Integrated control of a lean burn engine and a continuously variable transmission

• US 5,846,157 A
• Filed: 10/25/1996
• Issued: 12/08/1998
• Est. Priority Date: 10/25/1996
• Status: Expired due to Term

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: General Motors Corporation (General Motors Company)
• Inventors: Reinke, Paul Edward, Groff, Edward George
• Primary Examiner(s): Bonck, Rodney H.
• Assistant Examiner(s): KWON, TAI CHOON
• Application Number:
  US08/738,351
• Time in Patent Office: 774 Days
• Field of Search: 477/48, 477/46, 477/107, 123/673
• US Class Current: 477/48
• CPC Class Codes: B60W 10/06 including control of combustion engines
• CPC Class Codes: B60W 10/101 Infinitely variable gearings
• CPC Class Codes: B60W 2540/10 Accelerator pedal position
• CPC Class Codes: B60W 2710/0622 Air-fuel ratio
• CPC Class Codes: B60W 2710/0627 Fuel flow rate
• CPC Class Codes: B60W 2710/0633 Inlet air flow rate
• CPC Class Codes: B60W 2710/1005 Transmission ratio engaged
• CPC Class Codes: B60W 30/18 Propelling the vehicle
• CPC Class Codes: F02D 2400/12 Engine control specially adapted for a transmission comprising a torque converter or for continuously variable transmissions
• CPC Class Codes: F02D 41/0215 in relation with elements of the transmission
• CPC Class Codes: F02D 41/1475 Regulating the air fuel ratio at a value other than stoichiometry
• CPC Class Codes: F16H 61/66 specially adapted for continuously variable gearings control of exclusively fluid gearing F16H61/38

Abstract

A powertrain control method applied to a lean burn engine coupled to a continuously variable transmission for minimizing engine out emissions selects one or more control parameters from a plurality of parameters that may be precisely controlled to provide for acceptable powertrain control with minimized emissions. Lean burn engine operation is maintained under low brake mean effective pressure conditions by modulating powertrain output power through transmission drive ratio variation. Fuel and air per cylinder may further be varied with the drive ratio when low emissions can be provided with minimum sacrifice to fuel economy. Lean burn operation is suspended under high brake mean effective pressure conditions by driving air/fuel ratio toward the stoichiometric ratio to exploit the efficiency of an included three-way catalytic treatment device while lowering engine speed to stabilize combustion.

Claims

1. A powertrain control method for controlling admission of air and fuel into a lean burn internal combustion engine and for controlling a continuously variable drive ratio of a transmission coupled to the engine, comprising the steps of:

sampling input signals indicating a current engine operating condition;

detecting when a predetermined lean burn engine operating condition characterized by low cylinder mean effective pressure is present,

sensing a desired powertrain output power level; and

while the predetermined lean burn engine operating condition is present, (a) selecting transmission drive ratio, engine fuel quantity per cylinder, and engine air volume per cylinder, as the control parameters that may be controlled to yield the desired powertrain output power level with minimum emissions, and (b) increasing engine fuel per cylinder and engine air volume per cylinder and decreasing transmission drive ratio to provide for the desired powertrain output power level with minumum emissions.

2. A powertrain control method for controlling admission of air and fuel into a cylinder of a lean burn internal combustion engine and for controlling a continuously variable drive ratio of a continuously variable transmission coupled to the engine, comprising the steps of:

sampling input signals indicating a current engine operating condition;

estimating engine cylinder mean effective pressure;

determining when the estimated engine cylinder mean effective pressure is less than a predetermined threshold pressure, indicating a low mean effective pressure condition;

detecting when the current engine operating condition is a predetermined lean burn engine operating condition;

sensing a commanded change in a powertrain output power level; and

while the predetermined lean burn engine operating condition is detected, (a) selecting transmission drive ratio, engine fuel quantity per cylinder and engine air volume per engine cylinder as the control parameters that may be controlled to provide a powertrain output power level change corresponding to the commanded change in powertrain output power level with minimum emissions, and (b) increasing engine fuel quantity per cylinder and engine air volume per cylinder while decreasing transmission drive ratio to provide for the powertrain output power level change while the low mean effective pressure condition is indicated to provide for the commanded change in powertrain output power level with minimum emissions.