FR3033758A1 - TRACTION ASSEMBLY FOR A MOTOR VEHICLE - Google Patents

Abstract

A traction unit for a motor vehicle comprising a motor, a set of drive wheels, a torque transmission chain for applying to said train a torque supplied by the engine, and a control device for controlling the torque as a function of the speed of the vehicle and an acceleration command, said set being characterized in that the control device is configured to impose, when the vehicle is stationary and the acceleration control is zero, in anticipation of an anticipated command for a setting in motion of the vehicle, an anticipation torque setpoint (C) between a limit torque (Z0) for the transmission of force by said transmission chain, and a limit torque (Dec) for said setting in motion of the vehicle.

Description

BACKGROUND OF THE INVENTION [0001] The invention is in the field of traction assemblies for a motor vehicle. The traction assembly of a motor vehicle comprises, in general, a thermal or electric engine, then a traction chain which may comprise a clutch, a gear reduction system such as a gearbox, a transmission shaft, a bridge comprising a differential and finally half-shafts wheel operating wheels. The traction chain transmits a torque and is therefore also a transmission chain. In hybrid vehicles with thermal and electric propulsion, two electric motors can be used, one being coupled to the front wheelset and the other to the rear wheelset. [0004] These hybrid vehicles also offer an autonomous traction mode, without driver action, called rampage. This traction mode consists in applying a torque to the wheels in the absence of action of the driver on the brake pedal and on the accelerator pedal, to cause the vehicle to move at low acceleration and low speed, generally from 5 to 12 km / h. We find this behavior for a thermal vehicle equipped with an automatic gearbox with hydraulic torque converter. The application of the engine torque through the traction chain is done by overcoming games that exist in the traction chain, as well as the elasticity and stiffness (that is to say the damping and the stiffness) of it. Thus, it is known that in a range of torque values, quite low in absolute value if the chain is well designed, the power is not transmitted from the motor to the wheels. When the torque control, which varies continuously, is modified so that the range of torque values for which no power is transmitted must be crossed, if no precautions are taken shocks and efforts in torsion on the elements of the chain can be generated. It is desirable to avoid such phenomena, both for the comfort of the driver and the passengers, and for the wear of the mechanical elements. To improve the torque control, it is possible to apply a preventive approval filter to the raw control, which approaches the range of torque values for which the power is not transmitted decreases. the speed of variation of the requested torque. This approval filtering naturally causes a delay in the variation of the torque applied to the wheels. This disadvantage can be felt at the moment when the ramping mode is activated, or at the moment of acceleration controlled by the driver, also referred to as take-off. We speak of degraded vehicle brio, to indicate that a delay is observed by the driver compared to the control it provides, actively pressing the accelerator pedal or passively by releasing the brake pedal. The present invention aims to overcome this problem.

