Gasoline engine knock control

Abstract

Various methods of control of combustion knock are disclosed in relation to a spark ignition, internal combustion engine having active tappets, whereby an inlet poppet valve can be moved independently of the usual operating cam. In one embodiment the invention provides for combustion knock to be controlled solely by variation of inlet air charge.

1 - 21 . (canceled) 
     
     
         22 . A method of combustion knock control in a reciprocating piston internal combustion engine having a combustion chamber, an inlet valve at an inlet to said combustion chamber, and an active tappet for said inlet valve whereby valve operation may be adjusted on demand, said method comprising:
 a) detecting combustion knock during a combustion event in the combustion chamber;   b) commanding said active tappet to vary operation of the inlet valve in a knock reducing manner for a subsequent combustion event in said combustion chamber by at least re-timing an opening of the inlet valve to increase or reduce overlap with operation of at least one exhaust valve of said combustion chamber so as to increase or reduce the duration over which both of said valves are open simultaneously, and   c) repeating said detecting and said commanding for successive combustion events in said chamber until combustion knock is not detected.   
     
     
         23 . A method of  claim 22 , further comprising:
 d) detecting an absence of combustion knock in said combustion chamber;   e) commanding said active tappet to vary operation of the associated valve in a knock approaching manner for the subsequent combustion event in said chamber, and   f) repeating steps d) and e) until combustion knock is again detected.   
     
     
         24 . A method of  claim 22 , wherein commanding said active tappet reduces an air charge in said combustion chamber. 
     
     
         25 . A method of  claim 22 , wherein commanding said active tappet reduces an air charge in said combustion chamber and retards commencement of combustion in said combustion chamber. 
     
     
         26 . The method of  claim 25 , wherein the commencement of combustion is retarded by retarding the timing of an ignition spark. 
     
     
         27 . A method of combustion knock control in a spark ignition, reciprocating piston internal combustion engine having a combustion chamber, an inlet valve at an inlet to said combustion chamber, and an active tappet for said inlet valve whereby valve operation may be adjusted on demand, and a system of varying timing of an ignition spark, said method comprising:
 a) providing a threshold operating temperature for said engine;   b) below said threshold permitting treatment of combustion knock by operation of said active tappet and/or by operation of said system; and   c) above said threshold permitting treatment of combustion knock solely by operation of said active tappet.   
     
     
         28 . A method according to  claim 27 , wherein said operation of said active tappet comprises permitting at least re-timing opening of the inlet valve to increase or reduce overlap with operation of at least one exhaust valve of said combustion chamber so as to increase or reduce a duration over which both of said inlet valve and said exhaust valve are open simultaneously. 
     
     
         29 . A method according to  claim 27 , wherein above said threshold combustion knock is treated by commanding said active tappet to reduce air charge in said combustion chamber. 
     
     
         30 . A method according to  claim 27 , wherein above said threshold a timing of an ignition spark is fixed. 
     
     
         31 . A method according to  claim 30 , wherein said timing is fixed at an instant value of a time of exceeding said threshold, and remains fixed until subsequently falling below said threshold. 
     
     
         32 . A method of combustion knock control in a spark ignition reciprocating piston internal combustion engine having a combustion chamber, an inlet valve at an inlet to said combustion chamber, and an active tappet for said inlet valve whereby valve operation may be adjusted on demand and a system of varying timing of an ignition spark, said method comprising:
 a) for higher octane fuel, controlling combustion knock solely by varying a timing of an ignition spark and   b) for lower octane fuel, controlling combustion knock by a combination of varying the timing on an ignition spark and commanding said active tappet to vary air charge admitted to said combustion chamber.   
     
     
         33 . A method according to  claim 32 , wherein said commanding said active tappet to vary the air charge admitted to said combustion chamber comprises at least re-timing opening of the inlet valve to increase or reduce overlap with operation of at least one exhaust valve of said combustion chamber so as to increase or reduce a duration over which both of said inlet valve and said exhaust valve are open simultaneously. 
     
     
         34 . A method according to  claim 32 , wherein higher octane fuel lies in a range 90-100 RON, and lower octane fuel lies in the range 80-95 RON. 
     
     
         35 . The method of  claim 22 , wherein the combustion chamber is in a cylinder of a multi-cylinder engine. 
     
     
         36 . The method of  claim 35 , comprising controlling the active tappet of the inlet valve for each cylinder, to vary the respective air charge admitted to each cylinder. 
     
     
         37 . The method of  claim 36 , comprising controlling combustion knock cylinder by cylinder. 
     
