Development of a switching roller finger follower for cylinder deactivation in internal combustion engines
A rocker arm includes an outer arm having a first side and a second side, an inner arm positioned between the first side and the second side of the outer arm, a pivot axle pivotally coupling the inner arm to the outer arm at a first end of the inner arm and a first end of the outer arm, and a latch pin having a first position and a second position. The latch pin in the first position pivotally fixes the inner arm to the outer arm at a second end of each of the inner arm and a second end of the outer arm, and in the second position allows the inner arm and the outer arm to pivot independently. Two lost motion springs are respectively secured to mounts provided on the outer arm.
1. A rocker arm, comprising:
an outer arm comprising a first side and a second side;
an inner arm disposed between the first side and the second side of the outer arm;
a pivot axle pivotally coupling the inner arm to the outer arm at a first end of the inner arm and a first end of the outer arm;
a latch pin including a first position and a second position, the latch pin configured to:
in the first position pivotally fix the inner arm to the outer arm at a second end of the inner arm and a second end of the outer arm; and
in the second position, enable the inner arm to pivot independently of the outer arm;
a first biasing member urging the latch pin into one of the first position and the second position, a hydraulic fluid passage hydraulically coupled to the latch pin; and
two lost motion springs respectively secured to a mount on each of the first and second sides of the outer arm, each lost motion spring including coils with a trapezoidal cross-sectional shape arranged such that elongated sides of each coil rest against elongated sides of adjacent coils so as to stabilize the respective lost motion spring by holding each coil in an upright position, thereby preventing the coils from angling or passing over each other when subjected to torsional loading,
wherein the latch pin is responsive to hydraulic pressure in the hydraulic fluid passage so as to selectively switch between the first position and the second position,
wherein the inner arm comprises an inner arm sloped surface, and
wherein the latch pin comprises a latch pin sloped surface.
2. The rocker arm of claim 1 , wherein the inner arm sloped surface and the latch pin sloped surface are structured to provide a smooth latch movement when the inner arm sloped surface contacts the latch pin sloped surface.
3. The rocker arm of claim 1 , wherein for each lost motion spring:
a spring retainer secures the lost motion spring to the mount, the spring retainer comprising an aperture and a flange;
the aperture extends through a coil of the lost motion spring and over the mount; and
the flange rests against the coil.
4. The rocker arm of claim 1 , wherein:
the outer arm further comprises:
a first over-travel limiter on the first side; and
a second over-travel limiter on the second side; and
the first and second over-travel limiters are structured to contact the inner arm and prevent rotation of the outer arm.
5. The rocker arm of claim 1 , wherein:
the first side and the second side of the outer arm each comprise a slider pad configured to engage a low lift cam.
6. The rocker arm of claim 1 , further comprising a bearing axle mechanically coupled to one of the inner arm and the outer arm, the bearing axle including a bearing roller configured to engage a low lift cam.
7. The rocker arm of claim 6 , wherein:
one of the inner arm and the outer arm is a high lift arm including a slider pad engagement surface for the low lift cam; and
a remaining one of the inner arm and the outer arm is a low lift arm mechanically coupled to the bearing axle.
8. The rocker arm of claim 1 , wherein:
one of the inner arm and the outer arm is a high lift arm including a slider pad engagement surface for a high lift cam; and
a remaining one of the inner arm and the outer arm is a low lift arm including a roller bearing engagement for a low lift cam.
9. The rocker arm of claim 1 , wherein:
the inner arm further comprises an arcuate latch seat configured to engage a horizontal flat surface of the latch pin when in the first position so as to pivotally fix the inner arm to the outer arm.
10. The rocker arm of claim 1 , wherein a vertically-oriented flat surface of the inner arm is configured to contact an end of the latch pin so as to restrict the latch pin from moving to the first position.
11. The rocker arm of claim 1 , wherein:
the inner arm further comprises an engagement slot;
the latch pin in the first position extends into the engagement slot; and
the engagement slot and the latch pin have a contact position only on a vertically upward side of the latch pin.
12. The rocker arm of claim 1 , wherein the latch pin further comprises a dual diameter pin assembled into a sleeve so as to form a chamber.
13. The rocker arm of claim 1 , further comprising a lubricant hole structured to allow oil to escape to an engine.
14. The rocker arm of claim 1 , wherein the latch pin further comprises a latch spring retainer with a vent hole.
15. The rocker arm of claim 1 , wherein the outer arm further comprises a latch bore.
16. The rocker arm of claim 15 , wherein the latch pin is at least partially positioned within the latch bore.
17. The rocker arm of claim 1 , further comprising a hydraulic lash adjuster fluidly coupled to the hydraulic fluid passage and mechanically coupled to the outer arm.
18. The rocker arm of claim 17 , wherein the hydraulic lash adjuster is a dual feed hydraulic lash adjuster.
19. The rocker arm of claim 1 , wherein the two lost motion springs are structured to bias a position of the inner arm.
20. The rocker arm of claim 1 , wherein the latch pin further comprises a bottom surface in direct contact with the latch pin sloped surface.