JP2007177782A - Glow plug with combustion pressure sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a glow plug with a combustion pressure sensor capable of securing durability and reliability and having stable and excellent sensor sensitivity. <P>SOLUTION: In the glow plug 130 with the combustion pressure sensor, a heater 4 and an outer cylinder 5 are fixed, and a sheath 50 is fixed so as to extend from the outer cylinder 5 to a rear end side. A heater assembly 41 is constituted by the heater 4, the outer cylinder 5, the sheath 50 and a center shaft 6. They are slidble with respect to a main metal fitting 1 in an axial direction (vertical direction in Fig. 6). A holding member 80 is arranged between the outer cylinder 5 and the main metal fitting 1. The holding member 80 is constituted by graphite which is a material having the self-lubricating property. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a glow plug with a combustion pressure sensor used in an internal combustion engine such as an automobile engine.

  Conventionally, glow plugs have been used to assist ignition start of diesel engines for automobiles. Such a glow plug has a cylindrical metal shell, a heater housed and held in the metal shell so that the tip protrudes, and a central shaft provided and held in the rear wall of the heater. The thing of the structure provided with (glow heater electrode) is known. Further, as a glow plug with a combustion pressure sensor for detecting the combustion pressure, for example, a pressure detection element is provided on the rear end side of the metal shell, and a central shaft and a heater fixedly held on the metal shell are connected to the metal shell according to the combustion pressure. In contrast, there is known a structure in which a minute displacement at the time of minute displacement is detected by a pressure detection element to detect a combustion pressure (see, for example, Patent Document 1). However, in the glow plug with a combustion pressure sensor having such a structure, the amount of displacement of the central shaft and the heater with respect to the metal shell is very small with respect to fluctuations in the combustion pressure. For this reason, there is a problem that it is difficult to obtain high sensor sensitivity.

The heater is slidable in the axial direction in the metal shell, and an O-ring made of an elastic body is disposed between the heater and the front end of the metal shell, and slides between the heater and the metal shell. It has also been proposed to have a structure that allows airtight closure (see, for example, Patent Document 2). However, in such a structure in which the heater is held on the leading end side of the metal shell by the O-ring, the O-ring may pass through the interface friction between the O-ring and the heater when used for a long time, or the airtightness of the interface deteriorates. As a result, there is a risk that the output may change, and there is a problem that good sensor sensitivity that is stable in the long term cannot be obtained. This problem becomes prominent in situations where the O-ring is exposed to high temperatures. In addition, since the O-ring made of resin is exposed to high temperatures, there is a problem that it is difficult to ensure sufficient durability and reliability.
JP 2004-124910 A JP 2005-90954 A

  As described above, the prior art has a problem that it is difficult to ensure both durability and reliability and stable and good sensor sensitivity.

  The present invention has been made to solve the above problems. An object of this invention is to provide the glow plug with a combustion pressure sensor which can ensure durability and reliability, and has the stable favorable sensor sensitivity.

  A glow plug with a combustion pressure sensor according to the present invention extends along the axial direction, and is arranged in a cylindrical shape with a metal shell and a rod-shaped tip that protrudes from the tip of the metal shell. A heater assembly having a heater having a heat generating portion; a heater assembly provided on a rear end side of the heater and electrically connected to the heater; and disposed between the heater assembly and the metal shell. A holding part made of a material having self-lubricating and heat resistance, which slidably holds the assembly on the metal shell, and combustion of the internal combustion engine which is detected by the heater assembly and applied to the front end side of the heater assembly And a pressure detection element for detecting pressure.

  In the glow plug with a combustion pressure sensor of the present invention, the heater assembly is slidably held on the metal shell by the holding portion made of a material having self-lubricating properties and heat resistance. Thus, by making the heater assembly movable using self-lubricating properties, the movable range can be increased, sensitivity can be improved, and long-term characteristics can be stabilized. . And since it has heat resistance, sufficient durability and reliability can be ensured. In addition, the heat resistance as used in the field of this invention refers to the material which does not deteriorate (consume) in 300 degreeC air. 300 ° C. is defined after confirming that the temperature does not exceed 300 ° C. by actually measuring the temperature of the tip of the metal shell of the glow plug with the combustion pressure sensor during engine operation.

