METHOD FOR DETERMINING THE AIR VOLUME OF AN AIR RESERVOIR FOR AN INTERNAL COMBUSTION ENGINE OF A VEHICLE

Abstract

One aspect of the invention relates to a method 100 for determining the volume of air in an air reservoir for an internal combustion engine equipping a motor vehicle, the vehicle having an exhaust catalytic converter, when a demand for heating the exhaust catalytic converter is detected by vehicle control means, the method performed, via the control means, the steps of: Determining 101 an engine speed; Determining 102 a torque setpoint; Determining 103 an engine coolant temperature; Determining 104 a first volume of air for the air reservoir as a function of the determined engine speed, torque setpoint, and temperature; Determining 105 an atmospheric pressure; When the determined atmospheric pressure is below a threshold atmospheric pressure, determining 106 a second volume of air smaller than the first volume of air. Figure to be published with the abstract: Figure 2

Description

Title of the invention: METHOD FOR DETERMINING THE AIR VOLUME OF AN AIR RESERVOIR FOR AN INTERNAL COMBUSTION ENGINE OF A VEHICLE

[0001] The present invention relates to a method for determining the volume of air in an air reservoir for an internal combustion engine equipping a motor vehicle, said volume of air being used to increase the temperature of the vehicle's exhaust catalyst. The technical field of the invention is therefore that of controlling the air reservoir to increase the temperature of an exhaust catalyst.

[0002] An internal combustion engine comprises a selected number of cylinders, each forming a combustion chamber, suitable for allowing the combustion of a mixture of air and fuel. This combustion is supervised by a computer, also referred to as the engine control unit, configured to adjust, via actuators, various engine operating parameters influencing this combustion, for example, the regulation of the amount of air admitted into the cylinders, the mass of fuel injected, and the ignition to trigger combustion.

[0003] Exhaust gases, and more specifically pollutants such as carbon monoxide, nitrogen oxides, and unburned hydrocarbons, resulting from combustion, are usually treated by means of an exhaust catalyst. In order to effectively treat these pollutants, the catalyst temperature must be around 400°C.

[0004] When the exhaust catalyst is at ambient temperature, for example during engine start-up, in order to reach the optimal catalyst temperature of 400°C, an additional quantity of air is injected into the engine to ensure proper engine operation. This increased oxygen supply to the engine effectively contributes to raising the exhaust temperature and thus the catalyst temperature.

[0005] To achieve this operation, the opening of the intake air throttle is controlled so as to store a predetermined volume of air in an air reservoir. Then, this predetermined volume of air stored in the air reservoir is injected into the engine cylinders so as to increase the oxygen supply to the engine, and therefore the temperature of the exhaust gases.

[0006] The volume of air stored is usually determined by three parameters, namely the engine speed, the torque setpoint corresponding to the depressor of the accelerator pedal and the value of the engine coolant temperature.

[0007] Furthermore, it should be noted that the stability of an engine's operating speed is very complex to ensure and depends on many factors, including atmospheric pressure and the activation of the catalyst's heating function.

[0008] When operating at high altitude, because the air density is altered, the exhaust back pressure and the pressure losses normally present in the engine are modified and can lead to engine vibration that is perceived as unpleasant by the driver, or even to engine stalling, thus creating a safety risk. These phenomena are accentuated during the catalyst heating process.

[0009] A control strategy for regulating the oxygen supply to the catalyst when the vehicle is traveling at high altitude is also known from document CN-A-116608031. Since air density decreases with altitude, the proposed strategy involves increasing the volume of air stored in the air reservoir to ensure adequate catalyst heating. While this strategy improves catalyst heating at high altitude, it further increases the risk of engine vibration and even engine stalling.

[0010] The invention offers a solution to the problems mentioned above, by proposing a method to avoid vibratory behavior of the internal combustion engine during heating of the exhaust catalyst at high altitude.

[0011] In this context, the invention relates, in its broadest sense, to a method for determining the volume of air in an air reservoir for an internal combustion engine equipping a motor vehicle, the vehicle having an exhaust catalyst, when a demand for heating of the exhaust catalyst is detected by vehicle control means, the method performs, via the control means, the steps of: • Determine an engine speed; • Determine a torque setting; • Determine the engine coolant temperature; • Determine an initial volume of air for the air reserve based on the engine speed, torque setpoint and temperature determined.

