FR2886264A1 - Brake indicator for motor vehicle, has logic controller for calculating adhesion coefficient of wheels with respect to ground to determine usable breaking potential, and display device for displaying usable breaking potential - Google Patents

Abstract

The indicator has an estimation unit (22) comprising a sensor (32) for determining the longitudinal effort exerted on a disk (28) integrated to the wheels, and a sensor (34) for determining the vertical effort exerted on the wheels. A logic controller (30) calculates the adhesion coefficient of wheels with respect to the ground based on a ratio between the efforts to determine a usable breaking potential of a vehicle. A display device (10) displays the updated braking information, which comprises the usable breaking potential. An independent claim is also included for a motor vehicle equipped with a propulsion engine and a braking device comprising a brake indicator.

Description

The present invention relates to a clean brake indicator to provide

  updated braking information relating to a motor vehicle.

  In particular, the invention relates to a brake indicator comprising a display device adapted to display said updated brake information and adapted to be mounted in a motor vehicle equipped with a propulsion engine and a braking device.

  It is desirable to give the driver of a motor vehicle braking information to enable him to better adapt his actions to the brake controls according to the state of the road and the state of operation of the motor vehicle.

  Indeed, the braking distance of the vehicle depends on variable parameters such as the state of the road and the quality of tires and dampers.

  According to an analysis of the behavior of the drivers when braking, it appears that they do not press hard enough on the brake pedal during emergency braking. However, it has been found that a driver who does not sufficiently press on his brake pedal can easily lose several tens of meters of stopping distance during his braking.

  To alleviate this problem of dosage of braking adapted to the emergency situation or not, it is desirable to develop a brake assist system which indicates to the driver the maximum braking potential of the vehicle according to the road conditions and which allows to visualize the actual behavior of the vehicle during braking.

  The object of the invention is therefore to solve this problem.

  For this purpose, the subject of the invention is a braking indicator of the aforementioned type, characterized in that it furthermore comprises means for estimating a coefficient of grip of the wheels on the ground in order to determine a braking potential. of the vehicle and that said updated brake information includes the usable braking potential.

  According to particular embodiments, the brake indicator comprises one or more of the following characteristics: the braking device comprises at least one lining element integral with the vehicle and capable of applying a pressing force on a receiving element secured to the wheel for braking its rotation, and the coefficient of adhesion estimation means comprise: - means for controlling the application of the pressure on the receiving element by the lining element; means for determining the longitudinal force exerted by the lining element on the receiving element; means for determining the vertical force exerted by the wheels on the ground; and means for calculating the coefficient of adhesion as a function of the ratio between the determined longitudinal force and the determined vertical force; the means for estimating the coefficient of adhesion comprise: means for acquiring the outside temperature; means for acquiring the external moisture; and cartography means capable of determining the coefficient of adhesion by a predetermined correspondence law as a function of the external temperature and the external humidity; the means for estimating the coefficient of adhesion comprise means of connection to a vehicle steering device capable of calculating the coefficient of adhesion as a function of the instantaneous speed of the vehicle, of the instantaneous position of the steering member; and instantaneous steering power; the means for estimating the coefficient of adhesion comprise instrumented bearings which are capable of measuring the vertical and longitudinal forces; it comprises means for evaluating the braking rate used, and said updated braking information includes the braking rate used; it furthermore comprises means for determining the braking rate sought by the driver, comprising means for acquiring the force exerted by the driver on a brake actuating element of the braking device, and the updated braking information comprising the desired braking rate; it comprises a buzzer adapted to produce an audible signal when the desired braking rate is greater than the usable braking potential; the display device comprises a single linear or circular graduated screen capable of simultaneously displaying the usable braking potential, the braking rate used and the desired braking rate according to a preset color code; the screen makes it possible to display, in addition, information on the engine speed and / or the speed of the vehicle simultaneously or on demand; - The display device is a light indicator for displaying different colors and at different frequencies; and the display device comprises a memory for temporarily storing said updated brake information and the display device is adapted to display said updated braking information after a predefined delay time.

