The working principle of the camshaft and the difference between single and double camshafts


How the camshaft works: A camshaft is a component in a […]

How the camshaft works:
A camshaft is a component in a piston engine. Its function is to control the opening and closing of the valve. Although the speed of the camshaft in a four-stroke engine is half the speed of the crankshaft (in a two-stroke engine, the speed of the camshaft is the same as that of the crankshaft), but usually its speed is still very high, and it needs to bear a lot of torque, so the design of The camshaft has high requirements in terms of strength and support, and its material is generally high-quality alloy steel or alloy steel. Since the law of valve movement is related to the power and running characteristics of an engine, the design of the camshaft occupies a very important position in the design process of the engine.
Common failures of camshafts include abnormal wear, abnormal noise, and fracture. Abnormal wear and tear symptoms often appear before abnormal noise and fracture occur.
(1) The camshaft is almost at the end of the engine lubrication system, so the lubrication condition is not optimistic. If the oil supply pressure of the oil pump is insufficient due to the long-term use, or the lubricating oil passage is blocked so that the lubricating oil cannot reach the camshaft, or the tightening torque of the bearing cap fastening bolts is too large, the lubricating oil cannot enter the camshaft clearance, and the Causes abnormal wear of the camshaft.
(2) Abnormal wear of the camshaft will cause the gap between the camshaft and the bearing seat to increase, and axial displacement will occur when the camshaft moves, resulting in abnormal noise. Abnormal wear will also cause the gap between the drive cam and the hydraulic lifter to increase, and the cam will collide with the hydraulic lifter when combined, resulting in abnormal noise.
(3) Serious failures such as breakage of the camshaft sometimes occur. Common causes include cracked hydraulic tappets or severe wear, severe poor lubrication, poor camshaft quality, and cracked camshaft timing gears.
(4) In some cases, the failure of the camshaft is caused by human reasons, especially when the engine is repaired, the camshaft is not properly disassembled and assembled. For example, when removing the camshaft bearing cover, use a hammer to knock it down or pry it with a screwdriver, or install the bearing cover in the wrong position, causing the bearing cover to not match the bearing seat, or the tightening torque of the bearing cover fastening bolts is too large. When installing the bearing cover, pay attention to 4-cylinder single overhead camshaft the direction arrows and position numbers on the surface of the bearing cover, and use the torque wrench to tighten the bearing cover fastening bolts in strict accordance with the specified torque.
Production technology:
The camshaft is one of the key parts of the engine. The hardness of the camshaft peach and the depth of the white layer are the key technical indicators that determine the service life of the camshaft and the efficiency of the engine. On the premise of ensuring that the cam has a high enough hardness and a fairly deep white layer, it should also be considered that the journal does not have high carbides, so that it has better machining performance.
The single camshaft controls the opening and closing of the intake and exhaust valves at the same time. The dual camshafts are one control of the intake valve and one control of the exhaust valve, which can better control the advance and late angles of the opening of the intake and exhaust valves, so that the Go in more fully and exhaust more thoroughly. The dual camshaft is a control intake valve and a control exhaust valve, which can better control the advance and late angle of the intake and exhaust valve opening, so as to make the intake and exhaust more fully exhausted. Overhead twin camshafts are two camshafts mounted on the cylinder head, one for driving the intake valve and the other for driving the exhaust valve. The use of double overhead camshafts does not require high design requirements for camshafts and valve springs. It is especially suitable for hemispherical combustion chambers with V-shaped valves, and is also easy to use with four-valve valve trains.

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