DE102005016463A1 - Glow plug with integrated pressure measuring element - Google Patents

Abstract

In particular, for the combustion chamber pressure signal-based engine control, a reliable and cost-effective option for detecting a combustion chamber pressure in self-igniting internal combustion engines is required. Therefore, a glow plug (110) is proposed which has a glow plug module (112) and a pressure measuring module (114) connected to the glow plug module (112). The glow plug module (112) has a radiator (124) and a plug housing (118). The pressure measuring module (114) comprises at least one force measuring element (132) which is integrated in the pressure measuring module (114). The at least one force sensing element (132) is configured to generate an electrical signal in response to a force (130). The at least one force-measuring element (132) is connected to the heating element (124) in the assembled state of the glow plug (110) in such a way that a force (130) can be transmitted to the at least one force-measuring element (132) via the heating element (124).

Description

The The invention relates to a glow plug with integrated pressure measuring element as well as a method for the production such a glow plug. In particular, the invention relates to a glow plug, which in addition to a radiator and a candle case a pressure measuring module having at least one force measuring element.

in the Course of steady tightening the statutory emission regulations, in particular for diesel engines, toughen the requirements for a reduced pollutant emission of self-igniting Internal combustion engines. Modern engine management systems should ensure low fuel consumption and at the same time have a long life.

A Combustion optimization in the combustion chamber of a diesel engine can be achieved in particular through the use of a regulated injection of fuel achieve. This regulated injection can be controlled in particular are powered by electronic engine control units, which are already in have established modern motor vehicles. The successful execution of a combustion chamber pressure signal based engine control (combustion signal based control system, CSC) however, of the availability of production suitable Pressure sensors from which high demands in terms of price, reliability, accuracy and space to meet have to.

Currently are widely used measuring devices which have so-called "stand-alone" sensors Insert must have a separate hole in the cylinder head wall be what an extra Assembly costs means. In addition, stand-alone sensors require additional Holes in the cylinder head of the internal combustion engine, in particular in four-valve engines today's construction due to the very cramped space raises significant problems. Furthermore, the price is in the re gel of such systems comparatively high, and the life of such Systems is, mostly due to the high operating temperatures, much shorter as a typical vehicle life.

Accordingly, there are approaches in the prior art to integrate combustion chamber pressure sensors into already existing components of the cylinder head. An example of such an integration are spark plugs with integrated piezoelectric force measuring element, which for example DE 694 05 788 T2 are known. This document discloses a spark plug with built-in pressure sensor, wherein the pressure sensor has at least one pressure introduction channel, which connects the combustion chamber of an associated cylinder of the internal combustion engine with the pressure sensor.

A such sensor integration into already existing components The cylinder head brings a significant price advantage and also makes a mass production economically possible. In such systems deleted the need for direct access to the combustion chamber. on the other hand depends on that signal quality Such combustion chamber pressure sensors strongly from the force curve throughout mechanical bond and sufficient usually not the requirements.

Out DE 196 80 912 C2 For example, an apparatus and method for detecting cylinder pressure in a diesel engine is known. The device comprises a pressure sensor, a heating section of a glow plug, which is received in the interior of a cylinder of the diesel engine and can be acted upon by the cylinder pressure and a fixing member for fixing the heating section in a body of the glow plug. In this case, the pressure sensor is arranged between the heating section and the fixing member of the glow plug. The cylinder pressure is transferred to the pressure sensor via the heating section.

In the DE 196 80 912 C2 However, the disclosed device has the particular disadvantage that the pressure sensor is directly connected to the heating section and thus exposed to high temperature loads and temperature fluctuations. Furthermore, an assembly of in the DE 196 80 912 C2 consuming device, since first the heating section must be introduced into the body of the glow plug, after which then the pressure sensor must be positioned centrally on the heating section to ensure proper functionality of the device. Subsequently, the pressure sensor on the side facing away from the cylinder of the device must be fixed by means of the fixing device, which in turn involves the risk of misplacement of the pressure sensor. Testing the functionality of the pressure sensor is possible only in the fully assembled state of the glow plug.

