Abstract:
A valve actuator assembly for an engine includes a movable engine valve and a movable spool valve. The valve actuator assembly also includes a driving channel interconnecting the spool valve and the engine valve and a feedback channel interconnecting the spool valve and the engine valve. The valve actuator assembly includes an actuator operatively cooperating with the spool valve to position the spool valve to prevent and allow fluid flow in and out of the driving channel to position the engine valve. The valve actuator assembly further includes an on/off valve in fluid communication with the feedback channel to enable and disable the feedback channel to control motion of the spool valve.

Description:
TECHNICAL FIELD 
     The present invention relates generally to intake or exhaust valve actuators for engines and, more particularly, to a valve actuator assembly with hydraulic feedback for an internal combustion engine. 
     BACKGROUND OF THE INVENTION 
     It is known to provide a valve train or valve actuator assembly for an engine such as an internal combustion engine of a vehicle such as a motor vehicle. Typically, the valve train includes one or more valves, a cam shaft having one or more cams, and a tappet contacting each cam and valve. Typically, engine valve actuation is accomplished via the engine-driven camshaft. However, this type of valve actuation introduces constraints on valve operation that preclude optimal valve opening and closing schedules, compromising engine performance, fuel economy, and emissions. 
     It is also known to provide a camless valve train for an internal combustion engine. An example of such a camless valve train is disclosed in the prior art. For example, a camless intake/exhaust valve for an internal combustion engine is controlled by a solenoid actuated fluid control valve. The control valve has a pair of solenoids that move a spool. The solenoids are digitally latched by short digital pulses provided by a microcontroller. 
     One disadvantage of some camless valve trains is their poor controllability due to open loop instability, which causes great difficulty in their operation. Another disadvantage of some camless valve trains is that they do not provide full capability for variable lift. Further disadvantages of some camless valve trains are that they have relatively high cost, large size, high energy consumption, low repeatability from cycle to cycle and cylinder to cylinder, hard seating impact, and high seating velocity induced noise. 
     As a result, it is desirable to provide a valve actuator assembly for an engine that improves controllability. It is also desirable to provide a valve actuator assembly for an engine having more flexibility and full capacity for variable lift. It is further desirable to provide a valve actuator assembly for an engine that reduces energy consumption and provides satisfactory seating velocity. Therefore, there is a need in the art to provide a valve actuator assembly for an engine that meets these desires. 
     SUMMARY OF THE INVENTION 
     It is, therefore, one object of the present invention to provide a new camless valve actuator assembly for an engine. 
     It is another object of the present invention to provide a valve actuator assembly for an engine that has hydraulic feedback for controllability. 
     To achieve the foregoing objects, the present invention is a valve actuator assembly for an engine. The valve actuator assembly includes a movable engine valve and a movable spool valve. The valve actuator assembly also includes a driving channel interconnecting the spool valve and the engine valve and a feedback channel interconnecting the spool valve and the engine valve. The valve actuator assembly includes an actuator operatively cooperating with the spool valve to position the spool valve to prevent and allow fluid flow in and out of the driving channel to position the engine valve. The valve actuator assembly further includes an on/off valve in fluid communication with the feedback channel to enable and disable the feedback channel to control motion of the spool valve. 
     One advantage of the present invention is that a valve actuator assembly is provided for an engine that has hydraulic feedback for precise motion by self-regulating flow control. Another advantage of the present invention is that the valve actuator assembly has controllability that is open loop stable with automatic regulation. Yet another advantage of the present invention is that the valve actuator assembly is an enabler for improved valve train stability without sacrificing dynamic performance. Still another advantage of the present invention is that the valve actuator assembly is an enabler for improved engine performance, improved engine fuel economy by lowering fuel consumption, and improved engine emissions by lowering emissions. A further advantage of the present invention is that the valve actuator assembly minimizes energy consumption by self-regulation flow control, a simple spool valve, and efficient valve control to minimize throttling of the fluid flow. Yet a further advantage of the present invention is that the valve actuator assembly has uses one solenoid and one on/off valve. Still a further advantage of the present invention is that the valve actuator assembly has a relatively small size and is easy to package in an engine. Another advantage of the present invention is that the valve actuator assembly has a relatively low cost. Yet another advantage of the present invention is that the valve actuator assembly has improved output torque and built-in soft landing capability to reduce noise and improve durability. 