  The holding part in the present invention can perform airtight sealing appropriately without impairing the slidability of the heater assembly. This good slidability is due to the fact that the holding portion is made of a self-lubricating material having a small frictional resistance even without applying a lubricant. Therefore, in the glow plug with a combustion pressure sensor of the present invention, it is possible to obtain a good detection sensitivity of the combustion pressure by having the holding portion made of a material having self-lubricating properties.

  In the glow plug with a combustion pressure sensor of the present invention, the holding portion may be formed by inserting a member made of a self-lubricating material configured as a separate part between the heater assembly and the metal shell, Further, a self-lubricating material may be coated on at least one of the inside of the metal shell and the outside of the heater assembly to form a coating layer.

In the glow plug with a combustion pressure sensor of the present invention, the holding portion has a static friction coefficient of less than 0.2 on the surface thereof. The reason why the coefficient of static friction is made less than 0.2 is as follows. That is, the pressure due to combustion is about 4 MPa when it is small such as when idling, but in order to make the heater assembly moveable for pressure transmission, the axial load received by the heater assembly from this combustion pressure is the heater assembly. Greater than the static frictional force between the metal shell and the metal shell. That means
Coefficient of static friction x holding force (N) = frictional force <minimum combustion pressure (Pa) x pressure-receiving area (Am ² )
→ Coefficient of static friction <4 MPa × Am ² ÷ holding force (N) (1)
It becomes.

Here, the pressure receiving area is a cross-sectional area of the glow plug heater portion, and the diameter of a general glow plug heater portion in recent years is 5 mm or less. Therefore, A is about 2 × 10 ⁻⁵ (m ² ). In addition, the holding force (mN) has a lower limit because the airtightness between the heater assembly and the holding portion is significantly lowered when the holding force (mN) is extremely low. The lower limit of the holding force is about 400 N as shown in the graph of FIG. 16 showing the result of the airtightness test (applied pressure: 4 MPa) with the vertical axis representing the leak amount and the horizontal axis representing the holding force. As a result of substituting these numerical values into equation (1), the coefficient of static friction is <0.2. From the above results, “having self-lubricating” in the present invention means that the static friction coefficient of the surface of the holding portion (interface between the holding portion and the heater assembly) is smaller than 0.2. As shown in FIG. 17, the static friction coefficient is measured by increasing the axial load Fy while pressing the holding member 8 with a constant load Fx, and the load when the heater 4 slides is expressed as Fymax. Then,
Load Fymax (static friction force) = μ ((maximum) static friction coefficient) × load Fx (pressing load)
Can be measured as

  Further, the holding part preferably has elasticity of 10% or more for both the restoration rate and the compression rate. This elasticity makes it possible to seal the heater assembly and the holding part without any gap when filling the holding part, and to prevent the heat of combustion from entering the inside of the glow plug. It is also effective as a damping material when radial vibration is applied to the heater assembly itself.

  Further, it is preferable to use a material having high thermal conductivity that releases heat so that the heat generated by the heater does not transfer into the glow plug. That is, the holding part has a thermal conductivity higher than that of the heater, so that the heat from the heater can be effectively radiated to the engine head or the like. Thereby, since the inside of the glow plug and the combustion pressure sensor are unlikely to become high temperature, durability of the glow plug with the combustion pressure sensor is improved. Furthermore, it is preferable to use a material having a low coefficient of thermal expansion so that the sensor output value does not change when the force for holding the heater assembly of the holding portion changes between the low temperature and the high temperature. That is, if the holding portion has a thermal expansion coefficient equal to or lower than that of the metal shell, a change in sensor output value at high temperatures can be reduced.

  Examples of the self-lubricating material that satisfies the above requirements include graphite, talc, molybdenum disulfide, tungsten disulfide, and boron nitride. The holding portion may be made of the above material, but may contain other materials in addition to the above material as long as the above requirements are satisfied. Further, among these materials, graphite is one of particularly preferable materials. Ordinary graphite is a relatively hard material and is not suitable in terms of elasticity.However, by subjecting graphite powder to acid treatment and heat treatment, the powder expands, and the expanded powder is pressed to form good elasticity. It becomes possible to grant.

