US2888876A

US2888876A - Fuel injection equipment

Info

Publication number: US2888876A
Application number: US709537A
Authority: US
Inventors: William M Nichols
Original assignee: Alco Products Inc
Current assignee: Alco Products Inc
Priority date: 1958-01-17
Filing date: 1958-01-17
Publication date: 1959-06-02
Anticipated expiration: 1976-06-02

Description

June 2, 1959 w. M. NICHOLS FUEL INJECTION EQUIPMENT 2 Sheets-Sheet 1 Filed Jan. 17, 1958 INVENTOR.

WILLIAM M. NICHOLS ATTORNEY June 2, 1959 w. M. NICHOLS 2,888,876

FUEL INJECTION EQUIPMENT F1 led Jan. '17, 1958 2 Sheets-Sheet 2 Fig.2

MAAAAMA AA WILLIAM M. NICHOLS NVENTOR.

ATTORNEY U i Swami 0.

FUEL INJECTION EQUIPMENT William M. Nichols, Schenectady, N.Y., assignor to Alco Products, Incorporated, New York, N .Y., a corporation of New York Application January 17, 1958, Serial No. 709,537

2 Claims. (Cl. 103-41) This invention relates to a fuel pumping system and particularly to such a system for supplying ,solid fuel to an internal combustion engine of the compressionignition type.

In a common type of such a system, fuel is delivered to the injector through tubing which is supplied by a pump having a plunger which overruns a supply port to entrap the fuel charge. A pressure wave is abrutly gen- 2,888,876 Patented June 2, 195 9 surge immediately after the spill port opens, as shownin the diagram of Fig. 3 of said patent.

The instant invention is an improvement over the deat a particular location in the structure to give improved results.

The principal object of the present invention therefore is to damp out the pressure waves in the fuel injection tubing of an internalcombustion engine of the class described to prevent secondary injection, nozzle drip, and fuel tubing erosion. Another object is to provide a plurality of devices between the pump chamber and the tubing connection of such an engine which will function to damp surging in the fuel column by changing the pressure energy to heat energy.

Still another object of the invention is to provide in the fuel pumping system of an internal combustion enerated in the fuel column when the supply port is sud denly closed and is transmitted along the column at a high speed. When this wave reaches the injector, it is reflected back through the column to the plunger where it is reflected forwardly again. This wave oscillation continues as long as the plunger is forcing the column toward the injector. Likewise, when the supply port is suddenly opened upon the spill action of the plunger, a negative wave is created which also travels along the fuel column at high speed until it reaches the injector.

There it is reflected back to the delivery valve, which is now closed, and upon encountering that element is reflected forwardly along the column. That is to say, the negative wave also oscillates in the fuel column between the injector and the delivery valve.

The presence of these waves in an uncontrolled state creates undesirable conditions in the system, such 'for example, as secondary injections and nozzle dribbling. It is furthermore believed that these waves cause cavitation erosion of the fuel tubing. Such erosion is characterized by the dislodging of metallic particles. from the tubing ture. Such drop would be eliminated if the waves could be sufficiently damped. Pressure-time diagrams show that the free oscillating waves reach their maximum am- When these voids later column be prevented from dropping at any time below the vaporization point of the fuel at operating temperaplitude shortly preceding the time when the delivery valve snaps shut. Consequently, if a construction of the pumping system is provided which will damp the waves shortly before the. delivery valve shuts, the cavitation will be minimized or eliminated.

In my Patent No. 2,729,169 I have disclosed a device which deals with the above discussed problem. It is directed towards damping the wave by means of a disc .check valve located between the delivery valve and the injector. In practice, the device of the patent has proved tobe quite successful in damping the pressure surges al- L gine of the class described novel apparatus, including a pair of discs, one disposed in the fuel column between the pump plunger and the delivery valve and the other between the delivery valve and the injector, said discs functioning as check valves in such a manner that the waves or surges created in the fuel column upon the spill action of the pump are substantially damped with the result that the pressure of the fuel in the column will not be permitted to drop below the vapor point of the fuel thus eliminating cavitaton erosion.

Other and further objects of the present invention will be apparent from the following description the accompanying drawings, and the appended claims.

In the drawings:

Fig. l is a cross section of the upper portion of a fuel pump with the plunger retracted so that the spill port is in open position.

