MOTOR VEHICLE RECONFIGURING ITS POWERTRAIN ASSEMBLIES, ALLOWING MOVEMENT BY THE REAR ENGINE IN CASE OF OVERHEATING AT THE FRONT, PROCESS AND PROGRAMMING BASED ON SUCH A VEHICLE

Abstract

The invention relates to a motor vehicle comprising front and rear powertrains, which include: - an internal combustion engine (ICE); - a coupling device (CP); - a first clutch (K0); - a front electric motor (EM); - a front gearbox (GB); - a rear electric motor; - a reduction gear or a rear gearbox; - a dog clutch system; - at least one controller (eVCU) that determines whether the oil temperature of the front gearbox (GB) exceeds a temperature threshold for a specified duration; if so, it closes the dog clutch system; opens the first clutch (K0); and shifts the front gearbox (GB) into neutral. The invention also relates to a method and a program based on such a vehicle. Figure 2

Description

Title of the invention: AUTOMOBILE RECONFIGURING ITS POWERTRAIN ASSEMBLIES, ALLOWING MOVEMENT BY THE REAR POWERTRAIN IN CASE OF OVERHEATING AT THE FRONT, METHOD AND PROGRAM BASED ON SUCH A VEHICLE

[0001] The invention relates to the field of overheating monitoring of automatic or automated gearboxes, in particular for gearbox oil overheating of four-wheel drive hybrid vehicles.

[0002] Document WO2012153198 A2 describes a method for thermally protecting a gearbox to prevent a critical temperature rise during a creeping phase of a motor vehicle. This method consists of measuring the lubricating oil temperature inside the gearbox casing and warning the driver so that they can modify their driving, either by steering the vehicle or by placing the gear lever in neutral. However, the protective measures are entirely dependent on the driver's behavior, and although warning lights or messages are transmitted, it is common for the driver to make little or no change in their driving, which puts the gearbox at risk.

[0003] Currently, in the applicant's hybrid vehicles, when the powertrain supervisor detects overheating of the transmission oil (automatic or automated manual) on a two-wheel-drive hybrid vehicle, said supervisor performs the following operations: - it inhibits the operation of the electrical machine beforehand; - it shuts off the internal combustion engine; - it forces the gearbox to shift into neutral; and - it requests the "STOP" light to illuminate on the dashboard, to warn the driver of a serious fault and the prohibition of using the vehicle, as long as the fault persists.

[0004] Thus, users find themselves immobilized on the side of the road. This is disadvantageous with regard to user safety.

[0005] One objective of the present invention is to remedy the defects of the prior art, and in particular to propose a solution to improve user safety in the event of overheating of the automatic or automated gearbox oil, preventing the vehicle from being immobilized.

[0006] To achieve this objective, the invention proposes a motor vehicle in a frame of reference in space comprising a front-to-rear axis along a direction of movement of the motor vehicle, the motor vehicle comprising a front powertrain on a front axle with reference to the front-to-rear axis, which includes: - a heat engine; - a coupling device connected to the internal combustion engine; - a first clutch connected to the coupling device; - a front electric machine connected to the first clutch; - a front gearbox connected to the first clutch, the front gearbox being coupled to the front axle; the motor vehicle further comprising a rear powertrain on a rear axle with reference to the front-rear axis, which includes: - a rear electric machine; - a reduction gear or a rear gearbox connected to the rear electric machine, the reduction gear or rear gearbox being coupled to the rear axle; - a dog clutch system connecting the rear powertrain to the rear axle, the motor vehicle further comprising at least one controller controlling the internal combustion engine, the first clutch, the front electric machine, and the front gearbox, the rear electric machine, the reducer or the rear gearbox, the dog clutch system, characterized in that the front gearbox includes a temperature sensor connected to said controller, and said controller determines whether the temperature of the oil in the front gearbox is above a temperature threshold for a duration threshold; If so, said controller controls the closing of the dog clutch system to allow propulsion by the rear axle; opens the first clutch; puts the front gearbox in neutral; and preferably deactivates the internal combustion engine.

[0007] Advantageously, the invention proposes a reconfiguration of the front and rear powertrains in the event of overheating of the oil in the front gearbox, allowing the vehicle to be moved and thus preserving the safety of the users.

[0008] Preferably, the temperature threshold is between 90 and 160°C, preferably between 100 and 150°C; and the duration threshold is between 400 and 600 ms, and is preferably 500 ms.

[0009] This helps to limit damage to the front powertrain as much as possible.

