CN114616151A

CN114616151A - Starting method for starting an internal combustion engine in a hybrid traction architecture

Info

Publication number: CN114616151A
Application number: CN202080076414.6A
Authority: CN
Inventors: L·戈迪雄; S·布里-卡约
Original assignee: PSA Automobiles SA
Current assignee: PSA Automobiles SA
Priority date: 2019-10-31
Filing date: 2020-10-05
Publication date: 2022-06-10
Also published as: FR3102809B1; FR3102809A1; WO2021084172A1; EP4051896A1

Abstract

The invention relates to a method for controlling the starting of a heat engine (11) belonging to a hybrid traction chain, the hybrid traction chain is mounted on the axle of a motor vehicle equipped with wheels (17), the traction chain further comprising a traction motor (13), a gearbox (15) with a primary shaft (14) and a secondary shaft, and a starter (22) engaged with a starter ring gear of the heat engine (11), when the motor vehicle is in an electric driving phase ensured by the traction motor (13) and a start of the heat engine (11) is requested, the method comprises a selection step for selecting one or both of the starter (22) and the traction motor (13) to ensure the starting of the heat engine (11) as a function of the speed of rotation of the primary shaft of the gearbox (15).

Description

Starting method for starting an internal combustion engine in a hybrid traction architecture

Technical Field

The present invention claims priority from french application 1912279 filed on 31/10/2019, the contents of which (text, drawings and claims) are incorporated herein by reference.

The invention relates to a control method for controlling the starting of a heat engine, in particular in a hybrid traction architecture of a motor vehicle.

Background

As is known, the traction chain of a motor vehicle may comprise a heat engine and a traction motor mounted on the axle (in particular the front axle) of the motor vehicle.

The traction motor is coupled to the heat engine by means of a first clutch. The traction motor is coupled to the gearbox by means of a second clutch. The output shaft of the gearbox is engaged with the wheels of the vehicle by means of a differential.

To start the heat engine, a certain level of torque needs to be applied to the crankshaft. In the case of hybrid traction chains having an electrical architecture with a low operating voltage, for example of the order of 48 volts nominal, the electric motor is dedicated to the mobility of the vehicle. A starter (so-called reinforced starter), which is usually operated on a low-voltage electrical network, in particular 12 volts, is used for starting and restarting the heat engine during driving.

It has been observed that in order to ensure good performance during the transition between the electric drive mode and the hot drive mode, it is necessary to have a very short start-up time (of the order of 500ms), in particular for weak powers of the wheels in the electric drive mode. However, the enhanced starter, by itself, ensuring that torque is provided to the crankshaft, cannot meet the restart time.

Disclosure of Invention

The present invention aims to effectively overcome this drawback by providing a command method for commanding the starting of a heat engine belonging to a hybrid traction chain mounted on the axle of a motor vehicle equipped with wheels, said traction chain further comprising a traction motor, a gearbox having a primary shaft and a secondary shaft, and a starter engaged with a starter ring gear of said heat engine, said traction motor being coupled to said heat engine by means of a first clutch and to the primary shaft of said gearbox by means of a second clutch,

when the motor vehicle is in an electric driving phase ensured by the traction motor and the start of the heat engine is requested, in which the first clutch is open and the second clutch is closed, the method comprises a selection step for selecting one or both members from among the starter and the traction motor to ensure the start of the heat engine as a function of the speed of rotation of the primary shaft of the gearbox.

The invention makes it possible to distribute (mutualiser) the action of the enhanced starter and the action of the traction motor, if necessary, to ensure the starting of the heat engine. The invention thus makes it possible to increase the level of torque supplied to the crankshaft and to reduce the restart time of the heat engine. The invention also makes it possible to limit the power of the traction motor to the maximum, while using an enhanced starter already present on any motor vehicle equipped with a heat engine.

According to an embodiment, the traction motor alone ensures the starting of the heat engine by providing a torque to the crankshaft of the heat engine alone, in case the rotational speed of the primary shaft of the gearbox is less than a threshold value.

According to an embodiment, the traction motor and the starter together ensure the starting of the heat engine by jointly providing a torque to a crankshaft of the heat engine in case the rotational speed of the primary shaft of the gearbox is greater than a threshold value.