     
         38 . An electric control unit configured to control an internal combustion engine having a combustion chamber, an inlet valve at an inlet to said combustion chamber, and an active tappet for said inlet valve whereby valve operation may be adjusted on demand, the electric control unit comprising:
 a processor; and   a memory associated with the processor, the memory having control parameters,   wherein the processor is configured to implement a method of combustion knock control in reference to the control parameters, the method comprising one of   (i) detecting combustion knock during a combustion event in the combustion chamber,
 commanding said active tappet to vary operation of the inlet valve in a knock reducing manner for a subsequent combustion event in said combustion chamber by at least re-timing an opening of the inlet valve to increase or reduce overlap with operation of at least one exhaust valve of said combustion chamber so as to increase or reduce the duration over which both of said valves are open simultaneously, and 
 repeating said detecting and said commanding for successive combustion events in said chamber until combustion knock is not detected; or 
   (ii) providing a threshold operating temperature for said engine,
 below said threshold permitting treatment of combustion knock by operation of said active tappet and/or by operation of said system, and 
 above said threshold permitting treatment of combustion knock solely by operation of said active tappet; or 
   (iii) for higher octane fuel, controlling combustion knock solely by varying a timing of an ignition spark, and
 for lower octane fuel, controlling combustion knock by a combination of varying the timing on an ignition spark and commanding said active tappet to vary air charge admitted to said combustion chamber. 
   
     
     
         39 . An internal combustion engine, comprising:
 a combustion chamber;   an inlet valve at an inlet to said combustion chamber; and   an active tappet for said inlet valve whereby valve operation may be adjusted on demand,   the engine being controllable according to a method of combustion knock control, the method comprising one of   (i) detecting combustion knock during a combustion event in the combustion chamber,
 commanding said active tappet to vary operation of the inlet valve in a knock reducing manner for a subsequent combustion event in said combustion chamber by at least re-timing an opening of the inlet valve to increase or reduce overlap with operation of at least one exhaust valve of said combustion chamber so as to increase or reduce the duration over which both of said valves are open simultaneously, and 
 repeating said detecting and said commanding for successive combustion events in said chamber until combustion knock is not detected; or 
   (ii) providing a threshold operating temperature for said engine,
 below said threshold permitting treatment of combustion knock by operation of said active tappet and/or by operation of said system, and 
 above said threshold permitting treatment of combustion knock solely by operation of said active tappet; or 
   (iii) for higher octane fuel, controlling combustion knock solely by varying a timing of an ignition spark, and
 for lower octane fuel, controlling combustion knock by a combination of varying the timing on an ignition spark and commanding said active tappet to vary air charge admitted to said combustion chamber. 
   
     
     
         40 . The internal combustion engine of  claim 39 , wherein
 the active tappet comprises an electro-hydraulic actuation device for continuously varying a valve lift of a said inlet valve   
     
     
         41 . The internal combustion engine of  claim 40 , wherein
 the active tappet is between a cam and the inlet valve, and   the active tappet is for continuously varying the valve lift of the inlet valve independently of the cam.   
     
     
         42 . A vehicle comprising:
 an internal combustion engine including a combustion chamber, an inlet valve at an inlet to said combustion chamber, and an active tappet for said inlet valve whereby valve operation may be adjusted on demand; and   
       an electric control unit for controlling the engine, the electric control unit including a processor and a memory associated with the processor, the memory having control parameters,
 wherein the processor is configured to implement a method of combustion knock control in reference to the control parameters, the method comprising one of 
 (i) detecting combustion knock during a combustion event in the combustion chamber,
 commanding said active tappet to vary operation of the inlet valve in a knock reducing manner for a subsequent combustion event in said combustion chamber by at least re-timing an opening of the inlet valve to increase or reduce overlap with operation of at least one exhaust valve of said combustion chamber so as to increase or reduce the duration over which both of said valves are open simultaneously, and 
 repeating said detecting and said commanding for successive combustion events in said chamber until combustion knock is not detected; or 
 
 (ii) providing a threshold operating temperature for said engine,
 below said threshold permitting treatment of combustion knock by operation of said active tappet and/or by operation of said system, and 
 above said threshold permitting treatment of combustion knock solely by operation of said active tappet; or 
 
 (iii) for higher octane fuel, controlling combustion knock solely by varying a timing of an ignition spark, and
 for lower octane fuel, controlling combustion knock by a combination of varying the timing on an ignition spark and commanding said active tappet to vary air charge admitted to said combustion chamber.