ceramic glow plug with a combustion pressure detection sensor according to claim 3, wherein the ceramic glow plug is welded to an outer peripheral surface of the tapered portion at a portion.   5. The ceramic glow plug with a combustion pressure detection sensor according to claim 1, wherein the annular thick portion is provided at a rear end or a portion near the rear end of the different diameter pipe. . On the outer peripheral surface of the ceramic substrate, a plurality of electrode terminals for energizing the heating element provided therein are exposed,
The different-diameter pipe is externally fitted to the ceramic base in such a manner that an inner peripheral surface of a portion corresponding to the annular thick portion of the inner peripheral surface is in pressure contact with one of the electrode terminals. The ceramic glow plug with a combustion pressure detection sensor according to any one of claims 1 to 5.

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