FR3043379A1 - METHOD FOR CONTROLLING THE DISPLACEMENT OF A VEHICLE EQUIPPED WITH AUTOMATED TRANSMISSION AT THE SECURE OPENING OF ITS CINEMARY CHAIN - Google Patents

Abstract

A method of controlling the movement of a vehicle equipped with an automated transmission during the safe opening of its driveline to prevent excessive overheating of its components during a movement on a steep ramp, characterized in that that the torque delivered to the wheels by the drive source of the vehicle is estimated in real time to be able to memorize the torque necessary to maintain the immobilized vehicle in case of opening of the drive train, and in that during its opening a crossing of torque between the driving source of the vehicle and its braking system, by the synchronized application of a progressive braking torque to the wheels of the vehicle, by permanently applying to the wheels the stored torque, so as to stabilize the vehicle on the ramp.

Description

METHOD FOR CONTROLLING THE DISPLACEMENT OF A VEHICLE EQUIPPED WITH AUTOMATED TRANSMISSION AT THE SECURE OPENING OF ITS CINEMARY CHAIN

The present invention relates to the control of kinematic chains of motor vehicles, equipped with automatic transmission with a speed reducer, and at least one controlled coupling means.

It relates to the prevention of the risks associated with the momentary loss of control of the vehicle by the driver during the automatic opening of the drive train in order to prevent mechanical breakage related to the overheating of the components of the transmission, in particular under conditions of difficult driving.

More specifically, the subject of the invention is a method for controlling the movement of a vehicle equipped with an automated transmission during the safe opening of its drive train in order to prevent excessive overheating of the components, during a moving on a ramp with a steep gradient.

This invention has a preferred application, but not limited to automatically controlled speed reducers, in which the connection between the power source and the reducer is provided by a mechanical system with one or more clutches, dry or wet, placed under the control of a transmission computer. The drive train can be of the "4x2" "4x4", "6x4", etc. type.

The most common context for opening an automated transmission kinematics system is driving on a steep ramp in the upward direction, forward or reverse. A high torque applied to the wheel can then overheat some components of the clutch systems.

The usual safety response to this type of situation is a quick opening of the coupling system of the drive train, in order not to reach a thermal threshold whose destructive effects would be irreversible on certain components.

EP 1 607 650 discloses a method of taking control of a vehicle by its braking system at the opening of the transmission. The temperature of the clutch is monitored. We gradually open the clutch, while decreasing the engine torque. But the activation of the braking system is later. Under these conditions, there is no predictive analysis of the takeover by the brakes, and the transfer of torque between the engine and the brakes, can not be finely controlled. The unexpected opening of a coupler in the transmission can have serious consequences, such as the sudden reversal of the direction of movement of the vehicle against the will of the driver. The usual response is either an automatic immediate control restart by the vehicle's main braking system, or the driver's action on it. In the particular case of off-road vehicles in crossing situations, or for heavy trucks in maneuver, the risks of loss of control, mechanical breakage or accidents, are high in case of sudden braking, and the displacement in sense reverse of the desired movement, is also very dangerous.

The present invention aims to anticipate the safe opening of a transmission, so as to avoid the loss of momentary control of the vehicle by its driver.

For this purpose, it proposes that the torque delivered to the wheels by the driving source of the vehicle is estimated in real time to be able to memorize the torque necessary to maintain the immobilized vehicle in case of opening of the driveline, and that is carried out during its opening a torque cross between the driving source of the vehicle and its braking system, by the synchronized application of a progressive braking torque to the wheels of the vehicle, by permanently applying to the wheels the stored torque, so as to stabilize the vehicle on the ramp. The invention will be better understood on reading the following description of a nonlimiting embodiment thereof, with reference to the appended drawings, in which: FIG. 1 illustrates a predictive method of opening a clutch; Figure 2 is a simplified flow chart for estimating the torque necessary to maintain a vehicle ramp, and Figure 3 illustrates the instructions for crossing torque between a clutch and brakes.

