Method and system for controlling a drive train of a motor vehicle

• US 6,311,115 B2
• Filed: 01/02/2001
• Issued: 10/30/2001
• Est. Priority Date: 07/02/1998
• Status: Expired due to Term

• Current Assignee: Vitesco Technologies GmbH (Continental AG)
• Original Assignee: Siemens AG
• Inventors: Lohrenz, Frank
• Primary Examiner(s): Camby, Richard M.
• Application Number:
  US09/752,932
• Publication Number:
  US 20010020207A1
• Time in Patent Office: 301 Days
• Field of Search: 701/57, 701/51, 701/54, 701/55, 701/56, 180/338, 180/197, 477/78, 477/135, 395/3, 395/900
• US Class Current: 701/57
• CPC Class Codes: B60W 2050/0057 Frequency analysis, spectral techniques or transforms
• CPC Class Codes: F16H 2061/0081 Fuzzy logic
• CPC Class Codes: F16H 2061/0096 using a parameter map
• CPC Class Codes: F16H 59/24 dependent on the throttle opening
• CPC Class Codes: F16H 59/48 Inputs being a function of acceleration
• CPC Class Codes: F16H 59/54 dependent on signals from the brakes, e.g. parking brakes
• 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

A gear ratio of an automatic transmission is set by a fuzzy logic circuit which evaluates a braking torque desired by a motor vehicle driver and which carries out a change in the transmission gear ratio in order to support the braking torque of a brake system. After changing the transmission gear ratio, the braking torque desired by the driver is again evaluated and, in accordance with the evaluation result, the transmission gear ratio is, if appropriate, again adjusted in view of the desired braking torque. A drive train control system is also provided.

Claims

1. A method for controlling a drive train of a motor vehicle, comprising:

automatically setting, by using stored maps, a transmission ratio of an automatic transmission at least as a function of a speed of a motor vehicle and as a function of one of a position of an accelerator pedal and a substitute variable for the position of the accelerator pedal;

evaluating, with a fuzzy logic circuit, signals characterizing a driving state of the motor vehicle and subsequently producing, with the fuzzy logic circuit, control signals for setting the transmission ratio;

assessing, with the fuzzy logic circuit, a braking torque desire of a driver of the motor vehicle only after a brake pedal has been actuated for a given period of time and changing the transmission ratio for assisting a braking torque of a brake system; and

assessing, with the fuzzy logic circuit, the braking torque desire of the driver again after changing the transmission ratio, and, if appropriate, adapting the transmission ratio again to the braking torque desire in accordance with an assessment result.

2. The method according to claim 1, which comprises, after adapting the transmission ratio again, assessing, with the fuzzy logic circuit, the braking torque desire of the driver again and changing the transmission ratio in steps until a demanded braking torque is achieved.

3. The method according to claim 1, which comprises:

determining the transmission ratio for assisting the braking torque with the fuzzy logic circuit in parallel with a map-based calculation of the transmission ratio; and

calculating, with the fuzzy logic circuit, a change in the transmission ratio by using an actual transmission ratio present in the automatic transmission.

4. The method according to claim 1, which comprises:

determining the transmission ratio for assisting the braking torque with the fuzzy logic circuit in parallel with a map-based calculation of the transmission ratio; and

setting, with the fuzzy logic circuit, the transmission ratio to a statically determined transmission ratio if the statically determined transmission ratio results in an increase of the transmission ratio.

5. The method according to claim 1, which comprises:

deriving driving state variables of the motor vehicle; and

calculating, with the fuzzy logic circuit, the braking torque desire of the driver from the driving state variables.

6. The method according to claim 1, which comprises:

generating a control signal with the fuzzy logic circuit;

using the control signal as a rotational speed threshold for a comparison with a rotational speed of a turbine of the automatic transmission; and

inducing a change in the transmission ratio for assisting the brake torque, if the rotational speed of the turbine falls below the rotational speed threshold.

7. The method according to claim 1, which comprises:

generating a control signal with the fuzzy logic circuit;

using the control signal as a rotational speed threshold for a comparison with an output rotational speed of the automatic transmission; and

inducing a change in the transmission ratio for assisting the brake torque, if the output rotational speed of the automatic transmission falls below the rotational speed threshold.

8. The method according to claim 1, which comprises maintaining the transmission ratio for assisting the braking torque until given exit conditions are met.

9. In combination with a brake system having a break pedal, a drive train control system for a motor vehicle, comprising:

a drive train controller for setting, based on stored map data, a transmission ratio as a function of at least a motor vehicle speed and as a function of one of an accelerator pedal position and a substitute variable for the accelerator pedal position;

said drive train controller including a fuzzy logic circuit,

a signal line connecting said fuzzy logic circuit to the brake system;

said fuzzy logic circuit evaluating vehicle driving state signals and vehicle load signals for generating control signals for setting the transmission ratio; and

said fuzzy logic circuit evaluating a braking torque desire of a driver, the braking torque desire being communicated by the brake system, and said fuzzy logic circuit performing a change in the transmission ratio for assisting a braking action of the brake system once the brake pedal has been actuated for a given period of time.