FR3005920A1 - METHOD AND DEVICE FOR MANAGING THE GEARBOX OF A MOTOR VEHICLE TAKING INTO ACCOUNT A MINIMUM ACCELERATION CRITERION - Google Patents

Abstract

The object of the invention is to propose a method for managing a gearbox of a motor vehicle equipped with regulation / speed limitation means. The method selects a gear ratio from a set of available gear ratios, which tracks a speed setpoint by providing a minimum level of acceleration required to maintain a predefined ride comfort. The invention also relates to a device that implements the method.

Description

FIELD OF THE INVENTION The present invention relates to a control method for a gearbox of a motor vehicle, as well as to a device, a gearbox and a gearbox. and a vehicle implementing such a method. Some vehicles include means for automatically controlling the speed of the vehicle, to follow a set speed set by the driver, or to avoid exceeding this speed.

For automatic gearboxes, it is known to use a management computer containing in memory speed shift laws. The computer receives various information on the driver's request, such as the position of the gas pedal. It also receives information on the operation of the vehicle, such as the speed of rotation of the engine. This information is used to determine the moments of changes in speed ratios. The laws of passage of gear ratios choose at all times the right gear ratio to optimize the operation of the engine, in order to obtain good conditions of performance, comfort and energy saving.

For manual gearboxes, such known calculators are used to indicate a gear change necessary to the driver, typically through a dashboard display element. The display then indicates a speed ratio determined by the computer, which according to the computer allows the vehicle to continue the speed instruction that the driver has fixed. When the driver applies the indicated change, he implements the velocity transition laws on which the calculator bases its decisions. A type of known transmission control method, presented in particular by the patent document US 6801845 B2, realizes an adaptation of the laws of passage of the speed ratios as a function of parameters outside the vehicle, such as, for example, variations in the slope of the vehicle. route taken, to optimize the choice of speed ratio. The laws of passage are typically developed empirically and require several calibration phases. When the speed of the vehicle is much lower than the speed reference, known computers will decide to stay on a short report even if for a need for acceleration or monitoring of the speed reference, it would be possible to use a report more high which would also be more economical and would generate increased driving comfort.

Patent document WO201301206 A1 describes a method which determines the acceleration necessary to maintain a set speed set by the driver of a motor vehicle. The acceleration is converted to the necessary torque, and a ratio capable of providing the necessary torque is chosen to control the gearbox of the vehicle in accordance with the choice made.

The object of the invention is to propose a method for managing a gearbox of a motor vehicle which aims to overcome at least one of the disadvantages present in the state of the art. A device capable of implementing the method is also targeted. In particular, the invention aims at providing a method which makes it possible to calculate a ratio of speeds based on quantities available within the vehicle, and which ensures a minimum driving comfort, while ensuring the follow-up of a fixed speed reference. by the driver using speed limitation / control means. The subject of the invention is a method for managing a gearbox of a motor vehicle equipped with regulation / speed limitation means. The method comprises the steps of providing an acceleration value ad requested by the speed control / limitation means at a ratio management means; provision of a maximum threshold value of acceleration amax; ^ ^ calculating a set acceleration ac and a torque Cc corresponding to the setpoint acceleration; selecting a gear ratio from the available gear ratios, the selected gear being best suited to provide said gear. The method is remarkable in that the set acceleration ac is equal to the requested acceleration value ad if it is lower than the maximum threshold value amax, and in that the set acceleration ac is equal to the maximum threshold value amax otherwise.

Preferably, the ratio selected during the selection step is displayed using display means. The display means preferably comprises a display element such as a screen integrated in the control panel of the vehicle, which is configured to display data from the method.

The calculation of the maximum threshold value of acceleration amax may preferably comprise the following steps: estimation of the resistant forces that apply to the vehicle; calculating a maximum acceleration value a, relative to the gear ratio engaged; - provision of a minimum acceleration value amin; determination of the threshold value amax as the maximum between the acceleration values ar and amin. The estimation of the resistant forces is preferably based on the speed of the vehicle and the engine torque.

Preferably, the minimum acceleration value ami !, may be a function of the speed of the vehicle and a speed setpoint made available by the speed limiting / regulation means.