     Other objects, features, and advantages of the present invention will be readily appreciated, as the same becomes better understood, after reading the subsequent description taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagrammatic view of a valve actuator assembly, according to the present invention, illustrated in operational relationship with an engine of a vehicle. 
         FIG. 2  is a fragmentary view of the valve actuator assembly of  FIG. 1  in an engine valve closed position. 
         FIG. 3  is a view similar to  FIG. 2  illustrating the valve actuator assembly in an engine valve part opened position. 
         FIG. 4  is a view similar to  FIG. 2  illustrating the valve actuator assembly in an engine valve fully opened position. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings and in particular  FIG. 1 , one embodiment of a valve actuator assembly  10 , according to the present invention, is shown for an engine, generally indicated at  12 , of a vehicle (not shown). The engine  12  is of an internal combustion type. The engine  12  includes an engine block  14  having at least one opening  16  therein in communication with at least one internal combustion chamber (not shown). The engine  12  also includes a movable engine valve  18  for each opening  16 . The engine valve  18  has a valve stem  20  and a valve head  22  at one end of the valve stem  20 . The engine valve  18  is movable to open and close its respective opening  16  between an open position as illustrated in  FIGS. 3 and 4  and a closed position as illustrated in FIG.  2 . It should be appreciated that the engine valve  18  may be either an intake or exhaust valve. It should also be appreciated that the valve actuator assembly  10  is a camless valve train for the engine  12 . It should further be appreciated that, except for the valve actuator assembly  10 , the engine  12  is conventional and known in the art. 
     The valve actuator assembly  10  includes a valve housing  24  disposed adjacent the engine block  14 . The valve housing  24  has a first or primary fluid chamber  26  therein. The valve actuator assembly  10  also includes a piston  28  connected to or in contact with the engine valve  18  at the end of the valve stem  20  opposite the valve head  22 . The piston  28  is disposed in the primary fluid chamber  26  of the valve housing  24  and forms a second or secondary fluid chamber  30  therein. The valve actuator assembly  10  includes an engine valve spring  32  disposed about the valve stem  20  and contacting the engine block  14  to bias the engine valve  18  toward the closed position of FIG.  2 . It should be appreciated that the valve head  22  closes the opening  16  when the engine valve  18  is in the closed position. 
     The valve actuator assembly  10  also includes a spool valve  34  fluidly connected to the primary fluid chamber  26  and the secondary fluid chamber  30  of the valve housing  24 . The spool valve  34  is of a three-position three-way type. The spool valve  34  has a high pressure port  36  and a low pressure port  38 . The spool valve  34  also has a primary fluid chamber port  40  fluidly connected by a driving channel  42  to the primary fluid chamber  26  and a secondary fluid chamber port  44  fluidly connected by a feedback channel  46  to the secondary fluid chamber  30 . The spool valve  34  also has a third or tertiary fluid chamber  48  at one end thereof fluidly connected to the secondary fluid chamber port  44 . It should be appreciated that the spool valve  34  controls fluid flow with the primary fluid chamber  26 . 
     The valve actuator assembly  10  includes an actuator  50  at one end of the spool valve  34  opposite the fluid chamber  48 . The actuator  50  is of a linear type such as a solenoid electrically connected to a source of electrical power such as a controller  51 . The valve actuator assembly  10  further includes a spool valve spring  52  disposed in the tertiary fluid chamber  48  to bias the spool valve  34  toward the actuator  50 . It should be appreciated that the actuator  50  may be any suitable device that generates straight-line motion. It should also be appreciated that the controller  51  energizes and de-energizes the actuator  50  to move the spool valve  34 . 
     The valve actuator assembly  10  also includes a fluid pump  54  and a high pressure line  56  fluidly connected to the pump  54  and the high pressure port  36 . The valve actuator assembly  10  includes a fluid tank  58  and a low pressure line  60  fluidly connected to the tank  58  and the low pressure port  38 . It should be appreciated that the pump  54  may be fluidly connected to the tank  58  or a separate fluid tank  62 . 
