Adjustment mechanism for valves

Abstract

An apparatus for varying the motion characteristics of a valve typically in an engine includes a rotating member such as a valve crank shaft having a conrod with a sliding pin. The sliding pin is constrained to move along a path in a guide member. The guide member is adjustably attached to the engine, and by adjusting the position of the guide member, the trajectory taken by the pin can be varied. The pin also moves along a path of a pivotally attached rocker arm, the path of the rocker arm being different to the path of the guide member. The difference in the paths causes the rocker arm to pivot, and this in turn causes motion in a valve in contact with the end of the rocker arm. By moving the guide member, the differences in the path of the guide member and rocker arm can be accentuated or minimised, thereby altering the motion characteristics of the rocker arm and in turn the valve. This enables the valve opening duration and/or valve lift to be varied. The valve may be fixed to the end of the valve to allow for desmodromic valve actuation, or the valve may include a spring to keep the valve stem in contact with the rocker arm. In one embodiment the rocker arm has an actuator having contact surfaces on the valve which are of substantially constant diameter, in order for the valve clearance to be kept constant as the rocker arm pivots to open and close the valve. An apparatus for adjusting the valve clearance on the above device, including a valve stem having a thread is also disclosed.

The claims defining the invention are as follows:  
     
         1 . An apparatus for adjusting the motion characteristics of a valve over a range of opening and closing angles including a member in communication with a valve actuator, wherein the member travels along a non-straight path in a guide, and the position of the guide is varied to adjust the direction of motion of the member.  
     
     
         2 . The apparatus of  claim 1  wherein the valve actuator is a pivotally located arm.  
     
     
         3 . The apparatus of claims  1  or  2  wherein the guide includes a plate having a non-straight path.  
     
     
         4 . The apparatus of any one of  claims 1  to  3 , wherein at least  3  different opening and closing angles are able to be selected over a range of engine speed.  
     
     
         5 . An apparatus for adjusting the motion characteristics of a valve, including adjustment means to adjust the valve motion including an adjustment member and a guide member, the guide member moving along a first guide path in the adjustment member and along a second guide path in a valve actuator, wherein the first guide path and the second guide path are not collinear, and the guide member moving along the first and second guide paths causes the valve actuator to move relative to the adjustment member due to the differences in these paths.  
     
     
         6 . An apparatus as claimed in  claim 5 , wherein the valve actuator includes a rocker arm rotatably mounted around a point, the adjustment member includes a guide plate adjustable in relation to that point, and an actuation means for moving the guide member along the second guide path in the rocker arm and the first guide path in the guide plate wherein differences in the first and second guide paths are reduced when the guide plate is in a first position, compared to the differences in the guide paths when the guide plate is in a second position.  
     
     
         7 . Apparatus for adjusting the motion characteristics of a valve including an adjustment means having a plate having a guide path.  
     
     
         8 . The apparatus of  claim 7  including a valve actuator having a guide path different from the guide path of the adjustment means.  
     
     
         9 . The apparatus of  claim 8 , wherein the amount of non-alignment of the guide path of the adjustment means and the guide path of the valve actuator determines the motion characteristics of the valve actuator.  
     
     
         10 . The apparatus of  claim 9 , wherein varying the position of the adjustment means changes the alignment between the guide path of the adjustment means and the guide path of the valve actuator thus adjusting the motion characteristics of the valve.  
     
     
         11 . An apparatus for adjusting the motion characteristics of a valve including a first guide path and a second guide path wherein the motion characteristics of the valve are determined by differences in shape and/or alignment between the first and second guide paths.  
     
     
         12 . The apparatus of  claim 11 , wherein the first guide path is located in an adjustment member, which moves relative to a valve actuator to alter the differences between the shape and/or alignment of the first and second guide paths.  
     
     
         13 . An apparatus for adjusting the motion characteristics of a valve including an adjustment means operatively situated between a valve actuation means and the valve, having an adjustment member with a guide path adapted to receive a guide member, the adjustment member being moveable between a first position and a second position, wherein the guide member travelling along the guide path of the adjustment member has a different trajectory when the adjustment member is in the first position than when the adjustment member is in the second position.  
     
     
         14 . The apparatus of  claim 13  wherein the valve actuation means includes the means for determining the base timing of the valve actuation.  
     
     
         15 . The apparatus of  claim 13  or  14  where the guide member moves cyclicly.  
     
     
         16 . The apparatus of any one of  claims 13  to  15  where the position of the adjustment member can be varied over a given range of engine speeds.  
     
     
         17 . The apparatus of any one of  claims 13  to  16  where the position of the adjustment member can be varied over a given range of engine loads.  
     
     
         18 . An apparatus for adjusting the motion characteristics of a valve including an adjustment member having a first guide path, a valve actuator having a second guide path, wherein the adjustment member moves relative to the valve actuator, thus modifying the motion of the guide member moving along the first and second guide paths which also modifies the motion of the guide element.  
     
     
         19 . The apparatus of  claim 18  wherein the adjustment member and valve actuator include plates.  
     
     
         20 . The apparatus of any one of the preceding claims wherein an adjustment mechanism does not have its base timing varied.  
     
     
         21 . The apparatus of any of  claims 13  to  15  wherein the guide element is pivotally located.  
     
     
         22 . The apparatus of any one of the preceding claims wherein the adjustment member is slidably located with respect to the pivot point of the guide element.  
     
     
         23 . The apparatus of any one of the preceding claims, wherein the motion characteristics of an inlet valve are variable independently of the motion characteristics of the exhaust valve.