EP1937963A1

EP1937963A1 - Method for starting a hybrid vehicle heat engine

Info

Publication number: EP1937963A1
Application number: EP06820268A
Authority: EP
Inventors: Stéphane RIMAUX; Janette Rimaux
Original assignee: Peugeot Citroen Automobiles SA
Current assignee: PSA Automobiles SA
Priority date: 2005-10-20
Filing date: 2006-10-09
Publication date: 2008-07-02
Also published as: US20080245332A1; WO2007045785A1; JP2009512589A; CN101341041A; FR2892471B1; FR2892471A1

Abstract

The invention concerns a method applicable to a motor vehicle parallel hybrid drive train, comprising a heat engine, at least one electrical machine, a variable speed ratio transmission member, a first clutch linking the heat engine to the electrical machine, and a second clutch linking the transmission member to the electrical machine or to the heat engine. The method includes the following successive steps which consist in: a) placing the first clutch in open position; b) after positioning the second clutch in slip control, powering the electrical machine so as to drive same with kinetic energy higher than the energy required for starting the heat engine; and c) closing the first clutch so as to transmit, from the electrical machine to the heat engine, an energy at least sufficient to compensate the resisting torque of the heat engine shaft, and drive same at a starting speed.

Description

Method of starting a hybrid vehicle engine

The present invention relates to a method of starting an internal combustion engine of a parallel hybrid power train of a motor vehicle.

"Parallel hybrid traction train" is understood to mean a traction chain supplying a wheel shaft with mechanical energy from at least one "irreversible" engine (generally a heat engine), and at least one engine of "reversible" type (usually an electric machine), and wherein the energy node from the two motors is mechanical in nature.

Thereafter, we can designate the irreversible engine by "heat engine" and the reversible motor by "machine (or motor) electric", it being understood that this electric motor can operate in a motor mode and a generator mode.

FIGS. 1 and 2 schematically show two architectures of parallel hybrid traction chains of known type, for example by the French patent application published under No. 2,814,121, to which the invention more particularly applies. 'invention.

In a first architecture, illustrated in FIG. 1, the traction chain 1 essentially comprises, from upstream to downstream towards a wheel shaft 2, a heat engine 3, an electric motor 5, and a transmission member 7 with a gear ratio. variable speed (also called variable speed drive), such as a gearbox. The traction chain 1 further comprises a first clutch 11, connecting the heat engine 3 to the electric machine 5, and a second clutch 12 connecting the electric machine 5 to the transmission member 7. The clutches 11, 12 may be dry type, but in the context of the invention, they will preferably be wet type.

The traction chain of FIG. 1 can thus operate in a pure electric mode, in which the clutch 11 is open so as not to transmit torque between the electric machine 5 and the heat engine 3, and in which only the electric machine 5 provides mechanical energy to the wheel shaft 2, or withdraws. This traction chain 1 can also operate in hybrid modes, in which the clutch 11 is sliding or closed, in order to transmit torque between the heat engine 3 and the electric machine 5. According to a second architecture, the traction chain 101 FIG. 2 differs from that of FIG. 1 essentially in that the heat engine 3 is positioned, functionally, downstream of the electric machine 5, the second clutch 12 connecting the heat engine 3 (and no longer the electric machine 5) to the transmission member 7.

In this second known architecture, the traction chain 101 operates in a hybrid mode, in which the first clutch 11 is sliding or closed, so as to transmit torque between the electric machine 5 and the heat engine 3.

In this second architecture, unlike the first, the power train does not have a pure electrical operating mode.

The invention therefore relates more particularly to a method of starting a thermal engine of a parallel hybrid traction drive of a motor vehicle, said traction chain comprising said engine, an electric machine, a transmission member with a gear ratio. variable speed, a first clutch connecting the engine thermal to the electric machine, and a second clutch connecting the transmission member to the electric machine or the engine.

In the case of the first architecture, the subject of the invention is a method of starting the heat engine from a pure electric driving mode, or from a stopping phase.

In the case of the second architecture, the subject of the invention is a method of starting the heat engine from a stopping phase of the vehicle.

In the known hybrid traction chains, as described with reference to FIGS. 1 and 2, the starting of the heat engine is carried out by closing the first clutch 11 and suddenly increasing the electric power supplied by the electric machine 5.

The inertia of the heat engine being very important, the starting phase of the engine involves a significant sizing of the electric machine, as well as a large supply of electrical energy. This is disadvantageous from the point of view of the size and the cost of the electric machine and its power electronics.

In addition, this energy supply causes, in the starting phase of the engine, significant variations in the torque to the wheel, which are felt by the vehicle users.

