FR2934215A1 - Regenerative braking method for motor vehicle i.e. electric vehicle, involves applying regenerative braking action to vehicle using regenerative braking device, where intensity of braking action depends on speed of vehicle - Google Patents

Abstract

The method involves applying a regenerative braking action to a motor vehicle using a regenerative braking device, where intensity of the braking action depends on speed of the vehicle. The intensity increases with the speed of the vehicle over a speed interval ranging from a first speed threshold to a second speed threshold. The intensity is constant over another speed interval ranging from a third speed threshold to a fourth speed threshold. Independent claims are also included for the following: (1) a data medium comprising software units for implementing a regenerative braking method (2) a regenerative braking system of a motor vehicle, comprising a determination unit for determining speed of the vehicle.

Description

The present invention relates to a regenerative braking process of a motor vehicle or a regenerative braking process for a motor vehicle. It also relates to a data medium comprising software means for implementing such a method, a regenerative braking system for equipping a motor vehicle and a vehicle comprising such a regenerative braking system. The invention also relates to a method of operating a recuperative braking system for implementing the regenerative braking method according to the invention.

It is known to equip motor vehicles, in particular electric or hybrid motor vehicles, with two braking systems: a first dissipative braking system and a second regenerative braking system. The dissipative braking system makes it possible to convert the kinetic energy of the motor vehicle into dissipated energy, for example in the form of heat at discs and / or braking drums.

The regenerative braking system makes it possible, for its part, to convert the kinetic energy of the motor vehicle into energy, for example electric or mechanical, which can be stored at the level of the vehicle and then reused later, in particular to accelerate the vehicle.

The management of the use of these two braking systems is complex.

It is indeed difficult to provide two organs respectively dedicated to the control of the dissipative braking system and the control of the regenerative braking system. MS \ REN097EN.dpt Also, it is common to provide a control member dedicated to the only dissipative braking system to maintain a use that is intuitive for the driver of the vehicle. As a result, it is known to control the regenerative braking system by means of a vehicle acceleration pedal. In particular, it is known to activate the regenerative braking system when the driver releases the accelerator pedal of the vehicle.

In order to improve the driveability of a vehicle comprising the two braking systems mentioned above and the relevance of the braking action exerted by the regenerative braking system, it is still known from document FR 2 749 229. to control the braking force produced by the regenerative braking system according to the speed of the foot reading of the accelerator pedal.

However, in deceleration and / or braking phases, the driving pleasure of the vehicles mentioned above is not optimal. Similarly, the intensity of the braking action due to the regenerative braking system is not always optimal.

The object of the present invention is to provide a regenerative braking method obviating the drawbacks previously identified and making it possible to improve the recuperative braking methods known from the prior art. In particular, the invention proposes a braking method improving the use of regenerative braking both in terms of energy level recovered, as well as feeling and approval for the occupants of the vehicle.

According to a first aspect of the invention, the recuperative braking method of a motor vehicle is characterized in that the intensity of the regenerative braking action of the motor vehicle depends on the speed of the motor vehicle. MS \ REN097EN.dpt The intensity of the braking action can increase with the speed of the vehicle on a first speed interval extending from a first speed threshold to a second speed threshold. The intensity of the braking action may be at least substantially constant over a second speed range extending from a third speed threshold to a fourth speed threshold. The intensity of the braking action may decrease with the vehicle speed over a third speed range extending from a fifth speed threshold to a sixth speed threshold. The intensity of the braking action may be at least substantially constant over a fourth velocity range extending beyond a seventh speed threshold. The regenerative braking action can be applied progressively, the speed of application of the braking action depending on the speed of the motor vehicle. According to a second aspect of the invention, the recuperative braking method of a motor vehicle is characterized in that the regenerative braking action is applied progressively, the speed of application of the braking action depending on the speed. of the motor vehicle. A data carrier according to the invention comprises software means for implementing the braking method defined above. According to the invention, a regenerative braking system of a motor vehicle is characterized in that it comprises hardware and / or software means for implementing the braking method defined above.

MS \ REN097EN.dpt5 The regenerative braking system may comprise a computer, a vehicle speed determination means, a regenerative braking device and a control device of the energy recovery braking device. A motor vehicle according to the invention comprises a regenerative braking system defined above.

