EP0684377A1

EP0684377A1 - Electronic system for identifying the strokes of an internal combustion engine

Info

Publication number: EP0684377A1
Application number: EP95107845A
Authority: EP
Inventors: Roberto Flora; Gabriele Serra
Original assignee: Magneti Marelli SpA
Current assignee: Marelli Europe SpA
Priority date: 1994-05-23
Filing date: 1995-05-22
Publication date: 1995-11-29
Also published as: ITBO940238A1; ITBO940238A0

Abstract

Electronic system for identifying the strokes of a four-stroke internal combustion engine, having an output crankshaft coupled to an angular position sensor which generates a signal having an interval of 360 ° of the crankshaft. The signal has at least one zero reference corresponding to a zero angular reference of the crankshaft. The system can detect (100) the zero reference and arbitrarily assign (110) the strokes of the engine (2) with respect to the zero reference by determining at least one specified angular relation between the zero reference and the angular position in which the upper dead centre of a first cylinder is reached. The system can monitor (133) the torque generated by the engine to detect a timing displacement of 360 in the arbitrarily assigned strokes and retime (135) these strokes as a result.

Description

The present invention relates to an electronic system for identifying the strokes of an internal combustion engine.
There are known electronic injection systems for internal combustion engines in which a microprocessor-based electronic controller receives at its input a plurality of data signals (for example, the engine speed, the throttle position, the intake air temperature, the cooling water temperature, etc.), and generates at its output the injection stroke and time for the different injectors.
Certain electronic injection systems, for example the systems known as "Multipoint" (one injector per cylinder) which are sequential (the fuel is injected into one cylinder at a time) and stroke- dependent (the fuel is injected in the suction stroke) also require angular reference systems permitting the recognition of the engine stroke (suction, compression, expansion, exhaust) in the different cylinders of the engine.
The known angular reference systems use two sensors of the angular position of the engine: a first sensor which can supply a signal of the angular position of the crankshaft (with an interval of 360°) and a second sensor (with an interval of 720_°) which can supply a signal of the angular position of the camshaft.
In particular, the first angular position sensor conveniently consists of a toothed pulley keyed to the crankshaft and a fixed sensor which can supply a pulse at the moment in which one tooth of the pulley passes in front of the fixed sensor. The toothed pulley also has a flattened portion, formed for example by the omission of two teeth, which is used as a zero reference for identifying the upper dead centres of the different cylinders of the engine. In particular, the upper dead centre of each cylinder of the engine is found, with an indeterminacy of 3600, in a specified angular position with respect to the zero reference. The upper dead centres of the different cylinders are therefore identified by counting specified numbers of pulses following the detection of the zero reference.
The second sensor consists of a toothed pulley keyed to the camshaft and a fixed sensor which can supply at its output a first signal level corresponding to a first zero reference detected by the first sensor and a second signal level corresponding to a subsequent detection of the zero reference. The second sensor is used to eliminate the 360 _°indeterminacy of the first sensor.
The known systems also have electronic controllers which receive the signals generated by the first and second sensors and process them to obtain the data on the engine strokes (suction, compression, expansion, exhaust) of the different cylinders.
The known angular reference systems entail a considerable complexity of construction and high costs.
The processing of the signals generated by the two sensors is also complex.
The object of the present invention is to provide an electronic system for identifying the strokes of an internal combustion engine which resolves the problems of the known systems. In particular, the object of the present invention is to provide an electronic system for identifying the strokes of an engine which uses only one angular position sensor.
The above object is achieved by the present invention in that it relates to an electronic system for identifying the strokes of a four-stroke internal combustion engine;

the said engine having an output crankshaft coupled to a sensor of the angular position of the said shaft,
the said sensor generating a signal having an interval of 360 _°of the crankshaft,
the said signal having at least one zero reference corresponding to a zero angular reference of the said crankshaft,
characterized in that it comprises:
- - first electronic means capable of detecting the said zero reference;
- - second electronic means capable of arbitrarily assigning the strokes of the cylinders of the said engine with respect to the said zero reference;
  the said second electronic means determining at least one specified angular relation between the said zero reference and the angular position in which the upper dead centre of a first cylinder is reached;
- - means of monitoring the torque generated by the said engine, capable of detecting an error of 360 _°of the crankshaft in the strokes assigned by the said second electronic means and capable of selecting retiming means to retime the said strokes by 360 °,
  - the said monitoring means also comprising:
  - inhibiting means capable of causing the interruption of the fuel injection in at least one injector;
  - discriminating means capable of measuring the torque applied to the crankshaft by the said first cylinder;
  - the said discriminating means being capable of comparing the said measured torque with reference values, in particular stored values, to detect a lack of application of torque due to a lack of supply in the instant in which the upper dead centre is assumed to be present in the said first cylinder.