Figure 1 illustrates from an example, the proposed method for providing the opening of a transmission clutch and control. This control concerns a vehicle equipped with an automated transmission during the safe opening of its driveline in order to prevent excessive overheating of its components, during a movement on a ramp with steep gradient. The particular context is that of a vehicle parked on a steep slope, which it attempts to climb immediately from its takeoff at t = 0. The graph represents the evolution over time of different quantities from a take-off : the energy dissipated in the friction of the clutch Sdis and its gradient Grsdiss (calculated for example with a period of 100 ms, for the measurement of measurement of energy Sais), the speed of movement of the vehicle vVh, the friction temperature Θ, the input speed of the gearbox op, and the speed of the engine com.

In the figure: the mark 1 points the approximation of the engine and primary speeds indicating an attempt of synchronization of the engine on the input shaft of the gearbox; the mark 2 shows a peak of energy Sais dissipated by the clutch friction; this peak is reflected at the reference point 3 by a jump on the dissipated energy gradient curve GrSdis; mark 4 marks a critical temperature threshold de friction; a gradient of dissipated GrSdis energy gradient is crossed at the mark 5: given the large slip, the dissipated energy then increases exponentially; a confirmation time counter increments to the frequency of software recurrence; a calibrated threshold of the counter is reached after the 6 (n> Si) mark; each crossing of the calibrated threshold increments the confirmation time counter; the exceeding of the calibrated threshold triggers the opening of the drive train, and the progressive application of the braking torque. an arbitration and a priority request on the braking system is issued at reference 7.

Thus, the opening of the kinematic chain is anticipated during repeated crossing of a threshold by the energy gradient dissipated in the friction of the clutch. The invention is also based on a new method for evaluating the braking setpoint request, by constructing a transition phase, before the wheels are locked, to ensure a progressive relay between the engine torque transmitted by the clutch until 'to the driving wheels, and the braking torque on all the wheels of the vehicle. For this, the torque delivered to the wheels by the driving source of the vehicle is estimated in real time to be able to memorize the torque necessary to maintain the immobilized vehicle in case of opening of the drive train. During this opening, a torque cross is made between the driving source of the vehicle and its braking system. This crossing is ensured by the synchronized application of a progressive braking torque to the wheels of the vehicle. Thus, the stored torque is permanently applied to the wheels so as to stabilize the vehicle on the ramp.

According to the invention, the progressive braking force of the wheels necessary to take over the clutch system is calculated before its clear loss of torque capacity. A torque crossover between the clutch and the brakes is thus performed, so as not to overload the resisting torque on the clutch, to avoid an uncontrolled movement of the vehicle, and to avoid the locking of the wheels, which would cause a Suddenly.

FIG. 2 presents a nonlimiting example of a logic diagram for estimating the torque needed to maintain the vehicle in ramp, in a particular take-off context corresponding to FIG. 1. The automatic or automated transmission computer ("TA control"), immediately undertakes a reading of the torque to the driving wheels Cm. If the torque is greater than a Cmi threshold, if none of the vehicle brakes are applied (main brake of the vehicle, parking brake and HSA or Hill Start Assist, function of assisting the movement of a vehicle on an uphill slope, to avoid him moving in the opposite direction of the will of the driver]), and if the vehicle began to move [vVh different from 0], a confirmation time counter is incremented regularly. From a counting threshold Si (n> Si), the average torque during the incrementation of the counter CM is calculated and stored. Its value divided by two, determines the minimum braking torque to be applied to each of the four wheels of the vehicle to immobilize the vehicle. The application of the braking torque is carried out as follows (illustrated in a particular example in Figure 3), with a torque cross between the brakes and the clutch, after confirmation of the launch of the takeover strategy. of the vehicle by the braking system: a) request for control by the braking control system; b) torque limiting request to the CME [Effective Engine Torque, representing the available torque at the crankshaft output] minimum]; C) Progressive braking torque request (Nm /

Ms) d) clutch release request: from the value of the actual transmitted torque, application of a progressive decreasing torque transmission setpoint, inversely proportional to the braking torque setting of the wheels.

In summary, the confirmation of the start of the control of the vehicle by the braking system is followed by: a request for control by the braking control system, a request to limit the torque of the driving source , and a request for release of clutch. The application of the braking torque is therefore the result of an arbitration within the vehicle control system imposing the sending of a priority request on the braking system.

