US2243011A - Injector for internal combustion engines - Google Patents

Description

Filed Dec. 23, 1958 2 Sheets-Sheet 1 May 20, 1941. P. LORANGE I INJECTOR FOR INTERNAL COMBUSTION ENGINES Filed Dec. 23, 1958 2 Sheets-Sheet 2 Patented May 20, 1941 INjE-CTOR ron INTERNAL COMBUSTION ENGINES Prosper LOrange, Stuttgart-Feuerbach, Germany; Rudolf LOrange executor of the estate of said Prosper LOrange, deceased Application December 23, 1938, Serial No. 247,528 In Germany June 24, 1938 9 Claims. (Cl. 299-1075) The invention relates to injectors for-internal combustion engines, and in particular to injectors of the needle-valve type.

Such injectors are opened by the pressure of the fuel acting on the tip of the spring-loaded valve needle above the seating thereof, the space above the upper or other end of the needle not being subjected to fuel under pressure. As oil always leaks to the space above the needle, it is necessary to provide a pipe for the withdrawal of oil from this space.

The spring by which the needle is forced upon its seat must be so strong that it is not compressed until a certain opening pressure, which is sometimes very high, has been attained. When the pump pressure ceases, the pressure exerted by the spring forces the needle on to its seat, which is of relatively small area.

Many designs of injectors have been proposed to cause the production of a small preliminary injection as early as possibl before the main imection.

The chief object of the invention is to furnish an injector in which fuel under pressur is present above the end of the needle remote from the nozzle, whereby the provision of a conduit for the removal of escaped oil is obviated.

Another object of the invention is to provide an injector in which a substantially weaker loading spring for the needle than that normally employed can be utilised, whereby the hammering action of the needle on its seat and the resulting wear are diminished.

A,. further object of the invention is the provision of an injector in which a preliminary fuel injection is efiected in a particularly advantagBO'llS manner.

The above and further objects of the invention will now be described with reference to the annexed drawings, in which Figure 1 represents a pressure diagram;

Figure 2 illustrates an axial section of an injector with an invariable throttling aperture;

Figure 3 is a similar view of an injector the throttling aperture of which is controlled by a valve; and

Figure 4 illustrates a further embodiment of the type of injector illustrated in Figure 3.

In the injector according to the invention the space above the end of the needle remote from the nozzle communicates with the fuel delivery pipe by means of only one or more apertures having a strong throttling action and with the combustion chamber through a fine calibre injection aperture, the needle being pressed on its valve seat by means of a spring, whereby'when fuel is forced-through the delivery pipe from the pump, the pressure set up in the said space becomes so much smaller than the pressure at the tip of the needle above the valve seat, that the force of the spring is overcome and the needle rises from its seat.

The needle is preferably axially bored for the flow of fuel therethrough to the injection aperture.

The injector may operate in the following. manner:

As soon as the pump pressure is set up in the delivery pipe, fuel flows through the throttling aperture or apertures into the space above the needle and then through the' axially bored needle and the fine calibre injection aperture at the tip thereof into the combustion chamber. The injection aperture is so dimensioned that only a fraction, for example one sixth, of the entire fuel charge is injected therethrough.

A drop in pressure of the fuel flowing through the throttling aperture or apertures and the injection aperture occurs. The pressure decreases at the injection aperture opening into the combustion chamber to the level of the counterpressure in the said combustion chamber, the fuel under pressure being sprayed into the cylinder.

At the throttling aperture or apertures between the delivery pipe and the space above the needle, the pressure drop can be so controlled by selection of the ratio of the throttling aperture to the injection aperture in the tip of the needle, that it amounts to a predetermined fraction of the pump pressure, for example to approximately 20 atmospheres in the case of a pump pressure of about atmospheres. The ratio of the pressures at a given instant will thus be approximately that indicated in the pressure diagram constituting Figure 1 of the accompanying drawings. The full pump pressure, or the pump pressure P1 reduced by the throttling in the delivery pipe obtains up to the throttling aperture or apertures between the said delivery pipe and the space above the needle.

After the fuel has passed throughthe throttling aperture it is reduced to a pressure P2, so that from this throttling aperture to the injection aperture at the tip of the needle the pressure P2 obtains, which then falls through the injection aperture to a pressure P3, which is substantially equal to the pressure in the combustion chamber.

As soon as the pressure difference P1-P2 has become so great that the spring load on the needle is less than the vertical component of the super-pressure exerted on the needle above the valve seat at'the tip thereof, the needle rises,

. the said needle closing again when the pressure in the pressure annular space surrounding the needle tip decreases. 'For a short time before the needle opens, only the jet from the injection aperture in th tip of the needle is sprayed into the combustion chamber and thus the desired preliminary injectionisattained. 7

When the needle closes, the pressure in the space above the needle will in any case decrease more rapidly than the pump pressure, since the needle, forced down by its spring, exerts a sucking action. This arrangement aifords the following advantages:

1. In contra-distinction to normal constructions, the danger of carbonisation at the nozzle due to a preliminary injection (preliminary dripping) does not occur, since any drips escaping before the main injection are carried away by the full jet later sprayed past from the needle nozzle, whilst the eflect 'of subsequent dripping is eliminated owing to the fact that the pressure falls more rapidly in the space above the needle than in the delivery pipe, and the spray through the injection aperture at the tip of the needle therefore ceases ,more rapidly than the spray through the nozzle.

