Arm type valve gear

Abstract

A lash adjuster which is mounted in an arm type valve gear can be easily mounted. A fitting hole (12) is provided in one end of an arm (3) which can rock about a rocker shaft (2). A lash adjuster (20) for absorbing a valve clearance and mounted within the fitting hole (12) is configured of a cylindrical body (21), an adjustment screw (23) which is engaged with a female screw thread (22) formed on the inner periphery of the body (21), and a coiled torsion spring (31) which applies to the adjustment screw (23) rotational moment in the direction in which the adjustment screw (23) descends. The adjustment screw (23) is engaged with the female screw thread (22) of the body (21), the body (21) is inserted into the fitting hole (12) while the lash adjuster (20), into which the adjustment screw (23) is screwed, is retracted, and the body (21) is affixed to the arm (3) with the upper end of the body (21) exposed upward at the upper surface of an end of the arm (3). After the body (21) is affixed, the lower end of the coiled torsion spring (31) is engaged with the upper part of the body (21), and the lower end of the coiled torsion spring (31) is engaged with the body (21). Then, the coiled torsion spring (31) is twisted by rotating the upper end of the coiled torsion spring (31) after the arm is mounted to the engine, an engagement section (34) provided to the upper end of the coiled torsion spring is engaged with an engagement groove (35) of the adjustment screw (23), and rotational moment is applied to the adjustment screw (23) by the restoring elasticity of the coiled torsion spring (31).

Description

technical field [0001] The invention relates to arm valve drives in internal combustion engines. Background technique [0002] As a valve train configured to open and close intake valves or exhaust valves (hereinafter simply referred to as valves) by rotation of a cam, the following arm valve train is known: The arm is pivotably supported around the arm axis, one end of the arm is pushed up by the rotation of the cam, and the other end of the arm pushes down the valve stem to open the valve. [0003] In the above-mentioned arm type valve train, as described in Patent Document 1 and Patent Document 2, a mechanical lash adjuster is incorporated into the end portion of the arm, and the valve lash is automatically adjusted by the lash adjuster. [0004] Here, in the lash adjusters described in the above-mentioned Patent Document 1 and Patent Document 2, the internal thread is formed on the inner periphery of the cylindrical main body, and the external thread formed on the outer...

AI Technical Summary

Problems solved by technology

[0007] However, in the above-mentioned lash adjuster, the main body and the adjusting screw are stretched before being assembled to the engine. When the lash adjuster is assembled to the engine in this stretched state, compression leakage occurs when the engine is started. Complete combustion is not possible, and there is a possibility of damage due to mutual interference of the intake and exhaust valves. Therefore, the adjustment screw must be pressed in against the elasticity of the elastic member, and assembled while maintaining the pressed state, so the assembly is very cumbersome. question

[0008] In order to solve this problem, it is extremely effective to form a pin hole that penetrates radially through the main body and the adjustment screw, and insert the mounting pin into the pin hole to hold the adjustment screw in the initial installation that is press-fitted into the main body. state, but there are cases where the mounting pin is forgotten to be pulled out after the slack adjuster is assembled, or the pulled out mounting pin is dropped into the engine. In addition, since the processing of the pin hole is required, it is not conducive to cost saving

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