SE453770B - SET FOR AUTOMATIC CONTROL OF TENDING TIME IN A COMBUSTION ENGINE - Google Patents

Description

15 20 ZS 30 35 40 453 770 value V.

The predetermined value V, as well as the number P or the number Q can be fixed values or a function of at least one parameter related to the engine's operating condition, such as the engine speed, its fuel filling, its noise, the content of pollutants in the exhaust gases, the nature of the carburettor, an engine temperature.

If the engine is equipped with several cylinders and at least one is equipped with means for detecting the phenomenon that characterizes the operating state of the engine, the obtained statistical value is used, which leads to measures in the cylinder provided with such means, even in cylinders which are not are provided with such means for determining a change value for regulating the ignition time also in these.

If the engine has several cylinders, at least two of which are provided with means for detecting the operating condition of the engine, the statistical value from at least one of these cylinders is used to control the ignition time in another cylinder which does not have such means or for such cylinders where the number of valid measured values for said characteristic phenomenon has become less than P during Q cycles.

According to an embodiment of the method according to the invention, if the detecting means are not active in any cylinder provided with detecting means due to the number of measured values being lower than P during Q cycles, the feed can be given a predetermined value. The selected value may be a function of at least one of the parameters determined by the operating condition of the engine, such as the fuel filling, the temperature of the supplied fuel or other characteristic temperatures, various measurable engine pressures, or a function of the carburetor condition or a parameter depending on the accelerator pedal position.

In this case, there will be no reversal of the properties that characterize the combustion and the system can be described as an open control circuit.

The random occurrence of the phenomena which characterize the operating state of the engine may, for example, be due to the fact that, although not exclusively, the phenomenon itself occurs or not, or in the detection and finally to the fact that phenomena which characterize the engine operating state occur at several different angular positions. 10 15 20 ZS 30 35 40 453 770 It is possible according to the invention to check the different detected values as well as the value range for the crankshaft angle in which they have been detected. This is to determine whether the values should be accepted or rejected.

The choice and how strict the criteria for validity should be is left to the person skilled in the art to estimate and it can be more (for example that the detection should occur in a very narrow range) or less difficult (it is enough that detection takes place).

The use of a representative statistical value for the angular positions of the motor shaft, in which the phenomenon characteristic of the engine's operating condition is detected, is due to the fact that one wishes to avoid random errors in the phenomenon one has decided to measure. The value you want to keep is a value that you can describe as "normal" and not an incorrect or an unusual value. This is the reason why it is necessary to use a number of measured values, of course with scatter, in order to derive a value from them that can be said to be normal.

It is understood that the more number of values one has in the statistical quantity from which one derives the representative value, the more one can regard the latter value as normal.

Sometimes, in practice, one is limited by the necessity to avoid a grading of the measured values, during a period which is not representative of the operating condition of the engine, and the selection of useful measured values from the quantity P is too small to establish a normal value, that, as a compromise , make use of the number of P measured values obtained previously, which is sufficient to obtain a good representativeness of the phenomenon and allow the influence of external elements on the phenomenon to be reduced. However, the disruptive effect occurs only during certain cycles.

The statistical value obtained as representative of the amount P of measured values can be the median or the arithmetic, geometric or the quadratic mean value.

The type of representative value you choose depends on the type of phenomenon you are measuring.

The following description shows two kinds of phenomena which characterize the operating state of the engine. The first consists of the maximum pressure in a cylinder, the second consists of the passage of the flame front past a certain point in the combustion chamber. These phenomena have been previously described for a controlled ignition engine in French Patents 2,404,121, 2,432,097, 2,475,640 and in U.S. Patent 4,153,019.

These phenomena also occur in compression-ignition engines and can also be used there to regulate the ignition timing.

These two phenomena characteristic of the engine do not in any way limit the invention, but other phenomena of combustion can also be used in the method according to the invention to automatically regulate the ignition time, for example the phenomenon which occurs in the final phase of combustion and described in French patent 2,466,635.

The present invention thus allows the ignition timing of an internal combustion engine to be regulated on the basis of representative direct information on the operating condition of the engine. Thanks to this closed control circuit, the influence of certain phenomena that occur between the ignition time and the combustion itself will be automatically compensated in cycle after cycle.

Furthermore, since according to the invention it is possible to switch between an open and a closed control circuit, this in order to improve the performance of the motor, it can be used within a wide working range without the switching between the two control modes being noticeable.

