Internal-combustion engines – Charge forming device – With fuel pump
Reexamination Certificate
2000-12-01
2001-08-28
Miller, Carl S. (Department: 3747)
Internal-combustion engines
Charge forming device
With fuel pump
C123S514000
Reexamination Certificate
active
06279541
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a fuel supply system for an internal combustion engine of an automobile and, more particularly, to a fuel supply system responsive to engine fuel demand.
BACKGROUND OF THE INVENTION
In the fuel supply system for a fuel injected internal combustion engine present in many modem automotive vehicles, a fuel pump driven by an electric motor continuously supplies liquid fuel to the fuel injector(s) of the engine at a substantially constant flow rate which is always more than sufficient to supply the maximum possible fuel demand of the engine. Thus, under most engine operating conditions and particularly when the engine is merely idling, the fuel pump produces a significant amount of excess fuel that must be returned to the fuel tank from which the fuel pump originally drew the fuel.
Some fuel systems supply the entire fuel output of the pump to the engine and return the excess fuel from the engine to the fuel tank. Other fuel systems divert or bypass the excess fuel before it is delivered to the engine. Such a fuel system is commonly referred to as a “no return” or “returnless” type of system because it neither requires nor has a fuel return line extending from the fuel rail of the engine itself and back to the fuel tank. One prior returnless fuel system is disclosed in U.S. Pat. No. 5,975,061 issued on Nov. 2, 1999 to Briggs et al. In this system, the fuel pump continuously operates at maximum fuel output capacity, and the excess fuel is diverted from the engine and returned to the tank by a bypass fuel pressure regulator which maintains a substantially constant pressure of fuel supplied to the engine even though the fuel flow rate varies.
Another returnless fuel system is disclosed in U.S. Pat. No. 5,265,644 in which changes in the instantaneous pressure of the fuel supplied to the engine actuate a switch to change the speed of the electric motor to vary the fuel output of the pump through appropriate pulse width modulation circuitry which changes the electric power applied to the pump motor.
While these systems do attempt to deliver an amount of fuel to the engine which better matches the actual fuel demand of the engine, they are often inaccurate and untimely, especially when there is a sudden and significant rise or fall in the fuel demand of the engine, and sometimes momentarily result in insufficient fuel being supplied to the engine. Thus, there is a present need in the art for an apparatus which better and more rapidly and timely matches the actual fuel demand of the engine.
SUMMARY OF THE INVENTION
A fuel supply system with a bypass fuel pressure regulator, a fluid-activatable switch responsive to bypass fuel flow, and an associated electric control circuit to vary and modulate the speed of an electric motor driving a fuel pump and hence its output fuel flow rate in accordance with the fuel demand of an internal combustion engine. Preferably, the fluid-activatable switch is manipulable into one of either an electrically open state or an electrically closed state, as determined by the flow rate of excess fuel from the bypass fuel pressure regulator. Preferably, the control circuit is capable of adjusting the level of the voltage supplied to the electric fuel pump motor as dictated by the position of the fluid-activatable switch. In this way, the speed of the electric motor and fuel pump output is modulated in accordance with changes in both the flow of the fuel and the state of the switch.
In a preferred embodiment of the present invention, the fluid-activatable switch has a plunger movable relative to an electrical contact to change the state of the switch in response to the flow rate of excess fuel. The plunger is slidably received in an elongate chamber in a body having an inlet opening at one end, a stop opening at the opposite end, and at least one outlet opening, all communicating with the elongate chamber. Preferably, the plunger is yieldably biased by a resilient biasing element with an adjustable stop member. The stop member is received within the stop opening and has an exposed head portion and a tail portion extending into the chamber. Preferably, the biasing element is a spring with one end abutting the stop member and the other end extending into the chamber and bearing on the plunger. Preferably, the plunger has a shoulder portion, opposite the biased end and proximate each outlet opening in the body, and a single electrically conductive contact mounted on the shoulder portion proximate the inlet opening. The switch also preferably includes a pair of electrically conductive contacts electrically connected to the electric control circuit and mounted and exposed within the chamber of the body, substantially between the inlet opening and each outlet opening. In such a configuration, the chamber of the body defines a fuel flow path from the inlet opening to each outlet opening. The single contact and the shoulder portion of the plunger are situated within the fuel flow path and yieldably biased against any fuel flowing within the fuel flow path. In this way, the plunger is capable of being moved as dictated by the excess fuel flowing within the fuel flow path such that the switch is in one of either the electrically open state or the electrically closed state or position.
Preferably, the electric voltage control circuit includes means for both electrically sensing the state of the fluid-activatable switch and selectively connecting a resistive circuit element such as a resistor in electrical series with the electric fuel pump motor to an electric power source as dictated by the sensed state of the switch. Most preferably, the position sensing and selective connecting means includes a transistor such as, for example, a field-effect transistor.
Objects, features, and advantages of this invention include an electric motor fuel pump system which provides improved efficiency, improved responsiveness to varying engine fuel demand, always satisfies the engine fuel demand, and is compact, rugged, durable, of relatively simple design and economical manufacture and assembly, and in service has a long usefull life.
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patent: 5265644 (1993-11-01), Tuckey
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patent: 5701869 (1997-12-01), Richardson et al.
patent: 5718207 (1998-02-01), Ito
patent: 5765535 (1998-06-01), Radermacher
patent: 5775304 (1998-07-01), Kono et al.
patent: 5785025 (1998-07-01), Yoshiume et al.
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patent: 6067963 (2000-05-01), Oi et al.
Doane Kirk D.
Gettel Bryan J.
Kuenzli Ronald B.
Kuperus Peter P.
Maschke Edwyn R.
Miller Carl S.
Reising, Ethington, Barnes, Kisselle, Learman & McCulloch,P.C.
Walbro Corporation
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