  In addition, the heater includes an electrode extraction portion that is located on the rear end side of the heat generation portion and energizes the heat generation portion, and the holding portion is disposed between the heat generation portion and the electrode extraction portion. It is preferable to install. By disposing the holding portion in such a position, it is possible to prevent the electrical connection reliability of the heater electrode take-out portion from being maintained even when the temperature of the heat generating portion is significantly increased due to the heat generated by the heater. Furthermore, when using a ceramic heater in which the heat generating part is embedded in a ceramic substrate, heat conduction from the heater can be promoted by making the heater directly contact with a self-lubricating material, and the ceramic itself Since it also has a self-lubricating property, it is suitable as a movable structure of the heater.

  Further, when a cylindrical outer cylinder is provided outside the heater, the holding portion can be disposed between the outer cylinder and the metal shell. Moreover, the holding part can airtightly seal between the metal shell and the heater assembly.

  Moreover, as a pressure detection element, a Si type pressure detection element or a SOI type pressure detection element can be used. Such a pressure detection element is, for example, a sheath that is fixed to the metal shell and the middle shaft and is provided on a diaphragm that deforms in response to the sliding of the middle shaft, or a sheath that is mechanically connected to the heater assembly and extends to the rear end side. And a diaphragm that is fixed to the metal shell and deforms according to the slide of the heater assembly. Thereby, the combustion pressure can be detected with high sensitivity. In this case, it is preferable to provide a plurality of pressure detection elements on the diaphragm.

  ADVANTAGE OF THE INVENTION According to this invention, durability and reliability can be ensured and the glow plug with a pressure sensor which has the stable favorable sensor sensitivity can be provided.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing an overall configuration in a direction including an axis of a glow plug 100 with a combustion pressure sensor according to a first embodiment of the present invention.

  The glow plug 100 with a combustion pressure sensor includes a metal shell (housing) 1 made of a metal such as carbon steel and formed in a cylindrical shape. On the outer peripheral surface of the metal shell 1, there is formed a screw portion 2 for attaching the glow plug 100 with a combustion pressure sensor to an internal combustion engine (engine block) (not shown). A tool engaging portion 3 that engages a tool such as a spanner or a wrench when the metal shell 1 is attached to the internal combustion engine is provided on the outer peripheral portion on the rear end side of the screw portion 2.

  A shaft-shaped (columnar) heater 4 is provided on the front end side (left side in FIG. 1) of the metal shell 1 so that the front end portion protrudes. The outer periphery of the heater 4 is covered with a metal outer cylinder 5 such as SUS, except for the tip, and the outer cylinder 5 is held by the metal shell 1. The inner diameter of the outer cylinder 5 is configured to be larger than the outer diameter of the heater 4 so that the heater 4 can slide in the axial direction (left-right direction in FIG. 1). As a result, the heater 4 is substantially slidably held in the axial direction with respect to the metal shell 1. In addition, the heater 4 is connected to the inside of a base made of an insulating ceramic (mainly silicon nitride), a heat generating part 42 having a substantially U-shaped cross section made of a conductive ceramic, and both sides of the heat generating part 42. A lead portion 43 extending substantially parallel to the axial direction toward the rear end of the heater 4 is embedded. The heater 4 (lead portion) and the outer cylinder 5 are electrically connected via a leaf spring 20. The heater 4 generates heat when energized, thereby assisting in starting the internal combustion engine.

  Further, the inside of the metal shell 1 on the rear end side (right side in FIG. 1) of the heater 4 is made of a conductive metal or the like, is formed in a rod shape (columnar shape), and is electrically connected to the heater 4. A middle shaft 6 is provided. The middle shaft 6 serves as an electrode (glow heater electrode) that electrically pulls out the heater 4 to the rear end side, and the tip side thereof is electrically and mechanically connected to the heater 4 via the cap lead 7. The heater assembly 40 is connected. The middle shaft 6 is slidable together with the heater 4 in the axial direction (left-right direction in FIG. 1) with respect to the metal shell 1. In the present embodiment, the electrode extraction portion of the heater refers to the leaf spring 20 and the cap lead.

