What are the valve rocker arm and tappet
The automobile valve rocker arm and tappet are the important parts of the automobile engine valve mechanism, and each of them has a specific function and effect.
Valve rocker arm
valve rocker arm is a key part of the engine valve mechanism, its main role is to work with the camshaft to ensure the timely opening and closing of the valve, so as to complete the intake and exhaust process. The rocker arm is a two-arm lever with the middle shaft hole as the fulcrum. The short arm is equipped with a valve clearance adjustment screw on one side, and the long arm is provided with an arc working face to push the valve .
Valve tappet
The main function of the valve tappet is to transfer the motion and force of the camshaft to the push rod or valve, and push the push rod or valve to overcome the force of the valve spring. The tappet needs to withstand the lateral force exerted by the CAM during operation and transfer it to the body or cylinder head. Tappets can be divided into mechanical and hydraulic tappets, each with its own specific structure and function:
mechanical tappet : usually made of alloy steel or alloy cast iron with good wear resistance. The structure is simple but the valve clearance needs to be adjusted regularly.
hydraulic tappet : Automatically eliminates valve clearance without adjustment and reduces transmission noise. The hydraulic tappet is composed of a tappet body, a plunger and a compensation spring, etc., which is automatically adjusted by the pressure of the oil and the action of the spring .
Specific application scenarios and advantages and disadvantages
mechanical tappet : simple structure, but need regular maintenance and adjustment of valve clearance. It is applicable to scenarios that do not require high maintenance.
hydraulic tappet : complex structure but can be automatically adjusted, reduce maintenance work, suitable for high reliability and noise requirements of the scene. The hydraulic tappet is automatically adjusted through the action of oil pressure and spring, which can eliminate valve clearance and reduce transmission noise .
The role of the valve rocker arm and tappet mainly includes the following aspects:
The role of the tappet
The main function of the tappet is to transfer the thrust of the camshaft to the push rod or valve rod, and push the push rod or valve to overcome the force of the valve spring and move. At the same time, the tappings also bear the lateral forces exerted by the camshaft rotation. The tappet can be divided into two types: ordinary tappet and hydraulic tappet:
ordinary tappet : including fungus tappet, barrel tappet and roller tappet. Common tappets are rigid structures and cannot automatically eliminate the valve clearance, so it is necessary to adjust the valve clearance regularly.
hydraulic tappet : can eliminate the valve clearance of the engine, no need to adjust the valve clearance, and can reduce the transmission noise of the engine valve mechanism. The hydraulic tappet automatically adjusts the valve clearance through the oil pressure and the action of the compensating spring to ensure the close contact between the valve and the CAM .
The role of the rocker arm
The main function of the rocker arm is to pass the force from the push rod or CAM to the valve after changing the direction to make it open. The rocker arm assembly comprises a rocker arm, a rocker arm shaft, a support seat, a valve clearance adjustment screw and other parts. These parts work together to ensure the accurate opening and closing of the valve, thereby controlling the intake and exhaust process and ensuring the normal operation of the engine .
Specific working principle
When the engine is working, the crankshaft drives the camshaft to rotate through the transmission mechanism, and the CAM on the camshaft pushes the push rod or valve through the tashet. When the raised part of the CAM pushes against the tappet, the tappet transfers the force to the push rod or valve, opening the valve. With the rotation of the CAM, the valve is gradually closed under the action of the spring. The rocker arm transmits the force of the push rod or CAM to the valve, ensuring that the valve opens and closes accurately .
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