Patent Application
20120053818
The invention concerns an ignition device for a combustion engine with one or several combustion chambers, to each of which an ignition device is associated that comprises a sensor, which reacts to a measurand, which is influenced by a combustion cycle taking place in the respective combustion chamber. Such an ignition device is described in the article by Hans Houben et al. with the title “Pressure sensor glow plug (PSG) for diesel engines”, Journal MTZ11/2004. This publication describes a glow plug for diesel engine, in which a pressure sensor is integrated, which enables to measure the pressure in a combustion chamber, into which the glow plug protrudes. The pressure prevailing in the combustion chamber is transmitted from the heating rod of the glow plug to a stainless steel membrane arranged in the housing of the glow plug, to which micromechanical, monocrystalline silicon resistive wire strains are bonded which form a Wheatstone bridge. The heating rod of the glow plug is mounted elastically mobile in the glow plug housing for that purpose. The Wheatstone bridge is connected to an engine control device. The engine control device can regulate the combustion cycle depending on the magnitude and the variation in time of the pressure in the combustion chamber. However, this advantage is the fruit of an expensive construction of the glow plug with its mobile heating rod.
An object of the present invention is to provide for a solution enabling to determine with less effort a measurand value that is suitable for controlling the combustion process.
This object is met by an ignition device having the features specified in claim 1 and by a combustion engine fitted with such an ignition device. Advantageous further embodiments of the invention are described in the sub-claims.
According to the invention, the sensor, which reacts to a measurand, which is influenced by a combustion process taking place in the respective combustion chamber, is an acceleration sensor and this sensor is provided for every combustion chamber of the combustion engine in the ignition device which is associated to the respective combustion chamber of the combustion engine.
It has surprisingly appeared that a measurand can be acquired with acceleration sensors, which is characteristic of the progression of the combustion process in each individual combustion chamber of a combustion engine and can therefore be used individually for regulating the combustion cycle in the various combustion chambers, when it is the ignition device associated with the respective combustion chamber, which includes the acceleration sensor.
The invention has significant advantages:
There is still a whole range of additional advantageous applications for the acceleration sensor according to the invention deployed in an ignition device:
Such an element is more appropriately used as an acceleration sensor which delivers an electrical output signal. The electrical output signal can be conveyed to a control apparatus or regulation apparatus, in which it can be processed, interpreted and resorted to for the purposes of a control unit or regulation of the combustion cycles in the engine. But the electrical output signal can also be processed and interpreted in the ignition device already, if this device comprises to that end a corresponding electrical respectively electronic circuit. Such a circuit can be provided in the rear, cooler section of a glow plug, of a spark plug, in a high-frequency ignition device for generating a corona discharge and also in the or on the housing of an ignition coil. Such a circuit for processing and interpreting the signals of an acceleration sensor can for its own part be connected with an input of an open or closed loop control apparatus, in particular with an engine control device provided nonetheless with advanced engines.
For the purposes of the invention, acceleration sensors for instance are suitable, which have a seismic mass which is pressed by a spring against a piezoelectric body generating electrical signals by using the piezoelectric effect. Such acceleration sensors are known to those skilled in the art.
Alternately, MEMS Sensors can also be used as acceleration sensors for the purposes of the invention. MEMS designates an acceleration sensor on the basis of a micro-electro-mechanical system. These are miniaturised acceleration sensors. They comprise for instance miniaturised spring-mass systems, in which the springs are only few micron wide silicon webs, on which a mass body also consisting of silicon is suspended elastically. When acceleration occurs, the mass body suspended elastically is deflected and changes its distance from a fixed reference electrode. The electrical capacity between the mass body and the reference electrode is thereby changed and this change in capacity is measured as standard for the acceleration. MEMS Sensors are also known to those skilled in the art.
If the ignition device has a component with a longitudinal axis, the acceleration sensor is then arranged preferably coaxially to the longitudinal axis of this component in the ignition device, preferably in such a way that the acceleration sensor or a unit including the acceleration sensor encloses coaxially the corresponding component. A unit including the acceleration sensor can advantageously contain an electrical circuit, in particular with a microprocessor or similar micro-electronic constitutive element, in which the signals delivered by the acceleration sensor can be processed. For a diesel engine, the acceleration sensor is preferably arranged in the glow plugs. Glow plugs have a heating rod whose tip reaches into the combustion chamber. The acceleration sensor or a unit including it can be annular and could be arranged in such a way that it encloses the heating rod on its end remote from the combustion chamber. The temperatures occurring at this end are low enough for the acceleration sensors of the art described previously to be able to withstand them.
