EP1413744B1 - Pressure storage for a common-rail system - Google Patents

Description

The invention relates to a pressure accumulator for a common rail system Internal combustion engine according to the preamble of the independent Claim 1.

In particular, the invention relates to a pressure accumulator suitable for a common Rail system is suitable in a large diesel engine. Large diesel engines For example, as main propulsion units for ships or as Stationary systems used to generate electricity. They are mostly as slow running two-stroke crosshead machines or as four-stroke machines educated. Pressure accumulators of this type are known e.g. from WO 03 023220 (Prior art under Article 54 (3) EPC) and in DE 199 45 786 known. According to recent developments, modern Big diesel engines the fuel injection, the gas exchange, the Water injection and, where appropriate, auxiliary systems, eg. As for control oil, with Common rail systems operated. It is by means of pumps the respective Fluid, e.g. As the fuel for injection, a hydraulic medium for Operation of the outlet valves or a working medium for controlling the Injection, conveyed under high pressure into an accumulator, which is also called Accumulator is called. With the pressurized fluid from the each accumulator then all the cylinders Internal combustion engine supplies or the valves and the Fuel injectors controlled.

Usually, the accumulators are each as a tube-like, at both Ends closed components designed, which is approximately equal to the height Cylinder heads extend along the engine. The tubular basic body the pressure accumulator typically have a plurality of holes, over which the storage space of the pressure accumulator with the respective Supply or actuation devices of the individual cylinders is connectable.

The highest pressures typically occur in the common rail system for the Fuel injection on. In the associated accumulator, the pressure for example, be up to 2000 bar. In operation, it is in particular the dynamic, z. B. caused by pressure fluctuations, loads, which place high mechanical demands on the pressure accumulators. The High pressure resistance of the pressure accumulator is particularly by the limited radial bores. These can be the voltages, for example the comparison voltage to increase by a factor of three to four and more.

To increase the high pressure resistance of the accumulator in a common Rail injection system is proposed in DE-A-199 49 962, as Storage space serving the interior of the body in the area of Forming the holes just form, so the voltage spikes in the intersection between the holes and the body to reduce. These flat areas are subsequently replaced by a local, Material-removing machining made.

The object of the present invention is to provide a pressure accumulator for a Commmon Rail system to propose an internal combustion engine, in which with very simple measures a very high internal pressure at dynamic load is made possible without the external Dimensions and thus the space requirement of the pressure accumulator increased becomes. In particular, the accumulator for a common rail system of a Be suitable for a large diesel engine and especially for one Fuel injection system.

The problem solving pressure accumulator is characterized by the features of independent claim 1.

Thus, according to the invention, a pressure accumulator for a commmon rail System of an internal combustion engine proposed with a tubular Basic body with a wall, the one inside the main body provided storage space for the medium to be stored limited, and with at least one bore for discharging the medium extending through the Wall stretches. On the inside of the wall is at least one in the storage space in reaching, curved vault provided, the is arranged such that the bore within the curved curvature enters the storage space.

It has been shown that by this inward reaching vault, whose Curvature is finally "caused by the hole Voltage increases can be significantly reduced. By the optimized internal shape of the accumulator can be given at Fatigue strength of the material from which the base body is made, the allowable internal pressure for dynamic loads increase significantly or the outer dimension of the accumulator, in particular its diameter, can be reduced because, for example, the wall made thinner can be. Essential here is the knowledge, that area, in the bore opens into the storage space, with a finite Curvature - so in particular not flat - to design.

In a preferred embodiment, said area has a curvature, which has the opposite sign as the curvature of the remaining part of Inside the wall, which is the substantially cylindrical Storage space limited.

Preferably, the arch extends over a substantial portion of Length of the storage space and especially preferred over the entire length of the storage space. This has the consequence that the inner profile of Storage space, that is its section perpendicular to the longitudinal axis, over the entire length of the memory space is the same. Thus can on local Internal processing of the storage space are dispensed with, causing the Significantly simplify production. The main body with the Storage space can be easily, for example, by extrusion, Casting or broaching with a correspondingly shaped broach, getting produced.

