Method and apparatus for controlling a switchable cam follower

Abstract

An internal combustion engine is equipped to supply the camshaft bearings with pressurized oil via a first dedicated oil gallery independently of the hydraulic lash adjusters (HLAs) and any valve deactivation devices which are supplied from a second dedicated oil gallery. The galleries may be connected at their downstream ends and a flow restriction is placed in a connecting passage or within each HLA. An improved HLA is similar to a prior art HLA except that the prior art annular oil distribution groove in the outer surface of the HLA body is eliminated to prevent communication of the primary engine oil gallery with the HLA. The secondary gallery is formed remotely from the first oil gallery in the HLA residence bore in the engine, and the HLA is prevented from rotating within the residence bore.

1 . In an internal combustion engine having at least one camshaft bearing, at least one hydraulic lash adjuster disposed in a residence bore formed in said engine, and at least one switchable cam follower actuated by hydraulic fluid fed from the hydraulic lash adjuster, a system for controllably supplying hydraulic fluid to the camshaft bearing and to the hydraulic lash adjuster, comprising:
 a) a first hydraulic gallery in said engine for supplying said hydraulic fluid at a first pressure from a pressurized source to said camshaft bearing;   b) a second hydraulic gallery in said engine for supplying said hydraulic fluid at a second pressure from said pressurized source to said hydraulic lash adjuster.   c) a valve for variably connecting said second hydraulic gallery to said pressurized source; and   d) a fluid connector in fluid communication with said first and second hydraulic galleries, said connector including a flow-restricting orifice,   wherein said first and second hydraulic galleries are independently disposed on sides of said residence bore, and   wherein said hydraulic lash adjuster includes a hydraulic lash adjuster mechanism, said lash adjuster further comprising a low pressure chamber in fluid communication with the hydraulic lash adjuster mechanism and the switchable cam follower.   
   
   
       2 . A system in accordance with  claim 1  wherein said valve is a three-way on/off valve. 
   
   
       3 . A system in accordance with  claim 2  further comprising a pressure relief valve in fluid communication with said three-way on/off valve for selective connection to said second hydraulic gallery. 
   
   
       4 . A system in accordance with  claim 3  wherein a first position of said three-way on/off valve prohibits flow of said hydraulic fluid from said pressurized source through said valve to said second hydraulic gallery, and wherein a second position of said three-way on/off valve permits flow of said hydraulic fluid from said pressurized source through said valve to said second hydraulic gallery. 
   
   
       5 . A system in accordance with  claim 1  wherein said hydraulic fluid is engine oil supplied from an engine sump. 
   
   
       6 . A system in accordance with  claim 1  wherein said fluid connecting passage is connected between the distal ends of said first and second hydraulic galleries. 
   
   
       7 . A system in accordance with  claim 1  wherein said flow-restricting orifice is formed in a body of said hydraulic lash adjuster. 
   
   
       8 . A system in accordance with  claim 7  wherein the first gallery intersects the resident bore and is in flow communication with said low pressure chamber through said orifice. 
   
   
       9 . A system in accordance with  claim 1  wherein said flow-restricting orifice is disposed in a connecting passage, said connecting passage connecting said first and second hydraulic galleries. 
   
   
       10 . A system in accordance with  claim 1  wherein said hydraulic lash adjuster includes a body having a cylindrical outer surface unfeatured by an annular groove. 
   
   
       11 . A system in accordance with  claim 8  wherein one of said hydraulic lash adjuster or said resident bore includes an anti-rotation feature whereby axial rotation of said body relative to said resident bore is limited. 
   
   
       12 . A multiple-cylinder internal combustion engine comprising:
 a) at least one camshaft bearing;   b) at least one hydraulic lash adjuster disposed in a residence bore formed in said engine;   c) at least one switchable cam follower actuated by hydraulic fluid fed from said hydraulic lash adjuster; and   d) a system for controllably supplying hydraulic fluid to said camshaft bearing and to said hydraulic lash adjuster, including
 a first hydraulic gallery in said engine for supplying said hydraulic fluid from a pressurized source to said camshaft bearing; 
 a second hydraulic gallery in said engine for supplying said hydraulic fluid from said pressurized source to said hydraulic lash adjuster. 
 a valve for variably connecting said second hydraulic gallery to said pressurized source; and 
 a fluid connector in fluid communication with said first and second hydraulic galleries, said connector including a flow-restricting orifice, 
 wherein said first and second hydraulic galleries are independently disposed on sides of said residence bore, and 
 wherein said hydraulic lash adjuster includes a hydraulic lash adjuster mechanism, said lash adjuster further comprising a low pressure chamber in fluid communication with the hydraulic lash adjuster mechanism and the switchable cam follower.