KR20120041123A - A pressure-measuring plug for a combustion engine - Google Patents

Abstract

A piezoelectric resistance pressure measuring plug 1 for a combustion engine for measuring pressure is disclosed. This pressure measuring plug comprises a plug body 2 and a sensing structure 4. The plug body is configured to provide a seal between the plug body and the combustion engine with a threaded plug body portion 2a having an external thread for screwing the plug body into the cylinder of the combustion engine, A sealing plug body portion 2b forming a tip. The plug body further comprises a sensing body portion 2c located between the threaded plug body portion and the sealing plug body portion. The sensing body portion is integrally formed and includes a cylindrical body portion 2c1, a sensing structure and a moving portion 2c2. The sensing structure forms a connection between the moving part and the cylindrical body part, allowing the moving part to move relative to the cylindrical body part along the cylinder axis 6 of the cylindrical body part.

Description

PRESSURE MEASUREMENT PLUG FOR COMBUSTION ENGINES

The present invention relates to a pressure measuring plug for a combustion engine, the plug body comprising a plug body and a sensing structure, the plug body having a threaded plug body portion having an external thread for screwing the plug body into a cylinder of the combustion engine, and the plug. And a seal plug body portion configured to provide a seal between the combustion engine and the combustion engine and for forming a tip of the plug. More specifically, the present invention relates to piezoelectric resistance pressure measuring plugs for combustion engines.

The progressive combustion strategy of future diesel and otto engines depends on the presence or absence of accurate pressure feedback from each cylinder during the entire cycle of the combustion engine (compression-combustion-exhaust cycle). Such a strategy may or may not include Homogeneous Charge Compression Ignition (HCCI) combustion and may result in high pressure incidences requiring fast and accurate pressure response.

Pressure measuring plugs of the aforementioned type are known from European patent application 2138819A1. According to the patent application, the moving rod is disposed in the plug body. The sensing structure is disposed between the rod and the plug body such that prevailing pressure in the combustion chamber of the cylinder acts on the sensing structure, whereby the rod transfers pressure inside the combustion chamber of the cylinder to the sensing structure. The rod is disposed in the plug body so as to be displaceable in an axially sliding manner with respect to the plug body such that the pressure of the combustion chamber causes the heating rod to move in the axial direction relative to the plug body, resulting in a force Act on the sensing structure.

It is an object of the present invention to provide an improved pressure measuring plug which excludes at least one of the aforementioned prior art limitations. It is a further object of the present invention to provide a pressure measuring plug having at least one of lower cost and more reliable manufacture, long lasting and / or robustness against coarse pressure media, and resistance to the normal high temperature and vibration of combustion engines. will be.

According to the invention, this object is achieved by a pressure measuring plug with the features of claim 1. Advantageous embodiments and further methods for carrying out the invention may be achieved by the measures mentioned in the dependent claims.

According to the invention, the plug comprises a plug body, the plug body comprising a sensing body portion located between the threaded plug body portion and the sealing plug body portion. The sensing body portion is integrally formed and includes a cylindrical body portion, a sensing structure and a moving portion. The sensing structure forms a connection between the moving part and the cylindrical body part and allows the moving part to move relative to the cylindrical body part along the cylinder axis of the cylindrical body part when the pressure of the combustion chamber or cylinder of the combustion engine changes. .

The above-mentioned feature makes it possible to manufacture pressure measuring plugs with a reduced number of components. Compared with the device shown in European patent application 2138819A1, the sensing structure is formed of an integral part constituting part of the plug body, thus eliminating the need for an annular weld for joining the sensing structure to the plug body. In addition, there is no need for a weld to couple the moving rod to the sensing structure. As the number of welds to be formed is reduced, the processing steps are reduced, and as a result, the production cost of the pressure measuring device is reduced. Another advantage of the configuration of combining the sensing structure integrally with part of the plug body is that there is no longer a weld under stress due to the pressure acting on the rod. Accordingly, the life of the plug can be improved. The plug body is to be provided with a seal to form a hermetic seal between the plug body and the combustion engine. As a result, the stress due to the pressure of the medium is not applied to the welding portion for coupling the pressure sensing portion to each of the threaded plug body portion and the sealing portion of the plug body. The pressure sensing portion of the plug body is clamped between the sealing portion of the plug body and the threaded plug body portion.

