Method for controlling automatic transmission of a vehicle on a downhill slope

• US 20060149450A1
• Filed: 11/18/2003
• Published: 07/06/2006
• Est. Priority Date: 11/21/2002
• Status: Active Grant

• Current Assignee: Renault Sas (Renault)
• Original Assignee: Renault Sas (Renault)
• Inventors: Taffin, Christian
• Granted Patent: US 7,987,034 B2
• Time in Patent Office: Days
• US Class Current: 701/51
• CPC Class Codes: B60W 2720/10 Longitudinal speed
• CPC Class Codes: F16H 2059/186 Coasting
• CPC Class Codes: F16H 2059/663 Road slope
• CPC Class Codes: F16H 2061/0234 Adapting the ratios to special vehicle conditions
• CPC Class Codes: F16H 59/46 dependent on a comparison between speeds
• CPC Class Codes: F16H 59/66 Road conditions, e.g. slope, slippery
• CPC Class Codes: F16H 61/0213 characterised by the method for generating shift signals
• CPC Class Codes: F16H 61/21 Providing engine brake control

Abstract

The invention concerns a method for controlling automatic transmission (3) of a vehicle comprising an engine (2) driving the transmission (3) which consists in: detecting a downhill situation of the vehicle, and selecting a transmission ratio so that the engine absorbs energy, storing a longitudinal speed of downhill start (Vmin) when the vehicle starts going downhill, and while the vehicle is running downhill, comparing the current speed (V) of the vehicle with the downhill start speed (Vmin) such that the current speed (V) exceeds the downhill start speed (Vmin) by a predetermined difference (VS), then controlling the transmission to trigger downshifting.

Claims

1. A method for control of an automatic transmission (3) of a vehicle provided with an engine (2) that drives the transmission (3), in which method:

a downhill-travel situation of the vehicle is detected and;

a transmission ratio is chosen such that the engine (3) absorbs energy,

characterized in that a longitudinal speed (Vmin) at the beginning of downhill travel is stored in memory when the vehicle begins a downhill-travel situation and,

as long as the vehicle is in the downhill-travel situation, the current speed (V) of the vehicle is compared with the speed (Vmin) at the beginning of downhill travel in such a way that;

if the current speed (V) exceeds the speed (Vmin) at the beginning of downhill travel by a predetermined deviation (VS), the transmission is then instructed to initiate downshifting.

2. A control method according to claim 1, characterized in that the downhill-travel situation is detected if the slope (P) is greater than a predetermined threshold slope (PS), if the power demand (Acc) of the engine is smaller than a predetermined power threshold (AccS), and braking is absent.

3. A control method according to claim 1, characterized in that it includes an additional test step (28) verifying that, before downshifting is initiated, the energy-absorption capacity of the engine is smaller than a predetermined power threshold.

4. A control method according to claim 3, characterized in that the absorption capacity of the engine is determined by the engine speed (NTA).

5. A control method according to claim 3, characterized in that the threshold (NS) of power absorption capacity is an increasing function of the slope (P).

6. A control method according to claim 1, characterized in that the deviation (VS) from predetermined speed is between 5 and 10 km/h.

7. A control method according to claim 1, characterized in that the vehicle is equipped with a speed-governing system.

8. A system for control of an automatic transmission (3) of a vehicle provided with an engine (2) that drives the transmission (3), the system being provided with:

means for identifying a downhill-travel situation of the vehicle, and

means for choosing a transmission ratio so that the engine absorbs energy,

characterized in that it is additionally provided with;

means for measuring and storing in memory the longitudinal speed (Vmin) when the vehicle begins a downhill-travel situation,

means for comparing the current speed (V) of the vehicle with the speed (Vmin) at the beginning of downhill travel, and;

means for instructing the transmission to initiate downshifting if the current speed (V) exceeds the speed (Vmin) at the beginning of downhill travel by a predetermined deviation (VS).

9. A vehicle provided with an engine and an automatic transmission, characterized in that it is provided with the system according to claim 8 for control of the automatic transmission.