Patent GB-1389653-A (GB)
Title: Engine performance analyzer
IPC: G01R31/00
Filed: 1973-01-24
Abstract: 1389653 Electric testing; electric meters; indicating apparatus CLAYTON MFG CO 24 Jan 1973 [28 Jan 1972] 3624/73 Headings G1U G1Q and G1J An analyser for a multi-cylinder combustion engine comprises, a plurality of probes connected to the engine; an oscilloscope for displaying probe output signals; a generator for providing selected sweep signals for the oscilloscope and a multiposition programme switch for applying selected probe outputs to a test meter and the oscilloscope, selected sweep voltages to the oscilloscope and for causing a movable scale member to position a selected scale adjacent the test meter, for each switch position. Test procedure and apparatus - Fig. 1 The operator connects the probes to various points in the engine and also connects leads to a dynamometer and exhaust gas analyser which are connected to the vehicle. The battery polarity of the vehicle is selected by switch 28 and power supplied by switch 26 which also selects the number of cylinders. The programme switch 24 is then sequenced through positions A-M and the appropriate tests made. The switch 24 serves to select the correct scales for meters 16, 17, 18 connects the appropriate probes to the meter and oscilloscope inputs and provides the required trigger waveforms for the desired oscilloscope raster. The tests made include, starter current, battery voltage, points volts drop, ignition pulses, alternator performance, dwell-time, ignition advance, cylinder power balance engine speed, exhaust gas analysis, road speed and torque, resistance of spark plug leads and the solenoid 'on-time' of a fuel injection system if required. The apparatus also provides pulses for firing a strobe light 34, the timing being varied by knob 36 of a potentiometer. The engine probes are connected to the primary and secondary ignition coils, battery voltage and current monitors, engine manifold, the No. 1 cylinder spark plug and earth. The dynamometer provides indications of engine torque and road speed and the gas analyser provides measurement of nitric oxide, carbon monoxide and hydrocarbon content of the exhaust gas. Apparatus details - Fig. 6B Cylinder power balance test A switch (32) Fig. 1 selects the cylinder to be shorted. Generator 150 includes a ring counter which counts the ignition pulses via level trigger 140. The counter is reset by the No. 1 cylinder pulse detected by the probe output 152. The number of cylinders (and thus stages in the counter) is set by the power switch 26. The generator output 151 is a pulse which brackets the firing time of the selected cylinder and actuates shorting switch 154 via programme switch 24 to suppress the firing of that cylinder. The engine speed is measured by generator 170 which measures the p.r.f. of the No. 1 cylinder ignition pulses. Expand RPM generator 172 stores the speed before shorting and compares it with the speed after shorting, providing an output via  switch 24 to the appropriate meter representing the difference. Dwell-time Ignition pulses from trigger switch (131), Fig. 6A (not shown) pass via a low pass filter and clipper to integrator 157 which produces a D.C. voltage representing the width of the pulses (time points are closed). The output is amplified by amplifier 158, whose gain is set by switch (26) dependent on the number of cylinders. Ignition advance Sweep generator 136 provides a saw-tooth waveform triggered by the ignition pulses 133. Trigger 160 has a variable level set by potentiometer 163 which is adjusted by knob (36), Fig. 1 on the strobe unit (34). When the engine timing marks, illuminated by the strobe light 166 are coincident, the position of the potentiometer indicates the ignition advance angle. Alternatively, with potentiometer 163 set at one end, the strobe light 16<SP>b</SP> is driven by the No. 1 cylinder pulses 152 and the advance read from a scale on the engine block. Oscilloscope triggering The oscilloscope trigger pulses are derived from either the primary or secondary ignition coils, selected by switch (30) Fig. 1. Pulses from shaper (132) Fig. 6B (not shown) trigger sawtooth generator 136. Trigger 140 provides pulses just prior to the firing of the next cylinder, via switch 24 to generator 142 which provides a sawtooth horizontal sweep for the oscilloscope. This produces one sweep per cylinder i.e. a superimposed picture or vertically stacked if vertical deflection is provided. Trigger 140 output also drives trigger 144 which includes a gate opened by a pulse from generator 150 bracketing the firing of No. 1 cylinder. In this case, determined by the position of switch 24. Generator 142 provides a single sweep covering a complete engine cycle. In a third case, the output of sawtooth generator 136 is fed to trigger 138 which provides output pulses at the instant the points are open, thus providing from generator 142, a delayed sweep. Vertical deflection of the oscilloscope is provided either directly by the ignition pulses over line 146 or with the addition of a staircase voltage triggered by each ignition to provide multi-beam displays. Meter construction Figs. 3, 4 A tape (20) Fig. 2 (not shown) has coloured and transparent portions providing an indication 23 Fig. 3. The tape is supplied from spool (48) driven by a motor (47) and passes rollers (49), 51 before reaching take-up reel 52 which is spring- biased. The motor (47) is driven by the output of a differential amplifier (42) whose inputs come from a potentiometer on the spool (48) shaft and from the test signal input circuit. Thus the indicator is driven to a point along the scale on barrel 50 until the amplifier inputs are equal. The barrel 50 is hollow and carries six scales around its circumference. The barrel is rotatable and carries an end-plate 62, Fig. 4 having six holes 64 and a bifurcated contact 66 which wipes contacts 67, 68 on fixed plate 70. When selector switch 24 is changed, the contacts connected by contact 66 are de-energized as is output wire 82 to solenoid 76 Fig. 3. Pin 74 thus withdraws from holes 72 in plate 70 and 64 in plate 62. Motor 90 becomes energized via contact 80 and rotates barrel 50 until the wire 82 becomes energized again, thus operating the solonoid, inserting pin 74 through plates 70, 62 and stopping the motor 90.