Method to control a road vehicle provided with a servo-assisted transmission during a slowing-down phase

Patent metadata

Field	Value
Publication number	US-2021095759-A1
Application number	US-202017015359-A
Country	US
Kind code	A1
Filing date	Sep 9, 2020
Priority date	Sep 30, 2019
Publication date	Apr 1, 2021
Grant date	—

Abstract

A method to control a road vehicle provided with a servo-assisted transmission during a slowing down phase; the control method comprises, when the servo-assisted transmission is in an automatic operating mode, the steps of: calculating, assuming that a pressing of the brake pedal remains constant, an opening time interval needed to allow the road vehicle to reach an opening speed at which a clutch of the servo-assisted transmission is definitively opened; calculating a number of downshifts that can be carried out in the opening time interval based on a time needed to carry out a downshift; scheduling the downshifts to be carried out in order to get from the current gear engaged in the servo-assisted transmission to an opening gear with which the clutch of the servo-assisted transmission is definitively opened, so as to carry out no more than the number of downshifts that can be carried out in the opening time interval; and carrying out the scheduled downshifts.

First claim

1 ) A method to control a road vehicle ( 1 ) provided with a servo-assisted transmission ( 7 ) during a slowing down phase; the control method comprises, when the servo-assisted transmission ( 7 ) is in an automatic operating mode, the steps of:
detecting a current speed of the road vehicle ( 1 ); detecting a current gear engaged in the servo-assisted transmission ( 7 ); detecting a pressing of a brake pedal ( 23 ); calculating, assuming that the pressing of the brake pedal ( 23 ) remains constant, an opening time interval needed to allow the road vehicle ( 1 ) to reach an opening speed at which a clutch ( 16 ) of the servo-assisted transmission ( 7 ) is definitively opened; calculating a number of downshifts that can be carried out in the opening time interval based on a time needed to carry out a downshift; scheduling the downshifts to be carried out in order to get from the current gear engaged in the servo-assisted transmission ( 7 ) to an opening gear with which the clutch ( 16 ) of the servo-assisted transmission ( 7 ) is definitively opened, so as to carry out no more than the number of downshifts that can be carried out in the opening time interval; and carrying out the scheduled downshifts.

2 ) The control method according to claim 1 , wherein, if the number of downshifts that can be carried out in the opening time interval is smaller than the number of gears existing between the current gear engaged in the servo-assisted transmission ( 7 ) and the opening gear, the scheduling of the downshifts involves at least one multiple downshift.

3 ) The control method according to claim 2 , wherein a multiple downshift is always arranged first in the scheduling of the downshifts.

4 ) The control method according to claim 2 , wherein at least the last downshift of the scheduling of the downshifts is always a single downshift.

5 ) The control method according to claim 1 and comprising the further steps of:
cyclically detecting a pressing of the brake pedal ( 23 );
recalculating, in case of a change in the pressing of the brake pedal ( 23 ), the opening time instant;
recalculating, in case of a change in the pressing of the brake pedal ( 23 ), the number of downshifts that can be carried out in the opening time interval; and
rescheduling, in case of a change in the pressing of the brake pedal ( 23 ), the downshifts to be carried out in order to get from the current gear engaged in the servo-assisted transmission ( 7 ) to the opening gear.

6 ) The control method according to claim 1 , wherein:
the opening gear is a second gear (II); the road vehicle ( 1 ) is stopped with the clutch ( 16 ) open; and after the vehicle ( 1 ) has been stopped, a first gear (I) is engaged in the servo-assisted transmission ( 7 ).

7 ) The control method according to claim 1 , wherein the scheduling of the downshifts is carried out preventing the rotation speed (ω E ) of the internal combustion engine ( 4 ) from falling below a predetermined lower threshold.

8 ) The control method according to claim 1 and comprising the further steps of:
determining a longitudinal deceleration of the road vehicle ( 1 ); and
calculating the opening time interval based on the longitudinal deceleration of the road vehicle ( 1 ).

9 ) The control method according to claim 8 and comprising the further steps of:
measuring a rotation speed (ω 2 ) of a secondary shaft ( 17 ) of the servo-assisted transmission ( 7 ); and
calculating the longitudinal deceleration of the road vehicle ( 1 ) by calculating the time derivative of the rotation speed (ω 2 ) of the secondary shaft ( 17 ) of the servo-assisted transmission ( 7 ).

Assignees

• Ferrari Spa

Inventors

• Barone Alessandro
• Nannini Andrea
• Senserini Giacomo
• Marconi Stefano

Classifications

• B60W40/105

  Speed · CPC title

• B60W30/19 Primary

  Improvement of gear change, e.g. by synchronisation or smoothing gear shift · CPC title

• F16H59/48

  Inputs being a function of acceleration · CPC title

• F16H61/0213 Primary

  characterised by the method for generating shift signals · CPC title

• F16H2200/0056

  the gear ratios comprising seven forward speeds · CPC title