The invention will now be illustrated with particular reference to the attached figures, which represent a non-restrictive preferred embodiment, in which

Figure 1 shows an internal combustion engine provided with an electronic system for identifying the strokes, made according to the principles of the present invention; and
Figure 2 is a logical block diagram of the operations performed by the system according to the present invention.

Figure 1 shows a four-stroke internal combustion engine 2 operating in an Otto cycle, provided with an injection device 4 controlled by an electronic controller 7 operating according to the electronic system of stroke identification according to the present invention.
In particular, the electronic controller 7 receives a plurality of signals S1, S2, ... Sn of input data collected in the engine 2 (for example, signals proportional to the engine coolant temperature, to the intake air temperature, to the throttle position, etc.) and generates at the output a plurality of injection times Tj supplied to the injection device 4.
The injection device 4 is provided with four injectors 4a, 4b, 4c, 4d operating with corresponding cylinders 9a, 9b, 9c, 9d (shown schematically) of the engine 2 ("Multipoint" system) and can inject the fuel into one cylinder at a time (sequential system) and in the suction stroke (timed system).
The electronic controller 7 is provided with an engine stroke reference unit 11 permitting recognition of the engine stroke (suction, compression, expansion, exhaust) in each cylinder 9a, 9b, 9c, 9d of the engine 2.
The reference unit 11 receives at its input a signal from a sensor 15 coupled to a toothed pulley 17 keyed to one end of the crankshaft 20 of the engine 2. The sensor 15 can generate an electrical pulse when one tooth of the pulley 17 passes in front of the sensor 15.
The toothed pulley 17 is provided with sixty teeth, with the omission of two, and therefore has a flattened portion formed by the omission of these two teeth, which is used as the zero reference. The zero reference is used to identify the upper dead centres of the different cylinders of the engine. In particular, the upper dead centre of each cylinder 4a, 4b, 4c, 4d is found, with an indeterminacy of 360°, in a specified angular position aa, ab, ac, ad with respect to the zero reference.
The signal R generated by the sensor 15 consists of a sequence of pulses Di equally spaced by an interval t. The signal R also has a flat portion Dz of width T (equal to approximately three times t) in which pulses cannot be detected; this flat portion Dz is produced during the passage of the flattened portion in front of the sensor 15.
The upper dead centre of each cylinder is identified with the said indeterminacy of 360 _°by counting a specified number of pulses Na, Nb, Nc, Nd after the detection of the zero reference.
In particular, when the zero reference is detected it is not possible to identify the timing of the different cylinders 9a, 9b, 9c, 9d in a unique way, since the interval of the engine 2, operating in the Otto cycle, is 720 _°of the rotation of the crankshaft and the interval of the signal generated by the sensor 15 is 360 _°of the rotation of the crankshaft. Consequently it is not possible to know whether the 360 _°following the zero reference coincide with the first 360 _°of the cycle or with the final 360 _°of the engine cycle. It is therefore not possible to know whether the first specified angular position aa following the zero reference corresponds to the upper dead centre of the first cylinder 9a or to that of the fourth cylinder 9d of the engine 2.
The reference unit 11 also interacts with a device 25, for example the device described in French Patent FR-9111273 with the title "process and device for measuring the torque of an internal combustion engine", capable of measuring the instantaneous torque developed individually by the different cylinders of the engine 2.
The unit 11 generates at its output a signal which describes the engine strokes (suction, compression, expansion, exhaust) of each cylinder 9a, 9b, 9c, 9d of the engine 2.
With particular reference to Figure 2, the operations performed by the unit 11 operating according to the system of the present invention will now be illustrated.
The first block encountered is the block 100 in which the system detects the signal R generated by the sensor 15.
In particular, in the block 100 the system is prepared to await the flat portion Dz of the signal R in order to identify the zero reference of the pulley 17. Detection of the zero reference results in a passage from the block 100 to a block 110.
The block 110 arbitrarily assigns the strokes of the engine 2, assigning, for example, the upper dead centre of the first cylinder 9a to the first specified angular position aa following the zero reference; the assignation of the positions of the upper dead centres of the other cylinders is carried out in a way compatible with the first assignation.
In this way, the angular position aa of the upper dead centre of the first cylinder 9a is recognized after detection of a specified number (for example twenty) of pulses Na following the zero reference.
For the reasons stated above, the angular position found on the twentieth pulse following the zero reference may also correspond to the upper dead centre of the fourth cylinder 9d.
In case of error, the operation of the engine is not compromised, since the charge in the ignition coil (not illustrated) and the subsequent spark in the first cylinder 9a and in the fourth cylinder 9d are ensured; the performance of the engine 2 is, however, seriously degraded when incorrect advances of injection and ignition by 360 _°occur.
The block is followed by a block 130 which detects an error in the assignation of the strokes determined by the block 110 (mistiming by 3600) and consequently retimes the injection.
In particular, the block 130 comprises a block 131 which eliminates the fuel injection to an injector, in particular the injector which injects fuel into the first cylinder 9a.
The block 131 is followed by a wait block 132.
The block 132 is followed by a block 133 in which the torque applied to the crankshaft by the cylinder recognized by the block 110 as the first cylinder 9a is measured by a known method by the device 25.
If the assignation of the strokes performed by the block 110 is correct, in other words if the cylinder recognized by the block 110 as the first cylinder is actually the first (and therefore is not the fourth cylinder 9d), the interruption of the supply of the block 131 is followed by a lack of application of torque in the instant in which the upper dead centre is assumed to be present in the said first cylinder.
For this reason, if the interruption of the supply is followed by a decrease in torque in the instant in which the upper dead centre is assumed to be present in the first cylinder, the timing carried out by the block 110 is correct and passes from the block 133 to a block 134. The decrease in torque may be measured, for example, by comparing the instantaneous torque measured by the device 25 with the torque measured in preceding engine cycles.
If, however, the interruption of the supply to the first injector is not followed by a decrease in torque in the instant in which the upper dead centre is assumed to be present in the first cylinder, the timing carried out by the block 110 is incorrect, and passes from the block 133 to a block 135.
The block 135 retimes by 360 the timing set in the block 110; consequently, the upper dead centre of the fourth cylinder 9d (whose position is displaced by 360 _°with respect to that of the first cylinder) is assigned to the first angular position of the shaft 20 following the detection of a specified number of pulses Na (for example, twenty) from the zero reference.
The block 134 maintains the timing determined by the block 110.
The blocks 134 and 135 lead to the exit from the program.
The advantages of the present invention will be clear from the above, since the described system detects the engine strokes precisely although only one angular position sensor is used.
Finally, it will be clear that modifications and variations may be made to the described system without departure from the protected scope of the present invention.

