GB2296097A - Internal combustion engine analyser - Google Patents

Abstract

An apparatus for analysing parameters of an internal combustion engine comprises a personal computer 10 having a monitor 13, and an interface unit 11 connected to a parallel port of the computer 10. The interface unit is connected to a plurality of probes and sensors 26, 31, 34, which are arranged to monitor the operating parameters of the engine. The computer 10 is arranged to display the values of the monitored parameters on its monitor 13, so that the parameters can be analysed. The computer 10 may comprise a database which stores limits and/or ideal values of the operating parameters of different types of engine, so that comparisons can be made between them and the actual measured values and possible causes of error indicated. <IMAGE>

Description

INTERNAL COMBUSTION ENGINE ANALYSER This invention relates to an apparatus for analysing operating parameters of an internal combustion engine.

Internal combustion engines have various operating parameters, such as fuel mixture and ignition timing, which need to be checked and adjusted regularly. Hitherto, these operating parameters have been checked using a plurality of complicated items of test equipment. The results obtained from the test instruments are often complex to analyse, particularly when it is necessary to simultaneously study several parameters in combination. This process is further complicated because the ideal value of these parameters varies between different makes and model of engine.

I have now devised an apparatus for analysing parameters of an internal combustion engine which alleviates the above-mentioned problems.

In accordance with this invention there is provided an apparatus for analysing parameters of an internal combustion engine, the apparatus comprising a computer including a monitor and an interface unit connected to a port of the computer, the interface unit being connected to a plurality of remote transducers arranged to monitor operating parameters of an internal combustion engine, and the computer being arranged to display the values of said monitored parameters on the monitor.

In use, the information displayed on the monitor will depend on the parameter being monitored, for example in instances where two or more parameters need to be simultaneously studied, the monitor conveniently displays them together.

Preferably the interface unit is connected to a transducer for measuring exhaust emissions from the engine.

Alternatively the transducer may be mounted in the interface unit.

Preferably the interface unit is connected to means for sensing values, such as the frequency and period of electrical pulses output from an ignition system of the engine. The monitor is preferably arranged to display the frequency of the rotational speed of a rotational shaft of the engine. This may be derived from the frequency of the ignition pulses.

Many internal combustion engines comprise contact breaker points which cause a high voltage to be induced in an ignition coil. The points are opened and closed by a cam driven by the engine. If the gap between the points is too small when they open, then the voltage induced in the coil will be too low. If, however, the gap is too large, then the charge stored in the coil will not have sufficient time to grow to its full value in readiness for the next ignition spark.

Consequently engine manufacturers specify an angle of rotation of the cam that the contact points should remain closed. This so-called dwell-angle can be altered by adjusting the gap between the open contact points.

Preferably the monitor is arranged to display the dwell angle. The dwell angle may be derived from the period and frequency of the ignition pulses.

Preferably the interface unit is connected to a strobe light. The strobe light is preferably triggered by signals from an ignition-sensing transducer.

Preferably the interface unit is connected to means for monitoring voltage, current or resistance values of electrical circuits connected to the engine.

Preferably the computer comprises a personal computer or so-called PC.

Preferably the computer comprises a data base containing the limits and/or ideal values for the operating parameters of a plurality of different types or makes of engine, the computer comprising means for enabling the user to select the make or type of engine being analysed. Preferably the computer comprises means for entering details onto the database, for example when the user's type or make of engine is not on the database.

Preferably the computer is arranged to compare the value of the monitored parameters with said limits and/or ideal values from the database, and provide an indication of possible causes of any errors in the monitored parameters.

An embodiment of this invention will now be described by way of example only and with reference to the accompanying drawings, in which: FIGURE 1 is a schematic diagram of an apparatus for analysing parameters of a vehicle's internal combustion engine in accordance with this invention; FIGURE 2 is a diagram showing the monitor display of the apparatus of Figure 1, when in the multimeter mode; FIGURE 3 is a diagram showing the monitor display of the apparatus of Figure 1, when in the ignition timing mode; and FIGURE 4 is a diagram showing the monitor display of the apparatus of Figure 1, when in the carburation mode.

Referring to Figure 1 of the drawings, there is shown an apparatus for analysing the parameters of a vehicle internal combustion engine, the apparatus comprising a conventional personal computer 10 connected to an external interface 11.

The computer 10 comprises a keypad 12, monitor 13 and printer 15 connected to a control unit 14. A mouse (not shown) may also be connected to the control unit 14.

The interface 11 is connected to a parallel input/output terminal on the rear of the computer's control unit 14 via a multi-core cable 16. The interface unit 11 comprises a housing which houses an electronic circuit 17.

The electronic circuit 17 comprises AC and DC power supplies 18, 20 which are fed from a mains transformer 19. The power supplies feed AC or DC power as appropriate to each of the component parts of the interface. An elongate flexible tube 21 extends from the housing and is provided at its free end with a probe 22 for inserting into the exhaust of the internal combustion engine. The exhaust gases are drawn through a filter 23 and along the tube 21 by means of a pump 24 mounted inside the unit. The exhaust gases are then fed through a gas collector 25 to a measuring cell 26 which determines the type and quantity of its constituent gases. The signals from the cell 26 are fed through an amplifier 28 and scanner 29 to an analogue-to-digital (A-to-D) converter 30 via a mode selection switch 39.

An electrical contact probe such as a so-called crocodile clip 31 is connected via a long lead to the interface unit. In use the probe 31 is attached to the lead which feeds pulsed signals from the contact points to the low tension side of the ignition coil. The signal from the probe 31 is fed to the mode selection switch 39 and also to the scanner 29.

