US2589505A

US2589505A - Pump injector for oil engines

Info

Publication number: US2589505A
Application number: US778776A
Authority: US
Inventors: Morris Alberto Jorge
Original assignee: Lister & Co Ltd R A
Current assignee: RA Lister and Co Ltd
Priority date: 1946-09-11
Filing date: 1947-10-09
Publication date: 1952-03-18
Anticipated expiration: 1969-03-18

Description

Ma 1952 A. .1. MORRIS 2,539,505

PUMP INJECTOR FOR OIL ENGINES Filed Oct. 9, 1947 v 5 Sheets-Sheet l II i 10 19. l 4% 5a '16 INVENTOR. ALBERTO JORGE MORRIS March 18, 1952 A. J. MORRIS PUMP INJECTOR FOR OIL ENGINES 5 Sheets-Sheet 2 Filed Oct. 9, 1947 INVENTOR ALBERTO JORGE MORRIS 641A Mia/Z 1 00 7 J 3% 0 M 5 w l w&%5o 8 X y O #1 7 i f f 4 1 HHHHHI IHHHHI I MHIHHHH HHF O W V F "AA: 9 r 4% /7 7 NW fi fi W W/ a V 1 I W 4 1 g fi March 18, 1952 MORRJS 2,589,505

PUMP INJECTOR FOR OIL ENGINES Filed Oct. 9, 1947 3 Sheets-Sheet 3 Patented Mar. 18 1952 UNITED STATE S PATENT OFFIQE PUMP INJECTOR FOR OIL ENGINES Alberto Jorge Morris,-Dursley, England; assign'or to R. A. Lister & Company Limited, Dursley, England, a British company Application October 9, 1947-, Serial No. 778,776 In Great- Britain September 11, 1946 11 Claims.

This invention relates to pump-injectors for oil-engines comprising a plunger which reciprocates to deliver fuel from a cylinder to a nozzle by which the fuel is injected into the engine combustion space. The plunger makes a fuel-delivery stroke during which fuel injection occurs and a return stroke during which the cylinder is recharged with fuel.

This invention-has for an object to provide an improved construction of such pump-injector which is compact and is less liable to damage of the movingparts at the end'of a stroke.

According to this invention, a pump-injector comprises an injector body, a reciprocating plunger working in a cylinder in the body to deliver fuel intermittently to a nozzle provided at one end of the pump'inject'or, a spring-loaded gas-piston arranged to work in a chamber in the body under control of av pressure medium supplied to the chamber, said gas-piston and plunger being operatively connected to move as one piece, and means to provide a cushioning buffer to arrest the plunger and gas-piston at the end of a stroke.

According to one feature of this invention, means constituting a cushioning buffer at the end of the return stroke comprises a tapered extension of the gas-piston arranged progressively to decr'e'ase the effective area of a metering orifice through which-the pressure medium flows and thereby to control the flowof the pressure medium from the chamber. It will be seen that in use the tapered extension throttles the flow of pressure medium from the chamber onthe return stroke thus slowing down the moving parts and preventing damage there to. The extension is preferably given a taper of between 1 in 16 and 1 in 4. Such an arrangement has the further'advantage that as the pressure in the chamber increases during the fuel injection stroke the degree of throttling'decreases so that a quicker injection is obtained than if the metering orifice were of uniform effective area throughout the stroke.

It is preferred moreover that the metering orifice has an effective area when the piston is at the end of the return stroke equal to between about 0.5% and 2% ofthe cross-sectional area of the gas-piston in order that satisfactory cushioning and communication with pressure 'medium' supply is obtained and in order to avoid the necessity of providing an auxiliarycontrol to reduce the spring loading on the gas -piston for starting purposes.

