Valve actuator assembly having a center biased spool valve with detent feature
A valve actuator assembly for an engine includes a movable poppet valve, and movable first and second spool valves. The assembly also includes an intermediate channel interconnecting the first and second spool valve, a driving channel, and a first and second feedback channel interconnecting the second spool valve and the poppet valve. The valve actuator assembly includes an actuator cooperating with the first spool valve to position the first spool valve to selectively allow high pressure fluid flow to the second spool valve and the driving channel to position the engine valve. The valve actuator assembly further includes a first and second on/off valve in respective fluid communication with the first feedback channel and the second feedback channel to selectively exhaust the first and second feedback channel to control motion of the second spool valve. The second spool valve includes a detent feature operable to maintain the second spool valve in a center biased position.
1. A valve actuator assembly for an internal combustion engine comprising:
a housing;
a movable poppet valve;
a movable first spool valve;
a movable second spool valve having a center biased position and detent feature;
a driving channel interconnecting said second spool valve and said poppet valve;
an intermediate channel interconnecting said first spool valve and said second spool valve;
a first feedback channel interconnecting said second spool valve and said poppet valve;
a second feedback channel interconnecting said second spool valve and said poppet valve;
an actuator operatively cooperating with said first spool valve to position said first spool valve thereby selectively allowing fluid flow in and out of said second spool valve and said driving channel to position said poppet valve;
a first on/off valve in fluid communication with said first feedback channel to selectively exhaust said first feedback channel; and
a second on/off valve in fluid communication with said second feedback channel to selectively exhaust said second feedback channel, whereby the first on/off valve and the second on/off valve control motion of the second spool valve;
wherein said detent feature includes a second spool valve spring preloaded between a first spring retainer and said housing, and a third spool valve spring preloaded between a second spring retainer and said housing; and
wherein the preload of only one of said second and third spool valve springs is applied to said second spool valve when displaced from said center biased position.
2. The valve actuator assembly of claim 1 , wherein said housing defines a first fluid chamber in fluid communication with said driving channel and a second fluid chamber in fluid communication with said first feedback channel.
3. The valve actuator assembly of claim 2 , further comprising a first piston operatively cooperating with said poppet valve, wherein said first piston is disposed in said housing and has said first fluid chamber on one side and said second fluid chamber on an opposite side.
4. The valve actuator assembly of claim 2 , wherein said housing defines a third fluid chamber in fluid communication with said second feedback channel; and
wherein the valve actuator assembly further includes a second piston operatively cooperating with said poppet valve, wherein said second piston is disposed in said housing and has said third fluid chamber on one side thereof.
5. The valve actuator assembly of claim 4 , further comprising:
a first on/off valve channel interconnecting said second fluid chamber and said first on/off valve;
a second on/off valve channel interconnecting said third fluid chamber and said second on/off valve.
6. The valve actuator assembly of claim 4 , further comprising:
a fourth fluid chamber defined by said housing and disposed at one end of said second spool valve, wherein said fourth fluid chamber is in fluid communication with said first feedback channel;
a fifth fluid chamber defined by said housing and disposed at one end of said second spool valve opposite said fourth fluid chamber, wherein said fifth fluid chamber is in fluid communication with said second feedback channel;
wherein said second spool valve spring and said first spring retainer are at least partially disposed within said fourth fluid chamber and operable to bias said second spool valve toward said center biased position;
wherein said third spool valve spring and said second spring retainer are at least partially disposed within said fifth fluid chamber and operable to bias said second spool valve toward said center biased position.
7. An internal combustion engine having an engine block with a cylinder head mounted thereto, wherein the cylinder head includes at least one poppet valve movable therein, the internal combustion engine comprising:
a valve actuator assembly mounted with respect to the cylinder head, the valve actuator assembly including:
a housing;
a movable poppet valve;
a movable first spool valve;
a movable second spool valve having a center biased position and detent;
a driving channel interconnecting said second spool valve and said poppet valve;
an intermediate channel interconnecting said first spool valve and said second spool valve;
a first feedback channel interconnecting said second spool valve and said poppet valve;
a second feedback channel interconnecting said second spool valve and said poppet valve;
an actuator operatively cooperating with said first spool valve to position said first spool valve thereby selectively allowing fluid flow in and out of said second spool valve and said driving channel to position said poppet valve;
a first on/off valve in fluid communication with said first feedback channel to selectively exhaust said first feedback channel;
a second on/off valve in fluid communication with said second feedback channel to selectively exhaust said second feedback channel, whereby the first on/off valve and the second on/off valve control motion of the second spool valve;
a first fluid chamber defined by said housing and disposed in fluid communication with said driving channel;
a second fluid chamber defined by said housing and disposed in fluid communication with said first feedback channel;
a third fluid chamber defined by said housing and disposed in fluid communication with said second feedback channel;
a fourth fluid chamber defined by said housing and disposed at one end of said second spool valve, wherein said fourth fluid chamber is in fluid communication with said first feedback channel;
a fifth fluid chamber defined by said housing and disposed at one end of said second spool valve opposite said fourth fluid chamber, wherein said fifth fluid chamber is in fluid communication with said second feedback channel;
a first piston operatively cooperating with said poppet valve, wherein said first piston is disposed in said housing and has said first fluid chamber on one side and said second fluid chamber on an opposite side;
a second piston operatively cooperating with said poppet valve and being disposed in said housing and having said third fluid chamber on one side thereof;
a second spool valve spring intermediate a first spring retainer and said housing, said first spring retainer and second spool valve at least partially disposed within said fourth fluid chamber and operable to bias said second spool valve toward said center biased position;
a third spool valve spring intermediate a second spring retainer and said housing, said second spring retainer and third spool valve at least partially disposed within said fifth fluid chamber and operable to bias said second spool valve toward said center biased position; and
wherein said second spool valve spring and retainer and said third spool valve spring and retainer cooperate to provide said detent feature to said second spool valve; and
wherein only one of said second and third spool valve springs is in operative communication with said second spool valve when displaced from said center biased position.