WO2006003049A1

WO2006003049A1 - Injection nozzle for injecting fuel into the combustion chamber of a diesel engine

Info

Publication number: WO2006003049A1
Application number: PCT/EP2005/052159
Authority: WO
Inventors: Werner Teschner
Original assignee: Robert Bosch Gmbh
Priority date: 2004-07-07
Filing date: 2005-05-12
Publication date: 2006-01-12
Also published as: EP1766228A1; DE102004032818A1

Abstract

The invention relates to an injection nozzle (42) for injecting fuel into the combustion chamber (14) of a diesel engine via at least one first partial jet (44) and at least one second partial jet (44) which is emitted simultaneously with the first partial jet (44), a direction (46) of a first partial jet (44) being located on a first conical surface having a first cone angle (28). The injection nozzle (42) is characterized in that a direction (52, 54) of at least one second partial jet (48, 50) is located on a second conical surface having a second cone angle (56) which is smaller than the first cone angle (28).

Description

Injector for injecting fuel into a combustion chamber of a diesel engine

State of the art

The invention relates to an injection nozzle for injecting fuel into a combustion chamber of a diesel engine via at least a first partial beam and at least a second partial beam which is output simultaneously with the first partial beam, wherein a direction of a first partial beam is located on a first cone shroud with a first opening angle.

Such an injection nozzle is known for example from the Automotive Handbook, 23rd Edition, page 556. The injectors shown there are for one

Schrägeinbau provided in a cylinder head of an internal combustion engine and issue through multiple injection holes partial beams whose directions lie on a cone. The axis of the cone passes through the piston, which seals the combustion chamber movable. The opening angle of the

Cone of these known injection nozzles is in the range of 140 to 160 degrees. This geometry results in an injection into a comparatively flat volume. Appropriately, the injection occurs relatively late near top dead center of the compression of the upwardly moving piston.

Because of the late injection into a highly compressed air filling is for a mixture preparation in the combustion chamber, only a very short period of time until the onset of Combustion available. The injected fuel is therefore not distributed homogeneously throughout the combustion chamber. Instead, charge clouds are formed in the combustion chamber around or around the injection jets, in which the fuel concentration decreases from the inside to the outside. This type of charge distribution is also referred to as stratified combustion chamber filling.

As a side effect occurs at this comparatively wide opening angle good cold start capability. The good cold start capability results from the fact that, because of the wide opening angle, fuel is sprayed in the vicinity of a glow plug which is arranged in the cylinder head. The glow plug is heated electrically in the cold start case and makes it easier to ignite the filling of the combustion chamber.

According to recent development trends, diesel engines will in future also work with homogeneous combustion chamber fillings. A homogeneous distribution of the fuel in the combustion chamber is achieved by a comparatively early and deep into the combustion chamber, taking place well before the top dead center of the compression injection, so that more time is available for a homogeneous distribution of the fuel in the combustion chamber. The homogeneous distribution is also supported by the fact that the upwardly moving piston swirls the combustion chamber filling of air and fuel during further compression.

The large penetration depth results in this method from the fact that the fuel is injected at a much sharper opening angle in the direction of the upwardly running, but still relatively distant piston. In experiments with such new combustion process, a much lower cold start capability than in conventional direct injection diesel engines has been shown.

Against this background, the object of the invention is to specify measures which ensure an improvement in the cold start capability in diesel engines with homogeneous combustion processes.

This object is achieved with an injection nozzle of the type mentioned in that a direction of at least a second partial beam is located on a second conical surface with a second opening angle which is smaller than the first opening angle.

Advantages of the invention

This measure completely solves the problem. The invention is based on the finding that the undesirable effect of deterioration of the

Cold startability is less a direct consequence of the homogeneous combustion process, but rather is a direct consequence of the much smaller angle of opening of the cone of the injection directions in the homogeneous combustion process.

According to the invention, two opening angles are used, so that there is a division of the injection quantity into at least one ignition jet and further jets which ensure a homogeneous mixture distribution in the combustion chamber. It is preferable that the second opening angle is between 30 and 130 degrees.

It has been shown that with this opening angle a very good homogeneity of the fuel distribution can be achieved. It is also preferable that the first opening angle is between 130 and 160 degrees.

This angular interval corresponds approximately to the usual angular interval used for a stratified charge, which has shown good cold start capability.