Glow plugs usually have a metal housing which is also designated as a glow plug body in which the heating rod is held which protrudes into the combustion chamber with its glow tip. An electrical connection device is provided on the rear end of the housing of the glow plug. An electrical supply line leads from the connection device to the heating rod. This supply line is also called the internal pole of the glow plug. The acceleration sensor can be arranged in the housing of the glow plug in such a way that it encloses this electrical supply line, the internal pole. Preferably it is held in a recess of the housing of the glow plug. The temperatures occurring in this area of the glow plug are even lower than at the rear end of the heating rod. The signals of the acceleration sensor respectively the output signals of a circuit, which has processed the signals of the acceleration sensor, can be transmitted from the glow plug via the electrical connection device on the rear end of the housing of the glow plug.
In an Otto engine, the acceleration sensor can be arranged in the spark plugs. The spark plugs usually have a metal housing, an electrode passing centrally through the housing—the middle electrode—and an insulating body holding the middle electrode and electrically insulating said electrode from the housing. Preferably, the acceleration sensor respectively a unit including the acceleration sensor encloses the insulating body and is preferably arranged and held in a ring-shaped recess formed between the inside of the housing and the outside of the insulating body. The recess can be arranged in the insulating body or in the inside of the housing or partially in the insulating body and partially in the inside of the housing. Providing that the recess is formed in the insulating body, said recess can be obtained by powder metallurgy by means of corresponding shaping of the die without additional means implemented.
Glow plugs and spark plugs are usually screwed in a threaded bore and should hermetically close the respective combustion chamber, for which purpose a sealing seat is provided in the wall of the combustion chamber, which co-operates with a complementary sealing surface of the glow plug respectively of the spark plug. The acceleration sensor is preferably arranged in the case of glow plugs as well as in the case of spark plugs in the height of the sealing seat. Such an arrangement is particularly suitable since it guarantees that accelerations occurring on the combustion chamber and in particular those occurring on the roof of the combustion chamber are transmitted to the acceleration sensor with minimal damping and in a high bandwidth. Moreover, such an arrangement provides a good thermal connection of the acceleration sensor to the cooled cylinder block respectively cylinder head of the engine, which causes the temperature of the sensor to reliably remain below the temperature of 150° C. which is critical for electrical components. By roof of the combustion chamber is meant the wall of the combustion chamber through which the alternation of load (supply of air and fuel, emission of the exhaust gas) takes place and through which the glow plug respectively spark plug protrudes into the combustion space. In the case of an engine with reciprocating pistons, a removable cylinder head usually forms the combustion chamber roof.
It has appeared that even when the acceleration sensor is fastened in or on a housing of an ignition coil, the coupling of the acceleration sensor to the respective combustion chamber is still sufficient to transmit the accelerations occurring at or on the combustion chamber and in particular those occurring on the combustion chamber roof to the acceleration sensor with sufficiently low damping and in a sufficiently high bandwidth, so that the acceleration sensor can detect even in such an arrangement accelerations caused by processes in the respective combustion chamber. The ignition coil respectively the housing with the ignition coil is preferably fastened to the combustion chamber roof directly. The housing of the ignition coil preferably has a fixing eye with which the housing can be fastened to a stud, which is formed on the combustion chamber roof of the engine. In such a case, the acceleration sensor is preferably arranged on the fixing eye of the housing of the ignition coil because the mechanical coupling to the combustion chamber roof is particularly good there. In particular the acceleration sensor or a unit including the acceleration sensor is preferably annular so that it encloses the journal to which the fixing eye is fastened.
If the engine has an HF ignition device, by means of which a corona discharge is generated in the combustion chambers, then the acceleration sensor is provided preferably in the housing of this ignition device. Such an ignition device can comprise an HF spark plug, which may have a slim, predominantly cylindrical housing similar to the housing of a glow plug. An electrode is preferably run coaxially through this housing, which electrode is electrically insulated with respect to the housing. A coil and/or a capacitor of a high-frequency resonant circuit can be arranged in the rear region of the housing. Also in such a case of a HF spark plug it is recommended as with a glow plug and as with a conventional spark plug to use coaxial arrangement of the acceleration sensor or of a unit including the acceleration sensor in the housing of the high-frequency spark plug. The criteria according to which an acceleration sensor is arranged in the spark plug and in a glow plug and according to which a certain type of acceleration sensors is selected are also valid correspondingly for the integration of an acceleration sensor in an HF spark plug. The advantages, which according to the invention have spark plugs and glow plugs equipped with an acceleration sensor, are valid correspondingly for HF spark plugs, which according to the invention are equipped with an acceleration sensor.
