METHOD FOR ACTIVATING A CRAWL MOTION MODE OF A VEHICLE UNDER BRAKING ON AN INCLINE

Abstract

The invention relates to a method for controlling a so-called "creeping" mode of a vehicle, suitable for moving said vehicle at low speed by supplying torque produced by a powertrain without driver action on a brake or accelerator pedal. The method comprises: - a step for measuring or estimating a master cylinder pressure (Pmc), - a step for measuring or estimating a slope level, and - a step for activating the creeping mode when the master cylinder pressure (Pmc) falls below an activation threshold (Sact), said activation threshold (Sact) being a function of a slope level. Figure 2

Description

Title of the invention: METHOD FOR ACTIVATING A CRAWLING MODE OF A VEHICLE UNDER A BRAKING ON A SLOPE

[0001] The present invention relates to a method for activating a creeping mode of a vehicle under braking on a slope. The invention finds a particularly advantageous application with motor vehicles which are said to be automated.

[0002] Here, the term "automated vehicle" means both a vehicle comprising a system for controlling components making it possible to automatically adapt the gear ratio of its powertrain (or GMP) to the wheels (such as, for example, a robotized gearbox), and a vehicle not requiring this type of control system (such as, for example, an all-electric GMP vehicle). Consequently, the invention relates in particular to vehicles with an all-electric powertrain, vehicles with a hybrid powertrain, and vehicles with a powertrain with a gear ratio automation mechanism (such as, for example, a robotized manual gearbox, a dual-clutch gearbox, an automatic gearbox or a continuously variable gearbox).

[0003] Furthermore, herein, the term "creeping mode" (or "crawling") is understood to mean a mode of operation of the GMP which allows the vehicle to be moved, at low speed (typically 5 to 12 km / h on the flat) and autonomously, thanks to the supply of a variable torque as soon as the driver no longer acts on the brake pedal and accelerator pedal when the vehicle is traveling at low speed. This autonomous mode of movement (or rolling) (i.e. without driver intervention) is inherent to vehicles with automatic gearboxes with torque converters and in fact allows the driver to maneuver his vehicle more easily by temporarily operating only the brake pedal.

[0004] The creep mode has been implemented in many other automated vehicles in order to reproduce the mechanical operation of the creep mode present on powertrains equipped with an automated gearbox comprising a torque converter. The implementation of the control strategies of existing powertrains induces a risk of the vehicle rolling backward when the creep function is deactivated while the vehicle is on a slope.

[0005] The invention aims to effectively remedy this drawback by proposing a method for controlling a so-called "creeping" mode of a vehicle, capable of moving said vehicle at low speed by supplying a torque produced by a motor group. propellant without action of a driver on a brake pedal or an accelerator pedal, said method comprising: - a step of measuring or estimating a master cylinder pressure, - a step of measuring or estimating a slope level, and - a step of activating the creeping mode when the master cylinder pressure becomes lower than an activation threshold, said activation threshold being a function of a slope level.

[0006] The invention thus makes it possible to reduce the occurrence of rollback by activating the creeping mode as soon as braking is no longer sufficient. The invention also makes it possible to control acoustic and vibration disturbances without impacting the energy consumption of the powertrain. This method can be implemented regardless of the speed of the vehicle.

[0007] According to one implementation of the invention, the greater the slope level, the greater the activation threshold.

[0008] According to an implementation of the invention, for a slope level of the order of 5%, the activation threshold is of the order of 5x105Pa, for a slope level of the order of 30%, the activation threshold is of the order of 3x106 Pa, and for a slope level between 5% and 30%, the activation threshold is proportional to a slope level.

[0009] According to one implementation of the invention, the activation threshold depends on a direction of travel of the vehicle and / or a position of a gear lever corresponding to a desired direction of travel of the vehicle.

[0010] According to one implementation of the invention, the activation threshold depends on at least one parameter of the motor vehicle and / or at least one external parameter.

[0011] According to one implementation of the invention, the parameter of the motor vehicle is the speed or the acceleration, and / or at least one external parameter, such as an external temperature.

