Direct-acting type valve lifter for internal-combustion engines

Abstract

Objects: To provide a direct-acting type valve lifter that is simple in structure, involves a small number of components, and is capable of switching its valve lift between a high and a low lift. Means for Carrying Out the Invention: The valve lifter is mounted between a cam unit ( 20 ) and a valve stem ( 15 ). The cam unit ( 20 ) comprises a high-lift cam ( 22 ) and a low-lift cam ( 24 ) integrated to the high-lift cam. The valve lifter ( 30 ) is equipped with a side lifter ( 32 ) for slidably lifting the low-lift cams ( 24 ), a center lifter ( 40 ) for slidably lifting the high-lift cam, and hydraulic means (oil groove) ( 11 b ) for sliding the center lifter ( 40 ) so as to switch the valve lift in two levels, i.e. to switch between a high and a low lift. A cylindrical body of the valve lifter is provided on the top end thereof with a slit ( 33 ) for allowing the high-lift cam to freely rotate therein, and with sliding surfaces ( 32 a ) serving as a side lifter ( 32 ) to be in sliding contact with the low lift cam. Formed in the body of the valve lifter (lifter body) is a through-hole 34 perpendicular to the slit ( 33 ), which accommodate therein the piston type center lifter ( 40 ) such that the center lifter ( 40 ) can be slidably moved by a hydraulic pressure. When the center lifter ( 40 ) is located at a position aligned with the slit ( 33 ), the cam unit assumes a high lift mode. On the other hand, at a position well offset from the slit ( 33 ), the cam unit assumes a low lift mode. Thus, the valve lifter of the invention is composed of a small number of components, so that dimension tolerance demanded for the respective components are much relaxed, which permits easy assembly of the parts.

1 . A cylindrical direct acting type valve lifter for use with an internal-combustion engine, provided between the cam unit and the valve stem constituting a valve mechanism of said internal combustion engine, said cam unit formed of a high-lift cam (center cam) and a pair of low-lift cams integral with said high-lift cam, and said valve lifter having: a side lifter that can be in sliding contact with said low-lift cams; a center lifter that can be in sliding contact with said high-lift cam; and hydraulic means for actuating said center lifter to switch the valve lift of said valve lifter between a high and a low lift, said valve lifter characterized in that
 said cylindrical valve lifter is provided with:   a center cam slit for allowing said center cam to freely rotate therein, said center cam slit formed in the top end of the lifter body and extending in the direction of the sliding motion of said center cam;   sliding surfaces formed on the top end of said side lifter for said low-lift cams;   a circular through-hole formed in said lifter body, extending in the direction perpendicular to said center cam slit; and   a cylindrical piston type center lifter slidably fitted in said through-hole under hydraulic pressure.   
   
   
       2 . The direct-acting type valve lifter according to  claim 1 , characterized in that the width of said high-lift cam slit is substantially the same as the width (thickness) of said high-lift cam. 
   
   
       3 . (canceled)