Miscellaneous active electrical nonlinear devices – circuits – and – Signal converting – shaping – or generating – Current driver
Reexamination Certificate
2000-03-15
2001-09-18
Wells, Kenneth B. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Signal converting, shaping, or generating
Current driver
C123S478000
Reexamination Certificate
active
06292036
ABSTRACT:
TECHNICAL FIELD
The invention relates to a drive circuit for a device having two electromagnetically operable actuators. In particular, the invention relates to a drive circuit for a dual-valve fuel injector, forming part of the fuel system of a vehicle internal combustion engine, the fuel injector having two electromagnetically operable actuators, one for each of the two valves.
BACKGROUND OF THE INVENTION
In conventional fuel injectors there is a single actuator for a spill control valve controlled by means of a drive circuit. A drive circuit for controlling a four cylinder internal combustion engine having four fuel injectors is described in PCT application WO96/27198. The actuator for each fuel injector valve has a winding through which a current is passed to actuate the valve. A first controllable switch (commonly referred to as the high side switch) is connected in series between one end of the winding forming part of each actuator and a first terminal of the drive circuit connected to the positive terminal of a DC supply. The high side switch is therefore connected to one end of each of the four actuators. Additionally, a diode is connected in the path between the DC supply and the high side switch.
The other end of each winding is connected in series to a second controllable switch (commonly referred to the low side switch), which in turn is connected to the negative terminal of the DC supply via a resistor. The current flowing through each winding can be determined by means of this resistor. In addition, the anode connection of a second diode, one associated with each winding, is in connection with the end of the winding connected to the respective low side switch. The cathode connection of each second diode is in connection with the negative terminal of the DC supply via a capacitor. Thus, depending on whether the low side switch of the associated winding is switched on or off, the winding of each valve connects to the negative terminal of the battery either via a capacitor or by means of the resistor.
When it is required to actuate one of the valves, the current in the associated winding is allowed to rise to a high value and is then allowed to fall to a lower value after which it is maintained for a period at a mean level by subjecting the high side switch to a modulated pulse, thereby serving to regulate the current flow through the windings, until such time as the current is turned off to de-actuate the valve.
In more recently developed internal combustion engines, dual-valve fuel injectors are to be employed, each fuel injector having a spill valve and a nozzle control valve requiring independent control by an associated actuator. Thus, there is a requirement for a drive circuit for controlling an assembly of fuel injectors each having two actuators. For this purpose it would be possible to employ the drive circuit for a conventional single-actuator fuel injector assembly, as hereinbefore described. However, in order to do so, a duplicate of each circuit component is required for the additional actuator in each fuel injector. This requires a drive circuit of considerable complexity. In particular, four wire connections are needed to each fuel injector from the DC supply, two for each winding of each actuator. This is particularly difficult to accommodate within a single fuel injector body.
It is an object of the present invention to provide a drive circuit for a dual-actuator fuel injector having reduced complexity.
SUMMARY OF THE INVENTION
According to the present invention there is provided a drive circuit for controlling at least one device having first and second electromagnetically operable actuators, the drive circuit having first and second terminals for connection to voltage supply means and comprising a first controllable switch in connection with one side of the actuators and the first terminal, each actuator having an associated second controllable switch in connection with the other side of the respective actuator, whereby opening and closing of the first and second switches serves to control selection and actuation of the actuators, the drive circuit further comprising sensing means for providing independent sensing of the current flowing through each of the actuators, each actuator having an associated diode in connection with the respective second controllable switch to ensure current flows through the sensing means when the first controllable switch is opened and the second controllable switch is closed.
The drive circuit provides the advantage that dual-actuator device can be powered with a more simplified circuit than is possible using a conventional means. In particular, the drive circuit limits the numbers of connection required to the actuators. This is particularly important when the drive circuit is used to implement control of valve actuators in a dual-valve fuel injector system.
Furthermore, the drive circuit enables independent sensing of the current in each actuator. Therefore current glitch detection may be performed independently for each actuator during the period in which current flows through the sensing means. Current glitch detection is important in fuel injector control as it provides a means of determining when valve closure occurs.
The sensing means may be provided by two resistors, one resistor being associated with a different one of the two actuators, each resistor being connected on one side to the second controllable switch associated with the respective actuator.
The drive circuit may be controlled by an electronic control unit, providing switching pulses to the first and second controllable switches. The switching control pulses include current glitch detection pulses to initiate switching of the first and second controllable switches when current sensing is required.
The drive circuit may further comprise a blocking diode connected between each actuator and the respective second controllable switch to prevent any unintentional short-circuit current flow through the respective actuator. Preferably, the blocking diodes are located within the electronic control unit (ECU).
In a preferred embodiment of the invention, the drive circuit controls a plurality of devices arranged in two banks, the drive circuit comprising separate first controllable switches for each of the two banks, the second controllable switches being arranged such that each second controllable switch is common to actuators of devices in both banks.
The drive circuit may be powered by a DC supply voltage connected to the first and second terminals.
Alternatively, the drive circuit may further comprise a third controllable switch to enable mixed-voltage operation, whereby selection of a higher voltage supply provides an initial higher current to an actuator to initiate actuation thereof and selection of a lower voltage supply provides a subsequent lower current to the actuator sufficient to hold the actuator in a desired position within the device, selection being effected by switching of the third controllable switch.
REFERENCES:
patent: 4961006 (1990-10-01), Pace et al.
patent: 5264736 (1993-11-01), Jacobson
patent: 5729164 (1998-03-01), Pattantyus
patent: 5760619 (1998-06-01), Yamaguchi
Delphi Technologies Inc.
Dinh Paul
VanOphen John A.
Wells Kenneth B.
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