Description of Invention

This invention relates to the instrumentation and control of power units. Particularly, but not exclusively as explained hereafter, the invention is useable with internal combustion engines.

Many internal combustion engines, particularly those used in on-highway and off-highway motor vehicles, large and small, are now electronically controlled.

The precise control of the operating conditions of an engine which can be achieved using electronic control is essential if an engine is to meet the requirements set by regulations for exhaust emissions, fuel economy, noise, and so forth. The electronic control of an engine is usually effected by an electronic engine control unit (ECU) forming part of a control area network

(CAN) which forms part of the overall electrical system of the motor vehicle or other equipment where the engine is used.

Engines whose original intended use was in motor vehicles for example can also be used in other situations. For example, a diesel engine whose primary use is in trucks or passenger-carrying vehicles might be used to power an electrical generating set or some agricultural or construction machinery. Such an engine might be controlled by the same ECU as is used when it is in a motor vehicle, and use the same control area network, but the rest of the vehicle's electrical system is not of course present. This is of significance in that there is no provision of the instruments indicating the engine's operating conditions (such as oil pressure, coolant temperature, oil temperature and so forth). In current motor vehicles, such instruments are usually electronic instruments incorporating digital displays and the like, which are integrated with the electrical system of the vehicle in the sense that they receive

electrical signals, which might be digital signals, from the engine's CAN by way of the vehicle's electrical system.

When an engine intended for a particular application is used in other situations, it would be possible to provide instruments which interface with the engine's ECU and CAN in the same way as the instruments would in the original application. However, this is an expensive option since special- purpose electronic systems would have to be provided to interface with the engine's ECU and to provide signals to compatible instruments. Such instruments might be digital displays e.g. of the liquid crystal type, or in the case of instruments giving an analogue display on a dial might use stepper motors to move a needle in relation to the dial. Such instruments, as well as being expensive, require highly specialised attention if a problem develops, which attention might not be readily available where a generating set for example is to be used.

An alternative approach to the instrumentation of an engine under such conditions is to provide the engine with additional sensors/transducers for the various operating parameters, and provide additional electrical circuits connecting them to the "traditional" instruments of the moving coil-type for example. Such instruments are inexpensive, robust and more easily able to be understood and maintained by less-skilled personnel. The disadvantage is that this approach incurs the cost of duplicating sensors which may already be present on the engine, and may require engine modifications to fit the duplicated sensors. The latter could have warranty implications (unauthorised alterations to an engine could invalidate the manufacturer's warranty).

Hence there is a requirement for providing instrumentation for an electronically-controlled engine in such circumstances, in a manner in which the above-described problems are overcome or reduced.

According to one aspect of the invention, we provide a method of displaying the value of an operating parameter of an electronically controlled power unit, comprising deriving a signal from an ECU of the power unit to represent the operating parameter; converting the signal to a pulse width modulated signal representative of the parameter; and supplying the pulse width modulated signal directly or indirectly to a display instrument to display the value of the parameter.

The value conveniently is displayed on a moving coil display instrument. Such instruments are robust and reliable, and well known even to those who might not be familiar with digital displays or electronically-operating instruments.

The method may include further controlling the pulse width modulated signal in accordance with a reference voltage signal derived from the ECU. Moving coil instruments are voltage-sensitive, so controlling the pulse width modulated signal in accordance with a prevailing system voltage can be used to increase the accuracy of display by a moving coil instrument.

A further aspect of moving coil instruments is that their response to an applied signal is non-linear over their display range. Therefore the pulse width modulated signal may be further controlled in dependence on its level to increase the accuracy of the displayed value. Conventionally, the non-linearity of a moving coil instrument is matched to the non-linearity of the transducer providing the signal to which it is connected, so that accuracy is increased over the entire range of reading of the instrument between zero and full scale deflection. In accordance with the present invention, accuracy may be increased by matching the non-linearity of the instrument to a non-linearity in the pulse width modulated signal to which it responds. The pulse width modulated signal may be controlled in accordance with an algorithm which changes the relationship of the pulse width modulated signal to the derived

signal at a number of points between zero and full scale deflection of the instrument.

The power unit preferably is an internal combustion engine, although it may alternatively be on electrically-powered motor for example.

For example, some machines or vehicles, for example battery-powered forklift trucks, use an electronically-controlled motor with an ECU and CAN, and require instrumentation to display hours run, battery voltage, and so forth. The invention may be useable in such a situation.

The method may further comprise providing a signal to control an aspect of the engine's operation. One such signal which may be provided is one which causes the engine to be shut down, e.g. if the value of an operating parameter of the engine varies from predetermined values or from within predetermined limits. By way of example, engine shut-down might be required in the event of high coolant temperature or low oil pressure.