Claims

1. Electronic system for identifying the strokes of a four-stroke internal combustion engine;

the said engine having an output crankshaft (20) coupled to a sensor (15, 17) of the angular position of the said shaft (20),

the said sensor (15, 17) generating a signal (R) having an interval of 360 _°of the crankshaft,

the said signal (R) having at least one zero reference (Dz) corresponding to a zero angular reference of the said crankshaft (20),
characterized in that it comprises:

- first electronic means (100) capable of detecting the said zero reference;

- second electronic means (110) capable of arbitrarily assigning the strokes of the cylinders of the said engine (2) with respect to the said zero reference;
the said second electronic means determining at least one specified angular relation (aa) between the said zero reference and the angular position in which the upper dead centre of a first cylinder is reached;

- means (130) of monitoring the torque generated by the said engine (2), capable of detecting an error of 360 _°of the crankshaft in the strokes assigned by the said second electronic means (110) and capable of selecting retiming means (135) to retime the said strokes by 360 °,

the said monitoring means (130) also comprising:

inhibiting means (131) capable of causing the interruption of the fuel injection in at least one injector;

discriminating means (133) capable of measuring the torque applied to the crankshaft (20) by the said first cylinder;

the said discriminating means (133) being capable of comparing the said measured torque with reference values, in particular stored values, to detect a lack of application of torque due to a lack of supply in the instant in which the upper dead centre is assumed to be present in the said first cylinder.

2. System according to Claim 1, characterized in that the said monitoring means (130) comprise:

timing maintenance means (134) selectable by the said discriminating means when the interruption of supply caused by the said inhibiting means (131) is followed by a lack of application of torque in the instant in which the upper dead centre is assumed to be present in the said first cylinder;

the said timing maintenance means (134) being capable of maintaining the timing determined by the said second electronic means (110).

3. System according to Claim 2, characterized in that the said discriminating means (133) select the said retiming means (135) when the said interruption of supply is not followed by a decrease of torque in the instant in which the upper dead centre is assumed to be present in the said first cylinder.