  In the vicinity of the front end portion (left side in the figure) of the middle shaft 6, a holding member 8 for constituting a holding portion is provided so as to be filled between the middle shaft 6 and the metal shell 1. The holding member 8 is formed in an annular shape by inserting a heater assembly 40 in which a central shaft and a heater are integrated into a metal shell, filling the gap with talc powder, and then pressing with a cylindrical press pin. Thereafter, the outer cylinder 5 and the leaf spring 20 are disposed. By the holding member 8, the space between the middle shaft 6 and the metal shell 1 is appropriately airtight, and the middle shaft 6 is held in a state in which the middle shaft 6 can slide in the axial direction with respect to the metal shell 1. The holding member 8 needs to have a structure capable of ensuring the strength capable of withstanding the combustion pressure of the internal combustion engine and the required airtightness. However, if the length in the axial direction is increased more than necessary, the sliding property of the middle shaft 6 is deteriorated. For this reason, it is preferable that the axial length of the holding member 8 is about 5 mm or less. In addition, although talc is comprised from SiO and MgO, the holding member 8 may contain substances other than talc as long as it has talc as a main component. Further, the holding member 8 is not limited to talc but may be composed of other substances having self-lubricating properties and heat resistance. However, since the holding member 8 is disposed between the middle shaft 6 and the metal shell 1, the holding member 8 also needs to serve as an insulating member that is electrically insulated.

  As shown in FIG. 2, a pressure detection element 9 is provided at the rear end of the middle shaft 6. The pressure detection element 9 is provided on a substantially disc-shaped diaphragm 11 fixed to the middle shaft 6 via an insulating member 10. In this embodiment, as shown in FIG. 3, the pressure detection element 9 extends along the circumferential direction of the diaphragm 11. Are provided at regular intervals. The number of pressure detection elements 9 is not limited to four, and one or more pressure detection elements 9 may be provided. The peripheral edge of the diaphragm 11 is fixed to the metal shell 1, and when the middle shaft 6 slides relative to the metal shell 1, the diaphragm 11 is deformed.

  On the rear end side of the pressure detection element 9, an electronic circuit 12 for processing signals output from the pressure detection elements 9 is provided. The rear end portion of the metal shell 1 is covered with a cover 13, and the rear end portion of the middle shaft 6 is led out from an opening portion 14 provided in the cover 13 to the outside.

  The pressure detection element 9 is composed of, for example, an Si element or an SOI element, and is configured to output an electrical signal corresponding to strain when pressure is applied. When combustion pressure is applied to the front end portion of the heater 4, the heater 4 and the middle shaft 6, that is, the heater assembly 40 slide to the rear end side, and the diaphragm 11 is deformed. The pressure detection element 9 is distorted in accordance with the deformation of the diaphragm 11, and a signal is output from the pressure detection element 9. The pressure detection signal is processed by the electronic circuit 12, and is derived to the outside. This signal is input to a control device such as an ECU, and a change in combustion pressure in the internal combustion engine (engine) is detected.

  In FIG. 2, reference numeral 15 denotes an insulating member. As the insulating member 15, for example, like the holding member 8, a member formed in an annular shape by being pressurized after being filled with talc powder can be used. it can.

  In the glow plug 100 with the combustion pressure sensor configured as described above, the holding member 8 formed in an annular shape by pressurizing the talc is provided between the middle shaft 6 and the metal shell 1 so as to perform airtight sealing appropriately. Since talc is excellent in heat resistance and corrosion resistance, durability can be improved and reliability can be ensured as compared with the case where hermetic sealing is performed using an O-ring made of resin or the like. The holding member 8 made of talc can elastically hold each part, and further has a self-lubricating property, so that airtight sealing between the central shaft 6 and the metal shell 1 is appropriately performed without impairing the slidability. be able to. This makes it possible to obtain good detection sensitivity with stable combustion pressure.

  Next, second and third embodiments will be described with reference to FIGS. In these second and third embodiments, portions corresponding to those of the first embodiment described above are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 4 shows a configuration of a glow plug 110 with a combustion pressure sensor according to the second embodiment. In this embodiment, the holding member 8 is arranged on the rear end side (right side in FIG. 4) as compared with the embodiment shown in FIG. Thus, the arrangement position of the holding member 8 is not limited to the tip portion of the middle shaft 6 and may be a portion on the rear end side.

