Switchable rocker arm

Abstract

A latching mechanism for variably activating an engine valve in an internal combustion engine includes a rocker arm body having a bore and a socket. A first passage leads from the socket to a first hydraulic chamber formed above a lock pin head. A second passage leads from the socket to a second hydraulic chamber formed below the lock pin head. Since both the first and the second hydraulic chamber receive pressurized oil, it is the diameter of the pin shank that determines the hydraulic force needed to axially move the locking pin to an extended position and into a locking engagement with a slider member. In an alternate embodiment of the invention the first passage connecting the first hydraulic chamber with the socket is eliminated and instead the locking pin is modified to permit flow between second hydraulic chamber and first hydraulic chamber.

1 . A latching mechanism for variably activating an engine valve in an internal combustion engine, comprising:
 a body including a bore and a variable oil pressure source;   a locking pin including a pin head axially disposed in said bore;   a first hydraulic chamber formed above said pin head;   a second hydraulic chamber formed below said pin head;   a first passage connecting said first hydraulic chamber with said variable oil pressure source; and   a second passage connecting said second hydraulic chamber with said variable oil pressure source.   
   
   
       2 . The latching mechanism of  claim 1 , wherein said locking pin further includes a pin shank that extends from said pin head towards said second hydraulic chamber, and wherein said pin shank has a smaller diameter than said pin head. 
   
   
       3 . The latching mechanism of  claim 2 , further comprising a return spring received by said pin shank, wherein said locking pin is biased in said bore by said return spring. 
   
   
       4 . The latching mechanism of  claim 1 , further comprising a plug disposed in said bore, wherein said plug seals said bore and restricts movement of said locking pin. 
   
   
       5 . The latching mechanism of  claim 1 , wherein said variable oil pressure source receives a hydraulic lash adjuster, wherein said first hydraulic chamber receives pressurized oil from said hydraulic lash adjuster via said first passage while said second hydraulic chamber discharges oil via said second passage concurrently, or wherein said second hydraulic chamber receives pressurized oil from said hydraulic lash adjuster via said second passage while said first hydraulic chamber discharges oil via said first passage concurrently. 
   
   
       6 . The latching mechanism of  claim 1 , wherein a hydraulic force of pressurized oil received by said first hydraulic chamber and said second hydraulic chamber overcomes a counter-bias force of said return spring and biases said locking pin to an extended position, where a portion of said locking pin positioned opposite from said pin head axially extends beyond said bore. 
   
   
       7 . The latching mechanism of  claim 6 , wherein said hydraulic force axially urges said locking pin into a locking engagement with a slider member activating said engine valve. 
   
   
       8 . The latching mechanism of  claim 6 , wherein said diameter of said pin shank determines said hydraulic force that overcomes said counter-bias force of said return spring and a net volume of oil displaced by motion of said locking pin. 
   
   
       9 . The latching mechanism of  claim 1 , wherein oil enters and exits said first hydraulic chamber via said first passage, wherein oil enters and exits said second hydraulic chamber via said second passage, and wherein compressed oil leaks through a clearance between said pin head and said bore. 
   
   
       10 . The latching mechanism of  claim 1 , wherein a cavity housing a return spring forms said second hydraulic chamber. 
   
   
       11 . A latching mechanism for variably activating an engine valve in an internal combustion engine, comprising:
 a body including a bore and a variable oil pressure source;   a locking pin axially disposed in said bore, said locking pin including a pin head, a pin shank, and an oil passage;   a first hydraulic chamber formed above said pin head;   a second hydraulic chamber formed below said pin head; and   a passage connecting said second hydraulic chamber with said variable oil pressure source;   wherein said oil passage of said locking pin connect said second hydraulic chamber with said first hydraulic chamber.   
   
   
       12 . The latching mechanism of  claim 11 , wherein said oil passage of said locking pin includes an axial hole extending through said pin head and intersecting with a cross hole extending through said pin shank. 
   