  The invention also relates to a motor vehicle equipped with a propulsion engine and a braking device, characterized in that it comprises a braking indicator as mentioned above.

  The invention will be better understood on reading the description which will follow, given solely by way of example and with reference to the appended drawings, in which: FIG. 1 is a diagrammatic view of a first embodiment embodiment of a braking indicator according to the invention, connected to an information transmission network of a motor vehicle; FIG. 2 is a diagrammatic graph illustrating an example of the temporal evolution of the pressure exerted on an element of a braking device of the motor vehicle; FIG. 3 is a diagrammatic graph illustrating the temporal evolution of a vertical force and of a longitudinal force on a rear wheel during braking as illustrated in the graph of FIG. - Fig.4 is a schematic view of a linear display screen of the brake indicator according to the invention in dry soil conditions and without braking of the motor vehicle; - Fig.5 is a schematic view similar to the view of Fig.4 when the soil is dry and during normal braking; - Fig.6 is a view similar to the view of Fig.4 when the soil is dry and during a braking supported; - Fig.7 is a view similar to the view of Fig.4 when the ground is icy and without braking; - Fig.8 is a view similar to the view of Fig.4 when the ground is icy and during a braking supported; - Fig.9 is a schematic view of a circular display screen of the brake indicator according to the invention; and Fig. 10 is a schematic view of a second embodiment of the brake indicator according to the invention.

  The braking indicator 2 according to the invention is illustrated schematically in FIG. It is capable of providing updated braking information relating to a motor vehicle equipped, in particular, with a heat engine (not shown), a braking device 4 and an information transmission network 6, for example a network. CAN network type.

  The braking indicator 2 comprises means 8 for determining braking information and a display device 10 for this information connected to the network 6 for transmitting and respectively receiving the braking information.

  The means 8 for determining braking information comprise means 12 for evaluating the braking rate used during braking, means 14 for determining the braking rate sought by the driver during braking and means 16. determining the usable braking potential of the motor vehicle.

  The evaluation means 12 comprise, for example, a sensor 18 for measuring the angular position of the wheels of the vehicle and a calculator 20 able to calculate the second derivative with respect to the time of the distance traveled obtained from the angular position measured by the sensor 18.

  The determination means 14 comprise for example a sensor for measuring the force exerted by the driver of the vehicle on the brake pedal. This force measurement is proportional to the braking rate sought by the driver of the vehicle.

  The determination means 16 are suitable for determining the usable braking potential as a function of a coefficient of adhesion of the vehicle relative to the ground.

  For this purpose, the means 16 for determining the usable braking potential comprise means 22 for estimating the coefficient of adhesion of the wheels on the ground and a predetermined correspondence law 23 depending on the type of the vehicle, during a period of time. learning phase.

  According to the first embodiment of the invention, the estimation means 22 are able to calculate the coefficient of adhesion as a function of information measured from the braking device 4.

  According to the exemplary embodiment illustrated in FIG. 1, the braking device 4 is of the disc brake type mounted, for example, on a rear wheel of the vehicle.

  It comprises a computer 24 adapted to control a stirrup 26 integral with the vehicle structure and adapted to apply a pressure force on a disk 28, integral with the vehicle wheel, to slow its rotation.

  The computer 24 is connected to the network 6 and belongs for example to an electronic assistance device to the dynamic behavior of the vehicle, generally called ESP device.

  According to this embodiment of the invention, the means for estimating the coefficient of adhesion comprise a computer connected to a sensor 32 for measuring a longitudinal force F, and a sensor 34 for measuring a force F. The sensor 32 is adapted to measure the pressure exerted by the stirrup 26 on the disc 28. This pressure, representative of the longitudinal force F ,, is proportional, on the one hand to the coefficient of adhesion between the wheels and the ground and, on the other hand, the weight exerted on each wheel during taxiing.

