Method for balancing an air-fuel mixture from each cylinder of an internal combustion engine

Abstract

The invention relates to a method (100) for balancing an air-fuel mixture from a pair of cylinders associated with a binary probe, comprising the steps of: - determining (101), during an engine cycle, four voltage values corresponding to four angular positions spaced apart from one another by 180° from a crankshaft; - determining (102) a first difference between two voltage values and a second difference between two different voltage values, - determining (104), for a determined engine speed and a determined engine load, a first and a second factor in mapping, - selecting (105) a maximum value between the absolute value of the first and second factors; - determining (106) a balancing direction of the first cylinder on the basis of the maximum absolute value; - balancing (107) the air-fuel mixture of the first cylinder and / or second cylinder(s) on the basis of the determined balancing direction.

Description

DESCRIPTION METHOD FOR BALANCING AN AIR-FUEL MIXTURE FROM EACH CYLINDER OF AN INTERNAL COMBUSTION ENGINE TECHNICAL FIELD OF THE INVENTION

[0001] The field of the invention is that of balancing the air-fuel mixture from the cylinders of an internal combustion engine. The invention applies more particularly to internal combustion engines having at least two cylinders. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0002] It is well known that, in order to reduce harmful substances emitted by internal combustion engines, these engines are equipped with at least one exhaust gas catalyst. The efficiency of this catalyst depends heavily on the air-fuel mixture produced by the internal combustion engine's cylinders.

[0003] To facilitate the treatment of these exhaust gases by the catalytic converter, it is known to measure the oxygen concentration in the exhaust gases from the internal combustion engine cylinders using a binary probe. The binary information provided by this probe indicates either a lean fuel mixture (voltage close to 0 V) ​​or a rich fuel mixture (voltage close to 1 V). The approximately stoichiometric air-fuel mixture, necessary for efficient conversion in the catalytic converter, is then obtained by alternating slightly rich and slightly lean fuel injection based on the binary probe readings. This strategy ensures a correct average mixture of the exhaust gases from all the cylinders of the internal combustion engine.

[0004] However, in the same internal combustion engine, the air-fuel mixture from each cylinder can differ. These differences can be due to variations in the manufacturing dimensions of each cylinder. To more effectively regulate the air-fuel mixture and aid catalytic conversion, it is known to place a sensor at the outlet of each cylinder and to regulate the fuel injection control for each cylinder independently. Such an implementation However, it requires a large number of binary probes and extensive wiring, increasing the cost of the vehicle carrying these probes. SUMMARY OF THE INVENTION

[0005] One objective of the invention is to provide a low-cost solution for balancing an air-fuel mixture from each cylinder of an internal combustion engine.

[0006] To this end, the invention relates, in its broadest sense, to a method for balancing an air-fuel mixture from each cylinder of an internal combustion engine, the internal combustion engine comprising at least one pair of cylinders, each associated with a binary probe, the pair of cylinders comprising a first cylinder and a second cylinder, each comprising a piston mechanically connected to a crankshaft, the method being remarkable in that it comprises the steps of, for each pair of cylinders: To determine, during a motor cycle, via a binary probe, A first tension value when the crankshaft is positioned at a first angular position; A second tension value when the crankshaft is positioned at a second angular position of +180° relative to said first angular position; A third tension value when the crankshaft is positioned at a third angular position of + 360° relative to said first angular position; A fourth tension value when the crankshaft is positioned at a fourth angular position of +540° relative to said first angular position; Determine, via control means, a first difference between the first and third voltage values ​​and a second difference between the second and fourth voltage values; Filter, via the control means, the said first and second differences; To determine, via the control means, for a given engine speed and engine load, In a first mapping, a first factor, said first factor being representative of an imbalance between the first cylinder and the second cylinder when an absolute value of said first factor is close to 1; In a second mapping, a second factor, said second factor being representative of an imbalance between the first cylinder and the second cylinder when an absolute value of said second factor is close to 1; If at least one absolute value of said first determined factor or of said second determined factor is greater than a first threshold, select, via the control means, a maximum value between the absolute value of the first factor and the absolute value of the second factor; Determine, using control methods, a direction of balance as follows: If the maximum value is the absolute value of the first factor, multiply the sign of the first filtered difference by the sign of the first factor, the sign resulting from the multiplication giving the direction of balancing of the first cylinder; If the maximum value is the absolute value of the second factor, multiply the sign of the second filtered difference by the sign of the second factor, the sign resulting from the multiplication giving the direction of balancing of the first cylinder; when the maximum value is the absolute value of the first factor and the absolute value of the first filtered difference is greater than a second threshold or when the maximum value is the absolute value of the second factor and the absolute value of the second filtered difference is greater than said second threshold, balance, via the control means, the air-fuel mixture from at least one of the first and second cylinders according to the direction of balancing of the first cylinder determined.

