Fuel vapor detection system for vehicles

Abstract

An electric motor or generator is used to spin the vehicle's internal combustion engine while the engine is not running, in order to draw a vacuum within the vapor control system. Vacuum bleed off is then monitored to determine if an unacceptable condition in the control system may exist. The evaporative fuel emissions test may be conducted either while the vehicle is at rest or while under way in an electric drive mode of operation.

1 . A method of detecting evaporative fuel emissions in a fuel vapor emission control system of an internal combustion engine driven vehicle while the engine is not running, comprising the steps of: 
 opening a fuel vapor management valve connecting the engine with the control system;    rotating the engine to reduce the fuel vapor pressure in the control system; and    measuring the vapor pressure in the control system, a change in pressure being related to possible fuel vapor evaporative fuel emissions in the control system.    
     
     
         2 . The method of  claim 1  further comprising the steps, prior to said opening step, of: 
 closing a first valve for controlling the escape of fuel vapor from the control system to the atmosphere; and    closing a throttle on the engine to prevent air from entering into the engine through the throttle.    
     
     
         3 . The method of  claim 2  further comprising the step, inbetween said rotating step and said measuring step, of: 
 closing the vapor management valve.    
     
     
         4 . The method of  claim 2 , wherein the step of closing the throttle comprises closing a throttle plate controlling the flow of air into engine.  
     
     
         5 . The method of  claim 1 , wherein the step of rotating the engine comprises powering the engine using an electric drive motor.  
     
     
         6 . The method of  claim 1 , wherein the rotating step is continued for a preselected length of time.  
     
     
         7 . The method of  claim 6 , wherein the step of measuring the vapor pressure is performed continuously during the preselected length of time.  
     
     
         8 . The method of  claim 6 , further comprising the step of closing a vapor management after the preselected time period.  
     
     
         9 . The method of  claim 1 , wherein the rotating step is continued for a preselected length of time, and the method further comprises closing a vapor management valve when the measured vapor pressure is below a preselected pressure.  
     
     
         10 . The method of  claim 1 , wherein the rotating step comprises powering the engine with an electrical generator operated as an electric motor.  
     
     
         11 . The method of  claim 1 , wherein the method further comprises ending rotation of the engine after the vapor pressure has been measured for a preselected length of time.  
     
     
         12 . The method of  claim 11 , wherein the method further comprises monitoring the vapor pressure after the engine rotation of the engine has ended.  
     
     
         13 . A method of detecting a evaporative fuel emissions in an evaporative vapor control system for a vehicle having a fuel tank, a vent valve controlling the flow of fuel vapor to a vent, an internal combustion engine having an intake manifold and a throttle valve for controlling the flow of air into the intake manifold, and a vapor management valve for controlling the flow of fuel vapor between the control system and the engine, comprising the steps of: 
 closing the vent valve;    closing the throttle valve to prevent air from being drawn into the engine;    opening the vapor management valve to place the intake manifold in fluid communication with the control system;    rotating the engine using an auxiliary power source to produce a partial vacuum in the control system;    closing the vapor management valve; and,    measuring changes the vapor pressure within the control system, changes in the vapor pressure indicating a possible evaporative fuel emissions in the control system.    
     
     
         14 . The method of  claim 13 , wherein closing the throttle valve comprises closing a throttle plate controlling air flow into he intake manifold.  
     
     
         15 . The method of  claim 13 , wherein rotating the engine is performed by using an electrical generator as the auxiliary power source.  
     
     
         16 . The method of  13 , wherein the rotating step is continued until the vapor pressure within the control system is reduced to a preselected pressure value.  
     
     
         17 . A method of  claim 13 , wherein the rotating step is continued for a presented length of time.  
     
     
         18 . The method of  claim 13 , wherein the method further comprises stopping rotation of the engine and the measuring step is performed after the rotating step has stopped.  
     
     
         19 . A method of detecting a evaporative fuel emissions in a fuel vapor emission control system of a hybrid powered vehicle having an internal combustion engine and an electric drive motor, comprising the steps of: 
 determining if the internal combustion engine is running;    if the internal combustion engine is determined not to be running, closing the emission control system;    opening a fuel vapor management valve connecting the engine with the emission control system;    rotating the engine to reduce the fuel vapor pressure within emission control system;    closing the fuel vapor management valve; and    measuring the vapor pressure in the emission control system, a change in the vapor pressure indicating a possible fuel vapor evaporative fuel emissions in the emission control system.    
     
     
         20 . The method of  claim 19 , wherein closing the emission control system comprises closing a valve connecting the emission control system with the atmosphere.  
     
     
         21 . The method of  claim 20 , wherein closing the emission control system further comprises closing an engine throttle valve to prevent the flow of air into the engine.  
     
     
         22 . The method of  claim 19 , wherein closing the emission control system comprises closing an engine throttle valve to prevent the flow of air into the engine.  
     
     
         23 . The method of  claim 19 , wherein rotating the engine comprises driving the engine with the electric motor.  
     
     
         24 . The method of  claim 19 , wherein rotating the engine comprises driving the engine with an electric generator.  
     
     
         25 . The method of  claim 19 , wherein rotating the engine is performed for a preselected length of time.  
     
     
         26 . The method of  claim 19 , wherein rotating the engine is performed until the vapor pressure in the emission control system is reduced to a preselected pressure level.  
     
     
         27 . The method of  claim 25 , wherein the step of measuring the vapor pressure level is performed after the vapor pressure has been reduced to at least the preselected pressure level.