Another advantageous measure is, on the inside of the wall at least two - for example three - in the memory space Provide in-reaching, curved bulges, each over extend a substantial part of the length of the storage space and with respect to the circumferential direction of the inside of the wall various positions are provided. So it's on the inner circumference distributed several vaults provided, preferably each about extend the entire length of the storage space. Thus, in various directions pointing holes are provided, thereby the flexibility of the accumulator with respect to his Connection options significantly increased.

With a view to minimizing the stresses run the hole or the holes in the radial direction, so that their central axis perpendicular to the Longitudinal axis of the body is. Furthermore, it has to be advantageous proved, if each hole with respect to the circumferential direction of the inside the wall in the middle of the vault empties into the storage space, the means the central axes of the holes lie in the center of the vault. Of course it is also possible, the holes eccentric or offset to arrange each other. It is essential that the holes within the Bulge lead into the storage room.

Practice shows that each camber preferably has a height in radial Direction, which is between 5% and 30% of the inner diameter of the Memory space is. With this height is the maximum amount meant, the curvature on the otherwise, for example, circular Contour of the cross section of the storage space protrudes into this.

The curvature according to the invention, which extends into the storage space, leaves be realized by the memory space at least comprises two substantially cylindrical longitudinal bores, such are arranged so that their cross sections overlap. A Variant is the storage space by two cylindrical To realize longitudinal bores whose axes are parallel and are spaced apart from each other so that the cross sections of Overlap longitudinal bores. This means that the distance between the axes of Longitudinal holes are smaller than the sum of the radii of the two Longitudinal holes. This measure results in a storage space, its inner profile (cross-sectional area perpendicular to the longitudinal axis) the shape has an eight. The area where these eight "constrict" has, then forms two extending into the storage space curved Buckling in the sense of the present invention.

The realization form in which the memory space is at least two has overlapping longitudinal bores, offers the advantage of a particularly simple production. It only requires the making of two (or more) longitudinal bores in the tubular structure from which the Basic body is produced.

Another advantageous feature is when the wall of the Base body has on its outer side at least one flat, the is arranged and designed so that the hole on the outside of the Wall opens into a flat surface. This measure will allows, directly on the outside of the wall actuation or Supply devices provided with the medium from the Pressure accumulator to be acted upon - for example, slide valves for the fuel injection. This has the advantage that on high pressure resistant Connecting lines can be dispensed with.

A further advantageous variant is that the wall of the Body on its outside at least one flat strip which extends substantially the entire length of the tubular Base body extends. This allows, for example, at the Outside of the high-pressure accumulator to provide a heating element to the Apply heat to the medium in the storage room. The flat strip can also serve as a support, for example for fastening the Pressure accumulator.

The pressure accumulator according to the invention is particularly suitable for the Common rail system of a large diesel engine and specially for the common Rail system for fuel injection.

Further advantageous measures and preferred embodiments of Invention will be apparent from the dependent claims.

Fig.1:

einen Querschnitt.durch ein erstes Beispiel eines nicht erfindungsgemässen Druckspeichers entlang der Schnittlinie I-I in Fig. 2,

Fig. 2:

einen Längsschnitt durch das Beispiel aus Fig. 1 entlang der Schnittlinie II-II in Fig. 1,

Fig.3:

wie Fig. 1, jedoch für eine Variante des ersten Beispiels,

Fig. 4:

einen Querschnitt durch ein zweites Beispiel eines nicht erfindungsgemässen Druckspeichers,

Fig. 5:

wie Fig. 4, jedoch für eine Variante des zweiten Beispiels,

Fig. 6:

wie Fig. 4, jedoch für eine weitere Variante des zweiten Beispiels,

Fig. 7:

einen Querschnitt durch ein Ausführungsbeispiel eines erfindungsgemässen Druckspeichers, und

Fig. 8:

Wie Fig. 7, jedoch für eine Variante des Ausführungsbeispiels.

In the following the invention will be explained in more detail by means of embodiments and with reference to the drawing. In the schematic drawing show:

Fig.1:

a cross section. By a first example of a non-inventive pressure accumulator along the section line II in Fig. 2,

Fig. 2:

1 is a longitudinal section through the example of FIG. 1 along the section line II-II in Fig. 1,

3 shows:

like FIG. 1, but for a variant of the first example,

4:

a cross section through a second example of a non-inventive pressure accumulator,

Fig. 5:

like FIG. 4, but for a variant of the second example,

Fig. 6:

like FIG. 4, but for a further variant of the second example,

Fig. 7:

a cross section through an embodiment of an inventive accumulator, and

Fig. 8:

As Fig. 7, but for a variant of the embodiment.