In a first embodiment according to the invention, the ignition timing of the combustion is regulated so that, in at least one cylinder, the time of maximum pressure in the cylinder coincides with the passage of the motor shaft past a predetermined angular position.

To indicate the moment when the pressure is greatest, the acceleration of the piston top is measured and a first signal is emitted corresponding to the acceleration.

According to a special embodiment of this method, the first signal is integrated to obtain a second signal, which is zero when the pressure is at its greatest.

According to a second embodiment of this method, the second signal is integrated to obtain a third signal, which is greatest when the pressure is greatest in the cylinder.

Experience has shown that the combustion conditions in the cylinders vary. The determination of the maximum pressure in the various cylinders shows a certain random behavior, the 50111 although this detection does not take place in all the working operations of the engine 10 15 20 25 30 35 4ß s 453 770 cycles, for example because the sensitivity of the detector is not sufficient within the entire measuring range or that the detection is not representative of the function of the cylinder.

Under such conditions, the regulation of the ignition timing of combustion may not be satisfactory. The improved method of the invention overcomes these shortcomings.

According to a second embodiment, the method of controlling the ignition timing of combustion consists in locating the angular position of the motor shaft when the ratio between the volume of burned fuel and the total volume of fuel reaches a certain value and changing the ignition timing so that the motor shaft angular position coincides with a predetermined v. The ratio between the volume of fuel burned and the total fuel volume can be estimated by detecting the flame front.

According to a particular embodiment of this method, the passage of the flame front past a certain point in at least one cylinder (ie the interface between burned and unburned fuel) is detected, after which the ignition timing of the combustion is changed so that this passage coincides with the motor shaft passage past a predetermined angular position.

In general, the flame front is detected with an ionization probe which emits a characteristic signal when the motor shaft is in a defined area. This area is defined as an "angular window" and is described, for example, in the previously cited French patent 2,432,097. The detection can just as well be performed by means of a temperature probe with fast time characteristics or by means of a radiation meter.

Experience shows that the combustion conditions in the cylinders vary, the detection of the flame front by means of an ionization probe in said "angular windows" has a certain random character, either this is due to the fact that the detection is not performed during all work cycles, for example due to the absence of combustion or that this is because the detection cannot be considered representative of the cylinder's function. Under such conditions, the control of the ignition ignition timing cannot be considered satisfactory. The improved method of the invention overcomes these shortcomings.

According to an embodiment of the method according to the invention 10 15 20 25 30 35 40 453 770 applied to an engine with sqwd ün fl nhg of the combustion, the ignition time of the combustion is changed when knocks occur in at least one cylinder to make the knocks disappear in the cylinder. The ignition timing can be controlled by any method known to those skilled in the art as described in French Patent 2,337,261 or U.S. Patent 4,211,194.

The method of the present invention is described in the following with reference to the accompanying drawing. The example refers to an engine with four cylinders A, B, C and D, which is not shown.

Associated circuits have been denoted by the corresponding lowercase letters a, b, c or d.

The motor is equipped with detectors 64a to 64d which emit a signal at the occurrence of a phenomenon characteristic of the operating condition of the motor.

This signal is then processed and possibly converted in the circuits 6Sa to 65d. These circuits can also determine whether the measured value is to be accepted or rejected according to certain predetermined criteria, for example such as the signal amplitude, the signal form.

Thus, for example, if the phenomenon which characterizes the operating state of the engine is the maximum pressure, each cylinder in the engine is provided with means for detecting it. For example, but without being limited to this embodiment, the piston tops are provided with four accelerometers 64a to 64d which emit a signal corresponding to the acceleration to which the piston top is subjected in a particular cylinder. The signal from each accelerometer is transmitted to an analysis circuit 65a to 65d.

The four accelerometers 64a to 64d can be replaced by a single accelerometer, placed in a suitable place in the engine. The output signal from the accelerometer is a function of the angular position of the crankshaft and is fed to a selected analysis circuit.

Each circuit 65a to 65d emits a characteristic signal when the pressure in the associated cylinder is maximum. This characteristic signal (not shown) is converted into a suitable circuit, which, for example, emits a pulse when the pressure is maximum.

In the case where the passage of the flame front past a certain point is used as the phenomenon which characterizes the operating condition of the engine, each cylinder is provided with an ionization probe 64a, 64b, 64c and 64d. The probe emits a signal each time the flame front passes the point. The signal from each probe is an analog signal which is converted to a logic signal in an analog logic converter 6Sa, 65b, 6Sc and 65d.

