DE10260012A1 - Piston knocking avoidance method for an internal combustion engine in which evaluation and comparison units are used with measured and calculated parameters to determine a knocking tendency and thus prevent it - Google Patents

Abstract

Method for avoiding piston knocking in a combustion engine has the following steps: a data evaluation unit uses sensor measurements and or computer calculated operating parameters to calculate mixture parameters; the parameters are compared with reference values; and engine operation is adjusted to maximize combustion and performance without any risk of knocking occurring.

Description

The invention relates to a method to avoid knocking combustion in an Otto engine with the Features mentioned in the preamble of patent claim 1.

It is previously known to lower of fuel consumption and to increase engine torque Otto engines high compression ratios are needed. With increasing compression ratios there is a risk of explosive, knocking combustion of the air-fuel mixture, which has an increased thermal and mechanical Load on the engine. The knock limit of an Otto engine is mainly from Compression ratio the shape of the combustion chamber, deposits in the combustion chamber, fuel quality, mixture composition and the engine temperature. To achieve a high degree of efficiency, the motor Center of combustion at 8 ° KWnOT or as close as possible operated at the knock limit.

From the DE 195 18 394 C2 A method for avoiding knocking combustion in a gasoline engine is previously known, in which the ignition timing of the individual cylinders is controlled in accordance with a map stored in the control device as a function of operating parameters of the engine. A knock control acts in parallel to map the ignition timing, which adjusts the ignition timing late when a knock signal determined by a knock sensor exceeds a reference signal dependent on the engine speed.

From the DE 34 19 727 A1 a method for knock control of internal combustion engines is also known. In this case, a manipulated variable is formed from a knock message and the content of a stored characteristic map, with which the ignition timing of the engine is retarded to eliminate knocking. The map is changeable and depends on the previous operating parameters and at least one current operating parameter of the internal combustion engine.

In the known methods for knock control Countermeasures are only taken by internal combustion engines if the Knock sensor knocking after the downstream signal evaluation Combustion was detected. The engine control unit becomes safe and strong effective measures to prevent the knocking combustion and thus to protect the Motors initiated. By shifting the ignition timing towards late to avoid The knocking combustion increases the efficiency of the engine reduced. The engine is subsequently gradually changed by changing the Operating parameters brought back to the knock limit and only then will it be effective again.

Another disadvantage of the designs according to the known State of the art is that the sensory determined Vibrations to detect knocking combustion by mechanical Vibrations caused, for example, by the gas exchange valves are overlaid and thus the reliable detection of knocking combustion difficult. By the usual Using only two or one knock sensor per cylinder bank the detection of the knocking combustion is uncertain. It can, if necessary Failure of detection in entire map areas or individual Cylinders come. As a result, the individual cylinders cannot be attached securely the knock limit led become. The efficiency of the engine is not used effectively or there is knocking combustion, which can lead to engine damage.

The invention is based on the object generic method to avoid knocking combustion in an Otto engine, in which the individual cylinders of the engine with high efficiency of the engine precisely the knock limit led become. Already a possible one knocking combustion is said to be in the development or change phase recognized and prevented by influencing the operating parameters become.

This object is achieved according to the invention in a generic method by the characterizing features of the claim 1 solved.

According to the invention, the engine control unit can already then the combustion can be influenced if still there is no knocking combustion. Here, in a data evaluation device from the sensed and / or calculated in the engine control unit Operating parameters of the engine, the parameters for the mixture charge to be supplied to the cylinder space is determined and from these is stored with the help of the engine control unit Maps of the knocking combustion a value for the knocking Combustion predicted. By modeling the filling condition in the cylinder chamber can depend on the boundary conditions of knocking combustion getting closed. The determined knocking tendency is compared with the Test determined characteristic curves and stored in the engine control unit Maps of the knocking combustion compared. In engine operation the review of the Model using a known knock sensor, with a Data evaluation device an adaptation to the real engine condition he follows.

By pre-calculating the knocking combustion, it can be estimated whether the Mo gate parameters must be carried out, or whether the knocking limit can be accepted at short notice. This makes it possible to intercept engine status-dependent detection problems using the model approaches, in order to avoid deterioration in efficiency as a result of unwanted ignition adjustment or engine damage due to the non-detection of knocking phenomena that occur.

In addition, the solution according to the invention also rapidly changing combustion processes immediately recognized so that time delays be avoided in the regulation. The ignition can be more precise Efficiency oriented, regulated. With that the Reduced fuel consumption, optimized engine torque and the Probability of engine damage lowered.

By precisely operating the engine on the Knock limits are also measures to avoid the formation of deposits and thus for long-term maintenance optimal efficiency possible.

Another advantage of the solution according to the invention is in that there is only one knock sensor to compare the calculated Knock limit with that actually knocking required becomes. In addition to saving additional knock sensors and the corresponding components in the control unit also a reduction in Development effort.

Further advantageous configurations are in the subclaims They are described in the description along with their effects explained.

Based on a drawing, a embodiment described the invention. In the accompanying drawing is schematic a flow chart to avoid knocking combustion shown an Otto engine.

In the drawing, 1 shows the engine combustion that takes place in a gasoline engine known per se. The operating parameters of engine combustion are set by means of an engine control unit (not shown). In the method according to the invention for avoiding knocking combustion in a data evaluation device 3 , which can also be part of the engine control unit, from the operating parameters determined by sensor and / or computer in the engine control unit 2 of the engine determines the parameters for the mixture charge to be supplied to the cylinder space for the respective combustion. The calculated parameters of the mixture charge supplied to the combustion are compared with a map of the knocking combustion stored in the engine control unit. The characteristic map of knocking combustion stored in the engine control unit for each engine type is determined specifically in the test. A current value for knocking combustion is determined from the comparison of the calculated parameters with the map stored in the engine control unit, from which the boundary conditions for a knock tendency are determined 6 can be closed. This value is saved as a characteristic curve in the engine control unit in accordance with the respective operating conditions.

