Variable intake valve assembly for internal combustion engine

Abstract

An intake valve assembly of an internal combustion engine that includes a combustion chamber and an intake passage. The intake valve assembly comprises an intake valve movable into and out of engagement with a valve seat, a reciprocating primary valve tappet, and a secondary valve tappet axially non-movably attached to the primary valve tappet. The intake valve is mounted to the primary valve tappet and axially freely movable relative thereto. The primary valve tappet is configured for axially engaging the first intake valve to limit the axial movement thereof said intake valve away from the valve seat. The secondary valve tappet is configured for axially engaging the intake valve for mechanically moving the intake valve away from the valve seat. The intake valve is further operated fluidly in response to pressure differential between the intake passage and the combustion chamber.

1 . An intake valve assembly of an internal combustion engine including a combustion chamber and an intake passage fluidly communicating with said combustion chamber through an intake port, said intake valve assembly comprising:
 an intake valve movable into and out of engagement with a valve seat formed in said intake port between respective closed and open positions so that in said closed position of said intake valve said combustion chamber being sealed from said intake passage, said intake valve having first and second contact surfaces axially spaces from each other;   a primary valve tappet reciprocating between an innermost position and an outermost position, said primary valve tappet having a primary tappet surface complementary to said first contact surface of said intake valve; and   a secondary valve tappet having a secondary tappet surface complementary to said second contact surface of said intake valve, said secondary valve tappet axially non-movably attached to said primary valve tappet so that said secondary tappet surface being axially spaced from said second contact surface of said intake valve when said primary tappet surface of said primary valve tappet being in engagement with said first contact surface of said intake valve;   said intake valve being coaxially mounted to said primary valve tappet and axially freely movable relative thereto between said primary tappet surface of said primary valve tappet and said secondary tappet surface of said secondary valve tappet;   said primary tappet surface of said primary valve tappet configured for operatively axially engaging said first contact surface of said intake valve to limit the axial movement of said intake valve away from said valve seat and to place said intake valve in said closed position thereof when said primary valve tappet being in said innermost position thereof;   said secondary tappet surface of said secondary valve tappet configured for operatively axially engaging said second contact surface of said intake valve for mechanically moving said intake valve away from said valve seat;   said intake valve being operated both mechanically by both said primary and secondary valve tappets and fluidly in response to pressure differential between said intake passage and said combustion chamber.   
   
   
       2 . The intake valve assembly as defined in  claim 1 , wherein said combustion chamber fluidly communicates with said intake passage only when said intake valve is in said open position. 
   
   
       3 . The intake valve assembly as defined in  claim 2 , wherein said first contact surface of said intake valve is configured for operative engagement with said primary tappet surface of said primary valve tappet to mechanically close said intake valve and said second contact surface of said intake valve is configured for operative engagement with said secondary tappet surface of said secondary valve tappet to mechanically open said intake valve. 
   
   
       4 . The intake valve assembly as defined in  claim 3 , wherein said intake valve is axially freely movable along said primary valve tappet in response to pressure differential between said intake passage and said combustion chamber when said primary tappet surface of said primary valve tappet is axially spaced from said first contact surface of said intake valve. 
   
   
       5 . The intake valve assembly as defined in  claim 4 , further comprising a valve spring for normally biasing said primary valve tappet toward said innermost position thereof and said intake valve to said closed position thereof through said primary valve tappet. 
   
   
       6 . The intake valve assembly as defined in  claim 5 , wherein said primary valve tappet includes an elongated stem and a tappet head provided at a distal end of said stem, said tappet head of said primary valve tappet is provided with said primary tappet surface. 
   
   
       7 . The intake valve assembly as defined in  claim 6 , wherein said intake valve is a poppet valve including a stem portion, a valve head complementary to said valve seat for sealingly engaging said valve seat and a substantially cylindrical bore extending through both said stem portion and said valve head of said intake valve; and wherein a distal end of said valve head of said intake valve is provided with said first contact surface and a distal end of said stem portion of said intake valve is provided with said second contact surface. 
   
   
       8 . The intake valve assembly as defined in  claim 7 , wherein said valve head of said intake valve is shaped so that said first contact surface thereof is configured to complement said primary tappet surface of said tappet head of said primary valve tappet. 
   
   
       9 . The intake valve assembly as defined in  claim 7 , wherein said stem of said primary valve tappet is axially extending through said cylindrical bore in said intake valve substantially coaxially therewith so that said intake valve is mounted about said stem of said primary valve tappet and axially freely movable relative thereto between said primary tappet surface of said primary valve tappet and said secondary tappet surface of said secondary valve tappet. 
   
   
       10 . The intake valve assembly as defined in  claim 9 , wherein said secondary valve tappet is in the form of an elongated tubular stem mounted about said stem of said primary valve tappet substantially coaxially therewith. 
   
   
       11 . The intake valve assembly as defined in  claim 10 , wherein said secondary valve tappet is provided with a valve spring retainer formed integrally therewith. 
   
   
       12 . The intake valve assembly as defined in  claim 11 , wherein said valve spring is normally contracted for continuously biasing said primary valve tappet toward said innermost position thereof. 
   
   
       13 . The intake valve assembly as defined in  claim 12 , wherein said valve spring is in the form of a coil spring mounted about said elongated tubular stem of said secondary valve tappet. 
   
   
       14 . The intake valve assembly as defined in  claim 13 , further comprising a valve guide supporting said elongated tubular stem of said secondary valve tappet for reciprocatingly sliding said primary valve tappet between said innermost and outermost positions thereof. 
   
   
       15 . The intake valve assembly as defined in  claim 13 , wherein said valve guide slideably engages both said elongated tubular stem of said secondary valve tappet and said stem portion of said intake valve. 
   
   
       16 . The intake valve assembly as defined in  claim 1 , further comprising an intake cam lobe acting on said primary valve tappet; said intake cam lobe having a fixed cam profile including a leading flank and a trailing flank; said leading flank has a variable gradient such that said primary valve tappet slows down before said secondary contact surface of said secondary valve tappet contacts said second contact surface of said intake valve.