METHOD FOR MANAGING A STARTING SEQUENCE OF AN INTERNAL COMBUSTION ENGINE IN A HYBRID VEHICLE

Abstract

The invention relates to a method for managing a starting sequence of an internal combustion engine in a hybrid vehicle comprising a brake pedal (9), a start button (8), a crankshaft rotation speed sensor (71), the method comprising: - an activation of the start button (8) and the brake pedal, - a drive of the crankshaft by an electric machine, - a start of a time delay at the moment of release of the brake pedal, - if at the moment of release of the brake pedal, the crankshaft rotation speed is greater than a first speed threshold and less than a second speed threshold, then at the end of the time delay, if the crankshaft rotation speed has exceeded is still greater than the first threshold, then the starting sequence is confirmed and validated, otherwise the starting sequence is interrupted. Figure 2

Description

Title of the invention: METHOD FOR MANAGING A STARTING SEQUENCE OF AN INTERNAL COMBUSTION ENGINE IN A HYBRID VEHICLE

[0001] The invention relates to a method for managing a starting sequence of an internal combustion engine (also called a heat engine) in a mild hybrid vehicle (called "Mild Hybrid" according to a very widespread name of Anglo-Saxon origin).

[0002] We are interested here in hybrid vehicles in which mechanical power produced by an internal combustion engine can be delivered to the wheels simultaneously or independently of mechanical power delivered by an electric motor also delivered to the wheels via a transmission which combines thermal power and electrical power.

[0003] It is not excluded that the hybrid vehicle is of the rechargeable type ('Plugin').

[0004] In the example illustrated, the thermal and electrical powers are delivered on the same axle. However, it is not excluded to have the thermal power delivered on the front axle (front axle) and the electrical power delivered both on the front axle (front axle) and on the rear axle (rear axle).

[0005] A mild hybrid vehicle can drive in zero-emission mode for short distances, for example a few hundred meters or a few kilometers.

[0006] The internal combustion engine is controlled by a first electronic computer. Such a vehicle is equipped with at least one electric motor controlled by means of a second electronic computer via an inverter. A supervisor computer may be provided responsible for the general management functions of the powertrain. In this document, an electronic computer is also called a 'control unit'.

[0007] Furthermore, recent vehicles are equipped with a pulse start function, i.e. the driver briefly presses a button called "start" to trigger a starting sequence of the internal combustion engine. This pulse aspect is also available in versions with conventional ignition keys.

[0008] Hand in hand with the impulse engine start function is a check of the safety conditions of such an operation. Thus, drivers are asked to press the brake pedal to start the engine. In some versions with a manual gearbox, it may also be requested to have the gearbox in neutral or to fully depress the clutch pedal. In versions with an automatic gearbox, the gearbox selector must be in position P or N.

[0009] The brake pedal must be pressed throughout the sequence. Therefore, if the brake pedal is released while the engine is being started, then the engine is interrupted. And if the engine is declared to be running independently, then the start sequence is complete and releasing the brake pedal has no effect.

[0010] It turns out that the thermal engines of the powertrains used in mild hybridization declare themselves to be running autonomously at a higher speed than conventional thermal engines.

[0011] Consequently, it may happen that the driver thinks that the engine has started and releases the brake pedal when the engine speed expected for the end of the start sequence has not yet been reached.

[0012] It is this phenomenon, which is similar to an unjustified failure from the driver's point of view, that the inventors sought to minimize.

[0013] The inventors therefore proposed to eliminate the aforementioned defect.