2. As compared with the normal needle-valve type injector'the advantage is obtainedthat the conduit for the removal of escaped fuel is obviated.- The fuel penetrating past the needle is simply added to fuel entering through the throttling aperture.

3. The loading spring for the needle can be made very considerably smaller and weaker, for example one eighth as strong as the spring usually employed. In this manner, the heavy hammering of the needle on to its very narrow seat and the wear-thus produced are diminished.

4. The fuel is sprayed through the fine aperture in the tip of the needle somewhat earlier than the injection through the nozzle, and the preliminary ignition, which is generally very desirable, is thus efiected and shortens th usual delay in ignition.

5. In the case of an engine furnished with a pre-combustion chamber which has a conduit disposed opposite the injection nozzle extending to the main combustion chamber, it is possible to make the fine jet sprayed from the aperture in the tip of the needle penetrate through into the main chamber owing to the fact that it is particularly well guided, for example the length of the fine aperture may be four times greater than its diameter. This will be particularly advantageous for initiating the ignition if the air velocity in the conduit is not so high at the starting speed that the jet is blown back.

The pressure diiference P1Pa will vary with the fuel velocity in the delivery pipe, that is to say with the engine speed, and it may be desirable that this value, and consequently the needle opening pressure, should be. maintained constant.

This may be effected without difliculty if the throttling aperture is closed by a spring-leaded The difference in the manner of operation when a throttling aperture of invariable cross-section or one provided with a spring-loaded throttle valve is employed is as follows:

The needle opening pressure is reached more rapidly in the former case when the speed is higher. When the needle closes in the former case, the entire pressure will be removed from the delivery pipe, provided that this pipe is not closed by a non-return valve, whilst in the second case a pressure of the value of the differential pressure determined by the throttle valve remains in the delivery pipe,

In Figure 2, the casing A, which is pressed on to its seat by the screwthreadednut member B, contains the guide C for the nozzle needle valve F and the nozzle plate E. Both the guide C and the nozzle plate E are pressed on to the lower edge of the casing A by the screw cap D.

The guide C contains the ground-in and axially bored needle F, which is loaded by the spring G. v

The spring G bears against the apertured cover H screwed into the top end of the guide 0, the aperture of the plug H terminating in the fine calibre throttle aperture J, whilst the bore of the needle F extending towards the tip thereof terminates in the fine calibre injection aperture K.

delivery pipe, fuel flows through the-throttle aperture J into the space above the needle F and then traverses the bore in the needle F, and is injected through the fine aperture K into the combustion chamber.

The annular space at the tip of the needle F receives the full pump pressure, whilst the space above the said needle Fis subject to a lower pressure determined by the size of the apertures J and K.

The resultant pressure of the pressures in the spaces above and below the needle F acts in the direction of opening of the needle F and eventually attains a value greater than the pressure exerted on the needle F by the spring G. The

needle F then rises, either to its limit or until equilibrium with the loading spring pressure is established.

The mainfuel injection, into the combustion chamber now occurs, either in the form of a solid or hollow jet of fuel, the additionaljet sprayed from the aperture K being maintained as in each case.

If the pressure of the pump decreases, the pressure difference between the spaces above and below the needle F is also lowered, and at a certain pressure value the spring G is strong enough to return the needle F to its seat. If in this case the pressure drop in the delivery pipe is accelerated by a load-relieving device, there will not be a pressure in the delivery pipe when the needle F returns to its seat and further fuel will not be injected, since the pressure above the needle F must, in accordance with the spring pressure, always be less than the pressure in the delivery pipe.

Figure 3 illustrates a construction suitable for use with the usual needle-valve type injector.-

The casing A comprises the screwthreaded head B, which also carries the conical seating for the end of the delivery pipe.

the core The casing A contains the guide for the needle F, the upper end of the guide C being an excellent ground fit against the lower end of the screwthreaded head B. The needle F which has a pointed tip, is bored axially and has at the centre of its tip a fine injection aperture K which connects the space above the needle F with the combustion chamber. The spring G of the needle F at its upper end, presses a small apertured plate R on to its seat. The plate R forms an abutment for the small spring L, which constantly presses on the small throttle valve H. The strength of this spring L is so calculated in relation to the cross-section of the seat of the throttle valve H, that when the fuel flows from the delivery pipe into the space above the needle F a certain pressure difference which practically always remains constant is set up between the spaces above and below the needle F.

Figure 4 illustrates another construction inwhich the guide p for the needle F is screwed into the casing A, and the injection nozzle extending from the seat of the needle F has a number of apertures, that is to say it is of rose form, one of the injection apertures being disposed centrally, whilst the others are displaced from the centre position.

In this embodiment also the fine injection aperture K is arranged in the centre of the pointed tip of the needle F and the fuel from the aperture K passes through the central aperture of the nozzle rose.

