US1940510A - Fuel injecting device - Google Patents

Description

, Patented Dec. 19; 1933 PATENT OFFICE FUEL INJEC'IING DEVICE Alfred Ratellier-Parehet, Genoa, Italy Application July 2,1928, Serial No. 289,882, and

in Germany July 6, 192'! a 4 Claims. (Cl. 103-37) Motorsi with direct'injection of fuel, generally suifer from the drawback that the fuel-pump required for injecting the fuel is troublesome and v complicated in its construction as well as in its I mode of operation.

Control of the injecting-pump and its maintenance are the more difflcult, the smaller the fuel volume to be lifted and the greater the speeds of the motor. The employment of all kinds of pump valves prevents such a pump, with its accessories, from being operated by anybody. To

obtain a good combustion under all loads and speeds, the quantity of fuel to be injected has to be squirted'into the cylinder as rapidly as posli sible under high pressure, for which purpose so called accumulating pumps have been proposed. The construction of these however is still more complicated than that of ordinary injecting pumps and, consequently, they are absolutely unto suitable for untrained attendants. If valves of known fuel pumps leak, they must be re-ground and the controlling elements for operating the same-re-adjusted, which can only be done by trained hands. 28 been built, thepistons of which act as distributing-slide-valves, or special distributing elements have been installed in order to avoid the re-grinding of valves.

Such arrangements are however unsuitable for 30 pumps intended for pressures up to several hundred atmospheres. It must be considered that for small motors, often fractions of amillimeter piston stroke suflice for a single injection and that it is consequently extraordinarily diflicult 36 to effect a tight covering between piston edge and suction slot under such high pressure and a fraction of a millimeter covering surface and thus permanently obtain an exact injection.

These pumps have the further disadvantage,-

40 that the pump piston must be operated by a cam,

if the short injecting period required for highspeed motors is to be maintained, whereby a noisy running of the motor is produced.

All constructions are also subject to the common disadvantage that the injecting period and the injecting pressure are fixed by the control, the latter being only a function of the pump piston veloclty'and the nozzle cross-section. If the nozzle is stopped up care has to be taken by means of a safety-valve, that the fuel can escape. These safety-valves are a further source of interruption in working, as they often leak.

In high-speed vehicle motors with variable speed it is absolutely necessary to be ableto vary 65 the injecting period and the injecting pressure,

Pumps with suction slots have as well as the moment of injection during working- A fuel injecting device, in which the above disadvantages are avoided, and which corresponds with the requirements made upon a high-speed 00 motor is described below and is based upon the following principles:

In a pump cylinder with a suction slot and a delivery slot or slots, a driven piston is arranged adapted to close and to open said suction slot; a loaded counterpiston is arranged in the same cylinder and is adapted to close and to open said delivery slot or slots. Means are provided for bringing an additional load on the counterpiston approximately at the time the delivery slot or slots are uncovered by this piston. These means contain a contacting surface for the counterpiston and the distance between said surface and the upper end surface of the counterpiston is less than the distance between said delivery slot or slots and the lower end surface of said counterpiston. r

The subject of the invention is illustrated in the drawing by way of an example.

Fig. 1 is a central, longitudinal section of one embodiment of the invention for smaller capacities.

Fig. 2 is a partial section through another mode of construction for larger capacities.

In the pump cylinder 1, (Fig. 1) move two pistons 2 and 3. The pump cylinder 1 has below a suction slot 4 and above one or more superposed pressure slots 5, according to whether one or more nozzles are fed by the pump. The lower piston is moved up and down by any suitable means, according to the drawing e. g. by a crank pin 6. The piston 2 is below fitted with a crosshead-like guide 2. The piston 3 is moved down by some means, preferably according to the draw- The piston 3, forced down by the spring '7, rests ,upon a stop 12 adjustable as to height. The

height of this stop is adjusted by the regulator or by hand during working. It regulates the distance between the two pistons 2 and 3 in their lowermost position and consequently the quantity of fuel enclosed by the said pistons. Upon the spring plate 8, with the stop 10, rests the spring the piston 3.