The aim of the invention is to remedy these drawbacks, and to propose a starting method of the type previously explained, which makes it possible to limit the dimensioning of the electric machine, and to reduce or even eliminate jolts on the torque at the wheel when starting the engine. For this purpose, the subject of the invention is a method of the type previously described, characterized in that it comprises the successive steps of: a) placing the first clutch in the open position; b) powering the electric machine so as to drive it, according to an engine mode operation, at a speed giving its rotor a kinetic energy greater than the energy required to launch the heat engine, and c) close the first clutch of way to transmit, from the electrical machine to the heat engine, at least sufficient energy to compensate for the resisting torque of the engine shaft of the engine, and drive the latter at a launch speed. Preferably, during step b), the electric machine is powered so that it delivers its maximum torque.

According to optional features of the method according to the invention, applied to the first architecture: - driving the second clutch so as to maintain substantially constant speed and the input torque of the transmission member; and the method comprises the following steps, performed after launching the heat engine consisting in: d) bringing the heat engine to a higher speed at the speed, at the input of the transmission member, and greater than or equal to a minimum speed determined during a transition period determined, and e) close the second clutch.

According to optional features of the method according to the invention, applied to the second architecture: prior to step a), the respective speeds of the electric machine and of the heat engine, at the input of the transmission member, are increased so as to reach a determined speed enabling the vehicle to take off; and after step f), closing the second clutch. Particular embodiments of the invention will now be described in more detail with reference to FIGS. 3 and 4 of the accompanying drawings, in which: FIG. 3 is a graph illustrating the evolution, over time, of rotation speeds and couples in a traction chain according to the first architecture, during the execution of a starting method according to the invention; and FIG. 4 is a figure similar to FIG. 3 for a traction chain according to the second architecture.

In FIGS. 3 and 4, the evolution, as a function of the time t, is plotted on the abscissa, on the one hand of the shaft rotation speeds ω, and on the other hand of the following pairs C:

G0 ₃ , which is the rotational speed of the shaft of the heat engine 3;

- (Os, which is the rotational speed of the rotor of the electric machine 5;

GO ₇ , which is the rotational speed of the input shaft of the variable speed drive 7; and

C ₃ , which is the torque of the shaft of the heat engine 3; - C ₅ , which is the torque of the rotor of the electric machine 5;

C ₇ , which is the torque of the input shaft of the variable speed drive 7; - Cn, which is the torque transmitted by the clutch 11 of the heat engine 3 to the electric machine 5.

In the examples shown, and to simplify the graphs, the pairs have significant slot profiles of quasi-instantaneous variations corresponding to an ideal situation.

FIRST ARCHITECTURE

We will initially describe with reference to Figure 3 a startup method according to the invention, in the context of the first architecture shown in Figure 1.

In the example shown, the starting method is executed from a pure electric driving mode, in which the second clutch 12 transmits torque between the electric machine 5 and the variable speed drive 7; the first clutch 11 being open and transmitting no torque between the electric machine 5 and the heat engine 3. Thus, at the initial moment t = 0, the GO ₇ regime and the C ₇ torque input drive 7 are not zero.

The starting method illustrated in FIG. 3 can be broken down into eight successive phases, hereinafter explained, and referenced in the figure from Pi to Pg. During the entire starting process consisting of these eight phases, the second clutch 12 is driven. to at least partially meet the driver's demand

(resulting in a more or less important support on the accelerator pedal) and avoid that users do not feel jolts when starting the engine.

In the remainder of the description, an example will be considered in which the target regime is constant. First phase Pi _: In the initial state in pure electric rolling, the first clutch 11 being open and the second clutch

12 being closed, the speed G) ₇ at the input of the variable speed drive 7 is equal to the speed (O ₅ of the electric machine 5, while the speed (O ₃ of the engine 3 is zero.

In the same way, the torque C ₇ at the input of the variable speed drive 7 is equal to the torque C ₅ developed by the electric machine 5, the torque of the heat engine 3 C3 being zero. Second phase P2:

At the beginning of this phase is the decision to start the engine 3, taken by a computer, not shown, which implements a pre-programmed strategy of driving the traction chain. The second clutch 12 is brought to slip limit.

The speeds of rotation G0 ₃ , (O ₅ , G) ₇ and the pairs C ₃ , C ₅ , C ₇ are maintained at those of phase 1.

Third phase P ₃ : The electric machine is suddenly powered at full power, so as to reach its maximum torque C _max and go up to speed. The transition to maximum torque is almost instantaneous at the beginning of phase 3, with the regime being progressively increased to its maximum at the end of phase 3.

The torque transmitted by the second clutch 12 is always regulated so as to keep C ₇ constant at the input of the variable speed drive 7.

During this phase, the first clutch 11 remains open, so that the transmitted torque Cn remains zero.