Out DE 102 18 544 A1 is known a glow plug with built-in combustion pressure sensor. The glow plug includes a housing having a combustion pressure sensor concentrically disposed about a core and biased by the core. The combustion pressure in an engine is transmitted through the core as force, thereby reducing the force exerted on the core by the pressure sensor on the pressure sensor. The combustion pressure is thus converted into a reduction of a preload on the pressure sensor and thus by means of an electrical signal of the pressure sensor be recorded.

In the DE 102 18 544 However, the arrangement shown has the disadvantage of a high number of parts. Furthermore, the connection between the core and the concentrically arranged around this core pressure sensor during assembly can cause difficulties, since it can lead to tension between the core and the pressure sensor. Component tolerances can be critical here. Furthermore, also in the DE 102 18 544 A1 shown construction testable only in the fully assembled state, so that only after a complete assembly any errors can be detected.

Advantages of the invention

It will therefore be a glow plug with integrated pressure measuring element and a method for manufacturing such a glow plug proposed which has the disadvantages of the prior art known glow plugs avoid with integrated pressure measuring element.

One The basic idea of the invention is the glow plug of two separate Assemble modules. The glow plug has a radiator and a candle case on which components of a first module of the glow plug are. Furthermore, the glow plug a pressure measuring module, which faces away from the radiator on a Side to the candle housing followed. In the pressure measuring module at least one force measuring element is integrated, which generate an electrical signal in response to a force can. The pressure measuring module is connected to the first module in this way, that the at least one force measuring element directly or indirectly with the radiator connected, such that over the radiator a force on the at least one force measuring element transferable is.

When Force measuring element can be a variety of known in the art Insert components. Particularly advantageous piezoelectric, piezoresistive, capacitive, inductive force measuring elements and / or Insert measuring elements with strain gages (DMS). Basically However, other mechanical-electrical transducer elements used.

The Inventive glow plug offers opposite the known from the prior art devices a number of advantages. In particular, the use of a separate pressure measuring module causes and the modular design that the outer dimensions of at least a Kraftmesselements no longer by the internal space of the plug housing is limited. As a result, a larger selection of force measuring elements is commercial available, which reduces costs of production and avoids delivery bottlenecks can be. It can be done under certain circumstances also use force measuring elements, which a higher precision, lower temperature dependence and other advantageous properties, but due to of the low available standing space in conventional, from The glow plugs known from the prior art can not be integrated would.

Farther causes the modular design of the glow plug, that in construction and assembly ensures a high level of customer independence so that, for example, one and the same type of glow plug can be integrated into different engine types. For example enough For this purpose, a simple replacement of the pressure measuring module.

at the production of the glow plug can in particular the first module and the pressure measuring module in separate Steps, for example by separate manufacturers or in different production facilities, be made. In the production of the first module of the radiator with the candle case connected. During the production of the pressure measuring module at least a force measuring element integrated into the pressure measuring module. Both modules in particular, are separately testable, since the functionality of the two Module is independent of the other module.

On This way, errors can be discovered early on in the production process and which greatly reduces the scrap, lowers costs and reduces reliability of the components increased. Subsequently the pressure measuring module and the first module are connected to each other, such that over the radiator a force on the at least one force measuring element transferable is. This connection can in particular cohesively, for example by welding, and / or by a non-positive Connection done.

For transmission the power of the radiator on the at least one force measuring element can in particular at least a power transmission element be used. Example, as the at least one power transmission element having a power transfer ram.

This additional at least one force transmission element has the particular advantage that the radiator and the at least one force measuring element can be spatially separated from each other. Thus, in particular the Druckmessmo Dul be arranged outside the combustion chamber of the internal combustion engine, so that the at least one force measuring element is exposed to the lowest possible temperature loads and temperature fluctuations. Since the signal characteristics of many commercially available force measuring elements depend significantly on the operating temperature and / or temperature fluctuations, this construction according to the invention is thus of considerable advantage for the signal quality.

When Advantageously, it has also been proven that the at least a force measuring element at least one perpendicular to an axis the glow plug extending actuator surface having. The at least one force measuring element can, for example the shape of a disc, such as a circular disk having and can radially on a housing be fixed to the pressure measuring module. It can over the at least one power transmission element in the axial direction directly or indirectly a force on the at least an actuator surface be exercised. For example, the glow plug additionally have at least one membrane which between the at least a power transmission element and the at least one force-measuring element is arranged. These Membrane may in particular be an integral part of the at least one Be force elements.

