WO1992019947A1

WO1992019947A1 - Process and device for detecting knocking combustion in an internal combustion engine

Info

Publication number: WO1992019947A1
Application number: PCT/DE1992/000246
Authority: WO
Inventors: Bernhard Mencher; Michael Froeschle
Original assignee: Robert Bosch Gmbh
Priority date: 1991-04-24
Filing date: 1992-03-26
Publication date: 1992-11-12
Also published as: DE4113290A1

Abstract

The proposal is for a process for detecting knocking combustion in an internal combustion engine implemented with the aid of a knock sensor and a reference mark on the engines crankshaft. In the process, on the assessment of signals from the knock sensor, knock signals are allocated to certain groups of cylinders of the internal combustion engine with the aid of the aforementioned reference mark and various knock recognition factors for the individual groups of cylinders are used by means of which knocking combustion can be distinguished from non-knocking combustion within a group of cylinders.

Description

Method and device for detecting knocking combustion in an internal combustion engine

State of the art

The invention relates to a method and a device for detecting knocking combustion in an internal combustion engine according to the preamble of claim 1 or according to the preamble of claim 9.

It is known to detect knocking combustion in the cylinders of an internal combustion engine with the aid of knock sensors. In order to be able to assign signals of the knock sensor that may appear during operation of the internal combustion engine to a specific cylinder, for example, a known cylinder Linder detection or a phase sensor used. As a result, the known methods are relatively complex and cost-intensive.

Advantages of the invention

In contrast, the method according to the invention and the device according to the present invention for detecting knocking combustion in an internal combustion engine have the advantage that the detection reliability of knocking combustion can be carried out with high accuracy even without cylinder detection or phase sensor, so that a simple procedure or a relatively simple device for detecting knocking combustion, the non-detection of knocking burns and false detections can be excluded with a high degree of certainty.

This is achieved in a method with the features according to claim 1 in that the cylinders of the internal combustion engine are divided into groups to which various knock detection factors are assigned. When evaluating the signals of a knock sensor, knocking combustion within a group of cylinders can be distinguished from non-knocking combustion on the basis of the different knock detection factors. The method is characterized in that it is very simple and therefore inexpensive to implement. In addition, errors in the detection of knocking combustion can be reduced to a minimum. In a preferred embodiment of the method, the different knock detection factors of the different cylinder groups are specified as a fixed value or determined on the basis of a characteristic curve or a characteristic diagram. As a result, the different knock detection factors can be made available in a simple manner for the detection of knocking combustion.

In addition, an embodiment of the method is preferred in which the inner and outer cylinders of an internal combustion engine with four cylinders arranged in series are combined to form a group. The knock detection factors of the inner and outer cylinder groups can be distinguished without any particular effort, so that the method for knock detection can be implemented simply and inexpensively.

In addition, an embodiment of the method is preferred in which an assignment is generated on the crankshaft with the aid of the reference mark, on the basis of which the output signals of the knock sensor can be distinguished between the individual groups of cylinders of the internal combustion engine. Due to the fact that such reference signals are present in most engine control units, the assignment of the output signals of the knock sensor to the individual cylinder groups can be implemented particularly easily.

An embodiment of the method, which is characterized in that in order to distinguish knocking combustion from non-knocking combustion of the inner and outer groups of two cylinders of the internal combustion engine as knockers. characteristic factor the different useful / noise ratio is used for the output signal of the knock sensor is particularly preferred. The knock detection factor can be determined in this way in a simple manner, so that the method can be carried out inexpensively.

In addition, an embodiment of the method is preferred in which a so-called measurement window is generated as a function of the crankshaft position, within which the distinction between knocking and non-knocking combustion is made. By specifying such a measurement window, measurement errors can be reduced to a minimum without the circuit complexity for implementing the method being significantly increased.

Furthermore, an embodiment of the method is preferred in which the knock sensor is arranged essentially symmetrically to the defined groups of cylinders. In this way, different knock detection factors can be determined, so that the method can be carried out relatively easily.

Finally, a method is preferred in which the knock sensor is arranged approximately in the middle of the four cylinders of an internal combustion engine arranged in series. In such an implementation of the method, the arrangement of the knock sensor is relatively uncritical. It can be adapted to the spatial conditions of the internal combustion engine without slight deviations in the arrangement leading to measurement errors. The advantages mentioned also result in a device with the features of claim 9. Because a knock signal evaluation circuit is provided, with which the output signals of the knock sensor are processed, and a comparator circuit is provided, which outputs the output signals of the knock signal evaluation circuit processed taking into account a knock detection factor and emits a knock signal in the event of knocking combustion, a simple circuit for knock detection of an internal combustion engine is provided which can be implemented inexpensively and can be operated relatively reliably.