During the third phase P ₃ , the kinetic energy of the rotor of the electric machine 5 is brought to a level higher than the energy required to launch the engine thermal 3, determined, for example from a map.

Fourth phase P ₄ : The electric motor 5 being at its maximum torque, the first clutch 11 is positioned to slide by transmitting a torque Cn greater than the friction resisting torque of the heat engine 3.

The speed of rotation G0 ₅ of the electric motor 5 decreases gradually, while the speed (O3 of the heat engine gradually increases to a launch regime 0> _L at the end of the fourth phase P ₄ .

In the fourth phase P ₄ , the kinetic energy accumulated by the electrical machine 5 during the phase P3 is used to compensate for the inertia and the friction of the shaft of the heat engine 3 and to drive the latter at 0> L launch regime .

The heat engine 3 can then pass the first compressions and be put into autonomous operation.

Fifth phase P _5:

The first clutch 11 remains positioned to slide, allowing a torque helping to take turns of the engine 3. The torque of the engine 3 becomes positive so that its speed can exceed the speed of the input shaft of the drive 7.

At the end of phase 5, the intersection of the speed (O ₃ of the heat engine 3 and G) ₇ input shaft of the variator 7.

Until the end of phase 5, the torque C5 is maintained at its maximum level C _max . Sixth phase Pβ: The first clutch 11 is brought into the closed position.

The torque C ₅ of the electric motor 5 and the second clutch 12 are always controlled to transmit a torque such that the torque C ₇ remains constant, but also so that the speed (O ₅ of the electric machine 5 remains higher than the CO ₇ regime in drive input 7.

Due to the closing of the clutch 11, the speed (O ₃ becomes equal to the speed (O ₅₎ From this phase, the torque C ₅ of the electric machine 5 goes to a level below its maximum value C _max , the electric machine 5 can then operate in motor mode or in generator mode In other words, the torque C ₅ can be motor or resistant, depending on the setpoint torque at the drive input 7.

In the example shown, the torque C5 becomes resistant from phase 6.

Seventh phase P ₇ :

During this phase, the second clutch 12 is closed progressively so that the speeds (O3, (O5 of the heat engine 3 and of the electric machine 5 decrease, in decreasing order, the speed G) ₇ at the input of the variator 7. The latter is If the GO ₇ regime is below a determined minimum threshold, the respective speeds (O ₃ and (O ₅ of the heat engine 3 and of the electric machine 5 are maintained above this minimum value pending the increase of the CO ₇ regime and the exceeding of this threshold.

Eighth phase Ps: This phase represents the end of the starting process, the heat engine 3 being in operation, the two clutches 11, 12 being closed, and the regimes (O3 of the heat engine 3 and (O ₅ of the electric machine 5 coinciding with the speed G) ₇ at the input of the variator 7.

SECOND ARCHITECTURE In FIG. 4, a start-up method according to the invention has been illustrated, in the context of the second hybrid traction-chain architecture represented in FIG. 2.

The starting method is carried out from a stopping phase of the vehicle, wherein the two clutches 11, 12 are open so as to transmit no torque.

The process is described below, being decomposed into seven successive phases, referenced from Si to S ₇ .

First phase Si: This phase corresponds to the initial state of the system, in which the two clutches 11, 12 are open and the heat engine 3 and the electric machine 5 are stopped.

During this phase Si, the start-up decision of the heat engine 3 is awaited. It will be understood that this step can also be performed, when the vehicle is stopped, with an initial speed (O5 of the non-zero electrical machine) Second phase S2:

This phase consists in accumulating kinetic energy in the electric machine 5.

For this purpose, the electric machine 5 is powered at full power so as to reach its maximum torque C _maxr and this almost instantaneously from the initial state. The clutches 11, 12 remain open.

During this phase, the system (O ₅ of the electrical machine 5 gradually increases to its optimal speed value œ _op t As in the phase P ₃ of the first embodiment described in FIG. 3, the purpose of the phase S 2 is to accumulate a kinetic energy in the electrical machine 5, sufficient to compensate for the resisting torque of the motor shaft due to the Inertia and friction, pass the first compression, driving the shaft of the engine 3 at 0> L launch.

Third phase S ₃ :

This is the launch phase of the engine 3.

As the electric machine 5 has reached its optimum speed ω _opt at the maximum torque C _max , the first clutch 11 is positioned so that the torque transmitted to the heat engine 3 is greater than the torque required to start the heat engine 3.

In this phase, the second clutch 12 remains open.

During this phase, the torque C ₃ of the heat engine 3 is a resistant torque, and the engine speed 3 (O ₃ increases gradually up to the launching regime

Fourth phase S ₄ :

The heat engine 3 is launched and its developed torque C ₃ is brought to a level C _p ensuring the continuation of its rise in speed, with a torque C ₅ kept constant at its maximum value C _max .