[0010] Preferably, if the temperature of the front gearbox oil is above said temperature threshold during said time threshold, said controller limits the electrical power drawn by the rear electric machine to a limit power level.

[0011] This allows the vehicle to be put into limp mode.

[0012] Preferably, the limit power level is between 10 and 30 kW, and is preferably 20 kW.

[0013] This allows for optimal speed during degraded mode.

[0014] Preferably, said controller includes means for limiting the speed of the vehicle, and if the temperature of the oil in the front gearbox is above said temperature threshold during said time threshold, said controller limits the speed of the vehicle.

[0015] This allows a vehicle speed compatible with the degraded mode.

[0016] Preferably, said speed limiting means limit the speed of the vehicle to less than 125 km / h; preferably to less than 120 km / h.

[0017] This allows sufficient speed for normal movement.

[0018] The invention further relates to a method for controlling a vehicle according to the invention, comprising the following steps: - determine if the temperature of the front gearbox oil is above a temperature threshold for a duration threshold; - if yes, control the closing of the dog clutch system to allow propulsion by the rear axle; open the first clutch; put the front gearbox in neutral; and preferably deactivate the internal combustion engine.

[0019] Preferably, the method further includes, if the temperature of the front gearbox oil is above said temperature threshold during said time threshold, a step in which the electrical power taken by the rear electric machine is limited to a limit power level.

[0020] Preferably, the method further includes, if the temperature of the front gearbox oil is above said temperature threshold during said time threshold, a step in which the speed of the vehicle is limited.

[0021] Another object of the invention relates to a computer program comprising program code instructions for executing the steps of the control method according to the invention, when said program is running on a computer.

[0022] The invention will be further detailed by describing non-limiting embodiments, and based on the accompanying figures in which: - [Fig.l] schematically illustrates a front and rear powertrain architecture of a vehicle according to a preferred embodiment of the invention; - [Fig.2] schematically illustrates a detail of the architecture of the front powertrain of the vehicle in [Fig.1].

[0023] The invention proposes a solution for reconfiguring four-wheel drive vehicles in degraded mode to preserve user safety without immobilizing them.

[0024] In hybrid vehicles, there are various control units that manage the proper functioning of the powertrain. They are shown below.

[0025] A computer for the on-board charger / DC converter, which manages: - the operations of recharging the power of the low-voltage traction battery using alternating current or direct current (charger section); and - the 12V battery charging operation (converter part).

[0026] A traction battery control unit, which manages the operation of the traction chain's BT power battery. Depending on the manufacturer, it may be called a BMS (for "battery management system").

[0027] A front ME electric machine control unit that manages the operation of the front ME electric machine of the front powertrain. Depending on the manufacturer, it may be called MCUF (reference MCU).

[0028] A rear MP electric machine control unit that manages the operation of the rear MP electric machine of the rear powertrain. Depending on the manufacturer, it may be called MCUR (reference MCR);

[0029] A front MT internal combustion engine control unit that manages the operation of the MT internal combustion engine of the front powertrain.

[0030] A computer that supervises the proper functioning of all these computers and coordinates the actions of all these computers is also called the powertrain supervisor. Depending on the manufacturer, it may be called an eVCU.

[0031] One or more controllers / computers can be envisaged controlling one or more of the above elements in a different arrangement.

[0032] The mechanical architecture of the MHEV powertrain at the front of the vehicle is illustrated in [Fig.2].

[0033] This mechanical architecture consists of: - of an MT internal combustion engine; - connected to a CP coupling means to filter the acyclicities of the MT internal combustion engine in order to reduce gearbox noises (shotping) and the humming inside the vehicle which originates from the engine acyclicity transmitted to the wheels of the vehicle; - the coupling means is itself connected to a clutch (here named KO), where when the KO clutch is open, it allows the MT thermal engine to be isolated when the eVCU supervisor decides that the optimum is to drive in pure electric mode (or that the user requests driving in pure electric mode) without having to combat the friction torque of the MT thermal engine.

[0034] The KO clutch also allows the MT internal combustion engine to be started with a starter or an alternator-starter.

[0035] When the vehicle is running in hybrid or pure thermal mode, the KO clutch is closed.

[0036] After this KO clutch is the ME electric machine which can be connected to the gearbox input via a chain (alternatively this electric motor can be connected to the gearbox input via a chain drive or a belt).

[0037] This electric machine ME is powerful enough to drive the vehicle in pure electric traction and it also allows the BT traction battery and / or the service battery to be recharged. This electric machine ME can operate as an electric motor during vehicle traction phases and as an alternator during vehicle deceleration phases and / or during battery charging phases.