In one embodiment, the thickness of the cylindrical body portion of the sensing body portion is thicker than the thickness of the threaded body portion and / or the sealing plug body portion. This feature allows the pressure measuring plug according to the invention to be significantly less sensitive to the effects of mounting forces and torques.

In one embodiment, a piezo resistor element is attached to the annular surface of the sensing structure, the annular surface being in a plane perpendicular to the cylinder axis. In particular, the sensing structure comprises a hole for forming an annular surface, which is located in line with the moving part. The hole is also located at the center of the sensing structure. In one embodiment, the center of the sensing structure coincides with the cylinder axis of the plug body. This feature improves the stress distribution at the surface to which the piezoresistive element is attached, making the sensing structure less sensitive to pressure measurement operation.

In one embodiment, the holes of the sensing structure are through holes extending along the cylinder axis through the sensing structure and the moving portion. This feature allows the manufacture of one sensing body part suitable for use in different applications. For example, by attaching a dummy rod to the through hole, the sensing body portion can only be used for a plug for measuring pressure. By attaching a glow rod to the through hole, the sensing body portion can be used for pressure measurement and a glow plug. By attaching the temperature sensor to the through hole, the sensing body portion can be used for a pressure / temperature measuring plug.

In one embodiment, the sensing body portion comprises an annular recess, which not only accommodates one end of the threaded body portion, but also positions the sensing structure on the threaded body portion and further comprises a sensing structure and And to provide an annular space between the sand body portions. This feature provides a sensing body portion that is less sensitive to thermal shock caused by welding the threaded body portion to the sensing body portion.

In yet another embodiment, the annular recess further provides a separation groove in the sensing body portion between the cylindrical body portion and the sensing structure. This feature has the effect of further reducing the sensitivity of the pressure measuring plug to the mounting force and torque of the plug body.

In one embodiment, the sensing body portion is a component formed concentrically along the cylinder axis of the plug body. According to this feature, the stress on the annular surface can be uniformly distributed about the cylinder axis, thereby alleviating the importance of the piezo resistor element arrangement.

In one embodiment, the sensing body portion is a metal injection molded portion. Thus, the sensing body portion can be easily manufactured with high accuracy. In addition, the material for manufacturing the sensing body portion using injection molding is less expensive than the stainless steel used to form a monolith by a metal cutting process.

In one embodiment, the plug further comprises an annular membrane comprising an outer first rim and an inner second rim. The first rim is welded to the outer edge of the cylindrical body portion. The second rim is welded to the moving part. This annular membrane provides a seal between the cylindrical body portion and the moving portion. The membrane can protect the sensing structure from the extreme temperatures caused by the combustion process by allowing the moving portion of the sensing structure to move without friction in the axial direction of the cylindrical plug body portion. This membrane also serves to define the pressure sensitive area.

It will be apparent that the various aspects referred to in this patent application may be combined with each other and may also be considered separately for split patent applications, respectively. Other features and advantages of the invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings, in which various features of the preferred embodiments of the invention are shown by way of example.

According to the present invention, it is possible to provide a pressure measuring plug which can be manufactured reliably at a lower manufacturing cost, is excellent in durability and / or robustness, and is resistant to high temperature and vibration.

The foregoing and other aspects, features, and advantages of the present invention are described below on the basis of the following detailed description of the preferred embodiments with reference to the drawings, wherein like reference numerals refer to the same or comparable parts.
1 is a cross-sectional view of a first embodiment of a pressure measuring plug according to the invention.
FIG. 2 is a perspective view of the sensing body portion and membrane shown in FIG. 1. FIG.
3 is a sectional view of a second embodiment of a pressure measuring plug according to the invention.

