Cam-Driven Hydraulic Lost-Motion Mechanisms for Overhead Cam and Overhead Valve Valvetrains
A valve operating system includes a cam and a roller follower. An input piston is spring-biased to follow motion of the roller follower. A hydraulic chamber filled with fluid selectively transfers motion from the input piston to an output piston operatively engaged with a poppet valve. A variable-bleed valve is in fluid communication with the hydraulic chamber and an outlet channel and configured to selectively vary a bleed rate between the hydraulic chamber and outlet channel. Displacement of the input piston into the hydraulic chamber causes movement of the output piston, depending on the bleed rate. A pushrod may transfer motion from the roller follower to the input piston. A hydraulic damping shoulder may restrict the closing velocity of the output piston. The system may be further characterized by an absence of a rocker arm. An auxiliary piston may replace the variable-bleed orifice in the lost-motion hydraulic linkage.
1 . A valve operating system for an internal combustion engine comprising:
a cam;
a roller follower configured to follow motion of said cam san input piston spring-biased to follow motion of said roller follower;
an output piston operatively engaged with a poppet valve for opening said poppet valve;
a hydraulic chamber filled with a fluid; and
a variable-bleed valve in fluid communication with said hydraulic chamber and an outlet channel, wherein said variable-bleed valve is configured to selectively vary a bleed rate between said hydraulic chamber and said outlet channel;
wherein said input piston, output piston and variable-bleed valve are in fluid communication with said fluid in said hydraulic chamber, such that displacement of said input piston into said hydraulic chamber causes a proportional displacement of said output piston, and said proportional displacement of said output piston is dependent on said bleed rate.
2 . The valve operating system of claim 1 , further comprising
an end-pivoted finger carrying said roller follower, wherein said end-pivoted finger has a first end configured to transfer motion of said end-pivoted finger to said input piston; and
a lash adjuster pivotably attached to a second end of said end-pivoted finger;
wherein said roller follower is disposed between said first end and second end, such that the motion of said cam is proportionally transferred to said input piston.
3 . The valve operating system of claim 2 , wherein said lash adjuster is a mechanical lash adjuster.
4 . The valve operating system of claim 2 , wherein said cam is an overhead cam.
5 . The valve operating system of claim 1 , further comprising:
a center-pivoted finger carrying said roller follower, wherein said center-pivoted finger has a first end configured to transfer motion of said center-pivoted finger to said input piston and said roller follower is disposed on a second end; and
a pivot member disposed between said first end and said second end, such that the direction of motion of said cam is changed as motion is transferred through said center-pivoted finger to said input piston.
6 . The valve operating system of claim 5 , wherein said cam is an overhead cam.
7 . The valve operating system of claim 1 , further comprising a pushrod interposed between said roller follower and said input piston, such that motion of said cam is transferred through said pushrod to said input piston.
8 . The valve operating system of claim 7 , further comprising:
a valve spring biasing said output piston toward a closed position; and
a hydraulic damping shoulder interposed between said output piston and said hydraulic chamber, wherein said hydraulic damping shoulder is configured to restrict the velocity of said output piston in proximity to said closed position.
9 . The valve operating system of claim 8 , further comprising a pressure accumulator in fluid communication with said outlet channel.
10 . The valve operating system of claim 7 , further characterized by an absence of a rocker arm.
11 . An internal combustion engine valve operating system comprising:
a cam;
a roller follower configured to follow motion of said cam;
an input piston spring-biased to follow motion of said roller follower;
an output piston operatively engaged with a poppet valve for opening said poppet valve;
a hydraulic chamber filled with a fluid; and
an auxiliary piston in fluid communication with said hydraulic chamber and movable with respect to an adjustable stop member;
wherein said input piston, output piston and auxiliary piston are in fluid communication with said fluid in said hydraulic chamber, such that displacement of said input piston into said hydraulic chamber causes movement of said output piston and/or said auxiliary piston, depending on the adjusted position of said adjustable stop member, while the volume of fluid in said control chamber remains substantially constant.
12 . The valve operating system of claim 11 , further comprising a pushrod interposed between said roller follower and said input piston, such that motion of said cam is transferred through said pushrod to said input piston.
13 . The valve operating system of claim 12 , further characterized by an absence of a rocker arm.
14 . The valve operating system of claim 13 , further comprising:
a valve spring biasing said output piston toward a closed position; and
a hydraulic damping shoulder interposed between said output piston and said hydraulic chamber, wherein said hydraulic damping shoulder is configured to restrict the velocity of said output piston in proximity to said closed position.
15 . The valve operating system of claim 14 , further comprising a pressure accumulator in fluid communication with said outlet channel.