US3394688A

US3394688A - Fuel pump timing means

Info

Publication number: US3394688A
Application number: US513155A
Authority: US
Inventors: Vernon D Roosa
Original assignee: HARTFORD MACHINE SCREW CO
Current assignee: HARTFORD MACHINE SCREW CO
Priority date: 1965-11-01
Filing date: 1965-12-09
Publication date: 1968-07-30
Anticipated expiration: 1985-07-30
Also published as: DE1776253A1; SE322373B; DE1523226A1; SE331926B; ES332967A1; DE1776253C3; GB1165941A; DE1526542A1; DE1526542B2; FR1508175A; DE1526542C3; DE1523226B2; DE1776253B2; GB1120083A

Description

July 30, 1968 v. D. RoosA 3,394,688

v FUEL PUMP TIMING MEANS gia- FW. I //////////.7////////////////// 'ffx NI f IN INVENTOR. VERNON D. ROOSA www? ATTORNEYS July 30,1968 v. D. ROOSA '3,394,688

` FUEL PUMP TIMING MEANS 3 Sheets-Sheet 2 Filed Dec. 9. 1965 @Nm N...

l NVENTOR.

VERNON D. RoosA SYM ATTORNEYS v. D. RoosA 3,394,688

FUEL PUMP TIMING MEANS 3 Sheets-Sheet 5 July 30, 1968 Filed Dec. 9, 1965 w /za INVENTOR. VERNON D. ROOSA BY lafaa// ATTORNEYS @1MM l Il W United States Patent O f 3,394,688 FUEL PUMP TIMING MEANS Vernon D. Roosa, West Hartford, Conn. Hartford Maihine Screw Co., P.0. Box 1440, Hartford, Conn. 061 1) Filed Dec. 9, 1965, Ser. No. 513,155 7 Claims. (Cl. 123-139) ABSTRACT F THE DISCLOSURE A fuel injection pump wherein an angular shiftable cam ring for actuating the radially movable pistons of the pump is longitudinally split and radially expandable during the pumping stroke to transmit the radial force of pumping to the housing which provides the radial support for the reaction force imposed on the cam. The complementary bearing surface of the housing in which the cam ring is positioned is roughened and the connector arm between the cam ring and the timing piston engages one of the ends of the split cam ring to fix the adjusted angular position of the cam ring to control the timing of fuel injection. With this design the frictional force between the cam ring and the mating bearing surface of the housing is increased with an increase in the force imposed on the cam during the pumping stroke. The timing piston houses a pilot valve responsive to both fuel pressure proportional -to engine speed and an opposing fuel pressure to proportional engine load to control the addition of fuel to, and the the dumping of fuel from, a chamber at the end of the timing piston to tix the axial position of the timing piston and hence the angular position of the cam.

The present invention relates to fuel pumps of t-he type utilized in fuel injection `systems for delivering measured charges of fuel to the nozzles of an internal combustion engine and more particularly to the means for automatically varying the timing of the pump in response to engine operating conditions. The device of the present invention speciiically concerns a fuel pump in which the fuel charges are delivered by pistons radially slideable in a driven rotor and inwardly actuated by an annular cam encircling the pistons.

As disclosed in my prior U.S. Patent 2,660,992, entitled, Automatic Timing Means for Fuel Pumps, issued Dec. 1, 1953, the annular cam may be angularly shifted to adjusted the timing of the fuel delivered -to the engine. This is accomplished by the use of an arm connecting the cam to a reciprocable plunger which is axially adjusted in accordance with engine operating conditions to provide the desired timing of -the fuel delivery to the engine. In order to support the annular cam in the desired adjustably positioned angular position corresponding with the engine operating conditions as they exist from time -to time, the cam, the piston and connecting means have been required to provide the necessary mechanical strength to withstand the sharp intermittent loads imposed as the cams are actuated radially inwardly by the piston.

A principal aim of this invention is to provide an automatic timing device for fuel pumps of the type referred to which will be efficient and sensitive in operation so as to provide the desired correlation between engine operating conditions and the timing of fuel injections under all conditions of operation and yet minimize the strain imposed on the plunger, the connection means and the cam ring. Included in this aim is the provision of a timing device responsive to both the speed and load on the engine.

A further object of ythis invention is to provide such j 3,394,688 Patented July 30, 1968 a device which can withstand the high pressures or other forces normally encountered in regulation of this type without danger of failure and which will operate without any binding or locking of the moving parts which might result from operation under such high pressure.

Another object of this invention is to provide an improved construction wherein the cam ring is supported by the pump housing and need not itself have sufficient strength to withstand the pumping pressures.

Other objects will be in part obvious and in part pointed out more in detail hereinafter.