A probe 32 for attaching to an H.T. ignition lead of the engine is connected via a long lead to a firing circuit 35 in the interface unit 11. The probe 32 inductively couples with the ignition lead, through its insulating layer, such that each time an ignition pulse appears on the lead an electrical output signal is fed from the probe 32 to the firing circuit in the interface unit 11. The firing circuit 35 generates pulses which fire a strobe light 33 that is connected to the interface unit.

In use, the probe 32 is attached to an H.T. lead of a cylinder that is associated with a reference mark on the vehicle's flywheel. The ignition pulse to the cylinder should occur at say 120 - 50 before the piston of that cylinder reaches top dead centre. The strobe can be used to illuminate the flywheel to give a visual indication of the angle at which ignition occurs.

A pair of external electrical probes 34 are connected to a multimeter circuit 36 inside the housing. The circuit 36 comprises a switch 37 which is used to select the voltage or current range of the multimeter. Signals from the multimeter circuit are fed via the mode selection switch 39 to the A-to-D converter 30.

The A-to-D converter 30 converts the analogue signals from the probes and sensors 26, 31, 34 to digital signals and outputs these in parallel along the cable 16 to the computer 10. The computer 10 is loaded with a program which analyses the digital signals from the interface unit 11 to produce a variety of user-selectable modes of the apparatus.

Referring to Figure 2 of the drawings, when the switch 39 is turned to select the multimeter mode of the apparatus, a visual indication 40 of the voltage, current or resistance at the probes 34 is given on the monitor. The display also shows at 41 the selected multimeter range. Other data, such as the make and model of the vehicle, and its registration number are also displayed on the screen at 42 for reference.

This data is entered into the computer by the user using the keypad 12 at the start of the tests. The time and date may also be displayed at 43 and 44. The user can change the multimeter range using the switch 37 on the interface unit 11.

In an alternative embodiment the multimeter range may be changed using keys on the keyboard 12. A menu-bar 45 is provided at the bottom of the display to show which keys on the keyboard 12 are used for changing to alternative modes of the apparatus. The menu bar 45 may also show the keys used for changing multimeter ranges.

Referring to Figure 3 of the drawings, in an ignition mode of the apparatus, a graphical indication of the dwell angle is given at 46. The ideal dwell angle for the engine under test is also given at 47: this information is obtained from a database in the computer using the make and model information input by the user at the start of the tests. The number of revolutions per minute (CRPM) of the engine's crank shaft is displayed alongside the graphical display 46 at 48: this is so that the user can check that the dwell angle remains substantially constant over a range of engine speeds. The computer 11 calculates the dwell angle using data from the probe 31. The engine speed is also calculated using data from the probe 31. The display may also provide an indication at 49 and 50 of the upper and lower engine idle speed limits respectively.

Referring to Figure 4 of the drawings, in a carburation mode of the apparatus, the display gives the composition of the exhaust gases: these may include the carbon monoxide content 51 and the hydrocarbon content 52. The maximum limit of the carbon monoxide content is given at 53. A stop watch facility may be provided at 54, so that the exhaust gas tests can be carried out over predetermined time periods. Also, the engine speed is displayed at 48 alongside the composition of the exhaust gases, so that the exhaust gas tests can be carried out over a range of engine speeds.

It will be appreciated that the computer gives clear and concise indications to the user of the operating parameters of the engine of his/her vehicle. The computer may be arranged to examine the readings obtained and suggest possible causes of any errors. A list of readings and/or a list of possible errors may be printed out by the printer 15.

In an alternative embodiment the apparatus may include other transducers such as for measuring engine knock and cylinder compression.

Claims (16)

1) An apparatus for analysing parameters of an internal combustion engine, the apparatus comprising a computer including a monitor and an interface unit connected to a port of the computer, the interface unit being connected to a plurality of remote transducers arranged to monitor operating parameters of an internal combustion engine, and the computer being arranged to display the values of said monitored parameters on the monitor.

2) An apparatus as claimed in claim 1, in which the interface unit is connected to a transducer for measuring exhaust emissions from the engine.

3) An apparatus as claimed in claim 1, in which the interface unit comprises a transducer for measuring exhaust emissions from the engine.

4) An apparatus as claimed in any preceding claim, in which the interface unit is connected to means for sensing values of electrical pulses output from an ignition system of the engine.

5) An apparatus as claimed in any preceding claim, in which the monitor is arranged to display the rotational speed of a rotational shaft of the engine.

6) An apparatus as claimed in claim 5 as appended in claim 4, arranged to derive the rotational speed from the frequency of said ignition pulses.

7) An apparatus as claimed in any preceding claim, in which the monitor is arranged to display the dwell angle of contact breaker points of the engine.

8) An apparatus as claimed in claim 7 as appended to claim 4, arranged to derive the dwell angle from the period and frequency of said ignition pulses.

9) An apparatus as claimed in any preceding claim, in which the interface unit is connected to a strobe light.

10) An apparatus as claimed in claim 9, in which the strobe light is triggered by signals from an ignition-sensing transducer.

11) An apparatus as claimed in any preceding claim, in which the interface unit is connected to means for monitoring the electrical values of electrical circuits connected to the engine.

12) An apparatus as claimed in any preceding claim, in which the computer comprises a personal computer.

13) An apparatus as claimed in any preceding claim, in which the computer comprises a data base containing the limits and/or ideal values for the operating parameters of a plurality of different types or makes of engine, the computer comprising means for enabling the user to select the make or type of engine being analysed.

14) An apparatus as claimed in claim 13, in which the computer comprises means for entering details onto the database.

15) An apparatus as claimed in claim 13 or 14, in which the computer is arranged to compare the value of the monitored parameters of the engine with said limits and/or ideal values from the database, and provide an indication of possible causes of any errors in the monitored parameters.

16) An apparatus substantially as herein described with reference to the accompanying drawings.