[0007] Thanks to the method according to the invention, a single binary sensor, also referred to as a lambda sensor, is used to determine the air-fuel mixture from the first cylinder and the air-fuel mixture from the second cylinder of a pair of cylinders. Thus, it is possible to balance the air-fuel mixture from the cylinders of an internal combustion engine. Compared to the prior art, a single sensor is used for two cylinders, consequently significantly reducing the cost of the vehicle equipped with these binary sensors.

[0008] In addition to the characteristics mentioned in the preceding paragraph, the process according to the invention may have one or more additional characteristics from among the following, considered individually or according to all technically possible combinations.

[0009] According to a non-limiting implementation of the invention, the absolute value of the first factor is close to 1 when it is greater than or equal to 0.8; the absolute value of the second factor is close to 1 when it is greater than or equal to 0.8.

[0010] According to a non-limiting implementation of the invention, the first threshold is greater than or equal to 0.8.

[0011] According to a non-limiting implementation of the invention, during the balancing step: when the sign resulting from the multiplication giving the direction of balancing of the first cylinder is negative, the quantity of fuel injected into the first cylinder is increased and the quantity of fuel injected into the second cylinder is decreased; when the sign resulting from the multiplication giving the direction of balancing of the first cylinder is positive, the quantity of fuel injected into the first cylinder is decreased and the quantity of fuel injected into the second cylinder is increased.

[0012] According to a non-limiting implementation of the invention, the step of filtering the first and second differences is performed using a first-order filter.

[0013] The invention also relates to a computer program product comprising instructions which, when the program is executed by a computer, cause the computer to carry out the steps of the process according to any one of the preceding implementations.

[0014] The invention further relates to a motor vehicle equipped with an internal combustion engine comprising at least one pair of cylinders, the vehicle being notable in that it includes control means configured to perform the steps of the process according to any one of the aforementioned implementations, and in that it includes a different binary probe for each pair of cylinders.

[0015] According to a non-limiting implementation of the invention, the vehicle comprises a single pair of cylinders and a single binary probe.

[0016] According to a non-limiting implementation of the invention, the vehicle comprises a first pair of cylinders, a second pair of cylinders, a first binary probe associated with said first pair of cylinders and a second binary probe associated with said second pair of cylinders.

[0017] According to a non-limiting implementation of the invention, the vehicle is of the two-wheeled type.

[0018] The invention and its various applications will be better understood by reading the following description and examining the accompanying figures. BRIEF DESCRIPTION OF THE FIGURES

[0019] The figures are presented for illustrative purposes only and are in no way limiting to the invention.

[0020] [Fig. 1] illustrates, schematically, a vehicle according to a non-limiting aspect of the invention.

[0021] [Fig. 2] shows, schematically, the steps of a process according to a non-limiting aspect of the invention.

[0022] [Fig. 3a], [Fig. 3b] show, schematically, two maps used during the execution of the process according to a non-limiting aspect of the invention. DETAILED DESCRIPTION

[0023] Unless otherwise specified, the same element appearing on different figures has a unique reference.

[0024] Figure 1 schematically illustrates a motor vehicle conforming to a non-limiting implementation of the invention.

[0025] In this non-limiting example, vehicle 1 is a two-wheeled motor vehicle equipped with an internal combustion engine 2 comprising a single pair of cylinders 3.

[0026] The pair of cylinders 3 comprises a first cylinder 3a and a second cylinder 3b. Each of the first cylinder 3a and second cylinder 3b comprises a piston 4 mechanically connected to a crankshaft 5.

[0027] The pair of cylinders 3 is further associated with a single binary probe 6. In order to carry out measurements of the air-fuel mixture of the exhaust gases from the first and second cylinders 3a, 3b, this binary probe 6 is arranged at the outlet of the first and second cylinders 3a, 3b.

