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Camshaft Strength And Reliable Support Requirements Are High

Jun 19, 2017

The camshaft is an important part of the engine air distribution mechanism. In order to ensure that the engine work can be timely inhalation of fresh air, and timely discharge of the exhaust gas, the camshaft is responsible for driving the valve on and off on time, some camshaft also has the function of driving the distributor rotation. The speed of the car engine is very high, in order to ensure the efficiency of intake and exhaust, the valve with overhead design, the camshaft through the hydraulic tappet and other institutions to drive the valve action.

Camshaft structure

Although the speed of the camshaft is half the speed of the crankshaft in a four-stroke engine, its speed is still high and requires a lot of torque, so the requirements for the strength and reliability of the camshaft are high. The main body of the camshaft is a cylinder with the same length as the cylinder block. There are a number of cams. The material of the camshaft is usually special cast iron, sometimes made of forged and alloy. Most of the interior of the camshaft is made into a hollow structure, which not only reduces the quality of the camshaft, but also improves the ability of the cam bearing to be loaded. The camshaft is also machined with a lubricating oil passage, which is lubricated by the camshaft, rocker shaft, and rocker arm.

Camshaft position sensor is also called synchronous signal sensor, it is a cylinder identification positioning device, input to the ECU camshaft position signal, is the ignition control of the master signal.

The camshaft position sensor acquires the position signal of the camshaft camshaft and inputs the ECU so that the ECU recognizes the cylinder 1 to compress the top dead center so as to perform sequential injection control, ignition timing control and deflagration control. In addition, the camshaft position signal is also used to identify the first ignition timing when the engine is started. Because the camshaft position sensor can identify which cylinder piston is about to reach the top dead center, it is also known as the cylinder identification sensor.

The engine computer controls the four cylinders according to the camshaft position signal and the crankshaft position signal in the order of 1-3-4-2.

When the engine computer can not receive the camshaft position signal, according to the 1,4 cylinder at the same time injection, 2,3 cylinder jet injection control the way. Because the ignition coil to produce double spark, so the engine can still start and run, then deflagration control off, ignition advance angle delayed, the output power down.

Camshaft sensor

The camshaft sensor is fixed to the cylinder head cover.

The camshaft sensor detects the position of the intake camshaft by means of an incremental wheel (camshaft sensor gear) fixed to the camshaft. When the crankshaft sensor fails, the engine control calculates the engine speed accordingly. The camshaft sensor, together with the crankshaft sensor, is necessary for the ejection device (the injection of each cylinder is at the optimum ignition time).

Functional description

Through the camshaft sensor, the engine control system can identify whether the first cylinder is in the compression phase or during the ventilation phase.

The camshaft sensor is designed as a non-contact Hall sensor. The camshaft sensor has six different tooth surfaces. The tooth surface distance is recorded by the Hall sensor.

The engine control system will then calculate:

● camshaft speed

● camshaft speed

● The exact location of the camshaft

 To start the vehicle, the engine control unit checks whether the following conditions are met:

● The signal from the crankshaft sensor is not wrong

● These two signals must be identified in the specified chronological order

This step is called a synchronization process and is performed only when the vehicle is started. The engine controller can only properly control the fuel injection after synchronization. Do not start the vehicle when it is not synchronized. When the voltage is applied, it is possible to recognize whether the sensor is in the position of one tooth or at the position of a notch.