Method for deactivating a creep mode of a vehicle as a function of an oil temperature of the gearbox

Abstract

The invention relates to a method for controlling a mode referred to as a "creep" mode of a vehicle, capable of moving the vehicle at low speed by delivering a torque produced by a powertrain (10) without a driver acting on a brake pedal or an accelerator pedal, the powertrain (10) comprising a gearbox (16) that comprises at least one clutch (K1, K2) and contains oil, the method comprising: - a step of measuring or estimating an oil temperature of the gearbox (16); and - a step of deactivating the creep mode if the oil temperature of the gearbox (16) is below a low deactivation threshold or above a high deactivation threshold.

Description

DESCRIPTION TITLE: METHOD FOR DEACTIVATING A VEHICLE CRAWLING MODE BASED ON GEARBOX OIL TEMPERATURE

[0001] The present invention claims priority from French application No. 2307732 filed on 19.07.2023, the content of which (text, drawings and claims) is incorporated herein by reference.

[0002] The present invention relates to a method for deactivating a creeping mode of a vehicle as a function of a gearbox oil temperature. The invention finds a particularly advantageous application with motor vehicles which are said to be automated.

[0003] The term "automated vehicle" herein refers to both a vehicle comprising a system for controlling components enabling the gear ratio of its powertrain (or GMP) to be automatically adapted 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 having 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).

[0004] Furthermore, the term "creeping mode" (or "crawling") is used here to mean a mode of operation of the powertrain 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 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 in vehicles with automatic torque converter gearboxes, which allows the driver to maneuver their vehicle more easily by temporarily operating only the brake pedal.

[0005] Creeping mode has been implemented in many other automated vehicles to replicate the mechanical operation of creeping mode found on powertrains equipped with an automated gearbox incorporating a torque converter.

[0006] When the driver wants to stop his vehicle, he must therefore apply braking that opposes the creeping torque. However, when the vehicle is stationary and a creeping torque is present on a powertrain equipped with at least one clutch, the latter can see its temperature increase significantly. When the cooling oil of a clutch is too hot, it cannot optimally evacuate the calories to cool the clutch. When the oil is too cold, its high viscosity does not allow it to circulate properly inside the oil circuit to cool the clutch.

[0007] The invention aims to effectively remedy the aforementioned drawbacks 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 sliding of a clutch of a powertrain without action by a driver on a brake pedal or an accelerator pedal, said powertrain comprising a gearbox comprising at least one clutch and containing oil in common for the gearbox (16) and for cooling this clutch (K1, K2), said method comprising: - a step of measuring or estimating the gearbox oil temperature and - a step of deactivating the creeping mode if the gearbox oil temperature is below a low deactivation threshold or is above a high deactivation threshold.

[0008] The invention thus makes it possible to avoid overheating of the clutch due to oil that is too cold or too hot and cannot effectively cool the clutch. The invention is also economical in that it can be implemented by inexpensive software implementation.

[0009] According to one implementation of the invention, the creep mode is reactivated if the oil temperature of the gearbox becomes higher than a low reactivation authorization threshold or lower than a high reactivation authorization threshold and if a creep mode reactivation action occurs.

[0010] 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.

[0011] According to one implementation of the invention, the low deactivation threshold and the low reactivation authorization threshold are configured as hysteresis, so that the creep mode is deactivated when the gearbox oil temperature becomes lower than the low deactivation threshold and the deactivation of the creep mode is maintained until the gearbox oil temperature rises again above the low reactivation authorization threshold higher than the low deactivation threshold.

[0012] According to one implementation of the invention, the low deactivation threshold is of the order of -25°C and the low reactivation authorization threshold is of the order of -20°C.

[0013] According to one implementation of the invention, the high deactivation threshold and the high reactivation authorization threshold are configured in the form of hysteresis, so that the creep mode is deactivated when the temperature of the gearbox oil becomes higher than the high deactivation threshold and this deactivation of the creep mode is maintained until the temperature of the gearbox oil becomes lower than the high reactivation authorization threshold lower than the high deactivation threshold.

[0014] According to one implementation of the invention, the high deactivation threshold is of the order of 140°C and the low reactivation authorization threshold is of the order of 100°C.