[0014] To this end, the present invention proposes a method for managing a starting sequence (i.e. starting) of an internal combustion engine in a hybrid vehicle, the vehicle comprising at least one brake pedal with a brake pedal sensor, a starting member (e.g. 'start' push button or key) configured to be actuated by a user, at least one combustion engine control unit, a crankshaft rotation speed sensor, characterized in that the method comprises the following steps: - a step of activation of the starting device by a user of the vehicle - a step of verification of the safety conditions of a possible activation of the engine, including at least one condition of the brake pedal being pressed, - a step of activating a means of driving the crankshaft by an electric machine, - a recurring measurement of the crankshaft rotation speed, - a step of starting a time delay when the brake pedal is released, and the following conditional actions: (e 1)- if at the time of releasing the brake pedal, the crankshaft rotation speed is lower than a first speed threshold, then the starting sequence is interrupted, (e2)- if at the time of releasing the brake pedal, the crankshaft rotation speed is greater than a second speed threshold, then the start sequence is confirmed and validated, (e3)- if at the time of releasing the brake pedal, the crankshaft rotation speed is greater than the first speed threshold and less than the second speed threshold, so we wait for the end of the timeout, (fl)- if at the end of the time delay, the crankshaft rotation speed is still higher than the first speed threshold, then the start sequence is considered confirmed and validated, (f2)- if at the end of the time delay, the crankshaft rotation speed is lower than the first speed threshold, then the starting sequence is interrupted.

[0015] Thanks to the provisions promoted above, it is possible to let the start-up continue until the end, even if the brake pedal has been released just a little too early.

[0016] It is noted that the expression "the crankshaft rotation speed is always greater than the first speed threshold" covers the case where the crankshaft rotation speed has remained below the second threshold or has exceeded the second speed threshold at the end of the time delay.

[0017] If the crankshaft rotation speed has exceeded the second threshold, while the timer was running, then the start sequence is declared to have been successfully completed from that moment.

[0018] We note that the rotation speed of the crankshaft is expressed in revolutions per minute (here we use the equivalent unit Rpm 'Revolutions Per Minute').

[0019] According to one embodiment, the time delay can be between 100 ms and 400 ms, preferably between 150 ms and 250 ms.

[0020] This allows you to compensate for a release that is too early by a few hundred ms. This trick remains transparent to the driver.

[0021] The hybrid vehicle of interest here is a mild hybridization type hybrid vehicle (i.e. Mild Hybrid in the language of the trade), i.e. with a limited capacity for movement in zero-emission mode (i.e. thermal engine switched off).

[0022] According to one embodiment, the first threshold is a first parameter which can be between 800 revolutions per minute and 1200 revolutions per minute. Calibration work makes it possible to adjust this first threshold for a given powertrain.

[0023] According to one embodiment, the second threshold is a second parameter which can be between 1500 revolutions per minute and 2100 revolutions per minute. Here too, calibration work makes it possible to adjust this second threshold for a given powertrain.

[0024] According to one embodiment, the time delay and / or the first threshold and / or the second threshold are parameters which may depend on the temperature of the engine. For example, a longer time delay value may be used in the case of a start in very low temperature conditions, and the engine speed thresholds may also be adapted depending on the case of cold starts.

[0025] According to one embodiment, the time delay is a parameter which can depend on a state charging a vehicle traction battery. For example, if the battery is not very charged, a longer time delay can be chosen, as the rev-up curve may be a little slower.

[0026] According to one embodiment, a step of additional verifications may also be provided concerning a dual-clutch automatic gearbox including a step of verifying an electrical power supply to an oil pump and a verification of an electrical power supply to actuators.

[0027] The dual-clutch automatic gearbox is equipped with an oil pump electrically driven by an electric motor connected to the 12-volt network, and equipped with actuators electrically powered from the traction battery network (for example the 48-volt network).

[0028] The method provides that the starting sequence is subject to verification of the correct operation of the dual-clutch automatic gearbox; in other words, if the vehicle is unable to drive due to a fault in the gearbox, the thermal engine is not allowed to start.

[0029] According to one embodiment, the operation of the DC-DC converter and the correct operation of the 12 volt network are also checked. Generally speaking, extensive tests can be provided to authorize the operation of the thermal engine.

[0030] The invention further relates to a control system in a hybrid vehicle comprising an internal combustion engine and at least one electric motor, the control system comprising at least one first electronic computer responsible for controlling the internal combustion engine, and at least one second electronic computer responsible for controlling the electric motor, characterized in that the control system is configured to implement the method as described previously.

