METHOD FOR DEACTIVATING A VEHICLE'S CROWDING MODE 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 input on a brake or accelerator pedal. Once the creeping mode is activated, 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 deactivating the creeping mode when the master cylinder pressure (Pmc) exceeds a deactivation threshold (Sdes), said deactivation threshold (Sdes) ​​being a function of the slope level. Figure 2

Description

Title of the invention: METHOD FOR DEACTIVATING A CREEPING MODE OF A VEHICLE UNDER A BRAKING ON A SLOPE

[0001] The present invention relates to a method for deactivating 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 back 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, the creeping mode being activated, said method comprises: - a step of measuring or estimating a master cylinder pressure, - a step of measuring or estimating a slope level, and - a step of deactivating the creeping mode when the master cylinder pressure becomes higher than a deactivation threshold, said deactivation threshold being a function of the slope level.

[0006] The invention thus makes it possible to reduce the occurrence of vehicle rollback on a slope by controlling the deactivation of the creeping mode according to the level of slope. The invention also makes it possible to control acoustic and vibration disturbances without impacting the energy consumption of the powertrain. This strategy even offers the possibility of never deactivating creeping on a very steep slope. This allows the driver to maintain torque at the wheel and then be able to take off better on a steep slope.

[0007] According to one implementation of the invention, said method is implemented when the speed of the vehicle is lower than a speed threshold.

[0008] According to one implementation of the invention, the greater the slope level, the greater the deactivation threshold.

[0009] According to one implementation of the invention, said method comprises a step of time confirmation of deactivation, so that the creeping mode is deactivated only when the master cylinder pressure becomes greater than the deactivation threshold for a duration greater than a duration threshold, for example of the order of 3s.

[0010] According to one implementation of the invention, the creep mode is reactivated if the master cylinder pressure becomes lower than a reactivation authorization threshold and if a creep mode reactivation action occurs.

[0011] According to one implementation of the invention, the action of reactivating the creeping mode is chosen from: releasing a brake pedal, pressing an accelerator pedal, or acting on a gear lever.

[0012] According to one implementation of the invention, the deactivation threshold and the reactivation authorization threshold are configured in the form of hysteresis so that, for a given slope level, the creeping mode is deactivated when the master cylinder pressure becomes greater than the deactivation threshold and this deactivation is maintained until the master cylinder pressure becomes lower than the reactivation authorization threshold, lower than the deactivation threshold.

[0013] According to an implementation of the invention, the deactivation threshold and the reactivation authorization threshold depend on a direction of travel of the vehicle and / or a position of a gear lever corresponding to a desired direction of movement of the vehicle.

[0014] 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.

[0015] The invention also relates to a calculator comprising a memory storing software instructions for implementing the method as previously defined.

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

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

[0018] [Fig.2] [Fig.2] is a time diagram illustrating the implementation of the method according to the invention for deactivating a creeping mode as a function of a master cylinder pressure.

[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 engine thermal engine 11 and the rotating electrical machine 15. The insulation of the thermal engine 11 from the gearbox 16 and therefore from the wheels is required in particular when the vehicle is operating in a pure electric driving mode. The KO clutch 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 deactivating a creeping mode described below with reference to [Fig.2].

[0027] The so-called "creeping" mode of a vehicle, suitable for moving said vehicle at low speed by supplying torque produced by a powertrain 10 without action by a driver on a brake pedal or an accelerator pedal.

[0028] With the creeping mode activated, said method comprises a step of measuring or estimating a master cylinder pressure. This master cylinder pressure is representative of a braking force applied to wheels of the vehicle. 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.

[0029] 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 0.01 m / s2 at 0°, 9.81 m / s2 at 90°. This measurement is then converted into a slope percentage.

[0030] The method further comprises a step of deactivating the operating mode. creeping when the master cylinder pressure becomes higher than a deactivation threshold Sdes, said deactivation threshold (Sdes) ​​being a function of a slope level. Preferably, the method is implemented when the vehicle speed is lower than a speed threshold, for example of the order of 1km / h.

