DE3110996A1 - Sensor arrangement - Google Patents

Abstract

A sensor arrangement is proposed for detecting physical parameters in the combustion chamber of an internal-combustion engine, having an optical pick-up facing the combustion chamber. In order to keep the pollution of the window of the pick-up on the combustion-chamber side as low as possible, the end of the pick-up exposed to the combustion chamber is constructed thickened in the manner of a mushroom. By being combined with a centre electrode or a conductor track mounted on the outside, the sensor can be used at the same time as a spark plug. It is particularly advantageous to provide in the sensor a cavity resembling a heat pipe. <IMAGE>

Description

Sensor arrangement

PRIOR ART The invention is based on a sensor arrangement according to the genre of the main claim.

Internal combustion engines are only seemingly continuous working machines. Although torque and speed are quasi-continuous output variables, however, they are generated by a rapid succession of individual processes.

In the course of optimizing the operation of internal combustion engines, in particular with a view to reducing fuel consumption, it is therefore necessary to grasp these relationships in detail; about influencing the individual process to be able to influence the overall process in the desired manner.

The prerequisite for this is the determination of the condition inside the Internal combustion engine. Typical state variables are pressure and temperature, which in the case of the ideal gas, state the overall condition. The operation of Engines with internal combustion are also significantly affected by chemical processes and changes in substances determined, so that this operation cannot be described globally with pressure and temperature is, however, the observation of pressure and temperature provides sufficient information via the changes in the state variables over the engine cycle.

It is known to perform the detection in the combustion chamber of an internal combustion engine the temporal and spatial spread of the combustion process, the detection the ignition point, the recording of injection processes as well as the measurement of itegular Make burns.

These irregular burns also include what is known as "knocking", which occurs in internal combustion engines under certain working conditions. One understands including sound-frequency vibrations of the compressed fuel-air mixture, triggered by a shock wave. The heat transfer occurs during these oscillations greatly increased on the piston and cylinder walls of the internal combustion engine. This has a harmful thermal overload of these surfaces result, so that the knocking in principle is to be avoided. On the other hand, since one strives to use the available To utilize the working range of the internal combustion engine as much as possible, it is necessary to Provide means to indicate the knocking early and safely in order to respond to this Way to be able to implement a regulation of the internal combustion engine, in which the internal combustion engine is always operated just below the knock limit.

For this purpose, a large number of sensors have become known or has been proposed. For example, from DE-OS 28 01 969 a sensor is known, with the help of a piezoelectric vibrating element as a flexural vibrator resonant system is formed, which indicate the knocking of the internal combustion engine able. A disadvantage of this known arrangement is that the mechanical operation is not free from malfunctions, especially in the event of strong impacts in the motor vehicle.

On the other hand, it is known from measurement technology, the combustion process to observe and measure in an internal combustion engine with optical means. So is for example in the Motortechnische Zeitschrift, 39 (1978), page 385 a Describes a spectrometric measuring method for the investigation of the combustion in the diesel engine, with a quartz window in the combustion chamber wall through which a spectrometric Observation of the combustion processes is possible.

From the Rev. Tech. Automobile. 1979, pages 89, 90 is still an optical one Known analyzer, which is screwed in place of the spark plugs of an internal combustion engine to perform a calorimetric analysis of the fuel-air mixture.

However, the known arrangements have the disadvantage that in operation the sensor arrangement relatively quickly becomes heavily soiled by the combustion gases occurs in the combustion chamber.

Advantages of the invention The sensor arrangement according to the invention with the Characteristic features of the main claim has the advantage that low contamination of the combustion chamber side Window of the sensor arrangement and a good light output is achieved even for longer operating times, that the end on the combustion chamber side is made thickened in the shape of a mushroom.

The measures listed in the subclaims are advantageous Further developments of the sensor arrangement specified in the main claim are possible.

So in a preferred embodiment of the invention in addition to optical observation system an electrode as a center electrode or conductor track provided, whereby the arrangement doubles as a spark plug and optical sensor can be used.