Fig. 2 is a pressure-time diagram showing the curve of the wave generated when the spill port opens in a conventional pump; and

Fig. 3 is a similar diagram showing the curve of the wave generated in a pump to which the invention is applied. I

Reference is now made to Fig. 1 wherein delivery valve holder 1 is threaded into pump housing 2 to encase spring 3 which serves to bias delivery valve 4 into seated position. A hollow nut 5 is threaded to an extension 6 of holder 1 and has an opening in its top wall for the reception of tubing 7 which leads to a fuel injector, not shown. Tubing 7 has a shouldered conical head 8 adapted to seat in spacer 9, said conical head and spacer being clamped against the top face 10 of holder 6 by nut 5. Spacer 9 is formed with an axial duct 11, a bore 12, and -a counterbore 13, and holder 1 has a passageway 14 which establishes communication between spring chamber 15 in holder 1 and tubing 7. Disposed in counterbore 13 and normally resting upon top face 10 of holder .1 is a disc 16 preferably fluted whose outside diameter is less than that of counterbore 13 and whose vertical thickness is less than the depth of the counterbore. Free movement of the disc within the counterbore is thus permitted. Disc 16 has an axial duct 17 therethrough and its flutes define a plurality of passages 18 to permit the edge 24. Delivery valve 4 is fluted to provide lands 25 to guide the valve as it reciprocates in flanged housing member 26 in response to pumping action of the fuel. Member 26 rests on a circular spacer 27 having a central axial duct 28 therethrough. Spacer 27, in turn, abuts the sleeve 22. A solid copper packing 29 is clamped tightly between the chamfered downward extension 30 of holder 1 and the radial flange 31 of housing 26. Valve 4 has adjacent its upper end a cylindrical flange 32 which is connected to the main body of the valve by a neck 33. A conical shoulder 34 is formed upon a cylindrical projection 35 which extends downwardly from the main body of the valve to provide means for seating the valve on a conical valve seat 36 formed in housing member 26. Housing member 26 has a central cylindrical chamber 37 in which valve 4 reciprocates. Duct 38 is formed in housing member 26 adjacent seat 36 and communicates through a bore 39 and a counterbore 40, axial duct 28 in spacer 27 with pump cylinder 19. Disposed in counterbore 40 and having an outside diameter slightly smaller than the diameter of the counterbore is another fluted disc 41 formed with an axial duct 42 therethrough. The passages 43 formed by the disc flutes and the axial duct through the disc permit free flow of fuel therethrough in the same manner as fuel passes through disc 16, as previously described.

In operation, fuel enters cylinder 19 through radial ports 21 as supplied from the outside source. When plunger 23 rises and closes ports 21, a charge of fuel is trapped in cylinder 19 and the system therebeyond. As the plunger continues to rise, disc valve 41 is lifted by the fuel from its normal position on spacer 27 (as shown in Fig. 1) into engagement with shoulder 44. The fuel passes through the passages 43 formed by the disc flutes and through axial duct 42, bore 39, and duct 38 to lift the delivery valve 4 against the 'bias of spring 3 so that flange 32 clears chamber 37. The fuel continues through the valve and through spring chamber 15 and passage 14 to lift disc valve 16 upwardly against shoulder 12a. The fuel then passes through the passages 18 and duct 17 in disc 16 and through bore 12 and duct 11 into tubing 7 and thence to the injector not shown.

When fuel injection takes place at the injector, the

plunger 23 in systems of the class described is still rising and since thefuel is pumped in somewhat greater volume than it can escape through the injector, the pressure of the fuel column continues to rise until it is approximately 10,000-p.s.i. When such pressure is reached, the plunger helix 24 uncovers ports 21 and the fuel spills back through ports 21 into the supply system. At the timeof fuel spill, there is a large amount of pressure potential energy stored in the system beyond the plunger 23 due to the compressibility of the trapped fuel. Consequently, when the fuel spills, a negative pressure wave starts up through the column. When this negative wave reaches the lower face of disc 41, the disc is snapped down against spacer 27 because of the pressure differential across it. When the fuel in the fuel column above said disc reverses its flow as the negative wave progresses through the column toward the injector, such reversed flow of fuel impinges upon the top surface 45 of the disc from which it normally rebounds. However, axial duct 42 permits a portion of the impinging fuel to bleed through the disc thus reducing the amplitude of the rebounding wave.

