TITLE : METHOD AND CONTROL UNIT FOR CONTROLLING AN ENGINE PUMP

FIELD OF THE INVENTION

This invention relates to a method and control unit for controlling an engine pump.

BACKGROUND TO THE INVENTION

Engines may be supplied with fuel by a supply system involving a pump. Aside from the need for pumping of fuel to supply the fuelling requirements of an engine, the need for pumping of fuel on start-up may arise from a problem for engines operated in hotter countries where fuel, having a relatively high volatility, may evaporate. In such case, a required minimum level of fuel, for example in a sump of the engine fuel supply, may not be achieved. Indeed, there may be no fuel available at all. Taking fuel supply to a carburetted engine as an example, fuel level in a bowl or sump of the carburettor may fall below the pilot jet or even be empty of fuel after a few days without use.

Pumps run to address this problem may be electrical pumps run from the engine battery when the "ON" position is selected on the engine start system. The operation of the pump ensures that there is an available supply of fuel for operation of the engine on demand by the engine operator. For example, it may be known that in a worst case scenario of the carburettor bowl being completely empty, a five second operation of the pump may be sufficient to fill such bowl. Once fuel is available and the engine has been cranked, the fuel pump will continue to draw power from the electrical system, which is now being supplied by the alternator of the engine.

However, and for various reasons, the vehicle operator may not crank start the engine even after the ignition has been switched on. This may happen due to traffic conditions where the operator may stop the engine running but leave the

ignition in the "ON" state or may otherwise be due to inattention of the vehicle operator. In such cases, the fuel pump is driven by the vehicle battery for a significant period of time potentially draining the battery. Because the operation of the pump may be relatively quiet, there may not be externally obvious signs to the operator that a significant electrical drain is continuing on the battery (unlike having headlights on, for instance).

Further, in the event of the fuel tank running dry, the fuel pump may continue to operate even though there is no fuel supply available. This situation can occur because the engine can run for some period of time on the fuel available in the fuel supply system outside the fuel tank, for instance the fuel contained in the carburettor bowl. Such a situation may result in damage to the pump, for instance due to the lack of fuel as a lubricating agent between sliding parts of the pump.

It is an object of the present invention to address the problem of inappropriate and random operation of pumps, for example, to ensure that sufficient fuel is available to enable effective operation of an engine without draining the vehicle battery or damaging an engine pump for delivery of fuel or hydrocarbon liquids to an engine.

SUMMARY OF THE INVENTION

With the above object in view, the present invention provides a method of controlling an engine pump supplying a hydrocarbon liquid to an engine wherein a control unit starts the pump and stops it after a predetermined period of time of pump operation.

The control unit, which may be an engine control unit or pump control unit, incorporates a timer for timing a period of operation of the engine pump so that if, for example, timed engine pump operating interval exceeds that programmed into the control unit, the engine pump is stopped. Such stopping of the pump may

occur in any event (unconditionally) or continued operation may be made conditional on values of other engine operating conditions such as crankshaft speed and fuel flow state through the pump confirming allowable pump or normal pump operation.

In a conditional stopping methodology, if a predetermined engine pump operating time interval exceeds that programmed into the control unit, then operation of the pump will be stopped unless other engine operating conditions confirming normal engine operation, and appropriateness of continued pump operation, are met. For example, such engine operating conditions may include crankshaft speed, liquid (such as fuel) flow state and time since actuation of an engine starting means. Fuel state may relate to liquid flow state through the pump. Crankshaft speed indicating cranking and fuel flow state demonstrating fuel flowing appropriately through the pump are each conditions which may be assessed prior to allowing continued operation of the pump. Accordingly, they may be used separately or together in the control of the engine pump. Continued operation of the pump should not be though the battery. Rather the pump preferably draws power from the engine alternator after cranking. The crankshaft speed is a particularly important engine operating condition to be taken into account in accordance with the method of the invention. Pump operation may be stopped after a predetermined interval of time if the crankshaft speed is below a predetermined threshold level, for instance if it is detected that the engine is not running or the crankshaft speed is below cranking speed. Liquid or fuel flow state detection is optional being preferred as a criterion which helps to protect the pump from dry running. In that case, engine pump operation is stopped if liquid, such as fuel, flow level is below an acceptable flow level, for example if no fuel is flowing through the engine pump.

