FR3078669A1 - METHOD AND SYSTEM FOR PROTECTION AGAINST OVER-TRACTION OF ACTUATORS PRODUCING A TORQUE FOR MOTOR VEHICLE WITH ELECTRIC OR HYBRID PROPULSION - Google Patents

Abstract

System (40) for the over-revving protection of at least two torque actuators (12, 14) of a motor vehicle with electric or hybrid propulsion, comprising a module (42) for calculating a target maximum speed value ( Target Vmax) of the vehicle according to the maximum speed (N_max) the most limiting of the speeds of the two actuators (12, 14).

Description

Method and system for protection against overspeed of actuators producing a torque for an electric or hybrid propulsion vehicle

The present invention relates to the field of motor vehicles with electric propulsion comprising two actuators with electric energy, or hybrid comprising, on the one hand, a fossil energy actuator and, on the other hand, an electric energy actuator.

The torque producing actuators are subjected to maximum rotation speed constraints, for example in order to protect them or for operation in degraded mode.

In motor vehicles provided with a single torque actuator, for example a vehicle with thermal propulsion, it is sufficient to directly limit the speed of the actuator in order to avoid the overspeed of said actuator.

However, limiting the speed of a torque actuator is no longer sufficient when it is a motor vehicle with electric or hybrid propulsion, provided with several torque actuators. In fact, the second torque actuator can continue to transmit power to the vehicle and make it accelerate. This acceleration of the motor vehicle can then generate an overspeed of the first torque actuator.

Limiting the speed of each of the torque actuators in an electric or hybrid propulsion vehicle is also not satisfactory. Indeed, the maximum speed of an electric machine is generally higher than the maximum speed of a heat engine, so that by limiting the speed of the heat engine, the electric machine, which has not reached its maximum speed, continues to transmit engine torque to the vehicle wheels and therefore to make it accelerate. The engine speed is forced to exceed its maximum speed.

Reference can be made to document US Pat. No. 5,774,820 - A, which describes a method for limiting the speed of a motor vehicle.

However, this document does not relate to a motor vehicle with electric or hybrid propulsion and does not propose to protect the torque actuators against the overspeed.

There is a need to provide effective protection against overspeed of the torque actuators of an electric or hybrid powered vehicle.

The subject of the invention is a method of protecting against overspeed of at least two torque actuators of a motor vehicle, in which a target maximum speed value of the vehicle is calculated according to the maximum speed most limiting of the speeds of the two actuators.

The speed of a vehicle is limited in order to protect the torque actuators from possible overspeed.

Thus, by limiting the speed of the vehicle by the constraint of the most limiting speed of the torque actuators on a given gearbox ratio, the risk of overspeed is eliminated for each of the torque actuators.

To calculate the target maximum speed value, the maximum speed of the first actuator is converted into speed as a function of the gear ratio between said first actuator and the wheel and the maximum speed of the second actuator is converted into speed as a function of the gear ratio between said second actuator and the wheel. Then, the two previously calculated speeds are compared and the minimum speed between said speeds is selected.

Advantageously, a maximum torque limitation value is calculated as a function of the maximum target speed, the maximum nominal torque, a speed margin and the speed of the vehicle.

The maximum torque limitation corresponds to a straight line whose slope makes it possible to join the maximum torque curve and the target maximum speed to a zero resistive torque value.

Indeed, it is assumed that the maximum advancing torque is zero at the maximum target speed in order to have a maximum torque always lower than the resistive torque.

For example, it is checked whether the conditions required to trigger the torque limitation are satisfied, for this purpose, we subtract the target maximum speed with a predetermined speed margin to obtain a second target maximum speed value and we compare between said second speed maximum target with vehicle speed, if the vehicle speed is greater than or equal to the second maximum target speed, the conditions required to trigger the torque limitation are satisfied.

Thus, the torque limitation is only activated when the vehicle speed approaches the maximum target speed.

Advantageously, a final torque limiting value is calculated and it is transmitted to the general computer, to calculate said final torque limiting value, and a first minimum value is determined between the maximum torque limiting value and a threshold value, determines a first maximum value between said first minimum value and the minimum value of nominal torque. Said final torque limitation value corresponds to a second minimum value between the first maximum value and the maximum nominal torque value.

According to a second aspect, the invention relates to a system for protection against overspeed of at least two torque actuators of a motor vehicle, comprising a module for calculating a target maximum speed value of the vehicle according to the maximum speed the most limiting of the two actuator regimes.

The module for calculating a target maximum speed value for this purpose comprises a first module for converting the maximum speed of the first actuator into speed as a function of the reduction ratio between said first actuator and the wheel and a second speed conversion module maximum of the second actuator in speed as a function of the reduction ratio between said second actuator and the wheel.