Fig. 1 shows a cross section through a first example of a Accumulator, the total with the Reference numeral 1 is designated. The cut is made along the section line I-I in Fig. 2. Fig. 2 shows the same example in a longitudinal section along the line II-II in Fig. 1st

As common rail systems and especially those for Large diesel engines and especially for fuel injection in Large diesel engines with respect to their structure and their function sufficient are not discussed in detail below.

The pressure accumulator 1 has a tubular, for example cylindrical, Basic body 2 with a wall 3, the inside 31 a Storage space 4 for the medium, for example fuel under high pressure, limited. The main body 2 and the storage space 4 extend in Direction of a longitudinal axis L. Further, at least one bore 5 provided in the radial direction, that is perpendicular to the longitudinal axis L, extends through the wall 3 and the storage space 4 with the outside 32 of the wall 3 connects. Through the hole 5, the medium can the storage space 4 are removed.

On the inside 31 of the wall 3 is a curvature. 6 provided, extending in the direction of the axis L over a substantial part the storage space 4 and preferably over the entire length of Memory space 4 extends. In the illustration according to FIG. 2, the curvature is 6, the difference to that of the representation according to the upper part 3a of the wall. 3 thicker than the lower part 3b as shown. As this particular Fig. 1 illustrates, the curvature 6 is continuously curved, so it has no flat areas. The curvature of the curvature 6 has the opposite sign as the curvature of the remaining part of the Inner side 31 of the wall 3. For better understanding in Fig. 1 is the Contour K, resulting in a precisely circular cross section of the Memory space 4 would result, dashed added.

The transition region 61 between the bulge 6 and the rest of the Inside 31 of the wall 3 is rounded, so here no edges are present and the tensions are low even in these areas being held.

The bulge 6 is arranged with respect to the circumferential direction so that the Bore 5 symmetrically in the center of the curvature 6 in the storage space. 4 opens.

Regarding the design of the curvature 6, especially its curvature and the Location of their center of curvature, numerous variants are possible. The Curvature of the curvature 6 does not have to be constant either. It is essential however, that the curvature has a finite value and another Sign as the curvature of the rest of the inside 31, that is, the Buckle 6 must extend into the storage space 4. It is also essential that the bore 5 in total within the curvature 6 in the Memory space 4 opens, that is, the mouth of the bore 5 in the Storage space 4 must be completely covered by the curvature 6.

Regarding the height H of the bulge 6, bringing its maximum deviation from The contour K is meant in the radial direction, it has in practice as proven advantageous if this height H between 5% and 30% of Inside diameter D of the storage space 4 is.

Usually, the accumulator 1 has several holes 5. These are then arranged one behind the other in the first embodiment, so that each of the holes 5 as described in the center of the curvature 6 in the memory space opens.

Due to the curvature 6, the pressure accumulator 1 has a Internal shape optimized with respect to the stresses. By in the Storage space 4 projecting embodiment of the curvature 6 in the in terms of stresses critical area where the holes 5 This area remains under pressure when pressurized Compressive stresses. In known accumulators are directly at Pressurization generates tangential stresses, ie tensile stresses. In the embodiment takes place only at significantly higher Strains of transition to the range of tensile stresses. Thereby can the accumulator 1 even with dynamic Loads are exposed to significantly higher internal pressures. By the inner shape of the pressure accumulator 1, this can in Compared to known memories a multiple of the internal pressure get abandoned. On the other hand, at the same internal pressure as in known storage and at the same volume of the memory space of Memory significantly slimmer, so with a smaller thickness the wall 3, to be configured.

Preferably, the curvature 6 extends over the entire length of Memory space 4, so that the inner profile, bringing the cross section of the Memory space 4 is meant, over the entire length of the main body. 2 is equal to. This means a considerable simplification of the Manufacturing process. The main body 2 of a Accumulator 1 can easily by extrusion, casting or spaces by means adapted to the desired cross-section Tool be made. Subsequent local internal work on the inside 31 of the wall 3 are no longer needed.

Another advantage is that the holes 5 with respect to the longitudinal direction can be drilled at any point, resulting in flexibility significantly increased in terms of adaptation to different circumstances.

