US3119340A - Variable pump for fuel injection supply - Google Patents

Description

Jan. 28, 1964 H. R. SCIBBE VARIABLE PUMP FOR FUEL INJECTION SUPPLY Filed Sept. 22, 1961 2 Sheets-Sheet 1 IN V EN TOR. flara/a R. 5c z'fihz Jan. 28, 1964 H. R. SCIBBE VARIABLE PUMP FOR FUEL INJECTION SUPPLY Filed Sept. 22. 1961 2 -Sheet 2 @m Q wN m5 (w R A M W H.

United States Patent 3 119 349 VARHABLE PUMP FUR FUEL INJECTION SUPPLY Harold R. Scihbe, Chardon, Ohio, assignor to Thompson Raine Wooldridge Inc, Cleveland, Ohio, a corporation of Ghio Filed Sept. 22, 1961, Ser. No. 140,012 2 Claims. (Cl. 103-38) The present invention relates to improvements in fuel injection systems for high speed, four cycle, spark ignition internal combustion engines and to an improved variable displacement fuel pump for a fuel injection system.

The invention contemplates the provision of a system employing a variable output pump having a plurality of pistons operating in cylinders at controllable stroke lengths. The pump delivers to a distributor which provides for periodic uniform releases of the fuel to lines leading to fuel injectors. The distributor is driven from the engine and a shaft for driving the pump is mechanically connected through gearing to the distributor to be driven at a speed ratio relative to the distributor which cannot be expressed exactly in whole numbers so that starved or rich phases in the pump operation will not continually occur at releases to the same injectors but will move on to other injectors. The pump has a plurality of radially extending pistons embodying an improved seal with the cylinder wall, and the stroke of the pistons is controllable by a plunger in the pump shaft which varies the eccentricity of a simplified driving head. The plunger is spring loaded to increase the delivery of the pump and an arm acts against the spring to obtain a positive movement for reducing the pump delivery.

It is an object of the present invention to provide an improved simplified reliable variable delivery pump particularly adapted for use in a fuel delivery system for fuel injection engines.

Another object of the invention is to provide an improved control mechanism for varying the output of a reciprocating fuel pump employing radially extending pistons driven by a centrally located eccentric.

A still further object of the invention is to provide an improved seal for a fuel pump between the piston and the wall of the cylinder.

A further object of the invention is to provide an improved pump construction for a fuel system wherein the formation of air and vapor pockets is reduced.

A still further object of the invention is: to provide a simplified piston and drive construction in a pump of a type having radially extending pistons driven by a centrally located oscillating eccentric having a variable eccentricity.

Other objects and advantages will become more apparent from the teachings of the principles of the invention in connection with the disclosure of the preferred embodiment thereof in the specification, claims and drawings, in which:

FIGURE 1 is an end elevational view of a fuel delivery unit including a pump and a distributor constructed in accordance with the principles of the present invention;

FIGURE 2 is a vertical sectional view taken substantially along line IIII of FIGURE 1;

FIGURE 3 is a vertical sectional view taken substantially along line III III of FIGURE 2;

FIGURE 4 is a horizontal sectional view taken substantially along line IV-IV of FIGURE 2;

FIGURE 5 is an enlarged fragmentary detail view showing parts of the seals for the pistons before assembly; and

FIGURE 6 is a fragmentary enlarged detail view showing the seal parts of FIGURE 5 after assembly.

As shown on the drawings:

FIGURE 2 illustrates a mechanism having a pump 10 with a variable delivery for pumping fuel. The fuel flows to a distributor 11 which at intermittent periodic intervals releases the pumped fuel to individual fuel injectors, not shown, which supply an internal combustion engine. The fuel flows from the pump to the distributor through a conduit means 12 and communicating with the conduit means is an accumulator 13 which collects the fuel from the pump between distributor releases and completely discharges its collected fuel during the periods of distributor release.