Characterized in that in the injector according to the invention at least one partial beam in one for a layered

Cargo usual angle direction aims, as usual in the cylinder head mounted heater, such as a glow plug, bring much more heat in the injected fuel, which the ignition at low combustion chamber temperatures and thus the

Cold start capability significantly improved in a working with a homogeneous combustion diesel engine.

It is preferred that the injection nozzle simultaneously outputs exactly a first partial beam and a plurality of second partial beams.

By this configuration, it is achieved that a main amount of the injected fuel is available for a homogeneous distribution and only a smaller amount is diverted for an improvement of the cold start capability. As a result, losses in the advantages that result from a largely homogeneous distribution of the fuel in the combustion chamber, only slightly reduced.

It is further preferred that in each case a partial jet is output through an associated injection hole at a combustion chamber end of the injection nozzle. The output of a Kraftstoffnαenge over several injection holes allows a reproducible distribution of the fuel quantity to be injected to a plurality of partial beams, which is essential for optimizing a subsequent combustion.

It is also preferred that the two conical shells have the same conical axis and that n injection jets are distributed on the two conical shells so that an n-fold symmetry results in a projection of the n directions of the injection jets on a plane perpendicular to the conical axis. In this case, an arrangement has an n-fold symmetry when it is imaged onto itself during a rotation of 360 ° / n.

With this feature as far as possible rotational symmetry of the arrangement of the injection jets is achieved. Thus, the arrangement of the injection jets is as much as possible adapted to the symmetry of the air volume into which is injected. Since the injection takes place comparatively early in a homogeneous combustion process, this air volume is essentially defined by the cylinder shape above the piston which is moving upwards.

A further preferred embodiment is characterized in that a partial beam, the direction of which lies on the first conical jacket, has a smaller penetration depth into a combustion chamber than a partial beam whose direction lies on the second conical jacket.

This embodiment takes into account that the sub-beam is radiated on the first conical surface essentially transversely to the cylinder axis and that an injection nozzle arranged centrally in the direction of the cylinder axis can only be moved by a comparatively small distance from one lateral cylinder wall is separated. With a cylinder bore diameter to piston stroke ratio, the distance of a piston at bottom dead center to the injector is about twice the distance of the injector nozzle from the cylinder shell. In the case of an early injection with the aim of a homogeneous mixture distribution, therefore, a comparatively large penetration depth into the cylinder is to be striven for. If the sub-beam, which is output at a shallower angle, output with a comparable penetration, he would hit the cylinder wall or combustion chamber wall, which is not desirable. Impact on the cylinder wall could, for example, affect the lubricating film, and an impact of liquid fuel on a hot glow plug would lead to locally high temperature fluctuations and thus mechanical loads on the glow plug.

Furthermore, it is preferred that the injection holes are dimensioned so that a larger fuel mass is injected via a second partial jet during an injection than via a first partial jet.

This configuration, on the one hand, causes the lower penetration depth of the ignition jet and, moreover, causes the larger quantity of fuel to be available for the desired homogeneous distribution in the cylinder and only as little fuel as possible for an ignition jet to be diverted. As a result, losses that may result from the breakage of the symmetry of the injection jet arrangement with a warm internal combustion engine are kept small.

It is also preferred that the injection holes are dimensioned so that the same amount of fuel is metered via two second partial beams during an injection become .

This feature contributes as much as possible to maintain a symmetry of the fuel distribution in the cylinder and thus positively influences the combustion.

A further preferred embodiment is characterized in that the injection nozzle has markings for determining a built-in rotational angle position. It is furthermore preferred that the markings define a built-in rotational angle position in which a first partial jet has a predetermined orientation relative to a heating device or ignition device in the combustion chamber.

Through these embodiments, it is possible to

Install injection nozzle in a cylinder head so that the first part of the beam, so the ignition jet, in a predetermined direction in the combustion chamber, in which the slightest possible ignition is expected. This may, for example, be the direction in which a glow plug is arranged as a cold start aid.

It is also preferable that the first partial beam is directed to a heating device.

This arrangement ensures that the cold start improvement potential of the injection jet assembly according to the invention also comes into play when a heater arranged at a certain angle is used. With annular or other heaters distributed over the circumference of the cylinder, this feature would be dispensable.

Furthermore, it is preferred that the markings have a form-locking rotation lock. A further preferred embodiment is characterized by a fastening means for axially fixing the injection nozzle in a cylinder head of an internal combustion engine.

In such an embodiment, it is particularly preferred that the fastening means comprise a threaded sleeve or a union nut.