[0028] Vehicle 1 also includes control means 7, for example consisting of an engine control unit.

[0029] These control means 7 are configured to perform the steps of process 100 to balance an air-fuel mixture from each of the first and second cylinders 3a, 3b of the internal combustion engine 2.

[0030] The process 100 includes a step of determining 101, during a motor cycle, via the binary probe 6, A first tension value when the crankshaft 5 is positioned at a first angular position, for example of 180°; A second tension value when the crankshaft 5 is positioned at a second angular position of + 180° relative to the first angular position, i.e. 360° in the example; A third tension value when the crankshaft 5 is positioned at a third angular position of +360° relative to the first angular position, i.e., 540° in the example; and A fourth tension value when the crankshaft 5 is positioned at a fourth angular position of + 540° relative to the first angular position, i.e. 720° in the example.

[0031] According to a non-limiting embodiment not shown, a target position sensor can be used to measure the angular position of the crankshaft 5. The target can be rotationally fixed to the crankshaft 5 and have teeth. Thus, by counting the teeth passing in front of it, the sensor is able to determine the angular position of the crankshaft 5.

[0032] The binary sensor 6 provides, at each of the aforementioned angular positions, an analog voltage reading, typically between 0V and 1V. The information provided by this binary sensor 6 indicates either a lean fuel mixture from cylinder pair 3 or a rich fuel mixture from cylinder pair 3. When the mixture is lean, a voltage close to 0V is measured by the binary sensor 6. Conversely, when the mixture is rich, a voltage close to 1V is measured by the binary sensor 6.

[0033] For example, as illustrated by the first and second maps C1 and C2 in Figures 3a and 3b, at each engine operating point defined by an engine speed and an air flow rate, a coefficient ranging from -1 to 1 is entered. The value of this coefficient represents, for the first map C1 and the second map C2, an imbalance between the first cylinder 3a and the second cylinder 3b. The sign of the coefficient also indicates the direction of the imbalance between the first cylinder 3a and the second cylinder 3b.

[0034] In order to define the first C1 and the second C2 map, a reference engine (in other words, a nominal engine) is considered, and an enrichment imbalance is forced between 1 er cylinder 3a and the second cylinder 3b. For example, the enrichment difference is defined between 5 and 10%.

[0035] Following the generation of this enrichment difference, the lambda probe voltage is measured for each operating point of the map to be defined, in the manner described previously, more precisely, the values ​​are measured every 180 degrees as explained in paragraph 30.

[0036] Thus, after measuring the first, second, third, and fourth voltage values, the following differences are determined:

[0037] -a first difference Vdifl between the first voltage value and the third voltage value,

[0038] -and a second difference Vdif2 between the second voltage value and the fourth voltage value.

[0039] To define the first and second maps C1, C2, for each operating point of the map, the following comparisons allow us to define the value of the first and second maps C1, C2 ::

[0040] - if Vdifl > Vdif2 > 0 then: the value of the first map C1 is close to 1, the value of the second map C2 is close to 0,

[0041] - if Vdifl < Vdif2 < 0 then: the value of the first map C1 is close to -1, the value of the second map C2 is close to 0,

[0042] - if Vdif2 > Vdifl > 0 then: the value of the second map C2 is close to 1, the value of the first map C1 is close to 0,

[0043] - if Vdif2 < Vdifl < 0 then: the value of the second map C2 is close to -1, the value of the first map C1 is close to 0,

[0044] - if Vdif 1 and Vdif2 are close to 0 then the values ​​of the first and second maps C2 and C1 are close to 0.

[0045] Example :

[0046] Regarding voltage values: By "close to 0", we mean "below 10 mV".

[0047] For the maps: "Close to 0" means "below the threshold of 0.2". "Close to 1" means between 0.8 and 1, "Close to -1" means between -1 and -0.8.

[0048] Vdif1 and Vdif2 are referred to in the patent as the 'first and second differences'.

[0049] The process 100 then includes a step, executed by the control means 7, of determining 102 a first difference between the first voltage value and the third voltage value and a second difference between the second voltage value and the fourth voltage value.

[0050] The process 100 then includes a filtering step 103, via the control means 7, for the first difference and the second difference. According to a non-limiting implementation, the filtering step 103 is performed using a first-order filter.