The invention also relates to a device for managing a gearbox of a motor vehicle equipped with regulation / speed limitation means. The device is able to implement the method according to the invention. It further comprises a memory and processor means. The processor means are remarkable in that they are configured to obtain a desired acceleration value ad by the regulation / speed limitation means; read a maximum threshold value of acceleration amax in the memory; calculating a set acceleration ac and a torque Cc corresponding to the setpoint acceleration; selecting a gear ratio from among the available gear ratios, the selected gear being best suited to provide said gear. The device is remarkable in that the acceleration of setpoint ac it calculates is equal to the requested acceleration value ad if it is lower than the maximum threshold value amax, and in that the set acceleration ac is equal to the maximum threshold value amax otherwise. Preferably, the device may comprise display means, and the processor means may be configured to display the gear ratio selected during the selection step, by means of said display means. The invention also relates to a manual gearbox for a motor vehicle. The gearbox is remarkable in that it comprises a management device according to the invention.

The gearbox may preferably include automated means for changing gears. It is then remarkable in that it comprises for carrying out these gear changes a management device according to the invention.

Finally, the invention also relates to a motor vehicle equipped with regulation / speed limitation means. The vehicle is remarkable in that it comprises a gearbox according to the invention. The use of the method according to the invention makes it possible to continuously know the gear ratio which allows the monitoring of a speed setpoint set by the driver of a vehicle. When the speed setpoint is increased, a minimum "comfort" acceleration is ensured, in order to guarantee a predefined driving comfort in terms of acceleration, while following the speed setpoint chosen by the driver. The minimum acceleration may depend on the speed difference between the speed reference and the instantaneous speed of the vehicle, for example. The method and the device that implements it finds a particular application on vehicles with manual gearbox. Existing systems can easily apply the method since the calculations are based primarily on physical engine power quantities, GMP, which are traditionally available, or readily available, in a vehicle computer system. Other features and advantages of the present invention will be better understood from the description and the drawings, of which: FIG. 1 is a diagram which shows the main steps of the method according to the invention, in one embodiment preferential. Figure 1 shows a succession of functions applied by the method according to the invention, to prepare a gear ratio change when the driving conditions require, to ensure the right choice of the final report among several possibilities.

The process begins by obtaining an acceleration value ad as requested by the speed limiting / regulating means of which the motor vehicle is equipped. Calculation methods known per se in the art are applied in order to obtain the acceleration value ad, which may depend on the speed set point set by the driver, the instantaneous speed of the vehicle, the driving conditions or the speed of the vehicle. other parameters.

The method determines in real time a maximum threshold value of acceleration amax. According to a preferred embodiment, the calculation of the maximum threshold value comprises the following steps. In a first step 21, the method uses the instantaneous value of the vehicle speed Vv, as well as the engine torque Cm to estimate the resistant forces which oppose the advance of the vehicle. The resistant forces are the sum of the aerodynamic forces, the forces of the slope and the rolling forces, Fres = Frouiement + Faerodynamique + Fpente- From the maximal torque Cmax of the powertrain, GMP, the vehicle, and the resistant forces, the method calculates 22 the maximum acceleration ar that the vehicle can provide on the gear engaged, without the intervention of a gearshift, ar = Cmax / MR + Fres / IVI M describing the mass of the vehicle and R the radius of the wheels of the vehicle. This step makes it possible to take into account in real time the driving conditions of the vehicle, including the external conditions of the vehicle.

During step 24, the method determines the maximum threshold value amax by taking the maximum between the values ar and ami, or friend designates a limit acceleration, below which the follow-up service of the speed setpoint set by the driver is no longer considered acceptable. This value may preferably depend on the speed of the vehicle and the difference between the speed reference and the speed of the vehicle. It can be determined by means of a table relating these deviations to the acceptable minimum acceleration values, the values of the table being determined empirically beforehand. When the GMP can provide a level of acceleration greater than comforting acceleration without changing gear, the process will take advantage of this possibility. In step 30, the set acceleration ac is determined by taking the minimum between the requested acceleration values ad and the threshold value amax. Thus the minimum acceptable acceleration to ensure driving comfort is taken into account when selecting the gear ratio. If the set acceleration ac is greater than the maximum acceleration ar on the gear engaged, tracking the set acceleration will cause a downshift to a lower gear.