It has also been found that the volume of the gas-piston chamber with the piston at the end ofthe return stroke has a controlling effect on the t'emp'er'at'ure of the gases within the chamber. on the rate of lift of the gas-piston andthere'fore of the injection plunger and on the cushioning effect secured at the end of the return stroke. According to a further feature of the invention therefore, the volume of the gas-piston cham-' her when the gas piston'i's at the end of the r'e-" turn stroke is selected to be within the range of from 5% to of a' volume equivalent to'the cross-sectional area of the gas-chamber niulti plied by the stroke of the gas-piston. Conveniently, the metering orificeopens to that end of the pump-injector at which the nozzle'is located and the nozzle is" carried by the" tapered extension so that the pressure medium for controlling the gas-piston is con'stituted' by the gases in the combustion space to'whi'ch' fuel is supplied. In such a construction it is preferred that the volume of the gas-chamber when the pistonis'at the end of the return stroke be selected'to benot more than 5% of the volume'of the engine corn bustion space, which volume is calculated with the engine piston at top dead centre, to'which fuel is being supplied. If the chamber volume'is too large the' operation of the e'hg'ineis adversely may. be varied. In this manner the quantity of fuel injected and the point in the engine cycle at which injection commences may be varied; The? plunger preferably hasa shaped'stem'which pro-- vides during fuel injection communication between portions of a ductleading from the cylinder to the nozzle and which is adapted to ope'nthe' duct to a spill port to terminate fuel injection prior to'the'end'of the fuel injection stroke'and thereafter to cut off that portion of the duct opening to the cylinder from the'spill port and that portion of the duct leading to the nozzle thereby to entrap fuel in the cylinder.

According to yet another feature of this inveri tion, a spring-loadedvalveis providedcontrolling the flow of' fuel in the duct and means is pro- Vlded fOi Varying theloading Of' the valve there y t Liointat whichfu'el injection commences. t

In order to facilitate manufacture, it is preferred that the gas-piston and plunger be made as one.

A pump-injector embodying the features of this invention will now be described by way of example, reference being had to the accompanying drawings in which:

Figure l is an elevation of the pump-injector,

Figure 2 is a longitudinal section on a larger scale.

Figures 3 to '7 are diagrammatic figures illustrating the operation of the plunger and,

Figure 8 illustrates a modification.

Referring to Figures 1 and 2, the pump-injector comprises a body I9 accommodating in its upper portion (as viewed in the drawings) a fuel-pump and in its lower portion the means for actuating the pump. In this manner, the upper portion is cooledby the incoming fuel. 1.0,there is secured a distance piece H providing an. abutment for a spring 12 which bears on a gas-piston l3 working in a chamber :4 constituted by the wall of the body Hi and a nut l screwed into the end of the body. The nut is formedwith a central orifice 15a through which projects a tapered extension [6 of the piston l3 carrying atrits outer end an injection nozzle ll. A, duct I8 runs through the extension i6 so that fuel may be supplied to the nozzle from the pump, the plunger, IQ of which is formed as an axial extension of the gas-piston l3. A guide pin is provided between the skirt of gas-piston l3 andthe stem of the piston to engage in-a slot 21 in an extension 22 of the distance piece to pre- Vent rotation of the gas-piston and plunger in use. I

A resilient pad 23 is located in the space between the gas-piston skirt and stem as emergency means for stopping the moving parts and preventing damage thereto.

The. pump injector illustrated is of a construction adapted for operation by the pressure within the combustion space to which fuel is being supplied.

Referring to the gas-piston l3 and chamber I4,

it, has been found that for the most efiicient operation the dimensions of the parts must be carefully selected. j Thus, for example, to secure eflicient cushioning of the moving parts at the end of the return stroke and atthe same time toensure effective communication between the chamber [4 and the compression space under all running conditions, it has been found that when the gas-piston i3 is at the end of the return stroke (i. e. in a position with its under surface bearing against the shoulder 45 provided by nut 15) its effective area should be selected to be from about 0.5% to about 2% ofthe cross-sectional area of the piston. By so selecting the area of the orifice, it becomes unnecessary to provide an auxiliary control to relieve the loadingof spring 42 for starting purposes.