[0012] According to one implementation of the invention, the master cylinder pressure is capable of being modified by pressing the brake pedal by a driver or automatically by a computer, such as an adaptive cruise control.

[0013] The invention also relates to a computer comprising a memory storing software instructions for implementing the method as previously defined.

[0014] The invention further relates to a motor vehicle comprising a computer as defined above.

[0015] According to one embodiment of the invention, the vehicle comprises a dual-clutch gearbox.

[0016] The invention will be better understood upon reading the following description and examining the accompanying figures. These figures are given for illustrative purposes only but in no way limiting the invention.

[0017] [Fig. 1] [Fig.l] is a schematic representation of a powertrain implementing a method according to the invention for activating a creeping mode;

[0018] [Fig.2] [Fig.2] is a time diagram illustrating the implementation of the method according to the invention for activating a creeping mode under braking on a slope.

[0019] [Fig.l] shows a hybrid powertrain 10 of a motor vehicle comprising a heat engine 11 and an electric transmission device 12 mounted on a wheel set 13, in particular a front wheel set.

[0020] The electric transmission device 12 comprises a second torque producer, such as a rotating electric machine 15 and a dual-clutch gearbox 16 comprising two clutches K1, K2 for changing gear ratios. The rotating electric machine 15 is arranged at the input of the dual-clutch gearbox 16.

[0021] The gearbox 16 comprises at least one primary shaft 16.1, 16.1' and one secondary shaft 16.2. In this case, the gearbox 16 comprises a first primary shaft 16.1 associated with a first set of gear ratios, for example ratios 1-3-5, and connected to the clutch KL. A second primary shaft 16.1' is associated with a second set of gear ratios, for example ratios 2-4-6-7, and connected to the clutch K2. The secondary shaft 16.2 of the gearbox 16 is connected to the wheels via a differential and a lowering axle (not shown).

[0022] The clutch KO is a clutch for connecting and disconnecting the heat engine 11. The clutch KO is capable of selectively connecting the heat engine 11 to the gearbox 16 when said clutch KO is in the closed state and of isolating the heat engine 11 from the gearbox 16 when said clutch KO is in the open state. When a torque from the heat engine 11 is transmitted to the wheels, the clutch KO is closed and the clutches K1 and K2 are alternately closed depending on the gear engaged. For this purpose, the clutch KO is arranged between the heat engine 11 and the rotating electrical machine 15. The isolation of the heat engine 11 from the gearbox 16 and therefore from the wheels is required in particular when the vehicle operates in a pure electric driving mode. The clutch KO is associated with a flywheel 17.

[0023] The rotating electrical machine 15 is mounted between the clutch KO and the gear change clutches K1, K2 of the gearbox 16. The rotating electrical machine 15 can be connected to the input of the gearbox 16 via a belt or chain reduction unit 18.

[0024] The rotating electrical machine 15 is capable of transforming electrical energy from a traction battery 19 into mechanical energy to provide traction. of the vehicle by providing torque to the wheels of the vehicle. The rotating electrical machine 15 is also capable of operating in a generator mode in which the rotating electrical machine 15 transforms mechanical energy into electrical energy making it possible to recharge the traction battery 19, in particular during a regenerative braking phase.

[0025] An engine computer 21 is capable of controlling the powertrain 10, in particular controlling the torque section of the engine 11, the electric machine 15, as well as opening, closing or sliding the clutches KO, K1 and K2.

[0026] The engine computer 21 or a dedicated computer comprises a memory storing software instructions for implementing the method according to the invention for activating a creeping mode described below with reference to [Fig. 2]. The creeping mode makes it possible to move the vehicle at low speed by supplying a torque produced by the powertrain 10 without action by a driver on a brake pedal or an accelerator pedal.

[0027] The method comprises a step of measuring or estimating a master cylinder pressure Pmc. The pressure Pmc is representative of a braking force applied to wheels of the vehicle. The master cylinder pressure Pmc is capable of being modified by pressing the brake pedal by a driver or automatically by a computer, such as an adaptive cruise control.

