STRATEGY FOR COORDINATING THE AIR LOAD REGULATION OF A TURBOCHARGED GASOLINE INTERNAL COMBUSTION ENGINE

Abstract

Method for coordinating the load regulation of a turbocharged gasoline engine, variable between atmospheric (ATZ) throttle control zones, and supercharged (SAZ) turbocharger control zones, via a mixed transition zone defined around a natural boost pressure by first bias widths defining first upper (PZTS) and lower (PZTI) transition zones, where the mixed transition zone is widened by second bias widths defining second upper (DZTS) and lower (DZTI) transition zones, an algorithm is used regulating the load by the turbocharger alone or the throttle alone according to the differences between the boost pressure setpoint and the natural boost pressure, corrected by the first and second turbocharger and throttle bias values, compared to thresholds corresponding to the open saturated throttle or turbocharger;motor vehicle with computer using this method. Figure 5;

Description

Title of the invention: STRATEGY FOR COORDINATING THE AIR LOAD REGULATION OF A TURBOCHARGED GASOLINE INTERNAL COMBUSTION ENGINE

[0001] The invention relates to a method for coordinating the regulation of the air load of a gasoline internal combustion engine, turbocharged by the action of a turbine driven by the gas flow in an exhaust line and which turbine drives a turbocharger supplied with air by an air intake circuit and supplying a supercharging air circuit, directly or through an air cooler, to a motorized throttle delivering the air to an air distributor circuit directly supplying said engine, according to which the engine load is regulated, which is variable between the lowest load level in an atmospheric zone corresponding to the turbocharger fully open and where the throttle is regulated, and the highest load level in a supercharged zone corresponding to the throttle fully open and where the turbocharger is regulated, passing through an intermediate load level in a mixed transition zone,where the throttle and / or turbocharger can be regulated, where the pressure is variable around a natural boost pressure, a first throttle bias value in a first upper transition zone of the mixed transition zone to the supercharged zone, and a first turbocharger bias value in a first lower transition zone of the mixed transition zone to the atmospheric zone.

[0002] The invention relates to the field of controlling supercharged thermal engines of the gasoline type.

[0003] The regulation of the air charge of an internal combustion engine equipped with a fixed geometry turbocharger (TGF) is carried out via the throttle body in an atmospheric zone ZAT, and via the turbocharger in a supercharged zone ZSA. These two zones are defined by the concept of natural supercharging (pressure which prevails in the intake manifold when the turbine and throttle actuators are in the fully open position).

[0004] In the air supply system of the heat engine, the intake pressure is the pressure present in the air intake distributor which allows the fresh air necessary for combustion to enter the engine cylinders. The intake pressure therefore directly determines the air load of the engine for a given speed and a given timing setting. Thus, in order to obtain an intake pressure required to meet a torque request made by the driver of the vehicle, the timing setting is adapted to the engine speed. current and the throttle and turbocharger actuators are controlled by air charge regulation strategies which are based on an estimation of the natural boost pressure of the thermal engine.

[0005] The natural boost pressure PSN is the pressure present in the engine's air intake distributor when the air supply system operates in acoustic agreement, in a resonance regime, with the throttle valve fully open and the turbocharger not activated. This resonance regime makes it possible to benefit from natural supercharging which increases the air filling of the engine cylinders, with an intake pressure which is then higher than atmospheric pressure. The natural boost pressure PSN therefore represents the maximum performance that the thermal engine can achieve in terms of air charge, and therefore engine torque, in atmospheric operation, for a given engine speed and timing.

[0006] The natural boost pressure PSN is used in particular for estimating the air filling of the cylinders of the thermal engine, as well as for controlling the throttle valve and the turbocharger.

[0007] The natural boost pressure makes it possible to define the atmospheric zone ZAT in which the air charge is controlled via the throttle, and the supercharged zone ZSA in which the air charge is controlled via the turbocharger.