Based on the predicted value of knocking combustion 6 and the characteristic curves stored in the engine control unit are controlled by the knock control 4 the operating parameters are set via the engine control unit such that effective combustion occurs close below the knock limit. This is done via a continuous ignition angle correction 5 or a mixture adjustment, not shown. The continuous correction of the operating parameters through the knock control 4 leads to a harmonization of the torque curve. Even with high load and speed gradients, the parameterization of the motor is carried out by the precise modeling so that knocking is reliably avoided.

If the determined value of knocking combustion 6 Motor combustion occurs in the normal knocking range 1 at a basic ignition angle. Knows the determined knock value 6 If the knocking tendency is reduced, the ignition angle is set to advance, while if the knocking tendency is determined to be higher 6 the ignition angle is retarded. The ignition angle is adjusted via the knock control 4 by means of the ignition angle setting 5 ,

A well-known structure-borne noise sensor 7 provides data on the real knock tendency of engine combustion 1 , In the work area with a high useful signal, the knock control 4 the predicted value of the expected knock tendency 6 with the determined values of the knock sensor 7 compared.

When exceeding or falling below the The knock limit is corrected by the pre-calculated values Adaptation of the model to the current boundary conditions. The model comparison is in the engine control unit stored as a correction map. The new operating parameters are over the Engine control unit based on the corrected values.

The structure-borne noise sensor 7 is arranged such that it reliably determines the data of all cylinders at at least one map point that can be selected individually for the cylinder.

Adaptation maps are in the engine control unit for different Fuel qualities and compression ratios also for Engine condition changes stored and are immediately available in subsequent combustion cycles to disposal. A suitable software enables timely adaptation of the model to the current conditions without disadvantages for the engine torque expected by the driver.

• – Zündzeitpunkt α_z
• – Kolbengeschwindigkeit ν_K ~ Motordrehgeschwindigkeit
• – Luft/Kraftstoff-Verhältnis λ
• – Körperschall der Zylinder
• – Kühlmitteltemperatur am Austritt t_mot
• – AGR-Ventilposition
• – Ansauglufttemperatur t_ans

die Festwerte:

• – Wärmewert der Zündkerze
• – Verdichtungsverhältnis ε
• – Gemischhomogenität γ
• – Kraftstoffkonstanten

die bekannten Rechengrößen:

• – Luftmasse m_Luft
• – Einlasstemperatur t_EE
• – Restgasgehalt β_AGR
• – Abgasrückführungsrate

The operating parameters used to determine the knocking combustion
the measured values:

• - Ignition timing α _z
• - Piston speed ν _K ~ engine speed
• - Air / fuel ratio λ
• - Structure-borne noise from the cylinders
• - Coolant temperature at the outlet t _mot
• - EGR valve position
• - Intake air temperature t _ans

the fixed values:

• - heat value of the spark plug
• - compression ratio ε
• - Mix homogeneity γ
• - fuel constants

the known arithmetic variables:

• - _Air mass m _air
• - inlet temperature t _EE
• - Residual gas content β _EGR
• - EGR rate

1

motorized combustion

2

operating parameters

3

Data evaluation unit

4

knock control

5

ignition angle

6

knocking combustion

7

Acoustic emission sensor

Claims (8)

Method for avoiding knocking combustion in an Otto engine, in which - the sensors' operating parameters are recorded and stored in a control unit, - a knock signal from the engine is recorded by sensors and compared with a map of the permissible knock limit stored in the control unit, the ignition timing of each cylinder is controlled stored characteristic field in accordance with a in a control unit in dependence on operating parameters and the knock limit of the engine, characterized in that - detected by sensors in a data evaluation device from and / or constructed in the engine control device operating parameters of the engine, the parameters for the the mixture charge to be supplied to the cylinder space for the respective combustion are determined, - the determined parameters are compared with a map of the knocking combustion stored in the engine control unit, from which a value for an expected one Knocking tendency is calculated in advance and stored as a characteristic curve in the engine control unit, - on the basis of the comparison of the calculated value of the knocking combustion and the characteristic curve stored in the engine control unit, the operating parameters are set via the engine control unit in such a way that effective combustion occurs close to the knock limit, - in the data evaluation device of the predicted one The value of the expected knock tendency is compared with the determined values of a knock sensor and the pre-calculated value is corrected if the knock limit is exceeded or undershot, - the corrected values are stored in the data evaluation device and the engine control unit as a correction map and the operating parameters via the engine control unit based on the corrected values can be set. A method according to claim 1, characterized in that in the engine control unit Adaptation maps for different fuel qualities and compression ratios also for Engine condition changes are filed. Method according to one or more of the previous ones Expectations, characterized in that the knock sensor the data of all Cylinder at at least one map point that can be selected individually for the cylinder reliable determined. A method according to claim 3, characterized in that based on the sensor data a correction of the predicted Values are made by adapting the model to the current boundary conditions. Method according to one or more of the previous ones Expectations, characterized in that for every cylinder of the engine continuously a value of the expected Knock tendency in the data evaluation device determined and for everyone Cylinder set an effective combustion near the knock limit becomes. Method according to one or more of the previous ones Expectations, characterized in that for motor-specific adjustment determined data stored as characteristic curves and maps in the engine control unit become. Method according to one or more of the previous ones Expectations, characterized in that to harmonize the torque curve the knock control continuously corrects the operating parameters become. Method according to one or more of the previous ones Expectations, characterized in that with high load and speed gradients the parameterization of the motor is done by precise modeling, that knocking is safely avoided.