US1949789A

US1949789A - Fuel pump for diesel engines

Info

Publication number: US1949789A
Application number: US522458A
Authority: US
Inventors: Dussmann August
Original assignee: Individual
Current assignee: Individual
Priority date: 1930-07-16
Filing date: 1931-03-13
Publication date: 1934-03-06
Anticipated expiration: 1951-03-06

Description

March 6, 1934. A. DUSSMANN FUEL PUMP FOR DIESEL ENGINES Filed March 13, 1931 "Ann Il/I/I/I/ I .70 ran for.

Patented Mar. 6, 1934 UNITED STAT-ES FUEL PUMP FOR DIESEL ENGINES August Dussmann, Aschaflenburg, Germany Application March 13,

1931, Serifl No. 522,458

In Germany July 16, 1930 2 Claims.

In the case of the Diesel engines with injected air, the atomization of the fuel and also the regulation of the quantity, especially in engines with large variations of speed, can be obtained comparatively more reliably than in compressorless engines. However, the complicated arrangements for producing the injection air require expensive plants. The Diesel engine with pressure injection is much more simple and just as reliable when the following conditions are fulfilled:

1. The control of the fuel pump must, if possible, act so that the commencement of the injection always occurs at the same time, the, end of the injection occurring however, earlier or later according to the load. This problem is mostly solved by separately controlled closing elements, rotary valves or slides, which however results in complicated constructions with high back pressure on the regulator.

According to the invention, uniform commencement of the injection is obtained, with a simple regulation of the quantity of fuel, in that thepump plunger is turned so that the pressure chamber is connected sooner or later with the suction chamber of the pump by means of the bores provided in the plunger.

2. The spring-loaded shutting off element in front of the nozzle, since it wears out quickly, should if possible be avoided and replaced by a simple open nozzle. However, the fuel jet must then be forced through the nozzle at the greatest possible speed. This is effected according to the invention in that the feed stroke of the pump does not begin at the commencement of the cam incline but at the middle, when the pump plunger has already attained a high spee 3. In the case of engines, especially vehicle engines, which are subject to great variations of speed and load, the speed of the pump plunger must always remain uniform. independently of the running speed of the engine, so that the atomizing occurs in uniform quality also at low-. er speeds and when starting up the engine. This condition is fulfilled according to the invention in that the pump plunger is actuated not by a cam, the angular speed of which is dependent on the running speed of the engine, but by means of a medium capable of expansion, for example an ignitable mixture or compressed air.

Two embodiments of the fuel pump according to the invention for Diesel engines with pressure injection are illustrated by way of example in the accompanying drawing in which:-

Fig. 1 shows in vertical section a pump equipped with valve control.

Fig. 2 is a similar view of a modified form of construction.

The constructions illustrated in the drawing are characterized chiefly by the fact that the feed stroke of the fuel pump piston is effected jerklike by compressed air, which is sucked in and compressed by a separately arranged compressor.

The crank shaft 22, which is driven by the englne, actuates the compressor piston 24 through the connecting rod 23, which compressor reciprocates vertically, suction-tight, in the pump casing 25. In the lower dead centre position, the upper edge of the compressor piston 24 intersects with the lower edge of the air suction slot 26. The compressor cylinder 27 is filled with atmospheric air. This is compressed after the compressor piston 24 has passed the suction slot 26. Shortly before reaching the upper dead centre position, the compressor piston 24 pushes open the pressure valve 29 hitherto held closed by the spring 28. The compressed air flows into the cylinder 30. A piston 31 moves in the cylinder 30. The force of the spring 28 is selected so that it separates the cylinder 27 from thecylinder 30 with the surface of the pressure valve 29 against the maximum pressure of the compressed air. If the valve 29 is pushed up by the piston 24, the compressed air acts on the considerably larger surface of the piston 31. Consequently this piston is driven upwards with a jerk like movement. The speed of the piston 31 depends chiefly upon the air pressure and on the counter pressure in the pump cylinder, which depends chiefly upon the crosssection of the nozzle. Consequently, the speed of the piston 31 is always uniform under the same conditions independently of the number of revolutions of the engine.

During the outward movement of the compressor piston 24, the compressed air in the cylinder 30 returns through the suction valve 32 into the pump cylinder 27, a portion of the work expended for the compression being recuperated. The air losses due to leakages may be made good through air sucked in through the suction slot 26 in the lower dead centre position. The spring 28 forces the piston 31 back on to the pressure valve 29, and the suction valve 32 also closes, when the compressor piston 24 has passed the suction slot 26 on the inward movement.

The fuel pump plunger 6 is mounted on the piston 31 and is moved during the suction stroke by the washer 7 in a similar manner to that in the cam pump. The regulation of the quantity of fuel is also effected by turning the pump plunger 6, whereby the pump pressure chamber is connected earlier or later with the suction chamber.

In the case of pumps for small engines the valve control of the compressed air presents a complication which could cause trouble owing to the delicacy of the valve packings.

Fig. 2 shows the pump with simple slot control, with which exactly the same effect is obtained as with the pump illustrated in Fig. 1.

The piston 33 is also actuated by a crank drive. In the lower dead centre, atmospheric air enters through the suction slot 34 into the compressor cylinder 35. The running surface has an overflow slot 36, which connects the compressor cylinder 35 to the cylinder 37. The piston 33 has a U-shaped cross section 38. A piston cavity is thereby formed, in which a cylinder cover 39 fits. The piston 33 has a slot 40 which registers with the suction slot 34 in the lower dead centre and with the overflow slot 36 in the upper dead centre. The air sucked through the suction slot 34 is therefore compressed, and only on attaining the maximum pressure suddenly flows through the overflow slot 36 into the cylinder 37 in which the piston 41 moves.

The connection of the pump plunger 6 and the adjustment of the quantity of fuel are effected in the same manner as in the pump according to Fig. 1.

I claim:-

1. A fuel pump for Diesel engines with pressure injection with an air compressor for producing compressed air for actuating the pump, comprising in combination with the compressor cylinder, a compressor piston adapted to suck in and compress air, a valve adapted to open and allow the passage of the compressed air towards the end of the compressing stroke at the highest air pressure, a further cylinder spacially separated from said compressor cylinder adapted to suddenly receive the compressed air through said valve, a piston in said separate cylinder adapted to be moved ata high speed by the air suddenly entering said separate cylinder, an injection pump fixed on said last mentioned piston, and a nozzle adapted to inject the sucked in fuel under pressure.

2. A fuel pump for Diesel engines with pressure injection, comprising in combination with the pump piston, a compressor adapted to supply air for driving the fuel pump, a piston for said compressor of U-shaped section having a slot leading from the cavity to the running surface of said piston compressor, a cylinder cover adapted to project into the cavity formed in said piston, a wall of said compressor cylinder having a suction and an overflow slot, and a compartment communicating with said cylinder through said overflow slot, the slots in said cylinder wall adapted to be controlled by the slot in said piston, so that the compressed air suddenly strikes against the pump piston only on the maximum pressure being reached.

AUGUST DUSSMANN.