Referring to the drawings, FIG. 1 shows a first embodiment of an improved pressure measuring plug 1 formed in accordance with the invention. Only the portion from the thread of the pressure measuring plug to the top of the plug is shown. The plug portion from the thread to the connector is not shown because the portion does not affect the present invention. For the same reason, the electronic components of the sensor which can be provided on the PWB of the plug body are not shown.

In the example of the embodiment shown in FIG. 1, the plug body 2 comprises a threaded body part 2a, a sensing body part 2c and a sealing body part 2b, which parts are welded together. It is mechanically connected to each other. The sealing body portion 2b is provided with a sealing conical portion 2b1 on the combustion chamber side, through which the pressure measuring plug seals the cylinder head against combustion pressure. The threaded body portion 2a comprises an external thread for screwing the pressure measuring plug 1 into the combustion chamber through the opening of the combustion engine.

The sensing body portion 2c is integrally formed and comprises a cylindrical body portion 2c1, a sensing structure 4 and a moving portion 2c2. The sensing structure 4 serves to couple the moving part 2c2 to the cylindrical body part 2c1 on the side facing the threaded body part 2a. The outward facing surface of the cylindrical body portion 2c1 forms part of the outer side of the plug body. Piezo-resistive element 10 is attached to the annular surface 4a of the sensing structure 4 of the sensing body portion 2c. The annular surface 4a is in a plane orthogonal to the cylinder axis 6.

The sensing structure 4 comprises a hole 4b for forming a central opening of the annular surface. The hole 4b is located in line with the axis 6 of the moving part 2c2. It should be noted that the axis of symmetry 6 of the sensing body portion 2c coincides with the body axis of the cylindrical body portion 2c1 and the body axis of the moving portion 2c2.

The sensing body portion 2c comprises an annular recess 2d which is configured to receive one end of the threaded body portion 2a. When the end of the threaded body portion is received in the annular recess, the sensing structure 4 is disposed in the threaded body portion 2a. The annular space between the sensing structure 4 and the inner side of the threaded body portion 2a improves the measuring characteristics of the measuring plug.

The annular recess 2d also provides a separating groove 2e in the sensing body portion 2c between the cylindrical body portion 2c1 and the sensing structure 4. This has the effect of reducing the stiffness of the material between the sensing structure 4 and the cylindrical body portion 2c1. This reduces the sensitivity of the pressure measuring plug to the mounting force. If these two parts are welded together, after cooling, some stress occurs in the weld zone. This stress can be reduced by placing the sensing structure 4 at a distance from the welding zone and / or by the separating groove 2e.

As best shown in FIG. 1, the thickness of the cylindrical body portion 2c1 of the sensing body portion 2c is thicker than the thickness of the annular wall of the threaded body portion and / or the sealing plug body portion.

The sensing body portion 2c may be formed by a metal injection molding (MIM) process or a metal cutting process. It has been found that the MIM process is a cost effective process that can lower manufacturing costs.

The sensing body portion comprises another annular recess 2f for receiving the sealing body portion 2b of the plug body 2. The annular recess 2f is also configured to form the outer edge of the sensing body portion 2c for receiving the flexible annular membrane 12. The annular membrane 12 is an S-shaped membrane and includes a first edge portion 12a and a second edge portion 12b. The profile of the first edge portion 12a surrounds the profile of the second edge portion 12b. The first rim 12a is welded to the outer edge of the cylindrical body portion 2c1. The second edge portion 12b is welded to the moving portion 2c2. The annular membrane 12 provides a seal between the cylindrical body portion 2c and the moving portion 2c2 and protects the sensing structure 4 from the coarse environment inside the combustion chamber, in particular from the high temperature combustion chamber to the sensing structure. It serves to protect the mounted sensing element 10. The membrane 12 as described above also serves to reduce the radial movement of the tip of the moving part, thereby improving the measurement properties of the sensing structure 4.