In the embodiment in which at least one force transmission element is used, it has proved to be advantageous if the Glow plug additional a vibration damping element having. This vibration damping element In particular, at least one cavity between the at least a power transmission element and the candle housing complete or partially. especially when elongated power transmission elements, for example a power transfer ram used this has been to suppress vibrations of the at least one force transmission element proved to be beneficial to unwanted vibration and thus undesirable Artifacts in the electrical signal of the at least one force-measuring element to avoid.

The first module and the pressure measuring module can in particular by a Interface, for example, a partition to be separated from each other. In this case, it is advantageous if the at least one partition wall Has at least one power transmission opening.

For example it may be at this power transmission opening to act a central bore through which a power transfer ram in the axial Directed becomes.

drawing

Based the drawing, the invention is explained in more detail below.

It shows:

1 an embodiment of a glow plug according to the invention; and

2 An embodiment of a method according to the invention for producing a glow plug.

In 1 is an inventive embodiment of a glow plug 110 shown. The glow plug 110 has a first module 112 (Glow plug module) and a pressure measuring module 114 on. Both modules are along an interface through a partition wall 116 separated from each other, which is part of the pressure measuring module 114 or the glow plug module 112 can be. Also two partitions 116 are possible, with z. B. a partition part of the Glühstiftmoduls 112 and a partition wall part of the pressure measuring module 114 is. The connection between pressure measuring module 114 and glow plug module 112 can be done for example by welding. A screw connection through appropriate union nuts is conceivable.

The glow plug module 112 has a housing 118 with a substantially cylindrical interior 120 on. At one of the printing module 114 facing away, a combustion chamber of the internal combustion engine facing the end of the housing 118 shows the case 118 a sealing cone 122 in which a (in this embodiment, ceramic) radiator 124 is admitted. Here is the ceramic heater 124 in the sealing cone 122 such with the case 118 connected, for example by gluing, that the interior 120 is sealed substantially against the influences of the combustion chamber. The ceramic radiator 124 can also be soldered into a metallic support tube, which is then welded to the housing or can be pressed into this.

The ceramic radiator 124 has at its front, the combustion chamber end facing a pressure surface 126 on, which in this embodiment as a surface perpendicular to an axis 128 the glow plug 110 is designed. The pressure in the combustion chamber of the internal combustion engine causes a force F (reference numeral 130 ) on the ceramic heater (which, mutatis mutandis, it can also be a metallic radiator) is exercised. This force verur gently a linear-elastic deflection of the power path located in the components of the glow plug 110 , This deflection is usually in the micrometer range. About this linear-elastic deflection can be a force on the glow plug 110 be transferred, which correlates directly with the combustion chamber pressure.

A way of capturing this force 130 according to the invention is that in the pressure measuring module 114 a force measuring element 132 is arranged. The force measuring element 132 has substantially the shape of a perpendicular to the axis 128 arranged circular disc and has an end face 134 with an integrated, miniaturized membrane on top of the radiator 124 facing side is arranged. The force-measuring element, which may be a piezoresistive force-measuring element, for example, as described above, has two signal lines 138 on which at the glow plug module 112 opposite end of the pressure measuring module 114 axially from a housing 140 led out and a corresponding signal processing (not shown) are supplied.

Will a force on the force measuring element 132 exerted, this is the force measuring element 132 in corresponding electrical signals, such as a voltage or a current, converted by means of the signal lines 138 can be tapped.

The force measuring element 132 is circumferentially with the housing in this embodiment 140 connected, for example by gluing or by a corresponding thread. Additionally or alternatively, the force measuring element 132 also from the heating element 124 be supported away from the side, for example, characterized in that the housing 140 has an internal thread, in which, for example, a corresponding ring can be screwed with an external thread.

Unlike the one described above DE 196 80 912 C2 can in this inventive embodiment of the glow plug 110 thus to an additional fixing member behind the force measuring element 132 be waived. The force measuring element 132 is much more peripherally on the housing 140 from the glow plug module 112 separate pressure measuring module 114 fixed. As a result, the inventive design also differs significantly from that in the EP 102 18 544 A1 illustrated arrangement. In particular, as described above, a separate production of the two modules 112 . 114 possible. It can also be different variants of the glow plug module 112 and the pressure measuring module 114 whose geometries are adapted to specific customer requirements. However, the interface geometry, which is an assembly of the two modules 112 . 114 along the partition 116 allows to be type independent, so that is a "building block" of glow plug modules 112 and pressure measuring modules 140 results.

