GB2171213A

GB2171213A - Test instrument

Info

Publication number: GB2171213A
Application number: GB08600356A
Authority: GB
Inventors: John Roger Bywater
Original assignee: Individual
Current assignee: Individual
Priority date: 1985-02-14
Filing date: 1986-01-08
Publication date: 1986-08-20
Also published as: GB8600356D0; GB8503853D0

Abstract

A test instrument for testing automobile engine fuel injection and electronic ignition systems has a pulse generator 11 for providing component actuating pulses, and probes 14 for applying such pulses to the components, as well as indicator means 16 for indicating the occurrence of pulses. The instrument can be made in hand-held form and simple to use for e.g. roadside breakdown diagnosis. The generator may be a free-running astable oscillator, or a monostable oscillator e.g. connected as shown for triggering by ignition pulses applied via sensor leads 19 and an amplifier 18. <IMAGE>

Description

SPECIFICATION Test instrument This invention relates to test instruments and particularly for testing electric pulse-actuated engine components.

Automobiles are nowadays being fitted in increasing numbers with electronic fuel injection and ignition systems. Although very reliable, when such systems do go wrong, diagnosis of the fault is not such a straightforward matter as with conventional carburation and ignition systems. Indeed, diagnosis is essentially a matter of replacing parts until the fault is cleared, which can be expensive and time consuming, especially if replacement parts need to be specially ordered with no guarantee that they are in fact required.

The present invention provides a test instrument, which is simple enough to be made available in hand-held form particularly for use at a breakdown on the road and which is easy to use without special training so that it can readily pass into day-today use by motor technicians.

The invention comprises a test instrument for electric pulse-actuated engine components comprising a pulse generator adapted to simulate component actuating pulses and probe means connected to said pulse generator and adapted to contact said components to apply simulated actuating pulses thereto, and indicator means indicating the occurrence of pulses.

Said pulse generator may comprise an oscillator which may be a free running astable oscillator producing a continuous pulse train or a monostable oscillator having triggering means to trigger said monostable osciallator to produce single pulses.

The astable oscillator may be used to apply a series of pulses, through the probe, simulating the actuating pulses for the solenoids of a fuel injection system, so that they can be tested to see if they function properly, while the engine is not running. Ordinarily, of course, the solenoids derive their operating pulses from an electronic control unit which operates only when the engine is switched on.

A pulse train can also be applied to simulate an electronic ignition system so that the free running oscillator can substitute for the distributor for test purposes.

For the monostable oscillator, triggering means may comprise an amplifier and input means connected to said amplifier for inputting signals from an inductive pickup or other sensor in the engine to be tested. Such inductive pickup may be of an electronic ignition system.

A most useful instrument has an oscillator switchable between a free running astable state and a monostable state so that the instrument can carry out all of the above functions.

Suitable indicator means may comprise a light emitting diode arranged to flash on for each pulse.

One embodiment of a test instrument according to the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a circuit diagram, and Figure 2 is a diagram of part of an electrical system for an automobile internal combustion engine showing how the test instrument may be used.

The test instrument 10 illustrated in Figures 1 and 2 comprises a pulse generator 11 in the form of an oscillator which can be switched by a switch 12 between a free running astable state and a monostable state. The pulse output of the oscillator 11 is connected to the base 13b of a transistor 13 of which the collector 13c is connected to a probe 14. A pulse switches on the transistor to connect the probe to ground through a current limiting resistor 15. The probe 14 is normally maintained at 12 volts through a light emitting diode 16 and series resistor 17. The diode lights when current flows through it, which is to say whenever the transistor 13 is switched on. The diode and transistor are protected in conventional manner not further described herein against inductive voltage peaks.

Switching the transistor 13 by a pulse train from the free running astable oscillator 11 causes current pulses to flow through the probe whenever it is connected to a termainal of a component to test the same. Such current pulses simulate accuating pulses for components such as the solenoids 21 of fuel injectors (Figure 2) normally actuated by pulses under the control of an electronic control unit 24. A relay 23 is permanently conducting whenever the engine is operative.

The oscillator 11 can be connected to a built-in amplifier 18 having input leads 19 by which it can be connected to an inductive pick-up 20 for an ignition amplifier 25 (Figure 2) of an electronic ignition system, which also includes a coil 26 and a ballast resistor 27. The oscillator 11, which is in this position of the switch 12 in its monostable state, now outputs single pulses timed to the ignition pulses and the probe can be applied to the coil 26 to simulate the ignition amplifier 25 as a test thereof.

With the switch 12 back in position to put the oscillator 11 into its free running astable state a train of pulses can be applied by the probe 14 to the coil 26 independently of the inductive pick-up 20 and ignition amplifier.

The instrument can be made compact so that even with an internal 12 volt supply it is a hand held device.

Whereas the principal uses for which the instrument was devised have been described above, it will be found useful in different ways. For example, it may be used to detect live points and earth points in a circuit - in the astable condition if the probe 14 is connected to earth, the light emitting diode illuminates continuously, whereas if the probe 14 is connected to a point at 12V potential, the diode will not be illuminated.

