US2114565A

US2114565A - Fuel injection pump

Info

Publication number: US2114565A
Application number: US31267A
Authority: US
Inventors: Kovach Frank
Original assignee: H V MARTIN
Current assignee: H V MARTIN
Priority date: 1935-07-13
Filing date: 1935-07-13
Publication date: 1938-04-19
Anticipated expiration: 1955-04-19

Description

pri 19A, H933, F KOVACH @Elli-,5

FUEL INJECTION PUMP Filed July 13, 1935 2 Sheets-Sheet 2 Patented Apr. 19, 1938 PATENT GFFICE FUEL INJECTION PUMP Frank Kovach, Lincoln, Nebr., assignor of one-v half to H. V. Martin, Lincoln, Nebr.

Application July 13, 1935, Serial No. 31,267

4 Claims.

This invention relates to pumps and more particularly to the control of the stroke and the speed of the. pistons of reciprocating pumps, especially for oil and Diesel engines.

'I'he primary object of the invention is to provide an extremely simple and accurate device for precisely controlling the effective stroke of reciprocating pumps. Incidentally an object of the invention is to reduce the number of parts in such controls to about the same as that required for a fixed output pump.

Another object is to provide an extremely sturdy feed control for fuel injection pumps particularly for high speed oil and Diesel engines, which control may be varied micrometrically over a full range without seriously affecting the timing.

Another object is to combine in one simple unit a device which not only controls the amount of the fuel charge but which also and at the same time varies the rate of fuel injection and yet approximately maintains the timing.

The rate at which the fuel is injected into oil and Diesel engines is of extreme importance in its effect on smooth running and eiliciency. As is well known, this rate can be easily controlled for wide open throttle by properly designing the pump cam but the rate so obtained may be and usually is wrong for the lower range of throttle settings. By my invention I am able to use the cam designed to give maximum eiliciency at full throttle for all rangesl of throttle settings. I accomplish this by providing simple means for displacing the cam shaft from the line of motion of the cam follower which acts on the pump piston. The preferred path of displacement is such that altho the effective stroke is decreased the rate of fuel injection is increased, thus compensating for any bad effect the fixed cam shape may have at lower throttle openings.

In the drawings:

Figure 1 is a' view of the pump looking at it from the control end.

Figure 2 is a longitudinal vertical section taken on line 2--2 of Figure l.

Figure 3 is a transverse vertical section taken on line 3-3 of Figure 2.

Figures 4, 5, 6 and 'l are diagrams showing the control set respectively at full throttle, half throttle, idling and stopped.

Figure 8 is a diagrammatic view showing my improved pump connected to an engine.

The fuel injection pump shown in Figures 1, 2 and 3 used to illustrate my invention consists of a plurality of plungers Il) reciprocably mounted in bores I2 in a cylinder block i4 bolted as at I6 to the top of a cam shaft and tappet casting or housing i8. Springs 20 keep the base of the plungers in contact with the adjustable ends of roller tappet units 22 and thus keep the rollers 24 of these units in contact with the cams 26 on the cam shaft 28 which shaft is mounted in the end walls 30 of the cam chamber 3| in the lower part of the casting i8 in a novel manner to be described farther on. The tappet chamber 32 is provided with a removable cover 34 to permit inspection and adjustment of the tappet units and piston springs.

Thus far the pump is in general no different from the usual well known constant feed, constant stroke pumps of this type. The preferred form of my invention is obtained by providing the novel bearing unit 36 which carries the f bearings 38 of the cam shaft. The unit consists of two circular members 40 rigidly secured together as by the bar t2 whereby they may be turned as one in the circular openings or jour. nals M in the end Walls 30, or by removal of caps 46 and 4W the unit and cam shaft may be bodily removed from the casting.

The bearings 38 are eccentrically mounted in the circular members 40 whereby, as the unit is turned by means of the lever or, governor arm 48, the relation of the cam shaft to the tappet rollers is changed as will be clearly understood by reference to Figures 4 to 7. This causes a change in the clearance of the piston heads, or, what in effect amounts to the same thing, it causes a change in the effective stroke of the pump since the effective stroke is measured by the distance between the highest position of the plunger end and the top of the fuel inlet port Sil. Each of the inlet ports 50 communicates with a common bore 52 which may be provided with a shut-off valve 54 at one end and a connection 55 at the other end for connection with a supply pipe not shown. Each pump outlet p ort 56 is provided with means 5l for connecting with a conduit 58 for carrying the fuel charges to the respective engine cylinders in the usual manner.