[0028] The method comprises a step of measuring or estimating a slope level. The slope level is measured or estimated for the slope on which the motor vehicle is traveling. The slope level expressed in percent is estimated using an accelerometer, via the subtraction of the acceleration measured by the wheels. The accelerometer measures the Earth's gravity proportionally to the inclination, in particular 0 m / s2 at 0°, 9.81 m / s2 at 90°. This measurement is then converted into a slope percentage.

[0029] The method further comprises a step of activating the creeping mode when the master cylinder pressure Pmc becomes lower than an activation threshold Sact. The activation threshold Sact is a function of a slope level.

[0030] Advantageously, the greater the slope level, the greater the activation threshold Sact. According to an exemplary implementation, for a slope level of the order of 5%, the activation threshold Sact is of the order of 5xl05Pa (5 bars). For a slope level of the order of 30%, the activation threshold Sact is of the order of 3xl06 Pa (30 bars). For a slope level between 5% and 30%, the activation threshold Sact is proportional to a slope level.

[0031] As illustrated in [Fig.2], for a given slope level, as long as the master cylinder pressure is higher than the activation threshold Sact, the creep mode is deactivated (the creep activation signal Act_Ramp is 0). When the master cylinder pressure falls below the activation threshold Sact at time T1, the creep mode is activated (the activation signal Act_Ramp goes to 1). At time T2, the master cylinder pressure rises above a deactivation threshold Sdes, so that the activation signal Act_Ramp goes back to 0. The deactivation threshold Sdes can be higher than the activation threshold Sact.

[0032] The activation threshold Sact may depend on a direction of travel of the vehicle and / or a position of a gear lever corresponding to a desired direction of travel of the vehicle. The gear lever may in particular take a position R corresponding to the “Reverse” position and therefore to reverse gear or a position D corresponding to the “Drive” position and therefore to forward gear.

[0033] The activation threshold Sact may also depend on at least one parameter of the motor vehicle and / or at least one external parameter. The parameter of the motor vehicle is the speed or the acceleration, and / or at least one external parameter, such as an external temperature.

Claims

Claims

1. Method for controlling a so-called "creeping" mode of a vehicle, capable of moving said vehicle at low speed by supplying a torque produced by a powertrain (10) without action by a driver on a brake pedal or an accelerator pedal, characterized in that said method comprises: - a step of measuring or estimating a master cylinder pressure (Pmc), - a step of measuring or estimating a slope level and - a step of activating the creeping mode when the master cylinder pressure (Pmc) becomes lower than an activation threshold (Sact), said activation threshold (Sact) being a function of a slope level.

2. Method according to claim 1, characterized in that the greater the slope level, the greater the activation threshold (Sact).

3. Method according to claim 2, characterized in that, for a slope level of the order of 5%, the activation threshold (Sact) is of the order of 5xl05Pa (5 bars), for a slope level of the order of 30%, the activation threshold (Sact) is of the order of 3xl06 Pa (30 bars), and for a slope level between 5% and 30%, the activation threshold (Sact) is proportional to a slope level.

4. Method according to any one of claims 1 to 3, characterized in that the activation threshold (Sact) depends on a direction of travel of the vehicle and / or a position of a gear lever corresponding to a desired direction of travel of the vehicle.

5. Method according to any one of claims 1 to 4, characterized in that the activation threshold (Sact) depends on at least one parameter of the motor vehicle and / or at least one external parameter.

6. Method according to claim 5, characterized in that the parameter of the motor vehicle is the speed or the acceleration, and / or at least one external parameter, such as an external temperature.

7. Method according to any one of claims 1 to 6, characterized in that the master cylinder pressure (Pmc) is capable of being modified by pressing the brake pedal by a driver or automatically by a computer, such as an adaptive cruise control.

8. Computer (21) comprising a memory storing software instructions for implementing the method according to any one of the preceding claims.

9. Motor vehicle comprising a computer (21) according to the preceding claim.

10. Vehicle according to claim 9, characterized in that it comprises a gearbox (16) with double clutch (Kl, K2).

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