Eaton Show Hydraulic Lash Adjuster in Medium and Heavy Duty Engines

The HLA automatically controls valve clearance throughout the engine’s lifetime and eliminates the need to periodically shim the valves. The technology, also known as a hydraulic valve lifter has been successfully used in passenger cars since the 1950s. Eaton as the worldwide leader in valves and valvetrain technologies has identified a strong market potential for HLA technology in commercial vehicles. Eaton is currently producing and supplying the HLA for a major European heavy-duty engine manufacturer. Several other medium- and heavy-duty OEMs are currently evaluating the technology for potential applications in their engines and vehicle models. The HLA is particularly suited for use in on-highway trucks, construction and agriculture vehicles. 

“The Hydraulic Lash Adjuster for medium- and heavy-duty truck engines is Eaton’s answer to the increasingly strict emission requirements for truck and industrial diesel engines. Today’s newly required and increasingly complex exhaust gas after-treatment systems are frequently installed on top of the engine. This set-up complicates service access to valvetrain components and makes the manual valve adjustment even more time and cost intensive. With our HLA we eliminate the need to adjust the valve, reducing both the engine assembly effort for the vehicle manufacturer and the maintenance cost and vehicle downtime for the operator,” said Carlo Ghirardo, vice president and general manager, Eaton Global Valvetrain Business. “That is why we see strong market potential for our HLA technology, especially in the European market.”

HLA reduces engine assembly costs because no initial valve lash setting is needed, and it improves packaging flexibility as the need for service access is eliminated. Furthermore, it reduces truck downtime as well as maintenance costs by eliminating the need to periodically adjust (shim) the valves, thus lowering the cost of ownership. In addition, by compensating for thermal elongation and wear rate, the HLA ensures a precise valve event independent of engine temperature delivering more consistent engine performance and combustion. Additionally, it improves noise, vibration and harshness (NVH) characteristics by reducing noise levels thanks to smoother and better controlled valve closing. 

HLA is installed between the camshaft and engine valve, controlling valve opening and closing processes. It consists of a plunger sliding inside a cylindrical body filled with engine oil, and a spring to maintain contact with the camshaft, compensating all gaps within the valve train. When the engine valve is closed the system is fed with engine oil, expanding the whole piston to compensate for any clearance. As the turning camshaft exerts a high force on the HLA, a ball check valve blocks the oil feed. The HLA leaks oil only in very small and tightly controlled quantities, creating a temporarily solid HLA acting on the valve and controlling its motion. Balancing the amount of oil leaking out during valve lift and the amount of oil replenished once the valve is closed, the HLA compensates for thermal elongations created in the valvetrain so that gas exchange happens as intended through the entire lifetime of the engine.