The cam shaft 28 may be driven from the engine crank shaft in any manner which permits unimpeded rotation of the bearing unit 36, the only requirement being that the connections used be positive so that the gear ratio between the engine and the cam shaft is maintained. One method of driving the cam shaft is shown diagrammatically in Figure 8 in which the crank shaft 60 of the engine 6i is connected for exam- K,

ple, by a chain $2 to drive a shaft ll of the reduction gear unit 64 mounted on the engine. The gear unit is connected to one end of the cam shaft 28 thru a relatively long shaft C! with one or more universal joints 66 and 61. I do ,not wish to be limited to any specific manner of driving the pump and give this merely as an example. pump may be .applied to almost any type of oil or Diesel engine and, of course, its specific drive will depend upon the design of engine on which it is installed.

The operation of the pump control will be easily' understood by reference to Figures 4 to 7. 'I'he arrow 68 shows the direction of rotation of the cam shaft and the arrow 69 shows the direction of rotation of the bearing or control unit from a point of full throttle as illustrated in Figure 4 to a point of stop as illustrated in Figure 7.

At full throttle (Figure 4) the cam shaft axis, the bearing unit axis and the piston axes al1/lie in the same plane with the result that the effective stroke oi' the pump is at a maximum. Now moving the governor arm 48 in the direction of arrow 69 the effective stroke of the pump is decreased to about half when the arm has moved about 45 (Figure 5) and nearly a minimum when the arm has moved approximately 60 (Figure 6) and finally to zero as the arm reaches between 70 and 80 depending on the design of the parts. Incidentally it will be ,apparent to those skilled in the art that the governor arm 48 may be connected to be moved by the engine governor or by a foot or hand throttle lever or by a combination of these as desired.

Astudy of Figures 4 to 'I will show that three objects result from my extremely simple control.

First, I regulate the quantity of the fuel charge injected per stroke. Second, I regulate the rate of the injection of each fuel charge and, third,

I substantially maintain the timing of the injections. The regulation of the quantity or size of the fuel charge will be obvious but the regulation of the rate of injection and the approximate maintenance of the timing are not easily appreciated and will therefore be explained.

To illustrate, let us assume the quantity lof fuel injected into the engine at full throttle, i. e., at maximum effective stroke (Figure 4) to be, for example, three drops. Assume further that the cam is so shaped that the rst drop is injected in ten degrees of cam shaft rotation, the second in ten degrees of rotation and the last drop in ten degrees of rotation, under which condition the rate of injection is constant. Now assume that the cam is dropped in a straight line (so as not to move out of the center line 1I of the tappet, Figure 4) until the effective stroke is onethird that at full throttle, i. e., the pump will inject orie drop per stroke. Altho the size of the charge has been reduced the rate of injection has not been changed since the entire eective stroke will take place in the last 10 of cam shaft rotation exactly the same as the last third of the effective stroke at full throttle. The rate of injection, namely,.ten degrees per drop, has not been changed by the vertical displacement of the cam shaft in the straight line 1I. Since the pump piston stroke per degree of cam shaft rotation has not been affected through the throttle range, the rate of fuel injection remains constant and depends solely upon the shape of the cam.

A substantially vertical movement oi. the cam shaft could be obtained by locating the axis of It will be quite obvious that my improved f the bearing unit laterally of and in a plane normal to the piston axis at one-half throttle.

Now instead of dropping the cam shaft straight down assume it to be moved in a lateral path, such. for example, as the arcuate path 12, Figures 4 to 7, and in the direction indicated by the arrow 69, until the effective stroke is one-third maximum at which point the charge is one drop. From a study of the cam action it will be apparent that the speed of the pump piston per degree of cam shaft rotation is appreciably increased by the lateral displacement of the cam shaft from the center line of thev tappet. 'I'hus f` the slower the engine turns over, due to decrease in fuel charge, the faster the reduced charge is injected in fewer degrees of cam shaft rotation than one drop of the maximum charge.

'Ihe timing loss due to the dropping of the cam shaft is partly compensated for by the cam being displaced laterally from the center line of the tappet, which makes the cam engage the roller as many degrees sooner as was lost by the effective plunger stroke due to the drop of the cam shaft.

Thus it will be seen that by my invention I have provided an extremely simple control for simultaneously reducing the fuel charge and increasing the rate `of fuel injection while at the same time maintaining the timing not far from constant. It will also be seen that I eliminate the usual series of gears and levers and that all the elements employed such as bearings and bearing supports are solids of rotation thus not only reducing the cost of production to a minimum but also reducing the possibility of non-uniform wear and making possible very accurate machining, setting and adjustment.

The eccentric mounting of the cam shaft bearings in a rotatable bearing unit is the preferred embodiment of my invention but I do not wish to be limited to this specific construction since a little study will show that the invention in its broadest aspects may be carried out in an infinite number of Ways as, for example, replacing the arcuate path 'l2 by a path of any desired shape including straight lines (innite eccentricity) at any desired angle to the line of motion of the tappet. It will also be apparent to those skilled kin this art that for any given engine the design of the cam will depend on the shape and direction of the path of cam shaft displacement chosen. Or for any given cam and engine the choice of the path of displacement will depend upon the kind of engine operation that may Y be desired.

