WO2008025912A1

WO2008025912A1 - Procedure for distributing a torque set point on the wheels of a hybrid electric vehicle

Info

Publication number: WO2008025912A1
Application number: PCT/FR2007/051744
Authority: WO
Inventors: Olivier Cayol; Xavier Claeys; Eric Galichet; Marco Marsilia
Original assignee: Renault S.A.S.
Priority date: 2006-08-30
Filing date: 2007-07-27
Publication date: 2008-03-06
Also published as: FR2905333B1; FR2905333A1

Abstract

Procedure for distributing a torque set point Ctot to be distributed over the wheels of a vehicle between: a torque Cav exerted on the front wheels by means of a internal combustion motor; a torque Cfav_g exerted on the front left wheel by means of a left brake; a torque Cfav_d exerted on the right front wheel by means of a right brake; and a torque Car exerted on the rear wheels by means of an electric machine capable of functioning in the generator or in the motor, remarkable in that if a directional instability is detected during the “lifting of foot” phase and which began during the said “lifting of the foot” phase, the following torques are applied during a transition period for a duration Δt : Car = Cav = 0; Cfav_g = max(Ctot/2, CfESP_av_g); Cfav_d = max( Ctot/2, CfESP_av_d); where CfESP_av_g and CfESP_av_d are the braking torque controlled by an electronic integrated chassis control(ICC) at the front left wheel and the front right wheel, respectively, CfESP_av_g and CfESP_av_d being invalid in the absence of an electronic integrated chassis control (ICC).

Description

DISTRIBUTION METHOD ¹ A COUPLE SET ON WHEELS OF A VEHICLE

HYBRID AUTOMOTIVE

The invention relates to a novel method for distributing a set torque C _to t to be distributed on the wheels of a motor vehicle between a torque C _av exerted on the front wheels by means of an internal combustion engine, a torque

Cf _av _g exerted on the front left wheel via a left brake torque Cf _ _av _d exerted on the right front wheel via a right brake, and C _ar torque on the rear wheels through an electric machine capable of operating as a generator or motor. The invention also relates to an onboard computer programmed to execute said method.

The set torque C _tot is calculated as a function of the desired deceleration for the driver's comfort during the legs of the foot.

No. 2,799,417 discloses a method for distributing a set torque on a hybrid four-wheel drive vehicle, depending on the driving conditions. The distribution is made according to certain parameters including:

- the torque requested by the driver,

- the temperature of the electric actuators,

- the condition of the vehicle,

- the difference in the slip state between the front and rear axles. This device aims to provide a directional stability of the vehicle during the phases of "foot lift" including cornering. This device acts for this on the distribution of engine torque between the pair of front wheels and the pair of rear wheels, without affecting the braking torque of the vehicle. It has the disadvantage of only being efficient in terms of energy efficiency for a hybrid vehicle having two electric machines, one at the front and the other at the rear, capable of recovering energy at during the "kick up" phase.

In the case of a hybrid vehicle comprising an electric machine capable of exerting a torque on the rear wheels, and an internal combustion engine capable of exerting a torque on the front wheels to optimize consumption, the phases of "lifting of foot" typically accompanied by a disengagement and a stop of the front combustion engine and energy recovery by the electric machine on the rear axle. Due to this energy recovery, the control of the distribution of the only driving couples is then no longer sufficient to ensure, in all circumstances, satisfactory directional stability of the vehicle. There is therefore a need for a method for ensuring the directional stability, during a "foot-lift" phase, of a four-wheeled vehicle. motor equipped with an electric machine capable of exerting a torque on the rear wheels and an internal combustion engine capable of exerting a torque on the front wheels.