The small throttle valve H is guided in the hollow upper portion of the needle F, which portion also contains the small spring L.

The seat of the small throttle valve H is situated in the axially-bored cover M screwing into the top end of the guide C.

The operation of. the embodiments of the injector according to the invention illustrated in Figures 3 and 4 differs from that of the embodiment according to Figure 2 only by reason of the fact that fuel does not flow into the space above the needle F upon the initiation of the pump pressure, but only when the pressure in the delivery pipe has increased to such an extent that it is greater than the sum of the pressure of the spring L, of the throttle valve H and the pressure from the combustion chamber. As soon as that has occurred, the fuel commences to flow through the needle F and its injection aperture-K, and when the pump pressure has reached such a value that the difference between the said pump pressure and the pressure in the space above the needle F exceeds the pressure of the loading spring G, the needle F opens.

When the pump pressure terminates, the throttle valve H will close within a very short time and the fuel will cease to flow therethrough, possibly before the needle F has definitely closed. If it is desired to utilise a throttle aperture of invariable size, the throttle aperture may be constituted by a clearance between the needle and its guide, the needle then not being tightly ground in the guide, but being fitted with an accurately calculated clearance.

The spring G may also be employed to load the throttle valve H, but in this case the throttle valve must have a diameter of. appropriate size, which is substantially equal to that of the needle.

Furthermore, it is po 'ble to combine the throttling actions by means of a throttle aperture of invariable size and a spring-loaded throttle valve, by the provision of a fine throttle aperture below the valve.

with such a construction, the opening of the throttle valve H, and consequently the commencement of the flow of fuel, occurs as soon as the necessary pressure difference has been reached. However, the cross-section available for the flow of fuel of the throttle valve H is then larger than that of the throttle aperture, and the latter determines the throttling action.

Obviously, in the construction illustrated in Figure 2 a non-return valve may be provided in the delivery pipe merely in order to prevent the combustion gases from being forced back into the delivery pipe.

What I claim as my invention and desire to secure by Letters Patent of the United States is:

1. An injection nozzle for internal combustion engines for effecting a preliminary injection of fuel followed by a main injection of fuel during each fuel injection operation and comprising a casing having an axially extending guide bore, a first chamber located above said guide bore and in communication therewith, a fuel inlet passage in communication with said first chamber through a restricted passage having a throttling action, a second chamber below said guide bore in communication therewith and with a fuel outlet opening at the lower end of said casing in communication with the engine cylinder, and a passage leading from said fuel inlet passage to said second chamber; a needle adapted to reciprocate within said guide bore and having a passage extending therethrough leading from said first chamber to said fuel outlet opening through a restricted passage having a throttling action, the lower end of said needle having a surface exposed to the pressure of the fuel within said second chamber, which surface terminates in a portion adapted to normally close communication between said second chamber and said fuel outlet opening, and a spring acting upon the upper end of the needle and tending tohold said needle in its normally closed position; the arrangement being such that when fuel under pressure is. forced through the inlet passage in the casing a portion of said fuel passes through the restricted opening leading to the first chamber, through said first chamber, through the passage in the needle, through the restricted passage leading from said first chamber to the fuel outlet, through the fuel outlet opening in the casing and into the engine cylinder to constitute the preliminary injection of fuel thereto, and simultaneously with said preliminary injection, fuel is forced under pressure through the passage in the casingleading to said second chamber where said pressure acting upon the surface of said needle exposed within said second chamher is sufficient to lift said needle from said fuel outlet opening against the pressure of said spring, whereby the main fuel injection enters the engine cylinder.

2. An injection nozzle as defined in claim 1 wherein the restricted passage leading from the fuel inlet passage to the first chamber comprises a fine caliber throttle aperture of invariable size.

3. An injection nozzle as defined in claim 1 wherein the passage throughthe needle is an axial passage which terminates at its lower end in a restricted passage having a throttling action on the fuel passing from the first chamber through the fuel outlet opening in the casing.

4. An injection nozzle as defined in claim 1 wherein the spring which acts upon the upper end of the needle is disposed in the first chamber.

5. An injection nozzle as defined in claim 1 wherein the pressure of the fuel inthe first chamher assists the spring in normally holding the needle in closed position with respect to the fuel outlet opening leading from the second chamber into the engine cylinder.

6. An injection nozzle as defined in claim 1 wherein a spring-loaded valve is interposed in the fuel passage leading from the fuel inlet passage to said first chamber, the loading of the valve cooperating with a substantially conical valve seat formed 'in the casing and surrounding the fuel outlet opening :from the second chamberto the engine cylinder, said tip normally closing communication between said second chamber and said fuel outlet opening, and wherein the restricted passage at the lower end of said needle terminates at the tip thereof and is constantly in communication with the main fueloutlet opening.

9. An injection nozzle as defined in claim 1 wherein the fuel outlet opening leading from the second chamber to the engine cylinder is in the form of a spray nozzle comprising at least two jet.

passages radiating outwardly from a central passage in the nozzle and an additional jet passage in the nomle disposed in axial alignment with the restricted passage at the lower end of said needle. PROSPER LORANGE.

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