[0031] The greater the slope level, the greater the deactivation threshold Sdes. For example, for a slope level of the order of 5%, the deactivation threshold Sdes is of the order of 5 bars (5xl06 Pa). For a slope level of the order of 30%, the deactivation threshold Sdes is of the order of 30 bars (3xl06 Pa). For a slope level between 5% and 30%, the deactivation threshold Sdes is proportional to the slope level.

[0032] The method may comprise a step of time confirmation of deactivation, so that the creeping mode is deactivated only when the master cylinder pressure becomes greater than the deactivation threshold Sdes for a duration greater than a duration threshold, for example of the order of 3s.

[0033] The creep mode is reactivated if the master cylinder pressure falls below a reactivation authorization threshold Jump and if a creep mode reactivation action occurs. The creep mode reactivation action is chosen from: releasing a brake pedal, pressing an accelerator pedal, or an action on a gear lever, in particular a shift to position D (for Drive in English).

[0034] Advantageously, the deactivation threshold Sdes and the reactivation authorization threshold Saut are configured in the form of hysteresis so that, for a given slope level, the creeping mode is deactivated when the master cylinder pressure becomes greater than the deactivation threshold Sdes and this deactivation is maintained until the master cylinder pressure becomes lower than the reactivation authorization threshold Saut, lower than the deactivation threshold Sdes.

[0035] As illustrated in [Fig.2], as long as the master cylinder pressure Pmc is below the deactivation threshold Sdes, the creep mode can be activated (the creep deactivation signal Des_Ramp is equal to 0). When the master cylinder pressure Pmc exceeds the deactivation threshold Sdes at time T1, the creep mode is deactivated (the deactivation signal Des_Ramp goes to 1). At time T2, the master cylinder pressure Pmc falls back below the reactivation authorization threshold Saut, so that the deactivation signal Des_Ramp goes back to 0. From T2, the creep mode can be reactivated if a reactivation action (releasing a brake pedal, pressing the accelerator pedal, or action on a gear lever such as a shift to position D (for "Drive" in English) occurs.

[0036] For example, for a slope level of 30%, the deactivation threshold Sdes is the order of 30 bars (3xl06 Pa) and the reactivation authorization threshold is of the order of 20 bars (2xl06 Pa).

[0037] The deactivation threshold Sdes and the reactivation authorization threshold Saut 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.

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, the creeping mode being activated, said method comprises: - a step of measuring or estimating a master cylinder pressure, - a step of measuring or estimating a slope level, and - a step of deactivating the creeping mode when the master cylinder pressure becomes greater than a deactivation threshold (Sdes), said deactivation threshold (Sdes) ​​being a function of the slope level.

2. Method according to claim 1, characterized in that it is implemented when the speed of the vehicle is lower than a speed threshold.

3. Method according to claim 1 or 2, characterized in that the greater the slope level, the greater the deactivation threshold (Sdes).

4. Method according to any one of claims 1 to 3, characterized in that it comprises a step of temporal confirmation of deactivation, so that the creeping mode is deactivated only when the master cylinder pressure becomes greater than the deactivation threshold (Sdes) ​​for a duration greater than a duration threshold.

5. Method according to any one of claims 1 to 4, characterized in that the creep mode is reactivated if the master cylinder pressure becomes lower than a reactivation authorization threshold (Jump) and if a creep mode reactivation action occurs.

6. Method according to claim 5, characterized in that the action of reactivating the creeping mode is chosen from: releasing a brake pedal, pressing an accelerator pedal, or acting on a gear lever.

7. Method according to claim 6, characterized in that the deactivation threshold (Sdes) ​​and the reactivation authorization threshold (Jump) are configured in the form of hysteresis so that, for a given slope level, the creeping walking mode is deactivated when the pressure of master cylinder pressure becomes higher than the deactivation threshold (Sdes) ​​and this deactivation is maintained until the master cylinder pressure becomes lower than the reactivation authorization threshold (Jump), lower than the deactivation threshold (Sdes).

8. Method according to any one of claims 1 to 7, characterized in that the deactivation threshold (Sdes) ​​and the reactivation authorization threshold (Jump) 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.

9. Method according to any one of claims 1 to 8, characterized in that 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.

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

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