FIG. 2 is a perspective view of the membrane 12 and the sensing body portion 2c shown in FIG. 1. The sensing body portion 2c and the membrane 12 are concentrically formed portions. By using the MIM process to form the sensing body portion 2c, the concentricity of the sensing body portion 2c can be improved.

The pressure measuring glow plug shown in the figures operates in the manner described below. As a result of the compression or combustion pressure of the piston, the moving part 2c2 is displaced in the axial direction 6 with respect to the cylindrical body part 2c1 of the sensing body part 2c. The annular surface 4a of the sensing structure 4 is deformed to generate surface stress. A piezo-resistive sensor, wire strain gauge or similar measuring element 10 attached to the surface 4a senses the magnitude of the stress, so that the electronic components of the sensor A representative pressure value at work is determined.

Thus, the sensing structure 4 converts the axial movement of the moving part 2c2 into radial surface deformation. When the moving part 2c2 is moved in the axial direction along the symmetry axis 6, the piezoelectric resistance element 10 mounted on the annular surface of the sensing structure 4 provides a resistance change indicative of the surface deformation described above.

The film 12 is preferably formed of a metallic material and is, for example, radial and circumferential fillet welds or radial and to the moving portion 2c2 and the cylindrical body portion 2c1. Mechanical connection is made using circumferential through welds. Such a connection may also be achieved by laser welding, crimping, swaging, soldering, press fit, or the like. The film 12 may be formed in the form of a film as shown in FIG. 1 or 3, or may be formed in the form of a bellows type seal (not shown).

3 shows a second embodiment of the pressure measuring plug 1 according to the invention. The second embodiment has much in common with the first embodiment shown in Figs. In the second embodiment, the solid moving part 2c2 of the first embodiment is replaced by an elongated interface body 2c2 'comprising a longitudinal through hole 8 for the placement of the rod. The rod may be a dummy rod, a glow rod, a temperature sensing rod, or a spark plug. One side of the through hole 8 terminates at the central hole 4b of the sensing structure 4.

According to the second embodiment, the pressure measuring plug can be calibrated before the plug is completed, that is, before the heating rod, the temperature measuring rod or the dummy rod is welded to the hollow moving part 2c2 '. This not only enables the manufacture of a calibrated pressure measuring plug subassembly, but also allows other manufacturers to complete the plug by attaching the required rod to the subassembly, i.e. pressure measuring / glow plug, pressure and temperature measuring It is effective to form a pressure measuring plug having a plug or a dummy rod. Mounting the rod on the elongated interface body does not cause an offset or sensitivity change of the sensing structure, so no further calibration is necessary. Therefore, pressure correction can be realized by using a temporary sealing member to close the through hole 8 before welding the final rod to the sensor. In addition, pressure calibration of a plug provided with a detachable sealing member is also possible. In this case, by separating the sealing member, a pressure calibration plug subassembly is constructed, which pressure weld plug subassembly welds the final rod to the free end of the elongated interface body 2c2 'to provide the necessary through hole 8. It can also be completed by a third party in a way that provides a closing effect. Since the attachment of the final rod and the combustion engine mounting of the finished plug do not affect the properties of the pressure measuring part of the plug, subsequent calibration is not necessary until the combustion engine is controlled using the pressure signal generated by the plug.

It should be noted that the elongate interface body 2c2 'may be formed of two or more parts that are mechanically connected using laser welding, crimping, swaging, soldering, press fit, or the like. In this case, the sensing body portion 2c comprises a body portion 2c1, a sensing structure 4 and a short moving part. Thereafter, at the end facing away from the sensing structure 4, an elongate hollow interface body is attached to the short moving hollow moving part, so as to obtain a structure having properties similar to those in the embodiment shown in FIG. have.

According to the invention, the combustion pressure acts on the outer surface of the rod. The pressure acting on the rod and the membrane 12 is transmitted to the sensing structure 4 by the hollow moving part 2c2 ', and thus converted into a force acting on the sensing structure 4. The moving part 2c2 'moves along the longitudinal axis 6 as the pressure is changed.