If, as likely, the engine pump is an electrical pump, the supply of current to the engine may be stopped by opening of a switch in the fuel pump circuit after the timer counts the predetermined engine pump operating interval.

Dependent on sensed engine operating conditions, the method may be run iteratively, or through a plurality of iterations, that is, the controlled stopping of the pump on one occasion not precluding the pump being run again when at least one decision criterion confirming normal operation and/or allowing continued pump operation is met. The decision criterion may be selected from the group of conditions consisting of elapsed time since last stopping of the engine pump or attainment of a crankshaft speed above a predetermined threshold level.

The engine pump is advantageously an electrical pump used for pumping of fuel, a hydrocarbon liquid, in a vehicle. However, the method could be applied to the pumping of lubricant.

The method is particularly applicable where a starting means or ignition switch of the engine has been enabled. So, the method may be advantageously applied after the engine ignition switch has been enabled or switched on. Similarly, when the starting means or ignition switch has been turned off, the control unit timer may be reset so that the method may be implemented when next the engine ignition switch is enabled. The control unit may control operation of the engine pump dependent on the elapsed since the engine ignition switch was last enabled. For instance, if the system has been operating in the recent past (that is, such that it was a reasonable assumption that the fuel bowl of a carburettor had not had sufficient time to evaporate dry) then the system may advantageously not require the pump to operate until the engine had started. Thus the electrical load on the engine during the "cranking" phase may be reduced thus better ensuring that sufficient electrical power is available for starting the engine.

The engine pump operating time period may be selected by the engine control unit, either by pre-programming dependent on the engine pump to be employed or as a function of other engine conditions, typically at start-up and as above described. In this way, the pump may be operated for an appropriate controlled period of time to initiate fuel supply to the engine independently of

random action or inaction from the engine operator. However, the engine operator may be informed of the control strategy by written instructions, available in an engine manual. Typically, the engine forms part of a vehicle so the written instructions may form part of a vehicle manual.

The liquid or fuel flow state through the pump, where used as a control parameter, may be measured in any desired manner whether or not involving direct flow detection. However, this may not be quantitatively precise. The state may be rated as "acceptable" or "unacceptable", a binary evaluation. This state may be determined following input of sensed output pump flow to the engine control unit. Again, flow detection avoids guesswork by the vehicle operator as to fuel tank level. If no or low flow is detected, the engine pump may be stopped to prevent dry running and protect the engine pump.

The engine control unit for controlling the engine pump supplying a hydrocarbon liquid to the engine may be appropriately programmed with logic to operate the engine pump control strategy, this engine control unit forming a further embodiment of the present invention.

In this aspect, the engine control unit comprises: a) a micro-controller for controlling operation of an engine pump; and b) a timer for timing a period of operation of the engine wherein the micro controller is programmed with logic to start operation of the engine pump; and stop operation of the engine pump after a predetermined period of time counted by the time.

The engine control unit may receive input from the timer as well as data from engine condition sensors, such as crankshaft speed sensors, flow detectors and other engine operating condition sensors, data from the engine condition sensors causing actuation of the engine pump by the control unit when sensed conditions meet predetermined pump operation decision criteria and stopping the pump when sensed conditions meet predetermined pump stopping decision

criteria. In the latter case, pump operating time period exceeding that programmed into the control unit is a primary pump stopping decision criterion.

The engine pump control method and control unit is suitable for many types of engine. Carburetted engines are the prime focus of concern. More robust pumps are typically required in fuel injected engines which operate at higher fuel pressures and in a closed circuit not subjected to evaporation, than encountered in typical carburetted engines and this excludes some of the problems addressed by the present invention. The control method and unit are particularly applicable where the fuel tank and carburettor bowl or sump are substantially separated in height such that the pump has a greater head to overcome (that is, pump duty) before the requisite amount of fuel may be supplied to the carburettor bowl. These pumps are typically referred to as "lift" pumps as their primary duty is simply to lift the fuel from a supply height to a delivery height, there being no real need (as compared to fuel injected systems) for high pressures to be maintained.

Further, because the engine pump is stopped in a controlled manner, excessive drain on the battery may be avoided. This may be particularly important where the battery has limited capacity, up to about 9Ah.

