Device and method for measuring combustion processes in an internal combustion engine

Abstract

The invention relates to a device for measuring combustion processes in an internal combustion engine, comprising a sensor which is fastened to a surface of the internal combustion engine, wherein the sensor is designed to measure deformations of the surface of the internal combustion engine which are generated by combustion processes in the internal combustion engine.

Description

State of the art

[0001] The invention is based on a device and a method for measuring combustion processes in an internal combustion engine according to the preamble of the independent patent claims. Devices and methods for measuring combustion processes in an internal combustion engine are already known, in which an acceleration sensor is mounted on an internal combustion engine. Such acceleration sensors are typically suitable for measurements in a frequency range greater than 1 kHz. DE 100 18 265 B4 already discloses methods for measuring combustion chamber pressure, in which a strain gauge is positioned in the interior of the cylinder head. Such measuring arrangements are extremely sensitive with regard to the positioning of the strain gauges and exhibit significant distortion of the measurement signals due to changing temperatures. From the article "Amirante, R., Casavola, C., Distaso, E., and Tamburrano, P., "Towards the Development of the In-Cylinder Pressure Measurement Based on the Strain Gauge Technique for Internal Combustion Engines," SAE Technical Paper 2015-24-2419, 2015, doi:10.4271 / 2015-24-2419" the basic usability of a strain gauge for measuring combustion processes is already known. For this purpose, such a strain gauge is arranged in a cooling channel of an internal combustion engine. For the use of strain gauges, direct installation on site is therefore provided, which is problematic for the measurement signal of the strain gauges due to the temperature stress. Advantages of the invention

[0002] The device and method according to the invention with the features of the independent patent claims have the advantage that the sensors are less sensitive to both assembly and temperature changes. It has surprisingly been found that commercially available sensors are suitable for measuring deformation of the surface of internal combustion engines due to combustion processes in the internal combustion engine. This enables a significantly simpler and more robust measurement of combustion processes in an internal combustion engine.

[0003] Further advantages and improvements arise from the measures of the dependent patent claims. It is particularly advantageous that sensors can be used in which a strain gauge is arranged in a housing. The actual measuring element is protected by the housing from both environmental influences and excessively high temperatures. Surprisingly, strain gauges packaged in a housing of this type are also suitable for detecting combustion processes in an internal combustion engine. It has proven entirely sufficient to attach such sensors to the outside of a cylinder block of the internal combustion engine. Attachment can be achieved particularly easily by gluing or screwing. By aligning a preferred measuring direction of the sensor parallel to the rotational axis of the crankshaft of the internal combustion engine, an optimized measuring signal can be achieved.Combustion processes in internal combustion engines can be analyzed particularly effectively when signals with a frequency greater than 0.5 Hz are also evaluated. In particular, such signals, with a lower frequency than conventional acceleration sensors, can reliably detect combustion with pre-ignition. This improves the analysis of combustion processes in internal combustion engines. Particularly reliable and useful signals are provided by sensors that use a piezo element as a measuring element. The sensor signals are evaluated particularly effectively by evaluation electronics and used to control the internal combustion engine. Drawings

[0004] Embodiments of the invention are illustrated in the drawings and explained in more detail in the following description. It shows the Fig. 1 an internal combustion engine with a sensor for measuring combustion processes in the internal combustion engine and Fig. 2 a detailed view of the sensor and a cylinder of the internal combustion engine. Description

[0005] In the Fig. 1 schematically shows an internal combustion engine 1 with a sensor 2 attached to its surface. The sensor 2 is designed to measure deformations of the surface of the internal combustion engine 1 and is connected to a control unit 4 via a connecting line 3. The control unit 4 determines information regarding the combustion processes taking place in the internal combustion engine 1 based on the signals from the sensor 2. Based on the information thus determined regarding the combustion processes in the internal combustion engine 1, the control unit 4 calculates control signals for actuators or control elements of the internal combustion engine 1 and sends corresponding control signals via line 5 to the control elements or actuators of the internal combustion engine 1.

[0006] To clarify the operation of the sensor 2 or the internal combustion engine 1, Fig. 2, a single cylinder 21 of the internal combustion engine 1 is shown schematically again. The internal combustion engine 1 has a cylinder 21 with a piston 22 arranged therein. The piston 22 and the cylinder 21 form a combustion chamber 20, into which fuel and air are introduced for the combustion processes of the internal combustion engine 1. The necessary actuators, such as air intake valves and air outlet valves and a corresponding fuel injection, are shown in the Fig. 2 not shown. Due to the combustion processes, the pressure in the combustion chamber 20 is periodically increased and converted into mechanical work by a movement of the piston 22 along the direction of movement 23 through a connecting rod on a crankshaft of the internal combustion engine. The up and down movement of the piston 22 is thus converted into a rotary movement of the crankshaft. In the case of multiple cylinders, the crankshaft is driven by several cylinders. The rotational axis of the crankshaft is always perpendicular to the direction of movement 22 of the pistons. This is a conventional Otto internal combustion engine. Depending on the pressure conditions in the combustion chamber 20, a superficial deformation of the cylinder 21 occurs, which is measurable by the sensor element 2 on an outer surface of the cylinder 21. In the Fig. 2, the sensor 2 is shown on an outer surface of the cylinder 21. Preferably, the sensor 2 is arranged in an area where the deformation of the cylinder 21 is particularly severe due to the pressure increase in the combustion chamber 20. Depending on the design details of the internal combustion engine 1, a suitable location on the surface of the internal combustion engine 1 must be determined empirically.