DEFINITION OF THE INVENTION [0011] The invention constitutes a traction unit for a motor vehicle comprising a motor, a set of drive wheels, a torque transmission chain for applying to said train a torque supplied by the engine, and a control device for controlling the torque as a function of the vehicle speed and an acceleration command, said set being characterized in that the control device is configured to impose, when the vehicle is stopped and that the acceleration control is zero, in anticipation of an anticipated command for a movement of the vehicle, an anticipation torque setpoint adapted to take into account the range of torque values in which no power is transmitted. to the wheels and adapted to take into account the damping and the stiffness of the transmission chain, torque setpoint in practice between a limit torque, minimum in absolute value e, for the transmission of forces by said transmission chain, and a minimum limit torque in absolute value for said setting in motion of the vehicle. The invention may comprise additional features, among which 30 - said anticipation torque setpoint is applied for a limited time from a stop of the vehicle, then if the advance order for the setting 3033758 3 movement is not applied, a limiting torque setpoint for limiting power consumption is applied. advance control is a take-off command imposed actively by the driver (for example an action on the brake pedal or an action on the accelerator pedal or a transition from the lever to D for Drive or forwards or R for Reverse or reverse). the advance control is a ramping command in the absence of a braking action by the driver. - The engine is an electric motor or a thermal engine or hydraulic, 10 inertial or chemical. - The drive train is a front wheel train, or a train of rear wheels. The invention also proposes a motor vehicle comprising a traction unit according to the principles thus presented. The vehicle may be a hybrid vehicle having a heat engine and a second engine that may be electric, hydraulic, pneumatic, or based on a flywheel. List of Figures [0014] The invention will be better understood, and other objects, features, details and advantages thereof will appear more clearly in the explanatory description which will follow made with reference to the accompanying drawings given solely as a example illustrating one embodiment of the invention and in which - Figure 1 shows a diagram of a vehicle in which the invention can be implemented. - Figure 2 shows a scenario of torque variations to be applied to the wheels without the benefit of the invention. FIG. 3 is a diagram of one embodiment of the invention. - Figure 4 shows a scenario of torque variations to be applied to the wheels with the benefit of the invention. DETAILED DESCRIPTION OF ONE EMBODIMENT OF THE INVENTION [0015] FIG. 1 shows certain elements of a vehicle in which the invention can be implemented. It is a motor vehicle with two sets of wheels, one being the front gear and the other the rear gear. The wheels are referenced 10. A heat engine 20 is connected to the front wheelset by a gearbox 11. An electric machine 30 5 is also connected to the front wheelset by the gearbox 11. It can in particular operate in a motor mode and act on the front wheel set to cause the vehicle to move forward. An electric machine 40 is in turn connected to the rear wheel train, and when it works in engine mode, it causes the advancement of the vehicle. It can be coupled or uncoupled from the rear wheel train for example by a dog clutch or clutch. A battery 50 is used to power one or the other of the two electrical machines, via one or more inverters 55. Finally, a low voltage battery 60 supplies a starter 22 configured to participate in starting the engine when the one it's off. A converter 65 supports the low-voltage network powered by the ultra-low voltage battery 60 using the power of the network comprising the electrical machines 30 and 40 and the battery 50. [0018] The electrical machines 30 and 40 can be fed through the inverter by a three-phase alternating current while the battery 50 delivers a direct current. In foot-lifted situations, that is, during which no acceleration control is given, the generator-operated electric machine 30 can recharge the battery 50. This energy can then be used to tow the vehicle or to unload the engine to reduce its solicitation and therefore its consumption. The vehicle is equipped with four modes of operation: hybrid mode, minimizing fuel consumption by optimizing the operation of the engine, the gearbox and the electrical machines 30 and 40, a zero emission mode the engine being off, a mode with four-wheel drive to maximize the handling of the vehicle, and a sport mode promoting the performance of the vehicle. Whatever the mode of propulsion, a transmission chain is present between the engine involved and the drive wheels. This transmission chain includes games and damping and specific stiffness, which is a function of the state of the chain. For each transmission chain, there is therefore a range of torque values for which there is no transmission of torque or effort through the transmission chain, and where the speed remains zero. [0022] A rapid variation of the torque value imposed by the motor around the range of torque values thus defined is likely to cause an inverse torsion of the transmission chain or shocks. A filtering function makes it possible to reduce the torque gradient, and to minimize the shocks induced during a crossing of the torque zone. However, this filtering introduces a torque response time, which can, depending on the transmission chain and the circumstances, be of the order of 100 ms to 1 s. FIG. 2 shows a scenario for a vehicle according to the prior art, using a given chain, with an electric or thermal motor. The x-axis represents the time t. The curve 100 represents the brake control, which in the case presented can take either the value 0, in which case the brake is not activated, or the value 1, in which case the brake is activated. Curve 200 shows the speed of the vehicle. The curve 300 has a gross torque setpoint, while the curve 310 is the torque control transmitted to the engine after application of an approval filter on the gross torque setpoint of the curve 300, called thereafter net torque setpoint 310. The range of torque values Z is the range over which there is no torque transmission through the transmission chain. It extends here on both sides of the value 0 Nm. The Dec torque value (for take-off) is the torque value from which the vehicle actually starts to move, the resistance related to dry friction on the road being overcome. It may be greater than the upper limit Zo of the torque value range Z. A take-off torque value in the opposite direction exists on the other side of the range of torque values Z, but it is not commented in the present description. However, a similar reasoning is valid for this value of take-off torque in the opposite direction. In the scenario presented, the vehicle is initially in motion, the brake being released, and in the absence of acceleration control, a negative torque is applied to the engine train due to a phenomenon of engine braking. real or simulated. Moreover, from a moment ti, a brake control 100 is applied. The vehicle slows down and eventually stops.

