FR3080153A1 - METHOD FOR STARTING A THERMAL ENGINE - Google Patents

Abstract

The method is implemented in a hybrid vehicle power train comprising a heat engine (30) and a hybrid transmission system (20) including a rotating electrical machine (202) and a coupling member (203) of the rotating electrical machine to the engine. The method comprises a first step of rotating the heat engine by the rotating electrical machine, a second step of igniting the combustion in the heat engine and a third step of stopping the rotating control of the rotating electric machine when the combustion is established in the engine. According to the invention, during the first, second and third stages, the rotating electrical machine is driven in speed with a predetermined speed setpoint and the coupling member is driven with a transmissible torque setpoint (Ctr) which is determined in accordance with the invention. function of the temperature and the speed of the engine.

Description

The invention relates generally to the field of heat engines, in particular for a motor vehicle. More particularly, the invention relates to a process for starting a heat engine in a hydrous vehicle powertrain comprising a rotary electric machine coupled to the heat engine through a coupling member.

In conventional vehicles with thermal traction, the starting of the heat engine is generally ensured by the starter which brings the engine to a sufficient speed, typically between 200 and 300 rpm, to initiate combustion. When combustion is engaged, the heat engine goes up in speed by itself until reaching an idle speed, generally between 700 and 900 rpm depending on the vehicles.

In recent years, the need to reduce polluting emissions has led car manufacturers to integrate into thermal vehicles the function of automatic stop / restart of the heat engine, called "stop / start" function. The "stop / start" function was initially proposed through an alternator-starter mounted in place of the conventional alternator coupled by belt to the heat engine. As for the starter, the electrical supply of the alternator-starter during starting is ensured by the classic lead battery of the on-board network with very low voltage, of 12 Volts for vehicles and 24 Volts for trucks. Compared to a starter, the alternator starter provides a high quality starting service, particularly in terms of acoustic and mechanical vibrations, but is a relatively expensive solution. A more economical alternative solution for integrating the "stop / start" function was found with the so-called "reinforced" starter. Compared to a conventional starter which is designed to hold around 60,000 starts, the starter used in the “stop / start” function has been reinforced to hold around 200,000 starts / restarts. The starting performance provided by the reinforced starter remains substantially similar to that of the conventional starter and causes discomfort for the user of the vehicle, due to a high level of acoustic and mechanical vibrations and shaking. In addition, starting the engine is only possible when its ring gear is not rotating, which penalizes the "stop / start" function by a variable waiting time between a stop command and a restart command. of the heat engine. Improvements made subsequently to the engagement of the starter pinion in the ring gear of the heat engine have reduced acoustic and mechanical vibrations.

Currently, the starter with pre-engagement of the pinion allows in the "stop-start" function a faster restart of the heat engine after a stop, gear still rotating, with less acoustic and mechanical vibrations compared to the reinforced starter . However, the service of starting / restarting the heat engine remains unsatisfactory for the user who perceives it as noisy and lacking in uniformity in particular in terms of its duration. The combustion engine drive regime before the appearance of the first combustion is dependent on the friction torques of the thermal engine, the mechanical coupling and the gearbox, friction torques which vary with the temperature and affect the duration of the start-up. .

The electrification of powertrains in hybrid vehicles leads to architectures with two power supply networks, namely, the conventional on-board network at very low voltage and an auxiliary low-voltage power supply network, a few hundred volts. The low-voltage auxiliary network is more specifically dedicated to supplying rotating hybrid electric machines, known as "emachines", which provide traction, torque assistance and regenerative braking functions. In architectures where an electric machine is located near the heat engine, it has been proposed to ensure the start of the heat engine by means of the latter. Such a solution is advantageous in that it allows optimization of the starting system of the heat engine, and also of its cost by the possible elimination of the starter. Torque transmission to the engine is generally carried out via an accessory belt or a coupling device. Unlike the starters and alternator-starters mentioned above, the torque supplied to the heat engine by the electric machine can be controlled here, either by controlling the torque of the electric machine or by controlling the coupling member.