Also communicating with the conduit means 12 is an enrichment device 15 which is filled with fuel from the metering piunp 11 and selectively discharges this fuel to the distributor 11 when the engine is accelerated.

The metering pump 10 and distributor 11 are incorporated in a unit housing 16, FIGURES 1 and 2, made up of parts which are suitably clamped together such as by cap screws or bolts with the parts having gaskets therebetween. These parts need not be described in detail inasmuch as their construction will be apparent from the drawings and the entity maybe generally referred to as the housing 16. The distributor 11 and accumulator 13 are carried in housing part 16a and plate 16b, and the metering pump in parts 160, led. Pumping chambers and valves are carried on side housing projections 16e, FIG- URES 3 and 4. The housing is adapted to be suitably mounted on an engine tobe driven by the engine in the position shown in FIGURES 1 and 2 such as by being connected to the timing shaft. The mechanism has a distributor shaft '17 which is driven at one half the speed of an engine to which fuel is delivered so that in a four cycle engine the distributor 11 will release fuel once for one injection per four stroke cycle of the typical multicylinder engine.

Fuel is received through a line connected to a fuel intake opening 18 in the housing 16 and usually fuel will be delivered to the apparatus from a fuel tank by a supply pump so that the intake 18 will receive pressurized fuel. The distributor is connected to individual fuel lines 19a which lead to the injectors.

The metering pump 1ft is driven from the distributor shaft 17 which is supported in the housing 16 in a ball bearing assembly 18' and a cylindrical bearing surface 19. A circular sealing ring 29 is positioned around the shaft in the housing to prevent the escape of lubricant and a. ring 21 is also positioned around the shaft to prevent the escape of fuel from the distributor 11, as will later be described.

The pump 10 is driven by a gear 22 on the shaft 17 driving a gear 23 pinned to the pump shaft 24 which is supported in a ball bearing assembly 25.

The ratio of the gear 22 on the shaft 17 to the gear 23 on the pump shaft is preferably one which cannot be expressed exactly in whole numbers, such as 23/30 or 30/23; 25/28 or 28/25; 20/33 or 33/20. Inasmuch as the pump is a piston type, such fractional gear ratios will preclude the possibility of any one piston consistently delivering fuel through the same port of the distributor and hence to the same engine cylinder. If small differences exist between the pistons, piston chambers, piston stroke links or seals of the pumping element a slight inequality of fuel delivery may occur between pistons and this will not consistently result in the inequality being reflected in the fuel delivered to one or more engine cylinders but will move through the sequential injections to all of the cylinders. For example, engine failures due to consistently lean mixtures on one cylinder of the engine are prevented; While excessively rich or lean injections could occur due to manufacturing differences, these conditions will move through all of the cylinders of the multicylinder engine.

The bearing 25 for the pump shaft 24 and the pump pistons are lubricated through a lubrication connection 26 in the housing and lubricant flows through suitable passages through a passage 27 to the bearing 25 and through passages such as 28 leading to the individual pump pistons and their seals. Lubricant is also delivered to the hollow chamber 33 which contains the mechanism for driving the pump pistons.

As shown in FIGURES 2 and 3, the pump is provided with three radially extending pistons 29, 3t) and 31 slidably supported in radially bored cylinders 29a, 3% and 31a in the housing 16. An odd number of pistons are provided and a greater number may be employed if desired retaining an odd number. The pistons are movable radially outwardly in a discharge stroke and radially inwardly in an intake stroke and are urged inwardly by springs such as 32 surrounding the inner ends of the pistons and seated in annular recesses in the wall of the chamber 31. Split snap rings 34 seat in annular grooves in the pistons to hold washers against which the springs engage. Inasmuch as the construction of each piston is the same, the arrangement of the piston 30 only need be described in detail. The pistons are uniformly cylindrical in shape and size and are therefore inexpensive and simple to construct and can be formed out of a continuous length of stock material.

The pistons are driven by a head 35 eccentrically carried at the lower end of the pump shaft 24. The head 35 rotatably supports a roller 36 which is rotatably mounted on a stud 35a on the head and the roller 36 rolls on the stud to reduce friction between the roller and pistons.

