Speed limiter

Details Speed limiter Speed limiter

2002-04-23

2004-06-29

Huynh, Hai (Department: 3747)

Internal-combustion engines

Engine speed regulator

Engine speed reduction by fuel cutoff

C123S352000

Reexamination Certificate

active

06755177

ABSTRACT:

FIELD OF INVENTION
This invention relates to an improved method for controlling the engine speed of an internal combustion engine, and is particularly, though not exclusively, useful in relation to water vehicles or watercraft and motorcycles or scooters.
BACKGROUND INFORMATION
Internal combustion engines are used in a wide variety of applications, such as in motor vehicles (cars, all terrain vehicles and two-wheeled vehicles) and watercraft including personal watercraft (PWCs) and outboard engines for boats. In many of these applications, it may be important in the operation of the engine to be able to govern or limit the rotational speed of the engine under certain circumstances.
For example, a requirement to limit engine speed may arise in order to protect an engine from damage which could be sustained during overly high speed operation, or to limit the overall speed of the vehicle or craft being powered by the engine. One such reason for limiting the speed of the engine may be to provide or enable a lower engine speed “limp-home” mode of operation in response to certain information returned from a specific engine sensor or in response to a specific device failure. Such speed limiting or governing may also be desirable in instances where the operator of a vehicle or craft is inexperienced or if maximum speed limits are provided for a given situation.
PWCs represent one particular engine application where speed limiting may be desirable so as to control engine speed to a level lower than the normal maximum speed limit or capability of the engine. Such speed limiting may be particularly applicable where children or lesser experienced riders will be operating the PWC and additional safety is of concern. By way of such speed limiting, the rider will be unable to achieve the maximum speed of the engine or craft, this speed being likely to prove dangerous or unmanageable for the young or inexperienced rider. Accordingly, the rider's safety is enhanced by restricting the maximum attainable speed of the engine or craft to one that is within the operational capabilities of the rider.
Such speed limiting may also be desirable for hire or rental organisations who may wish to preserve and prolong the usefulness of the products that they make available to the public by restricting the maximum attainable speed of an engine or craft. In this way, the craft is prevented from repeatedly operating at its upper or maximum limit and hence the longevity of the craft and engine thereof can be enhanced. This may be particularly desirable for engines which do not have a maximum speed control except for the engine's natural maximum limit, leaving the engine particularly susceptible to damage from operation at overly high speeds.
Still further, certain legislative bodies are now regulating for lower maximum speeds in particular waterways and roads in built-up areas. Accordingly, the proliferation of such legislated speed limited zones is a further example of where it may be desirable to be able to limit the engine speed of a vehicle or craft.
In recent times, mechanical devices such as governors have been used, and developments in the electronic control of engines have resulted in a greater ability to govern or limit the speed of internal combustion engines. For example, in one such development, it has been proposed to prevent further increases in rotational speed once the engine has reached a preset limit by skipping combustion events. In such a method, typically, an ignition event is simply not scheduled for a particular engine cylinder, and a corresponding combustion event does not occur. This method however has the disadvantage that fuel is still delivered into the combustion chamber, and typically passes out through the engine exhaust system into the environment unburnt. This is both a significant waste of fuel and harmful to the environment. Additionally, residual unburnt fuel can remain in the combustion chamber and adversely affect the following combustion event by reducing the predictability and certainty with regard to the amount of fuel which will be combusted.
A further issue with certain existing speed governing systems is that the rider or operator is completely “removed from the loop” during the period that the engine is operating under such speed governed conditions. That is, whilst the engine speed is being restricted to a certain predetermined limit, the operator effectively has little to no input in regard to the operation of the engine and a suitable controller determines what the specific engine event timings will be to maintain the speed at the preset level. Such operation may not be desirable in all situations and may have certain issues associated therewith.
For example, if the load on the engine was to increase whilst a speed limited mode was enabled, a typical controller would increase the fuelling rate to the engine in order to maintain the predetermined engine speed. However, this increase in fuelling would result without any regard to the operator. Further, such existing systems typically require the operator to specifically disengage the speed control means or to activate a separate deceleration means in order to regain operator control over the engine and in particular the throttle thereof. Such aspects which result from the driver or operator having the control of the engine removed from their authority hence introduces certain safety issues.
OBJECT OF THE INVENTION
Accordingly, it is an object of the present invention to provide an engine speed control method which at least ameliorates some of the above problems. In particular, it is an object of the present invention to provide an engine speed control method wherein total engine control authority is not necessarily removed from the engine operator.
SUMMARY OF THE INVENTION
With the above object in mind, the present invention provides in one aspect a method of controlling the engine speed of an internal combustion engine, the method including the steps of determining the engine speed demanded by an operator of the engine and comparing this demanded engine speed with a predetermined engine speed limit, wherein if the demanded engine speed exceeds the predetermined engine speed limit, the fuelling rate demanded by the operator is only reduced in order to control the engine speed to the predetermined engine speed limit.
Conveniently, if the demanded engine speed is less than the predetermined engine speed limit, then no change is made to the normal operation of the engine. Accordingly, engine speed limited operation only occurs where the demanded engine speed exceeds the predetermined engine speed limit.
Preferably, where the demanded engine speed exceeds the predetermined engine speed limit, an engine speed control means is adapted to only reduce the amount of fuel demanded by an operator of the engine. Hence, even though the operator may demand a greater fuelling rate than that necessary to achieve the predetermined engine speed limit, during such speed limited operation, the actual fuelling rate to the engine never exceeds that corresponding to the predetermined engine speed limit. In effect, the controller which governs the fuelling rate to the engine functions in a unidirectional manner during speed limited engine operation to only ever reduce the demanded fuelling level.
Conveniently, the method as described above is used to control the engine speed to the predetermined speed limit with the level of reduction of the demanded fuelling rate, or the fuel sought to be delivered to the engine, being based on the demanded engine speed. Preferably, the actual amount of fuel to be delivered to the engine can be determined by considering the difference between the demanded engine speed and the engine speed limit and reducing the demanded or normal fuelling level accordingly. The normal fuelling level is considered to be the amount of fuel that would normally be injected, having regard to various parameters such as engine speed and throttle position, if a speed limit or target engine speed was not set and equates

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