Further configurations of the device result from the remaining subclaims.

Finally, the advantages mentioned can also be achieved in that the said device is used as part of an engine control unit of an internal combustion engine, in particular influencing the ignition and / or the injection of the internal combustion engine. Such an integration of the device into an engine control unit means a space-saving and therefore inexpensive implementation of the device, while at the same time providing high functional reliability.

drawing

The invention is explained in more detail below with reference to the drawing. Show it: 1 shows a schematic diagram from which the ignition sequence of an internal combustion engine with four cylinders can be seen;

FIG. 2 shows a rough functional sketch of an internal combustion engine with four cylinders connected in series;

FIG. 3 shows a schematic diagram of an internal combustion engine with an electronic control device, which includes the device for detecting knocking combustion;

FIG. 4 shows a basic circuit diagram of a knock sensor with a downstream control circuit and

Figure 5 is a diagram illustrating the implementation of the method for detecting knocking combustion.

Description of the embodiments

The method or the device for detecting knocking combustion in an internal combustion engine can in principle be used with all engines which have a plurality of cylinder groups with a distinguishable knock detection factor. The method and the device are particularly preferably used in four-cylinder engines, the cylinders of which can be combined in two groups: two outer and two inner cylinders. It is essential for the method that the ignition of the cylinders is selected such that cylinders of different groups are always supplied with an ignition spark one after the other. For example, the firing sequence 1-3-4-2 or 1-2-4-3 that is common in four-cylinder engines can be used. A prerequisite for carrying out the method is a reference mark on the crankshaft, so that its position in relation to a fixed system can be detected, for example with a sensor.

The ignition sequence mentioned is reproduced in FIG. 1 in a diagram in which the detection of the reference mark on the crankshaft is indicated in an uppermost graph by individual pulses. There is a 360 ° rotation of the cube shaft between two pulses.

In the graph below, the firing event of a cylinder is indicated by a continuous line, which is indicated by downward-pointing pulses and symbolized lightning bolts. The closing and opening process of an ignition coil is to be indicated by the negative impulses.

Below this graph, numbers indicate which of the four cylinders of the internal combustion engine is addressed during the respective ignition process, the usual firing sequence 1-3-4-2 or 1-2- 4-3 being indicated by two rows of numbers one above the other.

FIG. 2 shows, roughly schematically, an internal combustion engine with four cylinders arranged in series, the associated numbers 1, 2, 3 and 4 of which are reproduced. are given. The sketch shows the radiator fan on the left and the output of the internal combustion engine on the right. A knock sensor K is indicated by a dot in the middle of the four cylinders.

By looking at FIGS. 1 and 2, it can be seen which of the four cylinders of the internal combustion engine according to FIG. 2 is controlled in the ignition process outlined in FIG. 1.

3 also shows an internal combustion engine 10 with four cylinders arranged in series, the spark plugs ZI to Z4 of which are sketched. In the middle between the cylinders 1 to 4 assigned to the spark plugs ZI to Z4, a knock sensor K is again drawn, which is connected to an engine control unit 20 via a line I--.

The internal combustion engine 10 is also provided with a sensor that detects the speed of the internal combustion engine, a speed sensor DG, which is connected to the engine control unit 20 via an associated line.

The sketch according to FIG. 3 also indicates that the engine control unit 20 is supplied with further information, for example about the load, the temperature or about the supply voltage U _{BATT of} the system.

The engine control unit 20 outputs control signals to the ignition and to the injection of the internal combustion engine as output signals. For details of the otherwise known functions of the engine control devices need not be discussed further here.

The engine control unit 20 comprises a knock signal evaluation circuit KSA, to which the output signals of the knock sensor K are fed via the line 1 ~ r. In addition, the engine control unit includes a microprocessor μC, which serves as a central control unit. The above-mentioned additional signals such as load, temperature and supply voltage are fed to an A / D converter 22 which also receives the output signals of the knock signal evaluation circuit KSA. Output signals of the A / D converter 22 are output to the central microprocessor μC. Its output signals are emitted via a suitable output stage circuit E to each of the lines assigned to the ignition Z or injection E.