The torque Cn transmitted by the first clutch 11 can be brought to a value lower than the torque reached during the third phase to limit the vibration phenomena.

In this phase, the second clutch 12 is kept open.

During the third S ₃ and fourth S4 phases, the speed (O ₅ of the electric machine 5 decreases gradually and reaches, at the end of phase 4, a level that remains higher than the 0> L launch regime.

Fifth phase S ₅ : At the beginning of this phase, the first clutch 11 is closed so that from the beginning of phase 5, and until the end of the starting process, the GO ₅ regime remains equal to the speed ( O3.

During this phase, the regimes (O3, (O5 increase jointly to an intermediate value called "take-off" ω _P higher than the set speed (O70.

During this phase, the torque C ₃ of the heat engine 3 C ₃ is, for example, brought to a level C _P at the beginning of the phase 4 and maintained at this level, then is abruptly reduced to the set point C70.

During the entire phase S5, the torque C5 is maintained at its maximum level C _max .

The goal of this phase is to increase the CÙ3 and ω ₅ regimes to reach a specific target ω _P regime allowing takeoff.

This target regime ω _P can be fixed and prerecorded, for example in the form of a map, or calculated during the start command according to various parameters or variables related to the state of the engine 3.

Sixth phase Se:

At the beginning of this phase, the second clutch 12 is brought into the closed position, and the torque C5 of the electric machine 5 is abruptly reduced, for example to a zero value, so that the speeds (O5 and (O3 of the machine Electrical 5 and the heat engine 3 decrease together up to the setpoint (O7 ₀ inverter input. Seventh phase S ₇ :

This phase corresponds to a start of running in hybrid mode and at the end of the starting process of the engine. In the example shown, during this phase S ₇ , the electric machine 5 operates as a generator, and generates a resisting (negative) torque in the traction chain, the torque C ₃ of the heat engine being brought to a level higher than that of Phase Se, in order to increase the speed at the drive input.

In the two embodiments that have just been described, the engine is started by bringing the electric machine to a high speed and using the kinetic energy of the rotor thus stored, before mechanically linking the heat engine to the engine. electric machine.

Thanks to the invention, the starting phase of the engine is not preponderant in the design of the electric machine. It thus becomes possible to use, in the hybrid powertrains, electric machines having a power limited to the needs and the performances required in the different driving phases.

Claims

1. A method for starting a heat engine (3) of a parallel hybrid traction train (1; 101) of a motor vehicle, said traction chain (1; 101) comprising said heat engine (3), at least one electric machine (5), a transmission member (7) with variable speed ratio, a first clutch (11) connecting the heat engine (3) to the electric machine (5), and a second clutch (12) connecting the transmission member (7) to the electric machine (5) or the heat engine (3), characterized in that it comprises the successive steps of: a) placing the first clutch (11) in the open position; b) after positioning the second clutch (12) at the sliding limit, feeding the electric machine (5) so as to drive it, in motor mode operation, at a speed giving its rotor a kinetic energy greater than energy necessary for launching the heat engine (3), and c) closing the first clutch (11) so as to transmit, from the electric machine (5) to the heat engine (3), energy at least sufficient to compensate for the torque resistance of the engine shaft of the engine, and drive it to a launching speed.

2. Method according to claim 1, characterized in that, during step b) is fed to the electric machine (5) so that it delivers its maximum torque (C _max ).

3. A method according to claim 1 or 2, the traction chain (1) being such that the second clutch (12) connects the electric machine (5) to the transmission member (7), the starting being carried out from 'a pure electric driving mode, characterized in that the second clutch (12) is piloted to respond at least partially to the driver's request.

4. A method according to claim 3, characterized in that it comprises the following steps, performed after launch of the engine (3): d) bring the engine (3) to a higher speed regime (GO ₇ ), in input of the transmission member (7), and greater than or equal to a determined minimum speed, and e) closing the second clutch (12).

5. A method according to claim 1 or 2, the traction chain (101) being such that the second clutch (12) connects the heat engine (3) to the transmission member (7), the starting being carried out from a stopping phase of the vehicle, characterized in that prior to step a), the respective speeds (GOs and GÛ ₃ ) of the electric machine (5) and of the heat engine (3) are increased, at the input of the transmission member (7), so as to reach a determined speed (GOp) allowing the vehicle to take off; and in that after step f), the second clutch (12) is closed.

6. Method according to claim 5, characterized in that the speed (G0 _P ) allowing the vehicle to take off is determined from predetermined fixed values or calculated during the start-up command as a function of various parameters or variables related to the vehicle. state of the engine (3).