Hydraulic lash adjuster

A hydraulic lash adjuster for an engine valve train, the hydraulic lash adjuster comprising:

• a hydraulic lash adjusting arrangement configured to automatically compensate for lash in the engine valve train, the hydraulic lash adjusting arrangement comprising:
• a first chamber configured to contain hydraulic fluid;
• a second chamber configured to contain hydraulic fluid, the second chamber being located above the first chamber;
• a third chamber configured to contain hydraulic fluid, the third chamber being located above the second chamber;
• a first body;
• a second body disposed for sliding reciprocal movement within the first body;
• a first valve between the first chamber and the second chamber, the first valve comprising a ball captured by a cage;
• and
• a third body disposed for sliding reciprocal movement within the second body;
• a lost motion arrangement configured to inhibit motion, induced in the engine valve train in response to a lift profile of a rotating cam, from being transferred to an engine valve, the lost motion arrangement comprising:
• the second body;
• and
• the third body;
• and
• a relief valve configured to open an aperture into the second chamber, the relief valve extending along a central axis of the second chamber, the central axis extending axially through the aperture, the relief valve comprising an elongate stem or needle that extends along a longitudinal axis of the third chamber and through an upper wall of the hydraulic lash adjuster,
• wherein the first, second and third bodies are configured so that a displacement of hydraulic fluid in the first chamber resulting from a relative movement between the second body with respect to the first body results in a pressure difference between the first chamber and the second chamber so as to move the third body, inhibiting motion induced in the engine valve train in response to the lift profile of the rotating cam from being transferred to the engine valve, and
• wherein the first chamber comprises a space defined by the first body, the second body, and the third body.