The gross torque setpoint 300 is brought to the value of 0 Nm. The net torque setpoint 310 is stabilized at 0 Nm also, with a certain delay. From a time t2, the brake control is removed, the gross torque setpoint 300 is increased in the form of a torque ramp, because of a rampage mode 5 which is implemented without action of the driver, or due to a desire to accelerate the driver, in which case the command is a take-off command imposed actively by the driver. The net torque setpoint 310 increases slowly, so as not to cause shocks in the transmission. When the net torque setpoint 310 reaches the torque value Dec, at a time t3, the vehicle begins to move. The duration D is the time between the instant t2 where the gross torque setpoint 300 deviates from the value of 0 Nm to rise to positive values and the instant t3 where the vehicle actually starts to move with a speed not zero. In Figure 3, there is shown an embodiment of the invention. The controller 5000 receives vehicle speed information from a vehicle speed sensor 5100, an acceleration control value from a sensor related to the acceleration pedal 5200, and a control of the vehicle. brake from a sensor linked to the brake control 5300. The control device 5000 calculates the gross torque setpoint 300 (FIG. 2), the net torque setpoint 310 (FIG. 2) and transmits the latter to the engine 6000. In Figure 4, there is shown a scenario implementing an embodiment of the invention. The abscissa axis again represents the time t. Curve 1100 represents the brake control, identical to that shown in FIG. 2. [0035] Curve 1200 shows the speed of the vehicle. The curve 1300 has a gross torque setpoint, while the curve 1310 is the torque control transmitted to the engine after application of an approval filter on the raw torque setpoint of the curve 1300. In the presented scenario the vehicle is initially in motion, the brake being released, and in the absence of acceleration control, a negative torque is applied to the engine train as before. Moreover, from a moment t1, a brake control 100 is always applied as before. The vehicle slows down and eventually stops. The gross torque setpoint 1300 is, in anticipation of a forward acceleration control of the vehicle, brought to a value C, greater than the upper limit Zo of the range of torque values Z and less than the value of Takeoff couple Dec. The net torque setpoint 1310 is stabilized, with a certain delay, at this value C also. The value C is an anticipation value, allowing more favorably resume traction when applying an acceleration command. From a time t2, the raw torque setpoint 1300 is increased in the form of a torque ramp, due to a rampage mode that is implemented without action 10 of the driver, or the fact a desire to accelerate the driver, in which case the command is a take-off command imposed actively by the driver. The net torque setpoint 1310 increases to follow quickly, the torque values in which these instructions evolve being outside the range of torque values Z, since greater than Zo. When the net torque setpoint 310 reaches the torque value Dec, at a time t3 ', very close to t2, the vehicle begins to move. The duration D 'is the time separating the instant t2 where the gross torque setpoint 300 deviates from the value C to rise to positive values and the instant t3' where the vehicle actually starts to advance with a speed not zero. This duration D 'is lower than the duration D shown in FIG. 2. [0040] In order to limit energy consumption, the value of torque C is optimized, so as not to cause waste. In some embodiments, the torque setpoint can be maintained at the value C, different from 0 Nm for a few seconds, or at least for a predetermined time limited for example from the stopping of the vehicle , so that if the anticipated acceleration control has not appeared at the end of this period, the torque setpoint is reduced to 0 Nm, so as to allow energy savings. It may be decided to choose a value different from 0 Nm, the main thing being to look for energy savings. The new torque setpoint is a limiting torque setpoint to limit energy consumption. The torque value C can be varied depending on the life situation, to meet the performance needs of the vehicle and to satisfy the driver. In particular, the control device 5000 may take into account a current brake control value to define said anticipation torque setpoint C. The wheel train may be the front wheelset or the rear wheelset. , and the engine can be thermal or electric. If the advance command is a rearward command, the setpoint torque value C will be placed between the lower limit of the range Z and the take-off torque value in the opposite direction. The invention is not limited to the embodiment of the invention but extends to all variants within the scope of the claims.

Claims (8)

REVENDICATIONS1. Traction assembly for a motor vehicle comprising a motor (6000), a drive train (10), a torque transmission chain for applying to said train a torque supplied by the motor (6000), and a control device (5000) for controlling the torque as a function of the vehicle speed (5100) and an acceleration control (5200), said set being characterized in that the control device (5000) is configured to impose, when the vehicle is at stopping and that the acceleration control (5200) is zero, in anticipation of an anticipated command for a movement of the vehicle, an anticipation torque setpoint (C) between a limit torque (ZO) for the transmission of force by said transmission chain, and a limit torque (Dec) for said setting in motion of the vehicle. 2. traction assembly according to claim 1, wherein said anticipation torque setpoint (C) is applied for a limited time from a stop of the vehicle, and then if the advance command for the setting in motion is not applied, a limiting torque setpoint to limit power consumption is applied. Traction assembly according to claim 1 or claim 2, wherein the advance control is a take-off command actively imposed by the driver. 4. Traction assembly according to claim 1 or claim 2, wherein the advance control is a ramping control in the absence of a braking action by the driver. 5. Traction assembly according to one of claims 1 to 4, wherein the motor (6000) is an electric motor or a thermal engine, hydraulic, inertial or chemical. 6. Traction assembly according to one of claims 1 to 5, wherein the drive train is a front wheel train, or a rear wheel train. 7. Motor vehicle comprising a traction assembly according to one of claims 1 to 6. 3033758 10 8. Vehicle according to claim 7, which is a hybrid vehicle having a heat engine and a second motor that is electric, hydraulic, pneumatic, or based on a flywheel.