By these embodiments, an angular orientation about a longitudinal axis of the injection nozzle and a high-strength mounting of the injection nozzle by acting in the direction of the longitudinal axis clamping forces is simultaneously possible.

Further advantages will become apparent from the description and the accompanying figures.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination given, but also in other combinations or in isolation, without departing from the scope of the present invention.

drawings

Embodiments of the invention are illustrated in the drawings and are explained in more detail in the following description. Show it:

1 shows schematically a combustion chamber with a known, centrally arranged injection nozzle for a stratified diesel combustion process;

2 schematically shows a combustion chamber with a injection nozzle according to the invention for a homogeneous diesel combustion process; and

Fig. 3 is an observed from the direction of a piston injection nozzle as an embodiment of an injection nozzle according to the invention.

Description of the embodiments

In the figure 1, an injection nozzle 10 is shown, the combustion chamber side end 12 projects into a combustion chamber 14. The injection nozzle 10 has at its combustion chamber end 12 holes or openings 16, 18, 20, are output via the injection jets 22 in an air filling of the combustion chamber 14. The output of the

Injection jets 22 in different directions 24, 26, which define a first opening angle of a first cone sheath.

The combustion chamber 14 is bounded above by a cylinder head 30 and to the sides by a cylinder jacket 32 and movably sealed by a piston 34. The numeral 36 in FIG. 1 marks the position of a top dead center of movement of the piston 34 in the cylinder jacket 32. The illustration of FIG. 1 represents a known combustion chamber and injection jet geometry used in conjunction with a late fuel injection for the formation of a stratified combustion chamber charge becomes. In this case, the injection takes place relatively late, so only shortly before the piston 34 reaches its top dead center 36. Accordingly, the remaining volume of the combustion chamber 14 at this time is comparatively flat and wide. This geometry of the combustion chamber 14 at the time of injection is taken into account by a geometry of the injection jets angle that passes through a comparatively wide first opening angle 28 is characterized. The first opening angle 28 is typically between 130 and 160 ° in the boundary conditions shown in FIG.

To improve the cold start properties, a glow plug 38 is usually arranged in the cylinder head 30, the combustion chamber side end 40 is electrically heated. The very wide first opening angle, which is an interval between 130 ° and 160 °, as used in the prior art, has shown good cold start properties.

Figure 2 shows schematically a combustion chamber 14 with an injection nozzle 42 according to the invention for a homogeneous

Diesel combustion process. The injection nozzle 42 outputs a first partial jet 44 in a direction 46 which lies on a first conical jacket with a first opening angle 28. In addition, the injection nozzle 42 is at least a second partial beam 48 and / or 50 in a second

Direction 52 and / or 54, each lying on a second cone sheath with a second opening angle 56, which is smaller than the first opening angle 28. The second opening angle 56 is preferably in an interval between 30 ° and 130 °, while the first opening angle 28 corresponds to the known from the prior art ago opening angle from the interval between 130 and 160 ^c .

The second partial beams 48 and 50 are injected at the comparatively small aperture angle 56 to achieve a large penetration depth with a comparatively early injection. The piston 34 is in this case still relatively far away from its upper Totpunktläge 36, so that the known Injection geometry, as shown in Figure 1, would capture only a portion of the combustion chamber volume. The piston 34, which continues to move upwards during and after an injection, swirls the injected fuel with the air filling of the combustion chamber 14, so that the result is a substantially homogeneous mixture of fuel and air in the combustion chamber 14.

To a reliable ignition of the combustion chamber filling even at low temperatures of the combustion chamber 14 and the

Cylinder jacket 32, the cylinder head 30 and the piston 34 to ensure the first partial beam 44 is preferably sold with the flatter, or wider, first opening angle 28. This is done with the aim of achieving a local fuel enrichment at the combustion chamber end 40 of the glow plug 38. With a suitable orientation of the injection nozzle 42, a single first partial jet 44 suffices, which has a lower penetration depth than the second partial beams 48 and 50 and which also transports less fuel.

