FR2906778A1 - METHOD FOR PROHIBITING ENERGY RECOVERY ON A HYBRID MOTOR VEHICLE - Google Patents

Abstract

A method of prohibiting the recovery of energy on a four-wheel-drive hybrid motor vehicle equipped with an electric machine on the rear axle capable of operating as a motor or as a generator so as to recover energy, from a internal combustion engine on the front axle, a sliding sensor of each wheel of the vehicle, delivering a sliding signal G according to the number of sliding wheels, and / or a system for evaluating the maximum difference between the rotational speeds of the first and second wheels, delivering a speed difference signal DV signifying that the difference in speeds exceeds a predetermined threshold wlim, and / or a running detector of a front-end safety system, delivering a signal Fav, and / or a gait detector of a rear axle safety system, delivering a Far signal, which is remarkable in that it prohibits the recovery of energy on the engine. electrical if at least one of the following conditions is fulfilled: a) the slip signal G indicates a sliding function of the number of sliding wheels, b) the difference of speed signal exceeds a predetermined threshold Wlim, c) the safety system the front axle is active, and (d) the rear axle safety system is active.

Description

The invention relates to a novel method of prohibiting recovery

  of energy on a hybrid four-wheel drive motor vehicle equipped with an electric machine on the rear axle adapted to operate as a motor or generator so as to recover energy, an internal combustion engine on the front axle, a sliding sensor of each wheel of the vehicle, delivering a sliding signal G, and / or a system for evaluating the maximum difference between the rotation speeds of a first and second wheels, delivering a speed difference signal DV, and / or an operation detector of a front-end safety system, delivering a signal Fav, and / or an operating detector of a rear-end safety system , delivering a Far signal. The invention also relates to an onboard computer programmed to execute said method. 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 of which: - the torque demanded by the driver, the temperature of the electric actuators, the state of the vehicle, - the difference of the state of sliding between the front and rear trains.

  This device aims to ensure a directional stability of the vehicle 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 being efficient in terms of energy efficiency for a hybrid vehicle with two electric machines, one at the front and one at the rear. In the case of a hybrid vehicle comprising an electric machine capable of operating in generator mode, and an internal combustion engine capable of exerting a torque on the front wheels, to optimize consumption the recovery phases are conventionally accompanied by a disengagement and stopping 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.

2906778 2 Since energy recovery leads to a new source of vehicle instability, there is a need for a method of prohibiting energy recovery by the electric machine depending on the directional stability of the equipped four-wheel drive vehicle. an electric machine capable of operating in generator mode and an internal combustion engine capable of exerting a torque on the front wheels. The purpose of the present invention is to meet this need. This object of the invention is achieved by a method of prohibiting the recovery of energy on a hybrid four-wheel drive motor vehicle equipped with an electric machine on the rear axle capable of operating as a motor or as a generator. in order to recover energy from an internal combustion engine on the front axle, from a sliding sensor of each wheel of the vehicle, delivering a sliding signal G, and / or from an evaluation system of the maximum difference between the rotational speeds of a first and second wheels, delivering a speed difference signal DV, and / or an operation detector of a safety system of the front axle, delivering a signal Fav, and / or an operating detector of a rear-end safety system, delivering a Far signal, characterized in that energy recovery is prohibited on the electric machine if at least one of the following conditions It is filled in: the slip signal indicates a slip, the speed difference signal exceeds a predetermined threshold, the nose-wheel safety system is activated, the rear-end safety system is activated. The method according to the invention allows when a directional instability of the vehicle is detected to prohibit the recovery of energy by the electric machine.

