Auxiliary cam phaser hydraulic circuit and method of operation

Abstract

Provided is an auxiliary cam phaser hydraulic circuit for an internal combustion engine having an engine driven hydraulic pump and at least one cam phaser in fluid communication with a cam phaser control valve. The auxiliary cam phaser hydraulic circuit includes a reservoir containing fluid and an auxiliary hydraulic pump in fluid communication with the reservoir and operable to pressurize the fluid and communicate the fluid under pressure to a cam phaser feed passage. The cam phaser feed passage is in fluid communication with the cam phaser control valve, which operates to selectively and variably communicate the fluid to the cam phaser. A method of starting and operating an internal combustion engine is also provided. An internal combustion engine incorporating the auxiliary cam phaser hydraulic circuit is also disclosed.

1 . An auxiliary cam phaser hydraulic circuit for an internal combustion engine having an engine driven hydraulic pump and at least one cam phaser in fluid communication with a cam phaser control valve, the auxiliary cam phaser hydraulic circuit comprising: 
 a source containing fluid;    an auxiliary hydraulic pump in fluid communication with said source and operable to pressurize said fluid and communicate said fluid under pressure to a cam phaser feed passage; and    wherein said cam phaser feed passage is in fluid communication with the cam phaser control valve, the cam phaser control valve being operable to selectively and variably communicate said fluid to said cam phaser.    
   
   
       2 . The auxiliary cam phaser hydraulic circuit of  claim 1 , wherein said auxiliary hydraulic pump is driven by an electric motor.  
   
   
       3 . The auxiliary cam phaser hydraulic circuit of  claim 2 , further comprising an electronic control unit operable to control said electric motor.  
   
   
       4 . The auxiliary cam phaser hydraulic circuit of  claim 1 , further comprising an electronic control unit operable to control the cam phaser control valve.  
   
   
       5 . The auxiliary cam phaser hydraulic circuit of  claim 4 , wherein said electronic control unit is preprogrammed to command the cam phaser control valve to enable the at least one cam phaser to enable one of late intake valve closing and early intake valve closing to enable a reduction in effective compression ratio during starting of the internal combustion engine.  
   
   
       6 . The auxiliary cam phaser hydraulic circuit of  claim 1 , further comprising: 
 a main lubrication passage operable to receive said fluid from the engine driven hydraulic pump;    wherein said main lubrication passage is in selective fluid communication with said cam phaser feed passage; and    a check valve configured to selectively communicate said fluid from said main lubrication passage to said cam phaser feed passage and to substantially disallow communication of said fluid from said cam phaser feed passage to said main lubrication passage.    
   
   
       7 . The auxiliary cam phaser hydraulic circuit of  claim 1 , further comprising: 
 a main lubrication passage operable to receive said fluid from the engine driven hydraulic pump;    wherein said main lubrication passage is in fluid communication with said cam phaser feed passage; and    wherein said auxiliary pump is configured to provide said fluid under pressure to said main lubrication passage via said cam phaser feed passage.    
   
   
       8 . A method of starting and operating an internal combustion engine having at least one hydraulically actuatable cam phaser and an engine driven hydraulic pump, the method comprising: 
 providing pressurized fluid to the at least one hydraulically actuatable cam phaser when the internal combustion engine is shutoff;    controlling said at least one hydraulically actuatable cam phaser to command the internal combustion engine to operate in one of a late intake valve opening and an early intake valve opening mode of operation; and    starting the internal combustion engine.    
   
   
       9 . The method of  claim 8 , further comprising: 
 continuing to provide pressurized fluid to the at least one hydraulically actuatable cam phaser during engine operation between idle engine speed and a threshold engine speed.    
   
   
       10 . The method of  claim 8 , wherein an auxiliary hydraulic pump provides pressurized fluid to the at least one hydraulically actuatable cam phaser.  
   
   
       11 . The method of  claim 9 , wherein said threshold engine speed is the engine speed below which the engine driven hydraulic pump cannot provide the required fluid flow and pressure to actuate the at least one hydraulically actuatable cam phaser.  
   
   
       12 . The method of  claim 9 , further comprising: 
 communicating pressurized fluid from the engine driven hydraulic pump to the at least one hydraulically actuatable cam phaser during engine operation above said threshold speed.    
   
   
       13 . An internal combustion engine comprising: 
 an engine driven hydraulic pump;    at least one cam phaser in fluid communication with a cam phaser control valve;    a source containing fluid;    an auxiliary hydraulic pump in fluid communication with said source and operable to pressurize said fluid and communicate said fluid under pressure to a cam phaser feed passage; and    wherein said cam phaser feed passage is in fluid communication with the cam phaser control valve, the cam phaser control valve being operable to selectively and variably communicate said fluid to said cam phaser.    
   
   
       14 . The internal combustion engine of  claim 13 , wherein said auxiliary hydraulic pump is driven by an electric motor.  
   
   
       15 . The internal combustion engine of  claim 14 , further comprising an electronic control unit operable to control said electric motor.  
   
   
       16 . The internal combustion engine of  claim 13 , further comprising an electronic control unit operable to control the cam phaser control valve.  
   
   
       17 . The internal combustion engine of  claim 16 , wherein said electronic control unit is preprogrammed to command the cam phaser control valve to enable the at least one cam phaser to enable one of late intake valve closing and early intake valve closing to enable a reduction in effective compression ratio during starting of the internal combustion engine.  
   
   
       18 . The internal combustion engine of  claim 13 , further comprising: 
 a main lubrication passage operable to receive said fluid from the engine driven hydraulic pump;    wherein said main lubrication passage is in selective fluid communication with said cam phaser feed passage; and    a check valve configured to selectively communicate said fluid from said main lubrication passage to said cam phaser feed passage and to substantially disallow communication of said fluid from said cam phaser feed passage to said main lubrication passage.    
   
   
       19 . The internal combustion engine of  claim 13 , further comprising: 
 a main lubrication passage operable to receive said fluid from the engine driven hydraulic pump;    wherein said main lubrication passage is in fluid communication with said cam phaser feed passage; and    wherein said auxiliary pump is configured to provide said fluid under pressure to said main lubrication passage via said cam phaser feed passage.