The head 35 is carried in a radially extending supporting slot 37 on the shaft 24 and its eccentricity with respect to the axis of the shaft is controllable by a bell crank 38 supported on the shaft. The lower arm of the bell crank is held in a recess 39 in the head 35 and the upper arm of the bell crank 39 is received in a recess 4% in a plunger 4-1 coaxially carried in the hollow center of the pump shaft 24. A cross pin 41a extends across through an axially elongated slot 41b in the plunger 41 and the pin 41a is mounted in the shaft 24. This pin 41a also functions to lock the gear 23 to the pump shaft. A spring 42 in an axially extending recess in the end of the shaft 24 engages the underside of an enlarged head 410 of the plunger 41 to urge it to the left, as shown in FIGURE 2. This tends to move the head 35 to increase the eccentricity thereof and increase the pump delivery. The action of the spring 42 is resisted by an arm 43 hearing on the upper end of the head of the plunger 41 and mounted on a shaft 44. The shaft 44 is connected to a fuel control mechanism which operates an arm 45, FIGURE 1, on the shaft 44.

Spring 42 on coaxial plunger 41 eliminates lash in the external control linkage that actuates arm 45. It tends to minimize metering hysteresis conunon to manifold pressure sensitive controls. While in the illustrated design the spring urges the coaxial plunger to increase the eccentricity of the drive and the stroke of the pistons, the opposite effect could also be employed. For other applications, the spring could be positioned to hold the drive concentric and the pistons at zero stroke. The external control linked to the plunger control member (arm 45) would then move to increase eccentricity and piston stroke.

The fuel control mechanism will determine the displacement and output of the metering pump 10 and is operated in accordance with various factors of engine conditions such as the intake manifold pressure and engine temperature. A manual input signal is also provided by an accelerator, not shown and the fuel control mechanism is also not shown inasmuch as various devices may be employed as will be appreciated by those skilled in the art.

Each of the pump plungers are sealed by an O-ring 47 in an annular groove 47a in the housing, as shown in FIGURES 2, 3, and 6. As particularly shown in FIG- URES 5 and 6, the width W of the groove 47a in an axial direction is greater than the cross sectional diameter W of the uncompressed O-ring 47. The diameter D of the base of the groove 47a is less than the outer diameter D of the O-ring 47. The diameter D of the piston 35 is less than the inner diameter D of the O-ring 47. When assembled, as shown in FIGURE 6, the radial compression of the base of the groove 47a on the outer sunface of the O-ring forces the inner diameter of the ring to contact the cylindrical piston surface. The dimensions of the O-ring, O-ring groove, and piston are designed so that the contact of the inner diameter of the O-ring with the piston is sufiicient to seal against the fuel pressure but light enough to prevent excessive friction during reciprocation of the piston within the seal. The axial Width of the O-ring groove prevents axial compression of the O-ring. The cylindrical bore 30a in which the piston slides is relieved at its outer end 3% so as to be of a slightly larger size than the inner end of the bore to thereby prevent scratching contact between the piston and the cylinder where the piston slides through the O-ring '47. This insures that the piston will retain its finish at that location and not wear the O-ring but retain a good seal. Also, the lubricant passage 28 opens to the cylinder inwardly of the O-ring so that the piston is subjected to lubricant at all times Where it slides through the O-ring.

As shown in FIGURES 2 and 3, the fuel enters the intake 18 of the housing and flows through a passage 49 that forms a loop. Off this loop are branch passages 50, 51 and 52 for supplying pumping chambers 48 at the end of the pump pistons. Fuel intake into the pump chambers 48 flows through an intake port 510 past a check valve, FIGURE 4, having a ball check 53 held by a spring 54 against a seat 55 so as to close the intake passage when the pump piston moves outwardly. Flow out of the pumping chamber 48 is through a port 56a past a ball check valve 5611 which closes during the intake stroke of the piston. The ball check valve 56b is held against a valve seat 55c by a spring 56d. The pumping chambers 43 and the check valves are conveniently contained in housing projections 16a, FIGURES -1 through 4, mounted on the housing at the ends of each of the pump pistons.

