What is the function of the car camshaft sensor?
The camshaft position sensor is a sensing device, also known as a synchronization signal sensor. It is a cylinder discrimination positioning device that inputs the camshaft position signal to the ECU and serves as the main control signal for ignition control.
Structural Characteristics
The photoelectric crankshaft and camshaft position sensors produced by Nissan are improved versions of distributors. They mainly consist of a signal disc (i.e., the signal rotor), a signal generator, a distributor, a sensor housing, and a wiring harness connector.
The signal disc is the signal rotor of the sensor and is pressed onto the sensor shaft. At the edge near the signal disc, there are two concentric rings of light-transmitting holes with uniform intervals. Among them, the outer ring has 360 light-transmitting holes (缝隙)， with an interval arc of 1. (The light-transmitting holes account for 0.5， and the shading holes account for 0.5.) They are used to generate crankshaft rotation angle and speed signals； the inner ring has 6 light-transmitting holes (rectangular holes)， with an interval arc of 60， used to generate the top dead center signals of each cylinder. Among them， one rectangular hole has a slightly longer wide side， used to generate the top dead center signal of cylinder 1.
The signal generator is fixed on the sensor housing. It consists of an Ne signal (speed and rotation angle signal) generator， a G signal (top dead center signal) generator， and a signal processing circuit. Both the Ne signal and G signal generators are composed of an LED and a phototransistor (or photodiode)， with two LEDs facing two phototransistors respectively. Working principle
The signal disc is installed between the light-emitting diode (LED) and the photo-sensitive transistor (or photodiode). When the light-transmitting hole on the signal disc rotates to the position between the LED and the photo-sensitive transistor, the light emitted by the LED will be shone onto the photo-sensitive transistor. At this time, the photo-sensitive transistor conducts and its collector outputs a low level (0.1 - 0.3V). When the shading part on the signal disc rotates to the position between the LED and the photo-sensitive transistor, the light emitted by the LED cannot be shone onto the photo-sensitive transistor. At this time, the photo-sensitive transistor is cut off and its collector outputs a high level (4.8 - 5.2V).
If the signal disc rotates continuously, the light-transmitting hole and the shading part will alternately pass by the LED to be transparent or shaded. The collector of the photo-sensitive transistor will alternately output high and low levels. When the sensor shaft rotates with the crankshaft and the valve timing camshaft, the light-transmitting hole and the shading part on the signal disc will pass by the LED. The light emitted by the LED will be alternately shone onto the photo-sensitive transistor of the signal generator due to the light-transmitting and shading effect of the signal disc. Thus, a pulse signal corresponding to the position of the crankshaft and the valve timing camshaft will be generated in the signal sensor.
Since the crankshaft rotates two turns, the sensor shaft drives the signal disc to rotate one full circle. Therefore, the G signal sensor will generate 6 pulse signals. The Ne signal sensor will generate 360 pulse signals. Because the interval arc of the light-transmitting hole of the G signal is 60 degrees, a pulse signal is generated every 120 degrees of the crankshaft rotation. Therefore, the G signal is usually called the 120 signal. The design installation ensures that the 120 signal is generated 70 degrees before top dead center (BTDC70). The signal generated by the light-transmitting hole with a slightly longer rectangular width corresponds to 70 degrees before the top dead center of cylinder 1 of the engine, so that the ECU can control the fuel injection advance angle and the ignition advance angle. Because the interval arc of the light-transmitting hole of the Ne signal is 1 degree (the light-transmitting hole occupies 0.5 degrees and the shading hole occupies 0.5 degrees), in each pulse cycle, the high and low levels each occupy 1 crankshaft angle. 360 signals represent a rotation of 720 degrees of the crankshaft. Every 120 degrees of crankshaft rotation, the G signal sensor generates one signal and the Ne signal sensor generates 60 signals.
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