[0008] Knowledge of the natural boost pressure is necessary to coordinate and manage the operation of the throttle valve and turbocharger actuators. When the torque request made by the driver requires an intake pressure in the air distributor lower than the natural boost pressure, the air charge is controlled using the throttle valve alone and the engine then operates in its atmospheric zone ZAT, like a naturally aspirated engine. When the torque request requires an intake pressure higher than the natural boost pressure, the turbocharger is activated and the engine then operates in its supercharged zone ZSA. The more accurate the estimation of the natural boost pressure PSN, the better the control of the air charge around the transition zone TAS.An accurate estimation of the natural boost pressure is therefore important for optimal control of a supercharged thermal engine.

[0009] Thus, according to the prior art, the load regulation by the turbocharger is activated if the supercharging setpoint is higher than the natural supercharging pressure PSN. On the other hand, the load regulation by the throttle is activated if the pressure in the intake manifold is lower than the natural supercharging pressure PSN.

[0010] For new engines equipped with variable geometry turbochargers (TGV), this natural boost pressure PSN is higher and depends not only on external conditions (ambient pressure and temperature) but also on the conditions at the turbine terminals (mainly temperature). These new dependencies make the estimation of the boost pressure not very robust and biased, thus impacting the coordination of the load regulation. Indeed, in many cases, the two actuators can be fully open at the same time, without any power to regulate the load, consequently generating a load regulation error or even the reporting of faults leading to a power limitation.

[0011] The correct estimation of the natural boost pressure is therefore important for controlling the engine and its supercharging. It facilitates calibration tests and the determination of engine control parameters.

[0012] The objective of the present invention is to overcome these drawbacks by proposing a robustification of the coordination strategy of the air charge regulation actuators. It consists of taking into account the saturation of the actuators in the coordination of the air charge regulation in the zone where the estimation of the natural boost pressure is biased or not very robust.

[0013] To achieve this objective, the invention proposes to improve the method according to the prior art described in the introduction, to avoid simultaneous regulation by the butterfly valve and the turbocharger, and is characterized in that two other transition zones are created in the mixed transition zone, a second upper transition zone between the first upper transition zone of the mixed transition zone and the supercharged zone, and a second lower transition zone between the first lower transition zone of the mixed transition zone and the atmospheric zone, and where the pressure is variable around a natural supercharging pressure, a second butterfly bias value towards the second supercharged zone, and a second turbocharger bias value towards the first atmospheric zone,and where the turbocharger load regulation is activated if the boost pressure setpoint is not higher than the natural boost pressure minus the first turbocharger bias value and if the boost pressure setpoint is higher than the natural boost pressure minus the second turbocharger bias value and the throttle position is higher than a throttle threshold corresponding to the open saturated throttle, while the throttle load regulation is activated if the distributor pressure measurement is not lower than the natural boost pressure plus the first throttle bias value and if the distributor pressure measurement is lower than the natural boost pressure minus the second throttle bias value and the turbocharger position is in-, lower than a turbocharger threshold corresponding to the open saturated turbocharger.

[0014] Thanks to the invention, it is prevented that the two turbocharger and butterfly actuators can be saturated at the same time.

[0015] Advantageously, the first throttle bias value and the first turbocharger bias value are minimized by simulation.

[0016] This reduces the width of the mixed transition zone, because the risk of simultaneous saturation of the actuators is removed.

[0017] Advantageously, the first throttle bias value and the first turbocharger bias value are chosen to be lower than throttle bias and turbocharger bias values ​​in a simulation where the mixed transition zone is limited to the first upper transition zone and the first lower transition zone, without a second upper transition zone or a second lower transition zone.

[0018] Thus, the width of the mixed transition zone is reduced compared to the prior art, because the risk of simultaneous saturation of the actuators is removed.

[0019] Advantageously, the second throttle bias value and the second turbocharger bias value are minimized by simulation.

[0020] This reduces the width of the mixed transition zone.

[0021] More particularly, the first throttle bias value is chosen to be equal to the first turbocharger bias value.

[0022] Thus the calculations are simplified by reducing the number of parameters.