[0031] The invention further relates to a hybrid vehicle comprising an electric powertrain arranged on a front axle of the vehicle, comprising an internal combustion engine, at least one electric motor, and at least one control system as described previously.

[0032] The invention further relates to a hybrid vehicle, in particular of the mild hybridization type, comprising an electric powertrain, comprising an internal combustion engine arranged on a front axle of the vehicle, at least one electric motor arranged on a rear axle of the vehicle, and at least one control system as described previously.

[0033] 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] schematically illustrates a hybrid type powertrain in which the present invention can be implemented; [Fig.2] schematically illustrates a control system according to an example of the present invention; [Fig.3] schematically illustrates an example of a timing diagram of a starting sequence, with a substantially rapid and successful engine start; [Fig.4] is analogous to [Fig.3] and schematically illustrates another example of a timing diagram, in the case of a start sequence failing due to failure to reach the speed threshold prescribed for autonomous operation; [Fig.5] is analogous to [Fig.3] and schematically illustrates another example of a timing diagram, which shows the benefit of the timing proposed by the invention, with a slightly anticipated pedal release which does not prevent the success of the starting sequence; [Fig.6] is analogous to [Fig.3] and schematically illustrates another example of a timing diagram in the case of a failed start sequence [Fig.7] schematically illustrates an example of test logic occurring following release of the brake pedal.

[0034] In the various figures, the same references designate identical or similar elements. For reasons of clarity of the description, certain elements are not necessarily represented to scale.

[0035] A general diagram of a hybrid type powertrain is now described with reference to [Fig.l].

[0036] The vehicle in question can be a sedan, a pickup, a coupe, a van, etc., there is no limitation in the type of vehicle. The vehicle can be 4x4 or 4x2.

[0037] In the example illustrated, the hybrid powertrain drives the front axle. Of course, the hybrid powertrain could drive the rear axle. It is also possible to have the powertrain promoted here coupled to one of the axles and a second electric machine coupled to the other of the axles.

[0038] The CT powertrain comprises an internal combustion engine called ENG and marked 1, an electric machine called ME and marked 2 and a gearbox BV.

[0039] In addition, the CT drive train comprises an intermediate transmission interposed between the internal combustion engine 1 and the gearbox BV. The output shaft 56 of the gearbox BV is connected to the wheels of the train concerned via a differential 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].

[0040] The internal combustion engine 1 is controlled by a first electronic computer 3.

[0041] The electrical machine 2 is controlled by a control unit, here called the second control unit (also called the second computer) marked 4. The second control unit 4 controls the phases of the electric machine through an inverter 22. The electric machine 2 can act alternately as a motor or a generator. The electric machine 2 is controlled as a generator, particularly under regenerative braking conditions. The rest of the time, the electric machine is used as the main or auxiliary traction motor, and also to start the internal combustion engine 1, or not used in certain phases.

[0042] The intermediate transmission comprises a main clutch KO, the function of which is to selectively couple the output shaft of the engine with the primary transmission shaft 55. The primary shaft 55 is arranged downstream of the main clutch KO and forms the input shaft of the gearbox BV.

[0043] This main KO clutch is open when the internal combustion engine is stopped and the vehicle is driving in zero emission mode.

[0044] When the heat engine is running and needs to provide traction power to the wheels, then the main clutch KO is closed.

[0045] The intermediate transmission comprises on its primary shaft 55 a gear coupled to the electric motor, via where appropriate a reduction stage 54. In the example illustrated here, the coupling between the electric machine and the primary shaft is permanent.

[0046] In the example illustrated, the BV gearbox is of the mechanical type with double clutch, the control of the gearbox is robotized.

[0047] The gearbox comprises a first clutch K1 serving a first half-gearbox and a second clutch K2 serving a second half-gearbox. According to the example given here, the first half-gearbox carries the odd ratios, eg 1, 3, 5 and 7. The second half-gearbox carries the even ratios, eg 2, 4 and 6.