  FIG. 5 shows a main configuration of a glow plug 120 with a combustion pressure sensor according to the third embodiment. In this embodiment, the heater 4 and the outer cylinder 5 are fixed, and the heater assembly 41 is constituted by the heater 4, the outer cylinder 5 and the middle shaft 6. These are slidable in the axial direction (left-right direction in FIG. 5) with respect to the metal shell 1, and the flange on the rear end side of the outer cylinder 5 is in contact with the metal shell 1. A holding member 8 is disposed between the outer cylinder 5 and the metal shell 1, that is, substantially between the heater 4 and the metal shell 1. Thus, the arrangement position of the holding member 8 is not limited to between the middle shaft 6 and the metal shell 1, but may be between the heater 4 (outer cylinder 5) and the metal shell 1.

  FIGS. 6 and 7 show a main configuration of a glow plug 130 with a combustion pressure sensor according to the fourth embodiment. In this embodiment, the heater 4 and the outer cylinder 5 are fixed, and the sheath 50 is fixed so as to extend from the outer cylinder 5 to the rear end side. A heater assembly 41 is constituted by the heater 4, the outer cylinder 5, the sheath 50, and the middle shaft 6. The outer cylinder and the sheath may be the same member. These can be slid relative to the metal shell 1 in the axial direction (vertical direction in FIG. 6). A holding member 80 is disposed between the outer cylinder 5 and the metal shell 1. The holding member 80 is made of graphite which is a self-lubricating material. That is, the graphite powder is expanded by subjecting the graphite powder to acid treatment and heat treatment, and the expanded powder is pressed and molded. By forming the graphite powder by such a process, the holding member 80 can be given good elasticity.

  For example, the process shown in FIG. 8 can be suitably used as the molding process of the holding member 80. That is, in this step, first, as shown in FIG. 8A, the graphite sheet material 80 formed into a sheet shape is wound around the outer cylinder 5. Then, from this state, as shown in FIG. 8B, when the tip member 82 of the metal shell 1 is attached to the metal shell 1, the graphite sheet material 80 is pressed and deformed in the axial direction and contracted in the axial direction. And is expanded in the radial direction so that the outer cylinder 5 and the metal shell 1 are in close contact with each other without a gap.

  As shown in FIG. 7, in the present embodiment, the diaphragm 11 is provided between the sheath 50 and the metal shell 1, and the pressure detection element 9 is provided on the diaphragm 11. The pressure detection signal of the pressure detector 9 is processed by the electronic circuit 12 and derived to the outside. In FIG. 7, reference numeral 83 denotes an O-ring. In this embodiment, the holding member 80 provided on the front end side and the O-ring 83 provided on the rear end side perform reliable airtight sealing, and The ring 83 is configured not to be exposed to high heat. Since the O-ring 83 is not exposed to a high temperature, deterioration (consumption) due to friction with the heater assembly 41 hardly occurs, but a material having self-lubricating properties is preferable. Further, in this case, since the holding member (graphite) 80 provided on the tip side has a higher thermal conductivity than the heater, the heat of the heater 4 is effectively transferred to the metal shell 1 and released, This prevents heat from entering the rear end side. Further, by preventing the heat from entering in this way, it is possible to prevent the electrical connection reliability of the heater electrode take-out portions 7 and 20 from being unable to be maintained. Furthermore, since the holding member (graphite) 80 is a material having a low coefficient of thermal expansion, changes in the sensor output value at high temperatures can be reduced.

  In the glow plug 130 with the combustion pressure sensor having the above-described configuration, a holding member 80 made of graphite is provided between the middle shaft 6 and the metal shell 1 to perform an airtight seal appropriately. Since graphite is excellent in heat resistance and corrosion resistance, durability can be improved and reliability can be ensured as compared with the case where hermetic sealing is performed using an O-ring made of resin or the like. Since the holding member 80 made of graphite can elastically hold each part and further has self-lubricating properties, airtight sealing between the central shaft 6 and the metal shell 1 is appropriately performed without impairing slidability. be able to. This makes it possible to obtain good detection sensitivity with stable combustion pressure.