Engine shut-down under such conditions may be something which is provided for in the engine' ECU. However, when such shut-down occurs, it might require factory or authorised service agent resetting of the ECU before the engine can be re-started, even if any fault causing the shut-down has been rectified. In accordance with the invention, engine shut-down can be caused to take place before a condition has been reached to which the ECU would respond, so that after the shut-down resetting of the ECU is not required. By way of example, one situation in which the engine might be shut down is if a sudden drop in oil pressure occurs for no apparent reason, but without its falling to a level at which the engine's ECU would cause the engine to shut down.

Such a signal may be applied to a shut-off valve in the engine's fuel supply.

A further engine operation which might be controlled is starting the engine, with a signal being applied to a starter relay. Yet a further condition which could cause an engine-controlling signal to be given is engine over-speeding.

According to a second aspect of the invention, we provide apparatus for displaying the value of at least one operating parameter of an electronically controlled power unit, comprising means for deriving at least one signal from an ECU of the power unit to represent the operating parameter(s); means for converting the signal(s) to at least one pulse width modulated signal representative of the parameter(s); and means for supplying the pulse width modulated signal(s) directly or indirectly to at least one display instrument to display the value of the or each parameter.

The apparatus may include at least one moving coil display instrument to display the value of the or each parameter.

Preferably the apparatus further includes means for deriving a reference voltage signal from the ECU, and for controlling the pulse width modulated signal(s) in accordance with the reference voltage signal. Preferably also there is means for controlling the pulse width modulated signal(s) in accordance with an algorithm effective at a number of points between zero and full scale deflection of the instrument(s) (i.e. a maximum value of the or each signal).

The invention also provides a power unit, preferably an internal combustion engine, provided with apparatus according to the second aspect of the invention.

Means for providing a signal to control an aspect of the engine's operation may be provided, e.g. to cause the engine to be shut down.

The invention will now be described by way of example with reference to the accompanying drawings, of which

FIGURE 1 illustrates diagrammatically the principle of the invention; FIGURE 2 is a block diagram showing the elements of an embodiment of the invention; FIGURE 3 illustrates diagrammatically a further embodiment of the invention; FIGURE 4 is a block diagram illustrating the elements of the embodiment of Figure 3.

Referring firstly to Figure 1 of the drawings, this shows apparatus in accordance with the invention. It comprises a central process module, indicated at 10, which is electrically connected at 11 to the control area network of an electronically controlled internal combustion engine, in such a way as to be able to read the data carried by such network as to various operating parameters of the engine. By way of example only, in relation to an engine in a road vehicle, such parameters may include hours run, engine oil pressure, engine coolant temperature, battery voltage, battery current, percent load at current rpm, transmission oil pressure, transmission oil temperature, engine oil temperature, brake pressure, fuel data, and so forth. For the engine's use in a generating set or other application, the apparatus 10 converts signals relating to those parameters which are relevant to the engine's use and converts them to pulse width modulated signals which can be displayed directly or indirectly by moving coil display instruments indicated at 12. Any required number of such instruments can be provided.

Figure 2 shows an engine's CAN bus 20, a CAN transceiver 21 and a CAN engine 22. The module 10 has a central processor 23 which processes the

signals from the engine's CAN. A pulse width modulator unit 24 is included, providing pulse width modulated signals, representing required operating parameters of the engine, to suitable driving circuits 25 and then to moving coil gauges 26 to display the values of the required engine parameters. Also shown is a tachometer 27 which is not driven by a pulse width modulated signal since tachometers are usually frequency-driven. However it would be possible for the invention to provide a pulse width modulated signal representing engine speed, which can be displayed on a simpler tachometer instrument.

Referring now to Figures 3 and 4 of the drawings, these respectively illustrate the principle and elements of apparatus in accordance with a further embodiment of the invention. The basic principles and elements are as above described in relation to Figures 1 and 2, and therefore the same reference numerals are used for corresponding parts. In this embodiment, the main control module 10 has additional outputs which as illustrated are connected to a fuel shut-off valve 15 and an engine starter relay 16, providing for the engine to be stopped and started when required.

Figure 4 shows the driver circuits 25 have outputs to relays 28, 29 for the fuel valve 15 and starter 16. Also shown in Figure 4 is a setting input 30 to the central processor 23 which can be set to represent an engine over-speed value which could cause the engine to be shut down. The central processor also monitors the values of the engine operating parameters which it is causing to be displayed, and can provide for engine shut-down if any of those parameters deviate from acceptable values or rise above or fall below acceptable limits, or vary unexpectedly. Engine shut-down is caused in such circumstances by applying a signal to the fuel valve relay 28 causing closure of the fuel shut-off valve 15.

Also shown in Figure 4 is that there may be a display 31 of warning lights or the like, e.g. LED indicators, which can give an indication of the values of the engines operating parameters if they deviate from those which are normal or acceptable, or, in the event of engine shut-down, operate to indicate the cause of such shut-down.

When used in this specification and claims, the terms "comprises" and "comprising" and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps or components.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.