A further advantageous measure consists in, on the outside 32 the wall 3 of the body 2 to provide a flattening 7, the so is arranged and configured that the bore 5 on the outside 32 in a flat surface opens. This has the advantage that the devices 10 (in Fig. 1 and Fig. 2 indicated by dashed lines), with the medium from the Pressure accumulator to be acted upon, for example components of Fuel injection system to be mounted directly on the base body 2 can, so that can be dispensed with connecting lines.

Of course it is also possible - as in the context of the second Embodiment shown in Fig. 5 - that the flattening 7 via the entire length of the body extends so that the flattening 7 forming a flat strip that extends substantially over the entire Length of the main body 2 extends. The holes 5 then open in this flat strip.

FIG. 3 shows, in a representation analogous to FIG. 1, a variant of the first embodiment Example. In this variant, the external shape of the Main body 2 is not cylindrical, but has two flat strips 8, extending substantially over the entire length of the tubular Base body 2 extend. The flat strips 8 are arranged so that the holes 5 outside these flat strips 8 in the outside 32nd open out.

On this strip 8 additional equipment 9 can be arranged. at Large diesel engines are typically used as heavy fuel oil. The heavy oil must be heated to obtain the necessary viscosity. This can be on one of the flat strips 8 a heating than Additional device 9 may be provided to the heavy oil in the Storage space 4 to supply heat.

FIG. 4 shows, in a representation analogous to FIG. 1, a cross section through FIG a second example of a pressure accumulator 1. The following is only on the differences to the first Example received. The explanations related to In the first example, the same applies analogously for the second example. In particular, the reference numerals the same meaning.

In the example shown in FIG. 4, several are here namely three, the bulges 6 on the inside 31 the wall 3 is provided. Each of the bulges 6 extends over one essential part of the length of the storage space 4, preferably over its whole length. The vaults 6 are uniform over the circumference of Inside 31 distributed. There are several holes 5 are provided, each in the center of one of the vaults 6 open into the storage space 4. At the outer side 32 flats 7 are provided, which are arranged so that the holes 5 on the outside 32 in a flat surface open out. Of course it is also possible, the vaults unevenly to distribute over the circumference.

In this example, the holes 5 for the removal of Medium from the storage space 4 over the circumference of the pressure vessel. 1 distributed. As a result, more holes 5 can be provided. Furthermore, can the medium without great effort in different directions be carried away.

In the variant in Fig. 5, the flattenings 7 extend over the entire length of the main body 2, so that the flats 7 respectively form a flat strip 8, which extends substantially over the entire length of the main body 2 extends. The holes 5 open then each in one of these flat strips 8 a.

FIG. 6 shows a variant in which the outer surface 32 of the wall 3 forms a cylinder jacket.

For the connection of the pressure accumulator 1 with those devices or Facilities to be supplied with the medium are very many Variants possible. For example, the device 10 (FIG. 1, FIG explained above, directly attached to the outside 32 of the wall 3 become. It is also possible, the bore 5 with an internal thread provided, in which a pressure line or a connection part screwed becomes. Furthermore, it is also possible a flange preferably on one of Flattening 7 or one of the flat strips 8 to attach. in principle own all known connection and Mounting options.

The following is based on an embodiment of the invention another particularly preferred in practical terms Implementation form for the inventive in the storage space. 4 Sufficient curvature 6 described. It is understood that the Explanations regarding the first and the second example in apply mutatis mutandis the same way for the embodiment and the individual measures described also with the Embodiment can be combined or applicable to it.

Fig. 7 shows a cross section through the embodiment. Of the Difference to the first and the second example consists in the configuration of the memory space 4. The memory space 4 is at this embodiment of two cylindrical longitudinal bores 41, 42, which extend parallel to each other in the direction of the axis L. The axes L1, L2 of the longitudinal bores 41, 42 have a distance E from one another, which is dimensioned such that the cross sections of the longitudinal bores Overlap 41.42. This results in the illustrated in Fig. 7 inner profile, the essentially has the shape of an eight. The constrictions of these eight thus form two inventive curved bulges 6, which in the Interior of the storage space 4 extend. In the representation according to upper vault 6 opens the hole 5. Of course it is also possible that additionally or alternatively, a bore in the Darstellungsgemäss lower vault 6 opens.

