GM patents rocker-shaft cylinder deactivation for pushrod engines

Today’s Daily Planet by Planet X Performance

GM just patented a way to shut off cylinders at the rocker arm instead of collapsing the lifter. U.S. Patent 12,742,403 B2, assigned to GM Global Technology Operations and granted Sept. 22, covers pushrod engines with the cam in the block. Cylinder deactivation turns off some cylinders on light throttle so the engine burns less fuel.

On a pushrod engine, the cam lobe pushes a lifter, the lifter pushes a pushrod, and the pushrod tips a rocker arm that opens the valve. Today’s AFM and DFM systems, Active Fuel Management and Dynamic Fuel Management, unlock special lifters so selected valves stay closed. Collapsed or stuck AFM/DFM lifters are a well-documented service issue on Gen IV and Gen V small-blocks.

This patent takes a different path. Oil runs through a hollow rocker shaft and an insert sleeve to an oil-control valve on the shaft, which pressurizes a spring-lock unit at the pushrod end of the rocker. That unlocks so the rocker no longer lifts the valve, while the cam and pushrod keep moving. In plain terms, the rocker stops transferring the pushrod’s motion to the valve.

This is a granted patent, not a confirmed production part. The filing does not name an LS, LT, Gen 5, Gen 6, Corvette or truck engine that will use it.

Bare LS6 engine on GM's Flint factory assembly line — Image: U.S. Patent 12,742,403 B2 (GM); Photo: General Motors

Patent FIG. 1 cross-section of a V-engine pushrod valvetrain from U.S. Patent 12,742,403 B2 — Image: U.S. Patent 12,742,403 B2 (GM); Photo: General Motors

Would you rather see cylinder deactivation leave the lifter alone and work at the rocker instead?

Sources

Images: U.S. Patent 12,742,403 B2 (GM); Photo: General Motors