METHOD FOR MANAGING A START-UP MOMENT OF AN INTERNAL COMBUSTION ENGINE IN A HYBRID VEHICLE

Abstract

The invention relates to a method for controlling the start of a thermal engine in a hybrid vehicle, the hybrid vehicle comprising a drivetrain with at least one electric machine capable of delivering torque to the wheels via at least one gearbox, and a thermal engine capable of delivering torque to the wheels via said gearbox, the method providing for starting the thermal engine under the following cumulative forcing conditions: - the temperature of the transmission oil is below a predefined temperature threshold (TS) - the vehicle has an instantaneous speed (VitVeh) below a first speed threshold (VS), - the gear lever moves to the neutral position (N) and remains there for at least a predefined time.

Description

Title of the invention: METHOD FOR MANAGING THE START-UP MOMENT OF AN INTERNAL COMBUSTION ENGINE IN A HYBRID VEHICLE

[0001] The present invention relates to a method for managing a start-up moment of a thermal engine in a hybrid vehicle.

[0002] In a hybrid vehicle, the management of the start / stop of the internal combustion engine is based on optimizing vehicle fuel consumption. To achieve this, depending on the vehicle speed and the current state of charge of the electrical energy storage battery, it is possible to decide whether to start or stop the internal combustion engine to be as efficient as possible under normal operating conditions. Thus, in practice, the management of the start and stop of the internal combustion engine is not decided by the vehicle driver.

[0003] When the vehicle is at a standstill (zero speed), most of the time energy optimization will aim to request the shutdown of the internal combustion engine.

[0004] However, for other needs (e.g., the need for cabin heating or air conditioning), it may be necessary to start the internal combustion engine at any time. The starting of the internal combustion engine may also be triggered by a battery charge level falling below a certain threshold.

[0005] We are particularly interested in the scenario where the internal combustion engine must be restarted when the vehicle's speed is zero and the driver has placed the gear lever in N ('Neutral', i.e., the neutral position of the gearbox). Here, 'zero speed' should be understood as a speed that is strictly zero or almost zero, e.g., 1 or 2 km / h.

[0006] When the gearbox oil temperature is too low, internal friction in the gearbox in Neutral can cause, when restarting the internal combustion engine, a small movement of the vehicle, a movement felt as untimely by the driver who may be surprised, which may contribute to a feeling of insecurity.

[0007] The inventors sought to reduce the impression of surprise that can be produced by the consequences of starting the internal combustion engine at zero vehicle speed and lever in N, when the oil present in the gearbox has not yet reached a nominal operating temperature range.

[0008] To this end, the present invention proposes a method for controlling the starting of a thermal engine in a hybrid vehicle, the hybrid vehicle comprising a drivetrain with at least one electric machine capable of delivering torque to wheels via at least one gearbox, and a heat engine capable of delivering torque to the wheels via said gearbox, characterized in that the method provides for starting the heat engine under the following cumulative forcing conditions: - the transmission oil temperature is below a predefined temperature threshold, - the vehicle has an instantaneous speed below a first speed threshold, - the gear lever moves to the neutral position and remains there for at least a predefined time.

[0009] Thanks to the provisions promoted above, a possible occurrence of a start of the internal combustion engine occurring when the driver has put the lever in neutral and is not pressing the brake pedal is advantageously eliminated, a circumstance which, when the gearbox oil is cold, can cause a small movement perceived as untimely by the driver.

[0010] This improves, from the driver's point of view, the predictability of the vehicle's operation and behavior.

[0011] It is noted that the proposed method is independent of whether or not the driver presses the brake pedal.

[0012] It should also be noted that when the oil temperature in the gearbox has risen and reached values ​​within a prescribed range, it is no longer necessary to take the precaution described above. The management of the starting and stopping of the internal combustion engine can revert to conventional operation, independent of the lever's position in Neutral.

[0013] According to one embodiment, the predefined temperature threshold is calibrable, it is between 45°C and 60°C.

[0014] Accordingly, the viscosity of the gearbox oil can be taken into account, as it can vary from one type of gearbox to another. Below the predefined threshold, the viscosity is sufficient to create a frictional phenomenon that can induce unwanted vehicle movement when starting the internal combustion engine with the lever in neutral. Conversely, above the threshold, the oil is more fluid and the viscosity is insufficient to generate the aforementioned unwanted vehicle movement.

[0015] According to one embodiment, the first speed threshold is calibrable and is between 1 km / h and 3.5 km / h. The threshold for taking zero speed into account can thus be adjusted after customer testing.

