US 4,869,219 AGranted

Dual spring air fuel control for the PT fuel system

AssigneeCummins Engine Company, Inc.

InventorsRobin J. Bremmer, Roscoe A. Baker

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Abstract

A tamper-proof dual spring controlled air fuel control for a compression ignition type internal combustion engine is provided wherein fuel is supplied to the engine cylinders in response to the pressure of the air in the intake manifold. A pair of oppositely biased springs controls the movement of a stem valve in response to intake manifold air pressure exerted on a flexible diaphragm located between the oppositely biased springs. The stem valve includes a plunger within a barrel in the air fuel control housing in the engine fuel pump. The cross-sectional profiles of the plunger and barrel are designed to meter precisely a controlled amount of fuel to the engine fuel supply system as the intake air pressure increases and to reduce this metered flow as the intake air pressure decreases. Two plunger and barrel assembly embodiments having different profiles are provided. A class fit between the barrel and plunger of the present air fuel control wherein the clearance must not exceed 0.000075 to 0.000125 inches and pressure regulating means located in the plunger substantially eliminate fuel leakage from the barrel. Internal venting means are provided to direct any minimal amount of fuel which might leak to the engine crankcase.

Claims25

Dependent claims

A fuel supply system for an internal combustion engine which is operationally controlled by the pressure of fuel supplied to the engine from a fuel source and which has an intake manifold for supplying air to the engine, comprising

(a) air pressure responsive means for modulating mechanically the flow of fuel into the engine in response to the pressure of air within the intake manifold, said air pressure responsive means including:
(1) first and second chambers, wherein said first chamber includes means for fluid connection with the engine air supply and said second chamber is sealed from fluid connection with said fuel supply system, and
(2) pressure responsive actuating means dividing said first and second chambers for transforming changes in intake manifold pressure into mechanical movement for operating said air pressure responsive means, said pressure responsive actuating means comprising a diaphragm,
(b) fuel metering means including, a valve stem that is directly connected to said diaphragm so as to be movable in response to air pressure changes within said first chamber, said fuel metering means for controlling the flow of fuel from said fuel supply system directly in response to changes in intake manifold pressure between a substantially blocked position and a fully open position, and
(c) a pair of oppositely biased spring means located on opposite sides of said diaphragm, wherein a first spring means is located in said first chamber and is biased to move said diaphragm and said fuel metering means by way of said valve stem in a first direction and a second spring means is located in said second chamber and is biased to move said diaphragm and said fuel metering means by way of said valve stem in a second direction opposite to said first direction,
said first and second spring means maintain said fuel metering means in said substantially blocked position when said intake manifold pressure in said first chamber is zero, said first spring means moves said fuel metering means in said first direction toward said fully open position as the pressure in said first chamber is increased, and said second spring means moves said fuel metering means in said second direction back toward said substantially blocked position when pressure is decreased in said first chamber to zero,
whereby said pair of oppositely biased spring means cause quick and precise movement of said fuel metering means with intake pressure changes in said first chamber to align said fuel metering means in a position which permits the flow of fuel at a rate that is directly related to the intake manifold pressure, thereby substantially eliminating any delay in increasing fuel supply to the engine.

4 more elements

A plunger and barrel assembly for a fuel supply system for an internal combustion engine which is operationally controlled by the pressure of fuel supplied to the engine from a fuel source and which has an intake manifold for supplying air to the engine, air pressure responsive means for modulating mechanically the flow of fuel into the engine in response to the pressure of air within the intake manifold, and housing means for receiving said fuel supply system, said plunger and barrel assembly including longitudinal barrel means adapted to be engaged by said housing means to provide a fluid connection between said fuel source and said engine, and plunger means connected directly to said pressure responsive means slidably class fitted within a central bore in said barrel means to be coaxial therewith for selectively opening and closing said fluid connection manifold, wherein said plunger means includes pressure regulating means for providing a pressure connection between said central bore in said barrel means, at a point between said fluid connection and said connection of said plunger means to said pressure responsive means, and said housing, thereby substantially eliminating fuel leakage from said assembly.

An air fuel control for an internal combustion engine which is operationally controlled by the pressure of fuel supplied to the engine from a fuel source, which has an intake manifold for supplying air to the engine and which includes pressure responsive means connected to the intake manifold for modulating mechanically the flow of fuel into the engine on response to the pressure of the air within the intake manifold, said air pressure responsive means comprising

(a) a first chamber fluidically connected to said intake manifold and a second chamber separated from said first chamber by a flexible bellows member secured to a piston;
(b) a pair of oppositely biased spring means located on opposite sides of said piston for transforming changes in intake manifold pressure into mechanical movement, wherein one of said spring means is located in said first chamber and is biased to move said piston in a first direction and the other of said spring means is located in said second chamber and is biased to move said piston on a second direction opposite to said first chamber direction;
and
(c) fuel metering means having a valve stem attached directly to said piston for movement with said piston between a first, fuel flow position and a second, fuel blocked position, wherein as the pressure of intake air in said first chamber against said bellows member increases, said one spring means biases said piston in said first direction to move said fuel metering means to said first position, thereby allowing fuel to flow through said air fuel control as the pressure of intake air in said first chamber against said bellows member decreases, said direction to move said fuel metering means to said second position, thereby substantially blocking fuel from flowing through said air fuel control, wherein said one spring means includes an adjustable spring retaining means within said first chamber for controlling the extent of the longitudinal compression and expansion of said one spring means within said first chamber in response to increasing air pressure, thereby controlling the amount of air pressure required to bias said piston in said first direction.

1 more element

Dependencies are inferred from the claim text.

Facts

Application: 07/220,939Filed 23 Jun 1988 · continuation
Priority: 14 Jul 1986
Granted: 26 Sep 1989
Term ends: Not estimatedThe source records don’t support an estimate.

Classification5 codes

F02D 7/007
Throttling of fuel passages between pumps and injectors or overflow passages: by fluid actuated means, e.g. slide valves
F02D 1/065
By means dependent on pressure of engine working fluid: of intake of air
F02M 59/205
Varying fuel delivery in quantity or timing: quantity of fuel admitted to pumping elements being metered by an auxiliary metering device
F02D
Controlling combustion engines