The accompanying schematic drawings provide better explanation of the invention. The drawings include the following figures:
Identical and correlating parts are designated with matching reference numbers in the different drawings.
The acceleration sensor 5 can be single axis, double axis or triple axis, i.e. it can measure accelerations, which occur in one, in two or in three different space axes. Due to its arrangement in the combustion chamber roof 7 or on the combustion chamber roof 7, the acceleration sensor 5 first and foremost reacts to accelerations which occur on the combustion chamber roof 7 and on the glow plug 3 and is excited first and foremost by the combustion process in the corresponding combustion space 1a and/or possibly by moving components associated with the combustion chamber 1, in particular by the piston 2, by valves belonging to the combustion chamber 1 and the drive elements thereof.
Good mechanical connection of the acceleration sensor 5 to the combustion chamber roof 7 is important, so that the accelerations occurring on the combustion chamber roof 7 are transmitted to the acceleration sensor 5 with smallest possible damping and in a high bandwidth. To that end, an arrangement of the acceleration sensor 5 in the height of the combustion chamber roof 7 and in particular in the combustion chamber roof 7 in the vicinity of its underside is particularly advantageously. Good mechanical connection goes along with good thermal connection of the acceleration sensor 5 to the combustion chamber roof 7. The combustion chamber roof 7, which is generally designed as a removable cylinder head is usually force cooled, i.e. it is streaked with cooling channels 15, through which a cooling fluid of the engine is pumped. The temperature of the acceleration sensor 5 arranged in the height of the combustion chamber roof 7 respectively in the combustion chamber roof 7 will therefore remain below the temperature of 150° C., which is critical for electrical and electronic components.
The dynamic processes, which take place in the combustion chamber 1, are the main cause for the accelerations occurring on the combustion chamber roof 7 and on the glow plug 3. The acceleration signals provided by the acceleration sensor 5, their strength and in particular their variation in time enable to draw conclusions about the combustion process taking place in the combustion chamber 1 and to observe for instance the ignition timing and upon completed ignition the rapidity of the propagation of the flame front. The acceleration sensor 5 integrated into the ignition device can deliver measured values which may be used by an engine control device as input data for controlling the combustion cycle or by a glow control apparatus as input data for controlling the heating process of the glow plug 3.
A conical sealing surface 16 is formed on the front end of the housing 6 of the glow plug 3, which surface co-operates with a reversed conical sealing seat 17, which is provided in the bore of the cylinder head 7 receiving the glow plug 3.
In the embodiment of the glow plug 3 illustrated in
The acceleration sensor 5 is annular, rests in a recess 19 of the glow plug housing 6 and preferably encloses coaxially the rear, cool end of the heating rod 12, which, thanks to the good contact over the housing 6 and the sealing seat 17 with the cooled combustion chamber roof 7, remains at a temperature below 150° C.
In the exemplary embodiment illustrated in
In the exemplary embodiment illustrated in
The piezoelectric body 5a, the seismic mass 5b and the spring 5c could also could be arranged in reverse order in the recess 19, but the acceleration sensor 5 hence formed would be less sensitive than in the arrangement illustrated in
Electrical contacts, which abut against the piezoelectric body 5a and there tap the electrical voltage, which is generated by reason of the piezoelectric effect, are not represented in
The assembly of the acceleration sensor 5 illustrated in
The electrical lines, leading from the piezoelectric body 5a to an analyzing circuit, can be cables, in particular shielded cables, or shielded or unshielded lines imprinted on a rigid substrate or on a flexible substrate such as for instance a flexfoil. Printed conductor paths can be envisioned first and foremost inside the housing 6 and cables can be envisioned first and foremost outside the housing 6 of the glow plug 3.
