US3788615A

US3788615A - Accelerator pump system

Info

Publication number: US3788615A
Application number: US00231298A
Authority: US
Inventors: G Bishop
Original assignee: Ford Motor Co
Current assignee: Ford Motor Co
Priority date: 1972-03-02
Filing date: 1972-03-02
Publication date: 1974-01-29
Anticipated expiration: 1991-01-29
Also published as: CA965661A

Abstract

A fuel valve that is urged toward its seat by gravity is located in the discharge passage of a carburetor accelerator pump and separates the discharge passage from an outlet passage communicating directly with the carburetor induction passage. An air vent is provided for the outlet passage and a check valve located in the air vent also is urged toward its seat by gravity. During accelerator pump operation, the air vent check valve remains on its seat and fuel flows into the carburetor induction passage. If a low pressure develops in the outlet passage, the pressure differential lifts the air vent check valve from its seat before the fuel valve is lifted from its seat and thereby prevents spurious fuel flow through the accelerator pump system.

Description

im States i! atent 1 1 Bishop Jan. 29, 1974 Ford Motor Company, Dearbom, Mich.

Filed: Mar. 2, 1972 Appl. No.: 231,298

Inventor:

Assignee:

Primary ExaminerTim R. Miles [57] ABSCT A fuel valve that is urged toward its seat by gravity is located in the discharge passage of a carburetor accelerator pump and separates the discharge passage from an outlet passage communicating directly with the car- 52 US. Cl 261/34 A buretor induction P g An air vent is Provided for [51] Int. Cl. F02m 7/08 the Outlet p g d a check valve ed in th air 58 Field of Search 261/34 A vent also is urged toward its seat y y- During accelerator pump operation, the air vent check valve [56] References Cit d remains on its seat and fuel flows into the carburetor UNITED STATES PATENTS induction passage. If a low pressure develops in the outlet passage, the pressure differential lifts the air 2 vent check valve from its seat before the fuel valve is 2:920:877 1/1960 Spragle 67 lifted from its seat and thereby prevents spurious fuel 1,923,429 8/1933 Ericson 261 34 A flow through the accelerator P p y 2,267,57O 12/1941 Markham... 261/34 A 3,460,813 8/1969 Hieger 261/34 A 3 Clam, 1 D'awmg Flgure 34 if 32 K 22 Z 1 I as r28 4 36 24 &

Tfi 190 Z \/f z 4 ACCELERATOR 1P SYSTEM SUMMARY OF THE INVENTION During certain periods of reciprocating engine operation, a pressure differential is transmitted through the induction passage of the carburetor and into the discharge passage of the carburetor accelerator pump system. The pressure differential draws fuel through the accelerator pump system and into the engine. For many years this situation was ignored since the amount of fuel was small and it had minimal effect on engine performance and fuel economy. Investigations into engine exhaust emissions revealed, however, that such fuel pullover seriously affects the quantitity of various compounds in the engine exhaust gases. An attempt at solving the pullover proposed locating a spring loaded fuel valve in the accelerator pump discharge passage, but subsequent analysis showed that the force produced by the spring necessary to prevent pullover also produced an undesirable delay in accelerator pump operation.

This invention provides an accelerator pump system that positively prevents both fuel pullover through the induction system and direct fuel loss to the atmosphere. The pump system has a fuel check valve located where the discharge passage of the accelerator pump opens into an outlet passage that communicates directly with the carburetor induction passage. An air vent mechanism communicates with the outlet passage and includes a check valve permitting air flow into the outlet passage but preventing any flow out of the outlet passage. When the system is at rest the air vent check valve is urged toward its seat by a force that is considerably less than the force urging the fuel check valve toward its seat.

. During accelerator pump operation, fuel pressure produced by the accelerator pump moves the fuel check valve from its seat and forces fuel into the outlet passage. Any resulting pressure increase in the outlet passage increases the seating force on the air vent check valve to prevent positively any fuel leakage through the air vent. Fuel reaching the outlet passage flows into the carburetor induction passage from which it is drawn into the engine. If engine operation produces a low pressure in the outlet passage, the air vent check valve opens to bleed off the low pressure. Both the fuel check valve and the air vent check valve conveniently are urged toward the respective valve seat by gravity. The fuel check valve is designed with greater mass or smaller pressure area than the air vent check valve to insure that the air vent check valve opens when low pressure exists in the outlet passage.

BRIEF DESCRIPTION OF THE DRAWING The drawing is a achematic illulstration of an accelerator pump system of the invention. Both the air vent check valve and the fuel valve of the illustration are urged by gravity to the closed position.

DETAILED DESCRIPTION Referring to the drawing, a fuel source 10, which can be the fuel bowl of a conventional carburetor, has an opening 12 in its floor through which fuel flows to the inlet of an accelerator pump indicated generally by numeral 14. A ball type valve 16 serves as the inlet to accelerator pump 14. The accelerator pump piston 18 is mounted slidably in a chamber and is connected to the throttle linkage (not shown) for appropriate reciprocating motion.

