Lash adjuster

Abstract

A lash adjuster includes a plunger and a cylinder. The cylinder includes a high-pressure chamber defined therein. The plunger has a valve port provided through a bottom wall thereof. The valve port includes a seat. A spherical valve body is accommodated in the high-pressure chamber. The valve body is made of ceramic material containing silicon nitride. The valve body is arranged to have a surface roughness average (Ra) of equal to or less than 0.13 μm. The valve body is arranged to have a contact pressure of equal to or lower than 1386 Mpa with the seat in a state where the valve port is closed by the valve body.

1 . A lash adjuster, comprising:
 a cylinder disposed in a cylinder head;   a plunger fitted in the cylinder, the plunger including a bottom wall;   a low-pressure chamber defined in the plunger;   a high-pressure chamber defined in the cylinder;   a spherical valve body accommodated in the high-pressure chamber;   a valve port provided through the bottom wall of the plunger; and   a spring, the spring being capable of urging the valve body toward the valve port,   wherein the low-pressure chamber and the high-pressure chamber are capable of holding operating fluid,   wherein the low-pressure chamber and the high-pressure chamber are separated by the bottom wall of the plunger,   wherein the valve body and the spring constitute a check valve, the check valve being capable of opening and closing the valve port,   wherein the valve body is made of ceramic material containing silicon nitride,   wherein the valve body has a surface roughness average (Ra) of equal to or less than 0.13 μm,   wherein the valve port includes a seat thereon, and   wherein the valve body has a contact pressure of equal to or lower than 1386 MPa with the seat.   
   
   
       2 . The lash adjuster according to  claim 1 ,
 wherein the spring has an urging direction to urge the valve body,   wherein a periphery of the valve body has a contact point with the seat,   wherein a first line is a line parallel to the urging direction of the spring,   wherein a second line is a line passing through a center of the valve body and the contact point of the valve body with the seat, and   wherein the first line and the second line forms an angle, wherein the angle ranges from 30° to 75°.