The set acceleration ac is converted into a set torque that must be applied to the wheels of the vehicle in order to obtain the calculated acceleration. In step 40, this pair Cc serves to identify the gear ratio that has the best ability to provide the requested acceleration. The selection is done in an exemplary manner based on a table relating the torque values to be provided with gear ratios available from the vehicle gearbox. Note that the reports that can be engaged are selected beforehand according to different criteria, including the speed of rotation of the engine to not exceed certain limits.

According to an advantageous embodiment of the invention, the report thus selected is displayed by means of a display element, such as a screen forming part of the control panel of the vehicle. According to an alternative mode of the invention, the method proceeds to a gear ratio change to the ratio thus selected.

The method is preferably implemented by a known transmission management computer which includes in memory pass laws depending on different information on the driver's request and on the operation of the vehicle. The computer comprises processor means preferably programmable, which can be configured for the implementation of the method described, for example by loading software that implements the method. Such a device is connected to various vehicle sensors known per se in the art that provide GMP parameters in real time, including vehicle speed, resistant forces opposing vehicle movement, and torque provided. by the GMP to the vehicle wheels.

The processor means of the computer have read access on a memory element which comprises at least one table relating discrepancies between an instantaneous speed of the vehicle with acceptable minimum acceleration values. The memory element advantageously comprises a second table which relates torque values to be provided with gear ratios available from the vehicle gearbox.

The computer is preferably operatively connected to a screen that is part of the vehicle control panel, and configured so that the selected gear is displayed on a portion of that screen. Alternatively, the computer is operably connected to automated means for changing gear ratios. Preferably, the gear ratio management device is an integral part of the gearbox of a vehicle.

Claims (10)

REVENDICATIONS1. A method of managing a gearbox of a motor vehicle equipped with regulation / speed limitation means, the method comprising the steps of - providing an acceleration value ad requested by the regulation / limitation means speed at the level of report management means; (10) - provision of a maximum threshold value of acceleration amax; (20) - calculating a set acceleration ac and a torque Cc corresponding to the setpoint acceleration; (30) - selecting a gear ratio from among the available gear ratios, the selected gear being best suited to provide said torque; (40) characterized in that the set acceleration ac is equal to the requested acceleration value ad if it is lower than the maximum threshold value amax, and in that the set acceleration ac is equal to the maximum threshold value amax otherwise. 2. Method according to claim 1, characterized in that the selected report is displayed using display means. 3. Method according to any one of claims 1 or 2, characterized in that the calculation of the maximum threshold value of acceleration amax (20) comprises the following steps: - estimation of the resistant forces that apply to the vehicle; (21) - calculation of a maximum acceleration value a, relative to the gear ratio engaged; (22) - provision of a minimum acceleration value amin; (23) - determination of the threshold value amax as the maximum between the acceleration values a, and am / n (24). 4. Method according to claim 3, characterized in that the estimate ofefforts strength (21) is based on the vehicle speed and the engine torque. 5. Method according to any one of claims 3 or 4, characterized in that the minimum acceleration value ami, (23) is a function of the speed of the vehicle and a speed setpoint made available by the limiting means / speed regulation. 6. Device for managing a gearbox of a motor vehicle equipped with regulation / speed limitation means, the device being able to implement the method according to any one of claims 1 to 5, comprising a memory and processor means, and characterized in that the processor means are configured to - obtain a desired acceleration value ad by the regulation / speed limitation means; (10) - reading of a maximum threshold value of acceleration amax in the memory; (20) - calculating a set acceleration ac and a torque Cc corresponding to the setpoint acceleration; (30) - selecting a gear ratio from the available gear ratios, the selected gear being best suited to provide said torque; (40) and further characterized in that the set acceleration ac is equal to the requested acceleration value ad if it is less than the maximum threshold value amax, and in that the set acceleration ac is equal to the maximum threshold value ac otherwise. 7. Device according to claim 6, characterized in that the device comprises display means, and in that the processor means are configured to display the gear ratio selected with said display means. 8. Gearbox for a motor vehicle, characterized in that the gearbox comprises a management device according to any one of claims 6 or 7. 9. Gearbox for a motor vehicle, comprising automated means for changing speed ratio, characterized in that it comprises for performing these gear changes a management device according to any one of claims 6 or 7. 10. Motor vehicle equipped with regulation / speed limitation means, characterized in that the vehicle comprises a gearbox according to any one of claims 8 or 9.