  The sensor 34 is able to measure the vertical force F or in other words the weight exerted on each wheel of the vehicle, corrected mass transfer during braking.

  The computer 30 is also connected to the network 6 for transmitting brake commands to the computer 24 of the braking device 4.

  After transmission of such a braking command and application of a braking torque on the rear wheel of the vehicle, the computer 30 is adapted to receive values of longitudinal force F1 and vertical force F measured by the sensors 32 and 34 and to calculate the ratio between the longitudinal force F, and the vertical force F ,,, to obtain a value of the coefficient of adhesion between the wheels of the vehicle and the ground.

  According to the invention, the vertical force F and the longitudinal force F1 are suitable for being measured at the same time T1 just before the wheel locking limit.

  For example, when the stirrup 26 applies a pressure, represented by the curve 36 in FIG. 3, on the disc 28 of the rear wheel of the vehicle, the longitudinal force F1, represented by the curve 38 in FIG. , increases proportionally up to a level corresponding to the locking of the wheel. After the beginning of the locking of the wheel, the pressure in the brakes is clean to be stopped to allow to restart the wheel (role of ABS anti-lock system).

  The vertical force F ,,, represented by the curve 40 in FIG. 3 decreases on the contrary because of the mass transfer from one wheel to the other. The reduction of the vertical force F is all the more important as the adhesion is important.

  The display device 10 of the braking information, for example mounted on the dashboard of the vehicle, is connected to the network 6 to receive the information of usable braking potential, desired braking rate and braking rate used during the test. braking.

  It comprises a buffer memory 42, a buzzer 44 and / or a linear or circular display 46, for example of the LCD screen type.

  The buffer memory 42 is able to temporarily store the updated braking information sent by the estimation means 12, 14, 16 via the network 6 and to display this information with a predefined delay time, for example from 2 to 10 seconds.

  Advantageously, this delay time is determined so as to create a phenomenon of remanence, or drag, of the display to allow the driver to view the display just after braking and not only during braking.

  The horn, for example a loudspeaker 44, is capable of triggering an audible signal when the braking rate sought by the driver is greater than the usable braking potential.

  The screen 46 is able to simultaneously display the usable braking potential, the braking rate used and the braking rate desired by the driver but not achieved because it exceeds the usable braking potential.

  The screen 46 as shown in FIGS. 4 to 8, includes a graduated linear marking from 0 to 10 in which the value 2 represents a low deceleration and the value 10 represents a strong deceleration.

  To display each of these braking information, the display device 10 uses three different colors.

  FIGS. 4 to 8 illustrate examples of display of the screen 46 depending on the running conditions of the vehicle and the type of braking exerted by the driver.

  As can be seen in FIG. 4, in a situation on dry ground without braking, a usable braking potential corresponding to a value of 10 ms-2 is evidenced by a coloration according to a first color, for example a green color, d a section 47 of the screen 46 starting from 0 and extending to the value 10.

  As can be seen in FIG. 5, during a situation on dry ground with normal braking, the screen 46 displays the usable braking potential in the first color, in a section 49 graduated from 3 to 10, the braking used in a second color, such as for example orange, in a section 51 graduated from 0 to 3.

  As can be seen in FIG. 6, during a situation on the dry ground with sustained braking, the screen 46 displays the usable braking potential in the first color, in a section 53 graduated from 7.5 to 10 and the braking rate used in the second color, in a section 55 graduated from 0 to 7.5.

  As shown in Fig.7, in a situation on icy ground without braking, the screen 46 displays a braking potential usable in the first color in a section 57 graduated from 0 to 3.

  As can be seen in FIG. 8, during a situation of icy ground with sustained braking, the screen 46 displays the braking rate used in section 57 graduated from 0 to 3 in the second color and the braking re-sought but not effective because of the low adhesion of the vehicle on the ground, in a third color, for example in red, in a section 59 graduated from 3 to 6.5. The red color display can moreover and advantageously blink at a determined frequency, which frequency can increase depending on the rate of exceedance of the maximum potential braking indicator available and therefore the lack of deceleration. This information goes well beyond a simple information type ABS indicator Alternatively, the indicator is a single indicator capable of changing colors and blinking at several frequencies and coupled or not with a buzzer.

