Injector drive circuit
AssigneeNippondenso Co., Ltd.
InventorMasahiro Ohba
Life of this patent
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Abstract
An injector drive circuit in which the injector is opened in response to a pulse signal with a time width which determines the quantity of the fuel to be supplied to the engine. To the injector, a circuit for supplying a peak current at the time of fuel injection and a field effect transistor for supplying a holding current after supply of the peak current are connected in parallel. In response to the control signal from a fuel injection amount control circuit, the peak current is supplied to the injector, and upon detection that a predetermined peak current has been supplied to the injector, the peak current is stopped. Thereafter, by controlling the gate of the field effect transistor, the holding current is supplied to the injector through the field effect transistor, until the control signal is stopped.
Claims6
An injector drive circuit for an injector opened in response to an electrical pulse signal with a time width corresponding to the amount of fuel to be supplied to the engine comprising:
- a field effect transistor having a drain-source path connected in series with said injector for supplying current to said injector;
- and
- a switching circuit for determining whether a first predetermined current is supplied to said injector after the rise of said electrical pulse, and for controlling current supplied to said injector at a second current value by holding the gate potential of said field effect transistor at a predetermined set potential level for a time period during which said electrical pulse signal is produced after said first predetermined current is supplied to said injector, said switching circuit including:
- a first D-type flip-flop having a preset terminal, a data terminal, a clock terminal and an inverted output terminal,
- means for presetting said first flip-flop when said first predetermined current is supplied to said injector,
- means for setting said first flip-flop to a state defined by the voltage on said first flip-flop data terminal in response to the rise of said electrical pulse signal,
- a second D-type flip-flop having a preset terminal, a data terminal and an output terminal,
- means for presetting said second flip-flop when said first predetermined current is applied to said injector,
- means for setting said second flip-flop to a state defined by said second flip-flop dated terminal in response to the fall of said electrical pulse signal,
- a first gate having two inputs responsive to said electrical pulse signal and a signal at said first flip-flop inverted output, respectively, said first gate being activated when said electrical signal is applied while said first flip-flop is set,
- a power transistor for supplying current to said injector, said power transistor becoming conductive when said first gate is activated,
- a second gate having two inputs responsive to said electrical pulse signal and a signal at said second flip-flop output terminal, respectively, said second gate being activated when said second flip-flop is preset while said electrical pulse signal is being applied, and
- means for rendering conductive said field effect transistor when said second gate is activated.
An injector drive circuit for an injector opened in response to an electrical pulse signal with a time width corresponding to the amount of the fuel to be supplied to the engine comprising:
- a field effect transistor having a drain-source path connected in series with said injector for supplying current to said injector;
- and
- a switching circuit for determining whether a first predetermined current is supplied to said injector after the rise of said electrical pulse signal, and for fixing current through said field effect transistor to a fixed second predetermined level by holding the gate potential of said field effect transistor at a predetermined set potential level corresponding to said second predetermined level for a time period during which said electrical pulse signal is produced after said first predetermined current is supplied to said injector.
In an injector drive circuit for a fuel injection system comprising a control circuit for calculating the amount of the fuel supplied to the engine as a time width of an electrical pulse signal and an injector opened in accordance with the time width of said electrical pulse signal of said control circuit for supplying by injection the fuel to said engine;
- the improvement further comprising a power transistor in series with said injector for supplying a large current at the time of opening of said injector, a field effect transistor connected in series with said injector and in parallel to said power transistor for supplying a comparatively small current for holding the open state of said injector after the opening of said injector, and a switching circuit for turning on said power transistor only during the time period from the supply of said electrical pulse signal from said control circuit to the supply of a peak current of a predetermined value to said injector, said switching circuit holding the gate potential of said field effect transistor at a predetermined set potential only during that part of said time width of said electrical pulse signal when said power transistor is not conductive, thus turning on said field effect transistor.
Dependencies are inferred from the claim text.