KR100462459B1 - Abnormal combustion process detection method of multi-cylinder diesel internal combustion engine - Google Patents

Abstract

By recording the noise in each cylinder by one or more structure-generated noise sensors and checking whether the sensor signal exceeds the individual thresholds for each cylinder inside or outside the fixed measuring window, abnormal injection and spraying can be detected. Can be.

Description

Detection method of abnormal combustion process of multi-cylinder diesel internal combustion engine

The present invention relates to a method for detecting abnormal combustion processes in a multicylinder diesel internal combustion engine by evaluating the noise of combustion by a structure-borne noise sensor.

Injection systems in diesel internal combustion engines have the ability to introduce as finely atomized fuel as possible into the combustion space in a very short time. Higher injection pressures result in better mixture formation, resulting in lower fuel consumption and soot emissions. The currently developed injection system, called the common-rail system, operates at injection pressures up to 1500 bar, and its basic configuration is an electronic control unit with a high pressure pump, accumulator, injector and the necessary sensors. do.

The problem that arises in the injection system, which is operated individually for each cylinder, is that the operating behavior of the internal combustion engine, in particular the exhaust gas behavior, is due to deactivation due to the absence of flow to multiple injectors, or for example at incorrect times. Is incorrectly affected by incorrect activities.

1 is a diagram showing the characteristic form of combustion noise and pressure inside a cylinder as a function of crank angle,

2 is a process flow diagram for a sequence of methods for determining an abnormal combustion process, and

FIG. 3 shows a measurement chart of the corresponding signals of the cylinder pressure and knock sensors in the case of a four cylinder internal combustion engine.

It is an object of the present invention to provide a method which can detect abnormal combustion in a simple and inexpensive manner due to the absence of combustion or incorrect injection in a multicylinder diesel internal combustion engine.

This object is achieved by the features of the appended claims 1 according to the invention. That is, combustion noise is recorded separately for each cylinder by one or more structure-transmitting noise sensors in a predetermined measurement window MW _{1... Z} , and a separate structure for each cylinder. -The transmission noise signal KS _{1 ... z} is compared with the individual threshold values TV _{1 ... z} assigned to the cylinder Cyl _{1 ... z} and the threshold value TV _1.. in the case where the _.z), greater than the structure-passing noise signals (KS _{1 ... z)} are the threshold values (TV _{1 ... z)} within or outside the measurement windows (MW _{1 ... z)} And if the threshold value TV1 _{... z} is exceeded outside of the measurement window MW _{1 ... z} , inferring that the injection of the injector of the injector is incorrect. Is achieved by. The dependent claims preferably define or add to the invention.

By evaluating the combustion noise in the combustion space of each cylinder by structure-transfer noise analysis, it is possible to detect inadequate combustion processes, for example due to incorrect activity of the injector, and to detect a complete failure of one or more injectors. In particular, measures can be taken to protect the engine if incorrect injection is detected.

Embodiments of the present invention are described below with reference to the accompanying drawings.

1 shows a typical profile of the pressure P _{cy1 in} a cylinder of a diesel internal combustion engine as a function of crank angle. The top dead center is denoted by TDC. The relevant profile of the in-cylinder combustion noise (CN) is indicated by another curve. The generation of such combustion noise is used to detect faulty or missing combustion processes. To this end, the structure-transmitting noise sensor is fixed at an appropriate point in the cylinder block of the internal combustion engine, recording the characteristic knocking vibrations in the combustion chamber of the individual cylinders. The sensor converts this vibration into an electrical signal, which is fed to the electronic engine controller for another process. In this case, a knock sensor, which is an acceleration sensor operating on a piezoelectric principle, can be preferably used as a structure-transfer noise sensor.

Such knock sensors are known, for example, from German Utility Model No. G 87 06 781.1. If only one knock sensor is used, its mounting position should be chosen to be as centered in the engine housing as possible. In the case of internal combustion engines of six, eight or twelve cylinders, two or more knock sensors can be used to improve the accuracy of the evaluation of knock signals from individual cylinders, which are arranged at corresponding points in the engine housing and Constant allocation is made between the cylinder and the cylinder.

The method executed individually for each cylinder is described with reference to the process flow diagram according to FIG. 2.

The noise signal and knocking signal derived therefrom are, for example, a predetermined predetermined measurement window (MW) ranging from 45 ° crank angle before top dead center (TDC) to 15 ° crank angle after top dead center. Within, each cylinder is individually measured and evaluated.

Therefore, in the first step S1 the measurement window MW _{1... Z} is determined as a function of the engine speed n, the load of the internal combustion engine, and the number of cylinders z. Because of the elapsed time of combustion noise from the origin in each cylinder to the detection position by the sensor, the measurement window is recorded in the characteristic map in the storage of the engine control unit individually for each cylinder.