The module for calculating a target maximum speed value also includes a module for comparing the two previously calculated speeds and for selecting the minimum speed between said speeds.

Advantageously, the system comprises a module for calculating a maximum torque limitation value as a function of the maximum target speed, the maximum nominal torque, a speed margin and the speed of the vehicle.

The maximum torque limitation corresponds to a straight line whose slope makes it possible to join the maximum torque curve and the target maximum speed to a value of zero resistive torque.

Indeed, it is assumed that the maximum advancing torque is zero at the maximum target speed in order to have a maximum torque always lower than the resistive torque.

For example, the system comprises a module for verifying the conditions required to trigger the torque limitation, comprising a first subtractor delivering a target maximum speed value corresponding to the subtraction between the target maximum speed and a predetermined speed margin and a comparator between said second target maximum speed and the vehicle speed, the required conditions being satisfied when the vehicle speed is greater than or equal to the second target maximum speed.

Thus, the torque limitation is only activated when the vehicle speed approaches the maximum target speed.

The system can also include a module triggering the torque limitation when the required conditions are satisfied, said module comprising a first module determining a first minimum value between the maximum torque limitation value and a threshold value, a second module determining a maximum value between said first minimum value and the minimum nominal torque value. Said module further comprises a third module determining a final value of maximum torque limiting the conductor corresponding to the minimum value between the maximum value and the maximum value of nominal torque.

According to a third aspect, the invention relates to a hybrid propulsion motor vehicle comprising a system for protection against the overspeed of the two torque actuators as described above, in which the first torque actuator is a source of fossil energy and the second torque actuator is a source of electrical energy.

According to a fourth aspect, the invention relates to a motor vehicle with electric propulsion comprising a system for protection against the overspeed of the two torque actuators as described above, in which the two torque actuators are sources of electrical energy.

Other objects, characteristics and advantages of the invention will appear on reading the following description, given solely by way of non-limiting example, and made with reference to the appended drawings in which:

- Figure 1 schematically shows the architecture of a motor vehicle according to the invention;

Figure 2 schematically illustrates a force / speed graph;

- Figure 3 shows in detail the protection system against overspeed of Figure 1; and

FIG. 4 illustrates the steps of a method of protection against the overspeed according to the invention implemented by the system of FIG. 3.

As illustrated very diagrammatically in FIG. 1, a hybrid propulsion motor vehicle, referenced 10 as a whole, comprises a powertrain comprising a heat engine 12, an electric machine 14, a transmission 16 receiving a torque of the heat engine 12 and a couple of the electric machine 14, and a battery 18 connected to the electric motor 14.

The transmission 16 comprises a gearbox, such as for example a planetary gear (not shown) which distributes the torque to fixed gear ratios connected to the wheels 20a, 20b of the vehicle. A differential mechanism 22 can be placed between the transmission 16 and the output shaft of the wheels 20a, 20b. The wheels can be the front wheels of the hybrid vehicle.

In the following description, the heat engine 12 and the electric machine 14 will be referred to respectively as the first torque actuator and the second torque actuator.

The hybrid vehicle powertrain 10 comprises an electronic control unit (ECU) 30 which controls the first actuator 12 and an inverter 32 which controls the second actuator 14. The hybrid vehicle powertrain 10 further comprises a general computer 34, known as in Anglo-Saxon terms "Hybrid Electric Vehicle Calculator" (HEVC) which controls both the electronic control unit (UCE) 30, the inverter 32 and the transmission 16 according to the data supplied by different sensors and torque control instructions requested by the driver of the vehicle.

FIG. 2 represents a graph having for the abscissa the speed of the vehicle expressed in km / h and for ordinates the force expressed in N.

A first curve C1 represents the maximum torque at the wheel, a second curve C2 represents the minimum torque at the wheel and a third curve C3 represents the resistive torque.

When the driver presses the vehicle's accelerator pedal, a torque setting at the wheels is calculated and transmitted to the wheels. The driver has access to the entire wheel torque zone between the maximum and minimum torque. The maximum speed Vmax of the vehicle is thus defined at the intersection of the curve C1 of maximum torque and the curve C3 of resistive torque.

As shown in FIG. 3, the motor vehicle comprises a system 40 for protection against the overspeed of the two actuators 12, 14, integrated directly into the general computer 34.

The overspeed protection system 40 comprises a module 42 for calculating a target maximum speed value Vmax target of the vehicle as a function of the maximum speed N max most limiting of the speeds of the two actuators 12, 14.