Moreover, it is preferable to arrange that the area of the orifice I511. increases during the fuelinjectionv stroke. In this manner the pressure within chamber [4 rises sharply at the injection period giving improved injection. For this purpose it has been found that best results are secured if the tapered extension has a taper of between 1 in 16 and l in 4. If the orifice has a uniform cross-section throughout the injection stroke, the characteristic pressure curve for chamber M is a replica of the engine compression curve, the slope of which normally decreases as Within the body the engine reaches top-dead centre. Such a characteristic pressure curve would prevent quick fuel injection.

It has also been found that the volume of the gas-piston chamber with the piston at the end of the return stroke has. a controlling effect on the temperature of the gases within the chamber, on the rate of lift of the gas-piston and therefore of the injector-plunger and on the cushioning effect secured at the end of the return stroke. According to a further feature of the invention therefore, the volume of the gas-piston chamber when the gas piston is at the end of the return stroke is selected to be within the range of from 5% to 60% of a volume equivalent to the crosssectional area of the gas-chamber multiplied by the stroke of the gas-piston.

It has also been found that if the volume of the gas-chamber. I l (withthe gas-piston at the end of the return stroke). is too large, the engine operation may be affected and therefore it is preferred that the volume be limited to not more.

than 5% of the volume of the engine combustion space, which volume is calculated when the engine piston is at top dead centre.

Between the distance piece H. anda threaded collar 29, there is located a sleeve 24 having lands 25 for positioning the sleeve within the body HIV and ports 26 providing communication between a fuel-delivery connection 2! and a chamber 28 formed in the inner surfaceofthe sleeve.

Within the sleeve 24, there is located a cylinder 30 in which the plunger i9 works, and this cylinder is rotatable by means of a lever B! secured to a head 32 which is pinned to the cylinder 30 at 33. A nut,34 is threaded on the outside of the cylinder 30 and head 32 and bears on sleeve 24 to hold a flange 35 on the cylinder against the sleeve. A fuel inlet port 36 is provided connecting chamber 28 with the cylinder space and a duct 31 is formed in the wall of the cylinder connecting the cylinder space 7 with the duct [8 through a shaped portion of the plunger. Spill ports 38 are also formed in the cylinder just below the level of the inlet port 36. A pump priming duct 39 is formed in the head 32 and is normally closed by plug 40. V

The plunger l9 which is an axial extension of the gas-piston 13, has a head with a helical edge Al. It will thus be seen that by rotating the cylinder 30,,the point in thefuel delivery stroke at which the inlet port 36 is covered may be varied. In this way the quantity of fuel delivered to the nozzle and the injection time may be varied. The duct I8 communicates at its upper end with a cross duct 42 opening to a neck 43 formed in the stem of the plunger 19..

The operation of the pump injector is as follows:

With the gas-piston I3 and plunger i9 at the end of the return stroke and therefore at the beginning of the fuel injection stroke, pressure within chamber I4 will slowly rise with the pressure in the combustion space until the loading spring [2 is overcome. The piston l3 and plunger [9 will then commence the injection-stroke, the plunger moving from the. position shown in Figure 3 until the helical edge. 4| of the plunger head covers the inlet port 36 (Figure 4) at which point fuel injection commences, fuel being forced through duct 37, port 41, around neck 43, and

7 through cross duct 42,.duct l8 pastball valves 48 v thus relieving the pressure within the ducts l8, 3'! and in the cylinder.

On further upward movement of the gas-piston and plunger the lower lip of the. neck closes port 41 (Figure 6) so that fuel is trapped within the cylinder and duct 3] and provides a hydraulic cushioning buffer for the end of the fuel-injection stroke. In this way damage to the moving parts by violent contact is avoided.

In the event that'the cylinder is empty the moving parts are stopped by contact of the resilient pad 23 with the end of the sleeve-like extension 49 of the distance-piece H.