[0023] More particularly, the second throttle bias value is chosen to be equal to the second turbocharger bias value.

[0024] Thus the calculations are simplified by reducing the number of parameters.

[0025] More particularly, a hysteresis is introduced on the position of the actuators in order to eliminate or minimize possible noises which could disturb the coordination strategy.

[0026] This makes the simulation and regulation calculations more reliable.

[0027] The invention also relates to a motor vehicle control computer comprising a memory storing program instructions for implementing the method and for controlling the motorized throttle and the turbocharger.

[0028] Thus, the optimization of the regulation can be carried out anywhere.

[0029] The invention also relates to a motor vehicle comprising a gasoline internal combustion engine turbocharged by the action of a turbine driven by a gas flow in an exhaust line and which turbine drives a turbocharger supplied with air by an air intake circuit and supplying a supercharging air circuit, directly or through an air cooler, to a motorized butterfly delivering the air to an air distributor circuit directly supplying said engine, said motor vehicle comprising such a control computer.

[0030] Thus, the optimization of the regulation can be carried out regardless of the position of the vehicle.

[0031] The invention will be further detailed by the description of non-limiting embodiments, and on the basis of the appended figures illustrating variants of the invention, in which: - [Fig.l] schematically illustrates the architecture of a motorization assembly, comprising an internal combustion engine, and representing the different elements involved in the invention; - [Fig.2] to [Fig.4] illustrate the prior art: - [Fig.2] is a pressure versus time diagram showing the effects of a problem of saturation of the actuators when driving in cold conditions; - [Fig.3] schematically illustrates a detail of the strategy for activating load regulation by the turbine according to the prior art; - [Fig.4] schematically illustrates a detail of the activation strategy of the re load regulation by the butterfly according to the prior art; - [Fig.5] schematically illustrates the new coordination, according to the invention, of the control of the load by the butterfly or the turbocharger; - [Fig.6] schematically illustrates a detail of the new strategy for activating load regulation by the turbocharger, according to the invention; - [Fig.7] schematically illustrates a detail of the new activation strategy of load regulation by the throttle, according to the invention; - [Fig.8] schematically illustrates a motor vehicle comprising a computer for controlling the regulation of an engine according to [Fig.l], according to the method of the invention.

[0032] The invention relates to the strategy for coordinating the air charge regulation of a turbocharged gasoline internal combustion engine.

[0033] According to the invention, the aim is to avoid situations where the butterfly and turbocharger actuators would be saturated in position, i.e. finding themselves fully open at the same time.

[0034] ) The root cause is related to the non-robustness of the coordination strategy of the re load regulation. And more specifically to an error in estimating the natural boost pressure used to select the activation zone of the throttle or turbocharger. Although the latter can be consolidated by taking into account external conditions, and in particular temperature, there are nevertheless cases where the two actuators always remain saturated. Furthermore, other cases of "actuator saturation" can also be encountered during the life of the vehicle due to aging.

[0035] To avoid ending up with the butterfly actuator and the turbocharger actuator saturated at the same time, the position of these two actuators is taken into account in the strategy for coordinating the air charge regulation. Thus, in the atmospheric zone ZAT, if the butterfly is saturated open while the turbocharger regulation is still deactivated, the latter can then be activated to regain control over the charge regulation. In the same way, in the supercharged zone ZSA, if the turbocharger is saturated open, while the butterfly regulation is still deactivated, the latter can then be activated to regain control over the charge regulation. These additional conditions linked to the saturation of the actuators are used only in the zone where the natural boost pressure is biased or imprecise.In the rest of the motor field, the prior art coordination is used in order to benefit from instantaneous reactivity to the driver's wishes (without waiting to know whether the actuator will be saturated or not).

[0036] The invention proposes a non-intrusive solution, because it complements the prior art solution to address a well-localized weakness. It makes it possible to guarantee the achievement of the torque demand in the limiting operating conditions around the atmospheric / supercharged transition. It also makes it possible to provide robustness with respect to engine aging and to prevent the occurrence of untimely faults.