The appended drawing shows, by way of example, embodiments of the two regenerative braking methods according to the invention and an embodiment of a braking system according to the invention.

Figure 1 is a diagram of an embodiment of a regenerative braking system of a motor vehicle. FIG. 2 is a diagram of an embodiment of the first regenerative braking method according to the invention.

FIG. 3 is a graphical representation illustrating the principle of the first regenerative braking method according to the invention.

FIG. 4 is a diagram of an embodiment of the second regenerative braking method according to the invention.

FIG. 5 is a graphical representation illustrating the principle of the second regenerative braking method according to the invention.

The regenerative braking system shown in Figure 1 is intended to equip a motor vehicle. It mainly comprises a computer 2, a control device 3, a means 4 for determining the speed of the vehicle (longitudinal speed) and a regenerative braking device 5.

The means 4 for determining the speed of the vehicle may for example comprise a speed sensor or a means for estimating this speed. The determining means generates a vehicle speed signal which is transmitted to the computer.

The control device makes it possible to control the recuperative braking device 5 via the computer. It generates a signal, for example an activation or deactivation signal of the regenerative braking device which is transmitted to the computer. The control device can include a vehicle acceleration control member such as an accelerator pedal. In this case, the device can transmit an activation signal of the braking device when the driver causes a reading of the accelerator pedal and / or when the driver removes the foot of the accelerator pedal. Conversely, the device may transmit a signal for deactivation of the braking device when the driver causes a depression of the accelerator pedal and / or when the driver puts his foot on the accelerator pedal.

On the basis of the signals transmitted to the computer 2, the latter develops, using hardware and / or software contained in the computer, a control signal of the regenerative braking device. This control signal comprises an intensity command of the braking action to be implemented by the regenerative braking device. Thus, the computer comprises hardware and / or software means for implementing the regenerative braking method according to the invention and, therefore, hardware and / or software means for implementing the method of operation of the regenerative braking system according to the invention. the invention. The calculator comprises calculation means for calculating an intensity reference value of MS \ REN097FR.dpt the braking action to be implemented by the regenerative braking device as a function of the speed value of the motor vehicle when the device regenerative braking is activated.

These means may include computer programs.

Preferably, the regenerative braking device comprises an electric machine operating as an electric generator for charging batteries. However, the device may include any other technology for converting the kinetic energy of the vehicle into a second energy that can be stored and reused later, for example to set in motion and / or accelerate the vehicle.

An embodiment of the first braking method or an embodiment of the first method of operation of the regenerative braking system is described hereinafter with reference to FIG.

In a first test step 10, the presence of an activation signal of the regenerative braking device is tested. In the absence of an activation signal, step 10 is looped. If an activation signal is present, a step 20 is carried out.

In step 20, the speed of the motor vehicle is determined. For example, the signal transmitted by the speed determination means is analyzed for this purpose.

In a step 30, a braking action intensity setpoint value to be implemented by the recuperative braking device is calculated. This set value is for example an equivalent force value exerted on the vehicle against its displacement. Any other value of braking torque or braking power equivalent to this value MS \ REN097FR.dpt of braking force can be used as a set value to control the operation of the regenerative braking device. The calculation of the setpoint value is for example carried out as described below with reference to FIG. 3. From these setpoint values, a control signal of the recuperative braking device is generated.

In a step 40, the control signal is transmitted to the regenerative braking device which then operates in accordance with the set values contained in the control signal. Thus, in this operation, the intensity of the braking action is equal (or substantially equal) to the setpoint value. As a result, of such an embodiment of the braking process, the intensity of the regenerative braking action of the motor vehicle depends on the speed of the motor vehicle and a change in the speed of the vehicle causes all things to be equal. elsewhere, a change in the intensity of regenerative braking.

In a test step 50, the presence of a deactivation signal of the regenerative braking device is tested. In the absence of a deactivation signal, step 40 (or alternatively, in an execution variant on step 20) is looped. If a deactivation signal is present, a step 60 is started in which the regenerative braking device is deactivated.