   
       13 . The latching mechanism of  claim 11 , wherein said oil passage of said locking pin includes slots or grooves disposed on an outside diameter of said pin head. 
   
   
       14 . The latching mechanism of  claim 11 , wherein pressurized oil is supplied to said second hydraulic chamber from said variable oil pressure source via said passage, and wherein said pressurized oil is supplied from said second hydraulic chamber to said first hydraulic chamber via said oil passage of said locking pin. 
   
   
       15 . The latching mechanism of  claim 11 , wherein oil flows from said first hydraulic chamber into said second hydraulic chamber via said oil passage of said locking pin, and wherein said oil flows from said second hydraulic chamber into said socket via said passage. 
   
   
       16 . The latching mechanism of  claim 11 , wherein pressurized oil supplied to said second hydraulic chamber via said passage and supplied to said first hydraulic chamber via said oil passage of said locking pin creates a hydraulic force that overcomes the force of a return spring and urges said locking pin axially into a locking engagement with a slider member for activating said engine valve. 
   
   
       17 . A two-step finger follower rocker arm assembly for variably activating an engine valve in an internal combustion engine, comprising:
 a rocker arm body having a bore;   a locking pin axially disposed in said bore;   a first hydraulic chamber formed in said bore, wherein oil flows into and out of said first hydraulic chamber via a first passage; and   a second hydraulic chamber formed in said bore, wherein oil flows into and out of said second hydraulic chamber via a second passage;   wherein pressurized oil supplied to said first hydraulic chamber and said second hydraulic chamber moves said locking pin to an extended position for selectively latching a slider member to said body to provide a first rocker assembly mode having a first valve lift capability; and   wherein a return spring moves said locking pin to a retracted position for unlatching said slider member from said body to provide a second rocker assembly mode having a second valve lift capability.   
   
   
       18 . The rocker arm assembly of  claim 17 , wherein said first passage connects said first hydraulic chamber with a variable oil pressure source. 
   
   
       19 . The rocker arm assembly of  claim 18 , wherein said variable oil pressure source receives a hydraulic lash adjuster. 
   
   
       20 . The rocker arm assembly of  claim 17 , wherein said first passage is an oil passage integrated in said locking pin, and wherein said oil passage connects said first hydraulic chamber with said second hydraulic chamber. 
   
   
       21 . The rocker arm assembly of  claim 18 , wherein said second passage connects said second hydraulic chamber with the variable oil pressure source. 
   
   
       22 . The rocker arm assembly of  claim 17 , wherein said locking pin includes a pin head and a pin shank having a smaller diameter than said pin head, wherein said pressurized oil generates a hydraulic force, and wherein said diameter of said pin shank determines the hydraulic force needed to move said locking pin to said extended position. 
   
   
       23 . A method for providing a hydraulic force to a latching mechanism of a rocker arm assembly for variably activating an engine valve in an internal combustion engine, comprising the steps of:
 axially disposing a locking pin having a pin shank and a pin head in a bore of a rocker arm body;   supplying pressurized oil via a first passage to a first hydraulic chamber;   discharging pressurized oil via a second passage from a second hydraulic chamber, and   determining a hydraulic force needed to overcome a counter force and to move said locking pin to an position where a portion of said pin shank extends from said bore based on a diameter of said pin shank, wherein said diameter of said pin shank is smaller than the diameter of said pin head.   
   
   
       24 . The method of  claim 23 , further including the steps of:
 integrating said first passage into said locking pin to form an internal passage;   connecting said second hydraulic chamber with a variable oil pressure source via said second passage; and   providing communication between said second hydraulic chamber and said first hydraulic chamber via said locking pin oil passage.   
   
   
       25 . The method of  claim 23 , further including the steps of:
 connecting said first hydraulic chamber with a variable oil pressure source via said first passage, and   connecting said second hydraulic chamber with said variable oil pressure source via said second passage.