Patent GB-715898-A (GB)
Title: Test instrument for high tension spark distributors
IPC: F02P17/02
Filed: 1951-09-04
Abstract: 715,898. Testing engine distributers. ANGLO-IRANIAN OIL CO., Ltd., HULF, H. J., and WITHERS, J. G. Aug. 25, 1952, [Sept. 4, 1951.] No. 20816/51. Class 37. [Also in Groups XXVII and XXXVIII] In a system for testing the distributers of I.C. engines the distributer is driven at an indicated speed and the timing of impulses derived from an ignition lead is compared with that of reference impulses by feeding both sets to the respective inputs of a double stability circuit having a meter in its output circuit. Switches are provided to adapt the system for timing individual elements or the average of all elements in 4 and 6- cylinder distributers. The driving speed is adjustable so that the automatic timing of the interrupter may be checked and a source of variable sub-atmospheric pressure is provided for testing distributers with interrupters responsive to pressure in the induction pipe. Constructional details. The casing of the distributer is clamped in a stationary chuck G, Fig. 5, and the rotor shaft is held by a chuck D on the shaft of an electric motor. The latter also carries a magnetic arm R with a chisel edged pole piece co-operating with a ring of coils N for generating the reference impulses. Circuit arrangements. Reference impulses a Fig. i corresponding to a single cylinder or to all the cylinders in turn according to the position of switches S 13 , S 14 , S 3  ... S8 Fig. 2, after amplification in V 1  and V 10  with automatic gain control, control the discharge of capacitor C 4  via thyratron V2. The resulting pulse after differentiation by C5, R9 has the form f Fig. 1 at the grid of valve V3 of the double stability circuit V 3 , V 4 . Impulses picked up capacitively from an appropriate ignition lead produce highfrequency impulses which are rectified and smoothed in a circuit G1 and after amplification at V 5  produces pulses of the form k, Fig. 1, at the grid of thyratron V6. The resulting discharge of capacitor C16 gives a form n at the grid of the other valve V 4  of the double stability circuit. The reference pulse causes the anode current of V 4  to assume its lower value and the ignition pulse the higher value. The reading of Mi consequently depends on the time separating the two pulses which determines the ratio of high to low current in each pulse period p, Fig. 1, The speed of the distributer is indicated by a meter M 2  controlled by impulses derived from the reference impulses (see Group XXXVIII). Calibration: adapting for different tests. The timing system is calibrated by operating switch S1 which connects the right hand anode of the double stability circuit to potential divider R 22 , R 23 , disables the input from the signal channel and applies impulse to V 2 , V 4  then conducts its peak anode current, and shunt R  17  is adjusted to give a suitable scale reading. With the switches as shown, the circuit is conditioned for testing the arrangements for one plug at a time by the further operation of switches S 3  to S8 one at a time. Average-timing of a four and six cylinder engines is tested with switches S  14  and either S 13  or S 11  operated. These modify the proportion of the output voltage of V 1 applied to V  10  to compensate for the shunting effect of the idle pick-up coils connected in parallel with the operative one and modify the circuit parameters of V 3 , V 4 , and V 7 , V8 to ensure that Mi and M 2  read correctly without further calibration.