In an exemplary embodiment particularly suitable for electric vehicles, the calculation of the braking intensity reference value of the regenerative braking device is implemented as described below with reference to FIG. 3. As a first approximation, in FIG. the hypothesis where the regenerative braking is the only braking (or the predominant braking) applying to a vehicle, to a value F of intensity of the braking action corresponds to a deceleration A of the vehicle of mass M according to the formula: F = MxA. MS \ REN097FR.dpt In a first vehicle speed interval comprised between a first threshold value v1 and a second threshold value v2, the reference value of the intensity F of the regenerative braking action increases with the speed of the vehicle between a first value F1 and a second value F2. Preferably, the reference value of the intensity F of the regenerative braking action evolves continuously between F1 and F2, for example linearly.

In a second vehicle speed interval comprised between a third threshold value v3 and a fourth threshold value v4, the setpoint value of the intensity F of the recuperative braking action remains substantially constant around a third value F3. Preferably, the reference value of the intensity F of the regenerative braking action changes continuously in this interval, for example linearly.

In a third vehicle speed interval between a fifth threshold value v5 and a sixth threshold value v6, the setpoint value of the intensity F of the regenerative braking action decreases with the speed of the vehicle between a fourth value F4 and a fifth value F5. Preferably, the reference value of the intensity F of the regenerative braking action changes continuously between F4 and F5, for example linearly.

In a fourth vehicle speed interval extending beyond a seventh threshold value v7, the setpoint value of the intensity F of the recuperative braking action remains substantially constant around a sixth value F6. Preferably, the reference value of the intensity F of the regenerative braking action changes continuously in this interval, for example linearly. MS \ REN097FR.dpt Preferably, F2 = F3 and / or F3 = F4 and / or F5 = F6 and / or v2 = v3 and / or v4 = v5 and / or v6 = v7.

The speed threshold v2 may be between 15 and 25 km / h and is preferably equal to 20 km / h.

The speed threshold v4 can be between 35 and 45 km / h and is preferably equal to 40 km / h.

The speed threshold v6 may be between 80 and 100 km / h and is preferably equal to 90 km / h.

The intensity F3 of the regenerative braking action may correspond to a deceleration of the vehicle of between 1.5 and 2 m / s 2 and preferably corresponds to a deceleration of 1.7 m / s 2.

The intensity F6 of the regenerative braking action may correspond to a deceleration of the vehicle of between 0.5 and 1 m / s 2 and preferably corresponds to a deceleration of 0.8 m / s 2. Preferably, the speed threshold v1 is 5 km / h and / or the summary braking device is deactivated when the speed of the vehicle is less than v1.

The regenerative braking method according to the invention has advantages over vehicles having a constant level of regenerative braking as a function of their speed. Indeed, the constant nature of the intensity of the action of the regenerative braking generates discomfort at high speed and causes a high energy consumption during re-acceleration. In addition, at low speed (use in the city), the constant nature of the intensity of regenerative braking does not optimize the amount of MS \ REN097FR.dpt20 recovered energy. Conversely, thanks to the invention, the regenerative braking is important at low speed (for example in urban traffic) to recover a maximum of energy. At high speed, the regenerative braking becomes weaker (for example in traffic on a national road) and thus makes it possible not to lose too much speed and not have to re-accelerate too much over a range of operation of the engine on which the efficiency of the engine. engine is weak.

The invention also relates to a second method of regenerative braking of a motor vehicle such that the regenerative braking action produced by the regenerative braking device is applied progressively, the speed of application of the braking action depending on the speed. of the motor vehicle. This second braking method may be applied independently of the first regenerative braking method described above or incorporated in the first regenerative braking method described above.

A recuperative braking system adapted to the implementation of this second regenerative braking method may be similar to that described above with reference to FIG. 1. Nevertheless, this regenerative braking system differs from that described above in that it comprises, in addition to or instead of the hardware and / or software resources contained in the computer, hardware and / or software means for implementing the essential steps of the second regenerative braking method. For this purpose, the computer comprises hardware and / or software means for calculating a time ramp for changing the set value of the intensity of the regenerative braking action to be exerted by the regenerative braking device just after an activation of this recuperative braking device. The hardware and / or software means may comprise computer programs. MS \ REN097EN.dpt An embodiment of the second braking method or an embodiment of the method of operation of the regenerative braking system is described below with reference to FIG. 4.

In a first test step 100, the presence of an activation signal of the recuperative braking device is tested. In the absence of an activation signal, it is looped on step 100. In case of presence of an activation signal, go to a step 110.