The invention accordingly consists in the features of construction, combination of elements and arrangement of parts which is exemplified in the construction hereafter set forth, and the scope of the invention is indicated in the appended claims.

In the drawings:

FIG. 1 is a longitudinal cross-sectional View, partly broken away, of a fuel injection pump embodying the present invention;

FIG. 2 is an enlarged fragmentary sectional view taken along the lines 2 2 of FIG. l;

FIG. 3 is a fragmentary sectional view taken along the lines 3-3 of FIG. 2;

FIG. 4 is an enlarged Icross-sectional view taken along the lines 4 4 of FIG. l;

FIG. 5 is a top view of the cam ring of this invention;

FIG. 6 is a side View of the cam ring of FIG. 5; and

FIG. 7 is a fragmentary view of the bearing surface taken along the lines 7-7 of FIG. 4.

The following is a detailed description of the invention.

Referring now to the drawings in detail, in which like numerals refer to like parts throughout the several igures, a pump exemplifying the present invention is of the type now commercially available for supplying fuel charges to an associated internal combustion engine. The pump comprises an external housing or casing 10 having an axial bore or opening 12 rotatably supporting a pump rotor or distributor 14.

At the right end of the housing 10, as viewed in FIG. l there is mounted a vane-type fuel supply or transfer pump 18 driven by the rotor 14 and having an inlet port 16 and a discharge port 17. A diagonal inlet passa-ge 20 delivers fuel to a transfer pump 18 from an inlet pipe 22 which is connected to a fuel supply reservoir. The transfer pump delivers fuel under pressure through an outlet passage 24 in the housing 10 to an air separator 26 from whence the fuel flows through a passage 28 (FIG. 2) in the housing 10 to a longitudinal bore 30 in the housing. A slideable spring biased pressure regulating valve 32 (FIG. 3) is mounted in the bore 30` for regulatin-g the output pressure of the pump 18. Regulating valve 32 delivers fuel to the centrifugal metering valve 34 at a pressure correlated with the speed of the driving engine through conduit 33 and returns excess -fuel to the transfer pump inlet conduit 20 through conduit 35.

The high pressure charge pump generally denoted by the numeral 40 is formed by a transverse bore 42 in rotor 14 in which are slideably mounted a pair of opposed plungers 44. The outer ends of the plungers engage against shoes 46 which are slideably mounted in transverse .passages 4-8 formed by the bifurcated end 47 of a separable drive shaft 60 aligned with bore 42. As shown in FIG. 4, the bifurcated end of drive shaft 60 also provides a pair of at opposed shoulders which engage complementary shoulders 45 on the rotor 14 to drive the same.

Surrounding the rotary member 14 is a generally circular or ring-like cam ring 50 preferably constucted of hadened steel which encircles the rotor 14 in the plane of revolution of the plungers 44 and is mounted for angular adjustment within an annular bore 49 in the pump housing. The cam has a plurality of pairs of diametrically opposed inwardly extending cam lobes 52 which are adapted to actuate the plungers 44 inwardly simultaneously for discharging fuel from the pump, it being understood that the rollers 43 and the roller shoes 46 are disposed between the plungers 44 and the cam 50 whereby the rollers 43 act as cam followers for translating the cam contour into this reciprocal movement of the plungers 44. The C- shaped ring 56 secured to the charge pump by a screw fastener 58 (FIG. 4) provides an adjustable outer resilient top for the roller shoes 46. A seal 62 is provided to prevent leakage of fuel into or out of between the shaft 60 and the housing 10.

Upon rotation of the drive shaft 60, the transfer pump 1-8 and the charge pump 40 are rotated to supply measured charges of fuel under pressure to a plurality of fuel pump outlets 64 having suitable connections with the fuel injection nozzles of an associated engine, during the outward or intake stroke of the plungers 44 fuel is delivered to the charge pump from the metering lport 41 by a passage 66 in the housing 10 and a diagonal passage l68 in the rotor 14. During the inward or discharge stroke of the plungers 44, fuel is delivered under high pressure by an axial passage 76 to a pressure-operated delivery valve 77 and a generally radially extending delivery passage 78 adapted for sequential registration with a plurality of angularly spaced radial distributor passages 63 in fluid communication respectively with a plurality of pump outlets `64, only one of which is shown for convenience of illustration. It is to be noted that a one-way check valve 68a prevents reverse flow through inlet passage 68 during the discharge stroke of charge pump 40.

