US3394891A

US3394891A - Fuel injection nozzle arrangement for preinjection and main injection of fuel

Info

Publication number: US3394891A
Application number: US603492A
Authority: US
Inventors: Voit Willy
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1965-12-31
Filing date: 1966-12-21
Publication date: 1968-07-30
Anticipated expiration: 1985-07-30
Also published as: GB1125029A; FR1505156A; AT276866B

Description

July 30. 1968 W. VOIT 3,394,891

FUEL INJECTION NOZZLE ARRANGEMENT FOR PREINJECTION AND MAIN INJECTION 0F FUEL Filed D80. 21, 1966 Mm-wroe United States Patent 3,394,891 FUEL INJECTION NOZZLE ARRANGEMENT FOR gIJIIEETINJECTION AND MAIN INJECTION F Willy Voit, Stuttgart, Germany, assignor to Robert Bosch G.m.b.H., Stuttgart, Germany Filed Dec. 21, 1966, Ser. No. 603,492 Claims priority, application Germany, Dec. 31, 1965, B 85,219 12 Claims. (Cl. 239533) ABSTRACT OF THE DISCLOSURE A fuel injection nozzle arrangement for pre-injection and main injection of fuel into the cylinders of an internal combustion engine in which fuel under pressure from -a fuel pump may pass to the injection nozzle through a main feed passage and a throttling feed passage of restricted cross section and in which a single control slide is moved by the fuel under pressure to control flow of fluid through the aforementioned passages in such a manner that the throttling passage is first opened so that fuel may pass therethrough, and subsequently thereto both passages are closed and finally the main passage is opened while the throttling passage is closed to reduce the amount of fuel injected into the cylinder before the ignition takes place therein.

Background of the invention The present invention relates to a fuel injection nozzle arrangement for pre-injection and main injection of fuel into the cylinder of an internal combustion engine. Such arrangements are known in the art and they usually comprise a nOZZle needle moved by the pressure of the fuel coming from a fuel pump to an open position, and valve means in the fuel passage to a pressure chamber of the nozzle and actuated by the pressure of the fuel against the force of a spring in such a manner that the valve means, which in its rest position closes the fuel passage, gradually increases the cross section of a throttling passage formed by the valve means during its movement away from the rest position. Such an arrangement is shown, for instance, in the US. Patent 2,090.350 to Heinrich et al.

The known fuel injection nozzle arrangements of the aforementioned kind already produce during each injection a relatively slow increase in injected amount of fuel. However, in many cases this is not suflicient to avoid that, at the moment ignition of the fuel takes place, too great an amount of fuel has already been injected into the cylinder. In this case, the suddenly ignited fuel will produce noisy operation of the engine, which will be especially noticeable during idling or acceleration of the latter.

It is an object of the present invention to provide for a fuel injection nozzle arrangement for pre-injection and main injection of fuel into the cylinder of an internal combustion engine which avoids the disadvantages of similar fuel injection nozzle arrangements known in the art.

It is an additional object of the present invention to provide for a fuel nozzle arrangement, as mentioned above, which is constructed of relatively few and simple parts so that the whole arrangement may he manufactured at reasonable cost and will stand up trouble-free under extended use.

Summary of the invention The fuel injection nozzle arrangement according to the present invention for pre-injection and main injection of fuel into the cylinder of an internal combustion engine 3,394,891 Patented July 30, 1968 mainly comprises a nozzle body having an outlet opening and a pressure chamber upstream of the outlet opening, a nozzle needle arranged in the nozzle body and movable from a rest position closing the outlet opening to an active position opening the outlet opening when fuel under pressure is fed into the pressure chamber, fuel inlet passage means adapted to be connected at one end to a fuel injection pump feeding fuel under pressure into the fuel inlet passage means, fuel feed passage means communicating at opposite ends with the fuel inlet passage means and the pressure chamber of the nozzle body, control means in the inlet fuel feed passage means for controlling flow of fuel through the fuel feed passage means, the control means being movable by the fuel under pressure in the fuel inlet passage means from a rest position to an intermediate position and from there to an end position, and the control means and the fuel feed passage means being constructed and cooperate with each other to provide in the rest position of the control means only throttled flow of fuel through the fuel passage means, to completely stop the fiow of fuel through said fuel feed passage means when in said intermediate position and to provide for increased flow of fuel when in said end position, and biasing means cooperating with the control means and being biased to yieldably maintain the latter in the rest position thereof.