Individual elements, which are also shown in FIG. 3, are reproduced in greater detail from the functional sketch according to FIG. 4, so that the processing of the signals can be seen more clearly.

The output signals of knock sensor K are output via line ^ to knock signal evaluation circuit KSA, which has an amplifier V, a filter F, a rectifier G and an integrator I. The output signals of the knock sensor are processed by the individual elements connected in series. The knock signal evaluation circuit KSA is connected via a line M to the microprocessor μC of the motor control circuit 20 shown in FIG. The output signals of the knock signal evaluation circuit KSA are fed via a line L _{A to} the A / D converter 22 which, after processing the signals, forwards them to the microprocessor μC.

The microprocessor μC has a cylinder evaluation circuit or cylinder assignment circuit 30 which assigns the output signals of the A / D converter to the cylinder 1, 2, 3 or 4 of the internal combustion engine (see FIG. 3). The assignment of the signals to the individual cylinders can be seen from the output lines of the cylinder assignment circuit 30 identified by the numbers ^* 1-, -2-, * 3 * and ^» 4 ¹ .

Circuit elements 31 and 32 arranged downstream of the cylinder assignment circuit determine the current value of the knock sensor and the mean value of the output signal of the knock sensor, taking previous work cycles into account. The output signals of these two circuits 31 and 32 are fed to a comparator circuit 33 which compares these two values with one another.

In this comparison, the knock detection factors that are stored in a memory 34 are taken into account. The comparator or comparator circuit 33 has four output lines assigned to the cylinders 1, 2, 3 and 4, which are identified in FIG. 4 by the corresponding numbers of the cylinders. On the basis of the signals appearing on these lines, a distinction can be made as to whether knocking or non-knocking combustion of the cylinder assigned to the respective line has taken place. In FIG. 4, it is assumed that knocking combustion of cylinder 1 was determined on the basis of the signal detected by knock sensor K. The output of the comparator 33, which is assigned to the cylinder 1, is therefore indicated by a large arrow, while the other outputs have an arrow shown in the normal manner.

Based on the detection of knocking combustion via line Z, the microprocessor μC sends a corresponding signal to the ignition output stage 35, which then, marked by a broad arrow, influences the ignition of the cylinder 1 accordingly.

Via the line M of the microprocessor μC, the integrator I of the knock signal evaluation circuit KSA is acted upon by a measurement window signal, that is to say the integration of the input signal takes place only during a predetermined range of a crankshaft angle. The output signal of the knock signal evaluation circuit KSA is output to the A / D converter 22 via the line L _A and the digitized value of μC is requested at a defined time. In this way, knock detection interference is reduced to a minimum.

The implementation of the method and the function of the device can be derived from the diagram according to FIG.

The processed output signal of the speed sensor DG (see FIG. 3) of the internal combustion engine 10 is at the very top of the illustration in FIG. or a so-called tooth signal.

Below this, a reference mark signal t _{R is} indicated, which has individual pulses and represents the position of the crankshaft. This reference mark signal is generated in the usual way, for example by the engine control unit 20.

In the graph below, M denotes the measurement window signal sketched on line M shown in FIG. 4, which ultimately serves to evaluate the output signal of knock sensor K.

In FIG. 5 it is also indicated by horizontal arrows which of the two groups of cylinders of the internal combustion engine is taken into account in the current evaluation of the output signal of knock sensor K. The output signals of the knock sensor are evaluated with an arrow marked with an for the outer cylinder group and with an arrow marked with i for the inner cylinder group. According to FIG. 2 it can be seen that cylinders 1 and 4 are to be assigned to the outer group of cylinders and cylinders 2 and 3 to the inner group of cylinders.

Finally, symbolized by rectangles in FIG. 5, the knock detection factor referred to here as the K factor is used during a measurement window for the determination of knocking or non-knocking combustion. It can be seen that in the area in which the measuring window for the outer group of cycles is activated, the knock detection factors for the cylinders 1 and 4 are activated, while when the measurement window for the group of the inner cylinders 2 and 3 is activated, the knock detection factors for these cylinders 2 and 3 are used.

Overall, it can be seen that the reference mark signals t _{R appear} after every 180 ° KW, so that a full crankshaft revolution of 360 ° has taken place after two t _R pulses.