In this example, the vehicle is in balance, and is attempting to climb a slope. The torque for each drive wheel is 500 Nm or 1000 Nm in total. The engine torque is lowered to a minimum CME setpoint, following the confirmation of a risk of sudden opening of the kinematic chain in the very short term. The couple crossing is initiated at this moment. It lasts about 200ms. The takeover by the braking system is intended to distribute the 1000 nm on all four wheels. During this crossing, three actions are in phase: the activation of a braking torque rise ramp of 500 Nm per 100 Ms, the release of the clutch friction with torque reduction target transmitted to the wheel drive wheels 500 Nm / 10OMs, taking into account the gear ratio of the transmission, and the motor torque limitation setpoint.

Following the torque crossing, as soon as the braking torque target is reached and the confirmation of the cancellation of the vehicle speed, it is possible to increase the braking torque setpoint so as to guarantee the immobilisation of the vehicle, and to overcome the possible losses of mechanical performance of the system.

In conclusion it should be noted that: o the vehicle is immobilized in 200ms, where the torque crossover guarantees a lack of control or freewheeling and surprise effect where the engine is kept idle, despite a request for driver acceleration, where the clutch is kept open to cool the clutch friction, a warning light can be emitted to the instrument panel, where the incident context can be memorized in the RAM (RAM) of the vehicle calculator.

Indeed, when the immobilization mode imposed by the strategy is abandoned, it may be useful to activate a warning light to the driver, to inform him when the vehicle stops being stabilized on the ramp by the braking system, and thus draw his attention to the need to regain control of the movement.

It can also impose a confirmed support on the brake pedal, before removing the braking system control of the vehicle. For this purpose, an arbitration is preferably carried out between the braking instruction commanded by the driver and that of the control method by imposing on the vehicle the highest of the two.

The advantages of the process of the invention are numerous. Among these, it should be noted its total safety, the guarantee of protection of the mechanical transmission components and the safeguarding of the grip qualities of the tires. According to the analysis criteria selected, the displacement control method makes it possible to confirm an opening of the kinematic chain in the very short term, while it is constrained under torque. The method therefore makes it possible to anticipate and launch a fine control strategy well before the frank opening.

Claims (10)

1. A method of controlling the movement of a vehicle equipped with an automated transmission during the safe opening of its driveline to prevent excessive overheating of its components during a movement on a steep ramp, characterized in that the torque delivered to the wheels by the driving source of the vehicle is estimated in real time to be able to memorize the torque necessary to maintain the immobilized vehicle in case of opening of the kinematic chain, and in that during its opening a torque cross between the vehicle power source and its braking system by the synchronized application of a progressive braking torque to the wheels of the vehicle, by permanently applying to the wheels, the stored torque, so as to stabilize the vehicle on the ramp. 2. A method of displacement control according to claim 1, characterized in that the confirmation of the launch of the takeover of the vehicle by the braking system is followed by: a request for handling by the brake control system , a request for limiting the torque of the driving source, and a request for release of clutch. 3. A displacement control method according to claim 2, characterized in that the application to the clutch a decreasing set of transmitted torque decreases, inversely proportional to the setting of braking torque of the wheels. 4. Method of displacement control according to claim 1, 2 or 3, characterized in that the opening of the kinematic chain is anticipated during repeated crossings of a threshold (Si) by the gradient (GrSdis) of dissipated energy in a clutch friction. 5. Method of displacement control according to claim 4, characterized in that each crossing of the dissipated energy gradient threshold (GrSdis) increments a confirmation time counter whose exceeding of a calibrated threshold (Si) triggers the opening. the kinematic chain and the progressive application of the braking torque. 6. A method of displacement control according to one of claims 2 to 5, characterized in that the application of the braking torque is the result of an arbitration within the control system of the vehicle requiring the sending of a priority request on the braking system. 7. A displacement control method according to claim 6, characterized in that as soon as the braking torque target is reached and the confirmation of the cancellation of the vehicle speed, it is possible to increase the braking torque setpoint, in order to guarantee the immobilisation of the vehicle, and to be free from any loss of mechanical performance of the system. 8. A displacement control method according to one of the preceding claims, characterized in that a warning light is activated to the attention of the driver, to inform him when the vehicle stops being stabilized on the ramp by the braking system. 9. A displacement control method according to one of the preceding claims, characterized in that imposes the driver confirmed support on the brake pedal, before removing the brake system control of the vehicle. 10. Control method according to claim 9, characterized in that it carries out an arbitration between the braking commanded by the driver and the braking system, imposing the vehicle the higher of the two.