The fuel feed passage means preferably include a main feed passage and a throttling passage each communicating at one end with the fuel inlet passage means and at the other end with the aforementioned pressure chamber of the nozzle body, and the control means may include a control slide movable between the aforementioned positions and cooperating with the main feed passage and the throttling passage in such a manner that, when the control slide is in the rest position, the throttling passage is opened while the main feed passage is closed, while in the intermediate position of the control slide both of the passages are closed, and in the end position of the control slide the throttling passage is closed While the main feed passage is opened.

This arrangement will assure that the amount of fuel injected into the cylinder up to the moment of the ignition will be smaller than with the fuel injection nozzle arrangements of the prior art.

The pressure in the fuel inlet passage increases with increasing number of revolutions of the internal combustion engine in which the fuel injection arrangement is used. correspondingly, at a constant biasing force tending to yieldably maintain the control slide in its rest position, the speed of movement of the control slide away from the rest position and therewith the time of the pre-injection will change in dependence on the rotational speed of the engine. According to a further feature of the present invention this dependency of the pre-injection from the rotational speed of the engine can be influenced by means of a second throttling passage connecting the end of the guide passage towards which the control slide moves from its rest to its end position with a leakage chamber of the arrangement. This second throttling passage produces during increasing fuel pressure an increasing braking of the movement of the control slide from its rest towards its end position and thereby an increased pre-injection. This is advantageous since the throttling passage located in the path of the fuel to the pressure chamber in the nozzle body acts in the opposite direction.

The desired quick return of the control slide to its rest position after each injection is preferably obtained by a one-way valve connecting the guide passage of the control slide with the leakage chamber. The one-way valve opens toward the guide passage so that the liquid fuel displaced over the second throttling passage during movement of the control slide from its rest toward its end position may be quickly sucked back over the one-way valve during return movement of the slide.

The biasing means which cooperate with the control slide for yieldably maintaining the latter in the rest position thereof are preferably constituted by a compression spring adjustably arranged to thereby adjust the biasing force, whereby, besides the aforementioned two throttling passages a third means is provided to adjust the injection process which is divided in a pre-injection and a main injection period.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

Brief description of the drawing The drawing is an axial cross section through the fuel injection nozzle arrangement according to the present invention.

Description of the preferred embodiment Referring now to the drawing, it will be seen that the fuel injection nozzle arrangement according to the present invention mainly comprises a nozzle holder 1 formed with an axial stepped bore 211 20 therethrough. An elongated pin 3 extends with clearance through the lower portion 2a of the aforementioned axial bore and the pin 3 abuts with its lower end against a nozzle needle 4 and with its upper end against a spring plate 7a for a valve spring 7. The nozzle needle 4 is guided for movement in axial direction in the axial bore of a nozzle body 6 which is releasably connected to the bottom end of the nozzle holder by means of a screw cap 5. The nozzle body 6 is provided at its free end with an outlet opening coaxial with the nozzle needle 4 and rearwardly of this outlet opening with a pressure chamber 25.

The valve spring 7 is arranged in the large diameter middle portion 212 of the axial bore and the uppermost small diameter portion 2c of this bore is provided with an inner screw thread with which an adjusting screw 9 for the valve spring 7 is threadingly engaged and which can be fixed in any adjusted position by means of a counternut 8. The large diameter middle portion 2b of the axial bore serves at the same time as a leakage chamber, and a return passage 10 communicates with the upper end of the leakage chamber and the latter is connected through the lower bore portion 2a with the axial bore through the nozzle body 6 in which the nozzle needle 4 is slidably guided, so that any fuel leaking through the clearance between the outer surface of the nozzle needle and the surface of the axial bore through the nozzle body may pass into the aforementioned leakage chamber.

The nozzle holder 1 is provided with a laterally projecting connecting portion 11 for connecting the nozzle holder to a non-illustrated fuel pressure conduit coming from a fuel pump, and opposite the connecting portion 11, with a projecting portion 12 coaxially arranged with the portion 11 and projecting to the other side of the nozzlel holder 1. A spring chamber 13 is formed in the projecting portion 12. The common axis of the projecting

portions

11 and 12 crosses the longitudinal axis of the nozzle needle 4 substantially at right angles.

A stepped cross bore is formed along this common axis which starts at the left side, as viewed in the figure, with a fuel inlet passage 14 and which is continued by a guide passage 15 of larger diameter in which a control slide 16 is movable in axial direction. An elongated pin 17 abuts with one end thereof against the end face of the control slide 16 which faces away from the fuel inlet passage 14, and the pin 17 is guided for movement in axial direction in a portion of the cross bore. The pin 17 carries at its other end extending into the spring chamber 12 a spring plate 18 for a compression spring 19, the precornpression of which may be adjusted by an adjusting screw 20.