A discharge passage 20 connects the pump chamber defined in part by ball valve 16 and piston 18 with an outlet passage 22. Passage 20 is substantially vertical at its opening into outlet passage 22 and a fuel valve 24 is located in the opening so that gravity urges the fuel valve onto a seat 26. When the fuel valve 24 is on its seat 26, the valve prevents any fuel flow from passage 20 into passage 22.

Passage 22 communicates directly through a discharge nozzle 28 with an induction passage 30 of the carburetor. Induction passage 30 is a portion of the induction system of the engine (not shown). Passage 22 also communicates through a vent mechanism 32 with the atmosphere or a velocity pressure area of induction passage 30. Vent mechanism 32 comprises a ball type check valve 34 that is urged onto a seat 36 by gravity. Check valve 34 has substantially less mass than fuel valve 24.

When accelerating fuel is required by the engine, piston 18 moves downward to force a fuel charge against the lower surface fo fuel valve 23. The fuel charge lifts valve 24 from its seat, which permits the fuel to flow past the valve and into outlet passage 22. A slight pressure increase occurs in passage-22 and the pressure increase assists in holding ball valve 34 on its seat. The fuel reaching passage 22 thus flows through nozzle 28 and into induction passage 30.

Low pressure produced during some engine operating modes at nozzle 28 can be transmitted into outlet passage 22 where the low pressure tends to lift fuel valve 24 from its seat and draw fuel from passage 20. Under these circumstances, ball valve 34 is lifted from its seat prior to any significant movement of fuel valve 24. Air thus is drawn through the vent mechanism into passage 22 to dissipate the low pressure,

Passage 22 preferably slopes upward between fuel valve 24 and air vent check valve 34 to inhibit any tendency for fuel to collect around the air vent check valve. Small amounts of fuel might collect around the air vent check valve under certain conditions but the fuel usually is drawn back into passage 22 without escaping into the atmosphere. If necessary, the vent mechanism can communicate with passage 22 through the roof of passage 22.

Fuel valve 24 and air vent check valve 34 can be spring loaded toward the respective valve seats if desired. In this arrangement, the spring for air vent check valve 34 produces a lower force than the spring for the fuel valve to insure that the air valve opens when low pressure exists in outlet passage 22. Nozzle 28 preferably is as close as possible to fuel valve 24 to reduce the time required for fuel to reach induction passage 30.

Thus this invention provides an accelerating pump system for preventing fuel pullover into the induction system and preventing fuel leakage into the atmosphere. Since the relative opening resistance of the air vent check valve and the fuel valve determines proper system operation, the actual opening resistance of the fuel valve can be low to reduce fuel flow delay.

I claim:

ll. In a fuel supply system for an engine including a fuel source and an induction passage, an accelerator pump system comprising,

pump means obtaining fuel from said fuel source,

passage means connected to said pump means for transmitting fuel from said pump means to said induction passage,

a fuel valve urged toward its seat by gravity and located in said passage means for controlling fuel 5 flow from said pump means to said induction passage, said fuel valve opening when said pump means is actuated, and

vent means for venting the portion of said passage means downstream of said fuel valve, said vent means including a check valve movable independently of the fuel valve permitting air flow into the passage means through the vent means but preventing fuel flow out of the passage means through the vent means, said check valve being urged toward its seat by gravity to close the vent and having a mass less than the mass of the fuel valve so as to be lifted off its seat to an open poisition prior to said fuel valve when a predetermined subatmospheric pressure exists in the portion of the passage means downstream of the fuel valve.

2. The fuel supply system of claim 1 in which the passage means comprises an outlet passage communicating directly with said induction passage and a pump discharge passage connecting said pump means with said outlet passage, said fuel valve being located at the junction of said pump discharge passage with the outlet passage, and said air vent check valve communicating with said outlet passage.

3. The fuel supply system of claim 1 in which the passage means comprises an outlet passage communicating directly with said induction passage and a pump discharge passage connecting said pump means with said outlet passage, said fuel valve being located at the junction of said pump discharge passage with the outlet passage, and said vent means communicating with said outlet passage.

Claims

1. In a fuel supply system for an engine including a fuel source and an induction passage, an accelerator pump system comprising, pump means obtaining fuel from said fuel source, passage means connected to said pump means for transmitting fuel from said pump means to said induction passage, a fuel valve urged toward its seat by gravity and located in Said passage means for controlling fuel flow from said pump means to said induction passage, said fuel valve opening when said pump means is actuated, and vent means for venting the portion of said passage means downstream of said fuel valve, said vent means including a check valve movable independently of the fuel valve permitting air flow into the passage means through the vent means but preventing fuel flow out of the passage means through the vent means, said check valve being urged toward its seat by gravity to close the vent and having a mass less than the mass of the fuel valve so as to be lifted off its seat to an open poisition prior to said fuel valve when a predetermined subatmospheric pressure exists in the portion of the passage means downstream of the fuel valve.