In a further preferred embodiment of the invention is in the Sensor arrangement a cavity designed as a heat pipe is provided, as a result of which overheating the sensor arrangement and thus auto-ignition of the engine can be prevented.

Exemplary embodiments of the invention are shown in the drawing and explained in more detail in the following description. They show: figure 1 shows a first embodiment of a sensor arrangement according to the invention with a solid optically translucent glass or ceramic body; Figure 2 shows an embodiment according to Figure 1, however, with a center electrode; Figure 3a and b two further embodiments with a central, optically translucent body, supported by an insulating Ceramic part is surrounded; Figure 4 shows a further embodiment with a heat pipe designed cavity; Figure 5 shows a further embodiment with an antechamber.

Description of the exemplary embodiments In FIG. 1, 10 is the combustion chamber an internal combustion engine, which is adjacent to a cylinder head 11. In the Cylinder head 11 is screwed into a spark plug-like housing 12, which has a massive having central glass or ceramic body 13. This glass or ceramic body 13 is provided with a mushroom-shaped thickening 14 at its end toward the combustion chamber. At its end facing away from the combustion chamber, the glass or ceramic body 13 goes into itself known way in an optical cable over or it is at its combustion chamber facing away End of a photosensitive element arranged, which is connected to an electrical cable is. The optical cable or the light-sensitive element are in a plug-in element 16 held, the slide with grooves 15 on the glass or ceramic body 13 and is lockable.

The mushroom-like thickening 14 is particularly insensitive to soiling. This is due to the fact that the thickening occurs particularly from the fuel mixture that is sucked in wetted and by the strong gas flow through the advancing compression stroke is "washed clean".

An additional self-cleaning effect results from a combined Arrangement according to Figure 2, in which a central electrode 17 is also provided, which is connected to a high-voltage supply line 18 in the plug element 16. the The arrangement according to FIG. 2 is at the same time as a spark plug and sensor arrangement can be used for observation of the combustion chamber. With this arrangement, the spark slides over the hot mushroom-shaped thickening 14 and burns with each ignition process a new channel over the glass or ceramic body 13 free. Another advantage this arrangement lies in that optimal mixture accessibility and thus a safe ignition is given, since the spark is at any Place can skip over the mushroom-shaped thickening 14 and thus at the point breaks through at which the mixture is best ionizable.

In Figure 3a and b are two further embodiments of an inventive Sensor arrangement shown, both embodiments have in common that a centric glass or ceramic body 20 or 22 from an electrically insulating Ceramic body 21 and 23 surrounded within the housing 12 and the plug element 16 is.

In the embodiment according to FIG. 3a in the left half of the section there is a metallic admixture to the material of the glass or ceramic body 20, e.g.

Cu, Fe, Pt or the like. Attached. The glass or ceramic body acts in this way 20 at the same time as an electrical conductor for the ignition high voltage and as an optical conductor Head for the combustion chamber signal.

In the embodiment according to FIG. 3b in the right half of the section in contrast, a glass or ceramic body 22 is provided without admixtures, the electrical In this case, however, the conductor is through a conductor track 24 on the outside of the Glass or ceramic body 22 realized.

This conductor track 24 can, for example, consist of a coating, a Foil, a metal fabric stocking or the like. Consist. The conductor track 24 runs in a metal ring 25, which is between the electrically insulating ceramic body 23 and the mushroom-shaped thickening 14 is arranged.