Delivery from the pumping chamber 48 is through a passage 56 leading up into a chamber 57 in which is lo: cated a distributor plate 58. The passage 56 and the chamber 57 constitute the conduit means leading from the pump discharge to the distributor.

It is to be noted that the pumping chamber receives fluid through the port 51:: and delivers fluid through the port 56a. These ports and the passageways connected thereto are arranged so that fluid flow through the pumping chamber 48 is in an upward direction thus facilitating the escape flow of fluid vapor and entrained air through the chamber. All of the fluid passages in the pump are designed to prevent the trapping :of fuel vapor or entrained air in the pumping elements. This makes the pump self-purging of vapor and air and greatly reduces the number of pump revolutions required to purge a vapor locked pump.

As shown in FlGURE 2, a distributor valve or valve disc 58 has a flat smooth undersurface which sealingly slides against a surface 59 in the chamber 57 and is held downwardly by a spring 60 and is driven by the shaft 17. Below the distributor valve 58 in the distributor plate 16b are a series of evenly spaced circumferentially arranged relief ports 62 which conduct fuel each time an elongated port 61 in the distributor valve 58 passes over them. This intermittently at even intervals relieves the fluid fuel from the distributor chamber 57 and the fuel sequentially flows out through the lines 19 to the individual injectors 14.

The accumulator 13 is in communication with the conduit means 12 between the pump and distributor has an expansible chamber in the form of a cylinder 63 in which is located a piston 64. The piston is spring loaded by a spring 66 which urges the piston 64 in a direction to discharge the fuel from the chamber 63-. An annular piston seal 65 surrounds the piston.

The spring 66 has a natural frequency greater than the accumulator exciting frequency, namely the opening and closing of the successive distributor ports. The accumulator thus empties itself for each release of the distributor.

The accumulator 13 is located below the distributor chamber and in a position so that air or fuel vapor cannot be trapped. The cylinder 63 is shown in a horizontal position below the distributor.

Also in communication with the distributor chamber 57, or in other words, in communication with the conduit means 12 between the pump and distributor, is an accelerator chamber shown in the form of an elongated cylinder 67. The chamber 67 communicates with the distributor chamber 57 through openings '72 through the distributor plate. Within the chamber 67 is a piston 65 having a piston ring 69. The piston is mounted on a piston rod 7t) suitably connected to an accelerator pedal, not shown.

Movements of the accelerator pedal to decelenate a low the chamber 67 to fill from fuel delivered by the pumplt). As the accelerator is moved in an accelerating direction, the piston 63 will force fuel out of the chambers 67 through the openings 72 which will cause the distributor to deliver an increased quantity of fuel to the engine. The distributor valve 57 is held down against its smooth surface 59 by a coil spring 60 and the how of fuel through the passages 72 :have no effect on the normal operation of the distributor.

The use of this accelerator chamber 67 enhances the response of the engine to movements of the accelerator pedal without adding to the flow rate through the variable displacement pump :10. This therefore occurs without sacrifice to the general fuel economy. It is also to be noted that as the accelerator is release-d, the variable chamber 67 provides an escape chamber for the fuel in the distributor thereby enhancing the rapid cut-off of fuel supplied to the engine as the accelerator is released to prevent delivering over enriched fuel to the engine and consequent smoking and increase in smog effects.

While the fuel injection nozzles may be of various designs, the nozzle 14 is shown schematically as including an injection opening 74 against which seats a valve member 73 held against the opening by a tension spring '75. The tension spring 75 is such that it opens at a lower fuel pressure than that required to depress the accumulator spring 65. Thus with the accumulator discharge pressure being greater than the injector nozzle opening pressure, the injector will open as soon as the distributor 11 releases the fuel and will stay open during the time the accumulator piston 64 is emptying the accumulator chamber and during the time the distributor ports are in alignment.