The metering valve 34 may be adjusted in any suitable manner, and in the illustrated embodiment is shown as being a spool valve axially adjustable and rotatably driven by the centrifugal governor 31 against the force of spring 29, the bias of which may be adjusted or varied by lever 25. The governor 31 is provided with a gear 85 driven by gear 84 secured to shaft 60. Inasmuch as the axial force of centrifugal governor 31 is a function of engine speed, the position of the metering valve 34 and hence the restriction offered by the metering port 41 due to the axial shifting of the spool 34 will govern the engine at a speed which may be selected by varying the bias of the compression spring 29.

Referring now specifically to FIG. 4, there is shown a transverse bore 100 in the housing 10 in which an axially movable plunger 102 is reciprocably mounted. A passage 104 (FIG. 1) from the air separator 26 is shown as being in communication with the bore 100 to deliver regulated transfer pump outlet pressure thereto. In the illustrated design, the plunger 102 includes a pilot valve 105 positioned in a chamber 106, one end of which continuously communicates with housing passage 104 through passage 108 in plunger 102. A one-way valve is positioned in pilot valve 105 to prevent the reverse ow of fluid through the passage 108 as a result of intermittent pulsations of force imposed on the plunger 102 due to the operation ofthe charge pump.

Pilot valve 105 is provided with a biasing spring 109. Spring 109 opposes the transfer pump outlet pressure acting on the right end of the pilot valve with the result that transfer pump output pressure will urge the pilot valve 105 to the left, as seen in FIG. 4, against the bias of compression spring 109. The le-ft end of spring 109 engages a slidable piston 125 having the same cross-sectional area as pilot valve 105 A. spring 126 having a lower spring rate than spring 109 is positioned between piston 125 and adjusting screw 103. The chamber 127 between the adjusting screw 103 and piston 125 continuously communicates with annulus 51 through passage 128 so that the pressure in chamber 127 equals that of the metered fuel in annulus 51.

Pilot valve 105 is also provided with an annular land 110 which is axially shiftable over port 111 in the plunger 102. Port 111 communicates through passage 112 to a chamber 113 formed in the end of transverse housing bore to deliver fuel under pressure thereto when annular land of the pilot valve is moved to the left to provide communication between passage 106 and port 111 via annulus 107 and passage 112. Inasmuch as the transfer pump pressure is a function of engine speed, the bias imposed on the pilot valve 105 by the transfer pump pressure and hence the position assumed by the pilot valve is dependent on engine speed. This, in turn, determines whether the port 111 communicates with passage 112 to receive additional fuel from the transfer pump (and hence shift plunger 102 to the left to advance the time of injection) or the port 111 communicates with pas sage 114 to dump a portion of the fuel trapped in the chamber 113 into the pump housing through passage 114 to permit the plunger 102 to move to the right. As shown in FIG. 4, the left end of annulus 107 is of reduced cross section to throttle the flow of fuel therethrough and stabilize the operation of the pilot valve.

Since one end of the spring 109 engages axially slidable piston 125, it will be apparent that the position of the pilot valve 105 is also dependent upon the pressure of the metered fuel in chamber 127. Accordingly, with an increase in engine load (and hence an increased opening of the metering port 41 `by governor 31 to maintain constant engine speed) the pilot valve will move to the right to assume an equilibrium position with the plunger 102 and cam ring 50 positioned to cause a later injection of fuel by the charge pump than with a smaller lload on the engine.

For operatively connecting plunger 102 and cam 50, there is provided an arm 115 having a cylindrical body 116 mounted in a complementary radial bore 118 in the plunger 102. The connector has an integral head 120 closely received within a bore 101 of the cam ring 50 which serves as a socket therefor. The plunger 102 is recessed at 122 to receive a portion of the cam ring 50 extending within the bore 100, and the connector 1'15 is preferably dimensioned to reciprocate with the plunger 102 within the peripheral confines of the bore 100. A snap ring 124 seated in an annular groove in the connector v115 prevents excess axial movement of the connectoi toward the cam ring.

In accordance with another aspect of this invention, the cam ring 50 is split :as best shown in FIGS. 5 and 6. Preferably this split is centered in the bore 101 of the cam ring in which the head of the connector 115 is positioned.

Referring specifically to FIG. 4, the movement of the charge pump is in a clockwise direction. It will thus be seen that as the rollers 43 ride up on the cams 52, the resultant force is imposed on the left side (as viewed in FIG. 4) of the head 120 of the connector 115. The resultant force of the -rollers 43 riding up on the diametrically opposed pair of cams 52 will also exert a radial force tending to enlarge or expand the cam ring 50. The cam ring will be seated against the mating bearing surface of the bore 49 in view of the split therein. Thus the metal of the housing surrounding the cam ring reinforces the cam ring so that the cam ring may be reduced in thickness and need not alone provide the necessary strength for withstanding the pumping forces of the charge pump.