When energy recovery is prohibited, the vehicle can be stabilized by appropriately distributing, between the front and rear trains of the vehicle, the engine and braking torques. The method according to the invention comprises one, and more preferably several, of the following optional features: The safety system of the front axle may be an anti-slip system of the ASR type and / or an anti-lock braking system of the type ABS and / or ESP electronic stabilization system. The rear axle safety system may be an anti-skid system of the ASR type and / or an ESP type electronic stabilization system. - The speed difference signal can be a Boolean signal preferably taking the value 1 If said difference exceeds said threshold and the value 0 otherwise. The sliding signal may be a Boolean signal preferably taking the value 1 if there is a slip and the value 0 otherwise. The difference signal DV can be obtained by comparing a threshold value wpm with the difference between the maximum and minimum value of the signals coming from four wheel speed sensors filtered and brought back to the center of gravity of the vehicle according to the following approximate equations: RR W12 center = W12 W11 center = W11 112 R + + L2 1 2J / E \ 2 R-- + L2 2, LI'E LYE W21_center = W21 + 2r and W22_centre = W22 + 2r with w11 the speed of the front left wheel , w21 the speed of the left rear wheel 20, w12 the speed of the right front wheel and w22 the speed of the right rear wheel, LY the yaw rate of the vehicle, E the vehicle track, R the radius of the turn , L the vehicle wheelbase and r the radius of the vehicle wheels, then the DV signal is fixed at the value 1 if said difference is greater than w,; m, or else the value 0. The sliding signal can be established by determining for each wheel its slip state and by comparing at any moment the number of wheels sliding Nrg with a threshold number Giim, then fixing the sliding signal G to the value 1 if the number Nrg is greater than or equal to the threshold number Giim, or else the value 0.

If energy recovery is prohibited during a foot lift phase, a distribution of a set torque Ctot may be applied so that the drag of the front wheels is greater than that of the rear wheels.

The slip signal can be set to 1 before the safety system is triggered. Moreover the passage of this signal to the value 1 does not necessarily imply the activation of the security system. The invention also relates to an on-board computer in a motor vehicle comprising an internal combustion engine and an electric machine, a vehicle wheel slip detector, a difference detector between the maximum and minimum value of the wheel speed, a operating sensor of a safety system of the front and rear axle, programmed to execute a method according to the invention. Other characteristics 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 on examining the figures of the appended drawing in which: FIG. various signals that a computer according to the invention receives and transmits; FIG. 2 illustrates the combination of signals according to a method according to the invention. In this embodiment, the vehicle is a hybrid vehicle comprising an internal combustion engine as a power source for the front wheels, and an electric machine for the rear wheels. Said vehicle is equipped on the front and rear wheels of an electronic stabilization program of the ESP type as well as an anti-slip system of the ASR type and an anti-lock braking system on the front axle. For a vehicle with this architecture, energy recovery can be done by the electric machine on the rear wheels. The invention relates to a computer 10 embedded in a hybrid automobile vehicle with four driving wheels. The computer 10 according to the invention is programmed to execute a method according to the invention. It receives several signals which it interprets according to the method according to the invention and transmits a signal of prohibition of recovery of energy, S, by the electric machine according to the values of the signals which it receives. As shown in FIG. 1, a computer 10 according to the invention continuously receives: a boolean slip signal G which is a function of the number of wheels of the vehicle in sliding, a boolean DV speed difference signal, a Fav signal of running a safety system on the front axle chosen from an anti-slip system of the ASR type, an ABS anti-lock system 10 and an ESP type electronic stabilization system; a safety system on the rear axle chosen from an anti-slip system of the ASR type and an electronic stabilization system of the ESP type.

Preferably, the motor vehicle is equipped with a sliding detection system known per se analyzing with the aid of a sliding sensor the sliding state of each wheel of the vehicle. For each wheel, said detector calculates the sliding of said wheel. The slip is then compared to a predetermined threshold to determine the slip state of the wheel. In the state of the art, there are several methods for detecting the state of sliding of each wheel of a vehicle, described for example in the patent applications FR0511072, FR0605837 or FR0512087. Preferably, the motor vehicle is equipped with rotational speed detector of each wheel and a detector of the yaw rate of the vehicle.

These types of detectors are known to those skilled in the art. Speeds are expressed in units of the international system. Preferably, the motor vehicle is equipped with a detection system of the start of a safety system of the front and rear axle of the vehicle. The computer 10 executes a method according to the invention and delivers a signal prohibiting the recovery of energy, S, from the combination of the received signals.

FIG. 2 shows in detail the signals received by the computer 10 and how the computer combines them according to a method according to the invention to arrive at the delivery of the signal prohibiting the recovery of energy S. Preferably, the signal S energy recovery prohibition is a Boolean signal, its value indicating a prohibition of the recovery of energy by the electric machine. The energy recovery prohibition signal S has the value 1, indicating a prohibition of recovery if one or more of the incoming signals take the value 1.