What I claim is:

1. Afuel pump for Diesel engines comprising a housing having a cam shaft chamber and a tappet chamber above the cam shaft chamber, a horizontal wall between said chambers having vertical bores, a plurality of tappets in said bores and having adjustable upper ends, the upper wall for said tappet chamber having bores arranged coaxially of said tappet bores, a cylinder block removably but tlxedly secured to said housing and having cylinder bores located coaxially of said coaxially arranged bores, said cylinder bores having fuel inlet and outlet ports, pistons in said cylinder bores acting as slide valves to control said inlet ports and projecting into the tappet chamber for engaging the adjustable upper ends of said tappets, springs around the respective pistons for maintaining said engagement, said cam shaft chamber having a pair of alined bores in the end walls. bearing supports rotatably mounted in the alined bores, bearings eccentrically lcarried in the supports, means within the chamber rigidly connecting said supports together for maintaining the bearings in coaxial relation and for .rotating the supports as a unit, a cam shaft in said bearings and having cams for engaging the tappets, means for preventing axial movement of the cam shaft, said preventing means being removable for permitting the removal and insertion of the supports and cam shaft as a single unit, said tappet chamber having a removable side wall for permitting access to adjust said tappets and for moving the tappets to clear the cams during the insertion or removal of said cam shaft unit.

2. A fuel pump for Diesel engines comprising a housing having a wall separating the interior intoa cam shaft chamber and a tappet chamber, said wall having tappet bores therein, a plurality of tappets in said bores, a cylinder block xedly secured to said housing and having cylinder bores located coaxially of said tappet bores, said cylinder bores having fuel inlet and outlet ports, pistons in said cylinder bores acting as slide valves to control said inlet ports, and projecting into the tappet chamber for operatively engaging said tappets, springs 4associated with the respective pistons for maintaining said engagement, said cam shaft chamber having a pair of alined bores in the"end walls, bearing supports rotatably mounted in said alined bores, bearings eccentrically carried in the supports, means rigidly connecting said supports together for maintaining the bearings in coaxial relation 'Xx' and providing for rotation of the supports as a unit, a cam shaft in said bearings and having cams operatively engaging the tappets, and means preventing axial movement of said unit, said preventing means being removable for permitting the removal and insertion of said supports with the cam shaft through one of said alined bores as a single unit.

3. A fuel pump for Diesel engines comprising a housing having a horizontal wall separating the interior into a cam vshaft chamber and a tappet chamber, said wall having vertical tappet bores therein, a plurality of tappets in said bores, a cylinder block removably but ilxedly secured to said housing and having cyllnderbores located coaxially of said tappetbores, said cylinder bores having fuel inlet and outlet ports, spring pressed pistons in said cylinder bores acting as slide valves to control said inlet ports, and projecting into the tappet chamber for operatively engaging said tappets, said cam shaft chamber having a pair of alined bores in the end walls, bearing supports rotatably mounted in said alined bores, bearings eccentrically carried in the supports, means rigidly connecting said supports together for maintaining the bearings in coaxial relation and for rotating the supports as a unit, a cam shaft in said bearings and having cams operatively engaging the tappets, and means preventing axial movement of said supports and the cam shaft carried thereby, said preventing means being removable for permitting the removal and insertion of said supports and cam shaft through either one of said alined bores as a single unit. 4. A fuel injection pump for oil engines comprising a cylinder block having a pump bore and a cam chamber, said bore having fuel inlet and outlet ports, rigidly connected bearing supports rotatably mounted in two opposite walls of said chamber, bearings eccentrically mounted in said supports, a cam shaft carried in said bearings,

a cam on said shaft, a piston in said bore opera'tively associated with said cam, and acting as a slide valve for said fuel inlet port, said cam shaft, shaft bearings and bearing supports being inclosed in said chamber thereby being free from dust and dirt, said cam shaft being positioned between the piston and the support axis at maximum e'ective stroke, vvwhereby when the cam shaft is in said maximum stroke position the cam shaft axis and support axis are both intersected by an extension of the piston axis, and means connected to said bearing supports for rotating lsaid supports any desired number of degrees in a predetermined range of approximately 75 from said maximum effective stroke position, so that as the cam shaft starts toshift from said position its motion is substantially all lateral and its vertical component of motion is substantially zero but as the shaft approaches its no load position at the end o! said range of 75 its lateral component of motion is of negligible value while said vertical component approaches the value the lateral component had at maximum effective stroke position.

' FRANK KOVACH.