The threshold value TV _{1... Z} is determined as a function of engine speed and load for each cylinder C _{1 .. z} (step S2), and this value is recorded in the storage. In step S3, the noise signal from the structure-transfer noise sensor is recorded, processed (commutated) sequentially, and amplified by an individual signal amplifier of each cylinder (step S4). In this case, the amplification can be changed step by step or continuously. This ensures that the evaluable signal type is useful within a predetermined range under all operating conditions of the internal combustion engine.

In step S5, the individual structure-transmitting noise signal for each cylinder is compared with each relevant threshold value TV _{1... Z} (FIG. 1). If the threshold is exceeded, it is checked whether the signal from the sensor is within the fixed measurement window MW _{1... Z} (step S6). If it is not in the measurement window, it is regarded as an incorrect injection in step S7, and engine protection measures such as, for example, suppression of an operating pulse for this injector or reduction of operation time are started (step S8).

If the signal KS _{1 ... z} recorded by the knock sensor exceeds the threshold TV _{1 ... z} in the measurement window MW _{1 ... z} , this cylinder (Cyl _{1 ..} The combustion in _.z ) is considered normal (step S9). The signals KS _{1... Z} obtained in this way from the knock sensor are used to determine the onset of combustion in each cylinder, and for other control measures such as for example onset of combustion.

If the result of the question of step S5 is that the signal KS _{1 ... z} from the sensor is less than or equal to the threshold TV _{1 ... z} ), then in step S10 the maximum amplification of the sensor signal is already Check for excess. If exceeded, no combustion and injection is considered in step S11. If the maximum amplification of the sensor signal has not been exceeded, steps S4, S5 and S10 are repeated until the threshold is exceeded or the answer to the question in step S10 is positive.

Figure 3 shows a graph taken by measuring in a four-cylinder (Cyl _{1 ... 4} ) internal combustion engine at 1500 rpm. The profile of the cylinder pressure P _{cyl1... 4} and the profile of the associated signal KS _{1 ... 4} from the knock sensor are shown according to the ignition sequence 1-3-4-2.

Claims (9)

In the method for detecting abnormal combustion process of a multi-cylinder diesel internal combustion engine, Combustion noise is recorded for each cylinder individually by one or more structure-transmitting noise sensors in a predetermined measurement window (MW _{1 ... z} ), For each cylinder the individual structure-transfer noise signal Ks _{1 ... z} is compared with the individual thresholds TV _{1 ... z} assigned to the cylinders Cyl _{1 ... z} , When the threshold value TV _{1... Z} is exceeded, the structure-transmitting noise signal KS _{1... Z} is transmitted to the threshold inside or outside the measurement window MW _1. Check that it exceeds (TV _{1 ... z} ), and Abnormal combustion of a multi-cylinder diesel internal combustion engine, which infers that the injection of the injector of the injector is inaccurate when the threshold value TV _{1 ... z} is exceeded outside the measurement window MW _1. Process detection method. 2. The abnormality of a multi-cylinder diesel internal combustion engine according to claim 1, wherein if the threshold value TV _{1 ... z} is exceeded in the measurement window MW _{1 ... z} , it is inferred that combustion is normal. Combustion process detection method. 2. The signal from the structure-carrying noise sensor for each cylinder according to claim 1, before further processing the signals KS1 _{... z} in the engine control system. KS _{1 ... z} ) is individually rectified and amplified, wherein the amplification factor is varied step by step or continuously, detecting abnormal combustion process of a multi-cylinder diesel internal combustion engine. 4. The method according to claim 3, wherein in the case of maximum amplification for each cylinder Cyl _{1 ... z} , the threshold value TV _{1 ... z in} the measurement window MW _{1 ... z} . And a method of detecting an abnormal combustion process of a multi-cylinder diesel internal combustion engine, which infers that there is no injection if the) is not exceeded. 2. A method according to claim 1, comprising initiating engine protection measures such as suppressing an operating pulse or reducing operating time for an injector when incorrect injection is detected. . The abnormal combustion process detection method according to claim 1, wherein an acceleration sensor operating on a piezoelectric principle is used as the structure-transmitting noise sensor. The method of claim 1, wherein the measurement window (MW _{1... Z} ) includes a range from before top dead center to after top dead center. 8. The multicylinder diesel internal combustion engine according to claim 1, comprising recording the measurement window MW _{1... Z} in the characteristic map of the storage of the individual electronic engine control units in each cylinder. Abnormal combustion process detection method. 2. The multicylinder diesel internal combustion engine of claim 1, comprising providing a plurality of structure-transmitting noise sensors and assigning each sensor a particular plurality of cylinders (Cyl _{1 ... z} ) of the internal combustion engine. Abnormal combustion process detection method.