In step 110, the speed of the motor vehicle is determined. For example, the signal transmitted by the speed determination means is analyzed for this purpose.

In a step 120, a ramp of braking action intensity reference values to be implemented by the regenerative braking device is calculated just after a moment of activation of the regenerative braking device. The progressivity of the ramp of the setpoint values depends on the speed of the vehicle. This progressivity is such that the evolution of the ramp is more brutal for a first speed of the vehicle than for a second value of the vehicle greater than the first speed. Examples of ramp calculations of setpoint values are for example carried out as described below with reference to FIG. 5. From these ramps, a control signal of the device of the regenerative braking device is generated.

In a step 130, the control signal is transmitted to the regenerative braking device which then operates in accordance with the set values contained in the control signal. Thus, in this operation, the intensity of the braking action is equal (or substantially equal) to the setpoint value. MS \ REN097EN.dpt In an embodiment particularly suitable for electric vehicles, the calculation of the ramps of reference values of the braking intensity of the regenerative braking device is implemented as described below with reference to FIG. This figure describes the evolution of the value of the setpoint of the intensity of the regenerative braking action after an activation of the regenerative braking device at the time t = 0.05 s. A first curve in dashed lines reproduces a ramp of intensity reference values of the action of the regenerative braking device for a vehicle speed of 30 km / h. The setpoint reaches 100% of its value (for example the braking force intensity value corresponding to a deceleration of 1.7 m / s) at t = 0.12 s (ie 0.07 s after activation of the brake device).

A second curve in solid line reproduces a ramp of values of intensity of the action of the regenerative braking device for a vehicle speed of 80 km / h. The setpoint reaches 100% of its value (for example the braking force intensity value corresponding to a deceleration of 1 m / s) at t = 0.23 s (ie 0.18 s after activation of the device of brake).

This second method of braking has the following advantages: it guarantees a good level of comfort at high speed because there is no jerkiness by activating the regenerative braking, and it allows to increase the speed of reaction of the low speed braking (eg in heavy traffic).

The ramps are preferably continuous. They can be linear. They may also have a point of inflection and / or be continuous derivative.

Preferably, as previously seen, for example by means of a mapping, for all the vehicle speeds, the parameters MS \ REN097FR.dpt of intensity of the braking action, of the beginning of braking activation are defined. , time to achieve this braking intensity and stabilization of the action. MS \ REN097FR.dpt

Claims (11)

Claims: 1 A regenerative braking process of a motor vehicle, characterized in that the intensity of the regenerative braking action of the motor vehicle depends on the speed of the motor vehicle. Braking method according to claim 1, characterized in that the intensity of the braking action increases with the speed of the vehicle over a first speed range extending from a first speed threshold (v1) to a second speed threshold (v2). 3. A method of braking according to claim 1 or 2, characterized in that the intensity of the braking action is at least substantially constant over a second range of speeds ranging from a third speed threshold (v3) to a fourth speed threshold (v4). 4. Braking method according to one of the preceding claims, characterized in that the intensity of the braking action decreases with the speed of the vehicle on a third speed range extending from a fifth speed threshold (v5 ) at a sixth speed threshold (v6). Braking method according to one of the preceding claims, characterized in that the intensity of the braking action is at least substantially constant over a fourth speed range extending beyond a seventh speed threshold. (v7). 6. A method of braking according to one of the preceding claims, characterized in that the regenerative braking action is applied gradually, the speed of application of the braking action depending on the speed of the motor vehicle. 7. A method of regenerative braking of a motor vehicle, characterized in that the regenerative braking action is applied progressively, the speed of application of the braking action depending on the speed of the motor vehicle. 8. Support (2) data comprising software means for implementing the braking method according to one of the preceding claims. 9. System (1) for regenerative braking of a motor vehicle, characterized in that it comprises material means (2, 3, 4, 5) and / or software implementation of the braking method according to one Claims 1 to 7. 10. regenerative braking system according to claim 9, characterized in that it comprises a computer (2), a means (4) for determining the speed of the vehicle, a device (5) for regenerative braking energy and a device (3) for controlling the energy regenerative braking device (5). 11. A motor vehicle comprising a regenerative braking system according to claim 9 or 10. MS \ REN097EN.dpt