[0048] 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.

[0049] In the example illustrated, the gearbox is lubricated by an oil pump 47 driven by an electric motor. In such a case, the proper functioning of the motor driving the oil pump is part of the checks carried out prior to activation of the thermal engine.

[0050] In the same logic, the gearbox is actuated by electric actuators, e.g. fork movement cylinders, clutch control K1 and K2, the correct operation of this equipment is part of the checks carried out prior to activation of the thermal engine.

[0051] In the example illustrated, the alternator-starter 57 can supply electrical energy to the network NW1 with a nominal voltage of 48 Volts connected to a first battery 51. It is noted that the nominal voltage of the first network could be different from 48 volts. The 57 alternator-starter can also be used to start or restart the engine. thermal after driving in Zero Emission mode.

[0052] A DC / DC converter marked 5 is provided which supplies a second network NW2 with a nominal voltage of 12V connected to a second 52 (conventional 12 volt battery) as well as to a plurality of electrical equipment operating under 12Volts as known per se.

[0053] The first battery 51 may be of the Lithium-Ion type. The first battery 51 may be recharged independently of the alternator present on the vehicle, by connecting it to a means of recharging from a source external to the vehicle. This is the configuration known as a “plug-in hybrid”. The electrical energy stored in the first battery 51 is used by the electric machine.

[0054] In a hybrid powertrain, the traction transmitted to the wheels can come from the electric machine 2 and / or the internal combustion engine. In a zero-emission mode, the internal combustion engine 1 is stopped and traction is provided solely by the electric machine 2. In a so-called “boost” mode, the electric machine 2 and the thermal engine 1 are both used.

[0055] You are now interested in the starting sequence of the internal combustion engine 1.

[0056] For this purpose, there is provided, as visible in [Fig.2], a start button also called 'start engine' 8 (or simply 'start'). This start button can be generically called 'starting member'. Indeed, in an alternative embodiment (not shown in the figures), a conventional ignition key can be used to initiate the starting sequence.

[0057] The electrical contact present in the starting member is marked 81.

[0058] As known per se, the internal combustion engine is equipped with a flywheel with a toothed wheel 72 which rotates opposite a crankshaft position sensor 71.

[0059] The vehicle is equipped in a known manner with a brake pedal 9 with a brake pedal sensor 91. The contact used indicates that the brake pedal is substantially depressed.

[0060] As indicated in the introduction, the impulse start function involves a check of the safety conditions of such an operation and drivers are asked to press the brake pedal to start the engine. This ensures that it is indeed an adult who is in the driving position and also that the vehicle will not move during the starting sequence.

[0061] The brake pedal must be pressed throughout the sequence. Therefore, in principle, if the brake pedal is released while the engine is being started, then the engine is interrupted. And if the engine is declared to be running independently, then the start sequence is completed and a brake pedal release then has no effect.

[0062] According to the present invention, this general operation is modulated according to the use of a time delay which will now be described.

[0063] As illustrated in Figures 4 and 5, a time delay Tpp is started when the brake pedal 9 is released.

[0064] A thermal engine start sequence is started by pressing the start button provided that the brake is pressed at the time of the rising edge of the start button information.

[0065] With reference to figures 3 to 6, the time of pressing the brake pedal is marked t1 and the time of pressing the start button is marked t2.

[0066] The engine start sequence begins with safety checks, for example that the gearbox is in position P or N.

[0067] Other checks may be necessary, particularly concerning the 48 volt on-board network and the 12 volt on-board network.

[0068] At time t3, the crankshaft is driven by the electric motor being activated. The first control unit 3 receives the pulses from the so-called 'tooth signal' sensor marked 71 and calculates a rotation speed of the crankshaft as a function of the frequency of the pulses received.

[0069] The curve marked 14 represents the activation of the moving assembly and the evolution of the engine speed.

[0070] Two thresholds are defined for the crankshaft rotation speed: a first threshold noted SRI and a second threshold noted SR2.