Significant to the present invention is the provision on one of the journalled bearing surfaces of the cam ring and the bore 49 of an arrangement for increasing the friction therebetween without interfering with the easy angular adjustment of the cam ring by the plunger 102. In the illustrated embodiment, this friction increasing means takes the form of a knurled, grooved, or otherwise roughened surface which is preferably provided on the bearing surface 49 of the housing. Such a surface will disturb or destroy the lubricating lm between the journalled bearing surfaces to increase the' coeicient of friction therebetween.

It will -be seen that as the rollers 43, which turn clockwise as viewed in FIG. 4 ride up on the leading slope of the cams 52, the eifective diameter of the cam ring 50 will 'be increased so that the cam ring is bottomed against the bore 49 `and the frictional resistance therebetween serves to resist the movement of the cam ring during the pumping stroke and hence minimizes the sudden shock which would otherwise be imposed on the connector 115 and the plunger 102.

The design is one in which the frictional forces resisting the angular movement of the cam ring 50 during the pumping stroke of the charge pump is increased in proportion to the in-crease of the force tending to angularly shift the cam ring. Moreover, due to the resilience of the tempered cam ring, it automatically achieves a smaller diameter of about 1 mil when the rollers 43 are not engaging the lobes of the cam. Thus this invention does not materially affect the sensitivity or responsiveness of the cam in shifting to another angular position in response to a change in engine speed and an axial shift of the plunger 102.

Various modifications and adaptations of the invention above-described will become readily apparent to those skilled in the art. For example, the means for increasing the friction during the pumping stroke could be provided on the outer surface of the -cam if desired. It is therefore the intention to include within the scope of the appended claims such modifications and adaptations which do not depart from the spirit land scope of the invention as set forth in the appended claims.

I claim:

1. In a timing device for fuel injection pu-mps of the type described including a cam ring member, having an outer cylindrical bearing surface seated in a complementary shaped cylindrical bearing surface formed in a cavity in the pump housing and angularly shiftable for controlling the delivery of fuel to an associated engine, a pair of radially slideable pistons movable radially in correlation with the cam surface of the cam ring member, a regulating member mounted for movement in response to an operating condition of the engine and means interconnecting the regulating member and the cam ring memiber to adjust the angular position of the cam ring member in correlation with the operating condition of the engine, the improvement wherein the cam ring member is longitudinally split and contractable in outside diameter to reduce bearing loading to permit rotation of said cam ring on the cylindrical bearing surface of the cavity when unloaded, the cam ring member further being resiliently expansible in outside diameter due to the reaction forces imposed by the pistons on said cam ring.

2. A device as recited in claim 1 wherein the interconnecting means engages the cam ring member adjacent the split end thereof.

3. A devi-ce for use with a fuel injection pump of the type having a movable cam to vary the timing of delivery of fuel to an associated engine comprising means forming a pressure chamber, a position in the chamber connected with said cam for moving the same in a cam advancing direction upon an increase of fluid in said charnber, a passageway communicating with said chamber for receiving and discharging fuel therefrom, a first source of fluid having a pressure correlated with engine speed, la second source of fluid having a pressure correlated with engine load, and a pilot valve responsive to said first pressure and said second pressure for selectively providing communication between said passageway and a source 0f fluid under pressure to increase the quantity of fluid in said chamber in response t-o an increase in engine speed and for providing communication between said passageway and a discharge passage for dumping fuel from said chamber to move the piston in said cam retarding direction in response to an increase of load on the engine.

4. A device as recited in claim 3 wherein the pilot valve is mounted in -a bore in said piston and is axially shiftable t-o cover and uncover a port of said passageway in the wall of said piston, the port being uncovered to admit fluid to said chamber when the pilot valve is in one axial direction and uncovered to dump uid therefrom when the pilot valve is in the other axial direction.

`5. A device as recited in claim 4 wherein said pilot valve is provided with an internal passage in continuous communication with the source of fluid for supplying fluid to said cham-ber and further includes a one-way valve for preventing reverse ow of fluid therethrough.

6. A device as recited in claim 1 wherein at least a portion of one of the cylindrical bearing surfaces of said cam ring and said pump cavity is treated to increase its coefficient of friction under increased loading between said bearing surfaces.

7. A device as recited in claim 6 wherein the cylindrical bearing surface of the pump cavity is provided with a knurled finish.

References Cited UNITED STATES PATENTSY `2,919,687 1/1960 Friediander 12s-139.13 2,935,062 5/1960 Anlage-rein 1o3 2.1 3,051,154 8/1962 Kemp 123 139 3,116,728 1/1964 Evans 12s-139 LAURENCE M. GOODRIDGE, Primary Examiner.