The signal from each circuit 65a to 65d is sent to a circuit 66a, 66b, 66c or 66d which locates the angular position of the motor shaft for which a corresponding signal is emitted, after which the circuit 66a to 66d emits a signal corresponding to this position. Each circuit for locating the angular position 66a to 66d is synchronized by a clock 67, which is, for example, of the type described in French patent 2,404,121.

A circuit 68, connected to the clock 67, continuously determines whether the signals transmitted from each circuit 66a to 66d in the determined angular range of the motor shaft where it is expected that the respective circuit 65a to 65d emit a signal are to be approved.

The signal which arises in each locating circuit for the angular position 66a to 66d is forwarded to a processing circuit 69a to 69d.

Each processing circuit is adapted to, in the operating cycle of the corresponding cylinder, emit a reference signal after continuously having: a) established a representative statistical value from the different values for the angular position of the crankshaft during which the ionization probe has emitted a predetermined number of P signals during a number of Q duty cycles, b) assumed, if there is one, the representative statistical value for the angular position of the crankshaft which has been obtained in one of the treatment circuits associated with other cylinders, then after Q duty cycles the number of signals emitted is less than P , and c) produced a reference signal corresponding to the determined statistical value, produced in paragraph a or b, this reference signal being used to control the supply of the ignition, which is shown later.

According to another embodiment of the invention, which allows a faster setting of the ignition timing of the combustion depending on the operating condition of the engine, each treatment circuit is adapted to, during the operating cycle of the corresponding cylinder, emit a reference signal after continuously having: a) established a representative statistical value from the different values of the angular position of the crankshaft, during which the analysis circuit has emitted a predetermined number of P signals during a number less than Q, working cycles, b ) assumed, if any, the representative statistical value of the angular position of the crankshaft which has been obtained in one of the processing circuits associated with another cylinder, then after Q cycles the number of signals emitted is lower than P, and 'c) prepared a reference signal corresponding to the determined statistical value obtained in stage a or b, this reference signal being used to control the supply of ignition ngen, which will be shown later. the values P and Q are determined for each motor type, so that a satisfactory thread is achieved. They may be a function of the operating condition of the engine. For example, in a vehicle with a 78 kW engine and positive ignition, there are quite excellent results with the following values: P = 8 and Q = 16 Furthermore, during one of the experiments, a treatment circuit for a first cylinder was adapted that, when it was if necessary, assume the value obtained in the treatment circuit of the cylinder in which the ignition takes place just before the first cylinder. The value was obtained in accordance with the first paragraph a above.

The reference signal from each circuit 69a to 69d is transmitted to a circuit 70a to 70d arranged to determine a supply value, so that the analysis circuit emits its signal corresponding to a determined position of the crankshaft, and to output a main control signal which sets the ignition supply thereto. value.

This main control signal is transmitted via a selector circuit 71, the function of which will appear later, and drives a high-voltage generator 72 which feeds the spark plug over a distributor 73 when the engine has controlled ignition. In a compression-ignition engine, the control signal, possibly after a suitable conversion of the signal in a suitable device, goes to the injection nozzles and their controls.

Thus, under normal operating conditions, the ignition time is controlled by the maximum pressure in at least one of the engine cylinders, ie that for each cylinder the angular position of the engine shaft is determined in advance in which the phenomenon that characterizes the engine operating condition should occur.

Sometimes, as stated earlier, there may be conditions 10 15 20 25 30 35 40 453 770 during engine operation as no signal is given to the circuits 70 which generate the main control signal. This is especially the case when starting the engine, or when the number of signals emitted is lower than P for all the engine cylinders, or further when the detectors 64a to 64d do not emit any signal, or due to cable breakage in the lines from the detectors.

In this case, a circuit 75 has been provided which can emit a secondary control signal corresponding to a predetermined supply value. This value can be a constant or a function of at least one parameter relating to the engine's operating state, such as the engine speed measured with the detector 76, the engine's refueling, a temperature or a measurable characteristic engine pressure (detector 77), or an external parameter such as the accelerator pedal position .

The circuit 75 which provides the secondary control signal may be of known type and therefore need not be described in detail. For example, in the case of positive ignition, a circuit sold under the designation RENIX S100001-001 and used in some RENAULT cars may be used.