  In a variant, the screen 46 is circular, as can be seen in FIG. 9.

  As a variant, the screen 46 also comprises a digital indication which indicates the value of exceeding the desired braking rate with respect to the braking rate used.

  Alternatively, the display device 10 is able to display simultaneously or on demand, information relating to the engine speed and the vehicle speed during the acceleration thereof and the braking information during the deceleration of the vehicle. vehicle.

  In the case of a simultaneous display, the display of the engine speed and of the braking is of different or highlighted color depending on whether the braking indication is favored over that of the engine speed or vice versa, in particular for the variant with a screen. circular then serving as a dial.

  In this last variant, the display device 10 can be confused with the speedometer or the lap counter or another display already usually present on the dashboard. This variant offers the advantage of presenting the braking information with the same visibility as vehicle speed information; braking information which should be a priority for safety, being generally visually undersized with respect to speed information or nonexistent.

  According to a second embodiment of the invention, shown in FIG. 10, the braking indicator 2 is identical to the indicator shown in FIG. 1 with the exception of the determining means 16 which comprise an external temperature sensor 60, a sensor 62 for measuring the external humidity and Mapping means 64.

  The mapping means 64 are adapted to receive the outside temperature and the external humidity measured by the sensors 60 and 62 and to determine the coefficient of adhesion by a predetermined correspondence law during a calibration phase.

  Alternatively, the outside temperature and outdoor humidity information comes from another vehicle equipment such as for example an air conditioning module, automatic defrost or wiping windows. In this case, the mapping means 64 are connected to the network 6 to receive the outdoor temperature and external humidity information of the air conditioning module or defrost.

  According to a third embodiment of the invention not shown, the means 16 for determining the coefficient of adhesion comprise an adhesion sensor.

  According to a fourth embodiment of the invention not shown, the vehicle steering device is able to calculate the coefficient of adhesion in a manner known per se and according to the instantaneous speed of the vehicle, the instantaneous position of the steering member and the instantaneous power generated by a motor to steer the wheels of the vehicle. In this case, the adhesion coefficient determination means comprise network connection means 6 for receiving the adhesion coefficient information.

  According to one variant, the adhesion is determined from an adhesion estimator present in the servo-control loop of the electrical assistance direction (DAE) as described in the patent FR2826452.

  According to another embodiment, the maximum deceleration obtained during the ABS regulation is calculated.

  According to another embodiment, a very weak ESP control is performed on a rear wheel during a low speed turn to detect the wheel lock and knowing the braking pressure, deduction is deduced therefrom.

  This very low regulation is transparent to the driver.

  According to another embodiment, instrumented bearings are used which are capable of measuring the vertical and longitudinal forces. The ratio between the two values measured on the same wheel, at the wheel lock limit, gives the soil / wheel adhesion directly according to the calculation method previously described for the ESP with the sensors 32 and 34.

  In a variant, the vehicle braking device is of the drum brake type. It comprises a lining element constituted by jaws and a drum for receiving this pressure secured to the wheel.

  As a variant, the brake indicator comprises means for estimating the coefficient of adhesion suitable for calculating a coefficient of adhesion from different information such as the information measured by the braking device, the information from a sensor temperature and humidity and information from the vehicle steering device.

  In this case, the different measured information is used to refine the determination of the coefficient of adhesion and the resulting usable braking potential.

  Advantageously, this measurement exploits all the information that is available on the vehicle and which combined with each other optimizes the knowledge of the maximum braking potential of the vehicle in all circumstances and therefore the effectiveness of braking in an emergency situation.