The present invention is intended to meet this need. This object of the invention is achieved with a method of distributing a set torque C _to t to be distributed on the wheels of a motor vehicle between:

a torque C _av exerted on the front wheels by means of an internal combustion engine,

a torque Cf _av _ _g exerted on the left front wheel by means of a left brake,

a torque Cf _av _ _d exerted on the front right wheel by means of a right brake, and

- A torque C _ar exerted on the rear wheels by means of an electric machine capable of operating as a generator or motor, characterized in that if a directional instability is detected during a phase of "foot lift" and it has started during said "foot-lift" phase, the following pairs are applied during a transition period of a duration Δt:

- C _ar = C _av = 0; - Cfavjj = max (C _tot / 2, Cf _ESP _ _av _g);

- Cf _{av d} = max (Ctot / 2, Cf _ESP _ _av _d); where Cf _E sp_av_ _g and Cf _E sp_av_d are the braking torque is controlled by a trajectory control electronic program (ESP) for the front left wheel and the right front wheel, respectively, Cf _E sp_ _av _g and Cf _E sp_ _av _d being zero in the absence of an electronic program for trajectory control (ESP), and C _to t is preferably received by a computer programmed to execute a method according to the invention.

The application of a braking torque to the front wheels avoids a situation of oversteer and allows the vehicle to have on the contrary a sub-steering behavior and even, advantageously, a neutral behavior. This gives the vehicle better directional stability.

Preferably, the method according to the invention comprises one, and more preferably more, of the following optional characteristics: the duration of the transition period Δt is sufficient to allow the start of the internal combustion engine,

- it controls the restarting of the combustion engine at the beginning of the transition period Δt and / or one acts on the brakes, - it controls the immediate stop of the energy recovery by the electric machine at the beginning of the period transition Δt,

after said transition period of a duration Δt, the following pairs are applied:

- C _av + Cfavjj + Cf _av _d = 0.7 Ctot, - C _ar + Cf _ar = 0.3 C _M , with Cf _ar Is torque exerted on the rear wheels by means of rear brakes. Preferably, it is ordered to engage the internal combustion engine,

if a directional instability of the vehicle is detected during a "foot-lift" phase and has begun before said "foot-lift" phase, a distribution of the set-point torque C _to t is applied so that the drag front wheels is greater than that of the rear wheels, preferably a distribution of the setpoint torque C _to t is applied in the following manner:

- C _av + Cf _av _g + Cf _av _d = 0.7 C _to t,

, and preferably, it is ordered to engage the internal combustion engine,

if no directional instability of the vehicle is detected during a "foot-lift" phase, a distribution of the setpoint torque C _to t is applied as follows:

- C _av = 0;

! it is commanded to disengage, and preferably to extinguish, the internal combustion engine and operate the electric machine in generator mode.

The present invention also relates to an on-board computer in a motor vehicle comprising an internal combustion engine for providing the pair of front wheels with a torque C _av and an electric machine to provide the pair of rear wheels a torque C _ar , remarkable in that it is programmed to perform a method according to the invention.

Other features and advantages of the present invention will become apparent in the light of the detailed description of an embodiment, given in a non-limiting manner and to the examination of the figures of the appended drawing in which:

FIG. 1 illustrates the different signals that a computer according to the invention receives and transmits,

- Figure 2 is a logic diagram illustrating the distribution of couples according to a method according to the invention, depending on the different possible situations.

In this embodiment the vehicle is a hybrid vehicle equipped with an internal combustion engine as a power source for the front wheels, and an electric machine for the rear wheels. The vehicle is also equipped with an electronic program for trajectory control (ESP). For a vehicle with this architecture, energy recovery can be done by the electric machine on the rear wheels. Said machine then operates in generator mode providing a deceleration torque to the rear wheels.

The term "foot lift" means the period during which the driver of the motor vehicle does not actuate the brakes or the accelerator of said motor vehicle. It is preferably a deceleration phase of the vehicle engines during which the driver of said vehicle does not actuate the brakes of said vehicle, but does not include a shift phase.

The invention relates to a calculator embedded in a hybrid motor vehicle with four driving wheels. The computer according to the invention is programmed to execute a method according to the invention. It receives several signals that it interprets according to the method according to the invention. As shown in FIG. 1, a calculator according to the invention permanently receives:

a phase signal indicating the beginning and the end of a "foot-lift" phase, a setpoint torque C _to t indicating the total negative torque to be applied to the wheels, in the event of a foot-lift phase, for to obtain a determined deceleration, an ESP signal from the electronic program of trajectory control, and

a stability signal indicating the state of stability of the vehicle.