[0037] [Fig.l] shows the architecture of a motorization assembly comprising an internal combustion engine 1. This engine 1 is turbocharged by the action of a turbine 2 driven by a gas flow in an exhaust line 3, comprising, without limitation, a catalyst 31, an intermediate silencer 32, and a rear silencer 33 opening into the open air. The turbine 2 drives a turbocharger 4, which is supplied with air by an air intake circuit 5, comprising, without limitation, an air box 51 and an air filter 52. The turbine 2 manages the position of the turbocharger 4. This turbocharger 4 is, without limitation, mounted in parallel with a wastegate 4L. The turbocharger 4 supplies a supercharging air circuit 6, directly or through an air cooler 7, to a motorized throttle valve 8 which manages the position of the throttle valve and delivers the air to an air distributor circuit 9 directly supplying the engine 1.

[0038] [Fig.2] is a load diagram as a function of the speed, which schematically illustrates the coordination of the load control by the throttle and the turbo according to the prior art of the load regulation strategy. Three zones are distinguished: at the top of the diagram a supercharged zone ZSA where the load regulation is done solely via the turbocharger, and where the throttle is kept fully open, at the bottom of the diagram an atmospheric zone ZAT (where the load regulation is done solely via the throttle, and where the turbocharger is kept fully open, and a mixed transition zone TAS (between the broken lines), where load regulation can be done via both actuators at the same time; natural boost pressure is present in this mixed transition zone TAS.

[0039] This mixed TAS transition zone should be chosen as narrow as possible in order to promote load regulation with a fully open throttle in order to minimize pumping losses, while absorbing the lack of precision of the natural supercharging model.

[0040] The operating principle of the load regulation coordination strategy according to the prior art is illustrated by [Fig.3] and [Fig.4], which detail the load regulation by the turbine and by the throttle valve respectively.

[0041] According to [Fig.3], the load regulation coordination strategy according to the prior art consists of regulating the load via the turbocharger (coupled to the turbine), and comparing the CPS boost pressure setpoint to the natural boost pressure. If the latter is greater than the estimated natural boost pressure PSNE less a turbocharger bias called “Biais_tur” (representing the width of the mixed transition zone TAS on the side of the atmospheric zone ZAT where the turbocharger is fully open, below the dashed line of [Fig.2] which represents the natural boost pressure), then the turbocharger regulation is activated: ART activation of the turbocharger regulation.

[0042] According to [Fig.4], the load regulation coordination strategy according to the prior art consists of regulating the load via the throttle, and comparing the measurement of the distributor pressure MPR to the natural boost pressure. If the latter is lower than the estimated natural boost pressure PSNE plus a throttle bias called “Biais_pap” (representing the width of the mixed transition zone TAS on the throttle side of the supercharged zone ZSA where the throttle is fully open, above the dashed line of [Fig.2] which represents the natural boost pressure), then the throttle regulation is activated: ARP activation of the throttle regulation.

[0043] We then understand that, if the natural boost pressure model is not biased by more butterfly bias "Biais_pap" or less turbocharger bias "Biais_tur", then the two actuators can never be saturated at the same time because we will always be in the mixed regulation zone. However, we cannot widen this zone indefinitely because of the pumping losses mentioned above.

[0044] It is therefore proposed to widen this zone on one side or the other only if one of the actuators is saturated. This new operation according to the invention is illustrated in [Fig.5],

[0045] [Fig.5] is a load versus speed diagram, which illustrates diagram tically the new coordination, according to the invention, of the control of the load by the butterfly and the turbocharger. This diagram includes the same zones as that of [Fig.2] illustrating the prior art, and the mixed transition zone TAS includes, beyond and on either side of a first lower transition zone PZTI and a first upper transition zone PZTS, corresponding substantially to the lower and upper zones of the transition zone TAS of [Fig.2] and corresponding respectively to the biases Biais_tur and Biais_pap, two other transition zones represented in hatching: a second lower transition zone DZTI and a second upper transition zone DZTS.