When assembling the glow plug 3 illustrated in
When assembling the glow plug 3 illustrated in
In the embodiment illustrated in
In the embodiment of a glow plug 3 illustrated in
The provision of an acceleration sensor 5 in a glow plug 3 not only enables to draw conclusions about the variation in time of the relative combustion pressure in the combustion chamber 1 on the basis of the acceleration signal. It is also possible to observe the noise generation in the engine and monitor it for anomalies. Knocking in the respective combustion chamber 1 can be detected and be reduced or eliminated by controlling the combustion. The curve of the acceleration signal enables to determine the ignition timing and to acquire insights on the propagation of the flame front in the combustion chamber 1. Finally, it is also possible to measure the accelerations acting upon the glow plug 3 during the engine operation and to use them as input data for an operating strength analysis and for accelerated service life testing (Highly Accelerated Life Test, HALT). Finally, the acceleration signals acquired from an acceleration sensor 5 in the glow plug 3 can also be used to control or to regulate the temperature to which the glow plug is heated, depending on the acceleration signals occurring, individually for every combustion chamber 1 of the engine.
The exemplary illustrated in
The acceleration sensor 5 can also in such a case be single axis, double axis or triple axis, i.e. it can measure accelerations which occur in one, in two or in three different space axes. Due to its arrangement in the combustion chamber roof 7 or on the combustion chamber roof 7, the acceleration sensor 5 first and foremost reacts to accelerations which occur on the combustion chamber roof 7 and on the spark plug 3 and is excited first and foremost by the combustion process in the corresponding combustion space 1a and/or possibly by moving components associated with the combustion chamber 1, in particular by the piston 2, by valves belonging to the combustion chamber 1 and the drive elements thereof.
Good mechanical connection of the acceleration sensor 5 to the combustion chamber roof 7 is important, since that the accelerations occurring on the combustion chamber roof 7 are transmitted to the acceleration sensor 5 with smallest possible damping and in a high bandwidth. To that end, an arrangement of the acceleration sensor 5 in the height of the combustion chamber roof 7 and in particular in the combustion chamber roof 7 in the vicinity of its underside is particularly advantageous. Good mechanical connection goes along with good thermal connection of the acceleration sensor 5 to the combustion chamber roof 7. The combustion chamber roof 7, which is generally designed as a removable cylinder head is usually force cooled, i.e. it is streaked with cooling channels, through which a cooling fluid of the engine is pumped. The temperature of the acceleration sensor 5 arranged in the height of the combustion chamber roof 7 respectively in the combustion chamber roof 7 will therefore remain below the temperature of 150° C., which is critical for electrical and electronic components.
The dynamic processes, which take place in the combustion chamber 1, are the main cause for the accelerations occurring on the combustion chamber roof 7 and on the spark plug 23. The acceleration signals provided by the acceleration sensor 5, their strength and in particular their variation in time therefore enable to draw conclusions about the combustion process taking place in the combustion chamber 1 and to observe for instance the ignition timing and upon completed ignition the rapidity of the propagation of the flame front. The acceleration sensor 5 integrated into the spark plug 23 can provide measured values which may be used by an engine control device as input data for controlling or regulating the combustion cycle or by a spark plug control apparatus as input data for controlling or regulating the sparking process of the spark plug 23.
In the embodiment of the spark plug 23 illustrated in
The acceleration sensor 5 is annular respectively integral part of an annular unit, lies preferably coaxially to the longitudinal axis 38 of the spark plug 23 in a recess 28, which is formed between the housing 26 and the ceramic isolator 25 of the spark plug 23. Thanks to the good contact with the cooled combustion chamber roof 7, the acceleration sensor 5 remains at a temperature below 150° C. The assembly of the acceleration sensor 5 corresponds to that in the glow plug according to
The advantages, which have been offered for the arrangement of an acceleration sensor in a glow plug, are also valid correspondingly for the integration of an acceleration sensor in a spark plug.
In the embodiment illustrated in
The embodiment illustrated in
As shown on
In connection with an ignition coil 31, acceleration sensors other designs can also be used, in particular also the MEMS-acceleration sensors already aforementioned, among which an example in connection with
Also in the embodiments, which are illustrated in
The advantages, which have been explained in the context of the arrangement of an acceleration sensor 5 in a glow plug 3 or in a spark plug 23, are correspondingly valid for the use of an acceleration sensor 5 in the or on the housing 26 of an ignition coil 31.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2010 035 422.8 | Aug 2010 | DE | national |