[0071] It is at time t4 that the driver releases the brake pedal, according to various possibilities presented in figures 3 to 5.

[0072] Releasing the brake pedal corresponds to a falling edge of the brake pedal signal.

[0073] At this moment, at time t4, a three-branch test (e1,e2,e3) is carried out according to the logic presented below, and illustrated in [Fig.7].

[0074] el- if the crankshaft rotation speed is lower than the first SRI rpm threshold, then the starting sequence is interrupted, this is illustrated in [Fig.6]. SRI may not be reached due to a carburetion problem (air or gasoline) or an ignition problem.

[0075] e2- if the crankshaft rotation speed is greater than the second speed threshold SR2, then the start sequence is confirmed and validated, this is illustrated in [Fig.3]. In practice this is the case where the sequence ends positively before the brake pedal is released.

[0076] e3- if the crankshaft rotation speed is greater than the first speed threshold and lower than the second speed threshold, then we start the timing Tpp and we waits for the end of the time delay Tpp; in the meantime, the crankshaft drive continues. This is illustrated in Figures 4 and 5.

[0077] In [Fig.7], the cross-shaped pictogram indicates a failure, i.e. an interruption of the startup sequence, while a tick-shaped pictogram indicates success.

[0078] At the end of the time delay Tpp, and as illustrated in [Fig.7], a two-branch test (f 1 ,f2) is carried out according to the logic presented below.

[0079] fl- if the crankshaft rotation speed is greater than the first threshold SRI, then the starting sequence is confirmed and validated. This is illustrated in [Fig.5]. It is noted that the early release has no adverse effect on the end of the engine starting sequence, the driver does not have to undergo an unwanted stop of the starting procedure. Curve 14 illustrates a scenario where the engine speed has passed above the second speed threshold SR2, the starter activation command is interrupted immediately at time t5.

[0080] Curve 140 in dotted lines illustrates another scenario where the engine speed has remained above the first threshold SRI but has not reached the second speed threshold SR2. It is at the end of the time delay Tpp, at time t6, that the crankshaft drive control ceases.

[0081] f2- if the rotation speed has fallen below the first SRI threshold then the sequence start is interrupted. This is illustrated in [Fig.4]. Indeed, the success threshold is not reached on the engine speed criterion.

[0082] According to a non-limiting example, the first SRI threshold is a first parameter which can be between 800 Rpm and 1200 Rpm.

[0083] According to a non-limiting example, the second threshold SR2 is a second parameter which can be between 1500 Rpm and 2100 Rpm. Calibration work makes it possible to adjust this first threshold and this second threshold to a given powertrain.

[0084] According to a non-limiting example, the time delay Tpp may be between 100 ms and 400 ms, preferably between 150 ms and 250 ms.

[0085] The time delay Tpp can be a parameter dependent on the state of charge of a traction battery of the vehicle.

[0086] This way, we can compensate by releasing too early by a few hundred ms. This trick remains transparent to the driver.

[0087] The vehicle comprises a control system 10 comprising at least a first electronic computer 3 responsible for controlling the internal combustion engine, and at least a second electronic computer 4 responsible for controlling the electric motor.

[0088] In addition, a third computer may be provided which may be a su- 6-speed drive train monitor.

[0089] It is noted that the role of the supervisory computer can be played by the first computer or the second computer.

[0090] The computers communicate with each other by means of a multiplexed network 62.

[0091] Optionally, the engine temperature may be used. For this purpose, provision may be made to use a sensor 48 which may be managed by the first computer or by another computer, and a wired or multiplexed link 49.

[0092] According to this option, the time delay and / or the first threshold and / or the second threshold are parameters which may depend on the engine temperature.

[0093] It should be noted that in the example illustrated, the electric traction chain CT is arranged on the front axle of the vehicle, with the internal combustion engine 1, and the electric machine 2,

[0094] However, as a variant (not shown) the electric powertrain (CT) may comprise an internal combustion engine 1 on the front axle of the vehicle, and an electric machine arranged on a rear axle of the vehicle.