[0046] . The throttle bias thresholds “Biais_pap” and turbocharger bias thresholds “Biais_turb”, of the prior art, are replaced respectively by a first butterfly bias value “Biais_l_pap” and a first turbocharger bias value “Biais_l_turb”, defining the first lower transition zone PZTI and the first upper transition zone PZTS.

[0047] Two new thresholds are defined on either side of the dotted line representing the natural boost pressure PSN: a second butterfly bias value “Biais_2_pap” and a second turbocharger bias value “Biais_2_turb”, defining the second lower transition zone DZTI and the second upper transition zone DZTS.

[0048] The new operation of the coordination strategy is defined by [Fig.6] and [Fig.7],

[0049] [Fig.6] schematically illustrates a detail of the new strategy for activating load regulation by the turbocharger. If the boost pressure setpoint CPS is not higher than the estimated natural boost pressure PSNE less a first turbocharger bias value “Biais_l_tur”, but is higher than the estimated natural boost pressure PSNE less a second turbocharger bias value “Biais_2_tur” (lower hatched area of ​​[Fig.5]) and the throttle position setpoint CSP is higher than a throttle threshold SP “threshold_pap” (saturated throttle open), then load regulation via the turbocharger is reactivated: ART activation of turbocharger regulation.

[0050] [Fig.7] schematically illustrates a detail of the new activation strategy of the load regulation by the throttle. Similarly, if the distributor pressure measurement MPR is not lower than the estimated natural boost pressure PSNE plus a first throttle bias value “Biais_l_pap”, but lower than the estimated natural boost pressure PSNE plus a second throttle bias value “Biais_2_pap” (upper hatched area of ​​[Fig.5]) and the turbocharger position, called turbocharger setpoint CT, is lower than a turbocharger threshold “threshold_turbo” ST (saturated turbo open), then the load regulation via the throttle is reactivated: ARP activation of throttle regulation.

[0051] According to the new strategy, the mixed TAS transition zone defined by the thresholds corresponding to the first butterfly bias value “Biais_l_pap” and to the first turbocharger bias value “Biais_l_turb” may be chosen to be narrower than that of the prior art defined by the butterfly bias “Biais_pap” and the turbocharger bias “Biais_tur”, because the risk of saturation of the actuators is now removed.

[0052] Finally, for implementation reasons, a hysteresis on the position of the actuators is introduced in order to eliminate or minimize possible noises that could disturb the coordination strategy.

[0053] The new strategy is compared to the prior art strategy on a representative vehicle run, which shows that the new Booleans for activating the control loops are now activated correctly.

[0054] In short, the invention improves the prior art, and makes it possible to consolidate the coordination of actuator control for gasoline internal combustion engines equipped with a variable geometry turbocharger. It makes it possible to guarantee torque tracking in the atmospheric / supercharged transition zone and during engine aging. Finally, it can limit pumping losses, and consequently fuel consumption because it makes it possible to reduce the size of the dual regulation zone (throttle and turbocharger). This solution is advantageous for all applications where variable geometry turbocharging (TGV) is used. It also remains valid for applications with fixed geometry turbocharging (TGF).