[0038] Next comes the gearbox BV which can be a dual clutch gearbox (DCT BV) or a pilot-operated gearbox or an automatic gearbox.

[0039] The illustration shows a dual-clutch transmission (with a second clutch K1 and a third clutch K2), but if the transmission is a simple automated manual transmission or an automatic transmission, it will only have one clutch between the gearbox teeth and the electric motor. There may even be no clutch between the rear electric motor and the gearbox teeth.

[0040] Next, as conventionally, come the transverse transmissions connected to the differential which drive the front wheels (front axle RA) of the vehicle.

[0041] Regarding the architecture of the rear powertrain (four-wheel drive vehicle), it consists of a rear electric machine MP, a reduction gear or gearbox BP and a dog clutch system CR of the rear powertrain to the rear running gear RP.

[0042] The CR rear dog clutch system is very important because it prevents the rear powertrain from rotating when the vehicle is operating in two-wheel drive mode, thus reducing vehicle friction losses and saving energy for vehicle traction.

[0043] Regarding the invention, the strategy developed is as follows:

[0044] One of the controllers performs a detection of gearbox oil overheating. The detection phase is conventional; the innovation lies in the reconfiguration mode.

[0045] A temperature sensor is located in the front gearbox BV to measure the temperature of the gearbox oil (DCT, piloted or automatic).

[0046] This sensor sends the temperature to the gearbox control unit before the gearbox (or alternatively, this temperature information can also be sent to the eVCU powertrain supervisor).

[0047] If the front gearbox control unit or the eVCU supervisor detects that this measured temperature exceeds a temperature threshold denoted STemp for a duration exceeding a duration threshold denoted DI: - either the front gearbox computer informs the supervisor of the detection of the problem, so that the supervisor triggers the new reconfiguration mode; - either the supervisor does the detection himself and triggers the new reconfiguration mode.

[0048] STemp is the calibrable gearbox oil overheating temperature threshold during function development. It can be calibrated between 100°C and 150°C.

[0049] DI is the calibratable time threshold during function development. It can be calibrated to around 500 milliseconds.

[0050] The new function for reconfiguring the two powertrains is as follows. The eVCU supervisor initiates the following actions: - it asks the rear electric machine's computer to start the rear electric motor MP; - it controls the engagement of the CR rear dog clutch system, to force the rear dog clutch to close, so that the rear axle propels the vehicle; - it opens the KO clutch so that the front MT internal combustion engine no longer drives the front gearbox (alternatively it can request the shutdown of the front MT internal combustion engine of the vehicle); - it puts the front gearbox BV in neutral so that the gearbox BV does not transmit torque from the front electric machine ME to the front wheels RA, nor torque from the front internal combustion engine MT to the front wheels RA, nor does the gearbox BV transmit torque from the vehicle's wheels RA to the front electric machine ME or from the wheels RA to the front internal combustion engine MT; - it limits the electrical power taken by the rear electric machine MP to an energy level (limit power "Plim") to reduce the vehicle's performance because the vehicle is in a degraded mode; - it calls on the "vehicle speed lock" function (noted BVV) which prevents the vehicle from exceeding a "Vmax" speed because the vehicle is in a degraded mode; - it requests the "service" light to be illuminated on the dashboard, to warn the driver of a detected problem that needs to be diagnosed by the maintenance service; - it also requests that a message be displayed on the dashboard indicating that the vehicle's maximum speed is limited following the detection of a problem, to prevent the driver that it is normal if he can no longer exceed a certain vehicle speed.

[0051] Alternatively, a fault code can be stored in the memory of one of the vehicle's computers to help the maintenance service identify that the problem stems from a loss of communication between the gearbox computer and the eVCU supervisor.

[0052] Plim is calibrable in the eVCU supervisor during the development of this new function, this maximum electrical power is calibrated around 20kW (but this value depends on the vehicle, being calibrated according to the mass characteristics and coefficient of penetration in the air of the vehicle and the characteristics of the tires of the vehicle in question), the purpose of this power limitation is to prevent the vehicle from driving too fast in degraded mode (the speed of the vehicle must be less than a speed Vlim that the electric rear axle can accept (130Kmh in our case)).

[0053] Thus, "Vmax" can be calibrated in the eVCU supervisor during the development of this new function, at 120 km / h in our case.

[0054] Regarding the return to normal, if the gearbox oil temperature falls below a new temperature threshold, which will be called SRTemp (for recovery temperature threshold), the supervisor restores the normal operation of the vehicle.