When the vehicle is equipped with two electric hybridization machines, one of the machines, coupled to the heat engine, can be responsible for starting the heat engine while the other machine runs the vehicle.

Thus, the document WO2016180806A1 describes a hybrid vehicle equipped with first and second electric motors which are mounted on front and rear transmission trains. The first electric motor is mounted in parallel with the heat engine on the first train and can start the heat engine via a clutch. The second electric motor can be coupled to the first train or to the second train.

The present invention aims to provide a new solution for starting a heat engine which is suitable for a powertrain of a hydride vehicle comprising a rotary electric machine coupled to the heat engine through a coupling member and which guarantees a service of consistent and high quality boot.

According to a first aspect, the invention relates to a method of starting a heat engine in a powertrain of a hydride vehicle comprising a heat engine and a hydride transmission system including a rotating electric machine and a coupling member of the electric machine. rotating the heat engine, the method comprising a first step of driving the heat engine in rotation by the rotating electric machine, a second step of igniting the combustion in the heat engine and a third step of stopping the rotation control of the electric machine rotating when combustion is established in the heat engine. According to the invention, during the first, second and third stages mentioned above, the rotary electrical machine is controlled in speed with a predetermined speed setpoint and the coupling member is controlled with a transmissible torque setpoint which is determined as a function of the temperature and the engine speed.

According to a particular characteristic of the invention, the transmissible torque setpoint is determined by means of a map as a function of the temperature and of the engine speed.

According to another particular characteristic, the third step comprises stopping the rotation control of the rotary electric machine when the torque supplied by the rotary electric machine is less than a predetermined threshold for a predetermined duration.

According to yet another particular characteristic, the method comprises, prior to the first, second and third steps mentioned above, a first phase of dialogue and preparation intervening after an order to start the heat engine issued by a group load coordination supervisor powertrain, this first phase of dialogue and preparation comprising a dialogue between the load coordination supervisor and electronic control units for the heat engine, the hybrid transmission system and the vehicle's power supply system and a definition of the setpoint predetermined regime based on information obtained from this dialogue.

According to yet another particular characteristic, the method also includes a second phase of pressurizing the hybrid transmission system, this second phase occurring after the first phase and comprising torque control of the rotation of the machine electric motor with a torque control setpoint which is determined according to the temperature of the heat engine and the speed of the electric rotary machine.

According to yet another particular characteristic, the torque control setpoint is determined by means of a map as a function of the temperature of the heat engine and of the speed of the rotary electric machine.

According to another aspect, the invention also relates to an electronic control unit comprising a memory storing program instructions for the implementation of the method described briefly above.

According to other aspects, the invention also relates to a powertrain and a vehicle in which the process described briefly above is implemented.

Other advantages and characteristics of the present invention will appear more clearly on reading the detailed description below of a particular embodiment of the invention, with reference to the accompanying drawings, in which:

- Fig.1 is a block diagram of an exemplary architecture of a hybrid powertrain in which is implemented the method of starting a thermal engine according to the invention;

- Figs.2A and 2B shows speed and torque curves for a rotating electric machine and a heat engine included in the hybrid powertrain of Fig.1; and

- Fig.3 shows a succession of steps included in the method of starting the combustion engine according to the invention.

In Fig.1, an example of a hybrid architecture of a motor vehicle powertrain is shown in which the invention is implemented. This hybrid architecture essentially comprises a train of drive wheels 10, a hybrid transmission system with automatic gearbox 20 and a heat engine 30. The train of drive wheels 10 is the front axle in this architecture.

The hybrid transmission system 20 essentially comprises a differential 200, a gearbox 201, a rotary electrical machine 202, a coupling member 203, a mechanical freewheel coupling 204, a mechanical pump 205 and an electric pump 206 An electronic control unit CST is associated with the hybrid transmission system 20 and controls the operation thereof.