  FIG. 9 shows a main configuration of a glow plug 140 with a combustion pressure sensor according to the fifth embodiment. In this glow plug 140 with a combustion pressure sensor, a holding portion is formed by a coating layer 90 in which a material having self-lubricating properties is coated on at least one of the outside of the heater assembly 41 (outer cylinder 5) and the inside of the metal shell 1. ing. Thus, the holding portion can be formed by the coating layer 90 or the like without using another member such as the holding member 8. In this case, the coating layer 90 can be formed by performing a chemical conversion film treatment on the portion to be coated, applying a coating material by impregnation, spraying, brushing, or the like, and drying by normal temperature or heating.

  FIG. 10 shows a main configuration of a glow plug 150 with a combustion pressure sensor according to the sixth embodiment. The glow plug 150 with the combustion pressure sensor has a structure in which the heater 4 made of ceramic directly contacts the holding member 8 without using the outer cylinder 5. In the glow plug 150 with the combustion pressure sensor having such a structure, heat conduction from the heater 4 to the holding member 8 can be promoted.

  Next, a method for manufacturing the pressure detection element 9 will be described. The pressure detection element 9 can be manufactured, for example, from a Si wafer by a process as shown in FIG.

  That is, first, an oxide film 202 (film thickness, for example, 100 nm) is formed on a Si wafer (for example, 400 μm in thickness, resistance value 10-20 Ω · cm, N-type) 201 illustrated in FIG. After the formation, patterning is performed into a rectangular piezoresistor shape (and a linear temperature sensor shape).

Next, boron is doped into the surface layer of the Si wafer 100 by an ion implantation apparatus (boron concentration, for example, 1 × 10 ^{18 to} 3 × 10 ²⁰ atoms / cm ³ ), and thereafter annealing (for example, in a nitrogen atmosphere, at a temperature of 950). Piezoresistors 203 (and temperature sensors) are formed as shown in FIG. 11C.

Next, as shown in FIG. 11D, an HTO film 204 is formed as a protective film of the piezoresistor 203 (and the temperature sensor) (for example, a film forming gas: SiH ₂ Cl ₂ + N ₂ O, temperature 900). After forming a contact hole 205 in the HTO film 204 as shown in FIG. 11E, a pad 206 (for example, Pt) is formed in the contact hole 205 as shown in FIG. / TiN / PtSi).

  Next, as shown in FIG. 11 (g), the lower glass 207 is anodically bonded, and then the upper glass 208 is anodically bonded as shown in FIG. 11 (h).

  Further, the pressure detection element 9 can be manufactured from, for example, an SOI wafer by a process as shown in FIG.

That is, as shown in FIG. 12 (a), the active layer (for example, thickness 1.5 μm, resistance value 10-20 Ω · cm, P-type) and intermediate layer (for example, thickness 1 μm) in order from the surface side (upper side in the figure). First, an SOI wafer 301 having a support layer (for example, a thickness of 525 μm, a resistance value of 10 to 20 Ω · cm, P-type) is used. First, as shown in FIG. The layer is doped with boron (boron concentration, eg, 1 × 10 ^{18 to} 3 × 10 ²⁰ atoms / cm ³ ) and annealed (eg, at a temperature of 1000 ° C. for 5 hours in a nitrogen atmosphere) to thereby cause the piezoresistor 302 (and temperature). Sensor).

  Next, after a resist is patterned on the active layer into a rectangular piezoresistor shape (and a linear temperature sensor shape), the active layer silicon is formed into a rectangular piezoresistor 303 (and a linear temperature sensor shape) using the resist as a mask. Etching (for example, RIE), leaving only the portion), and performing dielectric separation as shown in FIG.

Next, as shown in FIG. 12D, an HTO film 304 is formed as a protective film of the piezoresistor 303 (and the temperature sensor) (for example, film forming gas: SiH ₂ Cl ₂ + N ₂ O, temperature 900). After forming a contact hole 305 in the HTO film 304 as shown in FIG. 12E, a pad 306 (for example, Pt as shown in FIG. 12F) is formed in the contact hole 305. / TiN / PtSi).