The control slide 16 is provided intermediate its ends with an annular groove 21 which through an axial passage 22in the control slide communicates with the end face of the latter facing the fuel inlet passage 14. Fuel feed passage means extend through the nozzle holder and the fuel feed passage means include a main feed passage 24 which communicates at its upper end 23 with the guide passage 15 which forms part of and a continuation of the fuel inlet passage 14 and with the lower end thereof with the pressure chamber 25 in the nozzle body 6, and a throttling passage 26, the upper end of which communicates spaced in direction of movement of the control slide 16 from the upper end 23 of the main fuel passage with the guide passage 15, whereas the lower end of the throttling passage 26 communicates with a portion of the main fuel passage 24 spaced from the upper end thereof so as to be likewise in communication with the pressure chamber 25 through the main fuel passage 24. Between the outer surface of the pin 17 and the surrounding wall of the nozzle holder 1 is an annular gap 27 provided which forms a second throttling passage and which is in communication through a bore 28 withthe middle portion 2b of the axial bore through the nozzle holder 1 which forms the aforementioned leakage chamber. The leakage chamber 2b is also connected through a channel 30 in which a one-way valve 29 is arranged with the guide passage 15 for the control slide 16. The one-way valve is constructed to open in direction toward the guide passage 15.

The control slide is illustrated in the drawing in a rest position in which the annular groove 21 of the control slide 16 communicates with the throttling passage 26, so that at the start of the pressure stroke of the non-illustrated injection pump, the fuel fed into the fuel inlet passage 14 will pass throu-gh the channel 22 and the annular groove 21. of the control slide 16 into the throttling passage 26 and through the passage 24 into the pressure chamber 25 of the nozzle body 6. The nozzle needle 4 is thereby slightly lifted from its seat at the outlet opening of the nozzle body 6 through the increasing pressure in the pressure chamber so that a pre-injection of a small amount of fuel into the cylinder of the combustion engine will occur. When the pressure in the fuel. inlet passage 14 surpasses the pressure exerted by the spring 19 on the control slide 16, the latter will move towards the right, as viewed in the drawing. The pro-injection will continue during movement of the control slide through the distance b, and it will stop when the left edge, as viewed in the drawing, of the annular groove 21, will pass beyond the throttling passage 26. After a movement'of the control slide 16 against the force of the spring 19 through the distance a, the end edge of the control slide will clear the opening 23, so that the pressure in the fuel inlet passage will act again in the pressure chamber 25 and will move the nozzle needle to its fully open position. Between closing of the opening of the throttling passage 26 and clearing of the opening 23- of the main fuel feed passage, that is during movement of the control slide 16 through a distance (a-b), the throttling passage 26 as well as the opening 23 of the main fuel passage are closed. Feeding of fuel into the pressure chamber 25 of the injection nozzle and therewith any injection of fuel is therefore completely interrupted in the aforementioned intermediate position of the control slide 16.

When the number of revolutions of the combustion engine increases. so that the feeding pressure of the injection pump connected therewith rises, a fastener displacement of the control slide 16 which would result therefrom is prevented through the annular throttling passage 27 through which the control slide has to displace a portion of the liquid fuel in the guide passage 15 into the leakage chamber 2b. This arrangement has therefore the purpose of increasing the amount of fuel passing through the throttling passage 26 into the pressure chamber 25 during increase of the number of revolutions of the combustion engine, since without the annular throttling passage 27 a faster displacement of the control slide and therewith a reduction of the pre-injected fuel amount would result with increasing number of revolutions of the combustion engine. The time of the pre-injection may also be influenced by adjusting the prestress of the compression spring 19. On the other hand, the throttling passage 26 acts to reduce the amount of pre-injection of the fuel. Through the opposing actions of the throttling passages 26 and 27, it is possible to regulate the amount of pre-injection independent of the number of revolutions of the combustion engine so that the pre-injection of fuel remains substantially constant during the whole range of revolutions of the combustion engine, or that the amount of pre-injection changes only in a predetermined desired manner.

After an injection cycle has been finished, the pressure in the fuel inlet passage 14 decreases, the valve needle 4 engages its valve seat, and the control slide 16 returns under the influence of the compression spring 19 to its rest position. During this return movement of the control slide to its rest position, liquid fuel will be sucked from the leakage chamber 2b over the one-way valve 29 into the guide passage to fill the latter.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of a fuel nozzle arrangement differing from the types described above.