[0051] The process 100 also includes a step, executed by the control means 7, of determining 104, for a given engine speed and engine load, In the first mapping C1, a first factor, said first factor being representative of an imbalance of the first cylinder 3a and the second cylinder 3b between them when an absolute value of said first factor is close to 1; In the second mapping C2, a second factor, said second factor also being representative of an imbalance of the first cylinder 3a and the second cylinder 3b between them when an absolute value of said second factor is close to 1.

[0052] According to a non-limiting example of an implementation, the absolute value of the first factor is close to 1 when it is greater than or equal to 0.8; the absolute value of the second factor is close to 1 when it is greater than or equal to 0.8.

[0053] If the absolute value of the first filtered difference and the absolute value of the second filtered difference are less than a first threshold, the first and second cylinders 3a and 3b are considered to be balanced so that step 104 and the following ones are not executed.

[0054] For example, for an engine speed of 3000 rpm and an air flow of 120 mg / tdc, the first factor is 0.6. Since the first factor is 0.6, the absolute value is 0.6. Since the absolute value of 0.6 is less than 0.8, we deduce that, for an engine speed of 3000 rpm and an air flow of 120 mg / tdc, the first voltage difference is not representative of an imbalance between the first and second cylinders 3a, 3b.

[0055] Conversely, for an engine speed of 3000 rpm and an air flow of 120 mg / tdc, the second factor is -1. Since the second factor is -1, the absolute value is 1. Since the absolute value of 1 is greater than 0.8, we deduce that, for an engine speed of 3000 rpm and an air flow of 120 mg / tdc, the second voltage difference is representative of an imbalance between the first and second cylinders 3a, 3b.

[0056] If at least one absolute value of the first determined factor or of the second determined factor is greater than the first threshold, the process 100 includes a step of selecting 105 a maximum value between the absolute value of the first factor and the absolute value of the second factor, in this case 1 in the example described.

[0057] For example, the first threshold is greater than or equal to 0.8. Indeed, since the absolute value of the first factor is less than 0.8, this means it may be noisy and therefore unusable. On the other hand, since the absolute value of the second factor is greater than 0.8, this maximum absolute value represents an imbalance between the first and second cylinders 3a and 3b and is considered unaffected.

[0058] Next, process 100 includes a step of determining 106 a direction of balancing as follows: If the maximum value is the absolute value of the first factor, multiply the sign of the first filtered difference by the sign of the first factor, the sign resulting from the multiplication giving the direction of balancing of the first cylinder 3a; If the maximum value is the absolute value of the second factor, multiply the sign of the second filtered difference by the sign of the second factor, the sign resulting from the multiplication giving the direction of balancing of the first cylinder 3a.

[0059] In the example described, since the maximum value is the absolute value of the second factor, we multiply the sign of the second filtered difference, for example negative, by the sign of the second factor of -1, and we obtain a positive balancing direction. This therefore leads, for example, to enriching the first cylinder 3a and leaning out the second cylinder 3b.

[0060] When the maximum value is the absolute value of the first factor and the absolute value of the first filtered difference is greater than a second threshold or when the maximum value is the absolute value of the second factor and the absolute value of the second filtered difference is greater than the second threshold, the process 100 then includes a step of balancing 107, via the control means 7, the air-fuel mixture from at least one of the first cylinder 3a and second cylinder 3b.

[0061] Since the sign resulting from the multiplication giving the direction of balancing of the second cylinder 3b is positive, the quantity of fuel injected into the first cylinder 3a is increased and the quantity of fuel injected into the second cylinder 3b is gradually decreased until a second difference equal to zero is reached.

[0062] Thus, with a single binary probe 6, the method 100 according to the invention is able to determine an imbalance between two cylinders of the same engine, and act on the fuel injection at the level of each of the cylinders taken individually.

[0063] Furthermore, the method described above (method 100) is performed on a two-wheeled vehicle with only one pair of cylinders. It is understood that this method applies to any type of vehicle, whether two-wheeled, four-wheeled, or more. In addition, and without limitation, the number of cylinder pairs can be two, three, or four. In this case, the vehicle has two, three, or four binary probes, respectively.

