Cylinder deactivation apparatus

Apparatus for selectively deactivating valves for specified cylinders of an engine, said apparatus comprising:

• switchable hydraulic lash adjusters forming part of a valve train for actuating engine valves of the specified cylinders, the lash adjusters having lash adjusting portions for adjusting valve lash and adjacent switching portions operative to selectively actuate or release their respective valves in response to an increase or decrease of oil pressure supplied to the switching portions;
• a gallery carrying said lash adjusters and including pressure oil passages connecting with the lash adjusting portions;
• a pressure oil supply connected with said pressure oil passages;
• at least one restricted passage connecting the pressure oil passages with the switching portions of the lash adjusters;
• and
• control passages connecting the switching portions of the lash adjusters with a control valve having a closed position cutting off flow and an open position allowing free flow through the control passages;
• the restricted passage limiting oil flow to the control passages, when the control valve is open, to a rate operative to maintain pressure below that required to actuate the switching portions to release their respective valves but to permit oil flow adequate to purge gaseous vapor from the control passages;
• whereby closing of the control valve increases pressure in the control passages to actuate the switching portions to deactivate their respective valves and opening of the control valve reduces pressure in the exhaust passages to re-engage the switching portions and reactivate their respective valves.