13. The same is supported by the adjustable stop 14, so that the compression of the spring 13 can be varied by the adjustment device 15. The spring 16 on the cross-head, serves the purpose of preventing a knocking consequent on play, as the spring always effects a pressure in the same direction, thus preventing a change in pressure.

In pumps for greater capacities, locating the spring 13 would be connected with difiiculties. This spring is then replaced by a piston 20 serv ing as a stop, as illustrated in Fig. 2. This piston moves in the cylinder 21, the lower portion of which is designed as a valve seat 22. Above the piston 20,- in the chamber 23, an adjustable liquid or gas pressure prevails.

The mode of action is as follows:

Thepump according to Fig. 1 shows the two pistons 2 and 3 in their lowest position. The piston 2 has been drawn by crank pin 6 into its lowest position, the piston 3 has followed it, forced down by the spring 7, until it abuts against the stop 12, the height of which is adjustable. The smaller the quantity to be lifted by the pump, the lower is the stop 12, i. e. the later the piston 3 comes to a stop in its downward stroke. The lower piston 2 has opened the suction slot 4, in its lowermost position, so that the space between the two pistons is filled with fuel. The same preferably flows to the pump under very little pressure. If the piston 2 moves upwards consequent on rotation of the crank pin, the suction slot 4 will be closed. The fuel between the pistons 2 and 3 is very slightly compressed, until the liquid pressure acting upon the piston overcomes the pressure of the spring 7, so that the piston 3 likewise moves upwards. The piston 2 covers the suction passage 4 1 thus to any desired extent, so that a tight packing towards the suction passage of the enclosed liquid is effected.

The piston 2 simultaneously moves in the vicinity of the greatest piston velocity, 1. e. in the zone, where, under a given crank angle, the largest quantity of fuel can be displaced. As soon as the piston 3 contacts with its seat 9 against the stop 10, it is prevented from further movement, as the strong compression of the spring 13 has to be overcome. The liquid pressure between the two pistons rises immediately, until the spring tension-has been overcome and the piston 3 can once more move upwards. Simultaneously one or more pressure slots are opened thereby consecutively, so that the highly compressed liquid can flow towards the injecting nozzle or nozzles. Opening of the pressure slots can be effected previous to the stoppage of the piston movement, by The piston velocity of the piston 2 is advantageously chosen so great, that the same is sufflcient for injecting the smallest quantity of fuel in the desired shortest time under the desired lowest injecting pressure. If the quantity of fuel to be injected is greater, so that a larger crank angle is required for its injection, the piston 3 in the beginning moves upwards by overcoming the spring pressure of the spring 13. Injection of fuel is now effected, depending upon the nozzle cross-section, by the continued movement of the piston 2 and the spring pressure exerted upon the piston 3, so that a greater quantity of fuel is forced into the working cylinder during a longer period but under approximately the same pressure.

If the speed of the motor increases, .and the injection is to be effected within a shorter time under approximately equal crank angle, the compression of the spring 13.111115; be increased by means of the devices 14 and 15, which can be done during working. As the piston velocity of the piston 2 increases with the speed and the pressure upon the piston '3 under a given quantity of fuel has likewise increased consequent on increased spring tension, the injecting pressure must rise, viz. the absolute injecting period is shortened. If the reverse method is employed, injecting pressure and injecting period can be increased during working under reduced speed, as may be desired. It is possible to shape the combustion diagrams by external influence as desired, without having to effect a regulation of the cross-section. of the injecting elements.

This enables the obtaining of the most favourable consumption of fuel under any load and speed. If one nozzle is partly or entirely stopped-up, the injecting period only is increased, but an increase in pressure, whereby thepump is endangered, can never occur.

Regulation of the pump is most exact consequent on the large covering effected by the piston 2 relative to the suction slot.

Present pump constructions with suction slots change their regulating position under wear, as the piston, closing the suction slot and packing immediately upon high pressure, permits, consequent on a very slight wear, relatively large quantities of fuel to flow back into the suction passage. A creeping rise in pressure is thus produced at the commencement of the fuel injection and consequently a faulty combustion. The same takes place in present pumps at the end of the injection period. The fuel supply is interrupted by the most varied regulating methods by the opening of a regulating valve.