Claims

DEMANDS

1. A method (100) for balancing an air-fuel mixture from each cylinder of an internal combustion engine (2), said internal combustion engine (2) comprising at least one pair of cylinders (3), each associated with a binary probe (6), said pair of cylinders (3) comprising a first cylinder (3a) and a second cylinder (3b), each comprising a piston (4) mechanically connected to a crankshaft (5), said method (100) being characterized in that it comprises the steps of, for each pair of cylinders (3): - Determine (101), during an engine cycle, via a binary probe (6), o A first voltage value when said crankshaft (5) is positioned at a first angular position; o A second voltage value when said crankshaft (5) is positioned at a second angular position of + 180° relative to said first angular position; o A third voltage value when the crankshaft (5) is positioned at a third angular position of + 360° relative to said first angular position; o A fourth voltage value when the crankshaft (5) is positioned at a fourth angular position of + 540° relative to said first angular position; - Determine (102), via control means (7), a first difference between said first and third voltage values ​​and a second difference between said second and fourth voltage values; - Filter (103), via the said control means (7), the said first and second differences; - Determine (104), via said control means (7), for a given engine speed and engine load, o In a first map (C1), a first factor, said first factor being representative of an imbalance of the first cylinder (3a) and the second cylinder (3b) with respect to each other when an absolute value of said first factor is close to 1; o In a second mapping (C2), a second factor, said second factor being representative of an imbalance of the first cylinder (3a) and the second cylinder (3b) with respect to each other when an absolute value of said second factor is close to 1; - If at least one absolute value of said first determined factor or of said second determined factor is greater than a first threshold, select (105), via said control means (7), a maximum value between said absolute value of the first factor and said absolute value of the second factor; - Determine (106), via the said control means (7), a balancing direction as follows, o If the maximum value is the absolute value of the first factor, multiply the sign of the first filtered difference by the sign of the first factor, the sign resulting from the multiplication giving the balancing direction of the first cylinder (3a); o If the maximum value is the absolute value of the second factor, multiply the sign of the second filtered difference by the sign of the second factor, the sign resulting from the multiplication giving the balancing direction of the first cylinder (3a); - When the maximum value is the absolute value of the first factor and the absolute value of the first filtered difference is greater than a second threshold or when the maximum value is the absolute value of the second factor and the absolute value of the second filtered difference is greater than said second threshold, balance (107), via said control means (7), the air-fuel mixture from at least one of said first cylinder (3a) and second cylinder (3b) according to the balancing direction of the first cylinder determined.

2. A method (100) according to the preceding claim, characterized in that: the absolute value of the first factor is close to 1 when it is greater than or equal to 0.8; the absolute value of the second factor is close to 1 when it is greater than or equal to 0.

8.

3. A method according to any one of the preceding claims, characterized in that the first threshold is greater than or equal to 0.

8.

4. A method (100) according to any one of the preceding claims, characterized in that during the balancing step (107): - when the sign resulting from the multiplication giving the direction of balancing of the first cylinder (3a) is negative, the quantity of fuel injected into the first cylinder (3a) is increased and the quantity of fuel injected into the second cylinder (3b) is decreased; - when the sign resulting from the multiplication giving the direction of balancing of the first cylinder (3a) is positive, the quantity of fuel injected into the first cylinder (3a) is decreased and the quantity of fuel injected into the second cylinder (3b) is increased. [Claims] A method (100) according to any one of the preceding claims, characterized in that the step of filtering (103) said first and second differences is carried out by means of a first-order filter.

6. Product computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the steps of the process (100) according to any one of the preceding claims.

7. Motor vehicle (1) equipped with an internal combustion engine (2) comprising at least one pair of cylinders (3), said vehicle (1) being characterized in that it comprises control means (7) configured to carry out the steps of the process (100) according to any one of claims 1 to 5, and in that it comprises a different binary probe (6) for each pair of cylinders (3).

8. Vehicle (1) according to the preceding claim, characterized in that it comprises a single pair of cylinders (3) and a single binary probe (6).

9. A vehicle (1) according to claim 7, characterized in that it comprises a first pair of cylinders (3), a second pair of cylinders, a first binary probe (6) associated with said first pair of cylinders (3), and a second binary probe associated with said second pair of cylinders.

10. A vehicle (1) according to any one of claims 7 to 9, characterized in that it is of the two-wheeled type.

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