The threaded body portion 2a and the sealing portion 2b are preferably formed of high resistance stainless steel, such as precipitation hardened stainless steel, which has high strength and hardness, excellent corrosion resistance and easy heat treatment.

The sensing body portion 2c may be manufactured by a metal injection molding (MIM) process. The strain gauge may be a microfuse type silicon strain gauge formed by a Micro Electro Mechanical System (MEMS) process, and may be coupled to the sensing structure 4 through glass bonding. The film 12 is preferably formed of a material having oxidation resistance and corrosion resistance that is very suitable for repair and maintenance in extreme environments. An example of such a material is an inconel alloy.

Measurements as described above for embodying the present invention can be clearly performed separately or in parallel, or in different combinations or, where appropriate, in a manner in which further measurements are complemented, in which case the practice of the invention Is preferably performed according to the field of application of the device. While certain embodiments of the invention have been described by way of example, it is to be understood that the invention includes all modifications and equivalents falling within the scope of the appended claims.

1: pressure measuring plug 2: plug body
2a: threaded plug body part 2b: sealed plug body part
2c: sensing body portion 4: sensing structure
4a: annular surface 6: axis
8: hole 10: piezo-resistive element

Claims (11)

A pressure measuring plug 1 for a combustion engine, comprising a plug body 2 and a sensing structure 4, the plug body comprising:
A threaded plug body portion 2a having an external thread for screwing the plug body 2 into the cylinder of the combustion engine; And
Sealed plug body portion 2b configured to provide a seal between the plug and the combustion engine and forming the tip of the plug 1
In the pressure measuring plug comprising:
The plug body further comprises a sensing body portion 2c positioned between the threaded plug body portion 2a and the sealing plug body portion 2b,
The sensing body portion 2c is integrally formed and includes a cylindrical body portion 2c1, a moving portion 2c2, and a sensing structure 4,
The sensing structure 4 forms a connection between the moving part 2c2 and the cylindrical body part 2c1, the moving part 2c2 along the cylinder axis 6 of the cylindrical body part 2c1. A pressure measuring plug, characterized in that it allows relative movement with respect to 2c1. 2. The piezoelectric resistance element 10 is characterized in that it is attached to an annular surface 4a of the sensing structure 4, the annular surface 4a being in a plane orthogonal to the cylinder axis 6. Pressure measurement plug. The pressure measurement as claimed in claim 2, wherein the sensing structure 4 comprises a hole 4b for forming an annular surface, the hole 4b being located in line with the moving part 2c2. plug. 4. The pressure measuring plug according to claim 3, wherein the hole (4b) is a through hole (8) extending along the cylinder axis (6) through the sensing structure (4) and the moving part (2c2). 2. The sensing body portion (2) according to claim 1, wherein the sensing body portion (2c) is adapted to position the sensing structure on the threaded body portion (2a) to receive one end of the threaded body portion (2a), and the sensing structure (4). And an annular recess (2d) which is configured to provide an annular space between the threaded body portion (2a). 6. The pressure according to claim 5, characterized in that the annular recess (2d) further provides a separating groove (2e) in the sensing body portion (2c) between the cylindrical body portion (2c1) and the sensing structure (4). Measuring plug. 2. The pressure measuring plug of claim 1 wherein the thickness of the cylindrical body portion of the sensing body portion is thicker than the thickness of the threaded body portion and / or the sealing plug body portion. 2. The pressure measuring plug according to claim 1, wherein the sensing body portion is a component formed concentrically along the cylinder axis. 6. The pressure measuring plug according to claim 1, wherein the sensing body portion (2c) is a metal injection molded portion. 2. The plug of claim 1 further comprising an annular membrane 12, wherein the first edge of the membrane is welded to the outer edge of the cylindrical body portion 2c1 and the second edge is welded to the moving portion 2c2, Pressure measuring plug, characterized in that to provide a seal between the cylindrical body portion (2c1) and the moving portion (2c2). Pressure sensing element 2c comprising the technical features of the sensing body part according to claim 1.

Images