The sliding signal G is calculated by the computer according to the invention as illustrated in FIG. 2. It receives Boolean signals whose value specifies the sliding state of each wheel of the vehicle, for the front left wheel, d21. for the left rear wheel, d12 for the right front wheel and d22 for the right rear wheel. In the embodiment described in FIG. 2, the values of the sliding signals of each wheel follow the following convention: di1 = 1 If the wheel slips, patches or locks, d = 0 If the condition of the wheel is normal. Strategies for detecting the slip state of a wheel exist and are well known to those skilled in the art. The computer 10 according to the invention permanently adds the sliding signals of the four wheels. The result of this addition is a number between 0 and 4 which indicates the number of wheels of the vehicle sliding Nrg at any time. The number of wheels in the process of sliding Nrg is compared with a threshold number Giim, suitably chosen, preferably G, m is an integer between 0 and 4. This comparison makes it possible to obtain the slip signal G by means of FIG. a logic comparator according to the convention and the following logic: if Nrg is greater than or equal to G, then m = G indicating a slip of the vehicle, if Nrg is strictly less than G, then M = G indicating 0 no slip of the vehicle.

Preferably, Giim is chosen equal to 4, more preferably Giim is chosen equal to 3, more preferably Giim is chosen equal to 2, more preferably Giim is chosen equal to 1. The slip signal G is analyzed in permanence by the computer 5 according to the invention. If it takes the value 1 then the energy recovery prohibition signal S also takes the value 1 prohibiting the recovery of energy by the electric machine. If the slip signal G has the value 0, the computer according to the invention takes into account the speed difference signals DV and the activation of the safety systems of the trains before Fav and back Far to determine the signal of prohibition of energy recovery S. The speed difference signal DV is calculated by the computer according to the invention as illustrated in FIG. 2. The computer according to the invention receives directly the maximum values W max 15 and minimum value W min of the signals derived from speed sensors filtered and brought back to the center of gravity of the vehicle namely wit_cntre for the left front wheel, W21_centre for the left rear wheel, W12_centre for the front right wheel and W22_centre for the right rear wheel. These signals are obtained from the following approximate equations: WI RR W12 center ù W12 1 center = Wll 2 'R ± E) + L2 RùE 2 + L2 2) IF E tI' E W21 center = W21 + 2r and w22_ center = W22 + 2r with w11 the speed of the left front wheel, w21 the speed of the left rear wheel, w12 the speed of the right front wheel and w22 the speed of the right rear wheel, kF the yaw rate of the vehicle, E la Vehicle Track, R Turn Radius, L Vehicle Wheelbase and r Vehicle Wheel Radius.

Velocity determining means as well as maximum and minimum values are known to those skilled in the art. The calculator according to the invention receives the wmax and Wmin speeds directly in the units of the international system.

The calculator according to the invention makes the difference d between the values w max and w m; n. This difference dw is compared with a threshold value w,; m, suitably chosen. The threshold value w,;, can be a constant of a few radians per second. Preferably, the threshold value w, m is set according to the speed of the vehicle. We can for example fix w, m = (1 + x) V, with V the speed of the vehicle, r r the radius of the wheels and x the maximum percentage of slip acceptable, generally of the order of 10%. This comparison makes it possible to obtain the differential speed signal DV by means of a logic comparator according to the following convention and logic: if dw is strictly greater than w, m, then DV = 1 indicating a difference in speeds that can be dangerous for the stability of the vehicle, if dw is less than or equal to w,; m, then DV = 0 indicating an acceptable speed difference for the stability of the vehicle. The difference signal DV is continuously analyzed by the computer according to the invention. If it takes the value 1, then the energy recovery prohibition signal S also takes the value 1 prohibiting the recovery of energy by the electric machine. If the speed difference signal DV has the value 0, the computer according to the invention takes account of the sliding signals G as well as the activation of the safety systems of the trains before Fav and Far back to determine the signal of the signal. prohibition of energy recovery S. The Fav and Far signals of the safety systems of the front and rear trains, respectively, are analyzed continuously and directly by the computer according to the invention.

The vehicle is equipped with detectors capable of sending a preferably Boolean signal which takes the value 1 when at least one safety system is activated on the front or rear trains of the vehicle. If one of the two signals Fav and Far has the value 1, then the energy recovery prohibition signal S also takes the value 1 prohibiting the energy recovery by the electric machine.

Preferably, the analysis of the Fav and Far signals provides optimum security. However, normally, the sliding signals dij sliding wheels pass to the value 1 always before the activation of the security systems.