The differential 200 connects the gearbox 201 to the drive wheel train 10. The gearbox 201 is coupled, by its primary shaft, to the rotary electric machine 202. The rotary machine 202 is placed between the gearbox 201 and the coupling member 203. The coupling member 203 is here a clutch which transmits the mechanical torque between the rotary electrical machine 202 and the heat engine 30, this transmission of the mechanical torque being able to be controlled between 0% and 100%.

The rotary electrical machine 202 is, for example, a reversible synchronous machine with permanent magnets, of high performance, suitable for traction and regenerative braking in the context of a hybrid engine.

The mechanical freewheel coupling 204 is driven by the heat engine 30 and the rotating electrical machine 202 and is connected to the mechanical pump 205 for actuation thereof. The electric pump 206 and the mechanical pump 205 ensure the pressurization of the fluids in the hydraulic cooling and lubrication circuits.

As also shown in Fig.1, an electronic control unit CM, called "engine control unit" is associated with the heat engine 30 for the control thereof. The CM unit and the CST control unit of the hybrid transmission system 20 communicate with an electronic control unit SCC via a CAN data communication network of the vehicle. The SCC unit is a load coordination supervisor who controls the water powertrain. In particular, the SCC unit coordinates the respective contributions of the heat engine 30 and the rotary electrical machine 202 to the supply of the engine torque for the traction of the vehicle.

Software modules are installed in memories ME of units SCC, CM and CST and authorize the implementation of the engine starting method according to the invention by the execution of program code instructions by a processor .

Referring to Figs.2A and 2B, it is shown the changes over time of the regimes R and the couples C, for the rotary electric machine 202 and the heat engine 30.

The speeds of the electric machine 202 and the heat engine 30 are referenced RME and RMO, respectively. The torques of the electric machine 202 and of the heat engine 30 are referenced CME and CMC, respectively. The idling speed and the starting speed setpoint are referenced R _r and R _C d, respectively.

According to the method of the invention, the starting of the heat engine 30 is carried out at a high speed, that is to say, at a speed of the order of 500 rpm, compared to conventional starting with starter which operates between 200 and 300 rpm approximately. The value of the starting speed is indicated by the starting speed setpoint R _C d and will be determined according to certain conditions, including the temperature of the heat engine 30.

As shown in Figs.2A and 2B, the control of the start of the engine 30 takes place in three phases P1 to P3. Phase P1 is a dialogue phase prior to the start order. The phase P2 is a phase of pressurizing the hybrid transmission system 20. The phase P3 is a phase of rotational driving of the heat engine 30 by the rotary electric machine 202 and of starting up properly speaking of the latter. There is also shown a phase P4 which is an idle regulation phase occurring after starting.

Referring also to Fig.3, the starting method according to the invention uses a control process which takes place in nine steps, S1 to S9, executed during phases P1 to P3.

Steps S1 to S5 are executed during the prior dialogue phase P1 in which the RME, RMO regimes, and the CME, CMO couples are harmful.

Step S1 corresponds to a request to start the heat engine 30 which is formulated by the load coordination supervisor SCC and initiates the start sequence. The start request is transmitted to the engine control unit CM by the load coordination supervisor SCC. In addition, in this step S1, the control unit CST of the hybrid transmission system 20 is informed by the load coordination supervisor SCC of a need to start the heat engine 30. The control unit CST can thus verify the state of the various components of the hybrid transmission system 20 and prepare them, in particular the rotary electrical machine 202, for an operation for starting the heat engine 30.

In step S2, the engine control unit CM supplies the load coordination supervisor SCC with a minimum speed value that the heat engine 30 must reach, without combustion, during the phase P3 of rotational drive of the heat engine 30 by the rotary electric machine 202. This minimum speed value is defined in order to obtain good combustion in the heat engine 30, when this is initiated to cause starting. The minimum speed value is used by the load coordination supervisor SCC to set the starting speed setpoint R _C d.

In step S3, the charge coordination supervisor SCC verifies the capability of the electrical supply system to supply the rotary electrical machine 202 with the electrical energy necessary to start the heat engine 30, by interrogating an electronic unit. control unit managing the power supply system. In the event that the state of charge of the battery of the power supply system is not sufficient to ensure a high-speed start by means of the rotary electrical machine 202, the charge coordination supervisor SCC may opt for a another start-up strategy, compatible with energy availability.