The secondary control signal is applied to the selector circuit 71.

Similarly, there is a safety circuit which produces a preferential control signal during certain operating conditions in the engine which are detected by a suitable sensor 78. For example, but not limited to this, the sensor 78 in a controlled ignition engine emits a signal when such phenomena occur as self-ignition or knocking in a cylinder. The circuit 74 produces a preferential control signal which changes the supply of the ignition until the knocks cease. This circuit may be any known circuit, for example that described in U.S. Patent 4,120,272.

The preference control signal is transmitted to the selector circuit 71.

The circuit 71 selects at any moment which signal of the main control signal, the secondary control signal and the preferential control signal is to control the ignition. The selected signal activates the high voltage generator which, via the distributor 73, continuously supplies the spark plugs (not shown) in the case of a motor with controlled ignition. In the case of a compression-ignition engine, the selected signal is fed to the fuel injection nozzles and to their control devices, possibly after conversion of the signal into a suitable device. The selection is performed as follows: a) if there is a preferential control signal, the selector 71 transmits the signal to the high voltage generator in a motor with controlled ignition and in a compression ignition motor to the injection nozzles, possibly via a suitable device, b) í in the absence of preferential control signal b-1) the selector circuit 71 transmits the main control signal when there is such a signal, and b-2) in the absence of such main control signal the circuit transmits the secondary control signal.

Preferably, the circuits with reference numerals 65 and 71 may consist of microprocessors pre-programmed during manufacture or also of programmable microprocessors such as INTEL 8085 with some memory such as R.0.M (Read-Only Memory), PROM (Programmable Read-Only Memory) or REPR0 .M.

(Reprogrammable Read-Only Memory).

Claims (9)

10 15 20 25 30 35 40 453 770 H Patent claim A method of automatically regulating the ignition timing of an internal combustion engine having at least one cylinder provided with means for locating the angular position of the engine shaft corresponding to the occurrence of at least one phenomenon which characterizes the operating condition of the engine as the phenomenon and / or the detection determination of a statistical value associated with this phenomenon, characterized in that for said cylinder the angular position of the motor shaft is measured at the moment when said phenomenon is detected, and after obtaining a number of P validated values during a number of cycles, which number of cycles is at most equal to a predetermined value Q, the said statistical value is formed which is to be a representative statistical angular value of the validated values, and on the basis of this statistical value a change value is formed which is allowed to influence the ignition timing control means. for combustion, in such a way that t said statistical value assumes a predetermined value V. A method according to claim 1, that the predetermined value V, the number P or the number characterized by Q can either be a fixed value or a function of a parameter relating to the operating condition of the engine such as its speed, its fuel filling, its noise, the content of pollutants in the exhaust gases, the nature of the carburettor, an engine temperature. A method according to any one of the preceding claims for an engine with several cylinders, at least one of which is equipped with means for detecting said phenomenon, characterized in that the statistical value, which depends on measures taken of said cylinder, is also used to determining the change value of the ignition time of the cylinders not equipped with such means for detecting said phenomenon. A method according to any one of the preceding claims for an engine with several cylinders, at least two of which are equipped with detection means, characterized in that the statistical value of at least one cylinder equipped with detection means is used to control the ignition timing of another cylinders not provided with such detecting means or for a cylinder in which the number of validated values is less than P 10 cycles during Q cycles. 5. A method according to any one of the preceding claims, characterized in that if, in all cylinders provided with detecting means, the number of validated measured values for said phenomenon characteristic of the engine operating condition is less than P during Q cycles, one ignition time a preselected value. 6. A method according to claim 5, characterized in that said preselected value for the ignition time of combustion is determined as a function of a value from at least one parameter affecting the operation of the engine, such as the engine speed, engine fuel, a temperature or a measurable engine. - pressure, the nature of the carburettor or an external parameter such as the accelerator pedal position. Method according to one of the preceding claims, characterized in that the phenomenon which characterizes the operating condition of the engine is the maximum pressure in the cylinders. 8. A method according to any one of claims 1-6, characterized in that the phenomenon which characterizes the operating condition of the engine is the passage of the flame front past a certain point in the combustion chamber. 9. A method according to any one of the preceding claims for an engine with controlled combustion provided with means for detecting knocks, characterized in that when knocks occur the ignition supply is changed in at least the cylinder where the knocks have been detected to cause the knocks to disappear.