Background of the Invention
Field of the Invention
The present invention relates to an angular position detector for detecting the position of rotary shaft objects, pedals such as Accelerator , Brake , Clutch & others, throttles used in automotive vehicles and more specifically to a non contact angular position sensor which converts rotational angle into electrical signal.
Description of the Related Art
Conventionally, in automobiles contact type potentiometers are used as rotary position sensors to measure rotation angle of Throttle, Accelerator pedals, Brake pedals and electronic speed governors. The potentiometer consists of wiper which slides on resistive PCB thereby changing electrical resistance values.
The drawbacks of potentiometers such as wear and tear are more significant when used in throttle position sensor application due to increased safety and reliability requirements. As throttle is mostly used in a small range (up to 30°), the abrasion is biggest in this limited range.
Before failure, non-linear behavior can be observed due to wear of the resistive tracks and material buildup on wipers, and unfortunately the worst effect is exactly in the driving range in which sensor is used most. The harsh environmental conditions for throttle position sensors include high temperatures, vibrations, shocks and exposure to

various liquids & gases which can all lead to early failure of potentiometers.
Finally, being a passive device, neither wire breakages and over voltage nor internal defects can be detected & communicated to the ECU by the potentiometers. To resolve above disadvantages of contact type rotational angle sensor, there is a need to develop a non contact rotary position sensor. Non contact sensors have following advantages such as no wear, more reliable, good signal to noise ratio, redundancy possible, wire breakage and short circuit detection possible.
There are many patents on Magnetic non contact position sensors, and most of the patents use magnetic circuit with Ring, sector or concave shape magnets.
US Patent Specification no. 5789917 discloses a magnetic position sensor with hall probe formed in an air gap of a stator. This invention relates to a magnetic position sensor which includes a thin tubular-shaped permanent magnet that is integral with a coupling shaft. The permanent magnet is mobile in rotation in a main air gap between two parts made of soft magnetic material. One of the part is formed by stator having a secondary air gap in which a hall probe is placed. The tubular magnet is radically magnetized with one sector facing North Pole on inner side and other sector facing South pole on inner side.
The manufacturing of Ring and Sector magnets is critical. Completed fixtures are required for magnetization of such magnets. Also the cost of magnet becomes higher.

WE CLAIM:
1. A non-contact angular position sensor for detecting the position of rotary
shaft objects for conversion of rotational angle to electrical signal, said sensor
comprising:
a plurality of semi-cylindrical stators;
at least one cylindrical yoke;
plurality of semi-circular pole shoes;
atleast two of disc shaped magnets are used for forming a magnetic circuit;
a flux measurement device for converting magnetic flux lines into voltage signal;
wherein said plurality of disc shaped magnets in said magnetic circuit being mounted between cylindrical yoke and pole shoe such that the N-pole and S-pole of the magnets face each other.
2. The sensor as claimed in claim 1, wherein said plurality of semi-cylindrical stators are placed inside the pole shoe to form a cylindrical air gap between the stators and pole shoe.
3. The sensor as claimed in claim 1, wherein the yoke, pole shoe and stator are co-axial with each other.
4. The sensor as claimed in claim 1, wherein a flux measurement device is placed between the flat surfaces of said semi-cylindrical stators for sensing the magnetic
flux.
5. The sensor as claimed in claim 1, wherein said magnetic circuit contributes to uniform flux distribution of magnetic field in primary air gap.
6. A rotary shaft / object, pedals, throttle used in an automobile comprising a non-contact angular position sensor as claimed in any of the preceding claims.
7. A non-contact angular position sensor for detecting the position of rotary shaft objects for conversion of rotational angle to electrical signal, substantially as herein described, particularly with reference to the accompanying drawings.