Hydraulic lash adjuster

A hydraulic lash adjuster comprising:

• a cylindrical body having a central cylindrical bore, the cylindrical bore having a closed end;
• a first oil inlet passage through a side wall of the body into the bore;
• a hollow plunger reciprocable in the bore and having a reservoir chamber therein;
• a second oil inlet passage through a side wall of the plunger into the reservoir chamber;
• a high pressure chamber defined by the plunger and the closed end of the bore, the plunger having a close clearance with the bore to limit leakage of oil from the high pressure chamber;
• a plunger wall having an orifice separating the reservoir chamber from the high pressure chamber;
• a check valve operative to allow flow of oil through the orifice from the reservoir chamber to the high pressure chamber and to prevent flow of oil from the high pressure chamber to the reservoir chamber;
• a plunger spring disposed in the high pressure chamber urging the plunger away from the closed end of the bore;
• the plunger having an end distal from the high pressure chamber;
• and
• a circumferential external groove around the plunger proximate the plunger distal end and spaced between the first and second oil inlet passages and the plunger distal end, the circumferential groove configured to hold oil for maintaining an oil seal in the clearance to prevent passage of air through the clearance.

A hydraulic lash adjuster comprising:

• a cylindrical body having a central cylindrical bore, the cylindrical bore having a closed end;
• a hollow plunger reciprocable in the bore and having a reservoir chamber therein;
• a high pressure chamber defined by the plunger and the closed end of the bore, the plunger having a close clearance with the bore to limit leakage of oil from the high pressure chamber;
• a plunger wall having an orifice separating the reservoir chamber from the high pressure chamber;
• a check valve to allow flow of oil through the orifice from the reservoir chamber to the high pressure chamber and to prevent flow of oil from the high pressure chamber to the reservoir chamber;
• plunger spring disposed in the high pressure chamber urging the plunger away from the closed end of the bore;
• a seat disposed at an end of the plunger distal from the high pressure chamber;
• a circumferential external groove around the plunger proximate the seat;
• and
• a seal ring disposed in the groove for temporarily sealing the clearance.