Said computer executes a method according to the invention and distributes the following pairs:

- Cav,

- Because,

and

"See _ar .

The motor vehicle may be equipped with a detection system known per se analyzing the directional stability state of said vehicle and able to communicate it to a computer according to the invention. Said detection system can thus provide a stability signal in the form of a Boolean signal. This signal is transmitted continuously to the computer and is preferably stored by said computer.

From the combination of the signals received, and during a phase of

"Hoist foot", the computer according to the invention executes the method according to the invention which allows, as described in more detail in the following description, to ensure the directional stability of the hybrid four-wheel drive vehicle during said phase to "kick up".

In step 1, if the phase signal indicates that the vehicle is not in a "foot-lift" phase, the set torque C _tot is distributed between the front and rear wheels in known manner. The computer continues to analyze the signals it receives and in particular to verify that the vehicle does not enter a phase of "foot lift".

If, on the other hand, the phase signal indicates that the vehicle is in the "kick up" phase, proceed to step 2.

In step 2, the computer that receives a vehicle stability signal, analyzes this signal to detect any instability.

If no directional instability is detected, the distribution of the torque C _to t is as follows:

The internal combustion engine is then disengaged, and preferably stopped, the electric machine operates in generator mode and recovers energy from the rear wheels. This situation is the most favorable in terms of energy, but presents a risk of directional instability for the vehicle in case of poor adhesion of the wheels of said vehicle. The computer continues to analyze the signals it receives and in particular to check if the vehicle is still in the "foot-lift" phase as well as the stability of the vehicle.

If on the contrary, the combination of the phase signal and the stability signal indicates that, the vehicle being in the "footing" phase, there is a directional instability, and we go to step 3.

In step 3, the computer that receives a stability signal indicating instability of the vehicle during a "foot-lift" phase analyzes this signal so as to determine whether the beginning of the instability is prior to said phase or not. "Kick up".

If the beginning of the instability is prior to said "foot-lift" phase, the method according to the invention provides for the distribution of C _to t to be applied during the whole of said "foot-lift" phase so as to the drag of the front axle is greater than that of the rear axle. Preferably the distribution is as follows: C _av + _av Cf _ _g _ _av Cf + _d = 0.7 _to t and C Car + Cf = 0.3 _ar C _tot.

The method provides that the computer applies this distribution throughout the duration of said phase of "foot lift". For this the computer continues to check if the vehicle is still in the phase of "foot lift". If the vehicle is in the "foot-lift" phase, the method provides for maintaining said distribution of the set torque C _tot -

If the vehicle is no longer in the "foot-lift" phase, the method provides a distribution of the set torque C _tot between the front and rear wheels in a known manner. If during the instability anestability test, step 3, it turns out that said instability appeared during said "foot-lift" phase, then the method according to the invention provides for a distribution of the torque C _to t of so that the drag of the front axle is greater than that of the rear axle.

In this situation, the method according to the invention provides a transition period of a duration Δt allowing the transition of the distribution of the torque C _to t of the situation: C _av = 0 and C _ar = C _to t at the preferred situation: C _av + Cf _av _ _g + Cf _{av d} = 0.7 C _to t and C _ar + Cf _ar = 0.3 Ctot.

During this period Δt, the method according to the invention controls the immediate stop of the energy recovery at the electric machine. The distribution of the pair C _to t, is from this moment the following one:

Car - C _a v - 0,

Cf _{av g} = max (Ctot / 2, Cf _ES p_ _av _ _g ); Cf _ _BC _d = max (C tot / 2, Cf _av_d _ESP). where Cf _E sp_ _av _g st Cf _E sp_ _av _d is the braking torque controlled by the brakes by an electronic program for trajectory control (ESP) at the front left wheel and the right front wheel respectively. This distribution of couples allows the vehicle to avoid an always critical situation of oversteer. The application of braking torques on the front wheels induces a vehicle understeer behavior, preferably a neutral behavior, much more favorable to the directional stability of the vehicle.