[0012] The method according to this aspect of the invention is remarkable in that it also performs, via the control means, the steps of: • Determine atmospheric pressure; • When the determined atmospheric pressure is less than an atmospheric pressure threshold, determine a second volume of air less than the first volume of air.

[0013] Thanks to the process according to the invention, atmospheric pressure is taken into account to regulate the volume of air for catalytic heating. More particularly, The air volume is reduced when atmospheric pressure decreases, in other words, when the vehicle is at high altitude. More specifically, the second air volume being smaller than the first air volume helps prevent vibrations in the internal combustion engine that would otherwise be caused by changes resulting from decreased atmospheric pressure, exhaust back pressure, and pressure losses.

[0014] In addition to the characteristics just mentioned in the preceding paragraph, the process according to this aspect of the invention may have one or more complementary characteristics from among the following, considered individually or according to all technically possible combinations.

[0015] According to a non-limiting aspect of the invention, the atmospheric pressure threshold is between 701.37 hPa and 780 hPa

[0016] According to a non-limiting aspect of the invention, the first volume of air is determined by the product of an initial volume of air and a coefficient; • The initial air volume is determined by means of an initial mapping providing initial air volume values ​​as a function of engine speed values ​​and torque setpoint values; • The coefficient is determined by means of a second map providing coefficient values ​​as a function of coolant temperature values.

[0017] According to a non-limiting aspect of the invention, the second volume of air is determined by applying a percentage reduction to the first volume of air.

[0018] According to a non-limiting aspect of the invention, the percentage decrease is determined by means of a third map providing percentage decrease values ​​as a function of atmospheric pressure values.

[0019] According to a non-limiting aspect of the invention, it includes a step of injecting the second volume of air into the air reservoir.

[0020] According to a non-limiting aspect of the invention, the second volume of air is injected into the air reserve by controlling, via the control means, an air intake butterfly valve that comprises the internal combustion engine.

[0021] Another aspect of the invention relates to a motor vehicle comprising an internal combustion engine, an exhaust catalyst, an air reservoir and control means configured to carry out the steps of the process according to any one of the aforementioned aspects of the invention.

[0022] Another aspect of the invention relates to a computer program product downloadable from a communication network and / or stored on a computer-readable medium and / or executable by a processor. The computer program product includes program code instructions for implementation of the process according to any of the aforementioned aspects of the invention, when the program is executed on a computer.

[0023] The invention and its various applications will be better understood by reading the following description and examining the accompanying figures.

[0024] [Fig-1] illustrates, schematically, a vehicle according to a non- limiting of the invention.

[0025] [Fig.2] illustrates a step diagram of a process for determining a volume air from an air reservoir for an internal combustion engine equipping a vehicle such as the one shown in [Fig.1].

[0026] The figures are presented for illustrative purposes only and are in no way limiting of the invention.

[0027] Unless otherwise specified, the same element appearing on different figures has a unique reference.

[0028] Figure 1 illustrates a motor vehicle. Vehicle 1 includes, in particular, from upstream to downstream of the airflow, • a throttle body 2; • an air reserve 3, also called a plenum; • an internal combustion engine 4; and • an exhaust catalyst 5.

[0029] The vehicle 1 further comprises control means 6. These control means 6 are configured to perform the steps of a method 100 for determining an air volume of the air reserve 3 of the internal combustion engine 4 equipping the motor vehicle 1 such as that illustrated in [Fig.2].

[0030] The method 100 includes a step of determining 101 an engine speed, for example in revolutions per minute.

[0031] The method 100 also includes a step of determining 102 a torque setpoint, for example in newton meters. This torque setpoint corresponds, for example, to the travel of the accelerator pedal of the vehicle 1. This torque setpoint reflects the user's desired acceleration of the vehicle.

[0032] The process 100 also includes a step of determining 103 a coolant temperature of the internal combustion engine 4. According to a non-limiting embodiment, this coolant temperature can be measured by a temperature sensor.

[0033] The process 100 then includes a step of determining 104 a first volume of air from the air reserve 3. This first volume of air is determined as a function of the engine speed previously determined in step 101, the torque setpoint previously determined in step 102 and the temperature of the coolant previously determined in step 103.

[0034] According to a non-limiting embodiment, the first volume of air is determined by the product of an initial volume of air and a coefficient.