The module 42 therefore includes a first module 44 for converting the maximum speed Nmax l of the first actuator 12 into speed Kl as a function of the reduction ratio between said first actuator 12 and the wheel and a second module 46 for converting the maximum speed Nmax_2 of the second actuator 14 at speed K2 as a function of the reduction ratio between said second actuator 14 and the wheel.

The module 42 also includes a module 48 for comparing the two speeds Kl, K2 previously calculated and for selecting the minimum speed between said speeds Kl, K2.

The overspeed protection system 40 includes a module 50 for calculating a maximum torque limitation value Cmaxlim as a function of the target maximum speed Vmax target, the nominal maximum torque Fmax nom, a margin M of speed and the speed of the vehicle V. The maximum torque limitation Cmax lim corresponds to a straight line dl, visible in FIG. 2, the slope of which makes it possible to join the curve C1 of maximum torque and the maximum target speed Vmax target to a value of resistive torque no.

Indeed, it is assumed that the maximum advancing torque is zero at the maximum target speed in order to have a maximum torque always lower than the resistive torque.

In order to limit the speed of the vehicle on a steep downward slope, the straight line dl extends to the curve C2 of minimum torque, delimiting a zone Z of deceleration, grayed out in FIG. 2. Thus, the maximum torque can decrease up to to the minimum available torque.

The overspeed protection system 40 also includes a module 60 for verifying the conditions required to trigger the torque limitation and a module 70 triggering the torque limitation when the required conditions are satisfied.

The module 60 for verifying the required conditions includes for this purpose a first subtractor 62 delivering a target maximum speed value Vmax_cible2 corresponding to the subtraction between the target maximum speed Vmaxcible and a predetermined speed margin M, a comparator 64 between said second maximum speed target Vmax_cible2 and the speed of vehicle V.

If the vehicle speed V is greater than or equal to the second maximum target speed Vmax_cible2, the module 70 consolidates and triggers the torque limitation. Thus, the torque limitation is only activated when the vehicle speed approaches the maximum target speed.

To this end, the module 70 for triggering the torque limitation comprises a first module 72 determining a first minimum value Min_C equal to Min (Cmaxlim; SI) between the maximum torque limitation value Cmax lim and a threshold value SI, a second module 74 determining a maximum value Max_C equal to Max (Min (Cmax lim; SI); Cmin) between said first minimum value Min_C and the minimum value of nominal torque Cmin.

The module 70 further comprises a third module 76 determining a final value CmaxlimF of maximum torque limiting the conductor corresponding to the minimum value between the maximum value Max_C and the maximum value of nominal torque Cmax.

FIG. 4 represents the steps of a method 100 of protection against the overspeed of the two actuators 12, 14, implemented by the protection system 40 of FIG. 3.

In a first step 102, a target maximum speed Vmax target value of the vehicle is calculated as a function of the maximum speed N max most limiting of the speeds of the two actuators 12,

14.

To calculate the target maximum speed value Vmax target, the maximum speed Nmax l of the first actuator 12 is converted into speed Kl as a function of the reduction ratio between said first actuator 12 and the wheel and the maximum speed Nmax_2 of the second actuator 14 is converted in speed K2 as a function of the reduction ratio between said second actuator 14 and the wheel. Then, the two speeds Kl, K2 previously calculated are compared and the minimum speed between said speeds Kl, K2 is selected.

During a second step 104, a maximum torque limitation value Cmaxlim is calculated as a function of the maximum target speed Vmax target, the maximum nominal torque Fmaxnom, a speed margin M and the speed of the vehicle V. La maximum torque limitation Cmax lim corresponds to a line dl, visible in FIG. 2, the slope of which makes it possible to join the curve C1 of maximum torque and the maximum target speed Vmax target to a value of zero resistive torque.

Indeed, it is assumed that the maximum advancing torque is zero at the maximum target speed in order to have a maximum torque always lower than the resistive torque.

In order to limit the speed of the vehicle on a steep downward slope, the straight line dl extends to the curve C2 of minimum torque, delimiting a zone Z of deceleration, grayed out in FIG. 2. Thus, the maximum torque can decrease up to to the minimum available torque.

In a third step 106, it is checked whether the conditions required to trigger the torque limitation are satisfied. To this end, the target maximum speed Vmax target is subtracted with a predetermined speed margin M to obtain a second target maximum speed value Vmax_cible2 and a comparison is made between said second target maximum speed Vmax_cible2 with the speed of the vehicle V.

If the vehicle speed V is greater than or equal to the second target maximum speed Vmax_cible2, the conditions required to trigger the torque limitation are satisfied. Thus, the torque limitation is only activated when the vehicle speed approaches the maximum target speed.