The engine pump control method and control unit are particularly suitable for use in two wheel vehicles, such as motorcycles, particularly where the battery may have limited capacity, up to about 9Ah.

BRIEF DESCRIPTION OF THE DRAWINGS

The method and control unit for controlling the engine pump in accordance with the invention may be more fully understood from the following description of the method made with reference to the accompanying drawings in which:

Figure 1 is a schematic view of a motorcycle employing the engine pump control method in accordance with one embodiment of the present invention;

Figure 2 is a schematic view of an engine fuel supply system for the motorcycle shown in Figure 1 and fuel supply system shown in Figure 2;

Figure 3 is a top sectional view of an electrical fuel pump employed in the motorcycle shown in Figure 1 ;

Figure 4 is a block diagram of a pump control unit for implementing the engine pump control method in accordance with one embodiment of the present invention;

Figure 5 is a block diagram of a starter motor control unit used in implementing the engine pump control method in accordance with one embodiment of the present invention;

Figure 6 is a schematic or flowchart of the control strategy used to control operation of the electrical fuel pump shown in Figure 3 in accordance with one embodiment of the present invention and employing fuel flow state detection;

Figure 7 is a schematic or flowchart of the control strategy used to control operation of the electrical fuel pump shown in Figure 3 in accordance with a second embodiment of the present invention without fuel flow state detection;

DETAILED DESCRIPTION OF THE DRAWINGS

Referring now to Figure 1 of the present invention, there is shown a motorcycle 10 which has a carburetted engine 15 operated on liquid fuel. The method could be employed for control over the liquid fuel supply in a dual fuel engine also using LPG or CNG as a gaseous fuel. Such liquid fuel supply may be a secondary fuel supply. Referring also to Figures 2 and 3, fuel is supplied to carburettor 16 of engine 15 by electric fuel pump 20. Fuel pump 20 has a fuel inlet line 27 drawing filtered fuel by suction from fuel tank 40; and a fuel outlet line 28 for supplying fuel to engine 15. Fuel pump 20 also has a fuel return line 30 communicating the fuel pump 20 with a fuel tank 40 which is located beneath the floorboard 1 1 of the motorcycle 10. A fuel flow detection sensor 28a is located in

fuel outlet line 28 downstream of the fuel pump 20, this sensor 28a indicating fuel flow state through fuel pump 20.

The carburettor 16 is of slide type located in the intake manifold 17 of engine 15 and the carburettor position at a distance H above the fuel pump 20 may be observed. The carburettor 16 may drain of fuel over several days of non- use of the motorcycle 10 and operation of fuel pump 20 allows fuel to once again be supplied to the carburettor 15 when the motorcycle 10 is next used.

The fuel pump 20 is an electric pump run on a DC supply (battery) on start up of the engine 15 and is shown in detail in Figure 3. It has a fuel inlet 27 and fuel outlet 28. The fuel pump 20 has a spring 25 biased in the direction of the fuel outlet 28. Spring 25 is connected to a plunger 26, of ferromagnetic material, which provides the capacity to draw fuel into the fuel pump 20 through fuel inlet 27 and expel- it through the fuel outlet 28 during pump 20 operation. Turning to pump operation, the fuel pump 20 has a coil 24, which is energised pulse wise by the battery. When the coil 24 is energised, it magnetises. When coil 24 is de- energised it de-magnetises. The movement of plunger 26 changes in direction in accordance with the magnetisation state of the coil 24. As it changes direction, it changes between a fuel suction stroke and a fuel expulsion stroke allowing fuel to be supplied to engine 15. The operation of fuel pump 20 is controlled by pump control unit 110 and, ultimately, starter motor control unit 120 shown in Figures 4 and 5 respectively. The battery has limited capacity up to about 9Ah.

The fuel pump control unit 1 10, shown in Figure 4, shows that - on closing of an ignition switch 135 - a circuit between fuel pump 20 and battery 50 is closed allowing operation of the fuel pump 20. The fuel pump 20 is operated in pulse wise manner and to this end the pulses are controlled by the pulser coil 1 12, wave shaping circuit 114 and micro-controller 116 which provides drive signal to fuel pump driver 118, all a part of the pump circuit, which operates fuel pump 20. A fuel pump 20 operation timer is employed to measure fuel pump 20 operating

time interval. When fuel pump 20 is to be stopped, a switch in the pump circuit is opened and power delivery to fuel pump 20 is stopped.