[0016] According to one embodiment, the predefined duration is calibrable and ranges from 400 ms to 1000 ms. This duration allows the system to avoid reacting to a relatively fleeting transition over position N when the driver moves from R to d or from D to R. Therefore, position N must be established stably to enable the strategy described below. above. The duration threshold can be adjusted after customer testing.

[0017] According to one embodiment, when the heat engine has been started in response to the cumulative forcing conditions, the method provides, in a condition where the gear lever leaves the neutral position, not to maintain a forcing of operation of the heat engine and to stop the heat engine if there is no functional demand to keep the heat engine running.

[0018] Thus, if the driver leaves the N position of the lever, then the constraint of the forced start disappears, and if there is no other reason to keep the internal combustion engine running, then the internal combustion engine is stopped at the moment when the driver has left the N position.

[0019] The invention further relates to a hybrid motor vehicle comprising a drivetrain with at least one internal combustion engine, at least one electric machine, capable of delivering torque to the wheels via a gearbox, and at least one control unit configured to implement the method as described above.

[0020] According to one embodiment, the gearbox is of the dual-clutch type. In this configuration, the two half-gearbox clutches, even when open, together exhibit frictional drag when the gearbox oil is cold.

[0021] According to one embodiment, the control unit is the engine management computer. The forced start strategy described above is contained within the computer, which also manages all other engine functions. This forms an optimized overall solution.

[0022] The invention will be further detailed by describing non-limiting embodiments, and based on the accompanying figures illustrating variants of the invention, in which: [Fig.1] is a functional schematic representation of the system in which the present invention is implemented; [Fig.2] shows an example of a functional flowchart relating to the process implemented according to the present invention.

[0023] In the different figures, the same references designate identical or similar elements.

[0024] Figure [1] shows a functional diagram of the CT traction chain implemented in a hybrid vehicle.

[0025] The hybrid vehicle in which the powertrain is installed can be a sedan, pickup truck, coupe, van, truck, coach, etc.; there is no limitation on the type of vehicle. The vehicle can be 4x4 or 4x2.

[0026] In the illustrated example, the hybrid drivetrain powers the front axle. Of course, the hybrid drivetrain could also power the rear axle. It is also It is possible to have the traction chain promoted here coupled to one of the trains and a second electric machine coupled to the other of the trains.

[0027] The traction chain CT includes an internal combustion engine called MOT and identified as 4, an electric machine called ME and identified as 8 and a gearbox called BV and identified as 1.

[0028] The heat engine is also called an internal combustion engine.

[0029] The MOT internal combustion engine is coupled to the gearbox by means of a main clutch marked KO, which selectively couples the AM drive shaft to the AP gearbox primary shaft.

[0030] The MOT internal combustion engine is started by selective activation of a starter called BS and identified as known in itself.

[0031] The BV gearbox is a mechanical dual-clutch type, the gearbox control is robotized.

[0032] As known per se, the gearbox comprises a first clutch K1 serving a first half-gearbox 41 and a second clutch K2 serving a second half-gearbox 42. According to the example given here, the first half-gearbox 41 carries the odd-numbered gears, e.g. 1, 3, 5 and 7. The second half-gearbox 42 carries the even-numbered gears, e.g. 2, 4 and 6.

[0033] The first clutch Kl and the second clutch K2 are arranged coaxially in the gearbox, although symbolically represented on two separate axes in [Fig.l] for clarity of exposition.

[0034] The output shaft 56 of the gearbox BV is connected to the wheels of the relevant axle via a differential 57 and a wheel shaft 58, as known per se and therefore not described in detail. It should be noted that only one wheel 59 is shown in [Fig. 1].

[0035] The electric motor ME is capable of delivering torque to the wheels via the gearbox BV, sufficient to provide a "zero-emission" mode of vehicle operation, i.e., with the internal combustion engine off. A battery with a capacity of a few kilowatt-hours coupled to the electric motor ME enables the vehicle to perform low-speed maneuvers, for example, all maneuvers at speeds below 15 km / h. During these maneuvers, the internal combustion engine remains off whenever possible.

[0036] When in operation, the MOT internal combustion engine is capable of delivering torque to the wheels via the main clutch KO and the gearbox BV.

[0037] When the internal combustion engine is running and needs to provide traction power to the wheels, the main clutch KO is closed, and one of the clutches (Kl or K2) of the gearbox is also closed.