Claims

Claims

1. Method for coordinating the regulation of the air load of a gasoline internal combustion engine (1), turbocharged by the action of a turbine (2) driven by a gas flow in an exhaust line (3) and which turbine (2) drives a turbocharger (4) supplied with air by an air intake circuit (5) and supplying a supercharging air circuit (6), directly or through an air cooler (7), to a motorized throttle (8) delivering the air to an air distributor circuit (9) directly supplying said engine (1), according to which the engine load is regulated, which is variable between the lowest load level in an atmospheric zone (ZAT) corresponding to the turbocharger fully open and where the throttle is regulated, and the highest load level in a supercharged zone (ZSA) corresponding to the throttle fully open and where the turbocharger is regulated,passing through an intermediate load level in a mixed transition zone (TAS), where the throttle and / or the turbocharger can be regulated, where the pressure is variable around a natural boost pressure, a first throttle bias value "Biais_l_pap" in a first upper transition zone (PZTS) from the mixed transition zone (TAS) to the second supercharged zone (ZSA), and a first turbocharger bias value "Biais_l_tur" in a first lower transition zone (PZTI) from the mixed transition zone (TAS) to the first atmospheric zone (ZAT), characterized in that, to avoid simultaneous regulation by the throttle and the turbocharger, the mixed transition zone (TAS) is widened by at least one second transition zone, a second upper transition zone (DZTS) between the first upper transition zone (PZTS) of the mixed transition zone (TAS) and the supercharged zone (ZSA),and / or a second lower transition zone (DZTI) between the first lower transition zone (PZTI) of the mixed transition zone (TAS) and the atmospheric zone (ZAT), only if one of the turbine and / or butterfly actuators is saturated, and where the pressure is variable around a natural boost pressure (PSN), a second butterfly bias value “Biais_2_pap” towards the second supercharged zone (ZSA), and a second turbocharger bias value “Biais_2_tur” towards the first atmospheric zone (ZAT), and where the load regulation is activated by the turbocharger if the, boost pressure setpoint (CPS) is not higher than the estimated natural boost pressure (ESBP) less the first turbocharger bias value “Biais_l_tur”, and if the boost pressure setpoint (CPS) is higher than the estimated natural boost pressure (ESBP) less the second turbocharger bias value “Biais_2_tur” and the throttle setpoint position (CP) is higher than a throttle threshold (SP) “threshold_pap” corresponding to the open saturated throttle, while load regulation by the throttle is activated if the distributor pressure measurement (MPR) is not lower than the estimated natural boost pressure (ESBP) plus the first throttle bias value “Biais_l_pap”,and if the distributor pressure measurement (MPR) is lower than the estimated natural boost pressure (PSNE) plus a “Biais_2_pap” and the turbocharger setpoint position (CT) is lower than a turbocharger threshold (ST) “seuil_turbo” corresponding to the open saturated turbocharger.,

2. Method according to claim 1 characterized in that the first throttle bias value “Biais_l_pap” and the first turbocharger bias value “Biais_l_tur” are minimized by simulation.

3. Method according to claim 1 characterized in that the first throttle bias value "Biais_l_pap" and the first turbocharger bias value "Biais_l_tur" are chosen to be lower than the throttle bias values ​​"Biais_pap" and turbocharger bias values ​​"Biais_tur" in a simulation where the mixed transition zone (TAS) is limited to the first upper transition zone (PZTS) and the first lower transition zone (PZTI), without a second upper transition zone (DZTS) or a second lower transition zone (DZTI).

4. Method according to one of claims 1 to 3 characterized in that the second butterfly bias value “Biais_2_pap” and the second turbocharger bias value “Biais_2_tur” are minimized by simulation.

5. Method according to one of claims 1 to 4 characterized in that the first butterfly bias value “Biais_l_pap” is chosen to be equal to the first turbocharger bias value “Biais_l_tur”.

6. Method according to one of claims 1 to 5 characterized in that the second butterfly bias value “Biais_2_pap” is chosen to be equal to the second turbocharger bias value “Biais_2_tur”.

7. Method according to one of claims 1 to 6 characterized in that introduces hysteresis on the position of the actuators in order to eliminate or minimize possible noise that could disrupt the coordination strategy.

8. Control computer (100) for a motor vehicle (1000) comprising a memory storing program instructions for implementing the method according to one of claims 1 to 7 and for controlling the motorized throttle (8) and the turbocharger (4).

9. Motor vehicle (1000) comprising a turbocharged gasoline internal combustion engine (1) driven by the action of a turbine (2) driven by a gas flow in an exhaust line (3) and which turbine (2) drives a turbocharger (4) supplied with air by an air intake circuit (5) and supplying a supercharging air circuit (6), directly or through an air cooler (7), to a motorized butterfly valve (8) delivering the air to an air distributor circuit (9) directly supplying said engine (1), said motor vehicle (1000) comprising a control computer (100) according to claim 8.

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