[0015] According to one implementation of the invention, the low deactivation threshold and the high deactivation threshold depend on at least one parameter of the motor vehicle, such as speed or acceleration, and / or at least one external parameter, such as an external temperature.

[0016] The invention also relates to a calculator comprising a memory storing software instructions for implementing the method as previously defined.

[0017] The invention further relates to a motor vehicle comprising a computer as defined above.

[0018] The invention will be better understood by reading the following description and examining the accompanying figures. These figures are given only for illustrative purposes but in no way limit the invention.

[0019] [Fig. 1] Figure 1 is a schematic representation of a powertrain implementing a method according to the invention for deactivating a creeping mode;

[0020] [Fig. 2a] Figure 2a is a time diagram illustrating the implementation of the method according to the invention for deactivating a creeping walking mode on high thresholds;

[0021] [Fig. 2b] Figure 2b is a time diagram illustrating the implementation of the method according to the invention for deactivating a creeping walking mode on low thresholds.

[0022] Figure 1 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.

[0023] 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.

[0024] 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 gear ratios 1-3-5, and connected to the clutch K1. A second primary shaft 16.1' is associated with a second set of gear ratios, for example gear 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).

[0025] The KO clutch is a clutch for connecting and disconnecting the heat engine 11. The KO clutch is capable of selectively connecting the heat engine 11 to the gearbox 16 when said KO clutch is in the closed state and of isolating the heat engine 11 from the gearbox 16 when said KO clutch is in the open state. When a torque from the heat engine 11 is transmitted to the wheels, the KO clutch is closed and the clutches K1 and K2 are alternately closed depending on the gear engaged. For this purpose, the KO clutch 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 is operating in a pure electric driving mode. The KO clutch is associated with a flywheel 17.

[0026] The rotating electrical machine 15 is mounted between the clutch KO and the clutches K1, K2 for changing gears 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 assembly 18.

[0027] 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.

[0028] 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.

[0029] The engine computer 21 or a dedicated computer comprises a memory storing software instructions for implementing the method according to the invention for deactivating the creeping mode described below with reference to FIGS. 2a and 2b.

[0030] The method is capable of controlling a so-called "creeping" mode of the vehicle, capable of moving said vehicle at low speed by providing a torque produced by the powertrain 10 without the driver acting on a brake pedal or an accelerator pedal.

[0031] This mode, called "creeping" of the vehicle, is suitable for moving said vehicle at low speed by supplying a torque produced by sliding of one of the two clutches K1, K2 without action by a driver on a brake pedal or an accelerator pedal, the gearbox containing oil in common for the gearbox 16 and for cooling this clutch K1, K2.

[0032] The method comprises a step of measuring or estimating an oil temperature of the gearbox 16 and a step of deactivating the creep mode if the gearbox oil temperature 16 is below a low deactivation threshold Sdes B or is above a high deactivation threshold Sdes_H.

[0033] The creep mode is reactivated if the oil temperature of the gearbox 16 becomes higher than a low reactivation authorization threshold Jump_B or lower than a high reactivation authorization threshold Jump_H 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 acting on a gear lever, such as shifting to position "D" (for "Drive" in English).

[0034] Preferably, the high deactivation threshold Sdes_H and the high reactivation authorization threshold Saut_H are configured in the form of hysteresis, so that the creep mode is deactivated when the oil temperature of the gearbox 16 becomes higher than the high deactivation threshold Sdes_H and this deactivation of the creep mode is maintained until the oil temperature of the gearbox 16 becomes lower than the high reactivation authorization threshold Saut_H lower than the high deactivation threshold Sdes_H.

[0035] As illustrated in Figure 2a, as long as the oil temperature Th is below the high deactivation threshold Sdes_H, the creep mode can be activated (the creep deactivation signal Des Ramp is equal to 0). When the oil temperature Th exceeds the high deactivation threshold Sdes_H at time T1, the creep mode is deactivated (the deactivation signal Des_Ramp goes to 1). At time T2, the oil temperature Th falls back below the high reactivation authorization threshold Saut H 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 acting on a gear lever) occurs.

[0036] Following an implementation example, the high deactivation threshold Sdes_H is of the order of 140°C and the low reactivation authorization threshold Jump_B is of the order of 100°C. By "of the order of" we mean a possible variation of plus or minus 10% around the indicated value.

