| Generally traditional crankshaft speed sensor of motorcycle is electromagnetic sensor. The structure of the sensor is simple, and the cost is low. However, there are the following drawbacks of it: firstly, the amplitude of its output signal changes with the speed. If the speed is too slow, its output signal is less than 1V, then ECU will be unable to examine it; secondly, its anti-electromagnetic interference ability is poor. If the speed sensor is produced by hall devices, there will not be those drawbacks.The working conditions of the motorcycle engine are relatively poor, great vibration and serious oil pollution. And the hall sensor has lots of advantages, such as non-contact, long-life, high reliability, no spark, no self-oscillation, good temperature performance, strong anti-pollution, simple structure, small size, impact-resistant.These characteristics have decided that it is a very good choice to use the hall-effect sensor in the motorcycle.In this paper, the magnetic circuit design of hall-speed sensor was studied, then determined the suitable program for the specific motorcycle application environment, selected the appropriate hall chips, identified cost-effective materials through the analysis and comparison of magnetic materials; carried on the simulation with finite element analysis software FEMM to the magnetic circuit, proved the feasibility of the plan by theory , and the simulation had analyzed the parameters such as magnet length which have influence on the output signal, obtained the relations between magnet length and the position of the chip; a special testing device was structured, and the experiment verified the numerical simulation results, tested for different shapes and sizes of gear on the impact of the output signal to determine the limit of the target gear size, also got the relationship between the air gap and the position of chip, analyzed the reliability of the chip in different air space. For the better development of the sensor used in motorcycle, all of the above parameters were optimized.According to the installation of the sensor, designed its mechanical structure, applied it to measure the crankshaft speed and the wheel speed, and got the expected signal. The sensors meet the application requirements of the motorcycle and have good characteristics like the reliable output signal, simple, durable. The Crankshaft speed sensor also solves the problem that general hall-effect sensor can not be applied to the high-speed stage of the motorcycle engine. |