Finally, as illustrated in FIG. 2, the energy recovery prohibition signal S takes the value 1 when one of the following events occurs: a) the slip signal G indicates a slip of a number Nrg of sliding wheels greater than a threshold G,; m, 10 b) the speed difference signal exceeds a predetermined threshold w,; m, c) the nosewheel safety system is active, d) the train safety system back is active. Preferably, the computer according to the invention receives a signal indicating the beginning and the end of a lifting phase. The computer can thus distribute a setpoint torque Ctot on the front and rear trains so that during a footing phase, if the energy recovery prohibition signal S takes the value 1, the drag front wheels is greater than the rear wheels. The set torque Ctot is distributed between: a torque Cav exerted on the front wheels by means of an internal combustion engine, a torque Cfav_g exerted on the left front wheel by means of a left brake, a torque Cfav exerted on the right front wheel by means of a right brake 25, and a car torque exerted on the rear wheels by means of an electric machine capable of operating as a generator or motor. 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 which does not include a phase of change of gear ratio. 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 choice of the values defining a slip, a speed difference greater than a threshold, the activation of the safety systems of the front and rear trains is only given as an illustrative but non-limiting example. Other conventions for determining wheel slip, a speed difference greater than a threshold and an activation of the front and rear train safety systems can be imagined.

Claims (9)

  1. A method of prohibiting the recovery of energy on a four-wheel-drive hybrid motor vehicle equipped with an electric machine on the rear axle capable of operating as a motor or a generator so as to recover energy, an internal combustion engine on the front axle, a sliding sensor of each wheel of the vehicle, delivering a sliding signal G as a function of the number of sliding wheels, and / or a system for evaluating the difference between the rotational speeds of the first and second wheels, delivering a difference signal DV meaning that the difference in speed exceeds a predetermined threshold w,; m, and / or a gait detector of a security system of the front gear, delivering a signal Fav, and / or a gait detector of a rear-end safety system, delivering a signal Far, characterized in that the energy recovery is prohibited on the electric machine if at least one of the following conditions is fulfilled: a) the slip signal G indicates a slip, b) the speed difference signal exceeds a predetermined threshold w,; m, c) the safety system of the nose gear is active, (d) the rear-end safety system is active.   2. A method of prohibiting energy recovery according to claim 1, characterized in that the safety system of the front axle is an anti-skid system and / or an anti-lock system and / or an electronic stabilization system .   3. A method of prohibiting energy recovery according to any one of claims 1 and 2, characterized in that the rear axle safety system is an anti-slip system and / or an electronic stabilization system. 35 2906778 12   4. A method of prohibiting energy recovery according to any one of the preceding claims, characterized in that the difference signal DV is a Boolean signal. 5   5. A method of prohibiting energy recovery according to any one of the preceding claims, characterized in that the slip signal G is a Boolean signal.   6. A method of prohibiting energy recovery according to claim 4, characterized in that one obtains the difference signal DV by comparing a threshold value won, the difference between the maximum value and the minimum value. signals from four wheel speed sensors filtered and returned to the center of gravity of the vehicle, W11_center for the left front wheel, W21 center for the left rear wheel, W12_centre for the right front wheel and W22_centre 15 for the right rear wheel, following the following approximate equations: wll center = WI1 R / 12 R + 2J + L2 W12 center = W12 R 12 [Rù + L2 \ 2) 1 E IF E W21center = W21 + 2r and w22_ center = W22 + 2r with w11 la left front wheel speed, w21 left rear wheel speed, w12 right front wheel speed and w22 right rear wheel speed 20, vehicle yaw rate, E vehicle track, R the radius of the turn, L the wheelbase of the veh icule and r the radius of the vehicle wheels.   7. A method of prohibiting energy recovery according to claim 5, characterized in that the slip signal G is established by determining for each wheel its slip state and comparing at any time the number of wheels in the process of drag Nrg with a Glin threshold number.   8. A method of prohibiting energy recovery according to any one of the preceding claims, characterized in that if the energy recovery is prohibited during a leg-up phase, a distribution 2906778 13 d is applied. a set torque Ctot so that the drag of the front wheels is greater than that of the rear wheels.   9. On-board computer in a motor vehicle comprising an internal combustion engine and an electric machine, a sliding sensor of each wheel of the vehicle, a detector of the maximum difference between the speeds of rotation of the first and second wheels, a detector of operating a safety system of the front and rear axle, characterized in that it is programmed to execute a method according to any one of the preceding claims.