The parts are now. at the beginning of the return stroke.

As the pressure within the combustion space decreases gases escape from chamber I4 through the metering orifice I504, the effective area of which is gradually decreased so as to throttle the flow of gases thus allowing the. moving partsat the end of the return stroke to be stopped gently against abutment 45.

During the return stroke a vacuum will form in the cylinder, and fuel will be drawn into it through port 36 and also partly through spill port 38 and duct 31 until the former is closed in the head of the plunger.

For starting purposes, the cylinder may be .primed by loosening the plug 40 and injecting fuel through inlet port 36 by a gravity or pressure feed allowing air to escape through duct 39.

Figure '7 illustrates the position of the cylinder 30 inwhich no fuel will be injected since the helical edge does not cover the inlet port 36 until the spill port 38 is uncovered.

It will be appreciated from the foregoing that the invention provides asimple compact construction of pump injector in which the possibility of damage to the moving parts is considerably reduced by providing a hydraulic cushioning buffer at the end of the fuel-injection stroke and a throttled gas flow to control the return stroke. Moreover, by suitably selecting the dimensions of various parts of the pump injector, efficient fuel injection is obtained and adverse effects on the engine operation are avoided.

Referring now to Figure 8, in which reference numerals used in Figure 2 are employed to indicate like parts, there is illustrated auxiliary means for varying the point in the fuel injection stroke at which fuel injection commences. The auxiliary means comprises a needle valve 50 having an enlarged stem 5i and mounted within the head 3'2. The needle valve 50 is normally urged into contact with a seat providing an outlet port 52 between the cylinder and duct 31 by means of a loading spring 53 the loading afforded by which may be varied by abutment screw 54. With this arrangement fuel cannot be delivered to the nozzle until the pressure in the cylinder is sufficient to overcome the spring 53. When the valve 5!) is clear of the port 52, the fuel pressure acts on the end of the enlarged stem 5| ensuring rapid lifting of the valve.

I claim:

1. A pump-injector comprising a body, a bore the body to form a gas chamber having port means for the supply to the chamber of a pressure fluid; a fuel pump cylinder accompanied in the body coaxially with the gas chamber, there being a fuel inlet port to the fuel pump cylinder; a fuel injection nozzle at one end of the pump injector, there being fuel-delivery duct means interconnecting the fuel pump cylinder and the fuel injection nozzle; a reciprocating member reeiprocable. within the. body under. control: of the pressure fluid in the gas: chamber and: having a gas piston portion working in the gas chamber. a. fuel pump plunger portion having ahead working in the fuel pump cylinder, a stem. connecting the head to the gas piston, and a tapered extension projecting from the gas. piston portion and ex.- tending through the port means of the gas chamber to throttle the flow ofpressure fluid through the port. means, the taper of said tapered extension being arranged progressively to increasethe effective area of the'port meansduring travel of the reciprocating. member to. increase thepressure fluid receiving volume of said gas chamberto deliver fuel to. the injection nozzle and progressively to decrease said effective area during the return travel of the reciprocating: member to decrease said pressure fluid receiving volume, and said stem having a part arranged as a valve to control the fuel flowv through the duct means to cut off the fuel flow prior to the endof. the fuel injection stroke and to entrap fuel in the fuel pump cylinder; and a return spring actingv to urge thereciprocating member in. the direction of the return travel.

2. A pump-injector as claimed in claim 1', wherein said taperedextension has a taper of between 1 in 16 to 1 in 4.

3. A pump-injector as claimed: in' claim 1, wherein said port means; of the gas chamber and said tapered extension are.arranged,.when the reciprocating member is at the end. of its. return travel, to give a value of said effective area of between 0.5% and about.2.% of the cross-sectional area of said gas piston.

4. A pump-injector. as claimed in claim 1, wherein said gas chamber and'saidgas piston are arranged, when the piston is atthe end of its re.- turn travel, to give a pressure fluid receiving volume of said gas chamber within the range. of from 5% to 60% of a volume. equivalent to the cross-sectional area of the gas piston multiplied by the stroke of the gas piston.