In a fourth step 108, a final torque limitation value CmaxlimF is calculated and it is transmitted to the general computer 34.

To this end, a first minimum value Min_C equal to Min (Cmaxlim; SI) is determined between the maximum torque limitation value Cmax lim and a threshold value SI, and a maximum value Max_C equal to Max (Min (Cmax_lim; SI); Cmin) between said first minimum value Min_C and the minimum nominal torque value Cmin.

A final value Cmax lim F of maximum torque is then determined, limiting the conductor corresponding to the minimum value between the maximum value Max_C and the maximum value of nominal torque Cmax.

The exemplary embodiments illustrated relate to a hybrid propulsion vehicle comprising two actuators. However, one could provide a motor vehicle with electric propulsion comprising two actuators or a motor vehicle comprising a heat engine as the only actuator.

The overspeed protection system and method according to the invention can therefore be generalized to one actuator or two actuators.

Thanks to the invention, all of the torque producing actuators in a motor vehicle are protected from overspeed, regardless of their location in the vehicle.

Claims (10)

1. Method (100) for protecting against overspeed of at least two torque actuators (12, 14) of a motor vehicle, in which a target maximum speed value (target Vmax) of the vehicle is calculated according to the speed maximum (Njnax) the most limiting of the speeds of the two actuators (12, 14). 2. Method according to claim 1, in which a maximum torque limitation value (Cmaxlim) is calculated as a function of the maximum target speed (target Vmax), of the nominal maximum torque (Fmaxnom), of a margin (M) of vehicle speed and speed (V). 3. Method according to claim 1 or 2, in which it is checked whether the conditions required to trigger the torque limitation are satisfied, for this purpose, the target maximum speed (Vmax target) is subtracted with a predetermined speed margin (M) to obtain a second target maximum speed value (Vmax_cible2) and a comparison between said second target maximum speed (Vmax_cible2) with the vehicle speed (V), if the vehicle speed (V) is greater than or equal to the second maximum speed target (Vmax_cible2), the conditions required to trigger the torque limitation are satisfied. 4. Method according to claims 2 and 3, in which a final torque limitation value is calculated (CmaxlimF) and it is transmitted to the general computer (34), to calculate said final torque limitation value (CmaxlimF), and a first minimum value (Min_C) between the maximum torque limitation value (Cmax lim) and a threshold value (SI) is determined, a first maximum value (Max_C) is determined between said first minimum value (Min_C) and the minimum value of nominal torque (Cmin), said final torque limitation value (CmaxlimF) corresponding to a second minimum value between the first maximum value (Max_C) and the maximum nominal torque value (Cmax). 5. System (40) for protection against overspeed of at least two torque actuators (12, 14) of a motor vehicle, comprising a module (42) for calculating a target maximum speed value (target Vmax) of the vehicle as a function of the maximum speed (N_max) the most limiting of the speeds of the two actuators (12, 14). 6. The system as claimed in claim 5, comprising a module (50) for calculating a maximum torque limitation value (Cmaxlim) as a function of the maximum target speed (Vmax target), of the nominal maximum torque (Fmaxnom), d '' a margin (M) of speed and vehicle speed (V). 7. The system as claimed in claim 5 or 6, comprising a module (60) for verifying the conditions required to trigger the torque limitation comprising a first subtractor (62) delivering a target maximum speed value (Vmax_cible2) corresponding to the subtraction between the target maximum speed (target Vmax) and a predetermined speed margin (M) and a comparator (64) between said second target maximum speed (Vmax_target2) and the vehicle speed (V), the required conditions being satisfied when the vehicle speed (V) is greater than or equal to the second maximum target speed (Vmax_cible2). 8. System according to claims 6 and 7, comprising a module (70) triggering the torque limitation when the required conditions are satisfied, said module (70) comprising a first module (72) determining a first minimum value (Min_C) between the maximum torque limitation value (Cmax lim) and a threshold value (SI), a second module (74) determining a maximum value (Max_C) between said first minimum value (Min_C) and the minimum nominal torque value (Cmin), said module (70) further comprising a third module (76) determining a final value (CmaxlimF) of maximum torque limiting the conductor corresponding to the minimum value between the maximum value (Max_C) and the maximum value of nominal torque (Cmax). 9. Motor vehicle with hybrid propulsion comprising a system (40) for protection against the overspeed of the two torque actuators (12, 14) according to any one of claims 5 to 8, in which the first torque actuator is a source of energy and the second torque actuator is a source of electrical energy. 5 10. Electrically propelled motor vehicle comprising a system (40) for protection against the overspeed of the two torque actuators (12, 14) according to any one of claims 5 to 8, in which the two torque actuators are sources of 'electric energy.