Internal-combustion engines – Charge forming device – Fuel injection system
Patent
1998-02-17
1998-09-08
Moulis, Thomas N.
Internal-combustion engines
Charge forming device
Fuel injection system
123506, 123299, 361154, F02D 4120
Patent
active
058030492
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a control system for an electromagnetically operable valve more particularly a fuel delivery control valve of a fuel injection system for a compression ignition engine.
One example of a fuel injection system incorporating the control valve comprises a cam actuated high pressure fuel pump having an outlet connected to the inlet of an injection nozzle which incorporates a fuel pressure actuated valve member. The control valve is connected between the outlet and a drain so that when the valve is closed the fuel delivered by the pump will be supplied to the injection nozzle and delivered to the associated engine. The control valve includes a valve member which is spring biased to the open position and the associated actuator is energised to move the valve member to the closed position against the action of the spring.
In order to minimise engine noise the usual practice is to deliver a small quantity of fuel at a reduced rate in advance of the main quantity of fuel, to the injection nozzle. The small quantity or pilot quantity, is achieved by closing the control valve and then re-opening the valve before re-closing the valve to obtain the main delivery of fuel.
In the examples described when the control valve is opened the pressure in the fuel column between the control valve and the nozzle falls towards the drain pressure. As a result when the control valve is re-energised to obtain the main delivery of fuel re-pressurisation of the column of fuel has to take place before the valve member of the nozzle can start to move to the open position. The effective separation between the end of delivery of the pilot quantity and the commencement of delivery of the main quantity of fuel therefore includes the period required to re-pressurise the fuel column.
As with all electromagnetically operable devices the valve member takes some time to move forward to its final position against the action of its spring when electric current is supplied to the actuator and in addition, it takes some time to return to its original position under the action of the spring, when the supply of current to the actuator is discontinued. There is therefore a minimum period between the end of the delivery of the pilot quantity of fuel and the commencement of delivery of the main quantity of fuel if the forward and return movements of the valve member are not to overlap, the period for re-pressurising the fuel column forming part of the aforesaid minimum period.
According to one aspect of the invention it is proposed by supplying current to the actuator from a source of supply, to control the movement of the valve member under the action of its spring following the delivery of the pilot quantity of fuel thereby to control the depressurisation of the fuel column prior to re-establishing the current flow from the source of supply to achieve delivery of the main quantity of fuel.
The minimum period required for a cycle of operation of the control valve also means that there is a minimum pilot quantity of fuel which can be supplied to the engine. It has been the practice to control the profile of the current pulse which is applied to the actuator to effect movement of the valve member against the action of the spring, to minimise so far as is possible, any bounce when the valve member reaches its final position. Moreover, the profile of the current pulse has been such as to provide an opportunity to detect when the valve member reaches its final position.
According to another aspect of the invention the initial current flow in the actuator for the purpose of achieving movement of the valve member against the action of the spring is sufficiently high as to cause bounce of the valve member and the decay of current flow following the initial current flow is controlled to control the de-pressurisation of the fuel column intermediate the control valve and the nozzle.
In the accompanying drawings:
FIG. 1 is a diagrammatic drawing of a typical fuel injection system,
FIG. 2 is a circuit diagram of a control circuit for a valve f
REFERENCES:
patent: 4225898 (1980-09-01), Weber et al.
patent: 4234903 (1980-11-01), Harper
patent: 4491113 (1985-01-01), Gassler et al.
patent: 4509487 (1985-04-01), Mowbray
patent: 5381297 (1995-01-01), Weber
patent: 5668476 (1997-09-01), Archer
patent: 5706778 (1998-01-01), Kapus
Lucas Industries
Moulis Thomas N.
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