  The advantages of a braking indicator according to the invention are multiple: Use of means already available on the vehicle: ABS, ESP, DAE, rain sensor, thermometer, etc.

  informing the driver of the use and the potential of braking and thus gaining safety by acting on the behavior of the driver during emergency braking; coaching training; very low cost in the case of using an existing display in the handset; etc. 25

Claims (13)

  1. Brake indicator (2) for a motor vehicle equipped with a propulsion motor and a braking device (4), which indicator comprises a display device (10, 42, 44, 46) capable of displaying updated braking information, characterized in that it further comprises estimation means (16, 22, 23, 30, 32, 34, 60, 62, 64) of a coefficient of grip of the wheels on the ground for determining a usable braking potential of the vehicle and in that said updated braking information includes the usable braking potential.   2. Indicator according to claim 1, characterized in that the braking device (4) comprises at least one lining element (26) integral with the vehicle and adapted to apply a pressure force on a receiving member (28) integral with the wheel for braking its rotation, and in that the estimation means (16, 22, 23, 30, 32, 34, 60, 62, 64) of the coefficient of adhesion comprise: - control means (30) applying pressure on the receiving member (28) by the packing member (26); - means (32) for determining the longitudinal force (FI) exerted by the lining element (26) on the receiving element (28); means (34) for determining the vertical force (Fv) exerted by the wheels on the ground; and means (30) for calculating the coefficient of adhesion as a function of the ratio between the determined longitudinal force (F1) and the determined vertical force (Fv).   3. Indicator according to claim 1, characterized in that the means (16, 22, 23, 30, 32, 34, 60, 62, 64) for estimating the coefficient of adhesion comprise: - means (60) of acquisition of the outside temperature; means (62) for acquiring the external humidity; and mapping means (64) for determining the coefficient of adhesion by a predetermined correspondence law as a function of the outside temperature and the external humidity.   4. Indicator according to claim 1, characterized in that the estimation means (16, 22, 23, 30, 32, 34, 60, 62, 64) of the coefficient of adhesion comprise means of connection to a device of vehicle steering capable of calculating the coefficient of adhesion according to the instantaneous speed of the vehicle, the instantaneous position of the steering member and the instantaneous steering power.   5. Indicator according to claim 1, characterized in that the estimation means (16, 22, 23, 30, 32, 34, 60, 62, 64) of the coefficient of adhesion comprise instrumented bearings which are capable of measuring vertical and longitudinal forces 6. Indicator according to any one of the preceding claims, characterized in that it comprises means (12, 18, 20) for evaluating the braking rate used, and in that said updated braking information comprises the rate braking used.   7. Indicator according to any one of the preceding claims, characterized in that it further comprises means (14) for determining the desired braking rate by the driver comprising means for acquiring the force exerted by the driver on a braking actuating element of the braking device (4) and in that said updated braking information comprises the desired braking rate.   8. Indicator according to claim 7, characterized in that it comprises a horn (44) adapted to produce an audible signal when the desired braking rate is greater than the usable braking potential.   9. Indicator according to the combination of claims 6 and 7, characterized in that the display device (10, 42, 44, 46) comprises a single screen (46) linear or circular graduated and adapted to simultaneously display the braking potential usable, the braking rate used and the desired braking rate according to a preset color code.   10. Indicator according to claim 9, characterized in that the screen (46) makes it possible to display, in addition, information on the engine speed and / or the speed of the vehicle simultaneously or on demand.   11. Indicator according to any one of the preceding claims, characterized in that the display device (10, 42, 44, 46) is a light indicator allowing the display of different colors and at different frequencies.   12. Indicator according to any one of the preceding claims, characterized in that the display device (10, 42, 44, 46) comprises a memory (42) for temporarily storing said updated braking information and in that the device display (10, 42, 44, 46) is adapted to display said updated braking information after a predefined delay time.   Motor vehicle equipped with a propulsion engine and a braking device, characterized in that it comprises a braking indicator (2) according to any one of claims 1 to 12.