In step S4, if the start at high speed is validated, the load coordination supervisor SCC informs the engine control unit CM that a start will be made, specifying the start mode at high speed and the starting speed setpoint R _C d.

The prior dialogue phase P1 ends with step S5. In this step S5, the charge coordination supervisor SCC informs the unit CST of the hybrid transmission system 20 of a control mode required for the rotary electric machine 202 and of the starting speed setpoint R _C d.

The next step S6 occurs during phase P2. In step S6, the rotary electrical machine 202 is controlled in rotation so as to ensure pressurization of the hybrid transmission system 20. The coupling member 203 is open and the RMO speed of the heat engine 30 is zero. In this step S6, it is a question of pressurizing in particular the lubrication circuits so as to minimize the friction torque.

In this step S6, the rotary electrical machine 202 is driven in torque by the CST unit. For piloting purposes, the CME torque supplied by the rotary electrical machine 202 is measured or estimated by techniques known to those skilled in the art. The CST unit uses a mapping CA1 which delivers a torque setpoint as a function of the temperature of the heat engine 30 and of the RME speed of the rotary electric machine 202. The temperature of the heat engine 30 is estimated from the temperature of the heat transfer liquid. cooling engine 30.

Referring to Figs.2A and 2B, throughout phase P2 (step 6), the rotary electrical machine 202 therefore provides a CME torque of positive value which is determined by the torque setpoint delivered by the mapping CA1. As can be seen in FIG. 2A, the RME speed of the rotary electrical machine 202 here increases rapidly at the start of phase P2 (step 6) and then stabilizes at a substantially constant value. Phase P2 (step 6) ends when the hybrid transmission system 20 is under pressure.

The next step S7 occurs during phase P3. In step S7, the coupling member 203 is closed for a transmission of torque to the heat engine 30. During the entire phase P3, the rotary electric machine 202 is controlled in speed. The RMO speed of the heat engine 30 is brought to the starting speed setpoint R _C d only by means of the torque CME supplied by the rotary electric machine 202. During this step S7, in order to control the gradient of the speed RMO of the engine thermal 30, the load coordination supervisor SCC defines a transmissible torque setpoint C _tr (FIG. 1) which is transmitted to the coupling member 203 by the unit CST. The transmissible torque setpoint C _tr is defined as a function of the temperature of the heat engine 30 and of the RMO speed of the heat engine 30. A mapping CA2 is typically used to determine the transmissible torque setpoint C _tr from the temperature of the heat engine 30 and the RMO speed of the heat engine 30. The temperature of the heat engine 30 is estimated from the temperature of the heat transfer liquid for cooling the heat engine 30. The CM unit activates (AIR arrow) the air supply function of the heat engine 30 at the start of the rotation thereof. The unit CM controls the positioning of the actuators of the air supply as a function of the temperature of the heat engine 30 and of its RMO speed.

In step S8, still during phase P3, when the RMO speed of the heat engine 30 reaches a threshold SR = C _C d - dR, the ignition point calculation function, with its advance, is activated (arrow AL). Once combustion has started, following activation of the ignition, the heat engine 30 begins to supply a positive CMO torque, as visible in FIG. 2B. The speed RMO and the torque CMO of the heat engine 30 then increase rapidly towards the idle speed R _r under the control of the engine control unit CM.

The start sequence start command intervenes at the end of phase P3, in step S9, on the detection of satisfactory combustion of the heat engine 30. The satisfactory combustion of the heat engine 30 is detected by the control process when the rotary electrical machine 202 supplies a torque CME having a negative value and less than a threshold value SC (FIG. 2B) for a minimum duration DM (FIG, 2B). The threshold value SC of the negative CME couple and that of the minimum duration DM are calibrated beforehand. When the autonomy of the heat engine 30 is confirmed by the detection of satisfactory combustion, the control of the rotary electric machine 202 is interrupted. The speed RMO of the heat engine 30 is then regulated around the idle speed R _r by the engine control unit CM which proceeds in a conventional manner. If the coupling member 203 remains closed, typically in preparation for a movement of the vehicle requested by the driver, the rotary electrical machine 202 continues to be driven by the heat engine 30, here idle and at idle speed R _r as shown in Figs. 2A and 2B, waiting for a new piloting. Otherwise, if the coupling member 203 is open and the rotary electrical machine 202 is not controlled, its RME speed gradually returns to zero.