As a brief summary of operation, the power or distributor shaft 17 is driven from the engine to provide a fuel release for each fuel intake stroke of the engine, and through the gears 22 and 23 drives the pump it). 1 e delivery of the pump is varied by the arm 43 pushing down on the plunger 41 which determines the eccentricity of the head 35 and the stroke of the pump pistons 29, 30 and 31. Fuel flows in through the intake 18 past the intake check valve 53 on the intake stroke of the piston 30 and a check valve 56b, FIGURE 4, closes off the delivery passage 56. On the delivery stroke of the piston fuel flows through the passage 56 to the distributor chamber 57. As the distributor valve 58 rotates quantities of fuel are intermittently released as the port 61 successively aligns itself with the ports 62. The accumulator chamber 63 receives fuel between port releases and discharges during the release periods.

The multiple piston metering and pressure generating pump has an advantage in freedom from high speed limitations that are placed on a single piston injection pump that must reciprocate through one stroke for each cylinder of a multicylinder engine. The metering pump with a rotary distributor has considerable manufacturing advantages over types heretofore used requiring individual pistons, cylinders, valves and passages all of which must be precisely matched to maintain distribution equality for each cylinder of a multicylinder engine.

The rotating distributor of the unit is normally driven at half engine crank shaft speed to provide one injection per four stroke cycle of the typical multicylinder engine. The metering and pressure generating pump is gear driven from the rotary distributor shaft at a speed selected to best suit several factors, although preferably driven at a speed ratio which is not an exact whole number, as above described. The factors which determine the speed at which the pump is driven include pump performance efiiciency and endurance reliability and the maximum delivery required by the particular engine displacement. A significant advantage is that the same pump unit may be used to accommodate engines of different sizes. For example, to accommodate a passenger car engine, a pump constructed as shown but using five pistons was geared to make 4.55 piston strokes for every two-engine revolutions. An identical unit was used to fuel a much larger displacement engine by employing a gear ratio that provided 5.5 piston strokes per two-engine revolutions.

The versatility of the system is shown in the pumping unit illustrated wherein three pistons are employed for the pump. By changes in piston diameter, maximum piston stroke, and pumping element driving gears, a three piston pump is capable of fueling a small displacement cubic inch) compact car engine or a large displacement (540 cubic inch) light aircraft engine. Cast housings, mechanical linkages and controls for the range of engine sizes remain identical effecting advantages in servicing, assembly, and reduction of manufacturing cost.

It is to be noted that the pistons are of uniform diameter so that they can be made of cylindrical stock mate rial. The simple manner in which the return springs are attached, the support for the springs and overall drive arrangement make a reliable inexpensive construction possible.

It will be understood that while the distributor usually is employed to accomplish one fuel release and one injection per four stroke cycle it may also be used to pro vide two injections per four stroke cycle. This method of distribution halves the large fuel quantities required per cycle and precludes the necessity for larger metering pump components.

Thus it will be seen that I have provided an improved pump and distributor arrangement incorporating an improved pump and system which meets the objectives and advantages above set forth. The arrangement lends itself to a compact unit device capable of continued operation without adjustment.

The drawings and specification present a detailed disclosure of the preferred embodiments of the invention, and it is to be understood that the invention is not limited to the specific forms disclosed, but covers all modifications, changes and alternative constructions and methods falling within the scope of the principles taught by the invention.

I claim as my invention:

1. A variable displacement fluid pump comprising,

a pump drive shaft,

a pump piston slidably mounted in a cylinder extending radially from the drive shaft,

an eccentric drive having an element thereof in dn'ving relationship to the piston and being 'adjustably connected to the shaft for controll-ably varying the eccentricity for reciprocating the piston in its cylinder,

a plunger slidably mounted coaxially with said shaft and non-yieldably connected to said eccentnic drive for changing its eccentricity with axial movement relative to the shaft,

a spring engaging the plunger and urging it in a first axial direction to increase the eccentricity of the drive element and the stroke of the piston,

an operating surface on said plunger facing in said first direction,

and a control member engaging said plunger surface and moving the piunger against the spring for tie creasing the eccentricity of the drive and the stroke of the piston for positive control in a direction to reduce the pump output.