By injecting a comparatively small amount of fuel in the vicinity of the combustion chamber end 40 of the glow plug 38 and by dosing the majority of the injected fuel by second partial beams 48 at an acute angle into the depth of the combustion chamber 14, both a homogeneous diesel combustion process can be realized as well Reliable ignition of the combustion chamber fillings at low temperatures can be achieved. The first sub-beam 44 thus serves as a kind of ignition. It is designed, for example by a smaller injection hole 16, to a lower injection quantity than the other partial beams 48, 50 in order to influence the pollutant emissions as little as possible in a warm combustion engine. By reducing the amount of fuel transported by the first partial jet 44, the penetration depth of the first partial jet 44 into the combustion chamber 14 is also reduced. The injection nozzle 42 is preferably inserted into the cylinder head 30 such that the first partial jet 44 is deposited in the direction of the glow plug 38. For this purpose, the injection nozzle 42 may have at its periphery a fixed mark 58 which fits positively into a correspondingly formed counterpart of the cylinder head 30 and fixes the injector 42 in the desired angular position. In the axial direction, the injection nozzle 42 is preferably clamped by means of threaded sleeves, banjo bolts, union nuts or claws with the cylinder head 30.

FIG. 3 shows an injection pattern of an exemplary embodiment of an injection nozzle 42 viewed from the direction of rotation of the piston 34. The injection nozzle according to FIG. 3 has a first injection opening 16 and seven second injection openings 18. The total of eight

Injection openings 16, 18 are arranged so that the directions of the output partial beams have an eightfold symmetry. It is preferred that in each case the same injection quantities are output via the second injection openings 18, so that the partial beams 48 emitted via the injection openings 18 have the same penetration depth. In contrast, the first part of the beam 44 should have a lower penetration depth and transport a lower fuel mass. This is illustrated in FIG. 3 by a partial beam 44 shortened in comparison to the second partial beams 48.

Claims

claims

An injector (42) for injecting fuel into a combustion chamber (14) of a diesel engine via at least a first sub-jet (44) and at least a second sub-jet (46) issued simultaneously with the first sub-jet (44), one direction (46) of a first partial beam (44) lies on a first conical jacket with a first opening angle (28), characterized in that a direction (52, 54) of at least one second partial beam (48, 50) on a second conical jacket with a second opening angle (56) which is smaller than the first opening angle (28).

2. Injection nozzle (42) according to claim 1, characterized in that the second opening angle (56) is between 30 and 130 degrees.

3. Injection nozzle (42) according to claim 1 or 2, characterized in that the first opening angle (28) is between 130 and 160 degrees.

4. Injection nozzle (42) according to at least one of claims 1 to 3, characterized in that the injection nozzle (42) at the same time exactly a first partial beam (44) and a plurality of second partial beams (48, 50) outputs.

5. ^' injector (42) according to at least one of the preceding claims, characterized in that in each case a partial jet (44, 48, 50) through an associated injection hole (16, 18, 20) at a combustion chamber end of the injection nozzle (42) is output ,

6. Injection nozzle (42) according to at least one of the preceding claims, characterized in that the two cone shells have the same cone axis and that n injection jets (44, 48, 50) are distributed on the two cone shells so that in a projection of the directions (46, 52, 54) of the injection jets (44, 48, 50) results in an n-fold symmetry on a plane perpendicular to the cone axis.

7. Injection nozzle (42) according to one of the preceding claims, characterized in that a partial beam

(44), whose direction is located on the first cone sheath, a smaller penetration depth into a combustion chamber (14) has as a partial beam (48, 50) whose direction (52, 54) lies on the second cone sheath.

8. Injection nozzle (42) according to at least one of claims 5 to 7, characterized in that the injection holes (16, 18, 20) are dimensioned so that a larger fuel mass is injected via a second partial jet (48, 50) during an injection as over a first partial beam (44).

9. Injection nozzle (42) according to claim 7, characterized in that the injection holes (16, 18, 20) are dimensioned so that over two second partial beams (48, 50) are metered at an injection equal amounts of fuel.

9. Injection nozzle (42) according to at least one of the preceding claims, characterized in that the injection nozzle (42) has markings (58) for fixing a built-in rotary angle position.

10. Injection nozzle (42) according to claim 9, characterized in that the markings (58) define a built-in rotation angle position, wherein a first Partial beam (44) has a vorbestiπimte alignment with a heater (38) or igniter in the combustion chamber.

11. Injection nozzle (42) according to claim 10, characterized in that the first partial jet (44) is directed to a heating device (38).

12. Injection nozzle (42) according to at least one of claims 9 to 11, characterized in that the markings (58) form a positive rotation.

13. Injection nozzle (42) according to at least one of the preceding claims, characterized by a fastening means for axially fixing the injection nozzle (42) in a cylinder head (30) of an internal combustion engine.

14. Injection nozzle according to claim 13, characterized in that the fastening means comprise a threaded sleeve or a union nut.