[0095] We also note that two electric machines can be provided: one on the front axle and one on the rear axle (electric 4x4 configuration possible).

[0096] The person skilled in the art will note that the first computer 3 and the second computer 4 can be implemented in a single unit.

[0097] Regarding the reading of Figures 3 to 6, the top line represents the state of the start button, the second line from the top represents the state of pressing the brake pedal, and the third line from the top represents a logical state of activation of the machine and electrical to drive the crankshaft of the ceramic engine.

[0098] The area just below represents the evolution of the engine speed.

[0099] The bottom line represents the logical state of the startup sequence.

[0100] Furthermore, it should be noted that the electric machine used to start the engine at internal combustion can be, as illustrated in [Fig.l], an alternator-starter involved in the mild hybridization function, but also alternatively a conventional starter, or another electric machine present in the gearbox.

Claims

Claims

1. Method for managing a starting sequence of an internal combustion engine (1) in a hybrid vehicle, the vehicle comprising at least one brake pedal (9) with a brake pedal sensor (91), an initiation member (8) configured to be actuated by a user, at least one control unit of the internal combustion engine, a crankshaft rotation speed sensor (71), characterized in that the method comprises the following steps: a step of activating the initiation member by a user of the vehicle a step of verifying the safety conditions for possible activation of the engine, including at least one condition of the brake pedal being pressed, - a step of activating a means of driving the crankshaft by an electric machine (2), - a recurring measurement of the crankshaft rotation speed, - a step of launching a time delay (Tpp) when the brake pedal is released, and the following conditional actions: (el)- if at the time of releasing the brake pedal, the crankshaft rotation speed is lower than a first speed threshold (SRI), then the starting sequence is interrupted, (e2)- if at the time of releasing the brake pedal, the crankshaft rotation speed is greater than a second speed threshold (SR2), then the start sequence is confirmed and validated, (e3)- if at the time of releasing the brake pedal, the crankshaft rotation speed is higher than the first rpm threshold and lower than the second rpm threshold, then the end of the time delay is waited for, (fl)- if at the end of the time delay, the crankshaft rotation speed is still higher than the first rpm threshold, then the start sequence is considered confirmed and validated, (f2)- if at the end of the time delay, the crankshaft rotation speed is lower than the first threshold, then the start sequence is interrupted.

2. Method according to claim 1, characterized in that the time delay (Tpp) is between 100 ms and 400 ms, preferably between 150 ms and 250 ms.

3. Method according to claim 1, characterized in that the first threshold (SRI) is a first parameter between 800 revolutions per minute and 1200 revolutions per minute.

4. Method according to claim 1, characterized in that the second threshold (SR2) is a second parameter between 1500 revolutions per minute and 2100 revolutions per minute.

5. Method according to claim 1, characterized in that the time delay (Tpp) and / or the first threshold and / or the second threshold are parameters which depend on the temperature of the engine.

6. Method according to claim 1, characterized in that the time delay (Tpp) is a parameter dependent on a state of charge of a traction battery (51) of the vehicle.

7. Method according to claim 1, characterized in that there is further provided a step of additional checks relating to a double-clutch automatic gearbox, including a step of checking an electrical supply to an oil pump and a check of an electrical supply to actuators.

8. Control system (10) in a hybrid vehicle comprising an internal combustion engine (1) and at least one electric motor (2), the control system comprising at least one first electronic computer (3) responsible for controlling the internal combustion engine, and at least one second electronic computer (4) responsible for controlling the electric motor, characterized in that the control system is configured to implement the method according to one of claims 1 to 7.

9. Hybrid vehicle comprising an electric powertrain (CT) arranged on a front axle of the vehicle, comprising an internal combustion engine (1), at least one electric motor (2), and at least one control system according to claim 8.

10. Vehicle comprising an electric powertrain (CT), comprising an internal combustion engine (1) arranged on a front axle of the vehicle, at least one electric motor arranged on a rear axle of the vehicle, and at least one control system according to claim 8.

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