METHOD FOR MANAGING A STARTING MOMENT OF A HEAT ENGINE IN A HYBRID VEHICLE

Abstract

The invention relates to a method for controlling a start of a thermal engine in a hybrid vehicle, the hybrid vehicle comprising a powertrain 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 duration.

Description

Title of the invention: METHOD FOR MANAGING A STARTING MOMENT OF A HEAT ENGINE IN A HYBRID VEHICLE

[0001] The present invention relates to a method for managing a starting time of a thermal engine in a hybrid vehicle.

[0002] On a hybrid vehicle, the management of the starts / stops of the thermal engine is based on the optimization of the vehicle's consumption. To do this, depending on the vehicle speed and the current state of charge of the electrical energy storage battery, it is possible to decide to start or stop the thermal engine to be as efficient as possible under normal conditions of use. Thus, in practice, the management of the starts and stops of the thermal engine is not decided by the driver of the vehicle.

[0003] When the vehicle is stationary (zero speed), most of the time energy optimization will aim to request the stopping of the thermal engine.

[0004] On the other hand, for other needs (e.g. need for passenger compartment heating or air conditioning), it may be necessary to start the thermal engine at any time. The starting of the thermal engine can also be triggered by a battery charge state which falls below a threshold.

[0005] We are particularly interested in the case where the thermal engine must be restarted while the vehicle speed is zero and the driver has put the gear lever in N ('Neutral', i.e. neutral of the gearbox). Here, "zero speed" should be understood to mean a strictly zero speed or a quasi-zero speed, e.g. 1 or 2 Km / h.

[0006] When the gearbox oil temperature is too low, the internal friction of the gearbox in Neutral can cause, when restarting the thermal engine, a small movement of the vehicle, a movement felt as untimely by the driver who may be surprised, which can 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 thermal engine at zero vehicle speed and lever on 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 a start of a thermal engine in a hybrid vehicle, the hybrid vehicle comprising a drive train with at least one electric machine capable of delivering a torque to the 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 lower than a first speed threshold, - the gear lever moves to the neutral position and remains there for at least a predefined period.

[0009] Thanks to the provisions promoted above, a possible occurrence of a thermal engine starting while 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 experienced as untimely by the driver.

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

[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 increased and reached values within a prescribed range, it is no longer useful to take the precaution set out above. The management of the starts and stops of the thermal engine can become conventional again, without any link to the position of the lever on Neutral.

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

[0014] By which means, the viscosity of the gearbox oil can be taken into account, which can be different from one type of gearbox to another. Below the predefined threshold, the viscosity is sufficient to create a frictional phenomenon which can induce an unwanted movement of the vehicle when starting the thermal engine while the lever is in N. Conversely, above the threshold, the oil is more fluid and the viscosity is insufficient to generate the unwanted movement of the vehicle mentioned above.

[0015] According to one embodiment, the first speed threshold is calibratable and is between 1 km / h and 3.5 km / h. It is thus possible to adjust, after customer tests, the threshold for taking zero speed into account.

[0016] According to one embodiment, the predefined duration is calibratable and is between 400 ms and 1000 ms. This duration makes it possible not to react to a relatively fleeting change to position N when the driver changes from R to d or changes from D to R. It is therefore necessary for position N to be established in a stable manner to give rise to the strategy presented above. above. The duration threshold can be adjusted after customer trials.

[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 request to keep the heat engine in operation.

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

[0019] The invention further relates to a hybrid motor vehicle comprising a powertrain with at least one thermal 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 previously.

[0020] According to one embodiment, the gearbox is of the double clutch type. In this configuration, the two half-gearbox clutches, even when open, together have a 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 set out above is contained in the computer which also manages all the other functions of the engine. This forms an optimized overall solution.

[0022] The invention will be further detailed by the description of non-limiting embodiments, and on the basis of the appended figures illustrating variants of the invention, in which: [Fig.l] 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 method implemented according to the present invention.

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

[0024] In [Fig.l], a functional diagram of the CT traction chain implemented in a hybrid vehicle is shown.

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

[0026] In the example shown, the hybrid powertrain drives the front axle. Of course, the hybrid powertrain could drive the rear axle. It is also 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 CT powertrain comprises an internal combustion engine called MOT and marked 4, an electric machine called ME and marked 8 and a gearbox called BV and marked 1.

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

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

[0030] The thermal engine MOT is started by selective activation of a starter called BS and marked 5 as known per se.

[0031] The BV gearbox is a mechanical double-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 ratios, eg 1, 3, 5 and 7. The second half-gearbox 42 carries the even ratios, eg 2, 4 and 6.

[0033] The first clutch K1 and the second clutch K2 are arranged coaxially in the gearbox, although symbolically represented on two separate axes in [Fig.l] for clarity of the description.

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

[0035] The electric machine ME is capable of delivering torque to the wheels via the gearbox BV, sufficient to provide a so-called "zero emission" mode of vehicle movement, namely with the thermal engine stopped. A battery with a capacity of a few kilowatt hours coupled to the electric machine ME makes it possible for the vehicle to carry out maneuvers at low speed, for example all maneuvers at speeds below 15 km / h. During these maneuvers, as far as possible, the thermal engine remains stopped.

[0036] When in operation, the thermal engine MOT is able to deliver torque to the wheels via the main clutch KO and the gearbox BV.

[0037] When the heat engine is running and has 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 comprises on its primary shaft AP a gear coupled to the electric motor, via a reduction stage where appropriate. In the example illustrated here, the coupling between the electric machine ME and the primary shaft AP is permanent.

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

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

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

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

[0043] The gearbox comprises a control lever, as known per se, with the positions P, R, N, D. The position of interest here is the neutral position N corresponding to the neutral point. Unlike the position P which involves a mechanical blocking of the gearbox via a blocking finger, in the position N, the gearbox is not blocked, it is free, apart from viscous friction.

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

[0045] The gearbox BV comprises an oil temperature sensor marked 2. This sensor 2 delivers 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 CTN.

[0046] Turning to [Fig.2], the method provides for starting 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 starting of the thermal engine (step noted 84).

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

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

[0050] The predefined duration TN is calibratable. 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 request to keep the heat engine in operation.

Claims

Claims

1. Method for controlling a start of a thermal engine (MOT) in a hybrid vehicle, the hybrid vehicle comprising a powertrain with at least one electric machine (ME) capable of delivering torque to the wheels via at least one gearbox (BV), and a thermal engine capable of delivering torque to the wheels via said gearbox, characterized in that the method provides for starting the thermal engine under the following cumulative forcing conditions: - the temperature of the transmission oil is lower than a predefined temperature threshold (TS) - the vehicle has an instantaneous speed (VitVeh) lower than a first speed threshold (VS), - the gear lever moves to the neutral position (N) and remains there for at least a predefined duration (TN).

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

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

4. Method according to one of claims 1 to 3, characterized in that the predefined duration is calibratable, and is between 400 ms and 1000 ms.

5. Method according to 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 request to keep the heat engine in operation.

6. Hybrid motor vehicle comprising a powertrain (CT) with at least one thermal 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 one of claims 1 to 5.

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

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

Images