Lash adjuster

Abstract

The object is to prevent rotation of the case when a load is applied to the adjusting screw that tends to push in the adjusting screw. The lash adjuster includes a cylindrical case 13 having a bottom 17 and received in a mounting hole 6 formed in a top surface of a cylinder head 2, the case 13 having an internal thread 14 on an inner periphery thereof, an adjusting screw 16 having an external thread 15 on an outer periphery thereof which is in threaded engagement with the internal thread 14 of the case 13, and a return spring 18 disposed between the adjusting screw 16 and the bottom 17 of the case 13 and biasing the adjusting screw 16 in a direction to protrude upwardly from the case 13, the adjusting screw 16 having a protruding end 22 protruding from the case 13 and configured to pivotally support an arm 7 of a valve gear, wherein an anti-rotation protrusion 27 is provided on the bottom 17 of the case 13 which is fitted in a fitting port 26 formed in an inner bottom surface 24 of the mounting hole 6, thereby preventing rotation of the case 13.

1 . A lash adjuster comprising a cylindrical case ( 13 ) having a bottom ( 17 ) and received in a mounting hole ( 6 ) formed in a top surface of a cylinder head ( 2 ), said case ( 13 ) having an internal thread ( 14 ) on an inner periphery thereof, an adjusting screw ( 16 ) having an external thread ( 15 ) on an outer periphery thereof which is in threaded engagement with the internal thread ( 14 ) of the case ( 13 ), and a return spring ( 18 ) disposed between the adjusting screw ( 16 ) and the bottom ( 17 ) of the case ( 13 ) and biasing the adjusting screw ( 16 ) in a direction to protrude upwardly from the case ( 13 ), said adjusting screw ( 16 ) having a protruding end ( 22 ) protruding from the case ( 13 ) and configured to pivotally support an arm ( 7 ) of a valve gear, characterized in that the lash adjuster further comprises an anti-rotation part arranged to prevent rotation of the case ( 13 ). 
     
     
         2 . The lash adjuster of  claim 1  wherein said anti-rotation part comprises an anti-rotation protrusion ( 27 ) provided on the bottom ( 17 ) of the case ( 13 ), and a fitting port ( 26 ) formed in an inner bottom surface ( 24 ) of the mounting hole ( 6 ), said anti-rotation protrusion ( 27 ) being fitted in the fitting port ( 26 ). 
     
     
         3 . The lash adjuster of  claim 2  wherein said anti-rotation protrusion is a protrusion ( 27 ) having a D-cut portion ( 28 ) on an outer periphery thereof. 
     
     
         4 . The lash adjuster of  claim 2  wherein said anti-rotation protrusion is a protrusion ( 32 ) having two chamfers ( 31 ) on an outer periphery thereof. 
     
     
         5 . The lash adjuster of  claim 2  wherein said anti-rotation protrusion is a protrusion ( 35 ) in the shape of a regular polygonal column. 
     
     
         6 . The lash adjuster of  claim 2  wherein said anti-rotation protrusion is a protrusion ( 37 ) offset from an axis of the case ( 13 ). 
     
     
         7 . The lash adjuster of  claim 2  wherein said fitting port ( 26 ) is one end of an air vent hole ( 25 ) extending from the inner bottom surface ( 24 ) of the mounting hole ( 6 ) to outside. 
     
     
         8 . The lash adjuster of  claim 7  wherein a through hole ( 30 ) extends vertically through the bottom ( 17 ) of the case( 13 ), with a bottom end thereof open to a free end of the anti-rotation protrusion ( 27 ). 
     
     
         9 . The lash adjuster of  claim 1  wherein said anti-rotation part is a friction ensuring part configured to ensure frictional resistance between the bottom ( 17 ) of the case ( 13 ) and the inner surface of the mounting hole ( 6 ), thereby preventing rotation of the case ( 13 ). 
     
     
         10 . The lash adjuster of  claim 9  wherein said friction ensuring part comprises an oil film expelling groove ( 53 ) formed in an outer bottom surface ( 52 ) of the case ( 13 ). 
     
     
         11 . The lash adjuster of  claim 9  wherein said friction ensuring part comprises a satin-finished surface formed on an outer bottom surface ( 52 ) of the case ( 13 ). 
     
     
         12 . The lash adjuster of  claim 11  wherein said satin-finished surface is formed by shot peening. 
     
     
         13 . The lash adjuster of  claim 9  wherein said friction ensuring part comprises a tapered outer peripheral surface ( 55 ) formed on the bottom ( 17 ) of the case ( 13 ) and having a downwardly decreasing diameter, and a tapered inner peripheral surface ( 54 ) formed on the mounting hole ( 6 ) and having a downwardly decreasing diameter, said tapered outer peripheral surface ( 55 ) being engaged in the tapered inner peripheral surface ( 54 ). 
     
     
         14 . The lash adjuster of  claim 9  wherein said friction ensuring part comprises a recess ( 56 ) formed in an outer bottom surface ( 52 ) of the case ( 13 ) except its peripheral edge, or a recess formed in an inner bottom surface ( 24 ) of the mounting hole ( 6 ) except its peripheral edge. 
     
     
         15 . The lash adjuster of  claim 9  wherein said friction ensuring part comprises a small-diameter inner peripheral portion ( 57 ) formed on the mounting hole ( 6 ), said bottom ( 17 ) of the case ( 13 ) being press-fitted in the small-diameter inner peripheral portion ( 57 ). 
     
     
         16 . The lash adjuster of  claim 9  wherein said friction ensuring part comprises a sheet ( 58 ) made of rubber or an elastomer and disposed between an outer bottom surface ( 52 ) of the case ( 13 ) and an inner bottom surface ( 24 ) of the mounting hole ( 6 ). 
     
     
         17 . The lash adjuster of  claim 9  wherein said friction ensuring part comprises a seat ( 59 ) made of iron and forming an inner bottom surface ( 24 ) of the mounting hole ( 6 ). 
     
     
         18 . The lash adjuster of  claim 9  wherein said friction ensuring part comprises a sleeve ( 61 ) made of iron and forming the mounting hole ( 6 ). 
     
     
         19 . The lash adjuster of  claim 1  wherein said return spring ( 18 ) is a compression coil spring that applies an axial force to the adjusting screw ( 16 ) that tends to push the adjusting screw ( 16 ) out of the case ( 13 ). 
     
     
         20 . The lash adjuster of  claim 1  wherein said return spring ( 18 ) is a torsion spring that applies torque to the adjusting screw ( 16 ) that tends to push the adjusting screw ( 16 ) out of the case ( 13 ). 
     
     
         21 . The lash adjuster of  claim 20  wherein said torsion spring is one of a torsion coil spring, a spiral spring and a volute spring. 
     
     
         22 . The lash adjuster of  claim 1  wherein said external thread ( 15 ) and the internal thread ( 14 ) are triangular threads, trapezoidal threads or serration-shaped threads.