Arm type valve lifter

Abstract

A lash adjuster is provided which can be easily assembled and mounted in an arm type valve mounted and in an engine. The valve lifter includes an arm ( 3 ) pivotable about a rocker shaft ( 2 ), and a lash adjuster ( 20 ) mounted in a fitting hole ( 12 ) formed in the arm ( 3 ) at one end thereof for eliminating a valve clearance. The lash adjuster ( 20 ) includes a cylindrical body ( 21 ), an adjusting screw ( 23 ) held in threaded engagement with an internal thread formed on the inner periphery of the body ( 21 ), and a torsion coil spring ( 31 ) for applying a rotational moment to the adjusting screw ( 23 ) that tends to move the adjusting screw ( 23 ) downwardly. With the adjusting screw ( 23 ) in threaded engagement with the internal thread ( 22 ) of the body ( 21 ), the adjusting screw ( 23 ) is screwed into the body ( 21 ) until the adjusting screw ( 23 ) is retracted into the body ( 21 ). In this state, the body ( 21 ) is inserted into the fitting hole ( 12 ) until the upper end portion of the body ( 21 ) protrudes upwardly from the top surface of the arm ( 3 ). The body ( 21 ) is fixed to the arm ( 3 ). After fixing the body ( 21 ) in position, the bottom end portion of the coil spring ( 31 ) is fitted on the upper portion of the body ( 21 ) and brought into engagement with the body ( 21 ). In this sate, after mounting the arm ( 3 ) to the engine, the upper end portion of the torsion coil spring ( 31 ) is turned to twist the torsion coil spring ( 31 ). An engaging piece ( 34 ) provided at the upper end of the thus twisted torsion coil spring ( 31 ) is brought into engagement with an engaging groove ( 35 ) of the adjusting screw ( 23 ), thereby applying the rotational moment from the torsion coil spring ( 31 ) to the adjusting screw ( 23 ).

1 . An arm type valve lifter comprising an arm pivotally mounted on a rocker shaft, a cam configured to rotate and push up first end portion of the arm, thereby pivoting the arm about the rocker shaft, a valve stem carrying a valve and configured to be pushed down by a second end portion of the arm when the first end portion of the arm is pushed up by the cam, so as to open the valve, and a lash adjuster mounted in a fitting hole vertically extending through the arm at one of said first and second end portions of the arm for automatically adjusting a valve clearance,
 characterized in that the lash adjuster comprises a cylindrical body mounted in the fitting hole and fixed to the arm with an upper portion of the body protruding upwardly from a top surface of the arm, said cylindrical body having an internal thread formed on a radially inner surface of the body, an adjusting screw having an external thread formed on a radially outer surface of the adjusting screw and in threaded engagement with said internal thread, a torsion coil spring for applying a rotational moment to the adjusting screw that tends to move the adjusting screw downwardly, said torsion coil spring having a lower end portion fitted on an upper end portion of the body and in engagement with the body, and an upper end portion located over the body, said torsion coil spring having at the upper end portion thereof a first engaging portion which can be brought into engagement with a second engaging portion formed at the upper portion of the adjusting screw.   
     
     
         2 . The arm type valve lifter of  claim 1 , wherein the body has at a lower end portion thereof a flange which is in abutment with a bottom surface of the arm at the end portion of the arm, said flange having a flat surface formed on an outer periphery of the flange and in abutment with a vertical shoulder surface formed on the bottom surface of the arm at its end portion, thereby rotationally fixing the body to the arm, the lash adjuster further comprising a snap ring mounted to a radially outer surface of said upper portion of the body, and a wave spring disposed between the snap ring and the top surface of the arm at the end portion thereof, whereby the body is fixed to the arm by the flange, the vertical shoulder surface, the snap ring and the wave spring. 
     
     
         3 . The arm type valve lifter of  claim 1 , wherein the body is adhesively fixed to the arm. 
     
     
         4 . The arm type valve lifter of  claim 1 , wherein the body is fixed to the arm by welding. 
     
     
         5 . The arm type valve lifter of  claim 1 , wherein each of the internal thread of the body and the external thread of the adjusting screw is one of a serration-shaped thread having a pressure flank for receiving a force that tends to push up the adjusting screw and a clearance flank having a smaller flank angle than the pressure flank, a triangular thread, and a trapezoidal thread. 
     
     
         6 . The arm type valve lifter of  claim 1 , wherein each of the internal thread and the external thread comprises multiple threads. 
     
     
         7 . The arm type valve lifter of  claim 1 , wherein the second engaging portion comprises a diametrically extending groove formed in a top surface of the adjusting screw, and wherein the first engaging portion comprises an engaging piece formed by radially inwardly bending a top end portion of the torsion coil spring. 
     
     
         8 . The arm type valve lifter of  claim 7 , wherein the second engaging portion comprises a plurality of diametrically extending radial grooves. 
     
     
         9 . The arm type valve lifter of  claim 1 , wherein the second engaging portion comprises a shaft portion having opposed flat surfaces on an outer periphery of the shaft portion, and wherein the first engaging portion comprises a helical winding portion having an oblong shape as viewed from top and having opposed inner surfaces that can engage the respective opposed flat surfaces of the shaft portion. 
     
     
         10 . The arm type valve lifter of  claim 1 , wherein an upwardly extending grip portion is integrally formed at a distal end of the first engaging portion. 
     
     
         11 . The arm type valve lifter of  claim 2 , wherein each of the internal thread of the body and the external thread of the adjusting screw is one of a serration-shaped thread having a pressure flank for receiving a force that tends to push up the adjusting screw and a clearance flank having a smaller flank angle than the pressure flank, a triangular thread, and a trapezoidal thread. 
     
     
         12 . The arm type valve lifter of  claim 2 , wherein each of the internal thread and the external thread comprises multiple threads. 
     
     
         13 . The arm type valve lifter of  claim 2 , wherein the second engaging portion comprises a diametrically extending groove formed in a top surface of the adjusting screw, and wherein the first engaging portion comprises an engaging piece formed by radially inwardly bending a top end portion of the torsion coil spring. 
     
     
         14 . The arm type valve lifter of  claim 2 , wherein the second engaging portion comprises a shaft portion having opposed flat surfaces on an outer periphery of the shaft portion, and wherein the first engaging portion comprises a helical winding portion having an oblong shape as viewed from top and having opposed inner surfaces that can engage the respective opposed flat surfaces of the shaft portion. 
     
     
         15 . The arm type valve lifter of  claim 2 , wherein an upwardly extending grip portion is integrally formed at a distal end of the first engaging portion.