1. A test instrument for electric pulse-actuated engine components comprising a pulse generator adapted to simulate component actuating pulses

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Test instrument This invention relates to test instruments and particularly for testing electric pulse-actuated engine components. Automobiles are nowadays being fitted in increasing numbers with electronic fuel injection and ignition systems. Although very reliable, when such systems do go wrong, diagnosis of the fault is not such a straightforward matter as with conventional carburation and ignition systems. Indeed, diagnosis is essentially a matter of replacing parts until the fault is cleared, which can be expensive and time consuming, especially if replacement parts need to be specially ordered with no guarantee that they are in fact required. The present invention provides a test instrument, which is simple enough to be made available in hand-held form particularly for use at a breakdown on the road and which is easy to use without special training so that it can readily pass into day-today use by motor technicians. The invention comprises a test instrument for electric pulse-actuated engine components comprising a pulse generator adapted to simulate component actuating pulses and probe means connected to said pulse generator and adapted to contact said components to apply simulated actuating pulses thereto, and indicator means indicating the occurrence of pulses. Said pulse generator may comprise an oscillator which may be a free running astable oscillator producing a continuous pulse train or a monostable oscillator having triggering means to trigger said monostable osciallator to produce single pulses. The astable oscillator may be used to apply a series of pulses, through the probe, simulating the actuating pulses for the solenoids of a fuel injection system, so that they can be tested to see if they function properly, while the engine is not running. Ordinarily, of course, the solenoids derive their operating pulses from an electronic control unit which operates only when the engine is switched on. A pulse train can also be applied to simulate an electronic ignition system so that the free running oscillator can substitute for the distributor for test purposes. For the monostable oscillator, triggering means may comprise an amplifier and input means connected to said amplifier for inputting signals from an inductive pickup or other sensor in the engine to be tested. Such inductive pickup may be of an electronic ignition system. A most useful instrument has an oscillator switchable between a free running astable state and a monostable state so that the instrument can carry out all of the above functions. Suitable indicator means may comprise a light emitting diode arranged to flash on for each pulse. One embodiment of a test instrument according to the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a circuit diagram, and Figure 2 is a diagram of part of an electrical system for an automobile internal combustion engine showing how the test instrument may be used. The test instrument 10 illustrated in Figures 1 and 2 comprises a pulse generator 11 in the form of an oscillator which can be switched by a switch 12 between a free running astable state and a monostable state. The pulse output of the oscillator 11 is connected to the base 13b of a transistor 13 of which the collector 13c is connected to a probe 14. A pulse switches on the transistor to connect the probe to ground through a current limiting resistor 15. The probe 14 is normally maintained at 12 volts through a light emitting diode 16 and series resistor 17. The diode lights when current flows through it, which is to say whenever the transistor 13 is switched on. The diode and transistor are protected in conventional manner not further described herein against inductive voltage peaks. Switching the transistor 13 by a pulse train from the free running astable oscillator 11 causes current pulses to flow through the probe whenever it is connected to a termainal of a component to test the same. Such current pulses simulate accuating pulses for components such as the solenoids 21 of fuel injectors (Figure 2) normally actuated by pulses under the control of an electronic control unit 24. A relay 23 is permanently conducting whenever the engine is operative. The oscillator 11 can be connected to a built-in amplifier 18 having input leads 19 by which it can be connected to an inductive pick-up 20 for an ignition amplifier 25 (Figure 2) of an electronic ignition system, which also includes a coil 26 and a ballast resistor 27. The oscillator 11, which is in this position of the switch 12 in its monostable state, now outputs single pulses timed to the ignition pulses and the probe can be applied to the coil 26 to simulate the ignition amplifier 25 as a test thereof. With the switch 12 back in position to put the oscillator 11 into its free running astable state a train of pulses can be applied by the probe 14 to the coil 26 independently of the inductive pick-up 20 and ignition amplifier. The instrument can be made compact so that even with an internal 12 volt supply it is a hand held device. Whereas the principal uses for which the instrument was devised have been described above, it will be found useful in different ways. For example, it may be used to detect live points and earth points in a circuit - in the astable condition if the probe 14 is connected to earth, the light emitting diode illuminates continuously, whereas if the probe 14 is connected to a point at 12V potential, the diode will not be illuminated. CLAIMS

1. A test instrument for electric pulse-actuated engine components comprising a pulse generator adapted to simulate component actuating pulses and probe means connected to said pulse generator and adapted to contact said components to apply simulated actuating pulses thereto, and indicator means indicating the occurrence of pulses.

2. A test instrument according to claim 1, said pulse generator comprising an oscillator.

3. A test instrument according to claim 2, said oscillator comprising a free running astable oscillator producing a continuous pulse train.

4. A test instrument according to claim 2, said oscillator comprising a monostable oscillator and triggering means to trigger said monostable oscillator to produce single pulses.

5. A test instrument according to claim 2, in which said oscillator is switchable between a free running astable state and a monostable stake, state, and comprising triggering means to trigger said oscillator when in said monostable state to produce single pulses.

6. A test instrument according to claim 3 or claim 4, said triggering means comprising an amplifier and input means connected to said amplifier for inputting signals from an inductive pick-up in an engine to be tested.

7. A test instrument according to any one of claims 1 to 6, in which said indicator means comprise a light emitting diode.

8. A test instrument according to any one of claims 1 to 7, comprising an output stage transistor turned on by a pulse to connect said probe means normally held at a non-zero potential to ground.

9. A test instrument substantially as hereinbefore described with reference to the accompanying drawings.