Due to the length of the power transmission element 142 , ie in particular the fact that the power transmission element 142 has a length which significantly exceeds its diameter, can occur in the excitation spectrum for mechanical vibrations vibration modes in the mostly undesirable low frequency range. By such natural resonances, the evaluation of the signals of the force measuring element 132 difficult, or completely prevented.

To remedy this problem is in the embodiment according to 1 According to the invention, a vibration damping element 146 intended. This vibration damping element 146 is in this embodiment, in which a cylindrical power transmission ram 142 is used as a power transmission element, advantageously designed as a cylinder sleeve and fills an annular gap between the power transfer ram 142 and the housing 118 of the glow plug module 112 completely off.

Advantageously, in order to completely fill the annular gap, the vibration damping element 146 a resin, in particular an electrically and / or thermally insulating resin may have. This resin can be in the liquid state in the annular gap between the power transfer ram 142 and the housing 118 of the glow plug module 112 are filled and then cured there. Instead of a resin but also a variety of other materials can be used, which can be introduced in the liquid or plastic state in the annular gap, and then cured there. The curing can be done in whole or in part, so that, for example, an elastic or a plastic vibration damping element 146 results. Furthermore, the curing can take place in various ways, for example by UV action or by heat treatment. Numerous other possibilities are conceivable and known to the person skilled in the art.

Furthermore, in the embodiment according to 1 the with glow plugs 110 Commonly used steel connection bolts for a Glühstromzuleitung to the ceramic heater 124 replaced by a thin and / flexible Drahtglühstromzuleitung 148 , The wire filament feed line 148 causes the small amount of available space inside the case 118 of the glow plug module 112 optimally utilized. This wire glühstromzuleitung 148 can have a radial bore 150 out of the case 118 of the glow plug module 112 led out and supplied to a corresponding power supply.

In 2 is an embodiment of a method according to the invention for producing a glow plug 110 , for example, to the in 1 shown glow plug 110 represented. The illustrated method steps need not necessarily be performed in the order shown, and additional, in 2 not shown process steps are performed. Individual process steps can also be carried out repeatedly.

In process step 210 becomes a first module 112 made, which is a radiator 124 and a housing 118 having. This is the radiator 124 with the candle case 118 connected. In process step 212 becomes this first module 112 tested, for example, the functionality of the radiator 124 by applying a corresponding current, for example via the Drahtglühstromzuleitung 148 , is checked.

In process step 214 becomes a pressure measuring module 114 , for example, according to the embodiment according to 1 , mounted, in particular at least one force-measuring element 132 , for example 132 of the type described above, in the pressure measuring module 114 is integrated. Subsequently, in process step 216 the pressure measuring module 114 tested. This testing can be done, for example, by passing over the opening 144 in the partition 116 the membrane 136 of the force measuring module 132 is acted upon by a suitable test element with a defined force, which by the force measuring element 132 generated electrical signal, for example, on the signal lines 138 can be detected. In particular, malfunctions of the pressure measuring module can be achieved in this way 114 detect.

Subsequently, in process step 218 the pressure measuring module 114 and the glow plug module 112 connected to each other, for example by welding or by connecting by means of a union nut. This connection is made such that a force from the radiator 124 on the force measuring element 132 is transferable. For example, for this purpose connecting the power transmission ram 142 through the centric bore 144 into the interior of the pressure measuring module 114 guided and on the membrane 136 be put on.

In this embodiment, the force 130 from the heating element 124 completely or partially by means of a power transmission element 142 , which in this Ausführungsbei play as a power transfer ram 142 is designed, transmitted. This power transfer ram 142 transfers the power 130 axially on the face 134 of the force measuring element 132 , For this purpose, the power transfer ram 142 through a centric bore 144 guided.