The duration of the period Δt is configurable, preferably it is sufficient to allow the start of the internal combustion engine.

According to the method of the invention, the starting of the engine is controlled during this period Δt, if the engine does not restart it will ensure the distribution of torque C _to t with the brakes.

Once the internal combustion engine is restarted, the method according to the invention distributes the torque C _to t, so that the drag of the front axle is greater than that of the rear axle, preferably so that C _av + Cf _{av g} + See _av _d = 0.7

The method provides that the computer applies this distribution throughout the duration of said phase of "foot lift". For this the computer continues to check if the vehicle is still in the phase of "foot lift".

If the vehicle is in the "foot-lift" phase, the method provides for maintaining said distribution of the target torque C _tot - If the vehicle is no longer in the "foot-lift" phase, the method provides a distribution of the torque set point C _to t between the front and rear wheels in a known manner.

Outside the kick-up period other directional stability control methods are activated. Of course, the present invention is not limited to the embodiment described and shown, provided by way of illustrative and non-limiting example.

In particular, the internal combustion engine may not restart during the transition period Δt, the distribution of the set torque C _to t is then provided by the brakes.

Claims

1. Method for distributing a set torque C _to t to be distributed on the wheels of a motor vehicle between:

a torque Cf _av _ _g exerted on the left front wheel by means of a left brake, - a torque Cf _av _d exerted on the front right wheel by means of a right brake, and

- C _ar = C _av = 0;

- Cf _{av g} = max (Ctot / 2, Cf _ES p_av_g); - Cf _av _d = max (C _tot / 2, Cf _ESP _ _av _d); where Cf _E sp_ _av _g st Cf _E sp_ _av _d are the braking torque is controlled by a trajectory control electronic program (ESP) for the front left wheel and the right front wheel, respectively, Cf _ES p _av _ _g and Cf _ES p_ _av _d being zero in the absence of an electronic program of trajectory control (ESP).

2. Method according to claim 1, wherein the duration of the transition period Δt is sufficient to allow the start of the internal combustion engine.

3. Method according to any one of claims 1 and 2, wherein it controls the restart of the combustion engine at the beginning of the transition period Δt and / or it acts on the brakes.

4. Method according to claim 3, wherein one acts on the brakes during the "foot-lift" phase if the internal combustion engine does not restart during the transition period Δt.

5. Method according to any one of the preceding claims, wherein it controls the immediate stop of the energy recovery at the electric machine at the beginning of the transition period Δt.

The method according to any one of the preceding claims, wherein if directional instability is detected during a "kick-up" phase and started during said "foot-lift" phase, the following couples are applied after a transition period of duration Δt:

- C _av + Cfavjj + Cf _av _d = 0.7 Ont, - C _ar + Cf _ar = 0.3 O _ot , with Cf _ar the torque exerted on the rear wheels by means of rear brakes.

A method as claimed in any one of the preceding claims, wherein if directional instability of the vehicle is detected during a "foot-lift" phase and has begun before said "foot-lift" phase, a distribution of the set torque Oot so that the drag of the front wheels is greater than that of the rear wheels.

8. A method according to any one of the preceding claims, wherein if a directional instability of the vehicle is detected during a phase of

"Lifting of foot" and that it started before said phase of "lifting of foot", one applies a distribution of the setpoint torque Oot in the following way:

"C _av ⁺ Cf _av _g ⁺ Cf _av _d ⁼ 0.7 Oot>

, with Cf _ar the torque exerted on the rear wheels by means of rear brakes.

9. Method according to any one of the preceding claims, according to which if no directional instability of the vehicle is detected before and during the whole "foot-lift" phase, a distribution of the target torque Ctot is applied as follows :

- C _av = 0,

and

• it is command to disengage the internal combustion engine and operate the electric machine in generator mode.

10. On-board computer in a motor vehicle comprising an internal combustion engine for supplying the pair of front wheels with a torque C _av and an electric machine for supplying the pair of rear wheels with a torque C _ar , characterized in that it is programmed to perform a method according to any one of the preceding claims.