     The valve actuator assembly  10  further includes an on/off valve  64  fluidly connected to the secondary fluid chamber  30  of the valve housing  24 . The on/off valve  64  is of a two-way magnetically latchable type and is electrically connected to a source of electrical power such as the controller  51 . The on/off valve  64  has a first port  66  and a second port  68 . The first port  66  is fluidly connected by a channel  70  to the secondary fluid chamber  30 . The valve actuator assembly  10  includes a fluid tank  72  fluidly connected to the second port  68  by a low pressure line  74 . It should be appreciated that the fluid tank  72  is a low pressure source. 
     In operation of the valve actuator assembly  10 , the engine valve  18  is shown in a closed position as illustrated in FIG.  2 . At the closed position of the engine valve  18 , the actuator  50  is de-energized by the controller  51  so that the spool valve spring  52  pushes the spool valve  34  upward and exposes the driving channel  42  to the low pressure line  60 . The primary fluid chamber  26  is then connected to the low pressure line  60  through the driving channel  42 . The engine valve spring  32  keeps the engine valve  18  closed with the valve head  22  closing the opening  16 . The on/off valve  64  is open so that both the secondary fluid chamber  30  and the tertiary fluid chamber  48  are exposed to the fluid tank  72 . 
     To open the engine valve  18 , the controller  51  energizes the actuator  50  and causes the actuator  50  to overcome the force of the spool valve spring  52  and drive the spool valve  34  downward. The driving-channel  42  is then exposed to the high pressure line  56  and the high pressure fluid flows into the primary fluid chamber  26 , which overcomes the force from the engine valve spring  32  and pushes the engine valve  18  open. The on/off valve  64  is open so that the secondary fluid chamber  30  and the tertiary fluid chamber  48  are exposed to the tank  72  as illustrated in FIG.  3 . It should be appreciated that, in  FIG. 3 , the engine valve  18  is illustrated in a valve part open position. 
     To stop the engine valve  18  at a predetermined lift position, the controller  51  energizes the on/off valve  64  and the on/off valve  64  is closed, cutting off the fluid connection between the secondary fluid chamber  30  and the fluid tank  72 . As the engine valve  18  continues to move downward, the piston  28  pushes the fluid in the secondary fluid chamber  30  via the feedback channel  46  into the tertiary fluid chamber  48 , which drives the spool valve  34  upward. This motion continues until the spool valve  34  cuts off the fluid connection between the driving channel  42  and both the high pressure line  56  and the low pressure line  60 . When the spool valve  34  reaches this equilibrium point, the engine valve  18  stops as illustrated in FIG.  4 . It should be appreciated that, in  FIG. 4 , the engine valve  18  is illustrated in a valve open position. 
     To close the engine valve  18 , the controller  51  de-energizes the actuator  50 . The spool valve spring  52  then pushes the spool valve  34  upward and exposes the driving channel  42  to the low pressure line  60 . The high pressure fluid in the primary fluid chamber  26  will exhaust into the low pressure line  60  and return to the fluid tank  58 . The engine valve spring  32  drives the engine valve  18  back such that the valve head  22  closes the opening  16  as illustrated in FIG.  2 . It should be appreciated that the on/off valve  64  is open so that the secondary fluid chamber  30  and tertiary fluid chamber  48  are connected to the fluid tank  72 , causing the low pressure fluid to fill those chambers while the engine valve  18  moves upward. It should also be appreciated that the spool valve spring  34  may be eliminated and the actuator  50  may be of push/pull type to connect the driving channel  42  to the low pressure line  60 . 
     The valve actuator assembly  10  of the present invention is made open-loop stable by utilizing the hydraulic feedback channel  46  and the on/off valve  64  is used to enable or disable the feedback channel  46 . Open-loop stability implies that a system&#39;s response to a given input signal is not unbounded. The better controllability achieved by open loop stability enables it to provide better performance. The valve actuator assembly  10  of the present invention precisely controls the motion of the spool valve  34  through the feedback channel  46  so that it avoids unnecessary throttling of the low pressure flow and high pressure flow, thereby providing energy consumption benefit. It should be appreciated that the tertiary fluid chamber  48  and the feedback channel  46  can also be located on top of the spool valve  34  so that soft seating of the valve head  22  of the engine valve  18  can be achieved by the hydraulic feedback. 
     The present invention has been described in an illustrative manner. It is to be understood that the terminology, which has been used, is intended to be in the nature of words of description rather than of limitation. 
     Many modifications and variations of the present invention are possible in light of the above teachings. Therefore, within the scope of the appended claims, the present invention may be practiced other than as specifically described.