[0055] On the other hand, the fault code stored in one of the vehicle's computers remains stored in the memory of one of the vehicle's computers (Depending on the manufacturer, the memory used may be the memory of the intelligent servicing box noted BSI, but any other computer memory may be used), so that during vehicle servicing, the maintenance service can see the occasional fault, in order to decide with the user whether the maintenance service will check the sensor, the gearbox or the gearbox cooling system or not.

[0056] SRTemp denotes the temperature threshold for restoring the gearbox oil temperature. It can be calibrated during the function development phase. With SRTemp necessarily lower than STemp and calibrated at least 10°C below the value of STemp, for example, it can be set between 80°C and 110°C.

[0057] The invention further relates to a method and a program for implementing the control described above. The program can be loaded into the memory of one or more controllers to implement the invention.

Claims

1. Demands A motor vehicle in a frame of reference in space comprising a front-to-rear axis (X) along a direction of movement of the motor vehicle, the motor vehicle comprising a front powertrain on a front axle (RA) with reference to the front-to-rear axis (X), which includes: - a thermal engine (MT); - a coupling device (CP) connected to the internal combustion engine (MT); - a first clutch (KO) connected to the coupling device (CP); - a front electric machine (ME) connected to the first clutch (KO); - a front gearbox (BV) connected to the first clutch (KO), the front gearbox (BV) being coupled to the front axle (RA); the motor vehicle further comprising a rear powertrain on a rear axle (RP) with reference to the front-rear axis (X), which includes: - a rear electric machine (MP); - a rear reducer or gearbox (BP) connected to the rear electric machine (MP), the rear reducer or gearbox (BP) being coupled to the rear axle (RP); - a dog clutch system (CR) connecting the rear powertrain to the rear axle (RP), the motor vehicle further comprising at least one controller (eVCU) controlling the internal combustion engine (MT), the first clutch (KO), the front electric machine (ME), and the front gearbox (BV), the rear electric machine (MP), the reduction gear or the rear gearbox (BP), the dog clutch system (CR), characterized in that the front gearbox (BV) comprises a temperature sensor connected to said controller (eVCU), and said controller (eVCU) determines whether the temperature of the oil in the front gearbox (BV) is above a temperature threshold for a duration threshold; If so, said controller (eVCU) controls the closure of the dog clutch (CR) system to allow propulsion by the rear axle (RP); opens the first clutch (KO); puts the front gearbox (BV) in neutral; and preferably deactivates the internal combustion engine (MT).

2. Motor vehicle according to claim 1, characterized in that the temperature threshold is between 90 and 160°C, preferably between 100 and 150°C; and the time threshold is between 400 and 600 ms, and is preferably 500 ms.

3. Motor vehicle according to any one of claims 1 to 2, characterized in that if the temperature of the front gearbox (BV) oil is above said temperature threshold during said time threshold, said controller (eVCU) limits the electrical power taken by the rear electric machine (MP) to a limit power level.

4. Motor vehicle according to claim 3, characterized in that the power limit level is between 10 and 30 kW, and is preferably 20 kW.

5. Motor vehicle according to any one of claims 1 to 4, wherein said controller (eVCU) includes means for limiting the speed of the vehicle, characterized in that if the temperature of the oil in the front gearbox (BV) is above said temperature threshold for said duration threshold, said controller (eVCU) limits the speed of the vehicle.

6. Motor vehicle according to claim 5, characterized in that said speed limiting means limit the speed of the vehicle to less than 125 km / h; preferably to less than 120 km / h.

7. A method for checking a vehicle according to any one of claims 1 to 6, comprising the following steps: - determining whether the temperature of the oil in the front gearbox (BV) is above a temperature threshold for a duration threshold; - if so, controlling the closure of the dog clutch system (CR) to allow rear axle propulsion (RP); opening the first clutch; putting the front gearbox (BV) into neutral, and preferably disabling the internal combustion engine (MT).

8. A control method according to claim 7, further comprising, if the temperature of the front gearbox (BV) oil is above said temperature threshold during said time threshold, a step in which the electrical power taken by the rear electric machine (MP) is limited to a limit power level.

9. A control method according to any one of claims 7 to 8, further comprising, if the temperature of the front gearbox (BV) oil is above said temperature threshold during said time threshold, a step in which the speed of the vehicle is limited.

10. Computer program comprising program code instructions for performing the steps of the control process according to any one of claims 7 to 9, when said program is running on a computer.

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