2. A variable displacement fluid pump comprising,

' a pump drive shaft,

a pump piston slid-ably mounted in a cylinder extending radially from the drive shaft,

an eccentric drive having an element thereof in driving relationship to the piston and being mounted on a slide on the shaft and having a bell crank connected to the slide for positioning the drive element eccentrically relative to the shaft,

3. plunger slidably mounted coaxially with said shaft and non-yieldably connected to said bell crank for changing the eccentricity of the drive element with axial movement of the plunger relative to the shaft,

a spring engaging the plunger for urging it in a first axial direction to increase the eccentricity of the drive element and the stroke of the piston,

a plunger surface facing in said first direction, and a control lever engaging said plunger surface and moving the plunger against the spring for decreasing the eccentricity of the cam and the stroke of the piston for positive control in a direction to reduce the pump output.

References (Zited in the file of this patent UNITED STATES PATENTS 831,890 Plane et a1. Sept. 25, 1906 1,982,958 Kraus Dec. 4, 1934 2,257,854 Peterson Oct. 7, 1941 2,336,996 McDonough Dec. 14, 1943 2,370,383 Wallace Feb. 27, 1945 2,404,175 Holden et al. July 16, 1946 2,442,488 Fisk June 1, 1948 2,539,277 Schroepfer Ian. 23, 1951 2,661,729 Reiners Dec. 8, 1953 2,746,442 Roosa May 22, 1956 2,795,195 Amblard June 11, 1957 2,828,696 Wright Apr. 1, 1958 2,902,938 Ebert Sept. 8, 1959 3,019,738 Zubaty Feb. 6, 1962 3,077,872 Allen Feb. 19, 1963 FOREIGN PATENTS 449,429 Canada June 29, 1948 857,594 France Apr. 22, 1940 713,778 Germany Nov. 15, 1941 569,759 Great Britain June 7, 1945 824,152 Great Britain Nov. 25, 1958

Claims (1)

1. A VARIABLE DISPLACEMENT FLUID PUMP COMPRISING, A PUMP DRIVE SHAFT, A PUMP PISTON SLIDABLY MOUNTED IN A CYLINDER EXTENDING RADIALLY FROM THE DRIVE SHAFT, AN ECCENTRIC DRIVE HAVING AN ELEMENT THEREOF IN DRIVING RELATIONSHIP TO THE PISTON AND BEING ADJUSTABLY CONNECTED TO THE SHAFT FOR CONTROLLABLY VARYING THE ECCENTRICITY FOR RECIPROCATING THE PISTON IN ITS CYLINDER, A PLUNGER SLIDABLY MOUNTED COAXIALLY WITH SAID SHAFT AND NON-YIELDABLY CONNECTED TO SAID ECCENTRIC DRIVE FOR CHANGING ITS ECCENTRICITY WITH AXIAL MOVEMENT RELATIVE TO THE SHAFT, A SPRING ENGAGING THE PLUNGER AND URGING IT IN A FIRST AXIAL DIRECTION TO INCREASE THE ECCENTRICITY OF THE DRIVE ELEMENT AND THE STROKE OF THE PISTON, AN OPERATING SURFACE ON SAID PLUNGER FACING IN SAID FIRST DIRECTION, AND A CONTROL MEMBER ENGAGING SAID PLUNGER SURFACE AND MOVING THE PLUNGER AGAINST THE SPRING FOR DECREASING THE ECCENTRICITY OF THE DRIVE AND THE STROKE OF THE PISTON FOR POSITIVE CONTROL IN A DIRECTION TO REDUCE THE PUMP OUTPUT.

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