Engine Management

Abstract

An in-cylinder pressure sensor obtains a high resolution pressure curve for each cylinder cycle allowing the various data to be derived for improved monitoring and control of operation of the engine. A more accurate measure of work done by the engine is obtained allowing more accurate estimation of the vehicle torque and hence real torque control. In addition, engine losses can be more accurately calculated and the estimates corrected yet further by obtaining an accurate top dead centre position for the engine cylinders.

1 . A method of deriving vehicle torque comprising measuring cylinder pressure during a cylinder cycle;
 constructing a pressure variation function;   obtaining work done by the engine therefrom and driving vehicle torque from the work done.   
   
   
       2 . A method as claimed in  claim 1  further including identifying vehicle motive efficiency losses and subtracting these from engine work done to derive vehicle torque. 
   
   
       3 . A method as claimed in  claim 1  in which the vehicle motive efficiency loss is derived from a map and/or model. 
   
   
       4 . A method as claimed in  claim 1  further comprising controlling vehicle performance by adjusting a performance input variable to control the derived vehicle torque to a target vehicle torque. 
   
   
       5 . A method as claimed in  claim 1  further comprising deriving loss from the difference between the measure of engine shaft output and the measure of work done on a piston in the cylinder. 
   
   
       6 . An engine management system for an internal combustion engine having at least one cylinder pressure sensor and a data processor arranged to receive the pressure measurement during a cylinder cycle from the cylinder pressure sensor and process the measured pressure according to the method of  claim 1 . 
   
   
       7 . An engine management system for an internal combustion engine having at least one cylinder pressure sensor and at least one engine actuator and a data processor arranged to receive pressure measurements during a cycle from the cylinder pressure sensor and an actuator controller arranged to control the actuator according to a performance input variable to carry out a method as claimed in  claim 1 . 
   
   
       8 . A computer readable medium containing processing instructions to enable a processor to carry out a method as claimed in  claim 1 . 
   
   
       9 . A method as claimed in  claim 2  in which vehicle motive efficiency loss is measured by skip firing an engine cylinder cycle and measuring corresponding vehicle deceleration. 
   
   
       10 . A method as claimed in  claim 3  in which the derived vehicle motive efficiency loss is correlated against the measured vehicle motive efficiency loss to refine the map or model. 
   
   
       11 . A method as claimed in  claim 5  further comprising adjusting a performance input variable to control the measure of engine shaft output to a target value or range to obtain a target measure of engine shaft output. 
   
   
       12 . A method as claimed in  claim 11  further comprising monitoring vehicle performance by obtaining separately a measure of engine shaft output and/or engine friction losses estimate and comparing the or each estimate against the respective derived value to correct the estimate. 
   
   
       13 . A method as claimed in  claim 12  further comprising controlling vehicle performance by adjusting a performance input variable to control the derived measure of engine shaft output to a target measure of engine shaft output. 
   
   
       14 . A method of obtaining the indicated mean effective pressure IMEP for a vehicle engine cylinder comprising measuring the cylinder pressure during a cylinder cycle, obtaining corresponding values of cylinder volume during the cycle, deriving top dead centre during the cycle, correcting the volume values based on the derived value of top dead centre, and integrating pressure against volume to obtain the IMEP. 
   
   
       15 . A method as claimed in  claim 14  in which top dead centre is derived at a maximum pressure point of the motoring pressure curve. 
   
   
       16 . A method as claimed in  claim 14  further comprising controlling vehicle performance deriving a vehicle performance output valve from the IMEP and adjusting a vehicle performance input variable to control the derived vehicle performance output value to a target vehicle performance output value. 
   
   
       17 . A method of diagnosing engine conditions in an engine with two or more cylinders comprising the steps of skip firing individual cylinders, deriving a measure of engine friction loss and comparing the derived loss to diagnose a respective cylinder condition.