According to an embodiment, the method comprises a control step for controlling the partial closure of a clutch mechanically coupling the traction motor with the heat engine and an activation step for activating the starter, so that the starter and the traction motor simultaneously provide a torque to the heat engine to ensure the starting of the heat engine.

According to one embodiment, before activation of the starter is initiated, the clutch is set to a slip state and only a few newton meters are transmitted in order to compensate for a dead travel between the fully open position of the clutch and a point of engagement (point de l change) of the clutch.

According to an embodiment, the control step for controlling the partial closing of the clutch and the activation step for activating the starter are commanded in parallel with each other.

According to an embodiment, the control step for controlling the partial closing of the clutch and the activation step for activating the starter are actuated offset with respect to one another.

According to an embodiment, the threshold value corresponds to the downshift speed (rgime de trogradage de premiere) of the first gear.

According to an embodiment, the drag chain is not equipped with a via-fitting facade (

accessoires) a reversible rotating electrical machine coupled to said heat engine.

The invention also aims to provide a computer comprising acquisition and processing means for acquiring and processing by software instructions stored in a memory and control means necessary to implement the steps of the piloting method for piloting the start of a heat engine as defined above.

Drawings

The present invention will become better understood from a reading of the detailed description of the invention and the accompanying drawings, wherein:

fig. 1 is a schematic view of a traction chain for a motor vehicle implementing a steering method for steering the start of a heat engine according to the invention;

fig. 2 is a schematic view showing the distribution of electrical and mechanical power between the different constituent parts of the traction chain of fig. 1;

figure 3 is a graph of the evolution of the maximum available torque of the traction motor and of the starting threshold of the heat engine with the rotation speed of the primary shaft of the gearbox;

fig. 4 is a time diagram of a strategy implemented for transitioning from the electric drive mode to the thermal drive mode when the rotational speed of the primary shaft of the gearbox is less than a downshift threshold for the first gear;

fig. 5 is a time diagram of a strategy implemented for transitioning from the electric drive mode to the thermal drive mode when the rotational speed of the primary shaft of the transmission is greater than the downshift threshold for the first gear.

Detailed Description

Fig. 1 shows a traction chain 10 for a motor vehicle, comprising a heat engine 11 associated with an inertial flywheel system 12 and a traction motor 13, which are mounted on an axle (in particular a front axle) of the motor vehicle. The heat engine 11 is, for example, a three-cylinder heat engine. In a variant, the heat engine 11 may of course comprise a different number of cylinders.

The traction motor 13 is coupled to the heat engine 11 by means of a first clutch K0. The traction motor 13 is coupled to the gearbox 15 by means of a second clutch K1. The gearbox 15 comprises a primary shaft 14 and a secondary shaft 16 connected to wheels 17 by means of a differential (not shown).

In the electric operating mode, clutch K0 is open and clutch K1 is closed. In the thermal operating mode, both clutches K0 and K1 are closed.

At the fitting elevation, the air conditioning compressor 20 can be coupled with the heat engine 11 by means of a motion transmission device 21. The means 21 may for example comprise a chain or a belt cooperating with a pulley carried by the crankshaft and by the shaft of the compressor 20, respectively.

The starter 22 provides for a cold start of the heat engine 11 and a restart of said heat engine after a disconnection has been performed according to the prevailing conditions. To this end, the starter 22 comprises a drive pinion which meshes with a toothed ring of the heat engine 11.

The traction chain 10 is not equipped with a reversible rotary electric machine coupled to the heat engine 11 via a fitting facade.

Fig. 2 shows an example of the distribution of electrical power (solid arrows) and mechanical power (dashed arrows) between the different components of the traction chain 10.

In the example shown, the traction motor 13 is powered by a traction battery 25. The traction motor 13 may have a supply voltage of 48 volts.

The starter 22 is powered by a battery 28 having an operating voltage of 12 volts. The 12 volt electrical network (reference numeral 26) is coupled to the 48 volt electrical network by means of a dc/dc converter 27.

The computer 23 shown on fig. 1 is able to select one or both of the components from the starter 22 and the traction motor 13 to ensure the starting of the heat engine 11 depending on the rotational speed of the primary shaft of the gearbox 15. The computer 23 is capable of operating the starter 22, the traction motor 13, and the clutches K0 and K1. More generally, the computer 23 comprises acquisition and processing means for acquiring and processing by software instructions stored in a memory, and control means necessary for implementing the steps of the method according to the invention.