[0037] Preferably, the low deactivation threshold Sdes_B and the low reactivation authorization threshold Saut_B are configured in the form of hysteresis, so that the creep mode is deactivated when the oil temperature of the gearbox 16 becomes lower than the low deactivation threshold Sdes_B and the deactivation of the creep mode is maintained until the oil temperature of the gearbox 16 returns above the low reactivation authorization threshold Saut_B higher than the low deactivation threshold Sdes_B. According to an exemplary implementation, the low deactivation threshold Sdes_B is of the order of -25°C and the low reactivation authorization threshold Saut_B is of the order of -20°C.

[0038] As illustrated in Figure 2b, as long as the oil temperature Th is below the low reactivation authorization threshold Saut_B, the creeping mode is deactivated (the deactivation signal Des_Ramp is equal to 1). When the oil temperature Th exceeds the low reactivation authorization threshold Saut_B at time T1, the creeping deactivation signal Des_Ramp goes to 0. Between times T1 and T2, the creeping mode can be reactivated if a reactivation action (releasing a brake pedal, pressing the accelerator pedal, or acting on a gear lever) occurs. At time T2, the oil temperature Th falls back below the low deactivation threshold Sdes_B so that the creeping deactivation signal Des_Ramp goes back to 1. Following an implementation example, the high deactivation threshold Sdes_H is of the order of 140°C and the low reactivation authorization threshold Saut_B is of the order of 100°C.

[0039] The low deactivation threshold Sdes_B and the high deactivation threshold Sdes_H may depend on at least one parameter of the motor vehicle, such as speed or 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 sliding of a clutch (K1, K2) of a powertrain (10) without action by a driver on a brake pedal or an accelerator pedal, said powertrain (10) comprising a gearbox (16) comprising at least the clutch (K1, K2) and containing oil in common for the gearbox (16) and for cooling this clutch (K1, K2), characterized in that said method comprises: - a step of measuring or estimating the oil temperature of the gearbox (16) and - a step of deactivating the creeping mode if the oil temperature of the gearbox (16) is lower than a low deactivation threshold (Sdes_B) or is higher than a high deactivation threshold (Sdes_H).

2. Method according to claim 1, characterized in that the creeping mode is reactivated if the oil temperature of the gearbox (16) becomes higher than a low reactivation authorization threshold (Jump_B) or lower than a high reactivation authorization threshold (Jump_H) and if an action of reactivating the creeping mode occurs.

3. Method according to claim 2, 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.

4. Method according to claim 2 or 3, characterized in that the low deactivation threshold (Sdes_B) and the low reactivation authorization threshold (Saut_B) are configured as hysteresis, so that the creep mode is deactivated when the oil temperature of the gearbox (16) becomes lower than the low deactivation threshold (Sdes_B) and the deactivation of the creep mode is maintained until the oil temperature of the gearbox (16) goes back above the low reactivation authorization threshold (Jump B) higher than the low deactivation threshold (Sdes B).

5. Method according to claim 4, characterized in that the low deactivation threshold (Sdes_B) is of the order of -25°C and the low reactivation authorization threshold (Saut_B) is of the order of -20°C.

6. Method according to any one of claims 2 to 4, characterized in that the high deactivation threshold (Sdes_H) and the high reactivation authorization threshold (Saut_H) are configured in the form of hysteresis, so that the creep mode is deactivated when the oil temperature of the gearbox (16) becomes higher than the high deactivation threshold (Sdes_H) and this deactivation of the creep mode is maintained until the oil temperature of the gearbox (16) becomes lower than the high reactivation authorization threshold (Saut_H) lower than the high deactivation threshold (Sdes_H).

7. Method according to claim 6, characterized in that the high deactivation threshold (Sdes H) is of the order of 140°C and the low reactivation authorization threshold (Saut_B) is of the order of 100°C.

8. Method according to any one of claims 1 to 7, characterized in that the low deactivation threshold (Sdes_B) and the high deactivation threshold (Sdes_H) depend on at least one parameter of the motor vehicle, such as speed or acceleration, and / or at least one external parameter, such as an external temperature.

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

10. Motor vehicle comprising a computer defined according to the preceding claim.

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