The negative wave continues upwardly through the column and creates a pressure differential across the delivery valve 4 when it reaches the valve seat 36. Such differential assists in rapidly seating the valve. The wave continues past the valve and through spring chamber 15 and passageway 14. Upon reaching the lower face of disc 16, another pressure differential is created across the disc; and such differential assists in the rapid seating of the disc on top face 10 of extension 6. When the wave passes through axial duct 17 and passages 18 of the disc, it reverses the fuel flow therebeyond causing it to impinge on the top face 46 of the disc from which it would normallyrebonnd. But a portion of the fuel bleeds through 4 l axial duct 17 and the tendency of the reversing wave to rebound from surface 46 is damped and the wave amplitude correspondingly reduced. The fuel bleeding through duct 17 impinges on the retreating top surfaces 47 and 48 of valve 4 which is seated relatively slowly because the movement of fuel below. it is restricted by the throttling or dashpot effect of axial duct 42 in lower disc 41. Further fuel damping is thus effected and the wave amplitude is diminished.

In short, the amplitude of the fuel waves is diminished by the throttling action of each of the two disc valves 16 and 41 and the dashpot action of the delivery valve.- Heat is generated by such action; that is to say, pressure potential energy is dissipated as heat energy.

The concrete results of the operation of the invented device, as actually tested, are illustrated in the pressuretime diagram of Fig. 3. The diagram shown in Fig. 2 illustrates the pressure curve of the wave generated in a conventional pumping construction.

It is thus apparent that the device of the present invention, by restricting the return flow of fuel upon the spill action of the pump, eliminates the pressure waves which can cause cavitation erosion of the tubing and the pump cylinder and plunger and also eliminates inaccurate metering due to the rapid fuel spill into the pump chamber before the delivery valve closes.

While there has been hereinbefore described an approved embodiment of this invention, it will be understood that many and various changes and modifications in form, arrangement of parts and details of construction thereof may be made without departing from the spirit of the invention, and that all such changes and modifications as fall within the scope of the appended claims are contemplated as a part of this invention.

What I claim is:

. 1. In a fuel injection pump, a pump body having a bore, a plunger mounted for reciprocation in said bore, a fuel inlet passage communicating with said bore for supplying fuel thereto and a fuel delivery passage in said pump body and communicating with said bore for delivering fuel pumped by said plunger, a delivery valve in said fuel delivery passage, said delivery valve comprising a seat, a valve member and resilient means normally urging said valve member toward engagement with said seat whereby the passage of fuel past said delivery valve is prevented except when said delivery valve is moved away from said seat by pressure of fuel from said pumping chamber and flow control means in the delivery passage in said pump body between said pumping chamber and said delivery valve, said flow control means comprising a valve member for allowing substantially unrestricted flow from said pumping chamber through said fuel delivery passage to said delivery valve, while restricting the fuel flow from the delivery valve back into the pumping chamber to prevent erosion of said plunger by said returning fuel and I tending to eliminate the effects of said returning fuel upon the metering of the fuel in said pumping chamber.

2. In a fuel injection pump, a pump body having a bore, a plunger mounted for reciprocation in said bore, a fuel inlet passage communicating with said bore for supplying fuel thereto and a fuel delivery passage in saidpump body and communicating with said bore for delivering fuel pumped by said plunger, a delivery valve in said fuel delivery passage, said delivery valve comprising a seat, a valve member and resilient means normally urging said valve member toward engagement with said seat whereby the passage of fuel past said delivery valve is prevented except when said delivery valve is moved. away from said seat by pressure of fuel from said pumping chamber and flow control means in the delivery passage in said pump body between said pumping chamber and said delivery valve, said flow contr-o1 means comprising a valve member forallowing substantially unrestricted flow from said pumping chamber 5 through said fuel delivery passage to said delivery valve, while restricting the fuel flow from the delivery valve back into the pumping chamber to prevent erosion of said plunger by said returning fuel and tending to eliminate the elfects of said returning fuel upon the metering of the fuel in said pumping chamber, said flow control means comprising a valve member having a restricted opening to restrict the flow of fuel back into the pumping chamber and passage means adjacent the periphery of said valve member to allow substantially unrestricted flow of fuel from said pumping chamber to said delivery valve through said fuel delivery passage in said pump body.

No references cited