While the invention has been illustrated and described as embodied in a fuel nozzle arrangement for pre-injection and main injection of fuel into the cylinder of an internal combustion engine, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims:

1. A fuel injection nozzle arrangement for pre-injection and main injection of fuel into the cylinder of an internal combustion engine comprising, in combination, a nozzle body having an outlet opening and a pressure chamber upstream of said outlet opening; a nozzle needle arranged in said nozzle body movable from a rest position closing said outlet opening to an active position opening said outlet opening when fuel under pressure is fed into said pressure chamber; fuel inlet passage means adapted to be connected at one end to a fuel injection pump feeding fuel under pressure into said fuel inlet passage means; fuel feed passage means communicating at opposite ends with said fuel inlet passage means and said pressure chamber; control means in said fuel inlet passage means for controlling fiow of fuel into said fuel feed passage means, said control means being movable by the fuel under pressure in said fuel inlet passage means from a rest position to an intermediate position and from there to an end position, said control means and the fuel feed passage means constructed and cooperating with each other to provide in said rest position of said control means only throttled flow of fuel through said fuel feed passage means, to completely stop the flow of fuel through said fuel feed passage means when in said intermediate position, and to provide for increased flow of fuel into said pressure chamber when in said end position; and biasing means cooperating with said control means and being biased to yieldably maintain the latter in said rest position.

2. A fuel injection nozzle arrangement as defined in claim 1 and including adjusting means cooperating with said biasing means for adjusting the biasing force of the latter.

3. A fuel injection nozzle arrangement as defined in claim 1, wherein said fuel feed passage means includes a main feed passage and a throttling passage, each communicating at one end with said fuel inlet passage means and at the other end with said pressure chamber, and wherein said control means includes a control slide movable in axial direction of the inlet passage means between said positions thereof.

4. A fuel injection nozzle arrangement as defined in claim 3, and including throttling means cooperating with said control slide for braking movement of the latter from said rest to said end position thereof.

5. A fuel injection nozzle arrangement as defined in claim 4, wherein said biasing means include a compression spring.

6. A fuel injection nozzle arrangement as defined in claim 3, wherein said nozzle needle is slidably guided in a bore of said nozzle body coaxially arranged with said outlet opening, and wherein said biasing means includes a compression spring acting on one side of said control slide to yieldably maintain the latter in said rest position, and including leakage chamber means communicating with said bore so that fuel leaking through a clearance between the outer surface of the needle and the bore surface will pass into said leakage chamber means, said control slide being slidably guided in a guide passage forming part of said inlet passage means, and a second throttling passage providing communication between said guide passage at said one side of the control slide and said leakage chamber means.

7. A fuel injection nozzle arrangement as defined in claim 6, and including one-way valve means providing additional communication between said leakage chamber means and said guide passage at said one side of the control slide, said one-way valve means opening toward said guide passage.

8. A fuel injection nozzle arrangement as defined in claim 7, wherein the axis of said guide passage crosses the axis of said nozzle needle substantially at right angles.

9. A fuel injection nozzle arrangement as defined in claim 8, and including a pin connecting said control slide with said compression spring, said pin and said compression spring being arranged coaxially with said guide passage, and means cooperating with said compression spring for adjusting the force with which said spring acts on said control slide.

10. A fuel injection nozzle arrangement as defined in claim 7, and including housing means forming a nozzle holder, said nozzle body being releasably connected to one end of said nozzle holder, said housing means including a pair of projecting portions, respectively projecting to opposite sides, the axis of these projecting portions crossing the axis of the nozzle holder substantially at right angles, said inlet passage means being formed in one of said projecting portions and the other of said projecting portions being formed with a cavity in which said compression spring is located substantially coaxial with said inlet passage means, and including a pin coaxial with said compression spring and connecting one end of the latter with said control slide, and an adjusting screw engaging the other end of said spring.

11. A fuel injection nozzle arrangement as defined in claim 10, wherein said pin extends through a passage providing communication between said leakage chamber means and said guide passage, and said second throttling passage being formed by an annular gap around saidpin.

12. A fuel injection nozzle arrangement as defined in claim 3, wherein said one end of said main feed passage and said one end of said throttling passage are spaced 7 8 in direction of movement of the control slide from each References Cited other and wherein said control slide is constructed in such UNITED STATES PATENTS a manner that the movement of the latter from the rest position to the position where it opens said main feed pass- 3,368,761 2/1968 Pehzzom 239-533 age is greater than the movement of the control slide from 5 said rest position to the position where it closes said HENSON WOOD lma'y Exammer throttling passage. M. Y. MAR, Assistant Examiner.