5. A: pump-injector as claimed in claim 1, wherein said fuel injection nozzle is carried at the outer end of the tapered extension, the duct means interconnecting the fuel pump cylinder and the fuel injection nozzle comprises duct portions in the pump cylinder and in the stem of the pump plunger, and said stem of the pump plunger has a waisted portion arranged during fuel injection to connect the duct portion in the fuel pump cylinder with the duct portion in the stem of the fuel pump plunger and arranged before the end of the fuel injection travel of the reciprocating member to be moved to brake said connection between said duct portions and to prevent fuel flow through said duct portion in the pump cylinder thereby to entrap fuel in the fuel pump cylinder.

6. A pump-injector as claimed in claim 5, wherein said fuel pump cylinder also comprises a spill port therein, which spill port is arranged to be uncovered by said waisted portion of the stem to terminate fuel injection just prior to the point in the fuel injection travel at which the connection between the duct portions is broken.

7. A pump-injector comprising a body, a bore in the body to form a gas chamber having port means for the supply to the gas chamber of a pressure fluid; a fuel pump cylinder accommodated in the body coaxially with the gas chamber and arranged for angular adjustment about its axis, there being a fuel inlet port to the fuel pump cylinder and a fuel outlet port therefrom and a duct portionin the pump cylinder connected with, the outlet port, means to rotate the fuel pump cylinder within the body to adjust its angular position therein; a member reciprocable within the body under control of the pressure fluid in the gas chamber and having a gas piston portion Working within said gas chamber, a fuel pump plunger portion having a head Working in the fuel pump cylinder and a stem connecting the head to the gas piston, said head having a portion shaped to co-operate with the inlet port to determine, accordingto the angular position of the pump cylinder within the body, the pointat which fuel injection commences, and a tapered extension projecting from the gas piston portion and arranged to extend through the port means of the gas chamber to throttle the flow of pressure fluid through said port means, the taper of said tapered portion being arranged so as progressively to increase the efiective area of the port means throughout travel of the reciprocating member to increase the pressure fluid receiving volume of said gas chamber and to deliver fuel from the fuel pump cylinder and progressively to decrease the effective area throughout the return travel of the reciprocating member to decrease said pressure fluid receiving volume of said gas chamber, there being a duct portion running through said stem and said tapered extension, and said stem having a waisted portion to provide communication between the duct portion in the fuel pump cylinder and the duct portion in the stem and tapered extension during fuel injection, said waisted portion being so located along the stem that communication between the duct portions is cut oil prior to the end of the travel of the reciprocating member in the fuel injection direction; a fuel injection nozzle carried on the free end of said tapered extension and communicating with the duct portion in the stem and tapered extension; and a return spring to effect travel of the reciprocating member in the return direction.

8. A pump-injector as claimed in claim 7,

wherein said tapered extension has a taper of between 1 in 16 to 1 in 4.

9. A pump-injector as claimed in claim '7, wherein said port means of the gas chamber and said tapered extension are arranged, when the reciprocating member is at the end of its return travel, to give a value of said effective area of between 0.5% and about 2% of the cross-sectional area of said gas piston.

10. A pump-injector as claimed in claim '7, wherein said gas chamber and said gas piston are arranged, when said gas piston is at the end of its return travel, to give a pressure fluid receiving volume within the range of from 5% to of a volume equivalent to the cross-sectional area of the gas piston multiplied by the stroke of the gas piston.

11. A pump-injector as claimed in claim 7 wherein the fuel pump cylinder is also provided with a spill port in such a position in its length that it is uncovered by the waisted portion of the stem to terminate fuel injection prior to cutting ofi of communication between the duct portion in the pump cylinder and the duct portion in the stem and tapered extension.

ALBERTO J ORGE MORRIS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Date