  Next, as shown in FIG. 12 (g), the lower glass 307 is anodically bonded, and then the upper glass 308 is anodically bonded as shown in FIG. 12 (h).

  Further, when the pressure detection element 9 is attached to the diaphragm 11, as shown in FIG. 13, a plurality of (for example, four) pressure detection elements 9 are provided on one Si wafer substrate, and the central shaft 6 penetrates in the central portion. It is possible to process the Si wafer into a shape having a possible opening and attach it to the diaphragm 11.

  Of the steps shown in FIG. 13, the steps of FIGS. 13A to 13F correspond to the steps shown in FIGS. 11A to 11F, and FIG. 13 (h) shows the step of anodically bonding the lower glass 210 having an aperture, and FIG. 13 (i) shows the step of anodically bonding the upper glass 211 having an aperture. ing. If one Si substrate having a plurality of pressure detecting elements 9 manufactured in this way is attached to the diaphragm 11, it can be manufactured more easily than attaching the pressure detecting elements 9 one by one.

  Further, when the same process is performed using an SOI wafer, it is performed as shown in FIG. 14A to 14F correspond to the steps shown in FIGS. 12A to 12F, and FIG. 14G shows an opening 309 formed in the SOI wafer 301 by etching. FIG. 14 (h) shows a step of anodically bonding the lower glass 310 having an aperture, and FIG. 14 (i) shows a step of anodically bonding the upper glass 311 having an aperture.

  In addition, as shown in FIG. 15, there is a method in which a piezoresistor formed on an SOI wafer is bonded to a metal wafer (diaphragm) and the support layer of the SOI wafer is removed by etching. That is, in this method, as shown in FIGS. 15A to 15C, the active layer of the SOI wafer 301 is doped with boron and annealed to form the piezoresistor 302, and the active layer silicon and intermediate layer are formed. Is etched, leaving only the rectangular piezoresistor 303, and diced.

  On the other hand, as shown in FIGS. 15D and 15E, a glass layer 402 is formed on the metal wafer 401. Then, as shown in FIG. 15F, the piezoresistor 303 of the SOI wafer 301 is bonded onto the glass layer 402 of the metal wafer 401, and thereafter, as shown in FIG. The support layer 301 is removed by etching.

  Next, as shown in FIG. 15H, an insulating film 501 is formed on the piezoresistor 303, and as shown in FIG. 15I, an electrode pad 502 is formed. In this way, the pressure detection element can be arranged on the metal wafer (diaphragm) 401.

  In the above, the present invention has been described with reference to the embodiment. However, the present invention is not limited to the above-described embodiment and the like, and it is needless to say that the present invention can be appropriately modified and applied without departing from the gist thereof.

Sectional drawing which shows the whole structure of the glow plug with a combustion pressure sensor which concerns on the 1st Embodiment of this invention. Sectional drawing which expands and shows the principal part of the glow plug with a combustion pressure sensor of FIG. The figure which expands and shows the principal part structure of the glow plug with a combustion pressure sensor of FIG. Sectional drawing which shows the structure of the glow plug with a combustion pressure sensor which concerns on 2nd Embodiment. Sectional drawing which shows the structure of the glow plug with a combustion pressure sensor which concerns on 3rd Embodiment. Sectional drawing which shows the structure of the glow plug with a combustion pressure sensor which concerns on 4th Embodiment. Sectional drawing which shows the structure by the side of the rear end of 4th Embodiment. Sectional drawing for demonstrating the manufacturing method of 4th Embodiment. Sectional drawing which shows the structure of the glow plug with a combustion pressure sensor which concerns on 5th Embodiment. Sectional drawing which shows the structure of the glow plug with a combustion pressure sensor which concerns on 6th Embodiment. The figure for demonstrating the manufacturing method of a pressure detection element. The figure for demonstrating the manufacturing method of a pressure detection element. The figure for demonstrating the manufacturing method of a pressure detection element. The figure for demonstrating the manufacturing method of a pressure detection element. The figure for demonstrating the manufacturing method of the pressure detection element joined to the diaphragm. The graph which shows the measurement result of an airtightness test. Sectional drawing for demonstrating the measuring method of a static friction coefficient.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Metal fitting, 4 ... Heater, 6 ... Middle shaft, 8 ... Holding member, 9 ... Pressure detection element, 100 ... Glow plug with a combustion pressure sensor.