Fig. 3 shows the evolution of the maximum available torque Cmax _ MT of the traction motor 13 and of the starting threshold S _ Mth of the heat engine as a function of the rotation speed W _ ap of the primary shaft of the gearbox 15. A starting threshold S _ Mth of the heat engine is determined for optimizing the fuel consumption of the motor vehicle. The starting threshold S _ Mth of the heat engine may vary according to the type of heat engine 11.

It is noted that the torque C provided to the heat engine 11 (to ensure starting of said heat engine) needs to be between 70n.m and 80 n.m.

It can be observed that the torque reserve of the electric motor 13 is sufficient to start the heat engine 11 in the region Z1 when the speed of rotation W _ ap of the primary shaft is less than a threshold value S _ ret, which corresponds to a downshift threshold value for the first gear.

Conversely, since the available torque of the electric motor 13 decreases as the motor speed increases, the torque reserve of the electric motor 13 is insufficient in the region Z2 to start the heat engine 11 when the primary shaft speed W _ ap is greater than the downshift threshold S _ ret for the first gear.

Thus, two restart modes are set. In accordance with a first starting mode, which is carried out when the primary shaft speed W _ ap is less than the downshift threshold S _ ret (see range Z1), the traction motor 13 alone ensures the mobility of the vehicle and provides torque to the crankshaft to effect a restart of the heat engine 11.

In accordance with a second starting mode, which is carried out when the primary shaft rotational speed W _ ap is greater than the downshift threshold value S _ ret (see region Z2), the traction motor 13 and the starter 22 jointly ensure the starting of the heat engine 11 by jointly providing a torque to the crankshaft of the heat engine 11. The starter 22 thus provides a torque in the operating range Z2, in which a drop in the torque of the traction motor 13 is observed.

For motor vehicles, the downshift threshold S _ ret is typically about 1100 revolutions per minute. "about" is understood to mean a change of plus or minus 10% around a target value. It is noted that the downshift threshold S _ ret for the higher gear is at a speed which is at least greater than or equal to the first gear speed.

The strategy required to implement the transition from electric to thermal drive mode at phase Ph _ dem when the rotational speed W _ ap of the primary shaft of the gearbox 15 is less than the downshift threshold S _ ret for the first gear is described below with reference to fig. 4. The upper graph shows the evolution of the torques C of the different constituent parts of the traction chain 10. The lower graph shows the evolution of the rotational speed W of the electric motor 13 and the heat engine 11.

More specifically, before time T0, the heat engine 11 is turned off and torque is applied to the wheels 17 by the traction motor 13. The clutch K1 is closed. The clutch K0 is open.

Between times T0 and T1, the torque transmitted by clutch K1 decreases.

Between times T1 and T2, the rotational speed of the traction motor 13 increases and a step in torque is observed.

Between times T2 and T3, clutch K0 begins to close until it reaches its slip point to transmit torque to the thermal engine 11.

Between times T3 and T4, heat engine 11 is driven in rotation so that its rotational speed increases.

At time T4 and when the heat engine 11 reaches its idle speed at time T5, fuel injection begins, clutch K0 closes, and the torque applied by the traction motor 13 goes to zero. The heat engine 11 starts to transmit torque from time T6.

The vehicle is thus operated in thermal mode (the heat engine 11 transmits torque to the wheels 17, while the electric motor no longer transmits torque to the wheels 17).

The strategy required to implement the transition from electric to thermal drive mode at phase Ph _ dem when the rotational speed W _ ap of the primary shaft of the gearbox 15 is greater than the downshift threshold S _ ret for the first gear is described below with reference to fig. 5. The upper graph shows the evolution of the torques C of the different constituent parts of the traction chain 10. The lower graph shows the evolution of the rotational speed W of the electric motor 13 and the heat engine 11. This strategy aims to obtain the best possible phasing (phasage) between the torque of the starter 22 and the torque of the electric motor 13, while minimizing the energy losses in the clutch K0.

Between times T0 and T1, the torque transmitted by clutch K1 decreases.

Between times T2 and T3, clutch K0 begins to close to transmit torque to the thermal engine 11.