As the height H of the camber in this embodiment, the difference from the diameter of the longitudinal bore 41 and 42 and the length of the common secant of the two circular cross sections of the Longitudinal holes 41 and 42 understood.

The respective distance of the axes L1 and L2 from the axis L can For example, about 40 percent of the radius of the associated longitudinal bore 41 and 42, respectively. The distance between the longitudinal holes 41,42 from the center (Axis L) is defined by the diameter of the radial bore 5 and the permissible fatigue limit determined. At the shown here Embodiment are the two longitudinal holes 41 and 42nd symmetrical with respect to the axis L. But this is not necessary.

Preferably, the longitudinal bores have the same radius. It can but also different radii are used.

Although preferred, it is not necessary that the two Longitudinal holes 41, 42 run parallel, they can also be slightly inclined to each other.

The embodiment is characterized in particular by his simple production. It only needs two holes around the Storage space 4 with the inventive bulges 6 produce.

Fig. 8 shows in cross section a variant of the embodiment. In this variant, the storage space 4 consists of three longitudinal bores 41,42,43, which are arranged such that their cross sections overlap. As FIG. 8 shows, this results in three bulges 6 according to the invention generated, each protrude into the storage space 4. In each of these Vaulting opens a radial hole 5. Of course it is also possible that only in one or two of the vaults 6 radial bores 5 open.

Preferably, the longitudinal bores 41, 42, 43 are symmetrical with respect to Axis L arranged.

Of course, also embodiments with more than three Longitudinal holes 41,42,43 possible.

It is understood that the features of the described embodiments and variants also described in a different way than here explicitly can be combined with each other. Also are configurations with two or more than three of the vaults 6 possible. In case of several vaults 6 it is not necessary that all vaults are made equal, they can for example, have different curvatures.

Even if in the context of this application on the practice very much relevant application of large diesel engines reference was, it is understood that the inventive pressure accumulator in analogously the same way for other diesel engines, for example Small diesel engines and internal combustion engines are generally used can be.

Claims (10)

1. A pressure accumulator for a common rail system of an internal combustion engine having a pipe-like base body (2) with a wall (3) which bounds a storage space (4) provided in the interior of the base body (2) for the medium to be stored, as well as having at least one bore (5) which extends through the wall (3) for the discharge of the medium, wherein at least one curved arch (6) is provided at the inner side (31) of the wall (3), extends into the storage space (4) and is arranged such that the bore (5) opens into the storage space (4) within the curved arch (6), characterised in that the storage space (4) includes at least two preferably cylindrical longitudinal bores (41, 42, 43) which are arranged such that their cross-sections overlap.
2. A pressure accumulator in accordance with claim 1, in which the arch (6) extends over a substantial part of the length of the storage space (4), preferably over the whole length of the storage space (4).
3. A pressure accumulator in accordance with any one of the preceding claims, in which at least two curved arches (6) extending into the storage space (4) are provided at the inner side (31) of the wall (3) and extend in each case over a substantial part of the length of the storage space (4), preferably over the whole length of the storage space (4), and are provided at different positions with respect to the peripheral direction of the inner side (31) of the wall (3).
4. A pressure accumulator in accordance with any one of the preceding claims, in which the bore (5), or the bores (5), extends/extend in the radial direction.
5. A pressure accumulator in accordance with any one of the preceding claims, in which each bore (5) opens into the storage space (4) at the centre of the arch (6) with respect to the peripheral direction of the inner side of the wall.
6. A pressure accumulator in accordance with any one of the preceding claims, in which each arch (6) has a height (H) in the radial direction which amounts to between 5% and 30% of the inner diameter (D) of the storage space (4).
7. A pressure accumulator in accordance with any one of the preceding claims, in which the wall (3) of the base body (2) has at least one flat (7) at its outer side which is arranged and designed such that the bore (5) opens into a planar face at the outer side (32) of the wall (3).
8. A pressure accumulator in accordance with any one of the preceding claims, in which the wall (3) of the base body (2) has at least one planar strip (8) at its outside (31) which extends substantially over the whole length of the pipe-like base body (2).
9. A pressure accumulator in accordance with claim 8, in which the bores (5) open into the planar strip (7; 8).
10. A large diesel engine having a common rail system for the fuel injection which has a pressure accumulator (1) in accordance with any one of the preceding claims.

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