The pump control unit 110 and starter motor control unit 120, shown in Figure 5, forms part of an engine control unit and implements the engine pump control method of the present invention. Several of the components of the fuel pump control unit are also shown in this block diagram. The micro-controller 1 16 takes signals of brake switch 122, starter switch 124 and engine temperature sensor 126.

The method and operation of the control unit 120 will now be described with reference to the control strategy schematic of Figure 6. First, the operator of motorcycle 10 switches on the ignition for engine 15 by enabling an ignition switch (not shown). Control units 110 and 120 are therefore powered by the battery and operational to receive input signals for crankshaft speed, and flow of petrol through line 28. Fuel pump 20 may then be operated in accordance with a conditional stopping methodology in which pump operating time, outlet fuel flow at outlet 28 and crankshaft speed are used as decision criteria confirming normal operation or allowable pump running to determine whether fuel pump 20 operation is to be continued. The stopping of fuel pump 20 could be unconditional with operation being stopped after a determined time of operation or determined time since starting. A simple logic like this still acts to protect fuel pump 20 but is less expensive to implement.

So, with fuel pump 20 on and pump operation timer started, crankshaft speed is compared with set point of IOOrpm (a value, related to cranking, that may vary with the vehicle and application). If crankshaft speed falls below the threshold value, the fuel pump 20 is run for 5 seconds with crankshaft speed continuing to be sensed. The speed comparison loop is exited once crankshaft speed reaches the threshold value. Once fuel pump 20 operating time reaches 5 seconds, fuel pump 20 operation is stopped in any event as an engine 15 operating problem is likely indicated. The motorcycle 10 operator may be

informed accordingly. Memory in control units 110 and 120 may store data regarding the event and this may be used to stop or control fuel pump 20 operation, the next time that engine 15 is operated. If a fault is indicated, fuel pump 20 operation may be prevented on the next occasion the ignition switch of engine 15 is switched on or enabled.

If crankshaft speed exceeds the 100 rpm threshold value, fuel flow sensor 28a determines whether there is an outflow of fuel through outlet 28. If fuel is flowing, the timer may be reset for next implementation of the fuel pump 20 control strategy. If "no flow" is sensed, the timer continues to run and the fuel pump delivers fuel for 30 seconds with flow continuing to be sensed by flow sensor 28a. The flow sensing and comparison loop may be performed iteratively, or through an indeterminate number of iterations or stopped after a certain number of iterations as a leakage or other engine 15 operational problem may be indicated. The motorcycle 10 operator may also be informed accordingly.

Alternatively, the flow comparison loop may be exited, once sensed flow reaches an acceptable state (flow ON or flow threshold value reached) and the timer reset for next implementation of the fuel pump 20 control strategy.

Dependent on sensed engine operating conditions, the method may run through a plurality of iterations, that is, the controlled stopping of the pump on one occasion does not preclude the pump being run again after a period of time has elapsed or other decision criteria confirming appropriateness of fuel pump 20 operation have been met. So, if fuel pump 20 is stopped, the operation timer may be reset. It is to be understood also that the threshold values above are used for illustration only and are to be set with reference to considerations such as the vehicle type, vehicle application, pump type and other engine design and operating considerations.

Figure 7 shows an alternative control strategy where fuel detection is not employed. This simplifies the control strategy, which is otherwise the same as

above. However, in this case, fuel pump 20 operation timer is reset if crankshaft speed reaches the 100 rpm threshold value in readiness for the next implementation of the control methodology. If crankshaft speed is below this threshold, the fuel pump 20 is operated for 5 seconds, the fuel pump 20 then being stopped and the timer reset. Further iteration(s) of the fuel pump 20 control strategy may be permitted or stopped once a fault is indicated. Again, the motorcycle 10 operator may be informed of this fact.

The control strategies of Figures 6 and 7 allow fuel pump 20 to be protected through operation for an appropriate controlled period of time to initiate fuel supply to the engine 15 independently of random action or inaction from the engine operator. This prevents or minimises the risk of dry running of fuel pump 20 as well as excessive drain on the limited capacity battery.

Modifications and variations to the engine pump control method and control unit of the present invention may be apparent to the skilled reader of this disclosure. Such modifications and variations are within the scope of the present invention.