In a further embodiment of a sensor arrangement according to the invention, as shown in Figure 4, the fact is taken into account that at the mushroom-shaped thickening 14 possibly high temperatures appear which can lead to auto-ignition in the engine. For this reason, at the embodiment according to Figure 4 in a glass or ceramic body 26 a cavity 27 is provided in the form of a so-called "heat pipe". One such heat pipe is usually with a thermally conductive substance, preferably sodium or mercury filled, with the sodium or mercury on the hot, combustion chamber facing Side evaporates and is reflected again on the colder side facing away from the combustion chamber can. In this way, such a heat pipe results in cooling of the mushroom-shaped ones Thickening 14. In order to also supply high voltage for the ignition in this case can, the cavity 27 can, for example, with an inner metallization 29 provided the electrical conduction through the sodium or mercury insufficient, being at the two opposite ends of the glass or ceramic body 26 center electrodes 28 and 28 'are specified. The center electrode 28 is included arranged in the combustion chamber 10 and the center electrode 28 'in the end remote from the combustion chamber, where it is connected to the high-voltage supply line 18.

The body 26 according to Figure 4 can also be metallic, the optical Observation via a glaze applied to the body 26 or a glass fiber stocking, which is pulled over the body 26 is possible. However, it is also possible to use the To make ceramic body 30 of optically translucent material, so that the Body 26 can be metallic without there being an optically translucent coating requirement.

Finally, in FIG. 5 there is yet another exemplary embodiment Sensor arrangement according to the invention shown, in which the arrangement in a spark plug-like casing is housed, which also has an antechamber 31. Although in FIG. 5 shows only one embodiment with a center electrode as in the embodiment is shown according to Figure 2, it goes without saying that such Arrangement with an antechamber also combined with the other proposed arrangements can be.

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Claims (13)

Claims /; 1 sensor arrangement for detecting physical parameters in the combustion chamber of an internal combustion engine with an optical one facing the combustion chamber Sensor, in particular according to patent application P 30 01 711.9, characterized in that that the transducer has a mushroom-shaped end at its end exposed to the combustion chamber (10) Has thickening (14). 2. Sensor arrangement according to claim 1, characterized in that the Sensor is housed in a spark plug-like housing (12) on which of a plug-in element (16) can be plugged on the outside. 3. Sensor arrangement according to claim 1 or 2, characterized in that that the sensor has a centrally arranged, optically translucent glass ode Ceramic body (13, 20, 21, 26), the end of which on the combustion chamber side is mushroom-shaped is thickened. 4. Sensor arrangement according to claim 3, characterized in that the Glass or ceramic body (13) has a center electrode (17). 5. Sensor arrangement according to claim 3, characterized in that the Glass or ceramic body (20) from an electrically insulating ceramic body (21) is surrounded and contains metallic additions, preferably Cu, Fe, Pt. 6. Sensor arrangement according to claim 3, characterized in that the Glass or ceramic body (22) has a conductor track (24) on its surface a foil, a metal fabric stocking, a metallized surface or Like. Has and is surrounded by an electrically insulating ceramic body (23). 7. Sensor arrangement according to claim 6, characterized in that the Conductor track runs out below the mushroom-shaped thickening (14) in a metal ring (25). 8. Sensor arrangement according to one of claims 5 to 7, characterized in that that the glass or ceramic body (26) one with a thermally conductive substance, preferably Has Na or Hg-filled cavity (27) in the form of a heat pipe. 9. Sensor arrangement according to claim 8, characterized in that the Glass or ceramic body (26) is preferably metallized on the inside + - and on its a center electrode (28, 28 ') leads to the outside at both ends. 10. Sensor arrangement according to claim 2, characterized in that the Sensor has a centrally arranged, metallic body, the combustion chamber-side End is mushroom-shaped and thickened by an optically translucent coating, preferably a glaze or a glass fiber stocking and an electrically insulating one Ceramic body is surrounded. 11. Sensor arrangement according to claim 2, characterized in that the Sensor has a centrally arranged metallic body, the combustion chamber side The end is mushroom-shaped and thickened by an electrically insulating, optically translucent ceramic body is surrounded. 12. Sensor arrangement according to claim 10 or 11, characterized in that that the metallic body is one with a thermally conductive substance, preferably Has Na or Hg-filled cavity (27) in the form of a heat pipe. 13. Sensor arrangement according to one of the preceding claims, characterized characterized in that the mushroom-shaped thickening (14) is arranged in an antechamber (31) is.