Patent GB-1514734-A (GB)
Title: Angular position transducers for use in engine timing controls
IPC: G01D5/242
Filed: 1974-05-21
Abstract: 1514734 Measuring angular displacement LUCAS ELECTRICAL Ltd 16 May 1975 [21 May 1974 4 June 1974 20 Aug 1974 8 Oct 1974(2)] 22535/74 25274/74 36548/74 43481/74 and 43482/74 Heading G1N An apparatus for indicating successive positions of a rotating member, e.g. for use in an engine timing control system or an engine fuel injection system, comprises an electromagnetic generator 9 connected to be driven by the rotating member and producing, in use, a beam of primary and secondary pulses, there being at least one secondary pulse between each pair of successive primary pulses and the secondary pulses being of magnitude different from that of the primary pulses. Recognition means 23 are connected to the generator 9 for distinguishing the two types of pulses and include integrating means for generating a signal corresponding to the time integral of at least part of the voltage waveform of each pulse. A control is connected to the recognition means for providing output signals indicating successive positions of the rotating member. The control comprises a two-way switch 24 connected to a fixed frequency clockpulse generator 25 and having outputs each connected to a respective frequency divider 26, 27. The divider 26 has its output connected to a counter 28 which in turn feeds a memory matrix device 30. The device 30 also receives a digital input from an encoder 31 which is connected to a manifold vacuum transducer. The other divider 27 is programmable and feeds a counter 29 which in turn feeds a digital comparator 33. Inputs to the comparator 33 are also taken from the memory matrix device 30. The comparator 33 is connected to a spark generator 34. The recognition means includes pulse height sensitive means connected to the output of the integrating means and arranged to recognise the primary pulses. In turn the pulse height sensitive means includes an active peak detector circuit having a capacitor which is charged periodically to a voltage representing the peak pulse height of the output of the integrating means and the comparator produces an output signal when the output of the integrating means exceeds a fixed proportion of the voltage on the generator. A zero-crossing detector is connected to the output of the generator and produces an output whenever the output of the generator is of one polarity and a signal combining circuit having inputs connected to the output of the zero-crossing detector and producing an output in each interval between the recognition means producing an output and the zero-crossing detector producing an output. Various embodiments of the circuits are disclosed. The generator, Figs. 1, 2, comprises a stator plate 11 and a motor plate 13 each having identical unequally spaced poles 15, 14 respectively. Windings 22 are mounted beneath the rotor 13. The stator plate 11 is mounted on an annular ferromagnetic base-plate 16 by screws which pass through the plate 11 as well as an annular ferromagnetic packing member 17, an annular magnet 18 and an annular ferromagnetic winding support member 18.