Between times T3 and T3', clutch K0 is slightly slipping and only transmits a few newton meters. This makes it possible to obtain greater responsiveness of the clutch K0, since the dead travel between the fully open position of the clutch K0 and the coupling point of said clutch is compensated. Since the clutch K0 only transmits a few newton meters during this period and does not transmit the reserve torque of the electric motor 13 (which corresponds to the difference between the running torque of the electric motor and the peak torque of the electric motor), the energy loss is reduced.

Between time T3' and Tinj (which corresponds to the time when fuel injection into the engine 11 is started), the starter 22 is activated so that the starter 22 and the electric motor 13 together transmit torque to the heat engine 11 to ensure starting of the heat engine.

The control step for controlling the partial closing of the clutch K0 and the activation step for activating the starter 22 can be actuated in parallel or offset with respect to one another. In any case, the aim is to arrange the maximum torque levels from the two components to the crankshaft of the thermodynamic engine 11 at the same moment in time, tending to maximize the probability.

In fact, a delay may be applied between the control step for controlling the clutch K0 and the activation step for activating the starter 22. These delays represent the time constant and the reaction time of the member at the step. The time uncertainty associated with the reaction time of the starter 22 is considered to be about 50ms (see window F1), which is acceptable for good performance.

When the heat engine 11 reaches its idle speed at time T4, the torque applied by the traction motor 13 becomes zero.

Clutch K0 is closed at time T5 and the heat engine 11 begins to transmit torque from time T6.

Claims

1. A control method for controlling the starting of a heat engine (11) belonging to a hybrid traction chain (10) mounted on the axle of a motor vehicle equipped with wheels (17), the hybrid traction chain (10) further comprising a traction motor (13), a gearbox (15) having a primary shaft (14) and a secondary shaft (16), and a starter (22) engaging with a starter ring gear of the heat engine (11), the traction motor (13) being coupled with the heat engine (11) by means of a first clutch (K0) and with the primary shaft (14) of the gearbox (15) by means of a second clutch (K1),

characterized in that, when the motor vehicle is in an electric driving phase ensured by the traction motor (13) in which the first clutch (K0) is open and the second clutch (K1) is closed and the start of the heat engine (11) is requested, the piloting method comprises a selection step for selecting one or two members from among the starter (22) and the traction motor (13) to ensure the start of the heat engine (11) as a function of the rotation speed (W _ ap) of the primary shaft (14) of the gearbox (15).

2. Operating method according to claim 1, characterized in that the traction motor (13) alone ensures the starting of the heat engine (11) by supplying torque alone to the crankshaft of the heat engine (11) when the speed of rotation (W _ ap) of the primary shaft (14) of the gearbox (15) is less than a threshold value (S _ ret).

3. Operating method according to claim 1 or 2, characterized in that the traction motor (13) and the starter (22) jointly ensure the starting of the heat engine (11) by jointly providing a torque to the crankshaft of the heat engine (11) when the rotational speed (W _ ap) of the primary shaft (14) of the gearbox (15) is greater than a threshold value (S _ ret).

4. The operating method according to claim 3, characterized in that it comprises a control step for controlling the partial closure of a clutch (K0) mechanically coupling the traction motor (13) with the heat engine (11) and an activation step for activating the starter (22) so that the starter (22) and the traction motor (13) simultaneously provide a torque to the heat engine (11) to ensure the starting thereof.

5. Operating method according to claim 3 or 4, characterized in that, before the activation of the starter (22) is operated, a clutch (K0) is put into a slipping state and only a few Newton meters are transmitted in order to compensate for the dead travel between the fully open position of the clutch (K0) and the engagement point of the clutch (K0).

6. The control method according to claim 4 or 5, characterized in that the control step for controlling the partial closing of the clutch (K0) and the activation step for activating the starter (22) are operated in parallel with one another.

7. The control method according to claim 4 or 5, characterized in that the control step for controlling the partial closing of the clutch (K0) and the activation step for activating the starter (22) are actuated offset with respect to one another.

8. The control method according to claim 2 or 3, characterized in that the threshold value (S _ ret) corresponds to a downshift speed of the first gear.

9. The steering method according to any one of claims 1 to 8, characterized in that the hybrid traction chain (10) is not equipped with a reversible rotary electric machine coupled with the heat engine (11) via a fitting facade.

10. A computer (23), characterized in that it comprises acquisition and processing means for acquiring and processing by software instructions stored in a memory and control means necessary to implement the steps of a piloting method for piloting the start of a heat engine (11) as defined according to any one of the preceding claims.