110

glow plug

112

heater plug

114

Pressure measurement module

116

partition wall

118

Housing of Glühstiftmoduls

120

inner space

122

sealing cone

124

ceramic radiator

126

print area

128

axis

130

force

132

Force measuring element

134

face

136

membrane

138

signal lines

140

Housing of Pressure measuring module

142

Power transmission plunger

144

centric drilling

146

Vibration-damping element

148

Drahtglühstromzuleitung

150

radial drilling

210

manufacturing heater plug

212

Testing of the glow plug module

214

Assembly of the pressure measuring module

216

Testing of the pressure measuring module

218

Connect of pressure measuring module

and heater plug

Claims (11)

Glow plug ( 110 ) for a self-igniting internal combustion engine, comprising a first, a radiator ( 124 ) and a candle housing ( 118 ) module ( 112 ) as well as a pressure measuring module ( 114 ), wherein the pressure measuring module ( 114 ) on a radiator ( 124 ) facing away from the first module ( 112 ), wherein at least one force measuring element ( 132 ) into the pressure measuring module ( 114 ), wherein the at least one force measuring element ( 132 ) is configured to generate an electrical signal in response to a force ( 130 ), wherein the at least one force measuring element ( 132 ) so with the radiator ( 124 ) that is connected to the radiator ( 124 ) a force ( 130 ) on the at least one force measuring element ( 132 ) is transferable. Glow plug ( 110 ) according to the preceding claim, characterized in that the at least one force-measuring element ( 132 ) comprises at least one of the following components: a piezoelectric force measuring element ( 132 ), a piezo Resistive force measuring element ( 132 ), a capacitive force measuring element ( 132 ), an inductive force measuring element ( 132 ) and / or a force measuring element ( 132 ) with strain gages (DMS). Glow plug ( 110 ) according to one of the two preceding claims, characterized in that the candle housing ( 118 ) and the pressure measuring module ( 114 ) are cohesively and / or non-positively connected. Glow plug ( 110 ) according to one of the preceding claims, characterized by at least one additional power transmission element ( 142 ), wherein by means of the at least one power transmission element ( 142 ) a force ( 130 ) of the radiator ( 124 ) on the at least one force measuring element ( 132 ) is transferable. Glow plug ( 110 ) according to the preceding claim, characterized in that the at least one power transmission element ( 142 ) a power transfer ram ( 142 ) having. Glow plug ( 110 ) according to one of the two preceding claims, characterized in that the at least one force-measuring element ( 132 ) at least one perpendicular to an axis of the glow plug ( 110 ) extending actuator surface ( 134 ), wherein the at least one force measuring element ( 132 ) radially on a housing ( 140 ) of the pressure measuring module ( 114 ) and wherein by means of at least egg NEN force transmission element ( 142 ) in the axial direction directly or indirectly a force ( 130 ) on the at least one actuator surface ( 134 ) is exercisable. Glow plug ( 110 ) according to one of the three preceding claims, characterized by at least one membrane ( 136 ) between the at least one power transmission element ( 142 ) and the at least one force measuring element ( 132 ), wherein the at least one membrane ( 136 ) preferably in the at least one force measuring element ( 132 ) is integrated. Glow plug ( 110 ) according to one of the four preceding claims, characterized by at least one in the plug housing ( 118 ) received vibration damping element ( 146 ), wherein the at least one vibration damping element ( 146 ) at least one cavity between the at least one force transmission element ( 142 ) and the candle housing ( 118 ) completely or partially fills. Glow plug ( 110 ) according to the preceding claim, characterized in that the at least one vibration damping element ( 146 ) at least one resin ( 146 ) having. Glüshtiftkerze according to any one of the preceding claims, characterized by at least one partition wall ( 116 ) between the plug housing ( 118 ) and the pressure measuring module ( 114 ), wherein the at least one partition ( 116 ) at least one power transmission opening ( 144 ) having. Method for producing a glow plug ( 110 ) for a self-igniting internal combustion engine, comprising the following steps: a) a first module ( 112 ), comprising a radiator ( 124 ) and a candle housing ( 118 ), with the radiator ( 124 ) with the candle housing ( 118 ) is connected; b) a pressure measuring module ( 114 ), comprising at least one force measuring element ( 132 ) is mounted, wherein the at least one force measuring element ( 132 ) is configured to generate an electrical signal in response to a force ( 130 ) to create; and c) the pressure measuring module ( 114 ) is done with the first module ( 112 ) connected to the radiator ( 124 ) a force ( 130 ) on the at least one force measuring element ( 132 ) is transferable.