The invention allows an optimized starting of the engine in terms of driver experience, fuel consumption and emission of pollutants. The torque and then speed control of the rotating electric machine allows pressurization of the hybrid transmission system and optimized drive of the heat engine up to a rotation speed very close to idle speed. A possible stalling of the thermal engine by a premature end of training is avoided thanks to a reliable detection of the good combustion of the thermal engine from the torque of the rotating electric machine.

The invention is not limited to the particular embodiment which has been described here by way of example. Those skilled in the art, depending on the applications, may make different modifications and variants coming within the scope of protection of the invention.

Claims (9)

1. A method of starting a heat engine in a hydride vehicle powertrain comprising a heat engine (30) and a hydride transmission system (20) including a rotary electric machine (202) and a coupling member (203) of said machine electric motor (202) to said heat engine (30), the method comprising a first step (S7) of rotating said heat engine (30) by said electric electric machine (202), a second step (S8) of ignition combustion in said heat engine (30) and a third step (S9) of stopping the rotation control of said rotary electric machine (202) when combustion is established in said heat engine (30), characterized in that, during said first, second and third stages (S7 to S9), said rotary electrical machine (202) is controlled in speed with a predetermined speed setpoint (R _C d) and said coupling member (2 03) is controlled with a transmissible torque setpoint (C _tr ) which is determined as a function of the temperature and of the speed (RMO) of said heat engine (30). 2. Method according to claim 1, characterized in that said transmissible torque setpoint (C _tr ) is determined by means of a map (CA2) as a function of the temperature and of the speed (RMO) of said heat engine (30). 3. Method according to claim 1 or 2, characterized in that said third step (S9) comprises stopping the rotation control of said rotary electric machine (202) when the torque (CME) supplied by said rotary electric machine is less than a predetermined threshold (SC) for a predetermined duration (DM). 4. Method according to any one of claims 1 to 3, characterized in that it comprises, prior to said first, second and third steps (S7 to S9), a first phase (P1; S1 to S5) of dialogue and preparation intervening after a start order of said heat engine (30) issued by a load coordination supervisor (SCC) of said powertrain, said first phase of dialogue and preparation (P1; S1 to S5) comprising a dialogue between said supervisor of coordination of load (SCC) and electronic control units (CM, CST) of said heat engine (30), of said hybrid transmission system (20) and of the power supply system of said vehicle and a definition of said predetermined speed setpoint (Rcd ) based on information obtained from said dialog. 5. Method according to claim 4, characterized in that it also comprises a second phase (P2; S6) of pressurizing said hybrid transmission system (20, 201), said second phase (P2; S6) intervening in the following said first phase (P1; S1 to S5) and comprising a torque control of the rotation of said rotary electric machine (202) with a torque control instruction which is determined as a function of the temperature of said heat engine (30) and the speed (RME) of said rotary electrical machine (202). 6. Method according to claim 5, characterized in that said torque control setpoint is determined by means of a map (CA1) as a function of the temperature of said heat engine (30) and of the speed (RME) of said electric machine rotating (202). 7. Electronic control unit (SCC, CM, CST) comprising a memory (ME) storing program instructions for implementing the method according to any one of claims 1 to 6. 8. Powertrain comprising a heat engine (30) and a hydride transmission system (20) including a rotary electric machine (202) and a coupling member (203) of said rotary electric machine (202) to said heat engine (30) , characterized in that it comprises at least one electronic control unit (SCC, CM, CST) according to claim 7. 9. Vehicle comprising a powertrain according to claim 8.