This opening is always effected creepingly and by strong tension of the nozzle pin spring; therefore care has to be taken, that dripping is prevented.

In the pump forming the subject of the present invention, the fuel supply is suddenly interrupted as soon as both pistons 2 and 3 strike together, and up to the last moment of injection, constant injecting presure prevails in the pressure pas- 120 sage.

If this fuel injection is to be employed for larger motors, the dimensions of the spring 13. according to Fig. 1, will be too large and this spring is consequently advantageously replaced 125 by a piston 20 (Fig. 2) subjected to 9. corresponding liquid, or gas pressure. The injecting pressure for the fuel is regulated by the pressure exerted upon the piston 20.

The pressure piston 20 moves in a cylinder 21, 130 the lower portion of which is designed as a valve seat 22, upon which the piston 20 rests like a valve and has a tight packing effect during the period in which it is in its position of rest.

According to the quantity of fuel to be lifted, the piston 20 is more or less lifted from its position of rest, influencing the injecting process in the same manner as the spring 13 according to Fig. 1. The pressure acting upon the piston 140 20 may be starting air, combustion air or a liquid under gas pressure.

valves requiring re-grinding. The pump, con- E50 sisting of two pistons only, can be installed even at an inaccessible part of the motor.

The same, or a similar device can be employed as any kind of liquid pump and anywhere where small quantities of liquid have to be lifted under high pressures, as for example lubricating pumps. In the latter it is often necessary to convey one drop of lubricating oil under high pressure at an absolutely certain moment to the point to be lubricated, viz. piston and piston rod, in order to obtain reliable and economical lubrication, which has hitherto been impossible with pumps of present constructions. The absence of any kind of valves adapts the pump to all those purposes in' which re-grinding of valves is impossible on account of the lack of proper attendance.

I claim as my invention:

1. In a fuel injecting device for internal combustion engines of the solid injection type, a pump cylinder with a suction slot and a delivery slot, a driven piston in said pump cylinder, said piston being adapted to close and to open said suction slot, a loaded counterpiston in, said pump cylinder, said counterpiston being adapted to close and to open said delivery slot, means for bringing an additional load on the counterpiston just before the delivery slot is uncovered by said piston, a contacting surface for the counterpiston on said means, the distance between said surface and the upper end surface of said counterpiston being less than the distance between said delivery slot and the lower end surface of said counterpiston when said counterpiston is at the end of its suction movement.

2. In a fuel injection device for internal combustion engines of the solid injection type. a; 'pump cylinder, a driven piston, and a loaded counterpiston in said pump cylinder, the driven piston being located opposite to the said counterpiston at a variable distance from it, forming a space for taking a quantity of fuel suitable for the load, a suction and a delivery slot for introducing and delivering the fuel, the distance between said slots being less than the stroke of the pump piston, means for bringing an additional load on said counterpiston, a stop on said means, the distance between said stop and said slots being variable, said stop being adapted to be moved by the counterpiston.

3. In a fuel injection device for internal combustion engines of the solid injection type, a pump cylinder, a driven piston, and a counterpiston in said pump cylinder, the driven piston being located opposite said counterpiston at a variable distance from it, forming space for taking a quantity of fuel suitable for the load, suction and delivery slots for introducing and delivering the fuel and being controlled by the piston and counterpiston respectively, the distance between said slots being less than the stroke of the pump piston, compounded loading means forforcing said counterpiston towards said driven piston, said loading means at all times cooperatively loading said counterpiston and being adapted to substantially increase the load on said counterpiston at certain positions of the latter, a stop on said means, the distance between said stop and said slots being variable, said stop being adapted to be moved by the counterpiston. 4. A fuel pump consisting substantially of a pump cylinder having a suction and a discharge opening, a driven piston reciprocating within said cylinder, said piston and counterpiston respectively controlling said suction and discharge openings, a plurality of resilient means arranged in series and forcing said counterpiston towards said driven piston, said resilient means at all times cooperatively loading said counterpiston,

and an adjustable stop for adjustably limiting ALFRED RATELLIER-PARCHET.

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