Overall, the following is to be noted for carrying out the method and for the function of the device shown:

Even without the usual measures for cylinder detection or without a phase sensor, knocking combustions can be detected with a high degree of detection reliability in the internal combustion engine mentioned here. The fact that two cylinders are combined for knock detection makes the method very simple and therefore inexpensive to implement. Different knock detection factors are assigned to the two cylinder groups and are stored in the suitable memory 34 according to FIG. 4 as a fixed value, characteristic curve or as a characteristic diagram.

The only prerequisite for carrying out the method or the function of the device is that the crankshaft has a reference mark and the sequence of the firings of the cylinders of the internal combustion engine has the firing sequence shown in FIG. 1. Each time alternately cylinders of the different groups are ignited.

With the aid of suitable software in the engine control unit, the outer and inner cylinders can be selected with the reference mark on the crankshaft. When evaluating the output signals of knock sensor K, different knock detection factors are assigned to the outer and inner cylinders, the useful / noise ratio in the knock sensor signal being different between knocking combustion between the outer and inner cylinders, provided the sensor is approximately in the middle is arranged between the second and third cylinders (see FIGS. 2 and 3).

Because of the described method and the function of the device shown, the detection reliability of knocking combustion is increased to such an extent that compromises are made between unrecognized knocking combustion, which may lead to engine damage, and between incorrect detection of knocking combustion, which leads to torque - or cause loss of power of the internal combustion engine, does not need to go in. All cylinders can be operated hard at the knock limit, so that there is a relatively low fuel consumption and a higher torque and ultimately a higher performance of the internal combustion engine.

Claims

Expectations

1. A method for detecting knocking combustion in an internal combustion engine with the aid of a knock sensor and with a reference mark on the crankshaft of the internal combustion engine, characterized in that an assignment is used when evaluating signals of the knock sensor with the reference mark knock signals for certain groups of cylinders of the internal combustion engine, and that different knock detection factors are used for the individual groups of cylinders, on the basis of which a knocking combustion is distinguished from a non-knocking combustion within a group of cylinders.

2. The method according to claim 1, characterized in that the different knock detection factors of the different groups of cylinders are predetermined as a fixed value or are determined on the basis of a characteristic curve or by means of a characteristic diagram.

3. The method according to claim 1 or 2, characterized ge indicates that the inner and outer cylinders of an internal combustion engine with four cylinders arranged in a row are combined to form a group.

4. The method according to any one of claims 1 to 3, characterized in that an assignment is generated with the aid of the reference mark on the crankshaft, on the basis of which the output signals of the knock sensor can be distinguished between the individual groups of cylinders of the internal combustion engine.

5. The method according to claim 4, characterized gekennzeich¬ net that to differentiate a knocking combustion from a non-knocking combustion of the inner and the outer group of two cylinders of the internal combustion engine as a knocking detection factor, the different useful / noise ratio in the output signal of Knock sensor is used.

6. The method according to any one of claims 1 to 5, da¬ characterized in that a measurement window is generated depending on the crankshaft position, within which the distinction between knocking and non-knocking combustion is made.

7. The method according to any one of claims 1 to 6, characterized in that the knock sensor is arranged substantially symmetrically to the defined groups of the cylinders of the internal combustion engine.

8. The method according to claim 7, characterized gekennzeich¬ net that the knock sensor is arranged approximately in the middle of the four cylinders arranged in series of the internal combustion engine.

9. Device for detecting knocking combustion in an internal combustion engine with the aid of a knock sensor and a reference mark on the crankshaft of the internal combustion engine, characterized by a knock signal evaluation circuit (KSA), with which the output signals of the knock sensor (K) are processed, and by a Comparator circuit (33) which processes the output signals of the knock signal evaluation circuit taking into account a knock detection factor stored in a memory (34) and emits a knock signal in the event of knocking combustion.

10. The device according to claim 9, characterized gekenn¬ characterized in that the output signals of the Komparator¬ circuit (33) a motor control switching device (20) can be fed.

11. The device according to claim 9 or 10, characterized in that the knock sensor (K) is arranged approximately symmetrically to the cylinders (1, 2, 3, 4) of the internal combustion engine (10) lying in series.

12. Device according to one of claims 9 to 11, characterized in that the knock sensor (K) is arranged approximately in the middle of the four cylinders (1, 2, 3, 4) of the internal combustion engine (10) arranged in series.

13. Use of a device according to one of claims 9 or 12 as part of an engine control unit of an internal combustion engine, which in particular influences the ignition and / or injection of the internal combustion engine.