Method and system for controlling an internal combustion engine having a brake booster

Abstract

The invention relates to a method and system for controlling an internal combustion engine ( 9 ) in a motor vehicle having a brake booster ( 1 ), a low pressure chamber ( 2 ) of the brake booster being connected to the intake manifold ( 8 ) of the internal combustion engine ( 9 ). To ensure that the brake booster ( 1 ) functions during a forced warm up of a catalytic converter, the pressure in the brake booster ( 1 ) is monitored by pressure sensors ( 7 a , 7 b ). If too high a pressure is detected, the internal combustion engine ( 9 ) is actuated by an engine control system ( 10 ) to decrease intake manifold ( 8 ) pressure, for example, by increasing the engine speed after startup. Spark retard, a measure for warming up a catalytic converter, is temporarily reduced or eliminated, if increasing engine speed is insufficient to reduce pressure.

We claim:  
     
         1 . A method for controlling an internal combustion engine to maintain pressure in a brake booster during warmup of an exhaust gas treatment device coupled to the internal combustion engine, the brake booster being coupled to an intake of the internal combustion engine and being actuated by a reduced pressure in the intake, comprising: monitoring pressure in the brake booster; and decreasing pressure in the engine intake when said pressure in the brake booster is greater than a threshold pressure.  
     
     
         2 . The method of  claim 1  wherein said threshold pressure is a pressure above which an operational capability of the brake booster is less than a desired operational capability.  
     
     
         3 . The method of  claim 1  wherein said monitoring comprises measuring a pressure in a low pressure side of the brake booster.  
     
     
         4 . The method of  claim 1  wherein monitoring comprises measuring a pressure difference between a high pressure and a low pressure side of the brake booster.  
     
     
         5 . The method of  claim 1 , further comprising: 
 Increasing engine speed after startup of the engine to ensure a sufficient partial vacuum in the engine intake.    
     
     
         6 . The method of  claim 5  wherein said increase is based on providing a desired functional capability of the brake booster.  
     
     
         7 . The method of  claim 1 , further comprising: 
 reducing an amount of spark retard to bring said brake booster pressure below said threshold wherein said spark retard is employed to warmup the exhaust gas treatment device.    
     
     
         8 . The method of  claim 5 , further comprising: 
 reducing an amount of spark retard to bring said brake booster pressure below said threshold when said increasing of engine speed is insufficient to bring about the brake booster vacuum below said threshold.    
     
     
         9 . An engine control system for the internal combustion engine of a motor vehicle having an exhaust gas treatment arrangement coupled to the engine, a brake booster actuated by a vacuum being coupled to the intake of the internal combustion engine, comprising: 
 a control system which monitors pressure in the brake booster and decreases pressure in the engine intake when said pressure in the brake booster is greater than a threshold pressure    
     
     
         10 . The system of  claim 9 , further comprising: a pressure sensor on a low pressure side of the brake booster.  
     
     
         11 . The system of  claim 9 , further comprising: a differential pressure sensor between low and high pressure sides of the brake booster.  
     
     
         12 . The system of  claim 9  wherein said control system causes engine speed to increase when said pressure is greater than a threshold pressure.  
     
     
         13 . The system of  claim 9  wherein said control system advances spark timing when said pressure is greater than a threshold pressure.  
     
     
         14 . The system of  claim 12 , wherein said control system advances spark timing when said engine speed increase is insufficient to cause said intake pressure to exceed said threshold pressure.