[0007] In the Fig. 2 shows a sensor 2 which consists of a two-part housing with a base plate 24 and a cover 25. A strain gauge element 26, which is preferably designed as a piezo element 26, is arranged on the base plate 24. The base plate 24 in turn is connected to the surface of the internal combustion engine 1, in particular to an outer surface of the cylinder 21. In typical Otto internal combustion engines with multiple cylinders 21, these multiple cylinders are typically designed as a cylinder block, i.e. as a one-piece metal block in which multiple cylinders are provided. This makes it possible to measure the signals of multiple cylinders using a single sensor. Even with individual cylinders, the cylinder 21 is also realized by a cylinder block, i.e. by a continuous metal workpiece.The sensor's location on the outer surface of the cylinder block ensures reliable detection of cylinder block surface deformations. Designing the cylinder block as a single, continuous metallic workpiece translates pressure increases in the combustion chamber of the internal combustion engine into easily detectable deformations of the cylinder block's outer surface.

[0008] The housing of the sensor 2 is attached to the surface of the internal combustion engine using suitable joining techniques that ensure the transfer of surface deformations to the actual measuring element 26. Adhesive bonding or screw fastening have proven particularly suitable.

[0009] In the Fig. 2, the direction of movement of the piston 22 in the cylinder 21 is represented by the arrow 23. It has been found that the deformations of the surface of the internal combustion engine 1 perpendicular to the direction of movement 23 of the piston 22, i.e. parallel to the rotational axis of the crankshaft, are relatively strong on the surface of the internal combustion engine. Furthermore, sensors for measuring deformations can have a preferred measuring direction. For this purpose, the measuring element 26 can, for example, be designed as an elongated strip, and the greatest sensitivity for deformations is accordingly along the longest extent of this strip. The sensor element as shown in the Fig. 2, is significantly longer parallel to the rotational axis of the crankshaft of the internal combustion engine 1 than in the two directions perpendicular to it. Fig.The sensor element shown in Figure 2 thus has the greatest sensitivity parallel to the rotational axis of the crankshaft, and the deformation is particularly pronounced in this direction. This arrangement of the measuring element 26 or sensor 2, with its measuring direction parallel to the rotational axis of the crankshaft, ensures optimal measurement of the deformation of the internal combustion engine 1.

[0010] The deformation of the surface of the internal combustion engine 1 is suitable for providing a variety of information about the combustion processes in the internal combustion engine 1. This allows the pressure conditions in the combustion chamber 20 to be analyzed during the combustion process. Abnormal combustion processes, such as knocking, combustion misfires, and pre-ignition, can be detected. This allows the quality of combustion or the health of the internal combustion engine to be assessed. Furthermore, combustion can be continuously monitored and appropriate control or regulation interventions can be performed. Overall, the quality of combustion in the internal combustion engine 1 is thus improved.

[0011] A particularly advantageous feature is that such a sensor for measuring the deformation of the surface of the internal combustion engine allows for a very favorable frequency range for measurement. This allows for the evaluation of deformations in a frequency range from greater than 0.5 Hz to several tens of kHz. The low frequency range, in particular, cannot be measured with the acceleration sensors commonly used for combustion analysis. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 100 18 265 B4

[0001] Cited non-patent literature

[0000] Amirante, R., Casavola, C., Distaso, E., and Tamburrano, P., „Towards the Development of the In-Cylinder Pressure Measurement Based on the Strain Gauge Technique for Internal Combustion Engines,“ SAE Technical Paper 2015-24-2419, 2015, doi:10.4271 / 2015-24-2419

[0001]

Claims

[1] Device for measuring combustion processes in an internal combustion engine (1), with a sensor (2) which is attached to a surface of the internal combustion engine, characterized by that the sensor is designed to measure deformations of the surface of the internal combustion engine which are generated by combustion processes in the internal combustion engine. [2] Device according to claim 1, characterized by that the sensor is designed as a strain gauge in a housing. [3] Device according to one of the preceding claims, characterized by that the surface is an outer side of a cylinder block of the internal combustion engine. [4] Device according to claim 1 to 3, characterized by that the sensor was attached by gluing. [5] Device according to claim 1 to 3, characterized by that the sensor is attached using screws. [6] Device according to one of the preceding claims, characterized by that the sensor has a measuring direction and that the measuring direction is parallel to the rotational axis of a crankshaft of the internal combustion engine. [7] Device according to one of the preceding claims, characterized by that the sensor has a measuring range for frequencies from 0.5 Hz to more than 10 Khz. [8] Device according to one of the preceding claims, characterized by that the sensor has a piezo element as a measuring element. [9] Device according to one of the preceding claims, characterized by that the sensor signals are evaluated by evaluation electronics and used to control the internal combustion engine. [10] Method for measuring combustion processes in an internal combustion engine, with a sensor which is attached to a surface of the internal combustion engine, characterized bythat the sensor measures deformations of the surface of the internal combustion engine that are generated by combustion processes in the internal combustion engine.

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