[0035] According to a non-limiting embodiment, the initial air volume is determined by means of a first map Cl. This first map Cl provides initial air volume values ​​as a function of engine speed values ​​and torque setpoint values. Thus, from a given engine speed and torque setpoint, it is possible to select the initial air volume of the product.

[0036] According to a non-limiting embodiment, the product coefficient is determined by means of a second map C2. This second map C2 provides coefficient values ​​as a function of coolant temperature values. Thus, from a determined internal combustion engine coolant temperature 4, it is possible to select the product coefficient.

[0037] The method 100 further includes a step of determining 105 an atmospheric pressure. This atmospheric pressure can be measured by means of a pressure sensor (not shown) included in the vehicle 1, and then transmitted to the control means 6.

[0038] When the determined atmospheric pressure is below a threshold atmospheric pressure, the method 100 includes a step of determining 106 a second volume of air smaller than the first volume of air. According to a non-limiting embodiment, this threshold atmospheric pressure can be between 701.37 hPa and 780 hPa, which corresponds to an altitude of 3000 m and 2000 m respectively.

[0039] According to a non-limiting embodiment, the second air volume is determined by applying a percentage reduction to the first air volume. For example, the percentage reduction is determined by means of a third C3 map providing percentage reduction values ​​as a function of atmospheric pressure values. Thus, based on the atmospheric pressure determined in step 105, it is possible to select the percentage reduction.

[0040] In order to avoid malfunction of the internal combustion engine 4 at high altitude, the second volume of air determined by the method 100 according to the invention is less than the first volume of air initially provided by the prior art methods to increase the temperature of the exhaust catalyst 5.

[0041] Once the second volume of air is determined, the process 100 includes a step of injecting 107 the second volume of air into the air reserve 3 by controlling, via the control means 6, the air intake throttle body 2.

[0042] Then, this second predetermined volume of air stored in the air reservoir 3 is injected into the cylinders of the internal combustion engine 4 so as to increase the oxygen supply in the internal combustion engine 4, and therefore consequently the temperature of the exhaust catalyst 5.

Claims

1.

2.

3. Demands Method (100) for determining the volume of air in an air reservoir (3) for an internal combustion engine (4) equipping a motor vehicle (1), said vehicle (1) having an exhaust catalyst (5), when a demand for heating of the exhaust catalyst (5) is detected by control means (6) of said vehicle (1), said method (100) performs, via said control means (6), the steps of: - Determine (101) an engine speed; - Determine (102) a torque setpoint; - Determine (103) a liquid temperature of cooling of said engine (4); - Determine (104) a first volume of air for said air reserve (3) as a function of said engine speed, said torque setpoint and said temperature determined; - said process (100) being characterized in that it further performs, via said control means (6), the steps of: - Determine (105) an atmospheric pressure; - When said determined atmospheric pressure is less than an atmospheric pressure threshold, determine (106) a second volume of air less than said first volume of air. Method (100) according to the preceding claim, characterized in that the atmospheric pressure threshold is between 701.37 hPa and 780 hPa. Method (100) according to any one of the preceding claims, characterized in that the first volume of air is determined by the product of an initial volume of air and a coefficient; - said initial air volume being determined by means of a first map (Cl) providing initial air volume values ​​as a function of engine speed values ​​and torque setpoint values; - said coefficient being determined by means of a second map (C2) providing coefficient values ​​as a function of coolant temperature values.

4. Method (100) according to any one of the preceding claims, characterized in that the second volume of air is determined by applying a percentage reduction to the first volume of air.

5. Method (100) according to the preceding claim, characterized in that the percentage decrease is determined by means of a third map (C3) providing percentage decrease values ​​as a function of atmospheric pressure values.

6. A method (100) according to any one of the preceding claims, characterized in that it comprises a step of injecting (107) the second volume of air into the air reservoir (3).

7. Method (100) according to the preceding claim, characterized in that the second volume of air is injected into the air reserve (3) by controlling, via the control means (6), an air intake butterfly valve (2) which comprises the internal combustion engine (4).

8. Motor vehicle (1) comprising an internal combustion engine (4), an exhaust catalyst (5) and an air reservoir (3), said vehicle (1) being characterized in that it comprises control means (6) configured to carry out the steps of the process (100) according to any one of the preceding claims.

9. Product computer program downloadable from a communication network and / or recorded on a computer-readable medium and / or executable by a processor, characterized in that it includes program code instructions for implementing the method (100) according to any one of claims 1 to 7, when the program is executed on a computer.

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