[0038] The gearbox BV includes on its primary shaft AP a gear coupled to the electric motor, optionally via a reduction stage. In the example illustrated here, the The coupling between the electric machine ME and the primary shaft AP is permanent.

[0039] The system includes at least one control unit 7. The control unit 7 includes a microcontroller 17.

[0040] In the illustrated example, the control unit in question corresponds to the engine management computer.

[0041] However, the control unit 7 could be another on-board computer other than the engine management computer.

[0042] The control unit 7 receives a vehicle speed information called VitVeh. In the illustrated example, the vehicle speed information VitVeh is received from the braking control unit 6, via the multiplexed network, e.g. CAN.

[0043] The gearbox includes a control lever, as known per se, with positions P, R, N, and D. The position of interest here is the neutral position N, corresponding to neutral. Unlike the P position, which involves a mechanical locking of the gearbox via a locking finger, in the N position, the gearbox is not locked; it is free, except for viscous friction.

[0044] The control lever may be electromechanical. A device 3 is provided to determine the current position of the lever. For example, Hall effect sensors may be provided to detect each of the P, R, N, D positions of the lever.

[0045] The gearbox BV includes an oil temperature sensor designated 2. This sensor 2 delivers an oil temperature information to the control unit 7. For example, the sensitive portion of the sensor 2 can be formed by a variable resistor with a negative coefficient called an NTC.

[0046] Turning to [Fig.2], the process plans to start the heat engine under the following cumulative forcing conditions: - the transmission oil temperature is below a predefined temperature threshold TS, represented by test 81 and its positive result ('yes'), - the vehicle has an instantaneous speed VitVeh lower than a first speed threshold VS, represented by test 82 and its positive result ('yes'), - the gear lever moves to the neutral position (N) and remains there for at least a predefined duration TN, represented by test 83 and its positive result ('yes').

[0047] If the three tests mentioned above are passed, then the control unit 7 triggers the start-up of the internal combustion engine (step noted 84).

[0048] The predefined temperature threshold TS is calibrable. For example, the predefined temperature threshold TS is between 45 °C and 60 °C.

[0049] The speed threshold VS is calibrable. For example, the speed threshold VS is between 1 km / h and 3.5 km / h.

[0050] The predefined duration TN is calibrable. For example, the predefined duration TN is between 400 ms (milliseconds) and 1000 ms (milliseconds).

[0051] Furthermore, the method provides that when the heat engine has been started in response to the cumulative forcing conditions, the method provides, in a condition where the gear lever leaves the neutral position, not to maintain a forcing of operation of the heat engine and to stop the heat engine if there is no functional demand to keep the heat engine running.

Claims

Demands

1. A method for controlling the start of a heat engine (HEI) in a hybrid vehicle, the hybrid vehicle comprising a drivetrain with at least one electric machine (EM) capable of delivering torque to the wheels via at least one gearbox (GV), and a heat engine capable of delivering torque to the wheels via said gearbox, characterized in that the method provides for starting the heat engine under the following cumulative forcing conditions: - the temperature of the transmission oil is below a predefined temperature threshold (TS) - the vehicle has an instantaneous speed (VitVeh) below a first speed threshold (VS), - the gear lever moves to the neutral position (N) and remains there for at least a predefined time (TN).

2. A method according to claim 1, characterized in that the predefined temperature threshold is calibrable, and is between 45°C and 60°C.

3. A method according to any one of claims 1 to 2, characterized in that the first speed threshold is calibrable, and is between 1 km / h and 3.5 km / h.

4. A method according to any one of claims 1 to 3, characterized in that the predefined duration is calibrable, and is between 400 ms and 1000 ms.

5. A method according to any one of claims 1 to 4, characterized in that when the heat engine has been started in response to the cumulative forcing conditions, the method provides, in a condition where the gear lever leaves the neutral position, not to maintain a forcing of operation of the heat engine and to stop the heat engine if there is no functional demand to keep the heat engine running.

6. Hybrid motor vehicle comprising a drivetrain (CT) with at least one internal combustion engine (MOT), at least one electric machine (ME), capable of delivering torque to the wheels via a gearbox (BV), and at least one control unit (10) configured to implement the method according to any one of claims 1 to 5.

7. Hybrid motor vehicle according to claim 6, characterized in that the gearbox (BV) is of the dual-clutch type.

8. Hybrid motor vehicle according to any one of claims 6 to 7, ca- characterized in that the control unit (10) is the engine management computer.

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