Claims (16)

A metal shell that extends along the axial direction and is formed in a cylindrical shape,
A heater having a heating portion that is formed in a rod shape and has a heat generating portion that is disposed so that the front end portion protrudes from the front end of the metal shell, and that is electrically connected to the heater is provided on the rear end side of the heater. A heater assembly having,
A holding portion made of a material having self-lubricating and heat resistance, disposed between the heater assembly and the metal shell, and slidably holding the heater assembly on the metal shell;
A pressure detection element for detecting the combustion pressure of the internal combustion engine applied to the front end side of the heater assembly by detecting the slide of the heater assembly;
A glow plug with a combustion pressure sensor. The glow plug with a combustion pressure sensor according to claim 1,
The glow plug with a combustion pressure sensor, wherein the holding portion is formed by inserting a member made of a self-lubricating material between the metal shell and the heater assembly. The glow plug with a combustion pressure sensor according to claim 1,
The glow plug with a combustion pressure sensor, wherein the holding portion is formed by coating a self-lubricating material on at least one of the inside of the metal shell and the outside of the heater assembly. The glow plug with a combustion pressure sensor according to any one of claims 1 to 3,
The glow plug with a combustion pressure sensor, wherein the holding portion has a surface static friction coefficient smaller than 0.2. The glow plug with a combustion pressure sensor according to any one of claims 1 to 4,
The glow plug with a combustion pressure sensor, wherein the holding portion has elasticity. The glow plug with a combustion pressure sensor according to any one of claims 1 to 5,
The glow plug with a combustion pressure sensor, wherein the holding portion has a thermal conductivity higher than that of the heater. The glow plug with a combustion pressure sensor according to any one of claims 1 to 6,
The glow plug with a combustion pressure sensor, wherein the holding portion has a thermal expansion coefficient equal to or less than that of the heater. The glow plug with a combustion pressure sensor according to any one of claims 1 to 7,
A glow plug with a combustion pressure sensor, wherein the self-lubricating material is any one of graphite, talc, molybdenum disulfide, tungsten disulfide, and boron nitride. The glow plug with a combustion pressure sensor according to any one of claims 1 to 8,
The heater includes an electrode extraction portion that is located on the rear end side of the heat generation portion and energizes the heat generation portion, and the holding portion is disposed between the heat generation portion and the electrode extraction portion. A glow plug with a combustion pressure sensor. The glow plug with a combustion pressure sensor according to any one of claims 1 to 9,
The heater is a ceramic heater in which the heat generating portion is embedded in a ceramic base, and the heater and the holding portion are in direct contact with no other member interposed therebetween. With glow plug. The glow plug with a combustion pressure sensor according to any one of claims 1 to 10,
The heater assembly includes a cylindrical outer cylinder provided outside the heater, and the holding portion is disposed between the outer cylinder and the metal shell. With glow plug. The glow plug with a combustion pressure sensor according to any one of claims 1 to 11,
The glow plug with a combustion pressure sensor, wherein the holding portion hermetically closes a space between the metal shell and the heater assembly. In the glow plug with a combustion pressure sensor according to any one of claims 1 to 12,
A glow plug with a combustion pressure sensor, wherein the pressure detection element is an Si type pressure detection element or an SOI type pressure detection element. The glow plug with a combustion pressure sensor according to claim 13,
The pressure detection element is provided on a diaphragm that is mechanically connected to the heater assembly and extends to the rear end side, and is fixed to the metal shell and is deformed in accordance with the slide of the heater assembly. Features glow plug with combustion pressure sensor. The glow plug with a combustion pressure sensor according to claim 13,
A glow plug with a combustion pressure sensor, wherein the pressure detecting element is provided on a diaphragm that is fixed to the metal shell and the middle shaft and deforms in accordance with the sliding of the middle shaft. The glow plug with a combustion pressure sensor according to claim 14 or 15,
A glow plug with a combustion pressure sensor, wherein a plurality of the pressure detection elements are provided on the diaphragm.

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